Realtime Coverage of U.S. EVA-17

1:50 PM EDT: Spacewalk ends

Astronauts Tracy Caldwell Dyson and Douglas Wheelock began repressurizing the Quest airlock module at 1:40 p.m., officially ending a seven-hour 20-minute space station repair spacewalk.

It was the third spacewalk by Wheelock and Caldwell Dyson to replace an ammonia cooling pump, a complex job that ended up requiring 22 hours and 49 minutes of EVA time to complete.

Wheelock's total through six career spacewalks now stands at 43 hours and 30 minutes, moving him up to 10th on the list of most experienced spacewalkers. Total EVA time for station assembly and maintenance now stands at 944 hours and 24 minutes - 39.4 days - through 150 spacewalks.

A wrapup story will be posted shortly.

1:20 PM EDT: Cable installation deferred; crew told to wrap up EVA

With their spacewalk running a bit longer than planned, flight controllers told astronauts Douglas Wheelock and Tracy Caldwell Dyson to skip the planned installation of a power cable between the Quest airlock and the Unity module and to head back to the airlock to wrap up the excursion.

The primary goal of the spacewalk -- installation of a spare ammonia pump module as part of a complex coolant system repair -- was successful. The extension cable installation will be deferred to a future spacewalk.

1:10 PM EDT: Controllers assess time needed for cable installation

Astronauts Douglas Wheelock and Tracy Caldwell Dyson have completed work to collect and inventory the tools and equipment they used to install a replacement ammonia cooling system pump.

The only task remaining on today's agenda is to install an extension cord between the Quest airlock and the International Space Station's central Unity module that is needed before the attachment of a cargo module during the next shuttle visit in November.

But the time needed to pack up tools and equipment used for the installation of the spare ammonia pump ran a bit longer than expected and it's not yet clear whether the astronauts will have time to fully install the cable before heading back to the Quest airlock to end the spacewalk.

11:15 AM EDT: Coolant lines connected to replacement pump

Astronaut Douglas Wheelock successfully connected four ammonia lines to a replacement pump module, wrapping up work to replace a faulty pump that knocked one of the International Space Station's two coolant loops out of action July 31.

The fourth ammonia line was connected at 10:41 a.m. and after installing positioning devices, Wheelock opened quick-disconnect valves in the lines to permit the normal flow of ammonia coolant into and out of the new pump module.

To the relief of flight controllers, no ammonia leaks were spotted.

"And Wheels, just to confirm, we did not see any ammonia come out today, amazingly," Oscar Koehler said from mission control. "So if you can confirm you saw no ammonia during any of the QD ops we are go with no ammonia tests at the end of the EVA."

"OK. I did not, Oscar," Wheelock replied. "I did at one time, though, saw what I thought were just a couple of little snowflakes. But I'm not able to confirm that. There was no leak or anything."

A few moments later, Wheelock showed off a cue card on his spacesuit's left wrist that thanked flight controllers and ended with the words "Game over!"

While no one suspected a leak, flight controllers decided the spacewalkers would be in direct sunlight long enough during the remainder of the spacewalk to bake out any ammonia ice that might have been present before Wheelock and Caldwell Dyson return to the Quest airlock at the end of the excursion.

The pump installation capped a complex three-spacewalk repair job that was required in the wake of a July 31 pump failure that took down half the space station's cooling, triggering a widespread power down to keep critical equipment from overheating.

Two of four ammonia lines attached to a replacement pump module.
(Photo: NASA TV)

The view from Wheelock's helmet cam, showing all four
ammonia lines in place with valves opened. (Photo: NASA TV)

Flight controllers earlier verified the electrical health of the replacement pump and now will carry out a complex series of steps to reactivate coolant loop A, work that is expected to take several days to complete.

Wheelock and Caldwell Dyson, meanwhile, planned to clean up the worksite on the S1 truss, putting insulation blankets back in place and rounding up their tools and equipment.

The only remaining task is to run an extension cord from the Quest airlock to the Earth-facing side of the Unity module that needs to be in place before attachment of a cargo module during a shuttle visit in November.

Wheelock and Caldwell Dyson had planned to install that cable during a spacewalk Aug. 5, but that excursion was canceled in the wake of the loop A pump failure.

9:30 AM EDT: Spare ammonia pump installed in S1 truss

Astronaut Douglas Wheelock, anchored to the end of the space station's robot arm, manhandled a 780-pound ammonia pump into the starboard one, or S1, truss segment, replacing a faulty pump that was removed during a spacewalk last week.

"Like butta," Wheelock said as the module slid into the truss.

"Like butta," Caldwell Dyson agreed.

"OK, I think we're in there," Wheelock reported a moment later.

"Outstanding," replied robot arm operator Shannon Walker.

"Good job, guys," Oscar Koehler called from mission control in Houston.

Astronaut Douglas Wheelock and Tracy Caldwell Dyson maneuver a new
ammonia pump into place during orbital darkness. A faulty pump
removed earlier can be seen in the background. (Photo: NASA TV)

While Wheelock bolted the new pump in place, Caldwell Dyson connected five electrical and data cables, completing the work at 9:04 a.m. A few minutes later, flight controllers powered up the pump module, the oldest of four spares aboard the station, to verify electrical continuity and to spin up the pump's drive shaft for a brief test.

"The bump test has been successful," Koehler called from Houston.

"Oh, sweet! That's awesome news," Wheelock replied.

