Evaluation of energy-sink stability criteria for dual-spin spacecraft
Ortiz, Vincent Michael.
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The nutational stability of a dual-spin, quasi-rigid, axisymmetric spacecraft containing a driven rotor is analyzed. The purpose is to examine a revised energy-sink stability theory that properly accounts for the energy contribution of the motor. An inconsistency in the development disproves the existing energy-sink theory's assumption that the motor of the system contributes exactly enough energy to offset the frictional losses between the rotor and the platform. Using the concept of core energy, the revised stability criteria for a dual-spin, quasi-rigid, axisymmetric spacecraft containing a driven rotor is derived. An expression for nutation angle as a function of core energy over time is then determined. Numerical simulations are used to verify the revised energy-sink stability theory. The dual-spin, quasi-rigid, axisymmetric system presented by D. L. Mingori was chosen for the simulation. Equations for angular momentum and total energy were necessary to validate the numerical simulation and confirm aspects of the revised energy-sink stability theory. These equations are derived from the first principles of dynamics and are included in the analysis. An explicit relationship for core energy as a function of time does not exist. Various models postulating core energy are presented and analyzed. The numerical simulations of the computed nutation angles as a function of the postulated core energy compare well with the actual nutation angles of the system to confirm the revised energy-sink stability criteria
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