Crew motions can affect the angular orientation of a spacecraft. Such motions are of a somewhat random nature and must be treated stochastically. The equations of motion for the spacecraft are solved to obtain a simple relationship between individual crew motions and the angular change in spacecraft orientation. For the majority of manned spacecraft, the angular changes about the three principal axes of inertia can be considered independent. The additive effect of many motions, considered random in frequency and magnitude, is found by treating the motion as a form of random walk. Solutions are obtained for the time required to reach predetermined maximum allowable angular deviation limits. If reaction control jets are used for stabilization, this time determines the frequency of firing and the fuel consumption rate. For relatively heavy spacecraft, such as those designed to carry three or more crew members, the complete solution to the diffusion equation gives the time between control jet firing; this solution has a particularly simple form. For smaller spacecraft, where individual motions may cause a change in orientation which is several percent of the maximum allowable, additional solutions have been obtained using Markov chain matrix analysis; numerical values for the matrix equations can be obtained from a digital computer. / Ph. D.