FOR SPACE APPLICATIONS

Abstract

QuynhGiao N. Nguyen t and William R. Jones, Jr. (Fellow, STLE)NASA Glenn Research CenterCleveland, Ohio 44135AbstractThe vapor pressures and wear characteristics are critical properties for liquid lubricants to assure long-term reliability and performance in space applications. Vapor pressures, obtained using a Knudsen celltechnique, and wear properties, obtained using a vacuum four-ball apparatus, were measured for a series ofunformulated liquid lubricants. These included: two multiply alkylated cyclopentanes (MACs) (X-1000 and X-2000), two linear perfluoropolyalkylethers (PFPAEs) (Z-25 and 815Z), and four silahydrocarbons (a tri-,a tetra-and two pentas). Vapor pressures were measured at three elevated temperatures (423,448 and 498K) andextrapolated to room temperature 298K. The lowest 298K vapor pressure of 5.7 x 1014 Pa, was obtained with thePFPAE fluid (815Z) and the highest value with the low molecular weight MAC (X-1000) at 3.6 x 10.7 Pa. Inaddition, vacuum wear rates were determined for some of the lubricants. The lowest wear rates (approximately 3x 1011 mm3/mm) were observed for three of the silahydrocarbons while the highest wear rates (approximately 2 x10.9mm3/mm) were observed with the two PFPAE fluids (Z-25 and 815Z). The MAC (X-2000) yielded a wear rateof about 101° mm3/mm. The results indicated that the silahydrocarbon class of liquid lubricants offers the betterpotential for space applications.KeywordsFluorocarbons, Hydrocarbons, Space Vehicles, Synthetic Lubricants, Vapor Pressure, Wear Testing DeviceIntroductiont Work performed as a contractor for AYT Corporation, Brookpark, Ohio 44142This report is a preprint of an article submitted to a journal forpublication. Because of changes that may be made before formalpublication, this preprint is made available with the understandingthat it will not be cited or reproduced without the permission of theauthor.