Super Sonic
This is one of those pictures that I absolutely love but won't appeal to most people because it's so nerdy.
In brief it's picture of a pellet that is going about twice the speed of sound. My pellet rifle will go close to the speed of sound with a super light pellet. The trick is that the gas that the pellet is going through is very dense and the speed of sound in that gas is half the speed of sound in air. The idea for this came from one of my smart co-workers, Andy.
I spent way more time on this than the picture warrants. But I had fun figuring things out. The first job was to find a supply of very dense gas. Sulfur hexaflouride was the first thought but I didn't want to buy a bottle of the stuff. Then I remembered a vintage can of Freon that I saved from the trash. It turns out that the average Freon has really high density. The average speed of sound is about half that of air. Perfect.
The next job was building a container to hold the gas that had high quality glass sides. A square plastic bottle with rectangular holes worked well. I sealed the glass with some silicone seal and cut two round holes on the other two sides to let the pellet through. This round holes were sealed with packing tape.
The only other big job was building a sturdy support to hold the pellet rifle and sensor. I got everything running last night so I set-up for the actual shot this morning.
I warmed up by setting up some Halloween decorations, gotta get ready for the sucrose hungry hordes.
The amazing thing was that after I filled up the container with Freon and fired the first pellet, this is what I got. Pretty much everything I wanted. If you look closely, behind the surpersonic shock wave, you can see faint shock waves that curve slightly. These are the near supersonic waves in air. The contrast between the two gases is obvious.
I'm very happy with this picture. Thanks Andy for the great idea.
Cheers.
Super Sonic
This is one of those pictures that I absolutely love but won't appeal to most people because it's so nerdy.
In brief it's picture of a pellet that is going about twice the speed of sound. My pellet rifle will go close to the speed of sound with a super light pellet. The trick is that the gas that the pellet is going through is very dense and the speed of sound in that gas is half the speed of sound in air. The idea for this came from one of my smart co-workers, Andy.
I spent way more time on this than the picture warrants. But I had fun figuring things out. The first job was to find a supply of very dense gas. Sulfur hexaflouride was the first thought but I didn't want to buy a bottle of the stuff. Then I remembered a vintage can of Freon that I saved from the trash. It turns out that the average Freon has really high density. The average speed of sound is about half that of air. Perfect.
The next job was building a container to hold the gas that had high quality glass sides. A square plastic bottle with rectangular holes worked well. I sealed the glass with some silicone seal and cut two round holes on the other two sides to let the pellet through. This round holes were sealed with packing tape.
The only other big job was building a sturdy support to hold the pellet rifle and sensor. I got everything running last night so I set-up for the actual shot this morning.
I warmed up by setting up some Halloween decorations, gotta get ready for the sucrose hungry hordes.
The amazing thing was that after I filled up the container with Freon and fired the first pellet, this is what I got. Pretty much everything I wanted. If you look closely, behind the surpersonic shock wave, you can see faint shock waves that curve slightly. These are the near supersonic waves in air. The contrast between the two gases is obvious.
I'm very happy with this picture. Thanks Andy for the great idea.
Cheers.