Dry lubricants are often used in space because of their excellent behaviour under vacuum and their thermal stability. But some mechanisms (which are heavily loaded, have a high sliding rate, a long life duration or need a stable friction coefficient) cannot use this kind of product. Therefore, they can be replaced by wet lubricants specially developed for vacuum applications. The vapour pressure of these lubricants is low, so outgassing losses and contamination are limited. The American experience with wet lubrication in space is greater than the European one. Therefore, CNES, with the help of LMC, began a tribological characterization under vacuum of wet lubricants which can be used for space applications. The selected lubricants are tested on a vacuum friction test bench which allows the control of the main contact parameters: speed, load, kinematics, atmosphere. Variations of physical properties versus temperature and pressure are taken into account in the test results analysis through a rheological characterization performed on the lubricants tested. This paper presents the facilities used and all the tribological and rheological test results obtained on three lubricants (two oils and one grease). It contains the first conclusions in terms of recommendations for using such lubricants. The last part concerns the future investigations which should lead to an improvement in their understanding of phenomena encountered in lubricated contacts under vacuum.
Tribological characterization of spatial wet lubricants under vacuum
Tribologische Charakterisierung von Weltraumschmierstoffen unter Vakuum
1993
7 Seiten, 9 Bilder, 7 Quellen
Conference paper
English
Vakuum , Tribologie , Trockenschmiermittel , Kinematik , Weltraum , thermische Stabilität , Gleitgeschwindigkeit , Reibungskoeffizient , Dampfdruck (Mechanik) , Schmierung , Geschwindigkeit , Last (mechanisch) , Rheologie , physikalische Eigenschaft , Ausgasen , Verlustrate , Schmutz , Reibung , Temperatur
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