NASA astronauts begin urgent spacewalking repairs

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NASA astronauts begin urgent spacewalking repairs
Associated Press
By MARCIA DUNN  1 hour ago



In this image made from video provided by NASA, astronaut Rick Mastracchio performs a space walk outside the International Space Station on Saturday, Dec. 21, 2013. Mastracchio and Michael Hopkins ventured out of the station to try to revive a crippled cooling line. (AP Photo/NASA)



CAPE CANAVERAL, Fla. (AP) — Astronauts sailed through the first of a series of urgent repair spacewalks Saturday to revive a crippled cooling line at the International Space Station.

The two Americans on the crew, Rick Mastracchio and Michael Hopkins, successfully removed an ammonia pump with a bad valve __ well ahead of schedule. That task had been planned for the next spacewalk on Monday.

"An early Christmas," observed Mission Control as Mastracchio pulled the refrigerator-size pump away from its nesting spot.

If Mastracchio and Hopkins keep up the quick work, two spacewalks will be enough to complete the installation of a spare pump and a third spacewalk will not be needed on Christmas Day as originally anticipated.

The breakdown 10 days earlier left one of two identical cooling loops too cold and forced the astronauts to turn off all nonessential equipment inside the orbiting lab, bringing scientific research to a near-halt and leaving the station in a vulnerable state.

Mastracchio managed to unhook all four ammonia fluid lines on the pump with relative ease, occasionally releasing a flurry of frozen ammonia flakes that brushed against his suit. Next he undid the electrical connections. A small O-ring floated away, but he managed to retrieve it.

"I got it, I got it, I got it. Barely," Mastracchio said as he stretched out his hand.

"Don't let that go, that's a stocking stuffer," Mission Control replied.

"Don't tell my wife," Mastracchio said, chuckling, as he put it in a small pouch for trash.

Mastracchio, a seven-time spacewalker, and Hopkins, making his first, wore extra safety gear as they worked outside. NASA wanted to prevent a recurrence of the helmet flooding that nearly drowned an astronaut last summer, so Saturday's spacewalkers had snorkels in their suits and water-absorbent pads in their helmets.

Midway through the spacewalk, the spacewalkers were still dry. But Mastracchio's toes were so cold that he had to crank up the heat in his boots. Mission Control worried aloud whether it was wise to stretch the spacewalk from the planned 6½ hours to 7½ hours to get ahead, given Mastracchio's discomfort. But he assured everyone he'd be fine once he warmed up.

Adding to the excitement 260 miles up, a smoke alarm went off in the space station as the astronauts toiled outside. It was quickly found to be a false alarm, and Mission Control reassuringly told the crew to continue with the spacewalk.

The pump replacement is a huge undertaking attempted only once before, back in 2010 on this very unit. The two astronauts who tackled the job three years ago were in Mission Control, offering guidance. Mastracchio promised to bring back a wire tie installed on the pump by the previous spacewalkers. "Oh, awesome, thanks Rick," replied the astronaut in Mission Control who put it on.

The 780-pound pump is about the size of a double-door refrigerator and extremely cumbersome to handle, with plumbing full of toxic ammonia. Any traces of ammonia on the spacesuits have to be dissipated by the time the astronauts go back inside, to avoid further contamination.

NASA's plan initially called for the pump to be disconnected Saturday, pulled out Monday and a fresh spare put in, and then all the hookups of the new pump completed Wednesday. But if the work is finished on the first two spacewalks, the third won't be needed.

In the days following the Dec. 11 breakdown, flight controllers attempted in vain to fix the bad valve through remote commanding. Then they tried using a different valve to regulate the temperature of the overly cold loop, with some success. But last Tuesday, NASA decided the situation was severe enough to press ahead with the spacewalks. Although the astronauts were safe and comfortable, NASA did not want to risk another failure and a potential loss of the entire cooling system, needed to radiate the heat generated by on-board equipment.

NASA delayed a delivery mission from Wallops Island, Va., to accommodate the spacewalks. That flight by Orbital Sciences Corp., which should have occurred this past week, is now targeted for Jan. 7.

Until Saturday, U.S. spacewalks had been on hold since July, when an Italian astronaut's helmet was flooded with water from the cooling system of his suit. Luca Parmitano barely got back inside alive.

Engineers traced the problem to a device in the suit that turned out to be contaminated — how and why, no one yet knows.

For Saturday's spacewalk, Hopkins wore Parmitano's suit, albeit with newly installed and thoroughly tested components.

Just in case, NASA had Mastracchio and Hopkins build snorkels out of plastic tubing from their suits, before going out. The snorkels will be used in case water starts building up in their helmets. They also put absorbent pads in their helmets; the pads were launched from Earth following the July scare.

Besides the two Americans, three Russians and one Japanese are living on the space station, all men.

