Orbital Mechanics is a study of the motions of celestial bodies such as moons and planets as well as rockets, spacecrafts, satellites and other artificial bodies. It also studies how gravity, drag, thrust and etc affects space vehicles. Basically it is based on Newton Laws of motion and his laws of universal gravitation and Kepler's laws of planetary motion.
The engineering application for this field includes lunar and interplanetary trajectories, reentry and landing, rendezvous computations, trajectories, orbital maneuver and more. (Credit:www.braeunig.us)