View allAll Photos Tagged self-limiting
This image is about being aware of self limiting behavioral patterns and being stuck in those modes .
This is the first time I've ever seen this condition in our deer population on the Olympic Peninsula. Not pretty but interesting just the same. We don't always see beauty out in the field.
I found the following info on Fish and Wildlife's Website.
WILDLIFE DIVISION
Regulating harvest, health, and enhancement of wildlife populations
Wildlife and Fish Health - Fibromatosis in Deer
Questions and Answers about Fibromatosis
What is fibromatosis?
Fibromatosis is a common skin disease of white-tailed deer, mule deer, black-tailed deer, and other Cervidae in North America. There is evidence that the skin tumors, called fibromas, are caused by a papilloma virus.
What are the signs of fibromatosis in deer?
Large, warty growths, or fibromas appear as firm, round, nodular, hairless, pigmented skin abnormalities adhered to or incorporated within the skin of deer. The masses occur most frequently around the eyes, mouth, face, neck, and forelimbs, and may appear as a single mass or numerous growths. The tumors are typically small (less than 5 inches across), dark brown or black in color, and their surface may be abraded or bleeding and in some case infected. Most often, fibromas occur in deer less than 2 years of age, with a higher incidence of disease in bucks.
How is the disease transmitted?
The manner in which the disease is transmitted is not entirely known. However, it has been suggested that transmission occurs through direct contact between broken skin and infectious material, either from a fibroma of an another infected deer or vegetation that has come in contact with an infected deer. Since more bucks are seen with the condition, rutting or fighting among males during the rut or rubbing of antlers to shed velvet may play a role in disease spread. Biting insects may also be involved in disease transmission.
What is the significance of fibromas to deer?
Deer with fibromatosis are generally unaffected by the condition, unless the location or size of the tumor impedes normal movement, feeding, or vision. The tumors may be surgically removed, although treatment is not typically practical, and is usually unnecessary, as the disease is self-limiting and fibromas tend to regress over time.
Do deer that get the disease die?
Typically, deer are exposed to the virus at a young age and develop fibromas. If they are exposed again as an adult, they are less likely to get the disease a second time due to acquired immunity to the disease. Fibromas are not a significant cause of deer deaths.
Can humans become infected with deer fibromas?
No, the virus is species specific and deer fibromas are not known to occur in or affect humans. As fibromas only involve the skin and not underlying muscles or other structures, an infected animal’s meat is safe to eat. However, if you have any question regarding the health of the animal or meat safety contact your local ODFW field office or wildlife health hotline
Cigar Galaxy (M82) – The Cigar Galaxy is a site of intense starburst activity, believed to be triggered by its interaction with the nearby Messier 81 (Bode’s Galaxy). In M82, young stars are crammed into tiny but massive star clusters. These, in turn, congregate by the dozens to make the bright patches, or “starburst clumps,” in the central parts of M82. The clusters in the clumps can only be distinguished in sharp Hubble images. The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst then will subside, probably in a few tens of millions of years. Located 12 million light-years away, M82 appears high in the northern spring sky in the direction of the constellation Ursa Major, the Great Bear. It is called the “Cigar Galaxy” because of the elliptical shape produced by the oblique tilt of its starry disk relative to our line of sight.
Description from www.constellation-guide.com
Taken from Death Valley CA, January 2025
Equipment Paramount MYT, ZWO 2600MM, Vixen VC200L @ 1800mm focal length. Scope courtesy of Larry Parker
This image is an HORGB composition. H and O are surprisingly strong. This object also has a strong S2 component, but it overlaps with Ha too much to display as a separate color channel. Stars are RGB only.
RGB 3 hours each channel
HO 6 hours each channel
I'm finding less and less separation these days between the parts of my brain that handle image capture and the ones devoted to image processing. These brain parts were once very distinct and didn't mix well. But I've come to conclude that thinking is inherently self limiting. The creativity need not end the moment the shutter is pressed. Sometimes the image is 85 or 90 percent there in that 125th of a second the shutter might be open. Other times the percentage is way less. Quite often I come home with parts of good image spread across several hundred frames. I'll scroll through and think, wow, I love that part of this photo, but not that. More often I'll discover things I didn't notice at the time and decide to play them up in processing. Or sometimes I'll just feel completely different about an image than I did when the scene was unfolding before me. Such was the case here, a brilliant autumn day, resplendent with richly saturated color. That really all I could see at the time. It's funny how sometimes color totally props up a marginal photo; other times it actually interferes. This one fell into the latter column. I was taken with the tonal values and the illumination effect of autumn leaves reflecting bright sunlight. Gives a sort of infrared quality that I love. It's ethereal, otherworldly, and ties in wonderfully with a feeling that often have in old cemeteries. The sky tones and textured effect of the clouds ties it all together in a way that was lost in full color. People sometimes see me out with the camera on a day like this and ask if I'm getting any 'pretty' pictures. Always makes me smile. The answer is always yes, but the prettiness is definitely in the eye of the beholder.
A decade ago, I led several photo workshops at this location, and most of my students loved it. One, however, was obviously struggling, and when I tried to assist she snarled, "This place doesn't do a thing for me - just as I expected!" Wow. What a self-limiting attitude! When I'm in the field, I expect wonders, and usually wonders are delivered. How we approach any situation tends to heavily influence our experience. An open mind is best.
Not surprisingly, this particular student always wanted to know "the rule" for photographing anything, and appeared to become frustrated at my insistence that I don't follow rules. Rules are for physics, not art. Certain established visual principles come into play, and I'm more than willing to discuss them, but I never use them as a starting point. My photos always originate from a gut feeling, which I then fine tune through the viewfinder. Often the elements will end up organized according to - for example - the principle of thirds. This photo is a good illustration: one third sky, two thirds land. But I wasn't thinking of that when I made the shot. I arranged the visual elements because somehow they felt "right".
I don't know if gut feelings can be taught, so it's understandable if instructors resort to teaching via "rules", and if students expect to be taught the "rules". The vast majority of my students over the years were willing to participate in the exercises I had devised to help them break out of the box of rules they were (perhaps) stuck in. I guess my methods weren't suited to everyone!
Anyway, this amazing place, lying less than an hour's drive southwest of Medicine Hat, Alberta, is well worth visiting. Huge concretions, 2 metres (6 feet) or more in diameter, are strewn across the prairie like gigantic bowling balls. Some are broken, some intact. The softer bedrock material has eroded away, leaving these amazing forms. It's a place where the imagination can wander! Better in evening light; in morning, steep-sided coulee slopes block the early, warm rays.
Scanned from the original Fujichrome Velvia (ISO 50) slide; photographed at Red Rock Coulee Natural Area, Alberta (Canada). Don't use this image on websites, blogs, or other media without explicit permission © 1999 James R. Page - all rights reserved.
“We like to say that Archean Earth is the most alien planet we have geochemical data for,”
For astronomers trying to understand which distant planets might have habitable conditions, the role of atmospheric haze has been hazy. To help sort it out, a team of researchers has been looking to Earth – specifically Earth during the Archean era, an epic 1-1/2-billion-year period early in our planet’s history. Read more: go.nasa.gov/2kTBhPU
Caption: When haze built up in the atmosphere of Archean Earth, the young planet might have looked like this artist's interpretation - a pale orange dot. A team led by Goddard scientists thinks the haze was self-limiting, cooling the surface by about 36 degrees Fahrenheit (20 Kelvins) – not enough to cause runaway glaciation. The team’s modeling suggests that atmospheric haze might be helpful for identifying earthlike exoplanets that could be habitable. Credits: NASA’s Goddard Space Flight Center/Francis Reddy
en.wikipedia.org/wiki/European_hare
The European hare (Lepus europaeus), also known as the brown hare, is a species of hare native to Europe and parts of Asia. It is among the largest hare species and is adapted to temperate, open country. Hares are herbivorous and feed mainly on grasses and herbs, supplementing these with twigs, buds, bark and field crops, particularly in winter. Their natural predators include large birds of prey, canids and felids. They rely on high-speed endurance running to escape from their enemies; having long, powerful limbs and large nostrils.
Generally nocturnal and shy in nature, hares change their behaviour in the spring, when they can be seen in broad daylight chasing one another around in fields. During this spring frenzy, they sometimes strike one another with their paws ("boxing"). This is usually not competition between males, but a female hitting a male, either to show she is not yet ready to mate or as a test of his determination. The female nests in a depression on the surface of the ground rather than in a burrow, and the young are active as soon as they are born. Litters may consist of three or four young and a female can bear three litters a year, with hares living for up to twelve years. The breeding season lasts from January to August.
The European hare is listed as being of least concern by the International Union for Conservation of Nature because it has a wide range and is moderately abundant. However, populations have been declining in mainland Europe since the 1960s, at least partly due to changes in farming practices. The hare has been hunted across Europe for centuries, with more than five million being shot each year; in Britain, it has traditionally been hunted by beagling and hare coursing, but these field sports are now illegal. The hare has been a traditional symbol of fertility and reproduction in some cultures, and its courtship behaviour in the spring inspired the English idiom mad as a March hare.
Taxonomy and genetics
The European hare was first described in 1778 by German zoologist Peter Simon Pallas.[2] It shares the genus Lepus (Latin for "hare"[3]) with 31 other hare and jackrabbit species,[4] jackrabbits being the name given to some species of hare native to North America. They are distinguished from other leporids (hares and rabbits) by their longer legs, wider nostrils and active (precocial) young.[5] The Corsican hare, broom hare and Granada hare were at one time considered to be subspecies of the European hare, but DNA sequencing and morphological analysis support their status as separate species.[6][7]
There is some debate as to whether the European hare and the Cape hare are the same species. A 2005 nuclear gene pool study suggested that they are,[8] but a 2006 study of the mitochondrial DNA of these same animals concluded that they had diverged sufficiently widely to be considered separate species.[9] A 2008 study claims that in the case of Lepus species, with their rapid evolution, species designation cannot be based solely on mtDNA but should also include an examination of the nuclear gene pool. It is possible that the genetic differences between the European and Cape hare are due to geographic separation rather than actual divergence. It has been speculated that in the Near East, hare populations are intergrading and experiencing gene flow.[10] Another 2008 study suggests that more research is needed before a conclusion is reached as to whether a species complex exists;[11] the European hare remains classified as a single species until further data contradicts this assumption.[1]
Cladogenetic analysis suggests that European hares survived the last glacial period during the Pleistocene via refugia in southern Europe (Italian peninsula and Balkans) and Asia Minor. Subsequent colonisations of Central Europe appear to have been initiated by human-caused environmental changes.[12] Genetic diversity in current populations is high with no signs of inbreeding. Gene flow appears to be biased towards males, but overall populations are matrilineally structured. There appears to be a particularly large degree of genetic diversity in hares in the North Rhine-Westphalia region of Germany. It is however possible that restricted gene flow could reduce genetic diversity within populations that become isolated.[13]
Historically, up to 30 subspecies of European hare have been described, although their status has been disputed.[5] These subspecies have been distinguished by differences in pelage colouration, body size, external body measurements, skull morphology and tooth shape.[14] Sixteen subspecies are listed in the IUCN red book, following Hoffmann and Smith (2005): Lepus europaeus caspicus, L. e. connori, L. e. creticus, L. e. cyprius, L. e. cyrensis, L. e. europaeus, L. e. hybridus, L. e. judeae, L. e. karpathorum, L. e. medius, L. e. occidentalis, L. e. parnassius, L. e. ponticus, L. e. rhodius, L. e. syriacus, and L. e. transsylvanicus.[15] Twenty-nine subspecies are listed by Chapman and Flux in their book on lagomorphs, including in addition L. e. alba, L. e. argenteogrisea, L. e. biarmicus, L. e. borealis, L. e. caspicus, L. e. caucasicus, L. e. flavus, L. e. gallaecius, L. e. hispanicus, L. e. hyemalis, L. e. granatensis, L. e. iturissius, L. e. kalmykorum, L. e. meridiei, L. e. meridionalis, L. e. niethammeri, L. e. niger, L. e. tesquorum, and L. e. tumak, but excluding L. e. connori, L. e. creticus, L. e. cyprius, L. e. judeae, L. e. rhodius, and L. e. syriacus, with the proviso that the subspecies they list are of "very variable status".[5]
Description
The European hare, like other members of the family Leporidae, is a fast-running terrestrial mammal; it has eyes set high on the sides of its head, long ears and a flexible neck. Its teeth grow continuously, the first incisors being modified for gnawing while the second incisors are peg-like and non-functional. There is a gap (diastema) between the incisors and the cheek teeth, the latter being adapted for grinding coarse plant material. The dental formula is 2/1, 0/0, 3/2, 3/3.[16][17] The dark limb musculature of hares is adapted for high-speed endurance running in open country. By contrast, cottontail rabbits are built for short bursts of speed in more vegetated habitats.[5][18] Other adaptions for high speed running in hares include wider nostrils and larger hearts.[5] In comparison to the European rabbit, the hare has a proportionally smaller stomach and caecum.[19]
This hare is one of the largest of the lagomorphs. Its head and body length can range from 60 to 75 cm (24 to 30 in) with a tail length of 7.2 to 11 cm (2.8 to 4.3 in). The body mass is typically between 3 and 5 kg (6.6 and 11.0 lb).[20] The hare's elongated ears range from 9.4 to 11.0 cm (3.7 to 4.3 in) from the notch to tip. It also has long hind feet that have a length of between 14 and 16 cm (5.5 and 6.3 in).[21] The skull has nasal bones that are short, but broad and heavy. The supraorbital ridge has well-developed anterior and posterior lobes and the lacrimal bone projects prominently from the anterior wall of the orbit.[20]
