A while back someone posted a link to a planetary simulator of sorts which seemed quite simple to use. However, I've got NO idea where that thread is, and the current Google internal search is... deplorable to say the least.
However - what we're doing is trying to produce logical or realistic solar systems about given stars - the primary seach tool for those stars is of course Celestia...
Thusly, what the Stellar Assault team needs is a sim that can allow us to take the known data about a star system and be able to throw some planets about it, etc., etc.
If anyone can help with this, please do so. Also, move this thread if necessary.