For three-axis control, reaction wheels must be mounted along at least three directions, with extra wheels providing redundancy to the attitude control system. A redundant mounting configuration could consist of four wheels along tetrahedral axes, or a spare wheel carried in addition to a three axis configuration. Changes in speed (in either direction) are controlled electronically by computer. The strength of the materials used in a reaction wheel determine the speed at which the wheel would come apart, and therefore how much angular momentum it can store.
For three-axis control reaction wheels must be mounted along at least three directions with extra wheels providing redundancy to the attitude control system A redundant mounting configuration could consist of four wheels along tetrahedral axes or a spare wheel carried in addition to a three axis configuration Changes in speed (in either direction) are controlled electronically by computer The strength of the materials used in a reaction wheel determine the speed at which the wheel would come apart and therefore how much angular momentum it can store