Orbitalmekanik

Orbitalmekanik, or orbital mechanics, is the branch of celestial mechanics that studies the motion of bodies under gravitational forces, particularly artificial satellites and spacecraft relative to planets and the Sun. It combines Newton's law of gravitation with kinematic relations to predict trajectories, design transfers, and assess stability.

Central to orbital mechanics is the two-body problem, which has closed-form solutions described by Kepler's laws. An orbit is characterized by orbital elements: semi-major axis a, eccentricity e, inclination i, longitude of ascending node Ω, argument of periapsis ω, and true anomaly ν. The vis-viva equation relates orbital speed v to distance r and a: v^2 = μ(2/r − 1/a), where μ is the primary's gravitational parameter. Energy and angular momentum provide a global description.

In practice, perturbations from non-spherical gravity, atmospheric drag, third bodies, radiation pressure, and thrust must be included. For mission design, common techniques include Hohmann transfers, bi-elliptic transfers, and Lambert's problem for time-constrained transfers; patched-conics approximate more complex gravity fields. Numerical integration and orbit determination using tracking data are essential for ephemerides and re-entry predictions.

Historically, orbital mechanics emerged from Kepler's laws and Newtonian gravity, matured with spaceflight in the mid-20th century, enabling satellite deployment and interplanetary travel. It remains central to mission planning, satellite navigation, debris mitigation, and planetary science.