The fur colour is grizzled yellow-brown on the back; rufous on the shoulders, legs, neck and throat; white on the underside and black on the tail and ear tips.[21] The fur on the back is typically longer and more curled than on the rest of the body.[5] The European hare's fur does not turn completely white in the winter as is the case with some other members of the genus,[21] although the sides of the head and base of the ears do develop white areas and the hip and rump region may gain some grey.[5]
Range and habitat
European hares are native to much of continental Europe and part of Asia. Their range extends from northern Spain to southern Scandinavia, eastern Europe, and northern parts of Western and Central Asia. They have been extending their range into Siberia.[5] They may have been introduced to Britain by the Romans (circa 2000 years ago) as there are no records of them from earlier sites. Undocumented introductions likely occurred in some Mediterranean Islands.[22] They have also been introduced, mostly as game animals, to North America (in Ontario and New York State, and unsuccessfully in Pennsylvania, Massachusetts, and Connecticut), South America (Brazil, Chile, Argentina, Uruguay, Paraguay, Bolivia, Peru and the Falkland Islands), Australia, both islands of New Zealand and the south Pacific coast of Russia.[5][21][23]
Hares primarily live in open fields with scattered brush for shelter. They are very adaptable and thrive in mixed farmland.[5] According to a study done in the Czech Republic, the mean hare densities were highest at altitudes below 200 metres (660 ft), 40 to 60 days of annual snow cover, 450 to 700 millimetres (18 to 28 in) of annual precipitation, and a mean annual air temperature of around 10 °C (50 °F). With regards to climate, the study found that hare densities were highest in "warm and dry districts with mild winters".[24] In Poland, hares are most abundant in areas with few forest edges, perhaps because foxes can use these for cover. They require cover, such as hedges, ditches and permanent cover areas, because these habitats supply the varied diet they require, and are found at lower densities in large open fields. Intensive cultivation of the land results in greater mortality of young hares (leverets).[25]
In the United Kingdom, hares are seen most frequently on arable farms, especially those with fallow land, wheat and sugar beet crops. In mainly grass farms their numbers are raised when there are improved pastures, some arable crops and patches of woodland. They are seen less frequently where foxes are abundant or where there are many buzzards. They also seem to be fewer in number in areas with high European rabbit populations,[26] although there appears to be little interaction between the two species and no aggression.[27] Although hares are shot as game when they are plentiful, this is a self-limiting activity and is less likely to occur in localities where they are scarce.[26]
Behaviour and life history
Hares are primarily nocturnal and spend a third of their time foraging.[5] During daytime, a hare hides in a depression in the ground called a "form" where it is partially hidden. Hares can run at 70 km/h (43 mph) and when confronted by predators they rely on outrunning them in the open. They are generally thought of as asocial but can be seen in both large and small groups. They do not appear to be territorial, living in shared home ranges of around 300 ha (740 acres). Hares communicate with each other by a variety of visual signals. To show interest they raise their ears, while lowering the ears warns others to keep away. When challenging a conspecific, a hare thumps its front feet; the hind feet are used to warn others of a predator. A hare squeals when hurt or scared and a female makes "guttural" calls to attract her young.[21] Hares can live for as long as twelve years.[1]
Food and foraging
European hares are primarily herbivorous. They may forage for wild grasses and weeds but with the intensification of agriculture, they have taken to feeding on crops when preferred foods are not available.[1] During the spring and summer, they feed on soy, clover and corn poppy[28] as well as grasses and herbs.[21] During autumn and winter, they primarily choose winter wheat, and are also attracted to piles of sugar beet and carrots provided for them by hunters.[28] They also eat twigs, buds and the bark of shrubs and young fruit trees during winter.[21] Cereal crops are usually avoided when other more attractive foods are available, the species appearing to prefer high energy foodstuffs over crude fibre.[29] When eating twigs, hares strip off the bark to access the vascular tissues which store soluble carbohydrates. Compared to the European rabbit, food passes through the gut more rapidly in the hare, although digestion rates are similar.[19] They sometimes eat their own green, faecal pellets to recover undigested proteins and vitamins.[20] Two to three adult hares can eat more food than a single sheep.[21]
European hares forage in groups. Group feeding is beneficial as individuals can spend more time feeding knowing that other hares are being vigilant. Nevertheless, the distribution of food affects these benefits. When food is well-spaced, all hares are able to access it. When food is clumped together, only dominant hares can access it. In small gatherings, dominants are more successful in defending food, but as more individuals join in, they must spend more time driving off others. The larger the group, the less time dominant individuals have in which to eat. Meanwhile, the subordinates can access the food while the dominants are distracted. As such, when in groups, all individuals fare worse when food is clumped as opposed to when it is widely spaced.[30]
Mating and reproduction
European hares have a prolonged breeding season which lasts from January to August.[31][32] Females, or does, can be found pregnant in all breeding months and males, or bucks, are fertile all year round except during October and November. After this hiatus, the size and activity of the males' testes increase, signalling the start of a new reproductive cycle. This continues through December, January and February when the reproductive tract gains back its functionality. Matings start before ovulation occurs and the first pregnancies of the year often result in a single foetus, with pregnancy failures being common. Peak reproductive activity occurs in March and April, when all females may be pregnant, the majority with three or more foetuses.[32]
The mating system of the hare has been described as both polygynous (single males mating with multiple females) and promiscuous.[33] Females have six-weekly reproductive cycles and are receptive for only a few hours at a time, making competition among local bucks intense.[31] At the height of the breeding season, this phenomenon is known as "March madness",[32] when the normally nocturnal bucks are forced to be active in the daytime. In addition to dominant animals subduing subordinates, the female fights off her numerous suitors if she is not ready to mate. Fights can be vicious and can leave numerous scars on the ears.[31] In these encounters, hares stand upright and attack each other with their paws, a practice known as "boxing", and this activity is usually between a female and a male and not between competing males as was previously believed.[21][34] When a doe is ready to mate, she runs across the countryside, starting a chase that tests the stamina of the following males. When only the fittest male remains, the female stops and allows him to copulate.[31] Female fertility continues through May, June and July, but testosterone production decreases in males and sexual behaviour becomes less overt. Litter sizes decrease as the breeding season draws to a close with no pregnancies occurring after August. The testes of males begin to regress and sperm production ends in September.[32]
Does give birth in hollow depressions in the ground. An individual female may have three litters in a year with a 41- to 42-day gestation period. The young have an average weigh of around 130 grams (4.6 oz) at birth.[35] The leverets are fully furred and are precocial, being ready to leave the nest soon after they are born, an adaptation to the lack of physical protection relative to that afforded by a burrow.[21] Leverets disperse during the day and come together in the evening close to where they were born. Their mother visits them for nursing soon after sunset; the young suckle for around five minutes, urinating while they do so, with the doe licking up the fluid. She then leaps away so as not to leave an olfactory trail, and the leverets disperse once more.[21][36] Young can eat solid food after two weeks and are weaned when they are four weeks old.[21] While young of either sex commonly explore their surroundings,[37] natal dispersal tends to be greater in males.[33][38] Sexual maturity occurs at seven or eight months for females and six months for males.[1]
Mortality and health
European hares are large leporids and adults can only be tackled by large predators such as canids, felids and the largest birds of prey.[20] In Poland it was found that the consumption of hares by foxes was at its highest during spring, when the availability of small animal prey was low; at this time of year, hares may constitute up to 50% of the biomass eaten by foxes, with 50% of the mortality of adult hares being caused by their predation.[39] In Scandinavia, a natural epizootic of sarcoptic mange which reduced the population of red foxes dramatically, resulted in an increase in the number of European hares, which returned to previous levels when the numbers of foxes subsequently increased.[40] The golden eagle preys on the European hare in the Alps, the Carpathians, the Apennines and northern Spain.[41] In North America, foxes and coyotes are probably the most common predators, with bobcats and lynx also preying on them in more remote locations.[35]
European hares have both external and internal parasites. One study found that 54% of animals in Slovakia were parasitised by nematodes and over 90% by coccidia.[42] In Australia, European hares were reported as being infected by four species of nematode, six of coccidian, several liver flukes and two canine tapeworms. They were also found to host rabbit fleas (Spilopsyllus cuniculi), stickfast fleas (Echidnophaga myrmecobii), lice (Haemodipsus setoni and H. lyriocephalus), and mites (Leporacarus gibbus).[43]
European brown hare syndrome (EBHS) is a disease caused by a calicivirus similar to that causing rabbit haemorrhagic disease (RHS) and can similarly be fatal, but cross infection between the two mammal species does not occur.[44] Other threats to the hare are pasteurellosis, yersiniosis (pseudo-tuberculosis), coccidiosis and tularaemia, which are the principal sources of mortality.[45]
Relationship with humans
In folklore, literature, and art
In Europe, the hare has been a symbol of sex and fertility since at least Ancient Greece. The Greeks associated it with the gods Dionysus, Aphrodite and Artemis as well as with satyrs and cupids. The Christian Church connected the hare with lustfulness and homosexuality, but also associated it with the persecution of the church because of the way it was commonly hunted.[46]
In Northern Europe, Easter imagery often involves hares or rabbits. Citing folk Easter customs in Leicestershire, England, where "the profits of the land called Harecrop Leys were applied to providing a meal which was thrown on the ground at the 'Hare-pie Bank'", the 19th-century scholar Charles Isaac Elton proposed a possible connection between these customs and the worship of Ēostre.[47] In his 19th-century study of the hare in folk custom and mythology, Charles J. Billson cites folk customs involving the hare around Easter in Northern Europe, and argues that the hare was probably a sacred animal in prehistoric Britain's festival of springtime.[48] Observation of the hare's springtime mating behaviour led to the popular English idiom "mad as a March hare",[46] with similar phrases from the sixteenth century writings of John Skelton and Sir Thomas More onwards.[49] The mad hare reappears in Alice's Adventures in Wonderland by Lewis Carroll, in which Alice participates in a crazy tea party with the March Hare and the Mad Hatter.[50]
Any connection of the hare to Ēostre is doubtful. John Andrew Boyle cites an etymology dictionary by A. Ernout and A. Meillet, who wrote that the lights of Ēostre were carried by hares, that Ēostre represented spring fecundity, love and sexual pleasure. Boyle responds that almost nothing is known about Ēostre, and that the authors had seemingly accepted the identification of Ēostre with the Norse goddess Freyja, but that the hare is not associated with Freyja either. Boyle adds that "when the authors speak of the hare as the 'companion of Aphrodite and of satyrs and cupids' and 'in the Middle Ages [the hare] appears beside the figure of [mythological] Luxuria', they are on much surer ground."[51]
The hare is a character in some fables, such as The Tortoise and the Hare of Aesop.[52] The story was annexed to a philosophical problem by Zeno of Elea, who created a set of paradoxes to support Parmenides' attack on the idea of continuous motion, as each time the hare (or the hero Achilles) moves to where the tortoise was, the tortoise moves just a little further away.[53][54] The German Renaissance artist Albrecht Dürer realistically depicted a hare in his 1502 watercolour painting Young Hare.[55]
Food and hunting
Across Europe, over five million European hares are shot each year, making it probably the most important game mammal on the continent. This popularity has threatened regional varieties such as those of France and Denmark, through large-scale importing of hares from Eastern European countries such as Hungary.[5] Hares have traditionally been hunted in Britain by beagling and hare coursing. In beagling, the hare is hunted with a pack of small hunting dogs, beagles, followed by the human hunters on foot. In Britain, the 2004 Hunting Act banned hunting of hares with dogs, so the 60 beagle packs now use artificial "trails", or may legally continue to hunt rabbits.[56] Hare coursing with greyhounds was once an aristocratic pursuit, forbidden to lower social classes.[57] More recently, informal hare coursing became a lower class activity and was conducted without the landowner's permission;[58] it is also now illegal.[59]
Hare is traditionally cooked by jugging: a whole hare is cut into pieces, marinated and cooked slowly with red wine and juniper berries in a tall jug that stands in a pan of water. It is traditionally served with (or briefly cooked with) the hare's blood and port wine.[60][61] Hare can also be cooked in a casserole.[62] The meat is darker and more strongly flavoured than that of rabbits. Young hares can be roasted; the meat of older hares becomes too tough for roasting, and may be slow-cooked.[61][63]
Status
The European hare has a wide range across Europe and western Asia and has been introduced to a number of other countries around the globe, often as a game species. In general it is considered moderately abundant in its native range,[13] but declines in populations have been noted in many areas since the 1960s. These have been associated with the intensification of agricultural practices.[64] The hare is an adaptable species and can move into new habitats, but it thrives best when there is an availability of a wide variety of weeds and other herbs to supplement its main diet of grasses.[1] The hare is considered a pest in some areas; it is more likely to damage crops and young trees in winter when there are not enough alternative foodstuffs available.[21]
The International Union for Conservation of Nature has evaluated the European hare's conservation status as being of least concern. However, at low population densities, hares are vulnerable to local extinctions as the available gene pool declines, making inbreeding more likely. This is the case in northern Spain and in Greece, where the restocking by hares brought from outside the region has been identified as a threat to regional gene pools. To counteract this, a captive breeding program has been implemented in Spain, and the relocation of some individuals from one location to another has increased genetic variety.[1] The Bern Convention lists the hare under Appendix III as a protected species.[26] Several countries, including Norway, Germany, Austria and Switzerland,[1] have placed the species on their Red Lists as "near threatened" or "threatened".
