The International Space Station's starboard solar wing made two compelete revolutions without inducing excessive vibrations today, signaling unprecedented spacewalking repairs by a visiting shuttle fix-it crew worked as intended.
NASA engineers still are poring over data generated during the two-orbit test of a giant rotary joint designed to turn the 240-foot wing like a steamboat paddlewheel so it can track the sun as the station circles Earth. Doing so maximizes solar energy collection and electrical power output.
Preliminary results indicate the rotary mechanism drew much less voltage as it turned -- an indication that a spacewalking lube job and bearing replacements may have fixed the wheel-like gear, which has not been operating properly since September 2007.
"The test went very well last night," NASA astronaut Terry Virts told the station crew from NASA's Mission Control Center in Houston. "It was a pretty good reduction in rotation current."
"That is excellent news, and it shows that the efforts -- valiant efforts -- from our (spacewalking) team were well worth it," said station commander Mike Fincke.
"It was an amazing four (spacewalks). That was a lot of work those guys did, and they did well," Virts said.
"Well, we're certainly very proud of them," Fincke said.
Endeavour mission specialists Heidemarie Stefanyshyn-Piper, Steve Bowen and Shane Kimbrough cleaned and lubricated the 10-foot-diameter rotary joint during a quartet of spacewalks and they also replaced 11 of its 12 trundle bearing assemblies.
During today's test, the current generated by the motor that drives the joint drew 18 amps -- well less than the 25 amps that alarmed engineers enough to halt the automatic rotation of the mechanism in September 2007.
In comparison, current drawn by the solar wing rotary mechanism on the port side of the station's central truss typically is 13 amps.
The high voltage detected in late 2007 was an indication of internal trouble, and subsequent spacewalking inspections showed the saw-toothed gear was grinding against its bearings, creating metal shavings that fouled the joint.
The repair work done by the Endeavour astronauts is considered important to plans to increase to six the size of resident crews at the outpost. A starboard joint that can being rotated -- rather than held in stationary positions -- will generate more electricity to run station systems as well as science research experiments.
The 10 astronauts and cosmonauts on the shuttle-station complex also got some good news about a newly delivered urine processing assembly. After three start-up shutdowns and two attempts to fix it, the assembly has completed two consecutive four-hour runs without significant problems. Another run is under way now.
You can watch all the action unfold here in The Flame Trench. Simply click the NASA TV box on the righthand side of this page to launch our NASA TV viewer and round-the-clock coverage of Endeavour's mission to the station.
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