MS thesis abstract - Elias, Laila

Author:	Elias, Laila
Degree:	Masters of Science
SERC #:	9-01
File type:	PDF, 7639 kB
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A Structurally Coupled Disturbance Analysis Method Using Dynamic Mass Measurement Techniques, with Application to Spacecraft-Reaction Wheel Systems

The next generation of space-based telescopes, including NASA's Space Interferometry Mission and Next Generation Space Telescope, are being designed to replace and improve upon the Hubble Space Telescope. A common trait of these space observatories, which aim to have maximum aperture size with minimal weight, is that they are lightweight, flexible structures whose dynamic characteristics can strongly influence their ability to achieve scientific goals. The largest vibrational disturbance source onboard most space observatories is the reaction wheel assembly (RWA), a spinning disk used for attitude control and pointing at scientific targets. RWA-induced vibrational disturbances have often been measured and characterized; the measured disturbances are typically combined with information from a finite element model of the spacecraft before it is launched in order to predict its on-orbit dynamic behavior. This traditional disturbance analysis method is flawed in that the RWA disturbances are measured in isolation and do not account for structural dynamic coupling between the RWA and the spacecraft to which it will be mounted.

This report suggests a coupled disturbance analysis method that accounts for spacecraft-RWA structural dynamic coupling by including the dynamic mass matrices of the spacecraft and the RWA in the analysis equations. Both experimental and model-based methods for obtaining all the terms necessary for a coupled analysis are clearly outlined. Experiments performed to validate this coupled analysis method are described in detail, and encouraging results are presented. Finally, recommendations for future work are provided.