Orbital mechanics, also called flight mechanics, is the study of the motions of artificial satellites and space vehicles moving under the influence of forces such as gravity, atmospheric drag, thrust, and so on. It is a modern spin-off of celestial mechanics, or the study of the motions of planetary and celestial bodies. One of the main scientists who built the foundations of orbital mechanics was mathematician Isaac Newton (1642–1727), who put forth his laws of motion and formulated the law of universal gravitation. (For more about Newton, see “History of Mathematics” and “Mathematical Analysis”; for more about Newton’s laws, see “Mathematics in the Physical Sciences.”) Today’s aerospace engineers apply orbital mechanics to such problems as rocket and spacecraft trajectories, reentry and landing of space vehicles, rendezvous computations (such spacecraft to the International Space Station), and lunar and interplanetary trajectories for unmanned vehicles.

Without knowing the mathematics involved in orbital mechanics, the International Space Station would plunge back into the Earth instead of circling it in a stable orbit.