Control moment gyros for the Space Shuttle

It is pointed out that the Space Transportation System (STS) depends upon reaction control systems (RCS) for achieving and maintaining desired attitudes. Precision pointing is provided by the Vernier Reaction Control System (VRCS). While in orbit, the Orbiter is subjected to the action of disturbing forces. These forces are easily controlled by the VRCS. However, the utilization of the VRCS has disadvantages which are related to the ejection of mass in the form of rocket propellants. Ejected contaminants may be deposited on the surfaces of sensitive equipment. In cases requiring the use of precision optics for extended periods, the RCS must be deactivated for some time. This leads to problems due to the lack of positive control of Orbiter pointing during that time. It is therefore, proposed to base a capability for pointing the Orbiter on the employment of control moment gyros (CMG's). Such an approach was used in the case of Skylab. CMG's expend only electrical power, except for the desaturation process.