The maker (there is only one guy) of Space Engine is going to add space vehicles in the next update it seems. No land vehicles for now. It does preternaturally make all of the planets. It's super cool to explore space. You can find some amazing things in it. It makes the universe feel giant. Like I said though, it has no trees, doesn't look good up close, water sucks, and it crashes a decent amount (though so does Outerra for me on my 2xx series cards...).
They both have their advantages. It would be amazing if we could combine them.