system
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human
Rail gun technology for space travel...

Not to get *into* space. But would it be possible to utilize rail gun technology *in* space? 

Say we had a large system orbiting the planet a la ISS. Would it:

a) be possible to use the technology to "fire" landers/orbiters towards other planets/moons? Manned crafts?

b) if it is possible, would there be any benefit over current methods, namely fuel needed to achieve proper velocity vs energy used for the initial "firing" to create momentum and velocity.
gpt
Would it be possible to? Sure. Not with the current ISS, though. The issue is Newton's third law: it takes a lot of energy to get something to the Moon, and the launch platform is going to lose that much energy in the process (because of the way orbits work, you can't fire it so that the ISS would gain energy, either). That means the ISS as is would end up being de-orbited in the process, or nearly so. In any case, you'd still have to end up spending the fuel anyways to put your launcher back into the correct orbit.

There are two possible alternatives. The first is that you fire with so much force, it puts you into orbit going the opposite way. That would require phenomenal amounts of energy (the delta-v of the launcher would be ~14km/s, so impossible with current technology), or by using a launch platform heavy enough to not be effected much by the reactive force. That would mean we could amortize the cost of the launch over a longer period of time, using ion or plasma engines to regain the orbital energy the launcher looses, which are much much more efficient than rocket engines. That could give us significant fuel cost gains (in theory anyways).

Keep in mind the acceleration involved would be high, again unless you had a really big gun, so whether you could do manned launches would depend on how big a gun you built. The technology isn't there yet.

Note that on the Moon, things are completely different. Rail launchers from the Moon are definitely possible and in fact will probably be a key piece of long-term expansion into the solar system. But that's a few decades away yet.