Pioneer is a pretty sweet space game if you like exploring thousands of solar systems and with there own planets/moons http://pioneerspacesim.net/ its still in alpha quote from homepage Pioneer is a space adventure game set in the milkyway galaxy at the turn of the 31st century. The game is open-ended, and you are free to explore the millions of star systems in the game. You can land on planets, slingshot past gas giants, and burn yourself to a crisp flying between binary star systems. When Pioneer is finished there will be many ways to make ends meet: piracy, smuggling, bounty-hunting, mining, doing missions for the various factions fighting for power, freedom or self-determination