Keep the shuttle flying: Fwd: U.S. EVA-25

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: December 24, 2013 11:20:52 AM CST
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: U.S. EVA-25

Astronauts prep for second coolant repair spacewalk
12/23/2013 02:03 PM
By WILLIAM HARWOOD
CBS News

Astronauts Rick Mastracchio and Mike Hopkins prepared their spacesuits Monday for a Christmas Eve spacewalk, their second in four days to complete an urgent cooling system repair job, installing a spare 780-pound ammonia pump module on the right side of the International Space Station's main power truss.

If the spacewalk goes as smoothly as the initial repair work did during a five-hour 28-minute excursion Saturday -- and assuming the replacement pump module works as expected to restore lost cooling -- a third spacewalk will not be required.

That would clear the decks for an already-planned Russian spacewalk Friday to install high-definition cameras on the hull of the Zvezda command module as part of a commercial venture with a Canadian company that plans to beam down Earth views to subscribers around the world.

But first, Mastracchio and Hopkins, switching roles for their second spacewalk, must finish the coolant system repair work.
Astronaut Mike Hopkins works in the Quest airlock module Monday, preparing the suits he and Rick Mastracchio will wear during a Christmas Eve spacewalk to complete repairs of the space station's cooling system. The spacewalk is scheduled to begin around 7:10 a.m. EST Tuesday. (Credit: NASA TV)

For identification, Hopkins, call sign EV-1, will be wearing an unmarked suit with helmet camera No. 18. Mastracchio, EV-2, will be wearing a suit with red stripes around the legs and using helmet camera No. 20. This will be the 176th spacewalk 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.

If all goes well, the astronauts, floating in the Quest airlock module, will switch their suits to internal battery power around 7:10 a.m. EST (GMT-5) Tuesday to officially kick off a planned six-hour spacewalk.

Because of an accidental switch throw inside the airlock at the end of the first repair spacewalk Saturday, 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 will be using a different upper torso and backpack, No. 3005, while Hopkins will continue 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.

The cooling system repair work was ordered in the wake of a valve malfunction that partially disabled one of the space station's two ammonia coolant loops, which dissipate the heat generated by the lab's electronic systems.

With one loop only partially functional, flight controllers had to power down non-essential equipment in the U.S. segment of the station, including much of the crew's research equipment. More important, the failure left the station with just one fully operational coolant loop and a subsequent problem with that system could require extensive power downs and a possible evacuation.

Engineers initially hoped to restore coolant loop A to normal, or near-normal, operation with a software "patch," but mission managers eventually decided to simply replace the pump module with one of three spares currently on board the station.

During their first spacewalk Saturday, Hopkins and Mastracchio successfully removed the coolant loop A pump module, disconnecting four ammonia lines and five power cables. Mastracchio, anchored to the end of the station's robot arm, then pulled the bulky pump module out of its rack in the S1 truss segment.

After a grapple fixture was attached to the pump housing, Mastracchio carried it to a nearby attachment fixture where the box was locked down and plugged into station power for long-term storage.

The original flight plan called for up to three spacewalks to replace the pump module, with its actual removal planned for the second EVA. But Mastracchio and Hopkins had no problems with the sometimes troublesome ammonia connectors and they were able to complete the removal task on Saturday.

Running well ahead of schedule, flight controllers asked the crew about extending the spacewalk to accomplish more get-ahead work, but Mastracchio said he preferred to end the excursion at that point. He did not say why he was reluctant to continue and flight controllers did not press him for an explanation.

During the second spacewalk, the astronauts plan to remove a replacement pump module from its storage pallet on the S3 truss segment, install it in the S1 slot where the faulty pump had been and re-attach the four ammonia lines and five electrical cables. This time around, Hopkins will be anchored to the end of the station's robot arm while Mastracchio, safely tethered, free floats.

NASA originally planned the second spacewalk for Monday, but the inadvertent switch throw at the end of the first outing that allowed water to enter Mastracchio's backpack prompted flight controllers to change their plans. While the suit was not damaged, its internal systems must be thoroughly dried out and that can take a week or so to accomplish.

"At the end of (the Saturday spacewalk), we pressurized the airlock and once we did that, we had an inadvertent switch throw that turned some water on to go to one of the suits," Flight Director Judd Frieling said Monday. "That inadvertent switch throw made us question whether we got some water in the sublimator module of one of those suits while it was at pressure."

The sublimator in the spacesuit's backpack uses ice to provide cooling during a spacewalk, turning warmed water directly into vapor that is vented into space.

"We expect water to go in the sublimator when we're at vacuum in the airlock, and the act of that water going into the sublimator actually is what creates an ice brick on the sublimator and allows us to reject heat on the suits once they go out EVA," Frieling said.

"When water gets in that sublimator at pressure, there's a chance that once we go back to vacuum again that that water will freeze in an incorrect place in the sublimator and kind of let it expand out and (damage) the sublimator. Because there was a question about whether we had liquid water in the sublimator of that suit, 3010, which was Rick's suit, we had to call that suit no go."

Mastracchio's suit, No. 3010, was equipped with a portable life support system backpack built in 1984. The PLSS was overhauled and upgraded in March 2009 and launched to the station aboard a space shuttle.

