Keep the shuttle flying: Fwd: Astronauts complete Christmas Eve EVA

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: December 25, 2013 4:29:21 PM CST
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: Astronauts complete Christmas Eve EVA

Station's Replacement Pump Successfully Restarted
Dec. 24, 2013
NASA astronaut Rick Mastracchio participates in the first Expedition 38 spacewalk designed to troubleshoot a faulty coolant pump on the International Space Station.
Image Credit: NASA

Following two spacewalks to replace a degraded pump module on the truss, or backbone, of the International Space Station, flight controllers in the Mission Control Center at NASA's Johnson Space Center in Houston successfully restarted the new pump Tuesday night.
The pump module controls the flow of ammonia through cooling loops and radiators outside the space station, and, combined with water-based cooling loops inside the station, removes excess heat into the vacuum of space.
The new pump now is considered fully functional, but it will take some time to fully reintegrate the pump and Loop A of the two-loop external cooling system. Teams at mission control are following a schedule that should allow the restored cooling loop to be fully activated and integrated into the station's cooling system on Christmas Day, Dec. 25.
Electrical systems that depend on cooling from Loop A will be repowered or moved back from temporary support on Loop B gradually on Thursday, Friday and throughout the weekend.
Expedition 38 Flight Engineers Mike Hopkins and Rick Mastracchio removed the degraded pump module during a 5 hour, 28 minute spacewalk Saturday, Dec. 22. They retrieved a replacement pump from an external stowage platform near the end of the station's backbone, and installed it during a 7 hour, 30 minute spacewalk on Christmas eve, Dec. 24.
› Read more about the Dec. 24 spacewalk
› Read more about the Dec. 22 spacewalk
Engineers at mission control sent a series of commands to the new pump module at the end of Tuesday's spacewalk to ensure that ammonia – an excellent thermal conductor – was flowing to the new pump module. Beginning about 4:30 p.m. EST today, remote commands started the process of pressurizing the new pump. Reactivation of the pump is now complete, and it is performing its job regulating the flow and temperature of the ammonia in Loop A of the two-loop cooling system.
On Saturday, the crew had moved the old pump module to a temporary stowage platform on a rail car on the station's mobile base system, where it can remain indefinitely.

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Repair gives ISS a cool gift
Spacewalkers fix faulty system just in time for Christmas
Dec. 24, 2013 5:46 PM |

Astronauts on rare Christmas Eve spacewalk: Two space station astronauts ventured out on a rare Christmas Eve spacewalk Tuesday, hoping to wrap up urgent repairs to a cooling system. Posted Dec. 24, 2013
Written by
James Dean
FLORIDA TODAY
Zoom
In this image taken from video provided by NASA, astronauts Rick Mastracchio, top, and Michael Hopkins work to repair an external cooling line on the International Space Station on Christmas Eve. / AP
Spacewalkers on Tuesday delivered a welcome Christmas gift to the International Space Station, completing repairs that were expected to fully restore the outpost's hobbled cooling system.
Astronauts Mike Hopkins and Rick Mastracchio retrieved and installed a spare coolant pump, a refrigerator-sized white box that appeared to lack only a colorful bow to fit the holiday season.
Full activation of the new pump module was planned late Tuesday, but it passed a preliminary test during the spacewalk, which lasted seven hours and 30 minutes.
"Houston, you got yourself a new pump module, congratulations," Hopkins radioed after making the final electrical connection.
"It's the best Christmas ever, thanks guys," said Doug Wheelock, an astronaut working with the crew from Mission Control, as the spacewalk wrapped up.
Today, teams on the ground hoped to start powering up non-critical systems that were shut down two weeks ago, after the failure of a valve that regulated temperatures in one of two coolant loops outside the station.
The six-person Expedition 38 crew was never in danger, but the Dec. 11 malfunction left the orbiting research complex vulnerable to more serious breakdowns, a position NASA did not want to remain in long.
Hopkins and Mastracchio removed the faulty pump during a five-and-a-half hour spacewalk on Saturday, then installed one of three available spares on Tuesday.
It was NASA's second Christmas Eve spacewalk, following one in 1999 to service the Hubble Space Telescope.
And the repairs unfolded 45 years after Apollo 8 astronauts beamed the famous "Earthrise" image back from orbit around the moon and read verses from the Book of Genesis.
"We close with good night, good luck, a Merry Christmas — and God bless all of you, all of you on the good Earth," Frank Borman, the commander of that mission, said then.
Tuesday's excursion included some dramatic views of its own, as Hopkins moved the pump while positioned on the end of the station's 58-foot robotic arm, flying against a backdrop of blue oceans and white cloud formations circling 260 miles below.
"Beautiful view," said Hopkins, who was performing his second spacewalk, to Mastracchio's eighth.
The effort's success briefly appeared in doubt as the duo struggled to connect one of four ammonia coolant hoses to the newly installed pump module.
In the process, ammonia crystals spurted from the lines, enveloping them in small particles and some larger chunks of potentially dangerous "snow."
As a standard precaution, the spacewalkers took time to "bake out" any ammonia that might have stuck to their suits, so they did not track the highly toxic substance back inside the station.
The spacewalk was the 176th supporting assembly and maintenance of the 15-year-old ISS, and one more is scheduled this year that is unrelated to the cooling system repairs.
Russian cosmonauts Oleg Kotov and Sergey Ryazanskiy plan to head outside Friday morning.
Contact Dean at 321-242-3668 or jdean@floridatoday.com.

Copyright © 2013 www.floridatoday.com. All rights reserved.

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Realtime coverage of U.S. EVA-25
12/24/2013 03:09 PM
By WILLIAM HARWOOD
CBS News

03:00 PM EST, 12/24/13: Replacement pump passes 'aliveness' test; spacewalk ends

Two astronauts successfully installed a replacement coolant pump aboard the International Space Station Tuesday, wrapping up a high-stakes two-spacewalk repair job and clearing the way for flight controllers to re-activate a critical coolant system.

"We'd just like to say thanks to all the great folks doing all this hard work to get this space station back up and running," spacewalker Rick Mastracchio radioed as he returned to the Quest airlock module.

"No, thank you guys," astronaut Doug Wheelock replied from mission control in Houston. "It's the best Christmas ever. Thanks, guys."

"Yeah, I'd just like to add to that," Mike Hopkins said from the airlock. "Fantastic work, Merry Christmas to everybody. It took a couple of licks to get her done, but we got it."
Astronaut Mike Hopkins, anchored to the end of the International Space Station's robot arm, inspects a new pump module after ammonia coolant lines and electrical cables were connected. A quick test showed the pump assembly was in good health, clearing the way for flight controllers to restart coolant loop A, one of two used to dissipate heat generated by the station's electronics. (Credit: NASA TV)

The only problem of any significance during the seven-hour 30-minute spacewalk was trouble getting one of four ammonia lines disconnected from a so-called jumper box where it was temporarily plugged in during a spacewalk Saturday.

Hopkins and Mastracchio finally freed a quick-disconnect fitting holding the half-inch line in place, and were sprayed with ammonia ice crystals trapped in the connector. The toxic chemical posed no threat to the astronauts but they spent a few extra minutes in vacuum to ensure any ice stuck to their suits had time to dissipate before they re-entered the station.

The ammonia contamination barely slowed the astronauts down. After freeing the stuck line, Hopkins and Mastracchio finished hooking up all four ammonia lines to the replacement pump module and plugged in five electrical cables. Flight controllers then carried out a so-called "bump" test, briefly spinning up the pump and verifying the operation of internal valves.

"Good news! The thermal control officer reports a good bump start test on the newly installed pump module," NASA's mission control commentator, Rob Navias, reported. "We have a pump that is alive and well."

Later today, flight controllers planned to begin re-activating coolant loop A, clearing the way to restart scientific experiments and other hardware that was shut down when the coolant loop suffered a malfunction Dec. 11.

The successful spacewalk also clears the way for Expedition 38 commander Oleg Kotov and Russian flight engineer Sergey Ryazanskiy to carry out a spacewalk of their own on Friday. They plan to venture outside to mount cameras on the hull of the Zvezda command module as part of a commercial venture to beam down high-definition Earth views to subscribers around the world.

Today's spacewalk was the 258th by U.S. astronauts, the 176th devoted to station assembly and maintenance since construction began in 1998, the 10th so far this year, the eighth for Mastracchio and the second for Hopkins.

One hundred and 14 astronauts and cosmonauts have now spent 1,107 hours and 37 minutes of spacewalk time building and maintaining the International Space Station since construction began in 1998. Mastracchio's total through eight spacewalks now stands at 51 hours and 28 minutes, moving him up to sixth on the list of most experienced spacewalkers. Hopkins total EVA time through two spacewalks stands at 12 hours and 58 minutes.

The goal of today's outing was to install a replacement ammonia pump module in coolant loop A, one of two cooling systems used to dissipate the heat generated by the station's electrical systems. A valve in the loop A pump assembly malfunctioned Dec. 11, partially disabling the system and forcing flight controllers to power down non-essential systems.

More important, the malfunction left the station one failure away from a much more drastic powerdown should the lone operational coolant loop break down.

During a five-hour 28-minute spacewalk Saturday, Mastracchio and Hopkins disconnected the suspect ammonia pump module on the right side of the station's main power truss, pulled it from its slide-in rack in the S1 segment of the truss and mounted it on a nearby storage fixture to complete phase one of the coolant system repair job.

Because of an accidental switch throw inside the airlock at the end of the spacewalk, a small amount of water got into the plumbing of Mastracchio's backpack, raising the possibility that potentially damaging ice could form during the second EVA.

As a result, Mastracchio assembled a different suit for the second spacewalk while Hopkins used the one he wore Saturday, the same suit that developed a potentially dangerous leak during a July spacewalk.

After exhaustive troubleshooting, engineers concluded the leak was caused by contamination that clogged a filter. While the root cause of the contamination has not yet been determined, the astronauts replaced suspect components and both suits performed normally during both coolant repair spacewalks.

During their second spacewalk Tuesday, Mastracchio and Hopkins focused on installing the replacement pump module.

In spectacular video downlinked from the station, Mastracchio and Hopkins, anchored to the end of the station's robot arm, could be seen unbolting the spare pump module from its storage pallet and pulling it from its insulated enclosure.

"Looks like you're almost there," Mastracchio radioed as arm-operator Koichi Wakata, working inside the Destiny lab module, slowly pulled Hopkins and the pump assembly away. "You're out of the groove there, Mike, I think you're in charge now of the pump module. ... It's stable, Mike, it looks good, you're doing a great job, it looks beautiful."

Hopkins held the tethered pump module in his gloved hands as Wakata slowly moved him inboard from the storage pallet on the S3 truss segment to the pump's install location in the S1 segment.

The astronauts then guided the big module into place and drove home bolts to lock it down. They had no trouble hooking up the first two ammonia lines, known as M1 and M2. Another two lines, M3 and M4, were attached to a jumper box Saturday to allow the ammonia in the coolant loop to expand and contract as needed when the station flew into and out of sunlight.

The astronauts initially were unable to disconnect the half-inch-wide M4 line from the jumper box. Mastracchio retrieved a tool designed to apply additional force to the quick-disconnect bale holding the mechanism together. The idea was to push the lever far enough over to allow the astronauts to depress a locking button, allowing them to separate the two sides of the fitting.

But the stubborn fitting refused to cooperate.

"One thing we never expected," Mastracchio muttered at one point.

After positioning the quick-disconnect tool with varying degrees of force, flight controllers decided to lower the pressure in the line. Right around that point, the astronauts successfully demated the stubborn fitting, but reported "we do have snow coming out."

A few moments later, astronaut Douglas Wheelock in mission control asked the spacewalkers if ammonia was still leaking out "or has it dissipated."

"Yes. It's about one every second, one little snowflake a second," Mastracchio replied.

Asked if their spacesuits had been hit by any ice, Mastracchio said "absolutely," adding a few moments later "they are just completely drowning us now."

"Copy, Rick," Wheelock said. "And we have no video, Rick, so we'll just take your continued description."

"OK. They're pretty good size particles, much bigger than anything we've ever seen. See that big one going by you, Mike?"

"I do," Hopkins said.

"It looks like they're coming inboard of the pump module, all around the pump module, looks like," Mastracchio said. "I can't see it everywhere, where the light is, but they're hitting the wrist cluster of the SSRMS (robot arm), they're enveloping Mike, probably enveloping me, also."

"Yes they are," Hopkins said. "Big chunks, big chunks."

The ammonia presumably was trapped in the line and expelled when flight controllers sent commands to vent the jumper box. The leak rate diminished a few moments later and the astronauts pressed ahead with work to attach M4 and then M3 to the replacement pump module.

The ammonia posed no threat to the spacewalkers, but they had to spend a few extra minutes in vacuum to give any ice crystals that may of stuck to their suits time to dissipate. Decontamination procedures have been required during past spacewalks involving the ammonia coolant system to make sure returning spacewalkers don't introduce any toxic material into the station's air supply.

NASA originally held open the possibility of a third spacewalk to complete the coolant system repair work, but with the successful pump installation and activation Tuesday, the station crew now can look forward to a quiet Christmas in orbit before making preparations for the Russian spacewalk Friday.

12:15 PM EST, 12/24/13: Coolant lines attached to new pump; ammonia sprays suits as balky connector freed

Working to reconnect ammonia coolant lines to a replacement pump module, astronauts Rick Mastracchio and Mike Hopkins ran into problems freeing a quick-disconnect fitting and reported being "enveloped" in a cloud of ammonia ice crystals that spewed out arond the time flight controllers lowered pressure in the lines to make them easier to separate.

The astronauts had no problems installing the spare pump unit, bolting it in place and connecting the first two of the four ammonia coolant lines. The final two lines, known as M3 and M4, were connected to a bypass assembly Saturday to allow the ammonia in coolant loop A to expand and contract while the pump replacement was in progress.

Today, the astronauts had trouble disconnecting the half-inch-wide M4 line from the jumper box. Mastracchio retrieved a tool designed to apply additional force to the quick-disconnect bale holding the mechanism together. The idea was to push the lever far enough over to allow the astronauts to depress a locking button, allowing them to separate the two sides of the fitting.
This view from astronaut Mike Hopkins' helmet camera shows two ammonia lines, M1 and M2, connected to a replacement coolant pump to the left side of the frame. But the astronauts had problem disconnecting two other ammonia lines, visible to the right, that were hooked up to a so-called jumper box during a spacewalk Saturday. The astronauts finally got both lines disconnected, but a brief spray of ammonia ice crystals will require decontamination before Mastracchio and Hopkins can re-enter the space station. (Credit: NASA TV)

But the stubborn fitting refused to cooperate.

"One thing we never expected," Mastracchio observed at one point.

After positioning the quick-disconnect tool with varying degrees of force, flight controllers decided to lower the pressure in the line. Right around that point, the astronauts successfully demated the stubborn fitting, but reported "we do have snow coming out."

A few moments later, astronaut Douglas Wheelock in mission control asked the spacewalkers if ammonia was still leaking out "or has it dissipated."

"Yes. It's about one every second, one little snowflake a second," Mastracchio replied.

"Copy that, we're taking a look to see if maybe that could be residual in that spring cavity," Wheelock said. "Stand by."

"OK."

"And for both of you, could you tell us if any of the flakes contacted your suits?" Wheelock asked.

"Absolutely," said Mastracchio.

"Yeah," Hopkins agreed.

A few moments later, he said: "They are just completely drowning us now."

"Copy, Rick," Wheelock said. "And we have no video, Rick, so we'll just take your continued description."

"OK. They're pretty good size particles, much bigger than anything we've ever seen. See that big one going by you, Mike?"

"I do," Hopkins said.

"It looks like they're coming inboard of the pump module, all around the pump module, looks like," Mastracchio said. "I can't see it everywhere, where the light is, but they're hitting the wrist cluster of the SSRMS (robot arm), they're enveloping Mike, probably enveloping me, also."

"Yes they are," Hopkins said. "Big chunks, big chunks."

"Copy," Wheelock said.

"Quarter-inch diameter," Hopkins said.

The ammonia presumably was trapped in the line and expelled when flight controllers sent commands to vent the jumper box. The leak rate diminished a few moments later and the astronauts pressed ahead with work to attach M4 and then M3 to the replacement pump module.

The ammonia posed no threat to the spacewalkers, but they likely will have to spend additional time outside to give any ammonia crystals on their suits time to dissipate before re-entering the space station. Decontamination procedures have been required during past spacewalks involving the ammonia coolant system to make sure returning spacewalkers don't introduce any toxic material into the station's air supply.

But the immediate priority was to finish reconnecting the replacement pump module, the final step in repairing coolant loop A. The balky M4 line was connected to the pump module with no problem and the larger 1.5-inch-wide M3 line was attached and plugged in a few minutes later.

Flight controllers plan to carry out a quick test later today to make sure the replacement pump module is working properly.

It's not yet clear how much time Mastracchio and Hopkins might have to spend carrying out decontamination procedures, but the astronauts have more than enough air, water and power to make sure any ammonia still on their suits has time to dissipate.

10:55 AM EST, 12/24/13: Replacement pump module installed; astronauts work on connections

Astronauts Mike Hopkins and Rick Mastracchio disconnected a spare ammonia pump module from a storage pallet aboard the International Space Station Tuesday, pulled it from a protective enclosure, maneuvered it into place for installation in the lab's cooling system and drove home four bolts to lock it down.

Running about a half-hour behind schedule, the last bolt was tightened down three hours and 15 minutes after the spacewalk began. Hopkins and Mastracchio then began work to re-connect four ammonia coolant lines before turning their attention to five electrical cables to tie the pump module into coolant loop A.

The astronauts have not encounteed any major problems and both report their spacesuits are working normally, with no buildups of water or any other issues.

In spectacular video downlinked throughout the morning, Mastracchio and Hopkins, anchored to the end of the station's robot arm, could be seen unbolting the spare pump module from its storage pallet and pulling it from its insulated enclosure.

"Looks like you're almost there," Mastracchio radioed as arm-operator Koichi Wakata, working inside the Destiny lab module, slowly pulled Hopkins and the pump assembly away. "You're out of the groove there, Mike, I think you're in charge now of the pump module. ... It's stable, Mike, it looks good, you're doing a great job, it looks beautiful."

Hopkins held the tethered pump module in his gloved hands as Wakata slowly moved him inboard from the storage pallet to the pump's install location in the S1 truss segment. While the move was in progress, Mastracchio, closing up the spare pump's storage enclosure, reported a small micrometeoroid-orbital debris -- MMOD -- impact on the storage platform.

"Hey Houston, I did see a pretty good MMOD strike," he called down. "I took some pictures of it. It was well clear of us and well clear of any handrails. I'll show you the pictures when I get back in."

"Could you give us a general location where you saw that MMOD strike?" astronaut Douglas Wheelock asked from mission control.

"It was right on ESP-3 (external storage platform No. 3), right on the SPACEHAB emblem, kind of under the pump module, facing... I don't know which way it was facing," Mastracchio said.

Space debris and micrometeroid strikes are not uncommon and flight controllers keep track of their locations, when found, to make sure spacewalkers know where they might encounter sharp edges that could potentially damage their suits.
This view from astronaut Mike Hopkins' helmet camera shows a replacement ammonia pump module in the foreground, held by the astronaut's gloved hands, and an empty storage bay in the background as the unit was pulled away. (Credit: NASA TV)

Hopkins pulls the pump module away from external storage platform No. 3. (Credit: NASA TV)

In a breathtaking view, Hopkins and the pump module are seen midway through the move to the pump's install location. (Credit: NASA TV)

Hopkins and Mastracchio line up the refrigerator-size pump module before sliding it into place in the S1 truss segment. A faulty pump unit removed during a spacewalk Saturday is visible to the right. (Credit: NASA TV)

Hopkins and Mastracchio slide the new pump into place. (Credit: NASA TV)

08:20 AM EST, 12/24/13: A beautiful day in space

An hour-and-a-half into a planned six-hour spacewalk, astronauts Rick Mastracchio and Mike Hopkins have completed initial preparations and are now in the process of disconnecting a spare ammonia pump module from a storage pallet on the right side of the International Space Station's solar power truss.

Mastracchio is working to unplug three electrical cables while Hopkins, anchored to the end of the station's robot arm, is standing by to help out with bolts holding the 780-pound pump assembly in place.
Astronaut Rick Mastracchio makes his way outboard along the International Space Station's solar power truss, heading for a storage platform where a replacement ammonia pump module is mounted. The limb of the Earth is visible at left as the station approaches an orbital sunrise. (Credit: NASA TV)

Astronaut Rick Mastracchio. red stripes in foreground, and Mike Hopkins get set up near External Storage Platform No. 3 and a spare ammonia pump module that will be installed to restore one of the International Space Station's two coolant loops to normal operation.(Credit: NASA TV)

Once the unit is free, Japanese astronaut Koichi Wakata, operating the robot arm from a work station inside the Destiny laboratory module, will pull Hopkins and the pump module away from the storage platform and maneuver them both inboard to the S1 truss segment where the replacement pump will be installed.

Spectacular video from orbit earlier today showed the two astronauts as they got in position and prepared their equipment during a daylight pass over South America and central Europe.

"Beautiful view," Hopkins marveled at one point.

"Yeah, you're right over the heart of South America," astronaut Douglas Wheelock replied from mission control in Houston.

A few minutes later, the station was over Europe.

"How do you like riding the arm, Mike?" Mastracchio asked.

"It's good," Hopkins laughed. "Beautiful view."

"Yeah, you're kind of hanging on by your feet, aren't you?"

So far, the spacewalk is proceeding smoothly with no technical problems of any significance and the astronauts' spacesuits are performing normally.

06:55 AM EST, 12/24/13: Spacewalk begins

Astronauts Rick Mastracchio and Mike Hopkins, floating in the International Space Station's Quest airlock module, switched their spacesuits to battery power at 6:53 a.m. EST (GMT-5) Tuesday, officially kicking off a planned six-hour Christmas Eve spacewalk to complete repairs to the station's cooling system.

For identification, Hopkins, call sign EV-1, is wearing an unmarked suit with helmet camera No. 18. Mastracchio, EV-2, is wearing a suit with red stripes around the legs and using helmet camera No. 20. Switching roles for their second spacewalk, Hopkins will spend most of the day anchored to the end of the station's robot arm while Mastracchio will assist as a tethered free floater.

"Let's go to work," Hopkins said just before floating out of the airlock as the space station sailed 260 miles above eastern China.
Japanese astronaut Koichi Wakata prepares to operate the International Space Station's robot arm from a computer work station in the Destiny laboratory module. Spacewalker Mike Hopkins will be anchored to the arm during a spacewalk Tuesday to finish repairs to the station's cooling system. (Credit: NASA TV)

Assuming the repair work goes well and a third spacewalk is not required, two Russian cosmonauts will venture outside Friday for an already planned excursion to install cameras on the Zvezda command module that will be used by a Canadian company to beam down high-definition Earth views to subscribers around the world.

Today's spacewalk is the 258th by U.S. astronauts, the 176th devoted to station assembly and maintenance since construction began in 1998, the 10th so far this year, the eighth for Mastracchio and the second for Hopkins.

The goal of the excursion is to install a replacement ammonia pump module in coolant loop A, one of two cooling systems used to dissipate the heat generated by the station's electrical systems. A valve in the loop A pump assembly malfunctioned Dec. 11, partially disabling the system and forcing flight controllers to power down non-essential systems.

More important, the malfunction left the station one failure away from a more drastic powerdown -- and possible evacuation -- should the lone operational coolant loop break down.

During a five-hour 28-minute spacewalk Saturday, Mastracchio and Hopkins disconnected the suspect ammonia pump module on the right side of the station's main power truss, pulled it from its slide-in rack in the S1 segment of the truss and mounted it on a nearby storage fixture to complete phase one of the coolant system repair job.

Because of an accidental switch throw inside the airlock at the end of the spacewalk, a small amount of water got into the plumbing of Mastracchio's backpack, raising the possibility that potentially damaging ice could form during the second EVA.

As a result, Mastracchio is wearing a different upper torso and backpack, No. 3005, for the second spacewalk while Hopkins is using the one he wore Saturday, No. 3011. That's the same suit that developed a potentially dangerous leak during a July spacewalk.

After exhaustive troubleshooting, engineers concluded the leak was caused by contamination that clogged a filter. While the root cause of the contamination has not yet been determined, the astronauts replaced suspect components and both suits performed normally during Saturday's spacewalk.

During their second spacewalk Tuesday, Mastracchio and Hopkins plan to take a spare pump module from a storage pallet attached to the S3 truss segment, install it in place of the faulty unit and reconnect four ammonia lines and five power cables.

Assuming the spare unit works as expected, flight controllers will power up the systems that were shut down earlier, restoring the space station to normal operations.

The work marks the second time in three years station astronauts have had to replace the coolant loop A pump module.

In August 2010, two other astronauts needed three spacewalks to install the unit that was removed Saturday after the pump in the original module suffered a failure and stopped working, taking down the entire coolant loop and forcing the crew to implement widespread powerdowns.

This time around, the pump in question was in good health, but a flow control valve in the system's plumbing malfunctioned, resulting in lower-than-allowable ammonia temperatures. Engineers attempted to restore coolant loop A to near-normal operation using a software "patch," but NASA managers ultimately decided to replace the pump module.

During the 2010 spacewalks, the astronauts ran into problems with ammonia line quick-disconnect fittings, but applying lessons learned, Mastracchio and Hopkins had no trouble Saturday, getting far enough ahead of schedule to go ahead and remove the pump module, work originally planned for the second spacewalk.

Assuming the replacement pump gets installed and works properly, NASA will forego a third spacewalk, leaving the faulty pump unit where it was mounted Saturday for the next several months.

At some point, a future team of spacewalkers will need to move it to a more secure storage location, but there's no hurry. A thermal analysis shows the pump module can remain where it is until next summer.

In the meantime, two Russian cosmonauts, Expedition 38 commander Oleg Kotov and Sergey Ryazanskiy, are gearing up for a spacewalk of their own on Friday to install high-definition and medium-resolution cameras for a Canadian company, UrtheCast, and to replace external materials science experiments.

They are expected to open the hatch of the Pirs airlock module around 7 a.m. Friday to begin the year's 11th and final planned space station spacewalk.

