Abstract
Spacecraft mechanisms commonly undergo extended periods of storage, either on-ground, or in-flight and there are an increasing number of missions for which some element of long-term storage may be required. Despite the obvious potential for degradation of lubricants during storage which might impact mechanism functionality or life and so even become mission-threatening, today’s understanding of storage phenomena is rather incomplete. This paper provides consolidation and review of recent experimental studies in this area and considers the range of storage conditions and associated degradation phenomena which could impact different lubricants. Whilst some storage best practice guidelines exist, experimental verification of the impact of storage phenomena has rarely been carried out and test data is rather scarce and incomplete. Given the absence of comprehensive data to support design, lubricant selection or the development of storage protocols, it is shown that for all lubricant types careful control of storage and test environments combined with monitoring of the evolving tribological performance during periodic mechanism exercising are presently the most effective storage risk mitigations.
Highlights
Spacecraft mechanism components are commonly stored before or after spacecraft integration for a considerable time
This review presents recent experimental data generated by ESTL into the potential effects of the above on the tribological performance of solid and fluid lubricants, together with insights gleaned from over 40 years of consultancy and testing support to the European space mechanisms industry
Given that Z25 provides a friction coefficient of ~0.1 under vacuum on the Spiral Orbit Tribometer (SOT) [2], it can be saidvacuum with some confidence that the was providing lubrication at this time and had been
Summary
Spacecraft mechanism components are commonly stored before or after spacecraft integration for a considerable time Such storage can occur prior to launch (on-ground storage), or in-flight where a mechanism remains dormant but exposed to the flight environment potentially for some years prior to operation. This review presents recent experimental data generated by ESTL into the potential effects of the above on the tribological performance of solid and fluid lubricants, together with insights gleaned from over 40 years of consultancy and testing support to the European space mechanisms industry. One must draw from available datasets to gain confidence in the impact of these factors These phenomena must be adequately understood as lubricant degradation during spacecraft storage or in-flight could be mission-compromising
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