Orbital mechanics is the physics of motion in gravitational fields. Founded by Johannes Kepler (1609–1619) who discovered the three laws of planetary motion, and formalized by Isaac Newton (1687) who showed that gravity's inverse-square law explains all orbits, it is the science that makes space travel possible.
Every spacecraft trajectory — from Apollo's lunar transfers to Voyager's Grand Tour of the outer planets — is computed using these principles. Hohmann transfers provide the most fuel-efficient way to move between orbits. Lagrange points are gravitational sweet spots where spacecraft can park with minimal fuel. Gravity assists use a planet's motion to boost a spacecraft's velocity for free.
These simulations let you design orbital maneuvers: draw Kepler orbits with different eccentricities, plan Hohmann transfer burns, find the five Lagrange points, and see how gravity assists bend trajectories to reach the outer solar system.