I'm not a physicist, but I am an engineer interested in things like this. I've wondered this kind of question too.

After a bit of online research, I think I understand it well enough to explain it. Since DaFranker, EY, and shiminux all seem to know, I'd like to run this by you and get your edits.

Question: "Where the frak does gravity get its power source?" Answer: "It's not really a source like a battery or a motor. What you're seeing is the changing of energy from one kind to another. The fact that masses curve space creates a way for the positions of potential energy to be changed into the motions of kinetic energy. Since it's not a dissipative force like friction there's no need to keep "pushing power into the system" like with a car's motor or an airplane's jet. Just like a spacecraft only needs to fire rockets at the beginning and the end to change direction and doesn't need to keep engines going all the time to stay moving. Oh, wait, you weren't talking about the equations of power, right? If that was it I'll need to go read up some more." <grin>

Upvotes! I've had the space travel and the gravity pieces of the puzzle for a long time. A special thanks to shminux for mentioning potential and disipative forces. That's how I was prompted to come to an answer.

Also, this really seems like a question that needs to be dissolved. I think it's based on a misunderstanding and not a real problem. That may be why professors have a hard time explaining it - there isn't a power source for gravity in the sense that was being asked.