Wheelock then pressed ahead with work to re-connect ammonia coolant lines and to disconnect a pressure-regulating "jumper box" that was installed earlier.

Astronaut Douglas Wheelock's helmet cam view of four ammonia
connectors on a replacement pump being moved into place in the
S1 truss. (Photo: NASA TV)

8:15 AM EDT Update: Spare pump module unbolted from stowage platform

Astronauts Tracy Caldwell Dyson and Douglas Wheelock, working at external stowage platform No. 2, have unbolted a spare ammonia pump module in preparation for installing it in the space station's starboard one, or S1, truss segment.

Douglas Wheelock uses a torque multiplier to loosen a tight bolt, one of
four holding a spare pump module in place on a stowage platform.
(Photo: NASA TV)

Wheelock broke torque on four bolts holding the pump module in place, using a torque multiplier to loosen a particularly tight one, while Caldwell Dyson installed protective caps on a variety of connectors.

"OK, Oscar, bolt three's released," Wheelock radioed at 8 a.m. after loosening the final bolt holding the pump in place.

A moment later, Oscar Koehler in mission control gave the spacewalkers permission to remove the pump.

Anchored to the end of the space station's robot arm, Wheelock held the 780-pound pump while astronaut Shannon Walker, operating the space crane from inside the Destiny laboratory module, pulled him away from external stowage platform No. 2.

Once the new pump module is in position at the S1 truss, Wheelock will use a power tool to tighten four bolts to lock it in place. Caldwell Dyson, meanwhile, will attach five electrical cables.

After flight controllers verify electrical continuity, Wheelock will begin work to connect four ammonia lines, including two that were attached to a pressure-regulating "jumper box" during the crew's first spacewalk Aug. 7.

6:30 AM EDT Update: Spacewalk begins

Running well ahead of schedule, astronauts Tracy Caldwell Dyson and Douglas Wheelock switched their spacesuits to battery power at 6:20 a.m. EDT to officially kick off a planned six-and-a-half-hour spacewalk to install a spare ammonia pump in the International Space Station's cooling system.

For identification, Wheelock, call sign EV-1, is wearing a suit with red stripes around the legs and will be using helmet camera No. 19. Caldwell Dyson, EV-2, is wearing an unmarked suit and will be using helmet cam No. 20.

The U.S. segment of the International Space Station features two coolant loops that circulate ammonia through huge radiators to dissipate the heat generated by the lab's electronics. The ammonia pump in loop A, mounted in the starboard one, or S1, truss segment, failed July 31, forcing the six-member crew to implement a widespread powerdown.

Wheelock and Caldwell Dyson originally planned two spacewalks to repair coolant loop A, one to remove the old pump and install a spare and a second to complete the required ammonia line connections. But during their first excursion Aug. 7, one of four ammonia lines leaked, preventing the faulty pump's removal.

Before a second spacewalk Aug. 11, flight controllers lowered pressure in the line to stop the leak and Wheelock was able to disconnect the balky M3 connector. The astronauts then unbolted the failed pump and Wheelock, anchored to the end of the station's robot arm, moved it to an attachment fitting at the base of the arm's mobile transporter.

The primary goals of today's spacewalk are to remove a spare pump module from external stowage platform No. 2, install it in the S1 truss segment and reconnect the ammonia lines and five electrical cables. The spare pump, launched to the station in 2006, is the oldest of four stored aboard the space station as a hedge against coolant system failures.

If time is available, the astronauts will install an electrical cable between the Quest airlock and the Unity module that is required before attachment of a cargo module during a shuttle flight in November.

Here is an updated spacewalk timeline (in EDT and elapsed time; best viewed with fixed-width font):


06:20 AM...00...00...Suits to battery power
06:25 AM...00...05...Post depress/airlock egress
06:40 AM...00...20...EV-1: Tether swap; ingress robot arm (SSRMS);
.....................loosen four bolts on spare pump module (PM);
.....................release three bolts
06:40 AM...00...20...EV-2: Assist EV-1; remove caps
07:40 AM...01...20...EV-1: Release final bolt; remove spare PM from
.....................external stowage platform No. 2 (ESP-2)
07:40 AM...01...20...EV-2: Assist EV-1; cleanup ESP-2
08:10 AM...01...50...EV-1: PM install in S1 truss; engage four bolts
08:10 AM...01...50...EV-2: Mate electrical cables
09:10 AM...02...50...EV-1: Mate PM quick disconnects (QDs); open valves;
.....................install SPDs
09:10 AM...02...50...EV-2: Assist with QDs
10:35 AM...04...15...EV-1: Retrieve vent tool, PM stowage bags;
.....................move to ESP-2
10:35 AM...04...15...EV-2: Cleanup S1 tethers; couple CETA carts
11:05 AM...04...45...EV-1: Remove SSRMS foot restraint; install on ESP-2
11:35 AM...05...15...EV-1: Install J612 extension cable between Quest
.....................and Unity for cargo module attachment during
.....................November shuttle flight
11:35 AM...05...15...EV-2: J612 extension cable install
12:20 PM...06...00...Cleanup/airlock ingress
12:45 PM...06...25...Airlock pre-pressurization

This is the 150th EVA devoted to space station assembly and maintenance since construction began in 1998, the 14th so far this year, the sixth overall for Wheelock and the third for Caldwell Dyson. Going into today's outing, ISS spacewalk time stood at 937 hours and four minutes, or 39 days.