HOUSTON — Discovery astronauts Steve Bowen and Al Drew safely vented a failed thermal control system pump and whipped through a list of maintenance tasks outside the International Space Station on March 2, foreshadowing a successful final mission for NASA’s fleet leader.
The 6-hr., 14-min. spacewalk was the second and final excursion planned during Discovery’s 12-day assembly and supply mission to the orbiting science laboratory. Discovery’s six astronauts are scheduled to depart March 6, and conclude Discovery’s 39th trip to orbit with a landing at NASA’s Kennedy Space Center, Fla., on March 8 at 11:36 a.m. EST.
Drew vented toxic ammonia coolant from the 780-lb. pump the spacewalkers retrieved from the station’s starboard solar power truss during their Feb. 28 excursion and relocated outside the lab’s U.S. airlock. Station managers hope the assembly can be returned to Earth for a failure analysis aboard Atlantis during the STS-135 mission this summer.
The pump’s unexplained July 31 shutdown prompted a 50% reduction in the station’s solar power output. Cooling was restored with a flurry of spacewalks by station crewmembers who scrambled to install an onboard spare.
Since docking with the station on Feb. 26, Discovery’s six astronauts have emptied the shuttle’s payload bay by transferring an equipment stowage module and external platform with spare parts to the station. Mission managers granted the fliers an extra day at the outpost to help the lab’s six U.S., Russian and Italian astronauts offload five tons of shuttle-delivered cargo.
Meanwhile, imagery experts in Mission Control completed a post-launch assessment of Discovery’s heat shielding and deemed the thermal protection acceptable for re-entry.
The March 2 spacewalk started at 10:42 a.m. EST, or nearly a half-hour late because of a leak in Bowen’s spacesuit detected during the airlock checkout. The leak was traced to a damaged O-ring seal in the suit’s carbon dioxide removal system.
Once outside, Bowen and Drew parted company to equip Canada’s Dextre robot hand with a second video camera and a tool cart with lighting, retrieve tool bags, make several insulation adjustments and troubleshoot a loose radiator support beam, among other tasks.
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