a08_r_c_o_TPMBK (S69-15560)
A rarely seen/published Apollo 8 image, capturing the moment of ignition - immediately before achieving full thrust - of its five Rocketdyne F-1 engines, marking the start of the historic mission, December 21, 1968.
I believe that's the jettisoned Q-ball cover immediately to the left and a little below the apex of the Launch Escape Tower/Launch Escape System. Too too cool:
apollo11space.com/how-does-the-q-ball-cover-retraction-sy...
Credit: "APOLLO 11 SPACE" website
www.collectspace.com/ubb/Forum29/HTML/000928.html
Credit: collectSPACE website
www.facebook.com/share/p/yxNZUShc4FeCvbaF/?mibextid=K35XfP
The “coolness” of the image led me to further research the engineering genius that made it possible. And the following pertains ONLY to the START-UP of the F-1 engines - which is what’s happening here, like super-duper fast!!!
Mind-boggling. Keeping in mind, this is 1968:
First, for those technically inclined, the following excerpt:
“The mechanical aspects of the Rocketdyne F-1 ignition sequence are mindboggling by themselves. In any large liquid-fueled rocket engine, a lot of massive parts have to be brought up to speed in a very short amount of time. The turbopumps in the F-1 are massive. Here's a cutaway: twicsy.com/i/hveRmc
One propellant line would be bolted to the top of the case. The cylinder in the center is the shaft. At the top of the shaft, you see the low-pressure pump, which feeds into the top of the impeller for the high-pressure pump. Its discharge flange is barely visible on the right. Beneath that is the other propellant's high-pressure impeller, arranged upside down relative to the first. Beneath that the "spiky" cutaway versions of its low-pressure pump. The intake flanges form the prominent "flank" of this assembly, and its discharge flange is also barely visible. Finally at the bottom is the toroidal combustion chamber for the gas generator and (at the very bottom) the drive turbine.
That's several hundred pounds of hardened steel and titanium that has to be brought up to minimal operating speed in just a few seconds. The "starter motor" (actually akin to how jet engines are started with compressed air blown into the compressor) gets that assembly to a barely serviceable speed -- a mere fraction of its operating speed and pressure, but just enough to get the propellants flowing.
Now we discovered through experience that you get smoother starts if you first inject oxidizer (liquid oxygen in this case) and then fuel, then spark the igniter. You see this in the slow-motion ignition videos as a cascade of white vapor. This, combined with the relatively low flow rate of propellants during the ignition transient, means a fairly non-propulsive, multi-directional conflagration first occurs (i.e., an ordinary fireball). As the gas-generator achieves a more self-sustaining operation and the engine builds thrust (and thus the plume becomes more unidirectional and propulsive), it entrains the air surrounding it by means of Bernoulli's principle.
As you may know, the simple explanation of Bernoulli's principle is that unidirectional fluid flow produces a zone of low static pressure around the flow column. The plume is moving downward only, therefore exerts no static pressure on the air around it. The air around it, however, is in a non-flowing state and hence has considerable static pressure (sea level normal). So, this creates the tendency for air (and the largely non-flowing fireball it now contains, due to effluence from the startup) to get sucked sideways into the plume and (obviously) start moving rapidly downward with it.
But this is not a finely demarcated effect. It is spread out over the several lateral feet of air (and fireball) near the plume, which means that the trend is for the static air (and fireball) pressure to decrease as one approaches the plume, and the entrainment flow therefore also to increase over those same few feet. Eventually (air being elastic), the effect diminishes as one gets far enough away from the plume.”
From/at:
forum.cosmoquest.org/forum/science-and-space/space-explor...
Credit: CosmoQuest Forum website
And, for the rest of us, the following is a MUST watch, seriously.
AGAIN, THIS IS FROM 1968.
THINK ABOUT IT:
Credit: Scott Manley/YouTube
Which is embedded here:
space.stackexchange.com/questions/26183/why-does-air-get-...
