Kerbal Space Program
I've been playing this game for a while.
It allows you to assemble all kinds of parts and sometimes it works out. sometimes things go crashing down. you can't loose you just revert back and fix it in the hanger. they have missions to accomplish that are built in as well, all good fun, if you ask me
the mod's I use depend on the version of the game, there have been many upgrade and no matter what version you like(for me, I'm on the latest 1.4.5) the mods have to be compatible to work right.
I test my mods prior to going all in, on a new mission and sometimes I get to migrate a ship or 2 into the new save.
I would be glad to advise you on "the how to's" as it is an attempt at realism and this can be a challenge.
let me know 'Jammer
see more photo's here a sample: