Realtime Coverage of U.S. EVA-16


4:00 p.m. EDT Update: Spacewalk ends

Astronauts Tracy Caldwell Dyson and Douglas Wheelock began repressurizing the International Space Station's Quest airlock at 3:53 p.m. to officially close out a seven-hour 26-minute spacewalk.

This was the 149th EVA devoted to station assembly and maintenance since construction began in 1998, the 13th so far this year, the fifth for Wheelock and the second for Caldwell Dyson.

Total space station EVA time now stands at 937 hours and four minutes. Wheelock's total through five spacewalks is 36 hours and 10 minutes, moving him up to 27th on the list of most experienced spacewalkers. Caldwell Dyson's total through two excursions stands at 15 hours and 29 minutes.

A news briefing with space station Program Manager Mike Suffredini, Flight Director Courtenay McMillan and spacewalk officer David Beaver is expected around 5 p.m.



3:05 p.m. EDT Update: Astronauts wrap up initial work on spare pump module

Astronauts Douglas Wheelock and Tracy Caldwell Dyson have completed initial preparation of a replacement coolant pump, disconnecting three of five electrical cables and reconfiguring insulation. They had planned to loosen bolts holding the module to its storage platform, but that work was deferred.

If all goes well, the spare pump will be installed on the S1 truss during a spacewalk Sunday to complete the loop A coolant system repair.

Wheelock and Caldwell Dyson now will stow their tools and head back to the Quest airlock module to wrap up today's spacewalk.



2:00 p.m. EDT Update: Pump module mounted on attachment fixture

Douglas Wheelock mounted a failed ammonia pump module on an attachment fixture at the base of the space station's robot arm transporter at 1:55 p.m., completing a complex removal procedure.

Wheelock and Tracy Caldwell Dyson plan to close out today's spacewalk by preparing a spare pump module for installation during a third spacewalk Sunday.

The astronauts plan to loosen three of four bolts holding the spare pump in place on external stowage platform No. 2. They also plan to disconnect electrical lines before cleaning up and heading back to the Quest airlock.



1:45 p.m. EDT Update: Faulty coolant pump removed, moved to temporary storage fixture

Successfully completing a major objective, astronauts Douglas Wheelock and Tracy Caldwell Dyson unbolted and removed a faulty 780-pound ammonia coolant pump from the space station's starboard one, or S1, truss segment today after disconnecting a final ammonia line and five electrical cables.

The astronauts had problems lining up and attaching a handling fixture called an adjustable grapple bar to the pump, but they finally got it lined up and attached.



Two views of astronaut Douglas Wheelock removing a failed
pump module from the S1 truss. (Photo: NASA TV)

That cleared the way for robot arm operator Shannon Walker, working inside the Destiny lab module, to pull Wheelock, holding the pump by the grapple bar, away from the S1 truss at 1:30 p.m.

"How you doing, Wheels?" Caldwell Dyson called as Wheelock pulled the pump module from the truss.

"Doing good," he replied. "Trying to be still with this thing."

Walker then carefully repositioned the arm so Wheelock could mount the pump module on a powered payload attachment fixture at the base of the station's robot arm transporter.

Caldwell Dyson, meanwhile, was cleared to make her way to external storage platform No. 2 where she planned to loosen three of four bolts holding a spare pump module in place.

The spare pump will be installed on the S1 truss during a spacewalk Sunday.

Assuming the astronauts don't run into problems re-attaching five electrical cables and four ammonia lines, flight controllers will be able to re-activate the loop A coolant system, completing a complex repair job.



12:25 p.m. EDT Update: Astronauts, ahead of schedule, prep pump for removal

Astronaut Douglas Wheelock, anchored on the end of the space station's robot arm, has retrieved an adjustable grapple bar from external storage platform No. 2. Tracy Caldwell Dyson, meanwhile, has removed three of four bolts holding a faulty coolant pump in place on the starboard one, or S1, truss segment.

After the final bolt is removed and the grapple bar is attached to the pump module, the astronauts will move the pump to a nearby attachment fitting at the base of the space station's robot arm transporter.

Astronaut Douglas Wheelock's helmet cam view of Brazil
220 miles below. (Photo: NASA TV)


Wheelock, on the end of the station's robot arm.
(Photo: NASA TV)

Riding the arm to ESP-2 to retrieve the AGB, Wheelock took a moment to marvel at the view, thanking arm operator Shannon Walker for a smooth ride.