© 2013 William Harwood/CBS News

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Astronauts complete rare Christmas Eve spacewalk
By MARCIA DUNN
.
Raw: New Cooling Unit Installed, Awaiting Testin
CAPE CANAVERAL, Fla. (AP) — Space station astronauts repaired a crippled cooling system during a rare Christmas Eve spacewalk Tuesday, braving a "mini blizzard" of noxious ammonia as they popped in a new pump.
It was the second spacewalk in four days for U.S. astronauts Rick Mastracchio and Michael Hopkins, and only the second Christmas Eve spacewalk ever.
NASA ordered up the spacewalks to revive a critical cooling loop at the International Space Station. All nonessential equipment had to be turned off when the line conked out Dec. 11, and many science experiments halted.
With Tuesday's success, the cooling system should be restored and all equipment up and running by this weekend, according to NASA.
"It's the best Christmas ever," Mission Control radioed as the 7½-hour spacewalk came to a close.
"Merry Christmas to everybody," replied Hopkins. "It took a couple weeks to get her done, but we got it."
View gallery

In this Saturday, Dec. 21, 2013 photo provided by NASA and tweeted Sunday, Dec. 22, by NASA astronau …
Mastracchio and Hopkins removed the faulty ammonia pump during Saturday's spacewalk. On Tuesday, they installed the fresh pump.
Standing on the end of the station's main robotic arm, Hopkins clutched the 780-pound, refrigerator-size pump with both hands as he headed toward its installation spot, and then slid it in. An astronaut working inside, Japan's Koichi Wakata, gingerly steered the arm and its precious load.
"Mike Hopkins taking a special sleigh ride on this Christmas Eve," Mission Control commentator Rob Navias said as the space station soared over the Pacific.
It was slow going because of a balky ammonia fluid line that sent frozen flakes of the extremely toxic substance straight at the men — "a mini blizzard," as Mission Control called it. The spacewalkers reported being surrounded by big chunks of the stuff that bounced off equipment and, in all probability, their suits.
The ammonia needed to dissipate from their suits before the pair returned inside, to avoid further contamination.
View gallery

In this image taken from video provided by NASA, astronauts Rick Mastracchio, top, and Michael Hopki …
"Wow," Hopkins sighed after the fourth and final fluid line was hooked to the new pump. The electrical hookups went more smoothly, and six hours into the spacewalk, Hopkins finally called down, "Houston, you've got yourself a new pump module."
Christmas references filled the radio waves as the action unfolded 260 miles above the planet.
"It's like Christmas morning opening up a little present here," Mastracchio said as he checked his toolkit. Later, as he worked to remove the spare pump from its storage shelf, he commented: "Now it really feels like I'm unwrapping a present."
Mission Control in Houston was in a festive mood, despite the gravity of the situation. Tabletop Christmas trees, Santa dolls and red Santa caps decorated the desks.
NASA's only previous Christmas Eve spacewalk occurred in 1999 during a Hubble Space Telescope repair mission.
View gallery

CORRECTS DAY OF WEEK TO TUESDAY INSTEAD OF MONDAY - In this image taken from video provided by NASA, …
But NASA's most memorable Christmas Eve was back on Dec. 24, 1968. Apollo 8 astronauts read from Genesis, the first book of the Bible, as they orbited the moon on mankind's first lunar flight.
A bad valve in the ammonia pump caused the latest breakdown.
Another team of spacewalking astronauts installed that pump just three years ago, and engineers are perplexed as to why it didn't last longer. NASA hopes to salvage it in the years ahead.
The 2010 replacement required three spacewalks because of the difficulty in removing pressurized ammonia fluid lines. But this time, the astronauts managed to squeeze everything into two after NASA reduced the pressure and simplified the task.
Mission Control successfully activated the pump Tuesday night. The two-line external cooling system uses ammonia to dispel heat generated by on-board equipment; only one loop was disabled by the breakdown.
The second spacewalk was supposed to take place Monday but was delayed a day to give Mastracchio time to switch to another suit. He inadvertently hit a water switch in the air lock at the end of Saturday's excursion, and a bit of water encroached on a cooling device in the backpack of his suit, making it unusable.
Otherwise, the suits remained dry during both spacewalks. Last July, an astronaut almost drowned when water from his suit's cooling system flooded his helmet. Makeshift snorkels and absorbent pads were added to the suits as a precaution.
A Moscow-led spacewalk, meanwhile, is set for Friday. Two Russian crew members will install new cameras and fresh experiments outside.

Copyright © 2013 The Associated Press. All rights reserved.

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Spacewalkers install new station cooling pump
By Irene Klotz

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NASA astronaut Mike Hopkins is seen during the spacewalk in this photo courtesy of NASA, received December …
By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - Two NASA astronauts spent more than seven hours working outside the International Space Station on Tuesday and successfully repaired a critical cooling system.
It was the second spacewalk in three days for flight engineers Rick Mastracchio and Mike Hopkins, who wrapped up the cumbersome work with only one problem.
As they were installing a spare cooling pump, a sprinkling of ammonia crystals leaked out from one of four fluid lines. The toxic liquid turns to flakes in the cold and weightlessness environment of space.
The astronauts spent an extra 15 minutes in the station's Quest airlock to bake out any potential residue on their spacesuits. The 7.5-hour spacewalk was broadcast live on NASA Television.
"It took a couple of licks to get her done, but we got it," Hopkins radioed to flight controllers at NASA's Mission Control Center in Houston.
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Flight engineers Michael Hopkins and Richard Mastracchio perform a series of spacewalks outside the …
The new pump will not be fully tested until later on Tuesday, but an initial check in the final hour of the spacewalk showed it was "alive and well," reported NASA mission commentator Rob Navias.
During a spacewalk on Saturday, the astronauts removed a failed cooling system pump and attached it to a temporary storage site at the base of the station's mobile rail cart.
NASA is considering a potential future spacewalk to repair the refrigerator-size pump and use it as a spare, officials said.
In addition to the new pump installed on Tuesday, there are two other spare pumps aboard the station, a $100 billion research complex that flies about 260 miles above Earth.
The U.S. side of the station, which includes Japanese and European laboratories, has been without half its cooling system since December 11 when a valve failed inside a pump.
The six-member crew was never in any danger, NASA said, but both cooling systems are needed to radiate heat from the station's modules and laboratories.
With just one cooling loop, astronauts had to turn off unnecessary equipment and some science experiments. The Russian part of the station has a separate cooling system.
The spacewalks were NASA's first since July when the water-cooled spacesuit worn by Italian astronaut Luca Parmitano developed a leak. His helmet began filling with water, a situation that could have caused him to drown if the spacewalk was not quickly aborted.
Engineers at the time traced the problem to contaminated water in a device that circulates water and air in a spacesuit and takes moisture out of the air. How the water became contaminated remains under investigation.
As a precaution, the helmets worn by Mastracchio and Hopkins were outfitted with moisture-absorbent pads and snorkels that could draw air from the belly of the spacesuits in case the problem recurred. No leaks were reported, Navias said.
NASA decided to forego a third spacewalk to relocate the failed pump onto a more permanent storage pallet, officials said.
Two Russian cosmonauts, meanwhile, are planning to conduct a spacewalk on Friday to install a pair of high-fidelity cameras outside the Zvezda service module, part of a Canadian commercial television project. They also will swap out several science experiments.
(Editing by Kevin Gray, Maureen Bavdek and Gunna Dickson)

Copyright © 2013 Reuters Limited. All rights reserved.