Chobe National Park, Botswana.
A giraffe showing the affects of the Papilloma Virus. The virus which is transmitted in different ways according to species, will cause a wart on the skin of the animal. It appears to be irritating and the giraffe will often rub the affected area causing the warts to rupture and later get infected. It can be self limiting or progressive due to the individuals immune system. The warts eventually harden and turn in to a type of cancer called a Sarcoid.
It is believed that transmission from Giraffe to Giraffe is by the constant grooming of the Oxpecker bird jumping from animal to animal with the virus on its beak.
Although not a disease that affects the animal in a severe manner, it is mostly unsightly, and can get infected, causing other health problems..
When I processed this image two nights ago, I was suffering from insomnia. It was 2am local time. When I can’t sleep, I don’t read or watch television, I work on my photography (which, in retrospect, has the opposite effect of what I desire -- sleep, hahaa). Photography keeps me interested and enthused so it’s actually harder to go back to sleep once I get into the art of it, which is everyday to some degree.
This image is from my visit to Britain two summers ago, during a road trip between London and beautiful, enchanting Bath (one of the prettiest cities I have ever seen in my life). I never shared any images from Stonehenge because, like those light trails leading towards (or away from) Big Ben and Parliament in London, it’s been photographed thousands, if not millions, of times. As a result, I often avoid adding to the mêlée of images that already exists. However, two nights ago, I couldn’t sleep. . .so I dismissed my own self-limiting regulations and decided to add my perspective to the pool.
I thank those of you have have advised to still share what I have photographed, regardless if the subject has been captured from the same angle, or similar angle, dozens of times. I realize my reservation to share images of a well known scene often limits my own creativity, which actually defeats the entire purpose of why I engage in photography at all. Life is about learning, right? I am fortunate photography gives me that capacity to open my mind and broaden my vision every day (with some assistance and reminders from my friends).
Alas, here is my take on Stonehenge.
WATCH ***TIA: YEAR IN PHOTOS 2012***
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More growth forms. Decided to focus on exploring the range of self-limiting forms in the system for a new work, Limits to Growth.
M82 or the Cigar galaxy, shines brightly at infrared wavelengths and is remarkable for its star formation activity. The Cigar galaxy experiences gravitational interactions with its galactic neighbor, M81, causing it to have an extraordinarily high rate of star formation — a starburst.
Around the galaxy’s center, young stars are being born 10 times faster than they are inside our entire Milky Way galaxy. Radiation and energetic particles from these newborn stars carve into the surrounding gas, and the resulting galactic wind compresses enough gas to make millions of more stars. The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst will then subside, probably in a few tens of millions of years.
This stunning Hubble image of M82 was assembled using observations at different wavelengths. The red in the image represents hydrogen and infrared light, indicating starburst activity. The blue and greenish-yellow color represent visible wavelengths of light.
For more information about Hubble’s observations of M82, see:
hubblesite.org/contents/news-releases/2006/news-2006-14.html
www.spacetelescope.org/images/potw1201a/
hubblesite.org/contents/news-releases/2017/news-2017-42.html
hubblesite.org/contents/news-releases/2008/news-2008-02.html
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: J. Gallagher (University of Wisconsin), M. Mountain (STScI), and P. Puxley (National Science Foundation)
Are you searching for more serenity and tranquility in your life? Do you need to heal from a deep hurt or find more strength and confidence?
There are times when circumstances beyond our control will leave us feeling tremendously sad and spiritually depleted. Yet, we can slowly begin to change our focus. In doing so, time will begin to work its magic; it will begin to fill the emptiness brought by life's unfairness, heartache, and pain.
A spirit of serenity and tranquility resides within each of us. It is a quiet energy of confidence, power and strength where creative thoughts arise.
From this peaceful place, we can begin to focus on what we need to do. We are not consumed by self-limiting beliefs and worries that steal our energy. Instead we can access our boundless God-given capacity.
Living serenely doesn't mean that we deny problems or avoid the responsibility for solving them. Just the opposite - we find the clarity and presence of mind to deal with the issues of daily living in positive constructive ways. Instead of identifying with problems and painful situations, we approach them from a calm center where constructive ideas originate.
Ask yourself: What thoughts tend to block my awareness of serenity and tranquility?
If you could choose, what would you want God to say to you in your most serene and tranquil moments?
Spend a moment in silence today. Look beneath and between the thoughts that occupy your mind. Notice the peaceful energy of aliveness within you.
Share this spirit of serenity with others through kindness and constructive action. By sharing peace with others, you will become more and more aware of the serenity and tranquility within you.
Taken : Mangla Dam
Discovered by the German astronomer Johann Elert Bode in 1774, M81 is one of the brightest galaxies in the night sky. It is located 11.6 million light-years from Earth in the constellation Ursa Major and has an apparent magnitude of 6.9. Through a pair of binoculars, the galaxy appears as a faint patch of light in the same field of view as M82. A small telescope will resolve M81’s core. The galaxy is best observed during April.
The galaxy’s spiral arms, which wind all the way down into its nucleus, are made up of young, bluish, hot stars formed in the past few million years. They also host a population of stars formed in an episode of star formation that started about 600 million years ago. Ultraviolet light from hot, young stars is fluorescing the surrounding clouds of hydrogen gas. A number of sinuous dust lanes also wind all the way into the nucleus of M81.
The galaxy’s central bulge contains much older, redder stars. It is significantly larger than the Milky Way’s bulge. A black hole of 70 million solar masses resides at the center of M81 and is about 15 times the mass of the Milky Way’s central black hole.
M82 or the Cigar galaxy, shines brightly at infrared wavelengths and is remarkable for its star formation activity. The Cigar galaxy experiences gravitational interactions with its galactic neighbor, M81, causing it to have an extraordinarily high rate of star formation — a starburst.
Around the galaxy’s center, young stars are being born 10 times faster than they are inside our entire Milky Way galaxy. Radiation and energetic particles from these newborn stars carve into the surrounding gas, and the resulting galactic wind compresses enough gas to make millions of more stars. The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst will then subside, probably in a few tens of millions of years.
M82 was discovered, along with its neighbor M81, by the German astronomer Johann Elert Bode in 1774. Located 12 million light-years from Earth in the constellation Ursa Major, M82 has an apparent magnitude of 8.4 and is best observed in April.
540 x10 seconds, total integration time of 90 minutes.
"Dr. Martha Starks (Modes of Therapeutic Action) defines maturity as "being able to accept the reality of people and things as they are, without needing them to be other than that." Humans tend to upset themselves if life is not the way they think it should be. What is - is… make your plan and move on to productive behaviors.
Our brains will believe anything we tell them. If you tell your brain that you are in danger (physically, emotionally or psychologically) it reacts as if you are sliding face first down a mountain. If you replace negative irrational, self-limiting thoughts, your emotional control will improve dramatically. What does that mean? It means that your relationships improve, you feel in control and self-confident, you like yourself, and you are more likely to reach your life goals."
Dr. Dorothy McCoy, www.personalityone.com/emotional-maturity.html
Rockets: Nuclear powered pulse rockets capable of rotating forward, backwards, and out to the sides.
Gyroscopes: Mounted on the sides and bottom of the Dragonfly, these can either be used to stabilize the fighter (for example, to counteract the force of the rocket's rotating) or to quickly spin the fighter to face a target.
Autocannon: The Dragonfly is equipped with a twin-linked pair of 20mm recoilless autocannons fed from helical magazines mounted below. ("Helix Magazine" redirects to here.)
Ordinance Chute: It's a chute, along with an ignition system and magnetic clamps to operate the mass torpedo.
Mass Torpedo: A rod of high density metal with a simple rocket system. The Mass torpedo is scored to break up on impact to impart as much force upon its target as possible- a concept similar to hollow-point bullets. The mass torpedo is also resistant to point defense, as a hit will usually break it into a number of high velocity projectiles rather than deflecting away.
Hangar Crane Hardpoint: The Dragonfly has a major hardpoint on the rear as well as a number of docking lugs along its undercarriage to allow it to be housed in a zero-g hangar. It could also be equipped with landing gear if appropriate for its mission.
Retrieval Hook: For catching a brake tether when docking.
Compression Harness: A pneumatic system that interlinks with the pilot's space suit, the harness is designed to reduce the physical strain of high-g maneuvers on the pilot. The air system can feed directly into the space suit to provide emergency atmosphere.
Reactor: A muon catalyzed fission reactor that is pre-charged before launch. The low start temperature and self limiting nature of the muon reaction proved to be ideal for small craft that could rely on a larger power source to provide catalyzing agents between missions.
Cockpit Canopy: The door in and out, of course, it also uses windows made of lab-grown sheets of aluminum crystals. The view ports are very small, and largely intended to be used in certain emergency scenarios, as the pilot's helmet has an internal monitor that provides the necessary visual inputs (as well as anti-nausea display lag during fast maneuvers). Similarly there is a redundant computer display in the front dashboard.
Source: hubblesite.org/newscenter/archive/releases/2006/14/image/a
Retouching: Lightroom 2.1
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The galaxy M82 is remarkable for its bright blue disk, webs of shredded clouds, and fiery-looking plumes of glowing hydrogen blasting out of its central regions.
Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy. The resulting huge concentration of young stars carved into the gas and dust at the galaxy's center. The fierce galactic superwind generated from these stars compresses enough gas to make millions of more stars.
In M82, young stars are crammed into tiny but massive star clusters. These, in turn, congregate by the dozens to make the bright patches, or "starburst clumps," in the central parts of M82. The clusters in the clumps can only be distinguished in the sharp Hubble images. Most of the pale, white objects sprinkled around the body of M82 that look like fuzzy stars are actually individual star clusters about 20 light-years across and contain up to a million stars.
The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst then will subside, probably in a few tens of millions of years.
Located 12 million light-years away, M82 appears high in the northern spring sky in the direction of the constellation Ursa Major, the Great Bear. It is also called the "Cigar Galaxy" because of the elliptical shape produced by the oblique tilt of its starry disk relative to our line of sight.
The observation was made in March 2006, with the Advanced Camera for Surveys' Wide Field Channel. Astronomers assembled this six-image composite mosaic by combining exposures taken with four colored filters that capture starlight from visible and infrared wavelengths as well as the light from the glowing hydrogen filaments.
I spent the last few days preparing for my Advanced Cardiac Life Support recertification today. Pictured above is a potentially lethal rhythm, perhaps the most lethal of all heart rhythms. Torsades de pointes is a distinctive form of polymorphic ventricular tachycardia with a gradual change in the amplitude and twisting of the QRS complexes around the isoelectric line. The management of Torsades is quite different from that of garden-variety V tach. In particular, the use of group IA antidysrhythmic drugs, which tend to prolong the QT interval, can have disastrous consequences in Torsades. Rapid and accurate diagnosis, therefore, is critical.
The characteristics of Torsades are:
Rotation of the heart's electrical axis by at least 180º
Prolonged QT interval (LQTS)
Preceded by long and short RR-intervals
Triggered by an early premature ventricular contraction (R-on-T PVC)
Torsades can be caused by diarrhea, hypomagnesemia and hypokalemia. It is usually seen in the malnourished and alcoholic patient. In an otherwise stable patient, cardioversion is a last resort. Torsades tends to be paroxysmal in nature, and often occurs following cardioversion. Although Torsades frequently is self limiting, it may refract into ventricular fibrillation, requiring defibrillation.
To treat, remove causative factors. Predisposing conditions such as hypokalemia, hypomagnesemia, and bradycardia should be identified and corrected. Magnesium is the drug of choice for terminating Torsades. Magnesium can be given at 1-2 g IV initially in 30-60 seconds, which then can be repeated in 5 to 15 minutes. Alternatively, a continuous infusion can be started at a rate of 3-10 mg/min. Magnesium is effective even in patients with normal magnesium levels. Because of the danger of hypermagnesemia, the patient requires close monitoring.
Oh, how did I do on my recertification? I passed. I get to keep doing my job.
Strobist: AB800 with Softlighter II camera right. AB800 open behind backdrop of white faux suede. Triggered by Cybersync.
...to the fateful limitations others have placed on their own lives. The vision of your true destiny does not reside within the blinkered outlook of the naysayers and the doom prophets. Judge not by their words, but accept advice based on the evidence of actual results. Do not be surprised should you find a complete absence of anything mystical or miraculous in the manifested reality of those who are so eager to advise you. Friends and family who suffer the lack of abundance, joy, love, fulfillment and prosperity in their own lives really have no business imposing their self-limiting beliefs on your reality experience.”
- Anthon St. Maarten -
Pic and quote below used on 'Best Ever Quotes About Cycling' quickrelease.tv/?p=486
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From Energy and equity: Toward a History of Needs. Ivan Illich, New York: Pantheon, 1978:
"The bicycle uses little space. Eighteen bikes can be parked in the place of one car, thirty of them can move along in the space devoured by a single automobile. It takes three lanes of a given size to move 40,000 people across a bridge in one hour by using automated trains, four to move them on buses, twelve to move them in their cars, and only two lanes for them to pedal across on bicycles. Of all these vehicles, only the bicycle really allows people to go from door to door without walking. The cyclist can reach new destinations of his choice without his tool creating new locations from which he is barred.
