See the new Space Add-On for FS2004!!
Nah, just kiddin, its a stand-alone freeware program and although I have only had a quick look, it seems to be pretty neat!! Its very complex as its goes deeply into astronautics, physics and mathamatical formulae that I wont even pretend to understand, (Adlabs will love it!!

) I just flew a quick approach to CC and the Shuttle has the decent rate of a brick!!

Great fun though
Get it here if you want it:
http://www.medphys.ucl.ac.uk/~martins/orbit/orbit.html