A shadowy Steve Bowen, left, and Al Drew, top, emerge from the International Space Station's
U. S. airlock to begin their second spacewalk this week. Photo Credit/NASA TV
The Discovery mission’s second spacewalk outside the International Space Station by Steve Bowen and Al Drew was underway at mid-morning on Wednesday. The start was delayed slightly by a leak found in Bowen’s space suit before he emerged from the airlock.
The agenda for the 6 1/2 hour excursion includes nearly a dozen assorted tasks, including a quick venting of the residual ammonia coolant in a failed thermal control system pump motor. Bowen and Drew retrieved the 780 pound pump from the station’s starboard solar power system truss and stowed it outside the U. S. airlock during Monday’s excursion.
Today’s outing began at 10:42 a.m., EST, or about a half hour behind schedule. The source of Bowen’s suit leak took nearly an hour to find and fix. It was in a small damaged O-ring seal in the suit’s carbon dioxide removal system.
Drew will vent about 10 pounds of ammonia from the pump, using caution not to get the hazardous chemical on his suit.
The pump failed on July 31, prompting a shutdown of half the station’s solar power generation system. Station managers hope to return the device to Earth aboard the STS-135 flight for a failure analysis. The 14-day supply mission aboard the orbiter Atlantis is manifested for a June 28 lift off. It would mark the final flight of NASA's shuttle program -- if funded by Congress.
The spacewalkers plan a range of small maintenance tasks during Wednesday’s outing. They include the installation of a video camera on Canada’s DEXTRE robotic hand, the retrieval of tool bags, the installation of external lighting and some troubleshooting on a loose radiator support beam.
Discovery lifted off on its final mission Feb. 24. The six shuttle astronauts have been parked at the station since Feb. 26. Under current scheduling, Discovery's crew will depart the outpost on March 6 and return to Earth on March 8, touching down at NASA's Kennedy Space Center at 11:36 a.m., EST.
Earlier this week, imagery experts wrapped up their post-launch analysis of Discovery’s heat shielding and found it in good shape.
So far, the shuttle crew has equipped the station with a new equipment stowage module and attached a carrier with external spare parts to the starboard truss. Inside the station on Wednesday, 10 U. S., Russian and Italian astronauts will continue unpacking five tons of cargo delivered by Discovery.