Effect of Space Vehicle Structure Vibration on Control Moment Gyroscope Dynamics
- Paper number
IAC-08.C2.3.6
- Author
Dr. Tatiana Dobrinskaya, United Space Alliance, LLC, United States
- Year
2008
- Abstract
Control Moment Gyroscopes (CMGs) are used for non-propulsive attitude control of satellites and space stations, including the International Space Station (ISS). CMGs could be essential for future long duration space missions due to the fact that they help to save propellant. CMGs were successfully tested on the ground for many years, and have been successfully used on satellites. However, operations have shown that the CMG service life on the ISS is significantly shorter than predicted. Since the dynamic environment of the ISS differs greatly from the nominal environment of satellites, it was important to analyze how operations specific to the station (dockings and undockings, huge solar array motion, crew exercising, robotic operations, etc) can affect the CMG performance. This task became even more important since the first CMG failure onboard the ISS. The CMG failure resulted in the limitation of the attitude control capabilities, more propellant consumption, and additional operational issues. Therefore, the goal of this work was to find out how the vibrations of a space vehicle structure, caused by a variety of onboard operations, can affect the CMG dynamics and performance. The equations of CMG motion were derived and analyzed for the case when the gyro foundation can vibrate in any direction. The analysis was performed for unbalanced CMG gimbals to match the CMG configuration on ISS. The analysis showed that vehicle structure vibrations can amplify and significantly change the CMG motion if the gyro gimbals are unbalanced in flight. It was shown that the resonance effect depends on the magnitude of gimbal imbalance, on the direction of a structure vibration, and on gimbal bearing friction. Computer modeling results of CMG dynamics affected by the external vibration are presented. The results can explain some of the CMG vibration telemetry observed on ISS. The conclusions of this work not only could help to increase CMG service life, but also could eliminate the critical limitations of the vehicle attitude control function. Copyright (c) 2008 by United Space Alliance, LLC. These materials are sponsored by the National Aeronautics and Space Administration under Contract NNJ06VA01C. The U.S. Government retains a paid-up, nonexclusive, irrevocable worldwide license in such materials to reproduce, prepare, derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the U.S. Government. All other rights are reserved by the copyright owner.
- Abstract document
- Manuscript document
IAC-08.C2.3.6.pdf (🔒 authorized access only).
To get the manuscript, please contact IAF Secretariat.