It's Minecraft in space.
Wait no it's not, it just looks like that. A sandbox builder/shooter in space, fun game mechanics, the ability to build a huge fleet or maybe just a gigantic destroyer, space stations etc.
http://star-made.org/

Download this, it's free as it's alpha!
If you're already playing, post pics of your stuff so far!

(Someone with a good comp and net should make a server for us)