ISS Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson to Perform Second of Three Spacewalks Wednesday

August 9, 2010

Flight controllers and engineers continue meetings to review the results from the first spacewalk conducted Saturday by International Space Station Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson and to plan for the second of what now will be three spacewalks to complete the replacement of a failed pump module on the station’s starboard truss.

In the International Space Station’s Quest airlock, Expedition 24 Flight Engineer Doug Wheelock works on a spacesuit in preparation for the second spacewalk to remove a failed ammonia pump module on the station's S1 Truss. Credit: NASA TV

In the wake of an eight-hour, three-minute spacewalk Saturday that fell short of removing the failed pump module due to a leak in the fourth of four ammonia line connectors hooked up to the old pump, mission operations and station program officials laid out a series of procedures for Wheelock and Caldwell Dyson to perform at the beginning of the second spacewalk Wednesday designed to greatly reduce, or eliminate the possibility of ammonia leaking from the final fluid connector – called M3 – when it is demated to set the stage for the failed pump to be removed from the truss.

The plan would call for Wheelock and Caldwell Dyson to close other quick disconnect lines where the S1 and S0 trusses meet that will isolate ammonia upstream in the system from the final connector, preventing any recurrence of leakage while the new pump module is being installed. Additional work to configure lines and valves would be conducted by the spacewalkers prior to the final electrical demating of the old pump so it can be parked on a stowage bracket on the station’s Mobile Base System.

The goal Wednesday will be to remove the old pump and stow it on a payload attachment bracket on the Mobile Base System on the station’s truss while preparing the replacement pump for its removal from a stowage platform adjacent to the Quest airlock and its installation on the truss during a third spacewalk targeted for no earlier than next Sunday.

Mission and station managers are continuing meetings today to prepare for the second spacewalk before the station Mission Management Team meets Tuesday morning to provide its final approval to proceed.

The station’s systems remain in good condition operating on the second of two cooling loops available for the complex and the crew is well rested following Saturday’s spacewalk, spending the last two days recharging spacesuit batteries, reviewing spacewalk procedures and configuring tools for Wednesday’s excursion.