In November 2008, the Space Shuttle Endeavor visited the International Space Station to do some important repair work. A critical part of the mission was to service the station’s two rotary joints, which allow its solar-cell arrays to track the sun. Wear and damage because of friction had rendered the joints inoperable. The fix required an hours-long spacewalk and a delicate technical procedure.
But the basic idea was simple. “We sent astronauts up with a grease gun and got it moving again,” recalls Christopher DellaCorte, a senior research engineer in the Tribology & Mechanical Components Branch at NASA’s Glenn Research Center.
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