"I really can't in good conscience call this 'spacewalking.' This is awesome," Wheelock radioed. "Thanks, Shannon."

After the faulty pump is removed and stowed, the astronauts plan to loosen bolts holding a spare pump in place on ESP-2 before calling it a day.

Assuming that schedule holds up, Wheelock and Caldwell Dyson will attach the new pump during a spacewalk Sunday and reconnect ammonia lines and electrical cables.

Four hours into today's spacewalk, the astronauts were running about a half hour ahead of schedule.

Flight controllers looked into the possibility of going ahead and moving the new pump into place today, but there does not appear to be enough time to accommodate the additional work.

The astronauts are still protecting a block of time at the end of the spacewalk for possible decontamination procedures. There were no major leaks from a final ammonia line that was disconnected earlier but a small amount of ammonia ice could be seen escaping for a few moments. That was not considered a problem, however.



11:25 a.m. EDT Update: Electrical cables demated

Three hours into a planned six-hour spacewalk, astronaut Tracy Caldwell Dyson has disconnected five electrical cables from a faulty ammonia pump module, clearing the way for its removal from the space station's starboard one, or S1, truss.

Crewmate Douglas Wheelock, anchored to the end of the space station's robot arm, has loosened four bolts holding the pump in place. After retrieving and attaching an adjustable grapple bar, Wheelock and Caldwell plan to move the pump to a temporary storage fixture at the base of the station's robot arm transporter.



10:40 a.m. EDT Update: M3 ammonia line successfully removed

Astronaut Douglas Wheelock, applying brute force to shake a balky connector loose, successfully demated a final ammonia line from a failed coolant pump module today, setting the stage for the pump's removal and eventual replacement.

Because of a significant ammonia leak in the M3 connector during a spacewalk Saturday, Wheelock and Tracy Caldwell Dyson were unable to complete preparations for the pump's removal, leaving the line in place pending additional troubleshooting.

Today, the astronauts planned to first close a quick-disconnect fitting on the outboard end of the S1 truss to isolate the line leading to the M3 connector. But Caldwell Dyson was unable to depress a release button, preventing her from closing the outboard quick-disconnect.

Astronaut Douglas Wheelock's helmet cam view of the M3
ammonia line quick-disconnect fitting. (Photo: NASA TV)



The M3 connector, after its release from the pump module.
(Photo: NASA TV)

Flight controllers then told Wheelock, anchored to the end of the space station's robot arm, to press ahead with an attempt to simply close the leaking M3 connector in hopes that lower pressure in the line, the result of earlier ground-commanded nitrogen venting, would reduce the leakage enough to disconnect the line from the pump.

To the relief of anxious flight controllers, the connector closed easily and no major leakage was observed.

"I don't see anything leaking," Wheelock reported.

"Excellent," replied Oscar Koehler from mission control in Houston. "And Wheels, if you see any leak, we're comparing this leak to what you saw when you first did the SPD on EVA-1.

"OK, I see a couple of little snowflakes," Wheelock reported a moment later. "But I don't see anything leaking around the white band like last time. ... OK, here they start to come out now by the white band, just little snowflakes."

The leakage quickly diminished and flight controllers told Caldwell Dyson there was no need to continue work to close the outboard quick-disconnect.

"That's great news," Wheelock said.

"It's awesome," Koehler agreed.

A few moments later, with no observable leakage, engineers decided there was no need to install a vent tool to release any residual ammonia that might be trapped in the line. Wheelock was then cleared to remove M3 from the pump module.

But in keeping with M3's now-familiar behavior, Wheelock was initially unable to pry the fitting apart using a lever tool.

"We believe there may be ice in there that's keeping it from releasing," Koehler advised. "So you've got a go to ... move the QD left to right to try to shake some of that ammonia ice out of there."

After working the fitting from side to side with no success, mission control told Wheelock "you've got a go to shake violently, that's the words I was given, in all directions."

Television views from Wheelock's helmet camera showed him energetically shaking the fitting from side to side. After multiple attempts, the connector finally released and Wheelock pulled the M3 line away from the pump at 10:23 a.m.

