Editing Reaction control system (section)

== Uses ==

Spacecraft reaction control systems are used for:

* [[Spacecraft attitude control|attitude control]] during different stages of a mission;<ref>{{Citation |last1=Colas |first1=Armand L. |title=Reaction Control System Performance Characterization using Vacuum Chamber Thrust Stand |date=2020-08-17 |url=https://arc.aiaa.org/doi/10.2514/6.2020-3526 |work=AIAA Propulsion and Energy 2020 Forum |series=AIAA Propulsion and Energy Forum |publisher=American Institute of Aeronautics and Astronautics |doi=10.2514/6.2020-3526 |access-date=2022-09-27 |last2=Valenzuela |first2=Juan G.|isbn=978-1-62410-602-6 |s2cid=225270552 |url-access=subscription }}</ref>
* [[Orbital station-keeping|station keeping]] in [[orbit]];
* close [[Space rendezvous|maneuvering]] during [[Space rendezvous|docking]] procedures;
* control of [[Orientation (geometry)|orientation]], or "pointing the nose" of the craft;
* a backup means of [[atmospheric reentry|deorbiting]];
* [[ullage motor]]s to prime the fuel system for a main engine burn.

Because spacecraft only contain a finite amount of fuel and there is little chance to refill them, alternative reaction control systems have been developed so that fuel can be conserved. For stationkeeping, some spacecraft (particularly those in [[geosynchronous orbit]]) use high-[[specific impulse]] engines such as [[arcjet]]s, [[ion thruster]]s, or [[Hall effect thruster]]s. To control orientation, a few spacecraft, including the [[International Space Station|ISS]], use [[momentum wheel]]s which spin to control rotational rates on the vehicle.