Because of the question about water in the sublimator of suit 3010, Mastracchio will wear a spacesuit made up of components from other available suits, sized to fit his frame, for the second spacewalk, including backpack No. 3005. His original suit will be dried out and returned to service later.

"Unless something goes awry, we should wrap up all of this pump replacement work in just two spacewalks," said NASA mission control commentator Rob Navias.

If so, the crew will enjoy a holiday break Wednesday while two Russian cosmonauts, Expedition 38 commander Oleg Kotov and Sergey Ryazanskiy, prepare 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.

Realtime coverage of U.S. EVA-25
12/24/2013 08:46 AM
By WILLIAM HARWOOD
CBS News

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 make rare Christmas Eve spacewalk
By MARCIA DUNN

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CAPE CANAVERAL, Fla. (AP) — Two space station astronauts ventured out on a rare Christmas Eve spacewalk Tuesday, hoping to wrap up urgent repairs to a cooling system.
It was the second spacewalk in four days for U.S. astronauts Rick Mastracchio and Michael Hopkins, and only the second Christmas Eve spacewalk in NASA history.
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.
Mastracchio and Hopkins removed a faulty ammonia pump during Saturday's outing. On Tuesday, they worked to install a new pump 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."
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.
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The International Space Station fully configured in 2013. (NASA)
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.
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.
Space station managers considered waiting until January for the repair spacewalks, so an unmanned rocket could blast off with supplies from Virginia. But flight controllers were unable to patch the cooling line by remote control, and the orbiting outpost was considered in too vulnerable a state to put off the spacewalking repairs. The delivery mission was bumped, instead, to January.
A bad valve in the ammonia pump caused the 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. This time, NASA reduced the pressure and the task was simplified, allowing the astronauts to get ahead Saturday. Although three spacewalks were scheduled this time around, Mastracchio and Hopkins' advance work allowed NASA to squeeze everything into two, barring any problems Tuesday.
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 entered his suit, making it unusable this week.
During the rest of the spacewalk, however, the suits remained dry. 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. Midway through Tuesday's spacewalk, no water leakage had been reported.
A Moscow-led spacewalk, meanwhile, is set for Friday. Two Russian crew members will install new cameras and fresh experiments outside.
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Online:
NASA: http://www.nasa.gov/mission_pages/station/main/index.html

Copyright © 2013 The Associated Press. All rights reserved.

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Astronauts leave space station to replace cooling pump
By Irene Klotz
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CAPE CANAVERAL, Florida (Reuters) - Two NASA astronauts floated outside the International Space Station on Tuesday for a second and final spacewalk to fix the outpost's critical cooling system.
Flight engineers Rick Mastracchio and Mike Hopkins were slated to spend about 6 1/2 hours outside the station to install a new ammonia cooling system pump. A nonworking unit was removed during a spacewalk on Saturday.
"Let's get to work," Hopkins said as left the station's Quest airlock just before 7 a.m. EST as it soared 260 miles over Mongolia.
The spacewalk was broadcast live on NASA Television.
Hopkins, in his second spacewalk, was due to attach himself to the end of the station's 58-foot-long (17.7-meter) robotic arm for a ride over to where the spare pump is located.
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Flight engineers Michael Hopkins and Richard Mastracchio perform a series of spacewalks outside the …
Flying the arm from a control post inside the station's Destiny laboratory was Japanese astronaut Koichi Wakata, who is due to take over command of the complex, a project of 15 nations, in March. Wakata's backup was current Commander Oleg Kotov, one of three Russian cosmonauts aboard the space station.
Meanwhile Mastracchio, a veteran of seven spacewalks, rummaged through storage bags outside the station for the tools needed to hook up the new pump's electrical connections and ammonia fluid lines.
The U.S. side of the $100 billion space 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, 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.
During Saturday's spacewalk, Mastracchio and Hopkins removed the failed pump and put it in a temporary storage location outside the station.
NASA is considering a possible future spacewalk to repair the pump and keep it as another spare. In addition to the new pump being installed on Tuesday, the station currently has two other spares.
Saturday's outing was NASA's first spacewalk 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 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 homemade snorkels that could draw air from the belly of the spacesuits in case the problem reoccurred.
No leaks were reported during Saturday's spacewalk.
(Editing by Kevin Gray and Maureen Bavdek)

Copyright © 2013 Reuters Limited. All rights reserved.

