[js1138]

For your amusement.

http://scienceworld.wolfram.com/physics/HohmannTransferOrbit.html

I had a lunar lander game for my Trash-80 that used this equation to tell you how you were doing with your burn times and fuel. You could play with parameters before committing to a burn, but the game continued in real time, so the time you spent testing your estimates also changed the situation.

[Thatcherite]

Well, there is the rocket science almost done. Of course rocket engineering is much tougher .