Credit: Space Exploration Stack Exchange website
a08_r_c_o_TPMBK (S69-15560)
A rarely seen/published Apollo 8 image, capturing the moment of ignition - immediately before achieving full thrust - of its five Rocketdyne F-1 engines, marking the start of the historic mission, December 21, 1968.
I believe that's the jettisoned Q-ball cover immediately to the left and a little below the apex of the Launch Escape Tower/Launch Escape System. Too too cool:
apollo11space.com/how-does-the-q-ball-cover-retraction-sy...
Credit: "APOLLO 11 SPACE" website
www.collectspace.com/ubb/Forum29/HTML/000928.html
Credit: collectSPACE website
www.facebook.com/share/p/yxNZUShc4FeCvbaF/?mibextid=K35XfP
The “coolness” of the image led me to further research the engineering genius that made it possible. And the following pertains ONLY to the START-UP of the F-1 engines - which is what’s happening here, like super-duper fast!!!
Mind-boggling. Keeping in mind, this is 1968:
First, for those technically inclined, the following excerpt:
“The mechanical aspects of the Rocketdyne F-1 ignition sequence are mindboggling by themselves. In any large liquid-fueled rocket engine, a lot of massive parts have to be brought up to speed in a very short amount of time. The turbopumps in the F-1 are massive. Here's a cutaway: twicsy.com/i/hveRmc
One propellant line would be bolted to the top of the case. The cylinder in the center is the shaft. At the top of the shaft, you see the low-pressure pump, which feeds into the top of the impeller for the high-pressure pump. Its discharge flange is barely visible on the right. Beneath that is the other propellant's high-pressure impeller, arranged upside down relative to the first. Beneath that the "spiky" cutaway versions of its low-pressure pump. The intake flanges form the prominent "flank" of this assembly, and its discharge flange is also barely visible. Finally at the bottom is the toroidal combustion chamber for the gas generator and (at the very bottom) the drive turbine.
That's several hundred pounds of hardened steel and titanium that has to be brought up to minimal operating speed in just a few seconds. The "starter motor" (actually akin to how jet engines are started with compressed air blown into the compressor) gets that assembly to a barely serviceable speed -- a mere fraction of its operating speed and pressure, but just enough to get the propellants flowing.
Now we discovered through experience that you get smoother starts if you first inject oxidizer (liquid oxygen in this case) and then fuel, then spark the igniter. You see this in the slow-motion ignition videos as a cascade of white vapor. This, combined with the relatively low flow rate of propellants during the ignition transient, means a fairly non-propulsive, multi-directional conflagration first occurs (i.e., an ordinary fireball). As the gas-generator achieves a more self-sustaining operation and the engine builds thrust (and thus the plume becomes more unidirectional and propulsive), it entrains the air surrounding it by means of Bernoulli's principle.
As you may know, the simple explanation of Bernoulli's principle is that unidirectional fluid flow produces a zone of low static pressure around the flow column. The plume is moving downward only, therefore exerts no static pressure on the air around it. The air around it, however, is in a non-flowing state and hence has considerable static pressure (sea level normal). So, this creates the tendency for air (and the largely non-flowing fireball it now contains, due to effluence from the startup) to get sucked sideways into the plume and (obviously) start moving rapidly downward with it.
But this is not a finely demarcated effect. It is spread out over the several lateral feet of air (and fireball) near the plume, which means that the trend is for the static air (and fireball) pressure to decrease as one approaches the plume, and the entrainment flow therefore also to increase over those same few feet. Eventually (air being elastic), the effect diminishes as one gets far enough away from the plume.”
From/at:
forum.cosmoquest.org/forum/science-and-space/space-explor...
Credit: CosmoQuest Forum website
And, for the rest of us, the following is a MUST watch, seriously.
AGAIN, THIS IS FROM 1968.
THINK ABOUT IT:
Credit: Scott Manley/YouTube
Which is embedded here:
space.stackexchange.com/questions/26183/why-does-air-get-...
Credit: Space Exploration Stack Exchange website