Publication:
Applications of tuned mass dampers to improve performance of large space mirrors

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Authors
Yingling, Adam J.
Agrawal, Brij N.
Subjects
Smart structures
Imaging satellites
Adaptive optics
Tuned mass dampers
Active hybrid mirrors
Advisors
Date of Issue
2014
Date
Publisher
Language
Abstract
In order for future imaging spacecraft to meet higher resolution imaging capability, it will be necessary to build large space telescopes with primary mirror diameters that range from 10m to 20 m and do so with nanometers surafce accuracy. Due to launch vehicle mass and volume constraints, these mirrors have to be deployable and lightweight, such as segmented mirrors using active optics to correct mirror surfaces with closed loop control. As a part of this work, system identification tests revealed that dynamic disturbances inheret in a laboratory environment are significant enough to degrade the optical performance of the telescope. Research was performed at the Naval Postgraduate School to identify the vibration modes most affecting the optical performance and evaluate different techniques to increase damping of those modes. Based on this work, tuned mass dampers (TMDs) were selected becaues of their simplicity in implementation and effectiveness in targeting specific modes. The selected damping mechanism was an eddy current damper where the damping and frequency of the damper could be easily changed. System identification of segments was performed to derive TMD specifications. Several configurations of the damper were evaluated, including the number and placement of TMDs, damping constant, and targeted structural modes. The final configuration consisted of two dampers located at the edge of each segment and resulted in the 80% reduction in vibrations. The WFE for the system without dampers was 1.5 waves, with one TMD and the WFE was 0.9 waves, and the two TMDs and the WFE was 0.25 waves. This paper provides details of some of the work done in this area and includes theoretical predictions for optimum damping which were experimentally verified on a large aperture segmented system.
Type
Article
Description
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Department
Mechanical and Aerospace Engineering
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NPS Report Number
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Funder
The authors would like to sincerely acknowledge the contribution of the members of NPS Spacecraft Reserarch and Design Center (SRDC) and the Adaptive Optics Center of Excellence (AOCoE). Research presented in this work was also conducted in collaboration with the Air Force Institute of Technology (AFIT), CSA Engineering, a Moog company,and Boeing SVS.
Format
Citation
Acta Astronautica, Volume 94, 2014, pp. 1-13.
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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