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- Reaction_wheel abstract "A reaction wheel (RW) is a type of flywheel used primarily by spacecraft for attitude control without using fuel for rockets or other reaction devices. They are particularly useful when the spacecraft must be rotated by very small amounts, such as keeping a telescope pointed at a star. They may also reduce the mass fraction needed for fuel. This is accomplished by equipping the spacecraft with an electric motor attached to a flywheel which, when its rotation speed is changed, causes the spacecraft to begin to counter-rotate proportionately through conservation of angular momentum. Reaction wheels can only rotate a spacecraft around its center of mass (see torque); they are not capable of moving the spacecraft from one place to another (see translational force). Reaction wheels work around a nominal zero rotation speed. However, external torques on the spacecraft may require a gradual buildup of reaction wheel rotation speed to maintain the spacecraft in a fixed orientation.A reaction wheel is sometimes operated as (and referred to as) a momentum wheel, by operating it at a constant (or near-constant) rotation speed, in order to imbue a satellite with a large amount of stored angular momentum. Doing so alters the spacecraft's rotational dynamics so that disturbance torques perpendicular to one axis of the satellite (the axis parallel to the wheel's spin axis) do not result directly in spacecraft angular motion about the same axis as the disturbance torque; instead, they result in (generally smaller) angular motion (precession) of that spacecraft axis about a perpendicular axis. This has the effect of tending to stabilize that spacecraft axis to point in a nearly-fixed direction, allowing for a less-complicated attitude control system. Satellites using this "momentum-bias" stabilization approach include SCISAT-1; by orienting the momentum wheel's axis to be parallel to the orbit-normal vector, this satellite is in a "pitch momentum bias" configuration.A control moment gyro (CMG) is a related but different type of attitude actuator, generally consisting of a momentum wheel mounted in a one-axis or two-axis gimbal. When mounted to a rigid spacecraft, applying a constant torque to the wheel using one of the gimbal motors causes the spacecraft to develop a constant angular velocity about a perpendicular axis, thus allowing control of the spacecraft's pointing direction. CMGs are generally able to produce larger sustained torques than RWs with less motor heating, and are preferentially used in larger and/or more-agile spacecraft, including Skylab and the International Space Station.".
- Reaction_wheel thumbnail Reaction_wheel00.jpg?width=300.
- Reaction_wheel wikiPageExternalLink viewcontent.cgi?filename=0&article=1496&context=smallsat&type=additional.
- Reaction_wheel wikiPageID "89484".
- Reaction_wheel wikiPageRevisionID "592906950".
- Reaction_wheel hasPhotoCollection Reaction_wheel.
- Reaction_wheel subject Category:Gyroscopes.
- Reaction_wheel subject Category:Spacecraft_attitude_control.
- Reaction_wheel subject Category:Spacecraft_propulsion.
- Reaction_wheel type Artifact100021939.
- Reaction_wheel type Device103183080.
- Reaction_wheel type Gyroscope103473227.
- Reaction_wheel type Gyroscopes.
- Reaction_wheel type Instrumentality103575240.
- Reaction_wheel type Mechanism103738472.
- Reaction_wheel type Object100002684.
- Reaction_wheel type PhysicalEntity100001930.
- Reaction_wheel type RotatingMechanism104110955.
- Reaction_wheel type Whole100003553.
- Reaction_wheel comment "A reaction wheel (RW) is a type of flywheel used primarily by spacecraft for attitude control without using fuel for rockets or other reaction devices. They are particularly useful when the spacecraft must be rotated by very small amounts, such as keeping a telescope pointed at a star. They may also reduce the mass fraction needed for fuel.".
- Reaction_wheel label "Reaction wheel".
- Reaction_wheel label "Reaktionsrad".
- Reaction_wheel label "Roue de réaction".
- Reaction_wheel label "Rueda de reacción".
- Reaction_wheel label "リアクションホイール".
- Reaction_wheel sameAs Reaktionsrad.
- Reaction_wheel sameAs Rueda_de_reacción.
- Reaction_wheel sameAs Roue_de_réaction.
- Reaction_wheel sameAs Roda_reaksi.
- Reaction_wheel sameAs リアクションホイール.
- Reaction_wheel sameAs m.0m9zd.
- Reaction_wheel sameAs Q2457049.
- Reaction_wheel sameAs Q2457049.
- Reaction_wheel sameAs Reaction_wheel.
- Reaction_wheel wasDerivedFrom Reaction_wheel?oldid=592906950.
- Reaction_wheel depiction Reaction_wheel00.jpg.
- Reaction_wheel isPrimaryTopicOf Reaction_wheel.
