Abstract
The lubrication of moving mechanical parts in the environment of space presents problems not ordinarily encountered in conventional operating conditions on earth. The special effects to be considered include those of weighlessness, radiation, temperature extremes, and prolonged exposure to hard vacuum. Of these, the last probably represents the most fundamental obstacle to the application of conventional designs, lubricants, and techniques.
The high degree of reliability required in mechanisms for use in space instruments or vehicles necessitates the use of test chambers which have an ultra-high vacuum capability in the range 10-7–10-10 torr. The paper will describe the techniques used and the results obtained from a large number of such tests, conducted in this laboratory, on miniature ball bearings, gears, and jewel bearings. Lubricants studied include low vapour pressure oils and greases, lamellar solids, soft metals, and composites. Basic materials range from plastics to hardened tool-steel.
Over 200 vacuum life tests have been performed on pairs of bearings mounted in specially designed eddy-current motors operating at 3000 rev/min. With certain oils and greases, up to two years' continuous life has been demonstrated. The most successful performance, in terms of life and reliability, has been obtained by the application of the soft metal, lead, as a thin film coating. The longest running test motor has completed in excess of 30 000 h continuous operation at 3000 rev/min in vacuum of 10-10 torr.
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