samedi 11 mai 2013

Spacewalk Under Way to Repair Ammonia Leak

ISS - International Space Station patch.

May 11, 2013

Expedition 35 Flight Engineers Chris Cassidy and Tom Marshburn began a spacewalk at 8:44 a.m. EDT Saturday to inspect and possibly replace a pump controller box on the International Space Station’s far port truss (P6) suspected of leaking ammonia coolant. Station managers and the international partners approved plans late Friday to conduct the spacewalk after a day-long review of procedures and the crew’s preparations to support the excursion.

Expedition 35 spacewalkers Chris Cassidy and Tom Marshburn. Credit: NASA TV

A leak of ammonia coolant from the area near or at the location of a Pump and Flow Control Subassembly was detected on Thursday, prompting engineers and flight controllers to begin plans to support the spacewalk. The device contains the mechanical systems that drive the cooling functions for the port truss.

Image above: Ammonia flakes are visible near the International Space Station's P6 truss on Thursday. Credit: NASA TV.

The P6 truss was launched to the station as the oldest component of the station’s backbone aboard the shuttle Endeavour on the STS-97 mission in November 2000. It was relocated from its original installation position to the far left side of the station during the STS-120 mission of the shuttle Discovery in October/November 2007.

The spacewalk is the 168th in support of the assembly and maintenance of the space station and the third for both Cassidy and Marshburn, who conducted two spacewalks together during the STS-127 mission of the shuttle Endeavour to the station in July 2009.

Image above: At 8:15 AM Eastern, NASA astronauts Tom Marshburn and Chris Cassidy will leave the International Space Station to inspect and possibly replace a pump suspected of leaking ammonia coolant. This picture of astronauts Suni Williams and Robert Curbeam working on a solar array in 2006 gives us a sense of where Marshburn and Cassidy will be working. Credit: NASA TV.

Cassidy is designated as Extravehicular crewmember 1 (EV 1) whose spacesuit will be distinguished by red stripes. Marshburn is designed Extravehicular crewmember 2 (EV 2), and is wearing the suit with no stripes.

ISS Active Cooling System. Credit: / Karl Tate

Expedition 35 Commander Chris Hadfield of the Canadian Space Agency is serving as the intravehicular crewmember or IV, choreographing the suit up of the spacewalkers and their tasks outside.

Image above: The astronauts have removed the suspect pump flow control subassembly and are now taking a look to see if they can find any smoking gun on the ammonia leak. Credit: NASA TV.

The spacewalk is expected to last around 6 ½ hours. A post-spacewalk briefing will be broadcast on NASA TV no earlier than 4:30 p.m. EDT.

Related links:

Watch NASA TV spacewalk live:

Read more about the station's radiators:

ATCS overview from Boeing:

Read more about Expedition 35:

Read more about Expedition 36:

Images (mentioned), Text, Credit: NASA.