___

Online:

NASA: http://www.nasa.gov/mission_pages/station/main/index.html


http://news.yahoo.com/nasa-astronauts-begin-urgent-spacewalking-repairs-121103907.html

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US spacewalkers get ready for orbiting lab repairs
AFP
By Kerry Sheridan  12 hours ago



The SpaceX capsule Dragon attached to the Canada Arm at the International Space Station (ISS) on March 3, 2013



Washington (AFP) - Two American astronauts are to step out Saturday on the first of three spacewalks to replace a broken cooling pump at the orbiting International Space Station.

The spacewalk is set to begin at 7:10 am (1210 GMT) and last six and a half hours, NASA said.

As the ISS spins around the Earth at a speed of five miles (eight kilometers) per second, veteran spacewalker Rick Mastracchio will lead the way, followed by Mike Hopkins, making his first venture outside the global research lab.

From the inside, Japanese astronaut Koichi Wakata will operate the station's 50-foot (15-meter) robotic arm, hoisting Mastracchio and hefty equipment from one section of the lab to another.

"There are quite a bit of arm maneuvers throughout all of these EVAs so I'm sure Koichi will be getting a workout," said lead spacewalk officer Allison Bolinger, using the NASA acronym for spacewalk: extravehicular activity (EVA).

While Mastracchio, 53, soars around with his boots attached to a foot-plate on the robotic arm, Hopkins, 44, will be the designated free-floating astronaut of the day.



Mikhail Tyurin of Roscosmos (Bottom), Flight Engineer Koichi Wakata and Flight Engineer Rick Mastracchio


The men's first task is to disconnect the ammonia pump, which is about the size of a refrigerator.

On the second spacewalk, set for Monday, the astronauts are to remove the pump so it can be replaced with a spare that was already stowed at the ISS.

A third spacewalk is planned for Christmas Day, when the failed pump will be shuttled away and final installations made on its replacement.

However, there is a chance the astronauts will be able to complete all their work in two spacewalks, NASA has said.

If not, the Christmas Day outing would be the first since 1974, when a pair of NASA astronauts "stepped outside the Skylab space station to retrieve film from a telescope and photograph Comet Kohoutek," the US space agency said.



People take photographs as Russia's Soyuz TMA-11M spacecraft blasts off


The urgent spacewalks were called for this week due to a faulty valve that caused a partial shutdown in the system that regulates equipment temperature at the space station.

Engineers tried to fix the problem from the ground, but eventually decided they needed to replace the ammonia pump.

The six-man crew was never in danger, but NASA wanted to fix the problem sooner rather than later, agency officials said.

The spacewalks meant the first regular commercial cargo supply mission by Orbital Sciences' Cygnus craft, which had been planned for earlier in the week, was postponed until next year.

NASA also had to rig up some last-minute contingency gear inside the American-made spacesuits, which have not been used since a helmet water leak nearly drowned a European astronaut in July.

Now the helmets carry an extra absorption pad and a snorkel inside, just in case.

The investigation into the cause of the helmet leak is ongoing. Hopkins will be wearing the suit that had the problem, though its inner water pump has been replaced.

Dina Contella, International Space Station flight director, told reporters on Wednesday the space agency is "confident that this suit is a very clean suit and ready to go."


http://news.yahoo.com/us-spacewalkers-ready-orbiting-lab-repairs-022612719.html

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Space Station Showing Its Age
Astronauts Plan Spacewalk to Replace Faulty Coolant System, in Latest Maintenance Issue
By Andy Pasztor  Dec. 19, 2013 7:33 p.m. ET

 

Rick Mastracchio checks spacesuits in the space station's Quest airlock. NASA TV


U.S. astronauts are poised to begin a series of spacewalks as soon as Saturday to replace a coolant system aboard the international space station, a harbinger of the increasing maintenance the aging laboratory is likely to need in coming years as it orbits Earth at more than 17,000 miles an hour.

The space station, launched in 1998, is run by a partnership of 15 nations to support scientific research. It was designed to remain structurally sound for as many as 60 years, but in the past 10 years it has experienced a number of problems, from air leaks to computer glitches.

The latest trouble, with the coolant system, doesn't pose an immediate hazard to crew members or experiments. The refrigerator-size unit is one of two that use ammonia to control the temperature of vital electrical components.

After a week spent developing a software patch as a makeshift solution for a malfunctioning valve, National Aeronautics and Space Administration officials decided instead to swap out the part. The agency scheduled three spacewalks totaling about 18 hours to do the job.

The space station will at some point need additional part replacements and upgrades, industry and U.S. government officials say. Some older systems increasingly are showing the results of wear and tear from exposure to radiation, micro-meteoroids, docking and everyday activities of six crew members.

With solar arrays and electrical systems among the most prone to damage, NASA and  Boeing Co.  BA +1.11%     , the prime contractor for NASA's portion of the station, are conducting a detailed study to identify the scope and timing of major refurbishment efforts that are needed to keep operating past the end of the decade.

The agency spends roughly $3 billion annually to operate the facility. According to industry officials, some preliminary estimates peg the additional cost of replacing just the main solar arrays at hundreds of millions of dollars. NASA hasn't commented on specific cost projections.

