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The International Space Station Solar Alpha Rotary Joint Anomaly InvestigationThe Solar Alpha Rotary Joint (SARJ) is a single-axis pointing mechanism used to orient the solar power generating arrays relative to the sun for the International Space Station (ISS). Approximately 83 days after its on-orbit installation, one of the two SARJ mechanisms aboard the ISS began to exhibit high drive motor current draw. Increased structural vibrations near the joint were also observed. Subsequent inspections via Extravehicular Activity (EVA) discovered that the nitrided case-hardened steel bearing race on the outboard side of the joint had extensive damage to one of its three rolling surfaces. A farreaching investigation of the anomaly was undertaken. The investigation included metallurgical inspections, coupon tests, traction kinematics tests, detailed bearing measurements, and thermal and structural analyses. The results of the investigation showed that the anomaly had most probably been caused by high bearing edge stresses that resulted from inadequate lubrication of the rolling contact. The profile of the roller bearings and the metallurgical properties of the race ring were also found to be significant contributing factors. To mitigate the impact of the damage, astronauts cleaned and lubricated the race ring surface with grease. This corrective action led to significantly improved performance of the mechanism both in terms of drive motor current and induced structural vibration.
Document ID
20100021920
Document Type
Conference Paper
Authors
Harik, Elliot P. (Boeing Co. Houston, TX, United States)
McFatter, Justin (Boeing Co. Houston, TX, United States)
Sweeney, Daniel J. (NASA Johnson Space Center Houston, TX, United States)
Enriquez, Carlos F. (Boeing Co. Houston, TX, United States)
Taylor, Deneen M. (NASA Johnson Space Center Houston, TX, United States)
McCann, David S. (Boeing Co. Houston, TX, United States)
Date Acquired
August 29, 2013
Publication Date
May 12, 2010
Publication Information
Publication: Proceedings of the 40th Aerospace Mechanisms Symposium
Subject Category
Space Sciences (General)
Distribution Limits
Public
Copyright
Public Use Permitted.

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IDRelationTitle20100021914Analytic PrimaryProceedings of the 40th Aerospace Mechanisms Symposium