What are some free to play 4X/space flight simulator games?

[Boo8er]

I would like to know, what are some good cool free to play 4X games or space flight simulator games? 4X games are like: Master of Orion, Galactic Civilizations II, Civilizations, etc. Space flight simulators are like: Freelancer, X3, Freespace, etc.

[GloatingSwine]

Star Conflict is a free to play space game.

It's basically War Thunder in space.

IIRC it's getting free roam of some sort reasonably soon (otherwise it's matchmade PvP/PvE).