Librational instability of rigid space station due to translation ofinternal mass

Abstract

the attitude stability of an Earth-pointing space station subjected to harmonic translation of onboard equipment is considered. It is shown that instability may occur if the period of translation is in the vicinity of the orbital period. Such periodic motion may result, for example, from experimentation that would require mass or crew shifting to the Earth end of the station at each passover of a ground location. Instability occurs for a range of station configurations expressed parametrically as two principal-moment-of-inertia ratios. The larger the moving internal mass and the larger its amplitude of motion, the wider the region of instability. Results are presented for point mass motion along the station axis that nominally is aligned to the local vertical. A similar analysis procedure could be applied to translation of a mass of arbitrary shape along any principal axis.