Gyroscope of the International Space Station

A momentum wheel or reaction wheel is a type of flywheel used primarily by spacecraft to change their angular momentum without using fuel for rockets or other reaction devices. They increase the pointing precision and reliability of a spacecraft, and may also reduce the mass fraction needed for fuel. However, they are not capable of producing translational force - only torque. Image File history File links Download high-resolution version (2304x1536, 499 KB) Gyroscope of the International Space Station (July 22, 1998) original description: Boeing technicians remove the cover from a Control Moment Gyroscope (CMG) in the Space Station Processing Facility at KSC. The CMG will be attached to the Integrated... Image File history File links Download high-resolution version (2304x1536, 499 KB) Gyroscope of the International Space Station (July 22, 1998) original description: Boeing technicians remove the cover from a Control Moment Gyroscope (CMG) in the Space Station Processing Facility at KSC. The CMG will be attached to the Integrated... ISS redirects here. ... Spoked flywheel Simple flywheel in motion. ... A spacecraft is a vehicle, vessel, craft or device designed to operate beyond the surface of the Earth in outer space. ... Gyroscope. ... A Redstone rocket, part of the Mercury program The traditional definition of a rocket is a vehicle, missile or aircraft which obtains thrust by the reaction to the ejection of fast moving fluid from within a rocket engine. ... In physics, a translation is the operation changing the positions of all objects according to the formula where is a constant vector. ... Torque applied via an adjustable end wrench Relationship between force, torque, and momentum vectors in a rotating system In physics, torque can informally be thought of as rotational force or angular force which causes a change in rotational motion. ...

Momentum wheels are usually implemented as special electric motors. Both spin-up and braking are controlled electronically by computer controls. The strength of the materials of a momentum wheel establishes a speed at which the wheel would come apart, and therefore how much angular momentum it can store. Rotating magnetic field as a sum of magnetic vectors from 3 phase coils. ...

Since the momentum wheel is a small fraction of the spacecraft's total mass, easily-measurable changes in its speed provide very precise changes in angle. It therefore permits very precise changes in a spacecraft's attitude. For this reason, momentum wheels are often used to aim spacecraft with cameras or telescopes.

Over time momentum wheels may build up stored momentum that needs to be cancelled. Designers therefore supplement momentum wheel systems with other attitude control mechanisms. The most efficient practice is probably to use high-efficiency attitude jets such as ion thrusters, or small, lightweight solar sails on the ends of projecting masts or solar cell arrays. Most spacecraft, however, also need fast pointing, and cannot afford the extra mass-fraction of three attitude control systems. Designers therefore usually use conventional monopropellant attitude jets to cancel momentum wheels, as well as for fast pointing. This article or section does not cite its references or sources. ... Concept image of a solar sail spacecraft in the process of unfurling sails. ... A monopropellant rocket (or monoprop rocket) is a rocket that uses a single chemical as its power source and propellant. ...

See also

• Gyroscope
• Control Moment Gyroscope
• Attitude control
• Spacecraft propulsion
• Reaction control system