The Science Behind Building a Space Gun

An anonymous reader writes "Astronomer and gamer Scott Manley (more famous for his Kerbal Space program coverage) has created a fantastic video explaining the science behind building guns that could one day be used to launch payloads into space. It's not as easy as simply making a bigger gun, there's a whole host of unorthodox 'gun' designs which work around the limitations of garden variety propellants."

Re:I think it's called a mass driver

[roc97007]

Some of the techniques resemble a mass driver, but many do not. It's actually an interesting video.

Re:Scaled Down Particle Accelerator

[Anonymous Coward]

Why not scale down the LHC and build something that is capable of accelerating something relatively small say 10-100kg fast enough to make it to orbit instead of accelerating atoms to nearly the speed of light.

Accelerating charged particles and accelerating something more complex, like a 10kg payload, are in a completely different ballpark, unless you're happy with send particles into orbit.

Also, each of the protons in the LHC's beam have about as much energy as a fast baseball.

Re:Inexpensive way to send up inert objects

[currently_awake]

Reusable rockets must be fully overhauled after every single flight and must be more rugged to survive repeated use, they therefore cost more than a disposable rocket. The Saturn 5 was much cheaper than the space shuttle. Using chemical fuels means 95% of the rocket must be fuel. To get usable launch weights you have to use every trick in the book to save weight. All those weight savings make rockets fragile, they wear out quickly and need everything rebuilt after each flight. The only way to make space cheap is by having the power source separate from the rocket/payload (gun, mass driver, loop, skyhook, tractor beam).

Re:Scaled Down Particle Accelerator

[Grayhand]

It's the g-force involved. The benefit of a long barrel is lower g-forces. A short barrel would be possible but when you start talking a million Gs the only thing that could survive would be solid metals. It's a balancing act of barrel length as opposed to G-Forces involved. There's nothing special about how the LHC is built, magnets or explosives it's still converting energy into motion. Most gun launch systems plan on using explosives to cut costs. Explosives are cheap, magnets and electricity are expensive. If you could do it efficiently one gallon of gasoline would orbit a couple of kilos. The trick is not wasting the energy. As the projectile moves down the barrel the gas expands exhausting it's energy. Say you have a mile long barrel you'd likely run out of gas expansion before you reached the end then add in friction and a projectile that could reach orbit doesn't even make it a mile. Instead burn a cup of vaporized gasoline spaced out every ten feet along the barrel and you might need a few hundred gallons of gas to reach orbit but it's still dirt cheap. Watch the video and he explains why that wouldn't work either. The real solution is lower density gases like hydrogen that have a higher Mach speed. The best bet is watch the video. It's one of the best I've ever seen and explains the problems in laymen's terms.