Knowra Orbital mechanics Orbital mechanics Orbital mechanics describes and predicts the motion of objects under gravity, especially spacecraft and celestial bodies. It includes calculating trajectories and planning maneuvers that change them.
Two-body problem : The idealized motion of two bodies interacting only through their mutual gravitational attraction. Its exact solutions provide the basic model for most introductory orbit calculations.
Hohmann transfer orbit : A two-impulse transfer between circular coplanar orbits using half of an elliptical orbit. It is a fuel-efficient baseline for changing a spacecraft's orbital altitude.
Newton's law of universal gravitation : The law stating that every pair of masses attracts with a force proportional to their masses and inversely proportional to distance squared. It supplies the gravitational force used to derive ideal orbital motion.
Astrodynamics : The applied study of spacecraft motion, trajectories, and navigation. It often emphasizes mission design and control where orbital mechanics names the broader mathematical subject.
Kepler's laws of planetary motion : Three mathematical rules describing how planets move in elliptical orbits around the Sun. They summarize the geometry and timing of ideal gravitational orbits.
Bi-elliptic transfer : An orbital transfer using three impulses and an intermediate orbit with a very large apoapsis. For sufficiently large radius changes, it can use less fuel than a Hohmann transfer.
Conservation of energy : The principle that total energy remains constant in an isolated system. Specific orbital energy distinguishes bound ellipses from parabolic and hyperbolic paths.
Celestial mechanics : The study of the motions of natural celestial bodies under gravity. It overlaps strongly but usually centers planets, moons, stars, and their long-term dynamics.
Orbital elements : A set of parameters specifying the size, shape, orientation, and position of an orbit. These parameters turn a trajectory into a compact, calculable description.
Gravity assist : A spacecraft trajectory change that exchanges energy and momentum with a moving celestial body. Planetary flybys can redirect spacecraft and change their heliocentric speed without propellant.
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