What sort energy propels the non-artificial satellites?
Once you are moving in space, you don’t need any energy to move further in a straight line at the same velocity. At least as long as the space is about void of any matter which could slow you. For a natural satellite, this straight line movement is modified through the presence of the main celestial body, so it is gravitation that makes it orbit that central body. “In space everything is in an orbit around some massive object. They maintain orbit because of the force of gravity between them.
