BRB, building one in Kerbal Space Program. :)
I've occasionally considered writing something with a better aerodynamics sim in ...
Ferram Aerospace[1] adds much more realistic aerodynamics and TAC fuel balancer[2] adds a fuel balancer.
[1] http://forum.kerbalspaceprogram.com/threads/20451-0-22-Ferra...
[2] http://forum.kerbalspaceprogram.com/threads/25823-0-23-TAC-F...