Fly-By-Wire System

Hey all

I'm currently trying to make a space flight sim. One thing I'm particularly keen on is a fly-by-wire system, where thrusters rotate and adjust power levels to achieve velocities and rotations specified. I can't seem to find anything on the subject though that provides me with some nice maths on how to work it out.

In this example I have a small shuttle with 4 thrusters (shown below). Each thruster can be rotated in the x-axis and their power level varied. At the moment I'm unable to even get the thing hovering stably let alone flying. Of course I'd love a general solution but I don't think one really exists. How might I go about getting this little guy flying nicely?