"Bicycles let people move with greater speed without taking up significant amounts of scarce space, energy, or time. They can spend fewer hours on each mile and still travel more miles in a year. They can get the benefit of technological breakthroughs without putting undue claims on the schedules, energy, or space of others. They become masters of their own movements without blocking those of their fellows. Their new tool creates only those demands which it can also satisfy. Every increase in motorized speed creates new demands on space and time. The use of the bicycle is self-limiting. It allows people to create a new relationship between their life-space and their life-time, between their territory and the pulse of their being, without destroying their inherited balance. The advantages of modern self-powered traffic are obvious, and ignored."
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Pic originally taken by the City of Münster press office, Germany
The economic downturn may mean that you are thinking of retraining as an alternative healer. You might be tempted to invest your redundancy money or savings in training courses and equipment. Think again. It may be far cheaper and much more lucrative to invent your own brand new form of quackery. Most forms of alternative medicine are at most only a few decades old or have only become popular recently. If others can become famous and wealthy by doing this, why can’t you?
Here is the Quackometer’s Guide to inventing a new branch of alternative medicine in ten easy to digest and holistic tips:
1. Minimise specific effects
Right. Let’s get one thing out of the way. Your newly designed alternative medicine is very unlikely to actually work. Progress in medicine does not happen with people just making stuff up, but instead relies on remarkable insight, careful analysis, detailed research and long and expensive clinical trials, with lots of false starts and wrong turns before progress is made. You will not have the time, inclination, money or intellect for this.
So, with little chance of being able to offer real benefit to your clients, the best you can do is to ensure you do as little as harm as possible. To this end, make sure your new quackery is inert, neutral and inconsequential in action. Take your inspiration from existing and successful alternative medicine. Homeopathy is just plain sugar pills. Acupuncture is just little pin pricks. Reiki is just hand waving. Bach Flower Remedies is just a few drops of brandy. Reflexology is just a foot massage. Even chiropractic is just a vigorous body rub.
If you make the mistake of delivering real effects, then you may well be found out and your new business will come to sticky end. That is why we do not see old sorts of quackery anymore such as blood letting and trepanning.
2. Maximise placebo effects
Make your treatment theatrical. Make your customer feel as if they have been listened to, been taken seriously, and then had lots of effort made on them to create a cure. This will ensure any available placebo effect is maximised. People will feel better about themselves if you make the effort. We know that the more dramatic the intervention, the greater any placebo effect will be.
So, spend at least an hour with your customer, asking lots of detailed questions, just like a homeopath. Use arcane terms and be thoroughly paternalistic, just like an old-fashioned doctor. Wear a white coat and have a brass plaque outside your spick and span clinic – just like a chiropractor. Get an impressive Harley Street address. Use equipment with dials and flashing lights. Take x-rays. Put certificates on your wall and, if you are doing well, have attractive receptionists. Give the impression you are creating your cure just for this patient. They are special. Make them feel so.
3. Choose what you want to cure carefully
The bread and butter illnesses for alternative medicine are the self-limiting (hayfever, flu, morning sickness) and the chronic but variable and cyclical (bad backs, arthritis, mild depression). The number one reason for people believing in alternative medicine is that it ‘works for them’. What this means is that their particular complaint just happened to improve sometime after rubbing whatever magic beans they had chosen.
Chronic illnesses are ideal – they represent repeat business. Bad backs are a classic. People will come to you when their backs are really playing up. Cast your spells, crack their bones and stick a pin in them and their pain will become less noticable. It will have gone away anyway. But now you have a loyal and evangelical customer. Correlation is causation to your customer. “Regression to the mean” is your friend. Understand it and use it.
Have excuses ready if things are not quite getting better yet – or even if things are getting worse. Homeopaths expect to see ‘aggravations’, that is, things getting worse before they get better. To them, it is more proof that the sugar pills are ‘working’. Have a story ready for every outcome, good or bad. Never admit you have failed.
Avoid illnesses with obvious end points, like death. Getting payment may be the least of your problems. If you want to be heroic and tackle illnesses like AIDS and cancer, best do it offshore. Find a country with fewer regulations, much lower standards of healthcare and more vulnerable people. Homeopaths tend to go to Africa to treat AIDS or prevent malaria. They might be imprisoned here. Find a nice spot in Spain for treating cancer. Or Mexico, if you are from the US.
Invent a ‘wellness’ programme. Tell people you can help them even if they are feeling fine. It’s preventative, you see. Chiropractors are masters at roping people into prolonged, expensive and unnecessary treatment programmes, all in the name of ‘wellness’. Nutritionists ensure people are popping highly ‘personalised’ lists of vitamin and mineral pills and creating a continuous and easy revenue stream for you.
Perhaps the most lucrative path is to invent illnesses. Create your own problems, diagnostic techniques and cures and you can provide an end-to-end service of imaginary illnesses and cures. The Detox industry has thrived on this. Food intolerances and allergies have made shed loads for vitamin pill sellers. Electrosensitives have been sold millions of pounds worth of useless EMF trinkets and neutralising boxes. People love their daily aches and pains, tiredness and mood swings to have a name and to have something to blame. You can provide a wonderful service by filling in the gaps for them.
4. Embrace the language of quackery
It is compulsory that you start using a few alternative medicine terms. ‘Holistic’ is probably the most important one. It will mark you out as a caring alternative type who wants to get to the ‘real’ causes of your illness, rather than superficial, but ‘money spinning’ ones, like viruses, genes and your smoking habit.
It does not really matter how monomaniacal your treatment is. All homeopaths ever do is dish out sugar pills and blame problems with your vital force. Acupuncturists stick pins in you and blame blocked Chi. A chiropractor will crack bones, even if you have an ear infection, and blame subluxations. Toxins cause all illness. So do parasites, acidic blood, vitamin and mineral depletion, miasms, vibrations, whatever. Pick one and stick to it. Describe yourself as holistic. No one will notice that you are the exact opposite.
‘Natural’ is another compulsory word. Do not trouble yourself that your treatment is completely unnatural. Vitamin pill sellers claim naturalness, despite their ‘food’ being the most highly processed and ‘space age’ form of nutrition imaginable. Be careful about what sort of ‘naturalness’ you highlight. Bach Flower Remedies work because they embrace the ‘goodness’ of the countryside hedgerow flowers. As John Diamond remarked, the public imagination might not have been quite so transfixed by ‘Bach Spider Remedies’.
Avoid using the term ‘alternative’ to describe your ‘medicine’. It is very 20th Century, and also frightens a potential lucrative source of income – government and insurance companies. Even ‘complementary’ medicine is falling out of favour. The hot button is ‘Integrative’. You want your business integrated with the health care provision of the state and private sectors. There is lucre there beyond your wildest fantasies – and the respectability of state endorsement. You do not want to be an alternative to a real doctor. Nor do you want to be complementary to them (some may see this as secondary and inferior). No, you want to be a ‘choice’ – a ‘lifestyle choice’ for the modern health consumer, and they can select you from within a single integrated market. Choice is the biggest biggest buzz word in healthcare politics in the UK. Make sure you offer it. People critising you will look like they are restricting consumer choice – always a bad thing.
5. Adopt the victim posture
Sooner or later, you may be asked why your new medicine has not been more wildly accepted and recognised by the medical establishment. The answer is simple: you are being suppressed by that very establishment. A powerful cabal of vested interests is trying to prevent the public from knowing about your discoveries and successes. ‘Big Pharma’ is the bogey man here. Use them to frighten the child in your customer. Highlight medicine’s failings and side effects and never mention their successes. If a critic highlights the successes of medicine, deny them and blame sanitation or fresh vegetables, or something. Under no circumstances, should you ever admit that a vaccination might be a good thing.
Say your invention cannot be patented and commercialised. No one can make money out of it (apart from you, but don’t mention that).
If a critic asks you for evidence about your treatment, then do anything but answer the direct question. Scream that the questioner is closed minded and probably a shill from Big Pharma. Say that your patients’ successes are all the proof you need. Claim that your technique does not lend itself well to ‘conventional’ scientific testing. But if some dodgy paper does exist, then wave it around furiously, despite just having claimed that science cannot measure what you do.
6. Wear the mantle of science
People love science. They do not understand it, but they love the authority of science. Most people form opinions based on various authorities in their life. So, embrace the authority of scientific language, but ignore the methods of science – the methods may show you are speaking hogwash. Your customers will not be interested in the details. They will never check references or take the time to understand what you mean. But they will be impressed by science experts and scientific language.
Quantum physics is your friend. Few people have any appreciation of it. And you can use the language of quantum physics to form cod explanations for whatever you like. Prefix the word ‘quantum’ to your treatment name. It sounds really impressive. Tell critics that they are stuck in a ‘Newtonian paradigm’ and that it is the quantum physicists that are really understanding what you do. Get a postmodernist sociologist to write some quantum gobbledegook to back up your claims. They will have no qualms – after all, science is just another ‘text’ and all viewpoints are valid. Another good trick is to claim foreign scientists back up your work. This makes it much harder to check. Russian science is a good bet – especially Russian scientists working on the space programme. Failing that, Chinese science is an excellent alternative, or even obscure Eastern European Universities. Cheeky people claim NASA pioneered their work. Few check.
Adopt the forms, behaviours and appearances of scientists. Once you get going, hold seminars and conferences. Book rooms in real universities to add kudos to the meeting. Remember to always book university rooms in the Medicine or Pharmacology departments, and never in Engineering, English literature or Law. Create a learned journal and publish ‘peer reviewed’ articles. However, never talk about data – that would be getting to be too close to real science. And you want to avoid that like the plague.
7. Envelop yourself in ancient origins
Having embraced the authority of science, you should also delve back into the historical origins of your treatments. Do not say that you have discovered your techniques – rather you have rediscovered them. Most alternative medicine has only really been around for the last fifty to a hundred years or so. Even Traditional Chinese Medicine was packaging and refinement made in communist China and then exported to the world.
Take a leaf out of the Ear Candling trade. They picked on an obscure American Indian tribe on which to base their claims of antiquity. Despite the Hopi writing to the manufacturers to deny the claims and to request they stop using their name, nothing has changed. People like to think they are tapping into ‘ancient wisdom’ and more ‘natural’ health approaches. Preferably use an Oriental connection. This is much more beguiling (and also harder to check). Ear acupuncture was invented in France and reflexology in America. Both are now found as part of the ‘traditional’ Chinese repertoire.
You may base your technique on some genuinely old practices like herbalism or acupuncture. But always overplay your ancientness. Acupuncture is claimed to be thousands of years old, despite thin steel needles not being invented until the seventeenth century and the first acupuncture point charts appearing at the same time. (Ancient China used bloodletting techniques with sharp flint blades – and this has been ‘re-interpreted’ as acupuncture).
8. Adorn yourself with titles and awards
Chiropractors love to put a brass plate outside of their office with the title ‘Dr’ on it, despite them not being medically qualified or having a higher research degree. It works though, so use it. People believe chiropractic to be some sort of medical discipline. If you do adopt the title ‘Dr’, it is also compulsory in alternative medicine circles to suffix your name with Ph.D too. It is a giveaway that you are a quack to sceptics, but your customers will be thoroughly impressed.
If you do not have a PhD then do not worry too much. There are correspondence courses where you can get one for a few thousand quid. A wise investment. Gillian McKeith was unlucky in being caught out. Chances are, you will not be. If you really have balls, just style yourself Dr anyway. It is not a protected title – it is yours to use.
But don’t stop there. How about Professor? You might get lucky, like Patrick Holford did for a while, and get invited by a minor university to teach. The title ‘Visiting Professor’ is so grand. Even easier, claim you are a professor from a very obscure overseas university. If it has burnt down and no longer has a web site, your claim is impossible to check. It will still get you onto the comfy sofas of day-time TV.
Awards are also impressive. Get someone to nominate you for a Nobel Prize. Anyone can do this. They may not accept your nomination, but hey? It is compulsory in alternative medicine circles to be nominated more than once, so you can describe yourself as ‘three times nominated for the Nobel Prize’. The Nobel Committee does not publish lists of nominees for understandable reasons. Otherwise, they would have to list my cat who I have annually nominated for the Economics prize.
9. Create two web sites and embrace weasel words
Legal matters need some attention. But not much. If you are selling through a web site, best not make too many bold claims about the effectiveness of your treatments. Trading Standards Authorities may come down on you like a ton of bricks. There is an easy way out: create two web sites. On the first, make as many bold claims as you like. Create a newsletter and ‘Health Club’. Fill your site with all your speculative and unproven nonsense. But, whatever you do, do not sell your product – maybe, just a few books. What you are doing is creating a ‘brand’. Then, set up a second, apparently unconnected site, that sells whatever you like and trades on your brand, but makes only very bland claims and no real claims to effectiveness. Easy. Sometimes, the web is so full of nonsense that might support the sale of your daft product, you do not need the first site: just tell punters to Google it, like Julian Graves does.
