Global Treatment of Energy Dissipation Effects for Multibody Satellites

Summary

For actual satellites, consisting of several bodies, principal axes and principal inertia moments can usually be defined in some fashion, e.g. either by indentifying the undeformed shape of the bodies and the system, or by referring to an attitude of maximum or minimum kinetic energy for a given angular momentum, i.e. collnearity of angular momentum and angular velocity, which in turn is associated with no deformation, this time enforced by the kinetics of the system. If furthermore elasticity is generally neglected, in the sense that there shall be neither storage nor release of recoverable mechanical energy nor changes in the inertia moments, except where needed to account for energy dissipation, then the effects of internal energy dissipation can be described in a global fashion. In the present paper the attitude drift of a two-body gyrostat is studied in some detail. It is shown what deformations of each body are required to bring about an attitude drift. The deformed gyrostat configuration is found to be a function of the (slowly changing) attitude angle only, and thus it is (nearly) constant. As a, consequence the gyrostat still consists of bodies that are essentially rigid, though deformed.