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Astronauts wrap up successful spacewalk to fix station
By Kerry SHERIDAN

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Washington (AFP) - Two NASA astronauts wrapped up successful repairs at the International Space Station after a rare Christmas Eve spacewalk to fix an equipment cooling system.
Americans Rick Mastracchio, 53, and Mike Hopkins, 44, floated outside the orbiting lab for seven and a half hours to replace an ammonia pump whose internal control valve failed on December 11.
"We have a pump that is alive and well," said NASA commentator Rob Navias on the US space agency's live television feed after a successful jumpstart test on the newly installed pump module, a bulky piece of gear the size of a refrigerator.
NASA said later Tuesday, after further checks, the pump was "considered fully functional."
"It will take some time to fully reintegrate" the space station's cooling system, NASA said on its web site, adding it expected that process to be completed by the next day.
Meanwhile, electrical systems depending on the newly repaired system -- which had been turned off or switched to a backup -- would be restored to normal over the next several days, it added.
Despite recent concerns about leaking spacesuits, neither astronaut reported any problems during the spacewalk.
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A graphic on details of repairs to the International Space Station (AFP Photo/)
The suits "have functioned perfectly and have been bone dry throughout the course of today's spacewalk," Navias said.
Hopkins, making his second career spacewalk, rode a 57-foot (15-meter) robotic arm, operated from inside the station by Japanese astronaut Koichi Wakata.
With his boots affixed to the Canadian-made arm, Hopkins grasped the bulky pump module as Wakata maneuvered him over to its installation location.
Then Mastracchio, who was making his eighth career spacewalk, helped push the module into its slot and the pair began affixing it in place.
Five electrical connections and four fluid connections followed, and a brief test, like a jumpstart, was done to test the pump's connections and electronics.
The team made swift work of a first spacewalk on Saturday, disconnecting and pulling out the old cooling pump that regulates the temperature of equipment at the orbiting space lab.
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US astronaut Rick Mastracchio during a space suit test prior to blast off to the International Space …
They managed to complete what had been seen as almost two days' work in a single outing that lasted just five and a half hours.
Orchestrating the spacewalks from inside the station's Destiny laboratory was Wakata of the Japan Aerospace Exploration Agency.
Wakata arrived at the space station in November for a half-year stay as part of the six-member international crew.
In March, he will become the first Japanese commander of the space station, NASA said.
Mastracchio was meanwhile wearing a different spacesuit than the one he donned on Saturday, a backup that was stored at the station and was resized to fit him over the weekend.
On Saturday, a "small amount of water" entered his suit's cooling system in the station airlock after he finished the spacewalk, NASA said.
But the US space agency said the problem was not related to the water leak in a helmet that cut short Italian astronaut Luca Parmitano's spacewalk in July and risked drowning him.
NASA is still investigating what went wrong in that case.
As a backup measure, the astronauts are now outfitted with emergency snorkels in their spacesuits and extra pads to absorb any leaking water in their helmets.
NASA officials have said the suits, which were designed 35 years ago, are safe, and stressed that Saturday's problem did not put Mastracchio in any danger.
NASA said the last time astronauts embarked on a Christmas Eve spacewalk was 14 years ago, when space shuttle Discovery astronauts Steve Smith and John Grunsfeld stepped out to install upgrades and new insulation on the Hubble Space Telescope.
On Wednesday, the six-man crew at the station will be off duty to enjoy a quiet Christmas, NASA said.
On Friday, Russian cosmonauts Oleg Kotov and Sergey Ryazansky will embark on a spacewalk to install a pair of high-fidelity cameras on the Zvezda service module and do maintenance on the Russian segment of the station.

Copyright © 2013 Agence France Presse. All rights reserved.

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Astronauts Brave Brief Ammonia Snowstorm As They Conclude Fix To Space Station
by Elizabeth Howell on December 24, 2013