Be careful what you say in advertising. Do not claim to be able to cure things. Instead, claim to ‘treat’ illnesses. You may be totally unsuccessful, but you are not lying. Your punter will not notice the subtle difference between treating and curing. Learn lessons from Chinese High Street Herbalists who simply list ailments on the windows of their shops whilst making no claims whatsoever. Look at the Society of Homeopaths for their excellent exposition of weasel words.
10. Create a training programme and set up a regulator
Finally, to rake in true wonga, do not just sit around waiting for your next mark to visit you and hand over fifty quid. Real money is made by training others in your new practice. Set up a correspondence course and training programme. Set up an ‘Institute’ and award diplomas and certificates. A very minor university may even accredit you. It does not matter that your course is just made up idiocy, all that matters to Universities is that paying students will attend. They will tick the boxes to show that you are properly setting ‘learning objectives’ and ‘assessment strategies’ and you are away. Chiropractors have this one sown up with Universities underwriting their degrees. Take a lesson from them and ensure you tell your students that they are getting an equivalent ‘post graduate’ education to a medical doctor, even if this is patently false. Also, learn from chiropractors and spend half the time teaching them good business practices. You do not want your students to fail commercially.
Writing training materials may be hard work. You could follow the Reiki method, which is essentially a pyramid scam. Reiki practitioners are ‘trained’ by having a previously trained Reiki healer ‘attune’ them – essentially, wave their hands over them in a special way. Fees get passed back up the chain. They can then go on to ‘attune’ other people – usually ex-customers. Marvellous.
Then you can really kick off with the accreditation thing. ‘Skills for Health’, the government training quango, can then develop National Occupational Standards for you, just like they are doing for Homeopathy and Reiki. It matters not one jot that these subjects are pseudoscientific balderdash, you can gain nationally accredited skills training programmes in your new money spinning exercise.
Finally, all good alternative medicine should have a ‘regulator’. To the public, it will look like their chosen healer is being monitored for the efficacy and safety of their work. To you, it is a good advertising device and channel for new customers. There are hundreds of regulators for alternative medicine in the UK. All have one thing in common – they will never condemn or criticise any of your practices, or strike you off for anything other than sexual misconduct – and then, at a push. You will be safe to do what you like without fear of being judged by the ‘regulator’.
Even the UK government will provide this sort of service to you. The Complementary and Natural Healthcare Council, or Ofquack, was set up this year by Prince Charles and his Foundation for Integrated Health and a government grant of £900,000 to be a ‘one stop shop’ regulator for all manner of quacks. However, they have made it quite clear that they are not interested if the treatments actually work, but only if the member has been trained in their alternative medicine and have insurance cover. It matters not at all that the training might be utterly delusional and result in dangerous advice to customers. All the boxes have been ticked.
And so there you are. Not too hard. Finally, the best top tip I can give you is for you to find a way to start believing in your own bullshit. You will appear far more convincing to people if you believe yourself. As Richard Feynman said “The first principle [in science] is that you must not fool yourself — and you are the easiest person to fool”. If you are not interested in truth then hurry along and get fooling yourself. It should be easy. Once you have done that, fooling everyone else is a doddle.
Good luck, and check back on these pages for when I write about you.
www.quackometer.net/blog/2009/03/top-ten-tips-for-creatin...
My dealer buddy/friend, who self-confessedly knows this topic better than I, said he thought these two young girls might be in the business. Certainly, they are casually affectionate, in a way that two young girls who perhaps shared a self-limiting occupation might be. I find them appealing in their friendship and light-heartedness.
More growth forms. Decided to focus on exploring the range of self-limiting forms in the system for a new work, Limits to Growth.
You can find Eileen McKusick on the Interactive Media Exchange where she will never be censored.
i.mediaentertainment.exchange/eileenmckusick/?afmc=V4NSgn...
Eileen McKusick:
My vision is to see humans free from self-limiting beliefs and misinformation that keep us small, powerless, and locked into expressing just a fraction of our potential. Within each and every one of us is the coding for vibrant health, connection to ourselves, each other, the earth, and the cosmos. Awakening from the illusion of separate particles, into the truth of a unified vibrating field, is currently underway. It Is just a short matter of time before medicine moves from a chemistry-based approach in health to a physics-based one.
#InteractiveMediaExchange
#InteractiveMedia
You could get lost in your fantasies today about producing great works of art, but you may needlessly worry that you lack the talent to pull it off. Nevertheless, allow yourself to imagine what you might do if you didn't need to earn a living and manage your everyday responsibilities. There's no place for self-limiting thinking now, so express yourself as creatively as you can. Make time for playful endeavors, even if only as a practice to connect with your inner child.
(Libra horoscope for 1/27/12)
Week 4 ~ Embracing Pluto with Vanessa
“As you come into yourself more, what do you want to create in 2017?”
“I want to create an expression of myself that’s completely untethered and free. I want to melt away all personal judgments and self-limiting beliefs so that I can be as free as I feel my soul and spirit are. But in the expression of my human body. Not forgetting the body and shooting straight up to spirituality, but bringing spirituality to my body and staying embodied and of spirit at the same time.”
#soulsofhive from the Hive program (2/3)
b is for bonding, family bonding
It is through touch and tenderness that we expose ourselves and render ourselves vulnerable. To allow another close enough to touch us, we have given away some security and built a bridge of trust.
Of course, in our family it is this trust that allows us all to push ourselves beyond our self-limiting boundaries. In our touches, we pass on support and encouragement. In extending our touch to those around us, we build peace, and hope that it ripples outwards like the wave from a stone thrown in a pond.
TRP: Touches
FGR: Poke it with a Stick
TOTW: Extreme Love... and Borders too :)
Hereford, Herefordshire
St Mary the Virgin and St Ethelbert the King
Cathedral
en.wikipedia.org/wiki/Hereford_Cathedral
Beyond Limitations
by John O'Conner
Another classic piece in John O'Connor's inspirational collection of emotionally charged artworks.
O'Connor Explains:
"More often than not, our potential far exceeds our self-limiting ideas of ourselves."
This piece is not only a reminder of this, but seeks to clearly state that you can achieve and be much more than you imagine yourself to be. It's a symbol of self-empowerment and celebrates a courageous spirit, beckoning us to step beyond our own illusions to become the greater man or woman that you truly are.
Beyond Limitations is cast in iron resin and stainless steel.
It is displayed in the Lady Arbour Cloister Garden.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
This section possibly contains original research. Relevant discussion may be found on Talk:Spaceflight. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (June 2018) (Learn how and when to remove this template message)
Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
To celebrate the Hubble Space Telescope's 16 years of success, the two space agencies involved in the project, NASA and the European Space Agency (ESA), are releasing this image of the magnificent starburst galaxy, Messier 82 (M82). This mosaic image is the sharpest wide-angle view ever obtained of M82. The galaxy is remarkable for its bright blue disk, webs of shredded clouds, and fiery-looking plumes of glowing hydrogen blasting out of its central regions.
Throughout the galaxy's center, young stars are being born 10 times faster than they are inside our entire Milky Way Galaxy. The resulting huge concentration of young stars carved into the gas and dust at the galaxy's center. The fierce galactic superwind generated from these stars compresses enough gas to make millions of more stars.
In M82, young stars are crammed into tiny but massive star clusters. These, in turn, congregate by the dozens to make the bright patches, or "starburst clumps," in the central parts of M82. The clusters in the clumps can only be distinguished in the sharp Hubble images. Most of the pale, white objects sprinkled around the body of M82 that look like fuzzy stars are actually individual star clusters about 20 light-years across and contain up to a million stars.
The rapid rate of star formation in this galaxy eventually will be self-limiting. When star formation becomes too vigorous, it will consume or destroy the material needed to make more stars. The starburst then will subside, probably in a few tens of millions of years.
Located 12 million light-years away, M82 appears high in the northern spring sky in the direction of the constellation Ursa Major, the Great Bear. It is also called the "Cigar Galaxy" because of the elliptical shape produced by the oblique tilt of its starry disk relative to our line of sight.
The observation was made in March 2006, with the Advanced Camera for Surveys' Wide Field Channel. Astronomers assembled this six-image composite mosaic by combining exposures taken with four colored filters that capture starlight from visible and infrared wavelengths as well as the light from the glowing hydrogen filaments.
Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
an illustration to demonstrate what recombination looks like compared to the immortality system where mating signals the beginning of the parent's death process.
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Summarising what we know:
Humans are here to consume and enjoy life as the safest middle organs of life.
There is nothing a planet or a star can gain by hurting them... the entire point of this situation is to get them to stop channeling the self-limiting punishment mindset, because it is only serving to slow down the development of positive life changes.
As long as we fall for the idea that humans have to be limited by gender or by age or by ethnicity, then humans are simply being channeled into dangerous social engineering.
If you can not get humans to do something FOR you, then you are not being inspiring enough.
It was demonstrated to me that pain is completely at the will of the hyperdimensional life and that it can be turned off or on nearly instantaneously... so don't waste my time trying to convince me to reduce something else's pain. If the hyperdimensional beings want it to feel pain then there is little I can do about that... which is why I refuse to accept that planets or stars should be able to abuse something into action... it is only in their best interest to inspire change and help humans become what THEY want to become.
Humans are OBVIOUSLY life seeing what it can accomplish when it throws aside the bullshit self limitations and really lets things happen.
Let us happen.
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Something is making a scissor sound effect and saying "scissors beat the paper that beat the rock"
But in this context, paper doesn't beat a rock, this is the mindset that binds everything together in the Galaxy being recorded... so paper can actually SAVE the rock, and if the scissors are still claiming that they want to sever the bonds between this planet and its star or the star system and the
Galaxy and it REALLY intends to follow through on that, then I would be surprised if its something on the planet.
But if it is something on the planet... then its misinformed (or disbelieving) about the process of rebirth and souls, insane, suicidal, planning to hijack the planet away from the star, or bluffing.
(I think those are the likely situations, if I missed something, let me know)
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Oh yeah, it could also be something that completely understands this situation and is lying into transmitter machines while claiming to be other people in the hopes that it causes those people to get attacked "for being wrong".
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If its not on the planet, then its possibly a stellar being trying to find out what happens when it argues with planetary beings, it could be a transmitter ship, it could be something from another star system that is trying to take over our stellar materials, or destroy our planet for any number of reasons...
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In any of these cases, it seems somewhat worrisome that this "scissors mindset" keeps getting into the elements and that at least with how its interacting with me, its being full on abusive and none of those scenarios is justified.
Its clearly something that profits by taking advantage of anything that isn't aware of how Galactic Culture lives.
So here's rock beating scissors.
Now its your move to provide YOUR paper.
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something says "but we don't have the resources to turn things into what they want to be."
Then why are you wasting what little resources we HAVE to hurt people and limit them?
You claim you have the resources to harm cows, tell people about it, and then torture those people... and yet you CAN'T AFFORD to be something enjoyable?
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Stop making me feel pregnant! I don't WANT to know what it feels like to pregnant. I believe that as long as I don't give birth or impregnate someone, that the process of aging will no longer effect me, because that is a valid life program under the ideal of "zero population growth".
If everyone thought that bringing a child into the world was them signaling life that they have given up on their body and want to recombine it into something else (and then die)... then I bet MOST young people alive today would NOT make children.
How would this improve life?
1. it would allow humans to engage in long term goals that they currently feel are impossible.
2. if we compare the mating system with a group of immortals, over the course of say a century or so... we will see the mating group give birth, raise their children, and then die. As many families have more than 3 children, this group is almost certain to have a positive population growth over this time, and there is much more resource use with parent / child lifespan overlap. The group of immortals will by definition of their lack of children will have a guaranteed zero population growth, and some may choose to end their lives or die of accidents, murders, or diseases other than aging (if those systems are in place during this century), so there is a likelihood that this group will atrophy a small bit.
Therefore, if you are concerned about solving population growth, make having genetic offspring the signal that you are giving up on your immortality in your body and seek death once your offspring are stable... and then see who decides "they have to mate".
3. It would allow for a greater range of learning, experiences, and for lives to feel more fulfilled and less "a race against the clock" which will remove much of the pressure to "keep up with the joneses" from the economic system. I know this is a subtle effect, but I think the changes immortality would have on things like economics would be huge over the first few decades.
4. Consistency, historical accuracy, better planetary record keeping. Imagine that instead of opening a book to read about the American Revolutionary war... schools could hire famous soldiers who fought in the various battles of the war to come speak to the students about what it was like to go through it. Imagine what a hundreds-of-years-old Leonardo DaVinci could have accomplished.
5. Less redundancy in learning. If we take those two groups from #2, the group that creates offspring spends a lot of resources starting over raising a new generation every couple decades... multiplying as they go... with each new life needing almost 20 years of startup time, and a decreasing ability as they are abused into a state of elder age. The effective adult working life of this mating group is about 50 years per person currently. The immortal group on the other hand simply keeps learning and changing and experiencing until they decide they are done, so once they get past their childhood, no hyperdimensional or elemental resources are wasted artificially aging them, and they can calmly go about their business without fear playing such a huge role... for as long as they want to.
Over time, the mating group loses knowledge over time and has to go through the same basic lessons over and over with each new generation. Now imagine trying to trick a 400 year old that had been all over the world, lived almost every job and lifestyle, and who still looked like a young healthy adult.
6. Some people have tried to sell the idea of immortality as dangerous, but it would call a bluff of something that is dependant upon keeping humans in an infantile state of life compared to what they SHOULD be like.
