U.S. Spacewalkers Repair ISS Solar Power Channel, Start Reconfigurations

NASA astronauts Reid Wiseman and Barry "Butch" Wilmore successfully replaced a failed sequential shunt unit during a spacewalk outside the International Space Station on Wednesday, then moved on to relocate tool holders, cameras, lights and antennas.

The spacewalkers encountered several balky bolts, which threatened to slow or interrupt an ambitious list of secondary tasks.

They battled the difficulties with a combination of power and hand tools to restore an ISS solar power channel that has been shut down since May 8 by an internal short and then clear the path for external reconfigurations next year that will accommodate a pair of docking ports for new Commercial Crew Program spacecraft.

NASA astronauts Reid Wiseman, foreground, and Barry "Butch" Wilmore move tool a stand, replace a camera and relocate a video antenna outside the International Space Station's U. S. segment. NASA

Boeing and SpaceX received space agency contracts last month to complete development of their CST-100 and crewed Dragon capsules in time for launchings by late 2017.

The scheduled 6 1/2 hour spacewalk got under way at 8:16 a.m., EDT.

The excursion was the second in a new round of NASA scheduled spacewalks that will extend into next year to prepare the ISS for the arrivals of new international docking adapters for Boeing's CST-100 and SpaceX's crewed Dragon. NASA anticipates launchings of the new crew transports by late 2017.

Wednesday's spacewalk sent the two men scrambling from the far starboard to the far port side of the station's near 360-foot-long solar power truss.

Scheduled ISS spacewalks resumed Oct. 7, following a hiatus to address the cooling system leak that permitted water to flow into the helmet of the NASA space suit worn by European Space Agency astronaut Luca Parmitano on July 16, 2013, and a more recent problem with the rechargeable space suit batteries.

Wiseman and ESA astronaut Alexander Gerst resumed the scheduled outings last week by relocating a large thermal control system pump module that failed late last year. A pair of emergency spacewalks in December -- permitted during the haitus -- replaced the pump with a spare but left the old hardware in a temporary location.

NASA's Mission Control said the successful replacement of the sequential shunt unit on Wednesday should lead to recovery of the disabled solar power channel by Thursday. The station's four large solar power modules generate electricity through eight power channels in all.