Whitson, Tani Repair Problem To Power Generation System

Let there be light... onboard the International Space Station, that is. Early Wednesday afternoon, Expedition 16 Commander Peggy Whitson and Flight Engineer Dan Tani finished a seven hour, 10 minute spacewalk outside the ISS, to make repairs on the starboard side of the truss structure.

NASA reports the spacewalkers successfully removed and replaced a Bearing Motor Roll Ring Module (BMRRM) that experienced electrical failure December 8. The BMRRM, or "broom," drives the solar arrays as they tilt towards the sun, maximizing power generation.

While the panels continued to produce energy, the faulty motor prevented the panels on the station's right side from tracking the sun, curbing the station's power-generation capabilities.

Mission Control reported good electrical continuity to the new BMRRM. While spacewalkers were still outside, flight controllers completed a planned three-degree rotation and then did a 360-degree rotation of those solar wings. NASA engineers pronounced the repairs a success, stating the station's right-side solar power module is now generating enough power to support the planned deliveries of the Japanese "Kibo" science module to the station in March and April.

"Yee haw," said Whitson, when Mission Control told her the repair was successful. "Thanks a lot."

"Great. Fantastic," echoed Tani, reports The Houston Chronicle.

The excursion was somewhat riskier than other spacewalks, as the astronauts had to work in close proximity to the high-voltage solar panels. The spacewalkers could only work while the station was in darkness... as when sunlight hits the panels, dangerously high levels of electricity spike through the cables they had to handle.

The motor is part of the Beta Gimbal Assembly, which experienced electrical failures December 8. Including pauses for the daylight parts of orbit, the removal and replacement of the BMRRM took about three hours.

The second major task of the spacewalk was inspection of the starboard Solar Alpha Rotary Joint (SARJ), which causes the starboard solar wings to rotate in a paddlewheel-like motion to keep the arrays pointed toward the sun. Previous inspections revealed contamination and debris inside that joint. Eight SARJ covers were removed for Wednesday's inspection.

Station Flight Engineer Yuri Malenchenko helped the crew with suiting up and provided other support. Astronaut Tom Marshburn was the ground intravehicular officer. He was in the station flight control room in Houston's Mission Control Center, acting as spacewalk choreographer.

Once tasks their tasks were completed and after cleanup the spacewalkers re-entered the Quest airlock and closed its hatch. The beginning of repressurization at 1206 EST marked the official end of the spacewalk.

(Photo courtesy of NASA TV)

FMI: www.spaceflight.nasa.gov