What kind of space game?
If its an FPS:
Certainly Cartography Shop can do it - but there are pros and cons to using it. (Pros: Nice effects from lightmapping, easy to use, existing code about to help you use - cons: VERY poor after-sales support, limited functionality). Personally speaking I really like it and I like the end results I get from it but I had to devote a lot of time to working out how to get the most from it (with virtually no help avaliable) and there are lots of good level designer progs for use with DB/DBP so try them all and decide which you like best.
Another option is to make your own designer for the levels and this is a route many good games in production in DB have taken.
If its a space ship sim:
If I was doing this sort of game I would certainly design my own editor as none of the editors I've seen are really designed for making the sort of levels you'd make for it.
I guess what I'm really saying is that its ultimately up to you to find out which method suits you and the way you work best, which is a bit of a cop out for an answer and I'm sorry about that.
