Digital simulation of counterspun nutation damper operation under non-ideal operating conditions

A computational model of a counterspun nutational damping device (CND) for spacecraft is developed, taking the possibilities of nonaxisymmetry, large nutation angle, and nutation growth due to energy-dissipative mechanisms into account. The principles of CND operation are introduced, and the effects of nonideal operating conditions are characterized. A set of 11 first-order differential equations is derived to describe the system and programmed in a continuous-system simulation language. Energy-dissipative effects are modeled on the analogy of a spherical fuel tank, but tunable to any exponential time index of nutational growth; the CND flywheel is simulated by gyroscope-motion equations. The results of sample runs using realistic input parameters are illustrated and discussed. The effects of a misaligned CND drive axle and of Coulomb friction are considered and found to be easily correctible, while spacecraft asymmetry is shown to have little negative effect on the performance of the CND.