Preliminary timeline for pump replacement spacewalk (EVA-1)
Flight planners at the Johnson Space Center are continuing to fine tune the timeline for a planned spacewalk Friday by Expedition 24 astronauts Tracy Caldwell Dyson and Douglas Wheelock to replace a faulty ammonia pump that failed Saturday, shutting down one of the space station's two primary coolant loops.
Under the current plan, Wheelock, call sign EV-1, and Caldwell Dyson, EV-2, will switch their spacesuits to battery power at 6:55 a.m. Friday, officially kicking off a planned seven-hour spacewalk. It will be the fourth EVA for Wheelock and the first for Caldwell Dyson.
The primary objectives of the spacewalk are to remove the faulty 780-pound pump module; temporarily stow it on a nearby payload attach fitting; and install the new pump module on the starboard one - S1 - truss segment on the right side of the International Space Station.
Viewed from just ahead of the International Space Station, the faulty loop A
pump module -- PM1 -- is located in the starboard one, or S1, truss segment.
(Credit: NASA)
Along with unbolting the faulty pump, the astronauts also will have to demate electrical cables and four ammonia lines. The first two ammonia lines to be disconnected - M3 and M4 - will be connected to a "jumper box" that will prevent the loop A coolant system from over pressurizing during temperature swings in orbit. After installing the new pump module, the astronauts will reconnect the data and electrical lines.
During a second spacewalk Monday, Wheelock and Caldwell Dyson will reconnect the ammonia lines to finish the repair.
Four ammonia lines leading to the faulty pump module must be disconnected,
along with bolts and electrical cables. (Credit: NASA)
The timeline for Friday's spacewalk may change pending additional analysis at the Johnson Space Center in Houston, but here is a preliminary version (in EDT and elapsed time):
Engineers at the Johnson Space Center are refining guidelines for the spacewalk, including what to do in the event of ammonia leaks or problems mating/demating any of the fluid lines. Even though the loop A coolant system is out of action until repairs are complete, the crew should have normal use of the station's robot arm -- Wheelock will ride on the end of the arm during the EVA while Caldwell Dyson will free float -- and near-normal television views are expected.
Under the current plan, Wheelock, call sign EV-1, and Caldwell Dyson, EV-2, will switch their spacesuits to battery power at 6:55 a.m. Friday, officially kicking off a planned seven-hour spacewalk. It will be the fourth EVA for Wheelock and the first for Caldwell Dyson.
The primary objectives of the spacewalk are to remove the faulty 780-pound pump module; temporarily stow it on a nearby payload attach fitting; and install the new pump module on the starboard one - S1 - truss segment on the right side of the International Space Station.
pump module -- PM1 -- is located in the starboard one, or S1, truss segment.
(Credit: NASA)
Along with unbolting the faulty pump, the astronauts also will have to demate electrical cables and four ammonia lines. The first two ammonia lines to be disconnected - M3 and M4 - will be connected to a "jumper box" that will prevent the loop A coolant system from over pressurizing during temperature swings in orbit. After installing the new pump module, the astronauts will reconnect the data and electrical lines.
During a second spacewalk Monday, Wheelock and Caldwell Dyson will reconnect the ammonia lines to finish the repair.
along with bolts and electrical cables. (Credit: NASA)
The timeline for Friday's spacewalk may change pending additional analysis at the Johnson Space Center in Houston, but here is a preliminary version (in EDT and elapsed time):
EDT........HH...MM...EVENT
08/06/10
06:55 AM...00...00...Spacesuits to battery power
07:00 AM...00...05...Post depress/airlock egress
07:25 AM...00...30...Tool and tether setup
07:45 AM...00...50...EV-1: Pump module (PM) removal preps
07:55 AM...01...00...EV-2: CETA cart preps
08:35 AM...01...40...EV-1: Station arm (SSRMS) prep and ingress
08:45 AM...01...50...EV-2: PM jumper vent
09:00 AM...02...05...Initial PM quick-disconnect (QD) operations
09:30 AM...02...35...QD demate
09:50 AM...02...55...Thermal shrouds on all QDs
10:05 AM...03...10...EV-1: Retrieve AGB (adjustable grapple bar)
10:10 AM...03...15...EV-2: Prep failed PM for removal from S1 truss
10:50 AM...03...55...Install AGB on failed PM
11:10 AM...04...15...EV-1: Failed PM moved to payload attachment fitting
11:10 AM...04...15...EV-2: Spare PM preps
11:30 AM...04...35...EV-1: Spare PM preps
11:50 AM...04...55...BINGO for spare PM removal
12:20 PM...05...25...Remove spare PM from external storage platform No. 2
12:50 PM...05...55...Install spare PM in S1 truss
01:25 PM...06...30...Cleanup and ingress
01:50 PM...06...55...Pre-airlock repress
01:55 PM...07...00...Airlock repress
Engineers at the Johnson Space Center are refining guidelines for the spacewalk, including what to do in the event of ammonia leaks or problems mating/demating any of the fluid lines. Even though the loop A coolant system is out of action until repairs are complete, the crew should have normal use of the station's robot arm -- Wheelock will ride on the end of the arm during the EVA while Caldwell Dyson will free float -- and near-normal television views are expected.