Nutational stability of dual-spin satellite systems is intimately related to the inertia properties of the vehicle and to the relative energy dissipation rates on the platform and spinner. Energy dissipation on the platform which may be required for stability can be effeciently achieved by passive eddy current nutation damping in which the nutational forcing function acts to impart relative motion between a permanent magnet and a conducting plate. The drag force on the magnet and resulting energy dissipation through eddy current generation in the conductor yield a dissipation rate per unit damper weight substantially greater than that obtainable by more conventional fluid dampers. In addition, an eddy current damper offers the following distinct advantages: it is durable, it does not require a fluid container, it is able to operate over extreme temperature ranges, it will withstand large nutation angles, it is able to damp small nutation since it is essentially free from 'stiction', and it may be conveniently tested in a 1-g environment. In this work the classical energy sink stability criterion for dual-spin systems is reviewed, the equations of motion of the damper are determined, and from these, the nutation damping time constant is derived. Optimization and trade-offs involved in the damper design to meet performance requirements over mission-required operation ranges of temperature, rotor spin speed, inertia properties, etc. are discussed with reference to a specific example. (Author)
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