There were no obvious signs of problems with the connector and the astronauts were cleared to press ahead with their pump removal work. Five electrical cables will be demated by Caldwell Dyson before the astronauts loosen four bolts to free the pump from the S1 truss. If all goes well, the pump will be mounted on an attachment fitting at the base of the station's robot arm transporter.



8:30 a.m. EDT Update: Spacewalk begins

Astronauts Douglas Wheelock and Tracy Caldwell Dyson, floating in the Quest airlock module, switched their spacesuits to internal battery power at 8:27 a.m. to officially kick off a planned six-hour spacewalk. The primary goal of the excursion is to remove a shorted ammonia pump module so a replacement can be installed during a spacewalk Sunday.

This is the 149th EVA devoted to space station assembly and maintenance since construction began in 1998, the 13th so far this year, the fifth overall for Wheelock and the second for Caldwell Dyson. Going into today's outing, ISS spacewalk time stood at 929 hours and 38 minutes, or 38.7 days.

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

The astronauts attempted to remove the faulty pump during a spacewalk Saturday, but one of four ammonia line quick-disconnect fittings leaked, presumably because of problems with an internal valve on the outboard side of the fitting.

Today, Wheelock will make another attempt to simply close the M3 quick-disconnect fitting. If the leak persists, the astronauts plan to close quick-disconnect valves at the inboard and outboard ends of the starboard one, or S1, truss where the pump module is located to isolate the ammonia line leading to the leaking connector.

Flight controllers earlier lowered pressure in the system and after the astronauts install a vent tool to get rid of any residual ammonia trapped in the line, the M3 quick disconnect will be closed and removed. That should clear the way for disconnection of five electrical umbilicals. After loosening four bolts, the failed pump module will be removed and temporarily mounted on a powered attach fitting at the base of the station's robot arm transporter.

If all goes well, a spare pump will be installed and reconnected during a third spacewalk Sunday.

Here is an updated timeline for today's spacewalk based on the official start time (in EDT and elapsed time; best viewed with fixed-width font):

EDT........HH...MM...EVENT

08:27 AM...00...00...Suits to battery power
08:32 AM...00...05...Post depress/airlock egress
08:47 AM...00...20...Setup
09:12 AM...00...45...EV-2: Close S1 outboard QD
09:27 AM...01...00...EV-1: Vent line routing
09:57 AM...01...30...EV-1: S0/S1 inboard jumper QD closed
10:12 AM...01...45...EV-2: M1 ammonia line restrained
10:27 AM...02...00...EV-2: Start venting
10:37 AM...02...10...EV-1: Close M2 ammonia line
11:07 AM...02...40...EV-1: Close vent tool
11:12 AM...02...45...EV-2: Vent tool cleanup
11:22 AM...02...55...EV-1: Close and demate M3 ammonia line
11:32 AM...03...05...EV-2: Cover and restrain M3
11:42 AM...03...15...EV-1: Break torque on failed pump module bolts
12:02 PM...03...35...EV-1: Retrieve adjustable grapple bar
12:02 PM...03...35...EV-2: Release failed PM electrical cables
12:32 PM...04...05...EV-2: Release failed PM bolts
12:47 PM...04...20...EV-1: Remove failed PM with AGB
12:57 PM...04...30...EV-2: Remove failed PM
01:32 PM...05...05...EV-1: Move failed PM to POA
01:42 PM...05...15...EV-2: Break torque on new PM; cleanup
02:02 PM...05...35...EV-1: Cleanup/airlock ingress
02:27 PM...06...00...Airlock pre-pressurization



8:00 a.m. EDT Update: Airlock depressurization underway

Astronauts Douglas Wheelock and Tracy Caldwell Dyson, assisted by flight engineer Shannon Walker, began depressurizing the Quest airlock module at 7:56 a.m. Today's spacewalk is expected to begin around 8:36 a.m. when the astronauts switch their spacesuits to battery power.



6:15 a.m. EDT Update: Spacewalk preparations about 30 minutes behind schedule

Astronauts Douglas Wheelock and Tracy Caldwell Dyson are running about a half hour behind schedule in their preparations for a planned six-hour spacewalk to continue space station coolant system repairs. The spacewalk had been scheduled to begin at 7:55 a.m., but could slip to around 8:30 a.m. if the current pace holds up.