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NASA astronauts step out on Christmas Eve spacewalk
By Kerry Sheridan
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Washington (AFP) - Two NASA astronauts stepped out Tuesday on a rare Christmas Eve spacewalk to wrap up repairs to an equipment cooling system at the International Space Station.
Americans Rick Mastracchio, 53, and Mike Hopkins, 44, floated outside the orbiting lab on a second outing to replace an ammonia pump module whose internal control valve failed December 11.
Their task was to retrieve a spare pump module from an external stowage platform and install it and, despite recent concerns about leaking spacesuits, the spacewalk got off to a smooth start.
After about two hours of maneuvers outside the station, Hopkins, riding a 57-foot (15-meter) robotic arm operated from inside the station by Japanese astronaut Koichi Wakata, managed to unhook all the connectors on the spare pump module.
"Okay, my friend you have yourself a pump module," said a NASA official at mission control in Houston, overheard in footage broadcast live on the space agency's online television station.
With his boots affixed to the Canadian-made arm, Hopkins' next adventure was to grasp the refrigerator-sized pump module as Wakata maneuvered him over to its installation location.
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US astronaut Rick Mastracchio during a space suit test prior to blast off to the International Space …
The team made swift work of the first spacewalk on Saturday, disconnecting and pulling out the old cooling pump that regulates the temperature of equipment at the orbiting space lab.
They managed to complete what had been seen as almost two days' worth of work in a single outing that lasted just five and a half hours, ending an hour earlier than planned.
Wakata, of the Japan Aerospace Exploration Agency, 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 is 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.
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A NASA TV still image shows the International Space Station during an spacewalk by NASA astronauts R …
On Saturday, a "small amount of water" had entered his suit's cooling system in the space 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.
Tuesday's spacewalk was expected to last six and a half hours, which the US space agency estimated would be enough time to complete the repair job.
Hopkins and Mastracchio must complete five electrical connections and four fluid connections before the pump can be activated.
NASA said tests will be done on the new pump later Tuesday to see how well it is working.
The spacewalk marks the second of Hopkins' career, and the eighth for Mastracchio.
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.
Later this week, Russian cosmonauts Oleg Kotov and Sergey Ryazanskiy will make a spacewalk on December 27 to install a pair of high-fidelity cameras on the Zvezda service module and to do maintenance on the Russian segment of the station.

Copyright © 2013 Agence France Presse. All rights reserved.

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NASA Astronauts Begin Christmas Eve Spacewalk for Space Station Repairs
by Megan Gannon, News Editor | December 24, 2013 06:55am ET
NASA astronaut Rick Mastracchio moves toward the International Space Station's robotic arm as the station moves into daylight on Dec. 24, 2013.
Credit: NASA TV View full size image
Two American astronauts are spending Christmas Eve working in the vacuum of space to hopefully fix the vital cooling system aboard the International Space Station.
NASA astronauts Mike Hopkins and Rick Mastracchio officially started the spacewalk at 6:53 a.m. EST (1153 GMT). The two astronauts ventured outside of the space station's Quest airlock shortly afterwards, getting to work on their second spacewalk in four days. You can watch the spacewalk live on SPACE.com today (Dec. 24) via NASA TV.
NASA astronaut Mike Hopkins floats outside the International Space Station on Dec. 24, 2013.
Credit: NASA TV
View full size image
"In this holiday way of giving, we're giving you a spacewalk today," NASA spokesman Rob Navias said during NASA TV's coverage of the spacewalk. Today's spacewalk is the second-ever Christmas Eve EVA (extra-vehicular activity, another term for spacewalk). The first took place 14 years ago as space shuttle Discovery astronauts Steve Smith and John Grunsfeld spent 8 hours and 8 minutes installing upgrades and new insulation on the Hubble Space Telescope. [See Photos from the Spacewalks to Fix the Station's Vital Cooling System]
During today's 6.5-hour spacewalk, Hopkins and Mastracchio will work to replace a faulty pump module that helps cool equipment inside and outside of the space laboratory. Since part of the pump failed on Dec. 11, non-critical systems and science experiments in two of the station's laboratories have been shut down.
NASA officials have said the six astronauts currently living inside the space station are not in any immediate danger, but the series of spacewalks is necessary to get the orbiting outpost back to normal.
On Dec. 21, Hopkins and Mastracchio performed the first urgent spacewalk in which they successfully removed the failed refrigerator-size pump module and stored it on a nearby platform ahead of schedule. During today's walk, the astronauts will install a replacement pump module stored on the station's exterior.
If the astronauts' work goes as planned, NASA officials said a third spacewalk probably won't be necessary, and the two astronauts will have a quiet Christmas Day.
Tuesday's spacewalk — the eighth for Mastracchio and the second for Hopkins — was originally scheduled for Monday (Dec. 23), but it was delayed because of a problem with Mastracchio's spacesuit. According to NASA, a small amount of water entered the suit's cooling system during the repressurization of the airlock on Saturday after the first spacewalk ended.
Mastracchio is wearing a different spacesuit for Tuesday's extra-vehicular activity. Space agency officials say the issue is unrelated to the leak that flooded Italian astronaut Luca Parmitano's spacesuit during a spacewalk in July.
Because of the quickly planned spacewalks, the first official cargo mission of Orbital Sciences' Cygnus spacecraft had to be postponed. The unmanned freighter, packed with science experiments and supplies, was set to launch to the International Space Station on Dec. 19 from the Mid-Atlantic Regional Spaceport at the NASA Wallops Flight Facility in Virginia. Now NASA officials said that liftoff will not occur before Jan. 7, 2014.
Hopkins and Mastracchio's spacewalk will also be the 176th spacewalk overall in support of the assembly and maintenance of the $100 billion International Space Station, which has been continuously inhabited by rotating crews of astronauts since 2000.
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