U. S., Japanese Astronauts Team for Space Station Spacewalk
U. S.and Japanese astronauts attempted to isolate a small but growing thermal control system leak outside the International Space Station during a spacewalk Thursday that spanned nearly seven hours.
The excursion took NASA astronaut Sunita Williams, the station’s commander, and Japanese astronaut Akihiko Hoshide to the far port side of the station’s 356 foot long solar power truss.
At the work site on the P-6 solar power module, the spacewalkers isolated one of two cooling loops in a leaky photovoltaic radiator and re-routed ammonia coolant to a backup radiator that was deactivated six years ago and subsequently retracted, covered and secured.
The spacewalkers succeeded in avoiding contact with all but a few flakes of the toxic ammonia coolant as they reconfigured cooling lines and prepared the backup cooling loop, the 45-foot-long trailing thermal control radiator, for its re-deployment.
“We are basking in the moment,” NASA’s Mission Control informed Williams and Hoshide as the backup extended over 10 minutes and soon began to circulate ammonia. “You guys totally rock.”
Ground-based station engineers will attempt to pinpoint the source of the PVR ammonia loss that was first noted in 2007. In June, the leak rate increased greatly. The loss, perhaps caused by a strike from orbital debris or a crack, threatens to interrupt use of the 2B power channel, one of eight that distribute solar generated electricity throughout the station.
A future spacewalk to implement new repairs is likely. In the meantime, the backup radiator introduces more coolant to the system to temporarily “feed” the leak, if necessary, allowing 2B operations to continue.
Williams and Hoshide teamed up for spacewalks on Aug. 30 and Sept. 5 to replace a failing main bus switching unit on the station. They are scheduled to join cosmonaut Yuri Malenchenko for their return to Earth on Nov. 19 aboard Russia’s 31 Soyuz spacecraft now docked to the six-person orbiting science lab.