VoidExpanse is finally in Steam "coming soon" section. You cannot purchase the game yet, as there are a few things we would like to finish before we officially release the game, but it's coming, and very soon! :)
If you'd like to learn more about the game you can visit the official website at http://voidexpanse.com/
Also, if you'd like to grab the current version of the game right now you can head over to https://atomictorch.com/ and to our Store there.