DYNAMICAL ANALYSIS OF A THREE-BODY GRAVITY-GRADIENT SPACECRAFT.
JOHNS HOPKINS UNIV SILVER SPRING MD APPLIED PHYSICS LAB
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This paper gives the results of a dynamical analysis of the in-orbit-plane motion of a three-body spacecraft. The linearized differential equations of motion and characteristic determinant are developed for gravity-gradient stabilization with passive damping of librational energy. Two damping techniques are considered one depends on relative motion between the component bodies of the spacecraft, the other on the relative motion between the spacecraft and an ambient magnetic field. The general results are applied to an artificial earth satellite consisting of two rigid bodies connected by a cable which is several miles long. With only viscous damping at the cable pivots, it is demonstrated that an undamped libration mode exists unless the two rigid bodies have triaxial ellipsoids of inertia. Furthermore, the time constants of the motion are inadequate even for unrealistically large mass distributions. The second damping technique considered gives more favorable results. Acceptable transient performance is obtained by dissipating energy viscously through the geomagnetic field. In addition, triaxial inertia ellipsoids of the two end bodies are not required. Author
- Unmanned Spacecraft