A small reaction wheel viewed in profileA momentum/reaction wheel comprising part of a high-accuracy Conical Earth Sensor to maintain a satellite's precise attitude
A reaction wheel (RW) is used primarily by spacecraft for three-axis attitude control, and does not require rockets or external applicators of torque. They provide a high pointing accuracy,[1]: 362 and are particularly useful when the spacecraft must be rotated by very small amounts, such as keeping a telescope pointed at a star.
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, to provide 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,[1]: 362 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 gyroscope (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.[1]: 362 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 or more-agile (or both) spacecraft, including Skylab, Mir, and the International Space Station.
^ abcWiley J Larson and James R Wertz (January 1999). Space Mission Analysis and Design (3 ed.). Microcosm Press. ISBN 1-881883-10-8.
A reactionwheel (RW) is used primarily by spacecraft for three-axis attitude control, and does not require rockets or external applicators of torque....
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mass, large CMGs have produced thousands of newton meters of torque. A reactionwheel of similar capability would require megawatts of power. The most effective...
process that can be used to explain phenomena in several disciplines Reactionwheel, a type of flywheel used primarily by spacecraft for attitude control...
House, the now lost house of Francis Bacon Wollaton Hall In spacecraft reactionwheel layout, a tetrahedral configuration of four wheels is commonly used...
Wheel alignment, which is sometimes referred to as breaking or tracking, is part of standard automobile maintenance that consists of adjusting the angles...
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tracker, a carbon nanotube radio frequency experiment, a commercial reactionwheel to provide attitude control in orbit. The FalconSAT-8 was deployed from...
D. J.; Bertrand, P. A. (1999). "Analysis of Hubble Space Telescope ReactionWheel Lubricant". Journal of Spacecraft and Rockets. 36 (1): 109–113. Bibcode:1999JSpRo...
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Jerry (January 8, 2015). "Heat Death: Venture Capital in the 1980s". ReactionWheel. Archived from the original on April 28, 2020. Retrieved May 5, 2020...
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spacecraft launched in 2009, repurposed as K2 since the failure of a second reactionwheel prevented the telescope from continuing to monitor the same field. BRITE...
on a given axis, the reactionwheel on that axis is accelerated in the opposite direction. To rotate the vehicle back, the wheel is slowed. Excess momentum...
thus its control. It was severely damaged on 20 September 1998 when a reactionwheel in the spacecraft's Attitude Measuring and Control System reached its...
attitude of a vehicle, rather than for energy storage, it is called a reactionwheel or a control moment gyroscope. The resistance of angular tilting can...
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thrusters were used for attitude control. For precision attitude control, a reactionwheel attitude control system was also included. Information for attitude...
pressures. The reaction to a radial load of a well-tensioned wire spoked wheel, such as by a rider sitting on a bicycle, is that the wheel flattens slightly...
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