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A reaction control system (abbreviated RCS) is a subsystem of a spacecraft. Its purpose is attitude control and steering. An RCS system is capable of providing small amounts of thrust in any desired direction or combination of directions. An RCS is also capable of providing torque to allow control of rotation (pitch, yaw, and roll). This is contrast to a spacecraft's main engine, which is only capable of providing thrust in one direction, but is much more powerful. Wikipedia does not yet have an article with this exact name. ...
An Ariane 5 expendable launch vehicle lifts off with the Rosetta spacecraft on March 2, 2004. ...
In the context of spacecraft, attitude control is control of the angular position and rotation of the spacecraft, either relative to the object that it is orbiting, or relative to the celestial sphere. ...
Steering is the term applied to the collection of components, linkages, etc. ...
Thrust is a reaction force described quantitatively by Newtons Second and Third Law. ...
In physics, torque can be thought of informally as rotational force. Torque is commonly measured in units of newton metres; although, centiNewton Meters (cNm), Foot Pounds (Lb-Ft), Inch Pounds (Lb-In) and Inch Ounces (Oz-In) are also frequently used expressions of torque. ...
Rotation of a plane, seen as the rotation of the terrain relative to the plane (exposure time 1. ...
Flight dynamics is the study of orientation of air and space vehicles and how to control the critical flight parameters, typically named pitch, roll and yaw. ...
Reaction control systems are used:
Because spacecraft only contain a finite amount of fuel and there is little chance to refill them (aside from visits by a Space Shuttle, which are very rare), some 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 arcjets, ion thrusters, or Hall Current thrusters. To control orientation, a few spacecraft use momentum wheels which spin to control rotational rates on the vehicle. In the context of spacecraft, attitude control is control of the angular position and rotation of the spacecraft, either relative to the object that it is orbiting, or relative to the celestial sphere. ...
Atmospheric entry is the transition from the vacuum of space to the atmosphere of any planet or other celestial body. ...
In astrodynamics orbital stationkeeping is a term used to descibe a particular set of orbital maneuvers used to keep a spacecraft in assigned orbit, either low earth orbit (LEO), or geostationary orbit (GEO). ...
In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ...
A space rendezvous between two spacecraft, often between a spacecraft and a space station, is an orbital maneuver where the two arrive at the same orbit, make the orbital velocities the same, and bring them together (an approach maneuver, taxiing maneuver); it may or may not include docking. ...
Docking is the cutting off or removal of something, such as a persons pay or an animals tail. ...
Orientation can refer to different things. ...
For the workstation, see SGI Fuel. ...
The Space Shuttle Columbia seconds after engine ignition, 1981 (NASA). ...
A geosynchronous orbit is a geocentric orbit that has the same orbital period as the sidereal rotation period of the Earth. ...
The specific impulse (commonly abbreviated Isp) of a propulsion system is the impulse (change in momentum) per unit of propellant. ...
This article or section does not cite its references or sources. ...
A momentum wheel is a type of flywheel used primarily by spacecraft to change their angular momentum without using fuel for rockets or other reaction devices. ...
Location of thrusters on space capsules
The placing of the approach or translation engines (which cause the spacecraft to move) on the surface of a spacecraft has one important requirement that the placing of the orientation thrusters (which cause the spacecraft to turn) does not. If the direction of thrust of the former does not pass through the center of mass of the spacecraft, when tracked backward from the nozzle, the spacecraft will turn as an unwanted side effect. Sometimes this is unavoidable, but spacecraft are not operated by automatically firing the orientation thrusters to counteract this because such a system might fail. So a separate step of re-orientation is required afterward. Image File history File links LM_RCS.jpg Summary Apollo LM (Lunar Module) RCS (Reaction Control System) quads. ...
Image File history File links LM_RCS.jpg Summary Apollo LM (Lunar Module) RCS (Reaction Control System) quads. ...
The Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program to achieve the transit from Moon orbit to the surface and back. ...
Translation thrusters thus have less of a variety of permissible locations than do orientation thrusters. In the Apollo spacecraft, both the Service Module and the Lunar Module, as well as the Chinese Shenzhou spacecraft, they are grouped in blocks of four, which are themselves attached to the outside of the spacecraft at each end of the two axes of a cross-section of the spacecraft through the long axis. Used in a variety of combinations, these thrusters are sufficient for both approach and orientation. Other designs use separate sets of thrusters.
A similar pattern is seen in the forward compartments of the Mercury and Gemini spacecraft. This is the equivalent of removing the two nozzles from each of the blocks of four which point in the longitudinal directions, then pushing the blocks inward, and cutting slots for the exhaust to escape. (This grouping is then rotated by 45 degrees.) These thrusters, however, are only used after the re-entry rockets or other modules have been jettisoned; any translation of the spacecraft that they would provide is a mere by-product. Indeed, the Mercury spacecraft has no separate capacity for translation at all. The re-entry modules of both Apollo and Soyuz have their thrusters ungrouped.
A pair of translation thrusters to go forward are located at the rear of both the Gemini and Soyuz spacecraft; the counter-acting thrusters are similarly paired in the middle of each spacecraft, pointing a bit outward besides forward. These act in pairs to prevent the spacecraft turning. The thrusters for the lateral directions are mounted as close to the center of mass of each of these spacecraft as well, but Gemini has only one engine for each of the directions while Soyuz continues with pairs.
None of these engines is intended for orientation. For that purpose, both Gemini and Soyuz have engines at the extreme rear of the spacecraft. Here Soyuz uses engines only one-tenth the power of the others, arranged in a unique pattern, while Gemini has engines arranged in the same pattern of eight as it uses for re-entry.
Gemini has no main orbit maneuvering engine as do the Apollo Service Module or Soyuz. It was light enough to change orbit without a separate engine.
Finally, Soyuz has a thruster at the rear of the spacecraft that points parallel to each solar panel, but which is not used for rendezvous at all. Instead, when the solar panels are pointing to the sun, the option exists to use this motor to spin the spacecraft to keep it pointing to the sun by gyroscopic action. Otherwise, a computer system would be kept running to automatically keep the panels so pointed, wasting electricity and propellant. The spin is stopped by the counterpart engine on the other side.
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