Page 228 - Satellite Communications, Fourth Edition

208 Chapter Seven

TELDIX manufactures momentum wheels ranging in size from 20, 26,
35, 50, to 60 cm in diameter that are used in a wide variety of satellites.
Details of these will be found in Chetty (1991).
The term momentum wheel is usually reserved for wheels that
operate at nonzero momentum. This is termed a momentum bias.
Such a wheel provides passive stabilization for the yaw and roll axes
when the axis of rotation of the wheel lies along the pitch axis, as
shown in Fig. 7.8a. Control about the pitch axis is achieved by changing
the speed of the wheel.

Figure 7.8 Alternative momentum wheel stabilization systems: (a) one-wheel, (b) two-
wheel, (c) three-wheel. (Reprinted with permission from Spacecraft Attitude Determination
and Control, edited by James R. Wertz. Copyright, 1984 by D. Reidel Publishing Company,
Dordrecht, Holland.)