40. Lesson: Lubrication of Rotating Machinery
If possible, positive lubrication methods should be included in the design of long-life rotating machinery, such as control moment gyros.
Two of the Skylab CMG's experienced bearing anomalies (temperature increases) and one (CMG #1) failed on day 194. Analysis indicates that poor lubrication caused bearing failure. The CMG's were designed with an automatic lubrication metering system which was chosen to minimize the need for active control, to maximize bearing life, and to prevent contamination by containing all oil. Life tests conducted on the ground far exceeded the required life.
In retrospect, it appears as if the forces on the oil in zero gravity caused it to seek different locations than in one-g where full lubrication was possible. Since fluid flow In zero-g is not yet fully understood, it appears prudent to design a system with positive control.
These lessons learned are from SKYLAB LESSONS LEARNED AS APPLICABLE TO A LARGE SPACE STATION, A dissertation submitted to the faculty of The School of Engineering and Architecture Of the Catholic University of America For the Degree Doctor of Engineering by William C. Schneider, Washington, D.C., 1976.
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