I have been playing Kerbal Space Program for years. I always say that I don’t like recommending things that I haven’t used myself. I have over 100 hours invested in the Kerbal Space Program, and I know that I’ve only scratched the surface.
The base game is currently on sale at the Humble Store for $8.99 (78% off). It runs on Windows, Mac, and Linux–it has had good Linux support for a very long time!
Not only that, but the Making History expansion is on sale for $6.74 (55% off). This is the part that drew my attention. I’ve been away from KSP for a while, and I don’t even have the expansion pack. I just corrected that problem, and I believe you should as well!
NOTE: The deal has expired, but Kerbal Space Program is still a fantastic game at any price!