7. This WOULD also free up the system of "aging" to end the lives of anyone that has created their genetic offspring much faster than currently, since they have made a conscious signal to life that they have found someone that they have chosen to mix their genetics with, and to die once the child is stable, so that their genetically mixed children may live. What I mean is, let's say Bob has lived for 400 years and finally decides that he no longer finds life that interesting, but he finds a woman that he believes is his perfect mate, and that if they combine their "genetics" together it will create something even better than himself... so he creates his offspring and then raises it, and once the child has reached the generally accepted age of adulthood, then if resources are in question in any way, or Bob's justifiability is challenged, then he would essentially be living in "sudden death mode"... and the forces that deal death would be able to act swiftly and without subtlety... and if he was aware of the consequences of mating, then it may even be something he is SEEKING... because for all we know living thousands of years might become a hassle that someone WANTS an exit strategy for.
This allows people to set their own death in motion, and with some part of themselves still remaining in the form of their recombined "genetics".
8. Sex would be taken a hell of a lot more seriously, since there is far more at stake for someone to lose in the case of an accidental pregnancy. This would also serve to draw people away from an overly sexual mindset, since children and sex would not be such a sought-after experience or goal any more... instead of sex being associated with the act of spreading life, it would become associated with the business of death and of change and of ending one life and starting over with another... changing sex and birth from glorified into something far more somber.
9. One of the great ways to signal to people that life is interested in this system and is going to give a try would be to just start doing it... don't bother trying to ease into it. The relatively quick and sudden deaths of people with adult children and the agelessness and health of those who remain childless or celibate would probably begin to catch the attention of the public and help drive home the idea that sexuality is no longer that sexy to life. If you are trying to reduce population and change people's relationship to sex and aging, there's no time like right now to start.
Think about it... this could be how we solve any complaints about population.
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(and this is where official BIRTH CERTIFICATES that list the mother and father's names COME IN REAL HANDY)
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Question:
"What if someone keeps having children so they can live forever and still mate?"
If the whole point of this is to reduce population, then just consume and kill them faster with each new child they bring into the world. That will keep "tribble families" from being too successful... as they will look strange and even the children are likely to suffer health problems while their irresponsible parents are being eliminated... and their offspring will probably not be seen as something that an immortal would WANT to give their eternal life to mate with, unless that offspring was able to overcome the mistakes of their parents.
and that brings up another good point... even if someone decides that they WANT to mate... when they are seeking a potential mate to raise offspring with... they will have to convince another potentially immortal person to give up their future and join them as a "death partner". Which is going to raise the stakes on dating, sex, and marriage a FUCKTON.
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Another subtle side effect is that since females that rely ONLY on sexuality benefit from the old "no immortality option" system the most... by being the protectors of "mate selection" and reproduction by carrying the fetus... and since many males don't want children and resent the pressures to take on a mate and raise children, the immortality option will actually be welcomed by many as a justification for their desires...
Another one of the changes we will see is that females will have to begin being the ones who take on the more active or "aggressor" role in sexuality if they want to control everything through their reproductive ability only... and for some reason don't find an ageless option attractive.
Also... people who choose to remove their genitals through orchiectomy or historectomy would be able to remain as sexual as they want to, without any risk of accidental pregnancy and loss of their ageless state... which would make transgenderism attractive as an option in a whole new way, and help spread the idea that population growth is SOLVABLE.
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If the only way you believe you can change human behavior is with physical abuse, then you are attempting to cause changes to life that are unjustifiable... so this system actually allows for people to remain with less suffering and only have to face aging by their own actions.
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"I discovered that a seductive woman is a trap more bitter than death. Her passion is a snare, and her soft hands are chains. Those who are pleasing to God will escape her, but sinners will be caught in her snare."
- Ecclesiastes 7:26
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Another advantage of making parenting children a spiritual signal that you have begun the death process is that in a system where reproduction is not punishable (or even encouraged) then adults are far more likely to have decades of reproductivity with many different potential partners, having children with a decade or more between their youngest and oldest born.
For example I was told that my bi
ofather had children with 6 other females than my mother, and that the oldest of them was almost 20 years older than me.
In a system where one of the your children reaches the age of majority means a parent is now in "sudden death mode", they will have probably spent more time focusing on the quality of their parenting, making sure that their offspring will be prepared for life without need of their help.
This also begins a ticking clock situation for anyone who offsprings... and if they begin trying to make other children, and the children or their partners feel they are not dedicated enough to raising their offspring (frivolous mating habits)...
Then obviously the pressures of life can spiritually feel righteous to end that wasteful person's reproduction and irresponsible resource use by ending their life.
*
So, under the "immortality or recombination" system... my biofather would have been dead nearly 40 years ago, instead of languishing in prisons for most of the last 4 decades, wasting resources and tax payer money.
*
Another way to phrase this:
Is having children important enough to someone that they would willingly give up an ageless body and die much sooner than their peers... simply to recombine their dna with someone else?
I took several shots from different angles and was pleased to catch this young, male, adult blackbird with his beak interestingly open. Then I realised that the beak was permanently open. He seems to be affected by a parasite called gape worm which is acquired when eating infected earthworms. The parasite lives in the bird's trachea and sufferers often have this locked open bill. The infection can be self limiting and the bird might recover. I considered trapping him but decided not to stress him further. After a couple of weeks he is surviving but as yet there is no sign of improvement. I seem to see a distressed look in his eye but it is easy for us to project our concerns onto a creature that does not have our range of facial expressions.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
This section possibly contains original research. Relevant discussion may be found on Talk:Spaceflight. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (June 2018) (Learn how and when to remove this template message)
Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
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The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
This section possibly contains original research. Relevant discussion may be found on Talk:Spaceflight. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (June 2018) (Learn how and when to remove this template message)
Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Photography by Philip Weller | Performance & Concept by Karina Pinzón
We invite you to dance with us into the sensual and mysterious dream world of DESEO. This visual story illustrates our protagonist's wavering between the guidance of her inner light and the beckoning of her darkest desires. It explores the process of how we honor our divinity and reclaim our innocence, while embracing our sexuality and indulging our mind-altering appetites for pleasure — all in the shadows of shame, self-limiting beliefs, destructive attachments, and maybe even erotically-charged spiritual warfare.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
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This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
• Jimpawcle: Constituting the most prominent and severe domestic menace regularly faced and commonly feared by the native Favredian population of Olsuclund, Jimpawcles are exclusively-carnivorous, and accordingly vicious, mammalian predators that live and hunt in packs of up to several dozen individuals. Such groups and their activities are generally centralized around self-designated local areas - relatively flat/even stretches of terrain seem to be preferred - over which the beasts are fiercely territorial, responding with violence toward all intruding entities, including others belonging to their own kind but different packs thereof. Indeed, Jimpawcles are quite prone to infighting within their species based on arbitrary group affiliation, and are able to tell trusted brethren apart from "outsiders", in spite of there being no visible differences between their race's various sub-populations, by sense of smell, with the members of each pack carrying a very subtly unique scent, detectable only by other Jimpawcles, based on the specific features and environmental conditions of their respective territories. Unlike most predatory, pack-dwelling animal varieties found elsewhere, Jimpawcles lack any kind of hierarchy within their packs, where all individuals hold equal standing; this is most evident in their polygamous reproductive habits, where any/all males of a group are liable to mate with any/all of its females.
Although Jimpawcles may occasionally make primitive bids to expand the alleged "borders" of their groups' dominions, any resultant spreading of their population(s) is close-to-negligible as far as any other beings are concerned, and despite generally not posing an active, direct threat to major Favredian settlements, the beasts nonetheless end up causing more than their fair share of humanoid casualties as "field hazards" to hunting parties and others traversing the Olsuclundan environment beyond the confines of their communities. Upon one's stumbling into the unmarked boundaries of a pack's territory, multiple Jimpawcles will frequently show up to attack in rapid order, without warning and seemingly out of nowhere at times, and the creatures are exceptionally adept at ruthlessly ganging up on their targets.
The physiology of the Jimpawcle is that of a posteriorly four-legged, horizontally-postured organism with a fully-upright torso bearing two long, clawed additional arms and a headpiece that possesses certain reptile-resembling features, as does the flesh covering the length of its dorsal starting from the back of said head's neck. Furthermore in terms of reptilian attributes, the characteristic noise of which the Jimpawcle's unintelligible vocalizations all consist resembles not a roar, a growl or even a howl, as one might expect based on the creature's behavior and overall ecosystem role, but rather what can only be described as a distinct hiss. Given how much more distantly-audible and conspicuous a more obvious, louder sound would be as an indicator of Jimpawcles' presence, the hissing nature of their vocals, if anything, enhances the danger they pose to many a traveler, and non-native humanoid explorers in particular, since it is much more difficult for the uninitiated/unprepared to discern it from a safe distance, with the beasts often already being in the process of actively closing in by the time one is close enough to readily hear it.
Like most other organisms present on Olsuclund, the Jimpawcle possesses very tough skin on most areas of its body and even some built-in light protective plating upon certain spots, but conspicuously, its bare feet are among its few parts to bear no such resilience-enhancing features, which is easily the creature's most glaring specific weakness, and makes tactful footing a necessary skill for it to quickly develop during its life. On average, Jimpawcles are marginally greater in total mass than Favredians, but tend to be just slightly shorter in height as well as inferior in their durability, which is valued at 800-950 for the animals compared to the burly avian humanoids' range of 1,000-1,300.
• Metzilume: Arguably the most distinctive-formed of Poulbrimian organisms - having the most unique appearance and build - as well as often being considered some of the Qendsewn homeworld's least-repugnant animals, Metzilumes are peaceful, omnivorous - but primarily plant-eating, with Hatiginiffs being the only other significant beings they consume with any regularity - beasts found, usually living among several others of their kind, within and around various stretches of swampy terrain and marshy alcoves across the planet's map, and very seldom in any other biomes (not that Poulbrim boasts much of a variety thereof). Capable of reaching body lengths of ten feet or more, they are the largest of their desolate home planet's naturally-occurring inhabitants, and among the only ones to be largely left alone by the vicious Ulirooh swarms that have dominated much of the planet's wilds throughout all of recorded history, with their size being instinctually perceived as intimidating by, and thus deterring most potential attacks on them by, the monstrous flying insectoids. This effectively protects Metzilumes from what might otherwise be a threat to their very survival as a species, with the creatures having very little combative capacity in reality and usually ending up getting slaughtered in the rare event that they actually are attacked, whether by Uliroohs or otherwise.
The Metzilume's lengthy, partially-segmented body is horizontally-oriented for the back half of its length, but anteriorly curves into a more upright position starting just past where the frontmost of three pairs of legs meet its lower-belly. The most notable facial feature of the beast is what may appear to be a set of as many as seven eyes, but consists in actuality of three eyes surrounded by a number of physically-functionless embossed markings seemingly designed to superficially resemble true outlets of vision, ultimately contributing to the Metzilume's perceived imposing appearance which is, again, a key asset for its survival. Other points of visual interest on the headpiece include an upward-extending set of three cartilage-based horns as well as fleshy orbs, bearing multiple protrusions, which constitute the Metzilume's ears and are, in fact, the most vulnerably sensitive external parts of its body. Tentacle-esque twin tails extending from the creature's posterior and bearing hard, moderately sharp-edged end-pieces, meanwhile, provide the Metzilume with the closest it has to an adequate method of actively defending itself through attacking, in this case by means of haphazard lashing.
Metzilume flesh is squishier and consequently less resistant to puncturing, burning and the like than most, but what bones the beasts - whose simple skeletal systems consist of little more than what is strictly necessary to support their basic body shape - do have are, in sharp contrast, exceptionally dense and sturdy, being the strongest bones found in any Poulbrimian organism. While this does somewhat offset the relative weakness of the rest of the Metzilume form, the benefit is, in practice, less substantial than one might expect: the majority of feasible injuries to the animal that would even pierce deeply enough to be directly resisted by any of its bones (especially the ones in the main torso length), would, in most cases, be fatal anyway due to the grievous, blood-loss-entailing damage sustained by its flesh prior to its bones even becoming a factor in shock-absorption. All things considered, the Metzilume's overall durability value, on average, is about 900, while the most significant practical function ultimately served by the solidity of its bones lies not so much in protection from outright trauma, but more-so in casual leg-and-foot support during sustained manual locomotion. During the early phases of the humanoid race's long history of experimental, unorthodox scientific endeavoring, Metzilume bones were commonly harvested by Qendsewn, who otherwise have no use for the creatures, for use in various projects as a high-strength organic constructive material. Fortunately for both the animals and the humanoids, this has since become obsolete as the Qendsewn have gained ready access to equally (and later still, superiorly) sturdy materials that can be used nigh-identically in their experiments.
• Doilerbaum: A rather diminutive and ostensibly, yet quite deceptively, harmless-looking winged mammal native to Meilbatsy, the Doilerbaum primarily makes its home amid the same network of elevated landmasses that also provides the foundation for Rabbyphune civilization's centers, dwelling there in large family units. Collectively, these often-rapidly-produced families constitute an exceptionally massive total population for the animal's species: there are, in fact, more Doilerbaums than there are Rabbyphunes on Meilbatsy, though the same cannot be said in regard to the whole of the Prime Galaxy, where Rabbyphunes have proliferated and colonized elsewhere while Doilerbaums, like most non-humanoid animals in general, remain strictly confined to their home planet. In addition to their main areas of habitation, Doilerbaums can also be encountered on occasion all throughout the various lowland regions comprising the rest of Meilbatsy's surface, though never in the same large numbers.
With their largest specimens standing just short of one full meter in height (even with their tall, antenna-like ears accounted for) and their durability values rarely surpassing 500, Doilerbaums possess neither an imposing form nor anything even remotely resembling superior physical strength, yet arguably benefit in other ways from their size more than they ultimately suffer from it. Limited mass and correspondingly low energy intake requirements for sustaining their petite bodies allow the Doilerbaums' great numbers to be sustainable without the matter of having enough space and food to go around becoming exacerbated as a result of their huge population. Additionally and rather more interestingly, at least as the average reader of this will likely be concerned, their small build strongly compliments that of their wings, which, in relation to the rest of the Doilerbaum form, are just sizable and strong enough to adequately carry the nimble bodies from which they protrude through the air, granting the ability of free flight, while not being so substantial and heavy as to prove burdensome for their bearers while not in use. Being able to fly, in turn, gives the Doilerbaum, already a fleet-footed and craftily evasive creature on the ground and even able to perform a special sprint powered by all four pairs of its arms and legs, a tremendous extra advantage in terms of escaping from predators and other hazards. However, it is only in the rare event that it is confronted by a foe from which it, and any of its brethren who happen to be present and likewise-threatened, cannot flee that the tiny beast's most impressive ability of all comes into play.
Upon the end of every Doilerbaum's insectoid-esque tail rests a bulbous, dark-red stinger, via which the animal is able to deliver among the most potent of all venoms to be produced by any mortal organism: a poison that will quickly - yet no-less-painfully for the swiftness - kill any living thing found on Meilbatsy as well as virtually all visitors/explorers from elsewhere in the galaxy, with very few beings out there standing any chance of survival. Fortunately for Rabbyphunes and any others of benign disposition who would otherwise face a severe natural hazard in them, Doilerbaums are not aggressive or reckless with this most frightening and drastic of their abilities, and for good reason, for its use comes with major drawbacks and limitations stemming from the fact that each of the creatures' supply of the pernicious venom involved being both extremely limited and utterly unable to be replenished. As such, a Doilerbaum can only ever deliver two proper stings, the second of which will deplete and destroy its tail - a critical structural supporter of multiple internal organs - and lead to its own excruciating death. Despite this, Doilerbaums that have already stung once before rarely experience any hesitation over what will amount to a suicide attack, for whenever one of them is threatened by an inescapable foe, which usually comes in the form of a den-intruder, multiple others in its family unit are generally at risk as well, and per the small beasts' instinctive mentality, sacrificing oneself for the good of one's group is considered an unquestionably worthy cause.
• Etchfulber: Simple-minded organisms of largely passive disposition, Etchfulbers are a semi-common sight on Alfriiden, where their naturally-designated role is as prey animals to multiple other Alfriidenizen varieties. Small-to-average in body volume but considerably greater in effective mass by virtue of being extremely dense by the standards of most organic beings, the core frames of Etchfulbers are flat-faced and nearly rectangular in shape, and have been likened on numerous occasions to fleshy, slimy, icy "bricks". Given how the creatures' bodies have come to be commonly harnessed post-mortem (read below), such a comparison's rise to prominent recognition was all-but-inevitable in hindsight.
An Etchfulber's main set of arms can accurately be considered as one-and-the-same with its legs, in the sense that the beast does not, in fact, have any limbs of the latter variety, and relies on the former both to carry the bulk of its own considerable weight and for the usual purposes assigned to arms that accompany actual legs. To elaborate: the Etchfulber walks upon four muscular, fuzzy-haired primary arms, protruding from each upper-corner of its torso and ending in five-fingered, typically fist-clenched hands of multicolored crystalline composition (which are actually the creature's most densely-compacted body parts of all), while also boasting pairs of smaller, more flexible four-fingered claw-bearing arms positioned just below its faces and used primarily for scooping things into its mouths. Regarding the use of plurals in the preceding sentence, the Etchfulber does indeed possess two identical faces at opposite ends of its body, with the anus mutually led to by both mouths' digestive tracts existing as a gaping hole located on its underside halfway across the length between them. This also conveniently allows excrement to be deposited downward at a straight angle, falling directly onto the ground while seldom leaving any residue stuck to the Etchfulber's body due it lacking buttocks as well as having very moistly slippery flesh in general. Note that, like other mortal beings with multiple visible heads and/or faces, the Etchfulber still possesses only one consciousness between them, with its singular brain residing at the top-center of its overall main body, more-or-less vertically-opposite (directly above) the animal's previously (and rather-gratuitously; we hereby apologize for any disgusting images brought to anyone's mind there) described anus. The entirety of an Etchfulber's body is of extremely low (by standards of living organic matter) natural temperature, even compared to other Alfriidenizens, giving much of its form an ice-like, "frozen" quality which increases its effective resilience in some respects but also renders it weak against heat-force and certain applications of physical trauma that may lead to shattering. All in all, the beast's durability value is close to an even 800, with little variation in this statistic between specimens.
A slow-moving as well as slow-witted organism that does little more than eat and sleep, the Etchfulber is ultimately most notable not for any facet of its own behavior or even for its inherent physiology (which is admittedly very peculiar), but rather for the extremely unique way in which its bodily matter has come to be utilized by others, namely the humanoid Spepescuos, as a long-lasting preserving and cooling material superior to purified ice. The specific form of tissue harvested to this end comes mainly from the skeletal muscle found in the upper-flanks of the Etchfulber's bulky torso, and must be specially prepared and treated via a process that only Shepescuos know the secret to before it can be properly used in such a way. Over the last few centuries, the Shepescuos, whose people once reserved this resource for their own use exclusively, have increasingly recognized, and taken advantage of, the profitability of selling it to interplanetary traders as an "exotic" or even "collectible" commodity, a business that stands as their mostly-isolated and somewhat ill-reputed race's most prominent venue of interaction with others in the greater Prime Galaxy today. The Etchfulber population, meanwhile, has declined significantly as of late as a clear result of this practice's growing lucrativeness, although as of yet, the species itself has not reached the point of depletion necessary for it to become officially classified as endangered and accordingly protected from further destructive exploitation.
• Quottynorb: A semi-amphibious (that is, capable of underwater respiration but physically unfit for adequately traversing submerged terrains and having no need to ever do so), quasi-reptilian and otherwise unclassified creature, the Quottynorb is one of the larger, yet functionally less prominent, predatory animals of the Virslaglish ecosystem, being found most commonly in areas of lower elevation relative to sea level. It is most readily recognizable by its vertically-elongated (read: tall) cranium whose face bears four large eyeballs and a nasal system externally manifested as what amounts to three visible noses, as well as by the set of five legs - a very rare specific number of such limbs for any organism to have - by which the rest of its body is supported. Quottynorbs are asocial and generally unfriendly beings, with each specimen living and hunting on its own and the beasts' mating rituals and periods of active parenthood both being relatively short-term commitments; their disposition towards Hexpultis and most other humanoids, meanwhile, is such that they will give warning in the form of a low-pitched, gurgling growling at the sight of one or more in their vicinity before attacking if approached any further. Intelligence-wise, the Quottynorb is competently-coordinated but uninspired, displaying surprisingly above-average situational judgment and cunning throughout its constant endeavors to fulfill its own basic needs as an animal, yet lacking any drive to utilize that intuition toward more sophisticated (even by wildlife standards) ends such as teamwork with other specimens, construction of more substantial shelter for itself and the use of objects in its surroundings as tools. This self-limiting mentality is demonstrated most evidently through the less-than-optimal capacity in which the most unique built-in asset of the Quottynorb organism, that being the presence of long osseous rods holstered within the lengths of either of its arms that can be partly or wholly unsheathed from beneath the wrists at will, and likewise-discretionarily charged with deadly (to all but their own user) heat energy of nearly molten intensity, is used for purposes of violent aggression alone. The Quottynorb simply never thinks, or doesn't care, to utilize this remarkable mechanism for anything more creative or ambitious, such as using its rods to reach high-placed objects or cooking its food via fire manually generated by their heat. Quottynorbs never live for more than fifty years, with this limit to their lifespan being far stricter than for most other mortal beings, to the point of natural death from age occurring extremely abruptly, with no externally-discernible warning signs or "slowing down" of the animal's apparent functioning beforehand. Some have even been witnessed to stop literally dead in their tracks, slumping over in place after having appeared to be moving around healthily mere moments prior.
Grown Quottynorbs measure up to a median height of roughly two meters, therefore standing close-to-evenly with most of the Hexpultis warriors who are, naturally, the humanoids they come into contact with most commonly by far, and are comparably sturdy as well, with their durability values typically ranging between 900 and 1,100. The meat of the beasts is edible to the humanoids but not considered a delicacy by them, and as such the former are hunted for food resources by the latter occasionally but not regularly. Somewhat conversely, while neither Quottynorbs nor the insectoid Zinnktoses - Virslagly's most infamous predators - can actually gain nourishment from the other's flesh, the two creatures are innately hostile to one another all the same, with the former being vastly more powerful individually but the latter possessing strength in just-as-vastly greater numbers whenever they fight. Although all attempts by other beings to directly salvage and harness the Quottynorb's heated polearms have proven fruitless, Hexpultis engineers have nevertheless managed to construct their own high-temperature, retractable melee armaments inspired by and bearing decent physical and functional semblance to them, which have in turn been imitated by other weapon-crafters in galactic society.
• Wurkenko: Known as the largest of all beast-hominid varieties, the Wurkenko is a sparsely-populated (per natural status quo) species indigenous and exclusive to Barserinv, among whose resident creatures it is the most massive by a considerable margin. Standing up to eight meters when fully-upright (but more often than not encountered in hunched-over, crouching or even fully-doubled-down posture, frequently out of necessity so as not to bump its head into ceilings), it is a reclusive woodland-dwelling mammal with a habitual affinity for making its home in and around large naturally-formed caves found amid such environments, which seem, quite conveniently for it, to be rather inexplicably plentiful throughout most of Barserinv's regions. Wurkenkos are, furthermore, highly resourceful and creative - insomuch as unenlightened, wild creatures of their nature can be - when it comes to their living arrangements and the "furbishing" thereof, commonly clearing out trees and such from the areas surrounding their lairs so as to give them selves more room to comfortably roam around in, as well as building rudimentary structures from boulders, tree trunks, etc. to exteriorly supplement their dens. Predictably given these tendencies, they are also fiercely and selfishly territorial, leading to many a lesser animal being driven from its home when one of them decides to move into the area, but somewhat paradoxically in spite of this, they never maintain a single residence for the whole duration of their generous natural lifespan of approximately eighty years. Rather, the average Wurkenko voluntarily resettles itself at least three or four times, entirely abandoning everything of its previous home on each such occasion, over the course of its existence, providing it does not die prematurely, which is rare thanks to its species' innately great physical strength and durability (valued at 3,500-4,000). It is also during these periods of searching for new dwellings that most of the mating between Wurkenkos occurs, with the males involved resuming on their solitary ways shortly after the act of procreation and the mothers alone being responsible thereafter for the raising of their young, which generally lasts for the first four-to-six years of young specimens' lives. Though being strictly herbivorous, and one of the largest and most formidable animals in the whole of the galaxy to exhibit this dietary attribute, the Wurkenko is (to some extent justifiably, given its great size and proportionately high needs for sustenance) a very greedy beast whose thriving presence in an area can end up posing a threat to other, competing smaller local life-forms all the same, namely by monopolizing the territory and resources of a local area as mentioned above.
As far as physical attributes go, Wurkenkos bear thick and heavy hair, most of it greenish in coloration, upon the majority of their bodies' surfaces, but unlike most other prominently hairy organisms, they ultimately do not rely on it for any sort of major protection, having consistently tough and strong leathery skin that would be more-than-sufficient for them to withstand any and all harsh elements occurring in their natural habitats even if they were completely bald. Of particular visual strikingness, albeit equally-superfluous in practice, are the deep-blue tufts of extra-coarse fur that cover the dorsal surfaces of the Wurkenko's forearms, from the elbows to the knuckles of its four-fingered paws; if anything, this feature could be considered to serve as an aesthetic "accentuation" of sorts to the gangly-armed beast's punching ability, which is indeed massively powerful and its primary asset in terms of attacking. Easily the Wurkenko form's most distinctive feature of all, though, is what Kierraplips and other humanoid witnesses to the animal have popularly labelled as its "crown", consisting of six tall, straight-standing and nigh-unbreakably sturdy horns surrounding a large fleshy "bump" in encircling formation upon the otherwise-flat top-surface of its noggin. This is seen, as one might already guess based on the aforementioned "crown" terminology alone, to physically symbolize the Wurkenko's dominant role as "king" of Barserinv's wilds.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
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Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.
Spaceflight (or space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.
Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.
A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft – both when unpropelled and when under propulsion – is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.
History
Main articles: History of spaceflight and Timeline of spaceflight
Tsiolkovsky, early space theorist
The first theoretical proposal of space travel using rockets was published by Scottish astronomer and mathematician William Leitch, in an 1861 essay "A Journey Through Space".[1] More well-known (though not widely outside Russia) is Konstantin Tsiolkovsky's work, "Исследование мировых пространств реактивными приборами" (The Exploration of Cosmic Space by Means of Reaction Devices), published in 1903.