NASA astronaut Mike Hopkins holds a spare ammonia pump module during a spacewalk Dec. 24, 2013. Hopkins and fellow Expedition 38 Rick Mastracchio (top) performed two spacewalks to replace a pump blamed for crippling one of the International Space Station's two cooling loops Dec. 11. Credit: NASA TV (screenshot)
Toxic snowflakes in space were just one obstacle astronauts faced down today (Dec. 24) as they successfully replaced an ammonia pump that will, if all goes to plan, put the space station back in full service in a few hours.
"They're just completely surrounding us now," radioed NASA astronaut Rick Mastracchio of the ammonia flakes as the astronauts clipped four fluid lines into place on to the spare pump. NASA said the ammonia was just residual fluid and not indicative of a leak. "Some little ones, some big ones," he added.
Within a few minutes, however, the ammonia dissipated. Some flakes did strike the spacesuits of Mastracchio and fellow NASA spacewalker Mike Hopkins, causing NASA to do a modified decontamination procedure where the astronauts stayed in a vacuum for a few extra minutes inside the airlock. (The sun's heat bakes off ammonia over time, and the crew was outside long enough for most ammonia to dissipate, NASA said.)
The spacewalk completed with no further drama at 7 hours and 30 minutes, earning high praise for the participating astronauts from Mission Control in Houston.
"It's the best Christmas ever," radioed CapCom and NASA astronaut Doug Wheelock from the ground as the spacewalkers entered the International Space Station's Quest airlock at the end of the repair job. "We got it," Mastracchio responded.
NASA astronaut Doug Wheelock (left) and Japanese astronaut Aki Hoshide served as CapComs during two tricky ammonia pump replacements in December 2013. Wheelock assisted Expedition 38 spacewalking astronauts Mike Hopkins and Rick Mastracchio, while Hoshide helped Japanese astronaut Koichi Wakata with robotic maneuvers. Credit: NASA TV (screenshot)
Preliminary tests show the spare pump is working perfectly. The pump is a welcome present for the six-person Expedition 38 crew, which saw a reduction in science and backup systems for two weeks after a valve in the last pump failed, causing one of the station's two cooling loops to shut down automatically. The loops are needed to regulate the temperatures of electronics and systems on station.
The Expedition 38 crew was so quick with the repair that they finished the job in two spacewalks instead of the planned three. The astronauts fell behind the timeline today as they struggled with some of the fluid connections to the new pump, but the final steps — putting the electrical connections in place — took just minutes. The pump was brought from another location on station today, and installed into its permanent spot to help ammonia flow through the cooling system.
Anywhere between hundreds and thousands of people at NASA and international partners scrambled to put spacewalks together to fix the cooling problem after it happened. Wheelock, himself a veteran of a tricky ammonia pump repair in 2010, communicated with the spacewalkers. Japanese astronaut Aki Hoshide filled the other CapCom slot, helping Japanese astronaut Koichi Wakata who handled robotics in orbit.
Japanese astronaut Koichi Wakata controlled Canadarm2 during two spacewalks to replace a faulty ammonia pump in December 2013. Credit: NASA TV (screenshot)
Mastracchio marked his eighth spacewalk with today's repair while Hopkins, who rode Canadarm2 for the first time in a last-minute decision, was on his second. As with a spacewalk on Saturday (Dec. 21), the astronauts reported no helmet water leaks — comforting words for agency officials who put in new procedures and parts after an incident in July. (Mastracchio experienced a water problem during repressurization Saturday that was unrelated to the first incident, and wore a backup suit today to let the primary one dry out.)
Should the ammonia pump work as planned, this clears the way for the Russians to do a spacewalk Dec. 27 to install the Urthecast high-resolution camera that will beam live views of Earth, among other tasks. Expedition 38 has the day off tomorrow (Dec. 25), NASA TV added.
The only other Christmas Eve spacewalk in NASA history took place Dec. 24, 1999 during Hubble Space Telescope servicing mission STS-103. Another Christmas Eve milestone for NASA took place 45 years ago today, when the Apollo 8 crew made a now-famous broadcast while orbiting above the moon.
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Astronauts successfully replace faulty pump on ISS
A NASA TV image shows astronauts Mike Hopkins, left, and Rick Mastracchio position a spare ammonia pump during a spacewalk outside the International Space Station. (AFP/Getty Images / December 24, 2013)
By Monte Morin
December 24, 2013, 11:20 a.m.
NASA astronauts Tuesday successfully replaced a faulty fluid pump in the International Space Station, following two days of work in the open vacuum of space 260 miles above the Earth's surface.
The 7 1/2-hour spacewalk was only the second in NASA history to occur on Christmas Eve. The first was in 1999, when astronauts made repairs to the Hubble Space Telescope.
Like any DIY home-improvement project, the work involved a glitch or two. The first occurred when a fluid line refused to budge and Astronauts Rick Mastracchio and Michael Hopkins struggled to remove it.
When they finally did get it off, tiny flakes of frozen ammonia drifted from the connection, raising concerns that the flakes had landed on the astronauts' spacesuits and might be brought back into the ISS, where they would instantly turn to a corrosive gas.
Though the crewmen initially planned to undergo a decontamination procedure known as a "bake-off," that requirement was waived in the final minutes of the mission. Lengthy exposure to the sun during the work probably eliminated the threat, Mission Control in Houston determined.
"Head to the barn," Mission Control told the astronauts as they entered the space station's airlock just before 11 a.m. PST, after completing the work.
2013: The Year in Science
Mastracchio and Hopkins had been tasked with replacing a pump in one of the station's two external ammonia cooling loops. The system is responsible for keeping instruments inside and outside the station from overheating.
On Saturday, the astronauts worked 5 1/2 hours to disconnect the faulty pump from four ammonia fluid lines and move it to a storage site.
Early Tuesday morning, the astronauts maneuvered a new, refrigerator-sized pump into place with the help of a massive robotic arm controlled by Japanese astronaut Koichi Wakata inside the station.
"Mike Hopkins taking a special sleigh ride on this Christmas Eve," Mission Control commentator Rob Navias said as Hopkins stood on the end of the robotic arm gripping the new pump.
The 3-year-old ammonia pump stopped working on Dec. 11 due to a faulty valve, requiring astronauts to halt numerous science experiments until the problem was resolved. The replacement pump is one of three spares on the ISS.
The second day of repair work was initially planned for Monday, but the spacewalk was postponed a day due to a potential problem with Mastracchio's spacesuit. Crew members reported that water entered the suit when the astronaut accidentally hit a switch in the space station airlock.
The postponement allowed crew members to assemble a second replacement suit for Mastracchio.
The recent spacewalks were absent the problems that plagued Italian astronaut Luca Parmitano of the European Space Agency in July. During that walk, Parmitano's helmet began to fill with water when the suit's cooling system backed up and began to leak. The astronaut nearly drowned as blobs of weightless water clung to his head.
NASA officials said the problems with the two spacesuits were unrelated, and that the suits had been modified to prevent such episodes in the future. Those modifications included the installation of absorbent pads and breathing snorkels.
Copyright © 2013, Los Angeles Times
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In Spacewalk, Astronauts Complete Repairs to Station
NASA/Reuters
Col. Michael S. Hopkins installed a new pump module on the International Space Station on Tuesday.
By KENNETH CHANG
Published: December 24, 2013
NASA astronauts on Tuesday completed urgent repairs to the cooling system of the International Space Station that should return it to normal operation within a few days.
In a seven-and-a-half-hour spacewalk, their second in four days, the astronauts, Col. Michael S. Hopkins of the Air Force and Richard A. Mastracchio, installed a new pump module on the outside of the space station.
The module, a 780-pound box about the size of a refrigerator, contains a pump and accompanying apparatus that circulate ammonia coolant through one of two loops on the station.
"It's like Christmas morning opening up a little present here," said Mr. Mastracchio, an engineer, as the spacewalk unfolded on NASA Television.
Operations on the space station, including some science experiments, have been curtailed since a valve in the pump module malfunctioned two weeks ago.
Plugging in the last of the electrical connectors on Tuesday afternoon, Colonel Hopkins said, "Houston, you've got yourself a new pump module."
The pump passed a brief check, and was turned on Tuesday evening. "We have a pump that is alive and well," said Rob Navias, a NASA spokesman who provided commentary during the spacewalk. Nonessential equipment that had been turned off should be switched on by the end of the week or early next week, he said.
The first spacewalk, on Saturday, went quickly and almost flawlessly, and the astronauts were able to get far ahead of schedule and remove the old module, a task that had originally been scheduled for the second spacewalk.
On Tuesday, they ran into trouble when one of the ammonia fluid lines would not detach. With brainstorming help from mission control, they finally succeeded, but then some toxic flakes of frozen ammonia leaked out. The astronauts had to take a few precautions at the end of the spacewalk to ensure their spacesuits were decontaminated.
During a spacewalk in July, the cooling system in an Italian astronaut's spacesuit malfunctioned and the helmet partly filled with water. There were no such problems this time.
"Fantastic work," Colonel Hopkins said as he re-entered the airlock. "Merry Christmas to everybody."
The malfunctioning pump module had been installed just three years ago, and the station has only two more spares available. With the space shuttle fleet retired, NASA has no craft big enough to ferry a replacement up from Earth.
The module will be stored on the outside of the space station, and NASA officials said it might be possible to return it to service in the future, even with the faulty valve.
After a busy few days, the station's six crew members will have a day off on Christmas.
On Friday, two Russian astronauts are to conduct a previously scheduled seven-hour spacewalk to install two cameras and replenish some science experiments outside the station.
<img src="http://meter-svc.nytimes.com/meter.gif">
A version of this article appears in print on December 25, 2013, on page A19 of the New York edition with the headline: In Spacewalk, Astronauts Complete Repairs to Station.
© 2013 The New York Times Company

