Date of Award

12-1995

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Christopher Hall, PhD

Abstract

This thesis addresses sub-optimal employment of 3 momentum wheels for large angle reorientation of rigid spacecraft with minimal induced spacecraft motion during maneuvers. In addition to development of general theory for 3 wheel vehicles, simulation results for a vehicle using momentum wheels for secondary attitude control (GPS Block IIR) are compared to results for a vehicle using them for primary attitude control (the Hubble Space Telescope), to demonstrate practical applications and limitations. While the control laws were developed assuming no external perturbing torques on the vehicle, reorientation scenarios were run both in a torque free environment as well as an environment with simulated gravity gradient and solar pressure torques. The goal was primarily to show the growth of vehicle angular velocities and again demonstrate limitations of the derived control laws. The results indicate that for real spacecraft with limited wheel momentum storage capacities, there is a significant trade-off between maneuver times and required wheel torques, and that final state errors (angular velocities) increase with increasing wheel torques. Nonetheless, the simulations demonstrated that large angle maneuvers can be performed for both GPS Block lift and Hubble Space Telescope in reasonable times and with small angular velocities using the sub-optimal control law. However, gravity gradient and solar pressure torques tended to cause larger fluctuations in total angular momentum, angular velocities, and final state errors for the Hubble Space Telescope.

AFIT Designator

AFIT-GA-ENY-95D-04

DTIC Accession Number

ADA302280

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