 | | A spinning wheel that can be moved to change the orientation of a body to which the wheel is attached. Reaction wheelsare used in many satellites, including the Hubble Space Telescope, to allow precise pointing. By attaching an electricmotor to a heavy wheel, and spinning the wheel one way quickly, a satellite rotates the other way slowly byconservation of angular momentum. This method can be made very precise, and it doesn't use up fuel. The problem is that if there is some small continuoustorque on a satellite, e.g.,radiation pressure, thewheels end up spinning all the time, faster and faster, to counteract it. The answer to that is to have some way ofdumping momentum. The usual technique, used by the Hubble Space Telescope, is utilizing a set of electromagnets thatcan be used to exert a weak torque against the Earths magnetic field.  Conservation of Angular Momentum
© 1996-2007 Eric W. Weisstein |