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Spacewalking Astronauts Gift Space Station with Christmas Eve Cooling Pump Fix
by Robert Z. Pearlman, SPACE.com Contributor | December 24, 2013 01:20pm ET
NASA astronaut Mike Hopkins flies above Peru while attached to the station's robotic arm during a spacewalk.
Credit: NASA TV View full size image
HOUSTON — Astronauts aboard the International Space Station have received a gift just in time for Christmas: a new pump module to repair their ailing cooling system and to restore the outpost to full power.
NASA astronauts Rick Mastracchio and Mike Hopkins embarked on their second spacewalk together, setting out at 6:53 a.m. EST (1153 GMT) on Tuesday (Dec. 24) to complete the work they began Saturday to remove and replace an ammonia pump module with a faulty flow control valve.
NASA's Mike Hopkins holds the space station's new pump module while floating past a Russian Soyuz spacecraft.
Credit: NASA TV
View full size image
"Houston from the airlock, we'd just like to say thanks to all the great folks doing all this hard work to get this space station back up and running," Mastracchio radioed at the end of the spacewalk, which concluded at 2:23 p.m. EST (1923 GMT), seven hours and 30 minutes after it began. [See photos from the Christmas Eve spacewalk]
"No, thank you guys," astronaut capcom Doug Wheelock replied from NASA's Mission Control in Houston. "It is the best Christmas ever. Thanks, guys."
"I'd just like to add to that," Hopkins said. "Fantastic work, merry Christmas to everybody. It took a couple of licks to get her done, but we got it."
The Christmas Eve EVA — extravehicular activity, NASA's term for a spacewalk — had the two astronauts retrieve a spare of the refrigerator-size cooling system device and install it on the space station's starboard, or right, side backbone truss. The 780-pound (355 kg) pump module replaced a faulty unit Mastracchio and Hopkins successfully and speedily removed three days ago.
The removal, which came just 10 days after a valve inside the module ceased working properly, was originally slated to be part of this second outing, but Mastracchio and Hopkins made quick work of disconnecting the degraded unit, allowing them the time to also remove and stow the module during the spacewalk Saturday.
Their get-ahead work negated the need for a planned third spacewalk.
Pump module in place
The failure of the flow control valve, which regulates the temperature of the ammonia coolant passing through the pump, resulted in restricting the space station to the use of just half of its cooling loop system needed to maintain equipment temperatures inside and outside of the outpost. Non-critical systems and science experiment hardware in two of the station's laboratories have been without power since the valve malfunctioned on Dec. 11.
NASA astronaut Mike Hopkins prepares to attach himself to the International Space Station's robotic arm during a Christmas Eve spacewalk on Dec. 24, 2013.
Credit: NASA TV
View full size image
The new pump module, installed by Mastracchio and Hopkins on Tuesday, was to return the space station to its full cooling and power capacity.
Trading spaces since their spacewalk together on Saturday, Hopkins, riding the end of the station's robotic arm, and Mastracchio working alongside him, retrieved the spare pump module from the station's External Stowage Platform 3 (ESP-3) and installed it in the slot on the truss they earlier emptied of the faulty unit.
"Mike, I think you're in charge now of the pump module," Japanese astronaut Koichi Wakata radioed Hopkins as he controlled the robotic arm to pull Hopkins and the spare pump module away from the stowage platform. "It looks good, you're doing a great job, it looks beautiful."
The pump module was bolted into place at 10:08 a.m. EST (1508 GMT), 3 hours and 15 minutes into the spacewalk. [How the Space Station's Cooling System Works (Infographic)]
'Snow' on Christmas Eve
The two astronauts then set about connecting five electrical and four fluid lines linking the new module to the station's systems. In the process, the pair ran into some trouble freeing one of the so-called "quick disconnect" lines from a temporary jumper box that the two installed during Saturday's spacewalk.
"One thing we never expected," Mastracchio observed.
"Getting it off the jumper box?" Hopkins replied.
"Yeah," Mastracchio said.
They were ultimately able to free the stubborn line using some additional tools. In the process, they released some frozen ammonia flakes, or "snow."
"About one little snowflake a second," Mastracchio reported to Mission Control, adding that the flakes did make contact with both astronauts' spacesuits, a contamination concern.
"Big chunks, big chunks," Mastracchio noted as Mission Control sent a command to vent the line. "Some little ones, some big ones."
As the line was vented, the astronauts confirmed it had "stopped snowing" and they proceeded with connecting it and the remaining lines to the new pump module. All nine lines were connected at about 12:45 p.m. EST (1645 GMT), 5 hours and 52 minutes into the spacewalk.
"Houston you have a new pump module," Mastracchio radioed Mission Control.
Second eve EVA
With the new pump module in place and its lines connected, flight controllers on the ground will work on Tuesday evening to test the unit and then, if everything checks out, begin reintegrating it into the space station's cooling system over the next day.
Tuesday's spacewalk marked Mastracchio's eighth career EVA and Hopkins' second. It was the 176th spacewalk devoted to the assembly and maintenance of the International Space Station and the 10th such outing in 2013.
One more spacewalk this year is scheduled for Friday (Dec. 27) by cosmonauts Oleg Kotov and Sergey Ryazanskiy to install a pair of high-fidelity cameras and refresh several experiment packages on the exterior of the Russian segment of the station.
Tuesday's EVA was only the second Christmas Eve spacewalk conducted in history. Fourteen years ago, space shuttle Discovery astronauts Steve Smith and John Grunsfeld conducted an 8-hour, 8-minute excursion on Dec. 24, 1999 to upgrade and install new insulation on the Hubble Space Telescope.
Editor's Note: This story was updated to reflect a change at 1:53 p.m. EST. The astronauts did not need to perform a "bake out" after cleaning up during the spacewalk. The story was also updated to add more details about the spacewalk.

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