RESONANCES IN THE DESPIN DYNAMICS OF DUAL-SPIN SPACECRAFT

A unifying treatment of the nutation resonances encountered during the despin of platform of a dual-spin spacecraft with transverse inertia asymmetry and either platform or rotor imbalance is developed. The linear model equations governing the resonance dynamics depend on three nondimensional parameters that measure the degree of dynamic imbalance, asymmetry, and the time duration available for resonance growth. The solution dependence on all of these parameters is studied, and the basic physics of the phenomena is emphasized. The linear theory is supplemented by a simple variational analysis that provides a phase plane geometric interpretation of a rather interesting saddle-type transition, which has been observed in fully nonlinear simulations. The transition leads to an abrupt change in the spin orientation commonly known as the "stall" in spacecraft despin maneuvers.