November 2, 2012
Expedition 33 Crew Complete Six Hour Plus Spacewalk
Lawrence LeBlond for redOrbit.com - Your Universe Online
Expedition 33 Commander Sunita Williams and Flight Engineer Akihiko Hoshide completed a scheduled spacewalk on Thursday (Nov. 1). The mission, which began at 8:29 a.m. EDT, was scheduled to repair an ammonia leak on the International Space Station´s (ISS) port side truss.Williams and Hoshide ventured outside the station to configure the 2B solar array power channel´s photovoltaic thermal control system (PVTCS) to allow for ground-based troubleshooting of an ammonia leak in one of the station´s radiators. After successfully configuring the PVTCS and rerouting ammonia coolant lines to a backup radiator, Williams and Hoshide returned to the safety of the station at 3:07 p.m.--the walk lasted 6 hours and 38 minutes.
Their work should allow flight controllers at Mission Control to determine in the coming days whether the radiator was the source of the ammonia leakage. Mission Control will continue to monitor telemetry to see if the leak continues.
If the rerouting procedure stops the leak, flight controllers will evaluate the situation and decide whether to leave the fix as-is or replace the PVTCS radiator on a future spacewalk. If the leak does continue, additional troubleshooting will be needed.
A likely reason the leak occurred is contact with a small piece of space junk that penetrated the radiator or part of its system. Another scenario is that the equipment just cracked under pressure due to age--the orbiting lab has been in space for 12 years.
The radiators are needed to dissipate heat generated by electronic equipment aboard the station. Williams and Hoshide took precautions to avoid contamination form the toxic ammonia coolant. During the procedure a few frozen ammonia flakes harmlessly struck Hoshide´s helmet.
This was not a new issue for the radiator system on the port side of the space station--a small leak was detected in 2007. Astronauts ventured outside the station last year to shore up the system and add extra coolant. But this past summer the leakage increased fourfold. Without intervention, the affected power channel could have gone offline by the end of this year.
Thursday´s spacewalk put Williams into the No. 5 position of most experienced spacewalkers. In all she has spent 50 hours and 40 minutes over seven spacewalks, the most by a woman. This was Hoshide´s third spacewalk, with a total of 21 hours and 23 minutes, the most by a Japanese astronaut.
This spacewalk mission was the 166th in support of station assembly, totaling just over 1,049 hours--the equivalent of 44 days.
Today also marks an anniversary for the International Space Station--it has been continuously manned for 12 years (since Nov. 2, 2000).