Play kerbal space program? lol
Best space simulation i know off, you can also mod and stuffs, i made new planets, a hyper drive, etc.
Near-infinite posiblities ;D
And it is in development, so it's still fully active.
It have ships that you can make yourself part by part, launch them on a launch pad on the planet, and get to pace, shoot a kerbal (character in the vessel) for fun in the space... Yet very fun.
Eventually you can mod your own parts or download plugins for the game.
At this moment the game is only single player (even if there are 2 multiplayer plugins made by the community), and they are working on that for the next version.
417 parts, custom parts, etc.
It can be fun at somne times, and you can even smash your keyboard because your "supposed-to-work-plane-design" fails to lift off.
Oh yea, vessels, and planes too ;D
Well have fun searching more infos lol
(And btw my ship is not really a "good" example on how to build ships xD)