Stable Limit Cycles due to Nonlinear Damping in Dual-Spin Spacecraft

It is demonstrated that in the presence of energy dissipators on both rotor and despun platform of a dual-spin spacecraft it is possible for the vehicle to be unstable in its nominal attitude with rotor spin axis inertially stationary, but stable in a nearby state of free precession. Heuristic "energy sink" arguments are used to predict the indicated stability behavior for systems with various kinds of damping nonlinear!ties, and these predictions are confirmed by digital computer simulation. The similar anomalous flight behavior of Tacsat 1 is cited as evidence of the practical implications of this phenomenon.