Does it, though? I mean, I've played KSP, I know the rocket equation. But with a space gun, your vehicle only winds up moving as fast as the propellant pushin

Does it, though? I mean, I've played KSP, I know the rocket equation. But with a space gun, your vehicle only winds up moving as fast as the propellant pushing it out- so that mass of fuel (more explosive than fuel, I guess) still has to be accelerated to near-orbital speeds in order for the gun to work.