Good game, needs polish
First, change the gun so as to be effective; say, like the enemy guns...at the moment we're comparing muskets to M-14s in effectiveness.
Also, either go all the way with the slide (no air, no friction; we're in space) or remove it; as it is, turning the ship and firing the engine results in an instant reversal of direction, however if reality were in place, this would be the equivalent of sticking and engine on each side of the space-craft and firing both at the same time.
This is a great, if slightly underrated, game that comes close to simulating reality; close enough that people expect reality, but far enough away that they are disapointed. To improve it to a great game (no longer mediocre) either move it closer to reality, or move it away from reality, I would be overjoyed to see a sequel to this game.