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Lube job for the thermosphere.

On Earth, oil makes an excellent lubricant. Off Earth, where gravity no longer plays its convenient circulatory role, the tried and true fluid is less than ideal. In an effort to stop using the stuff in a refrigeration compressor on the International Space Station, Lockheed Martin approached Mainstream Engineering in Rockledge, Fla.

The company's engineers replaced the compressor's old bearings with self-lubricating ones made of Vespel and impregnated with Teflon.

"As the material wears, you get fine particles that actually lubricate the bearings," said Greg Cole, Mainstream's engineering director. These bearings are grooved to dispose of the particles and avoid buildup. They also use permanently lubricated seal bearings and add a cylinder liner to the piston cylinder arrangement.

As the wear of the bearings is what produces the solid lubricant, the new compressor has a life of 1,500 hours, an order of magnitude shorter than its terrestrial, oil-lubricated peers. Mainstream Engineering hopes that the next version of the compressor will keep working for as long as 8,000 hours.

One of the main challenges of the project was finding a material that could survive long-term contact with the refrigerant, which is contained in the compressor itself, and it took several prototypes before designers settled on Vespel and Teflon. Another hurdle was fitting the new parts into the established configuration.

The first version of the oil-less compressor now sits attached to a centrifuge on the space station. It's been tested to make sure it works, but has not yet been used for any experiments.

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Title Annotation:lubricants
Author:Abrams, Michael
Publication:Mechanical Engineering-CIME
Article Type:Brief article
Geographic Code:1USA
Date:Apr 1, 2006
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