Leak in Russian spacesuit O2 bottle forces cancellation

A spacewalk intended to replace a faulty circuit breaker on the exterior of the International Space Station was cut short when the primary oxygen bottle on Astronaut Mike Fincke's Russian space suit began losing pressure faster than expected. The overall pressure in Fincke's suit remained stable at all times and he was not in danger. A backup oxygen tank available on his suit was not needed.

Fincke and Expedition 9 Commander Gennady Padalka opened the Pirs docking compartment hatch at 16:56 CDT. Immediately after Fincke floated out of the airlock, flight controllers in Moscow saw readings that indicated the primary oxygen bottle on Fincke's suit was losing pressure.

The two spacewalkers returned to the airlock and closed the hatch about 14 minutes later. After conducting preliminary troubleshooting activities, Padalka and Fincke were asked to remove the Orlan-M spacesuits and assist with troubleshooting of Fincke's suit. Russian flight controllers could not immediately determine the cause of the malfunction.

Fincke and Padalka then climbed out of the suits, returned to the Station's living quarters and began working with ground controllers to reconfigure the Station's systems for normal operations. The duration of Fincke and Padalka's spacewalk was 14 minutes, 22 seconds.

Mission managers in Houston and Moscow agreed to conduct further evaluation of the problem before setting a new target date for the spacewalk. The earliest the spacewalk could now be performed is June 29 based on Russian ground communications coverage.

Fincke told Mission Control in Houston that he was pleased flight controllers in Moscow had discovered the oxygen tank problem so quickly, and thanked both control teams for their efforts. He indicated the crew would sleep late tomorrow, and then resume their regular sleep schedule until it was time to prepare for another spacewalk.

The spacewalk's goal is to replace a Remote Power Controller Module (RPCM) which houses a faulty circuit breaker, through which power is routed to one of the Control Moment Gyroscopes (CMGs).

There are four CMGs in the Station's Z1 truss. They control the orientation of the ISS in space.  CMG 1 failed about two years ago, and will be replaced during the next Shuttle mission. CMG 2 was taken off line by the April 21 failure of the circuit breaker and should be restored by the RPCM's replacement. Meanwhile, two functioning CMGs adequately control the station's attitude.

FMI: http://spaceflight.nasa.gov/, http://scipoc.msfc.nasa.gov/