Astronautics Glossary

A thermal protection method where the heat shield material charrs and erodes away, carrying heat with it during atmospheric reentry.

The point in an orbit around Earth that is farthest from the planet's center.

The science and technology of spaceflight, including the design and operation of rockets, spacecraft, and space missions.

The process of orienting a spacecraft in a desired direction using reaction wheels, thrusters, or magnetic torquers.

A rocket propulsion system using two separate propellants, a fuel and an oxidizer, that are combined in a combustion chamber.

A coordinated group of satellites working together to provide continuous coverage or service, such as GPS or Starlink.

The total change in velocity a spacecraft can achieve through propulsion; the primary metric for mission feasibility and planning.

The minimum speed needed for an object to escape a celestial body's gravitational influence without further propulsion.

A circular equatorial orbit at 35,786 km altitude where a satellite's orbital period matches Earth's rotation, appearing stationary.

A maneuver using a planet's gravity to alter a spacecraft's speed and trajectory without consuming propellant.

A fuel-efficient two-impulse maneuver using an elliptical orbit to transfer between two coplanar circular orbits.

A fuel-oxidizer combination that ignites spontaneously on contact, requiring no ignition system. Used in spacecraft thrusters for reliability.

An electric propulsion device that creates thrust by accelerating ionized propellant using electric fields, achieving very high specific impulse.

A theoretical scenario in which cascading collisions of orbital debris create enough fragments to make certain orbits hazardous or unusable.

One of five gravitational equilibrium positions in a two-body system where a small object can maintain a relatively stable position.

An orbit between approximately 160 km and 2,000 km altitude above Earth's surface.

The ratio of a rocket's initial total mass (with propellant) to its final mass (after propellant is expended).

The angle between a satellite's orbital plane and the reference plane, usually Earth's equatorial plane.

The branch of physics and engineering dealing with the motion of objects in gravitational fields, fundamental to spacecraft trajectory design.

The cargo carried by a launch vehicle into space, such as satellites, scientific instruments, crew modules, or supplies.

The point in an orbit around Earth that is closest to the planet's center.

The precise maneuver of bringing two spacecraft into close proximity in orbit, often as a precursor to docking.

A measure of propulsion efficiency expressed as thrust per unit weight of propellant consumed per second, measured in seconds.

The technique of using multiple sequential rocket sections that are discarded when emptied to improve overall mass ratio and performance.

The ratio of a rocket engine's thrust to the weight of the vehicle, determining whether it can lift off and how quickly it accelerates.