Correlations of Space-Charging Environments With Aerospace Mechanism Friction Anomalies

A relentless root cause analysis of a series of unresolved bearing failures and friction anomalies on spacecraft utilizing ITHACO reaction wheels was funded and completed by United Technologies Corporation, Danbury, CT, USA, which is now known as Collins Aerospace. The analysis implicated a severe space-charging environment as a likely root cause, a factor that was not considered in the previous failure investigations. The strong correlation of geomagnetic storms with ball bearing friction events observed on-orbit was supported by the results of laboratory tests, which successfully duplicated the friction event signatures. The objective of this paper is to shed a new light on previously unexplained or unverified bearing anomalies and failures using this new approach to mechanism friction behavior. The scope of this paper is to open the discussion of anomalous friction signatures to include the effects of the space environment and electrical discharge and introduce this potential root cause to both the space charging and space mechanism communities.