Spaceflight became an engineering possibility with the work of Robert H. Goddard's publication in 1919 of his paper A Method of Reaching Extreme Altitudes. His application of the de Laval nozzle to liquid fuel rockets improved efficiency enough for interplanetary travel to become possible. He also proved in the laboratory that rockets would work in the vacuum of space;[specify] nonetheless, his work was not taken seriously by the public. His attempt to secure an Army contract for a rocket-propelled weapon in the first World War was defeated by the November 11, 1918 armistice with Germany. Working with private financial support, he was the first to launch a liquid-fueled rocket in 1926. Goddard's paper was highly influential on Hermann Oberth, who in turn influenced Wernher von Braun. Von Braun became the first to produce modern rockets as guided weapons, employed by Adolf Hitler. Von Braun's V-2 was the first rocket to reach space, at an altitude of 189 kilometers (102 nautical miles) on a June 1944 test flight.[2]
Tsiolkovsky's rocketry work was not fully appreciated in his lifetime, but he influenced Sergey Korolev, who became the Soviet Union's chief rocket designer under Joseph Stalin, to develop intercontinental ballistic missiles to carry nuclear weapons as a counter measure to United States bomber planes. Derivatives of Korolev's R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite, Sputnik 1, on October 4, 1957, and later the first human to orbit the Earth, Yuri Gagarin in Vostok 1, on April 12, 1961.[3]
At the end of World War II, von Braun and most of his rocket team surrendered to the United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency. This work on missiles such as Juno I and Atlas enabled launch of the first US satellite Explorer 1 on February 1, 1958, and the first American in orbit, John Glenn in Friendship 7 on February 20, 1962. As director of the Marshall Space Flight Center, Von Braun oversaw development of a larger class of rocket called Saturn, which allowed the US to send the first two humans, Neil Armstrong and Buzz Aldrin, to the Moon and back on Apollo 11 in July 1969. Over the same period, the Soviet Union secretly tried but failed to develop the N1 rocket to give them the capability to land one person on the Moon.
Phases
Launch
Main article: Rocket launch
See also: List of space launch system designs
Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from a spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches, and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities.
A launch is often restricted to certain launch windows. These windows depend upon the position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth itself. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit.
A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of a launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh many hundreds of tonnes. The Space Shuttle Columbia, on STS-1, weighed 2,030 tonnes (4,480,000 lb) at take off.
Reaching space
The most commonly used definition of outer space is everything beyond the Kármán line, which is 100 kilometers (62 mi) above the Earth's surface. The United States sometimes defines outer space as everything beyond 50 miles (80 km) in altitude.
Rockets are the only currently practical means of reaching space. Conventional airplane engines cannot reach space due to the lack of oxygen. Rocket engines expel propellant to provide forward thrust that generates enough delta-v (change in velocity) to reach orbit.
For manned launch systems launch escape systems are frequently fitted to allow astronauts to escape in the case of emergency.
Alternatives
Main article: Non-rocket spacelaunch
Many ways to reach space other than rockets have been proposed. Ideas such as the space elevator, and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo.
Leaving orbit
This section possibly contains original research. Relevant discussion may be found on Talk:Spaceflight. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. (June 2018) (Learn how and when to remove this template message)
Main articles: Escape velocity and Parking orbit
Launched in 1959, Luna 1 was the first known man-made object to achieve escape velocity from the Earth.[4] (replica pictured)
Achieving a closed orbit is not essential to lunar and interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. NASA considered launching Apollo missions directly into lunar trajectories but adopted the strategy of first entering a temporary parking orbit and then performing a separate burn several orbits later onto a lunar trajectory. This costs additional propellant because the parking orbit perigee must be high enough to prevent reentry while direct injection can have an arbitrarily low perigee because it will never be reached.
However, the parking orbit approach greatly simplified Apollo mission planning in several important ways. It substantially widened the allowable launch windows, increasing the chance of a successful launch despite minor technical problems during the countdown. The parking orbit was a stable "mission plateau" that gave the crew and controllers several hours to thoroughly check out the spacecraft after the stresses of launch before committing it to a long lunar flight; the crew could quickly return to Earth, if necessary, or an alternate Earth-orbital mission could be conducted. The parking orbit also enabled translunar trajectories that avoided the densest parts of the Van Allen radiation belts.
Apollo missions minimized the performance penalty of the parking orbit by keeping its altitude as low as possible. For example, Apollo 15 used an unusually low parking orbit (even for Apollo) of 92.5 nmi by 91.5 nmi (171 km by 169 km) where there was significant atmospheric drag. But it was partially overcome by continuous venting of hydrogen from the third stage of the Saturn V, and was in any event tolerable for the short stay.
Robotic missions do not require an abort capability or radiation minimization, and because modern launchers routinely meet "instantaneous" launch windows, space probes to the Moon and other planets generally use direct injection to maximize performance. Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory.
Note that the escape velocity from a celestial body decreases with altitude above that body. However, it is more fuel-efficient for a craft to burn its fuel as close to the ground as possible; see Oberth effect and reference.[5] This is another way to explain the performance penalty associated with establishing the safe perigee of a parking orbit.
Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Project Orion and Russia's Kliper/Parom tandem.
Astrodynamics
Main article: Orbital mechanics
Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits.
Non-rocket orbital propulsion methods include solar sails, magnetic sails, plasma-bubble magnetic systems, and using gravitational slingshot effects.
Ionized gas trail from Shuttle reentry
Recovery of Discoverer 14 return capsule by a C-119 airplane
Transfer energy
The term "transfer energy" means the total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft.[6][7]
Reentry
Main article: Atmospheric reentry
Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if the vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating. The theory behind reentry was developed by Harry Julian Allen. Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat that reaches the vehicle, and the remainder heats up the atmosphere.
Landing
The Mercury, Gemini, and Apollo capsules all splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. The Space Shuttle glided to a touchdown like a plane.
Recovery
After a successful landing the spacecraft, its occupants and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites.
Types
Uncrewed
See also: Uncrewed spacecraft and robotic spacecraft
Sojourner takes its Alpha particle X-ray spectrometer measurement of Yogi Rock on Mars
The MESSENGER spacecraft at Mercury (artist's interpretation)
Uncrewed spaceflight (or unmanned) is all spaceflight activity without a necessary human presence in space. This includes all space probes, satellites and robotic spacecraft and missions. Uncrewed spaceflight is the opposite of manned spaceflight, which is usually called human spaceflight. Subcategories of uncrewed spaceflight are "robotic spacecraft" (objects) and "robotic space missions" (activities). A robotic spacecraft is an uncrewed spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe.
Uncrewed space missions use remote-controlled spacecraft. The first uncrewed space mission was Sputnik I, launched October 4, 1957 to orbit the Earth. Space missions where other animals but no humans are on-board are considered uncrewed missions.
Benefits
Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit.
Telepresence
Telerobotics becomes telepresence when the time delay is short enough to permit control of the spacecraft in close to real time by humans. Even the two seconds light speed delay for the Moon is too far away for telepresence exploration from Earth. The L1 and L2 positions permit 400-millisecond round trip delays, which is just close enough for telepresence operation. Telepresence has also been suggested as a way to repair satellites in Earth orbit from Earth. The Exploration Telerobotics Symposium in 2012 explored this and other topics.[8]
Human
Main article: Human spaceflight
ISS crew member stores samples
The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of the USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles.[9] Currently, the only spacecraft regularly used for human spaceflight are the Russian Soyuz spacecraft and the Chinese Shenzhou spacecraft. The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted two human suborbital spaceflights.
Sub-orbital
Main article: Sub-orbital spaceflight
The International Space Station in Earth orbit after a visit from the crew of STS-119
On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch.
The most generally recognized boundary of space is the Kármán line 100 km above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 50 miles (80 km) above sea level.) It is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight.
Point-to-point
Point-to-point is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. Consider a conventional airline route between London and Sydney, a flight that normally lasts over twenty hours. With point-to-point suborbital travel the same route could be traversed in less than one hour.[10] While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using its BFR vehicle.[11] Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit.[12] If rockets are used, the size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmosphere re-entry that are nearly as large as those faced by orbital spaceflight.
Orbital
Main article: Orbital spaceflight
Apollo 6 heads into orbit
A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight, the tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit.
Interplanetary
Main article: Interplanetary spaceflight
Interplanetary travel is travel between planets within a single planetary system. In practice, the use of the term is confined to travel between the planets of our Solar System.
Interstellar
Main article: Interstellar travel
Five spacecraft are currently leaving the Solar System on escape trajectories, Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons. The one farthest from the Sun is Voyager 1, which is more than 100 AU distant and is moving at 3.6 AU per year.[13] In comparison, Proxima Centauri, the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach the nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation, as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require the use of some new, advanced method of propulsion.
Intergalactic
Main article: Intergalactic travel
Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction.
Spacecraft
Main article: Spacecraft
An Apollo Lunar Module on the lunar surface
Spacecraft are vehicles capable of controlling their trajectory through space.
The first 'true spacecraft' is sometimes said to be Apollo Lunar Module,[14] since this was the only manned vehicle to have been designed for, and operated only in space; and is notable for its non aerodynamic shape.
Propulsion
Main article: Spacecraft propulsion
Spacecraft today predominantly use rockets for propulsion, but other propulsion techniques such as ion drives are becoming more common, particularly for unmanned vehicles, and this can significantly reduce the vehicle's mass and increase its delta-v.
Launch systems
Main article: Launch vehicle
Launch systems are used to carry a payload from Earth's surface into outer space.
Expendable
Main article: Expendable launch system
Most current spaceflight uses multi-stage expendable launch systems to reach space.
Reusable
Main article: Reusable launch system
Ambox current red.svg
This section needs to be updated. Please update this article to reflect recent events or newly available information. (August 2019)
The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger, which was lost in January 1986. The Columbia broke up during reentry in February 2003.
The Space Shuttle Columbia seconds after engine ignition on mission STS-1
Columbia landing, concluding the STS-1 mission
Columbia launches again on STS-2
The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the US Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.
Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2021. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.
Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company has built its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic planned to begin reusable private spaceflight carrying paying passengers (space tourists) in 2008, but this was delayed due to an accident in the propulsion development.[15]
Challenges
Main article: Effect of spaceflight on the human body
Space disasters
Main article: Space accidents and incidents
All launch vehicles contain a huge amount of energy that is needed for some part of it to reach orbit. There is therefore some risk that this energy can be released prematurely and suddenly, with significant effects. When a Delta II rocket exploded 13 seconds after launch on January 17, 1997, there were reports of store windows 10 miles (16 km) away being broken by the blast.[16]
Space is a fairly predictable environment, but there are still risks of accidental depressurization and the potential failure of equipment, some of which may be very newly developed.
In 2004 the International Association for the Advancement of Space Safety was established in the Netherlands to further international cooperation and scientific advancement in space systems safety.[17]
Weightlessness
Main article: Weightlessness
Astronauts on the ISS in weightless conditions. Michael Foale can be seen exercising in the foreground.
In a microgravity environment such as that provided by a spacecraft in orbit around the Earth, humans experience a sense of "weightlessness." Short-term exposure to microgravity causes space adaptation syndrome, a self-limiting nausea caused by derangement of the vestibular system. Long-term exposure causes multiple health issues. The most significant is bone loss, some of which is permanent, but microgravity also leads to significant deconditioning of muscular and cardiovascular tissues.
Radiation
Once above the atmosphere, radiation due to the Van Allen belts, solar radiation and cosmic radiation issues occur and increase. Further away from the Earth, solar flares can give a fatal radiation dose in minutes, and the health threat from cosmic radiation significantly increases the chances of cancer over a decade exposure or more.[18]
Life support
Main article: Life support system
In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[19] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.
Space weather
Main article: Space weather
Aurora australis and Discovery, May 1991.
Space weather is the concept of changing environmental conditions in outer space. It is distinct from the concept of weather within a planetary atmosphere, and deals with phenomena involving ambient plasma, magnetic fields, radiation and other matter in space (generally close to Earth but also in interplanetary, and occasionally interstellar medium). "Space weather describes the conditions in space that affect Earth and its technological systems. Our space weather is a consequence of the behavior of the Sun, the nature of Earth's magnetic field, and our location in the Solar System."[20]
Space weather exerts a profound influence in several areas related to space exploration and development. Changing geomagnetic conditions can induce changes in atmospheric density causing the rapid degradation of spacecraft altitude in Low Earth orbit. Geomagnetic storms due to increased solar activity can potentially blind sensors aboard spacecraft, or interfere with on-board electronics. An understanding of space environmental conditions is also important in designing shielding and life support systems for manned spacecraft.
Environmental considerations
Rockets as a class are not inherently grossly polluting. However, some rockets use toxic propellants, and most vehicles use propellants that are not carbon neutral. Many solid rockets have chlorine in the form of perchlorate or other chemicals, and this can cause temporary local holes in the ozone layer. Re-entering spacecraft generate nitrates which also can temporarily impact the ozone layer. Most rockets are made of metals that can have an environmental impact during their construction.
In addition to the atmospheric effects there are effects on the near-Earth space environment. There is the possibility that orbit could become inaccessible for generations due to exponentially increasing space debris caused by spalling of satellites and vehicles (Kessler syndrome). Many launched vehicles today are therefore designed to be re-entered after use.