Congress and the White House have agreed with foreign partners to keep the space station operational until at least 2020, but agency officials and other proponents are looking for ways to stretch that to 2028. "I expect NASA will want to extend it for questions of international cooperation and pride," said Joseph Dyer, who heads the agency's independent safety advisory panel.

Space agencies representing the U.S., Russia, Canada and Japan, along with and 11 participating European countries, will decide the fate of the station. But according to industry and U.S. space officials, budget and political factors in many of those countries have reduced the desire to keep going past 2020.

Russian officials, for example, have suggested they may go their own way and develop a rival station. China and India recently launched separate unmanned spacecraft to the moon and Mars. And Beijing has sketched out an ambitious path to construct and launch its own smaller scientific outpost in low-earth orbit.

Amid such uncertainty, William Gerstenmaier, who heads NASA's manned exploration programs, has said the U.S. and its partners may have to decide by the end of 2014 whether it is feasible to keep the station functioning through 2028. In a presentation earlier this month to part of the agency's outside advisory panel, Mr. Gerstenmaier said such a move would spur commercial space projects, help move human exploration deeper into space and promote global partnerships.

Sam Scimemi, another senior NASA official, told the same gathering that it is likely to take until "the mid-2020s" until research aboard the station identifies and finds ways to mitigate health hazards likely to be faced by astronauts venturing deeper into space.

But fiscal realities may intervene. The station "is starting to enter a period when you can see the aging issues perhaps begin to rear their head," said Mr. Dyer. The committee he heads is likely to deal with some of those issues when it releases its annual report next month.

Meanwhile, some of the new scientific research slated for the station includes studying the behavior of stem cells and bone tumors in orbit, with the hope of developing more-effective cancer fighting drugs. Within four years, commercial crew taxis may start shuttling U.S. astronauts to and from low-earth orbit, potentially putting pressure on NASA to extend operations past 2020 to justify federal funds used to partially support that transport.


http://online.wsj.com/news/articles/SB10001424052702304773104579268611258089806

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NASA Astronauts Perform 1st of 3 Holiday Spacewalks Saturday: Watch Live
SPACE.com
By Miriam Kramer, Staff Writer  17 hours ago



Astronaut Rick Mastracchio tweeted this photo on Dec. 17, 2013, from the International Space Station



On Saturday morning (Dec. 21), two NASA astronauts will venture outside the International Space Station to perform the first of potentially three urgent spacewalks to fix the vital cooling system on the orbiting outpost, and you can watch the excursion live online.

NASA astronauts Mike Hopkins and Rick Mastracchio will perform the spacewalk, which is expected to begin the necessary repairs on the outside of the station. NASA TV will broadcast the entire 6.5-hour spacewalk set to begin at 7:10 a.m. EST (1210 GMT) Saturday. Coverage will begin at 6:15 a.m. EST (1115 GMT), and you can watch the spacewalk live on SPACE.com.

Mastracchio and Hopkins are leaving the confines of the station to remove and replace a failed pump module that helps keep equipment inside and outside of the space laboratory cool. The six residents of the space station are not in any immediate danger, but in order to get the station up to its fully functional status, the two astronauts will need to perform a series of quickly planned spacewalks, NASA officials said.

For this first spacewalk, Hopkins and Mastracchio will focus on preparing the failed pump module for removal and getting the replacement module — which is stored on the station's exterior — ready for installation. The next spacewalk is scheduled for Dec. 23, and a third could occur on Christmas Day (Dec. 25), if necessary.

"We refer to it as a contingency spacewalk, and the skills really are fundamental," astronaut Doug Wheelock said of the spacewalks during a NASA TV event Thursday (Dec. 19). "We practice all of these skills, just rehearse them over and over again in the pool. The crew has done these particular skills. The skills are the same, but space always has surprises for us, especially when we go outside."

In 2010, Wheelock and his fellow NASA astronaut Tracy Caldwell Dyson performed a similar series of spacewalks when they had to repair the space station's cooling system. Doug Wheelock and Caldwell Dyson have been helping Mastracchio and Hopkins prepare by running through the spacewalking plans on the ground.

"It's a little bit [of] a different failure we're facing this time around, but the spacewalks to remove the old pump module and replace it with a new spare is exactly the same as what we did in 2010," Wheelock said. "We've had a lot of lessons learned back then, and so we've implemented those changes into our procedure in the way that we prepare our suits and our tools, so we'll be ready to go on Saturday."

Veteran spacewalker Mastracchio has performed six EVAs (extra-vehicular activities, another term for spacewalks) totaling 38 hours and 30 minutes of spacewalk time. Tomorrow's spacewalk will be Hopkins' first. Japanese astronaut Kiochi Wakata will assist them from inside the station tomorrow.

Three Russian cosmonauts also live and work aboard the space station with Mastracchio, Hopkins and Wakata. Oleg Kotov, Sergey Ryazanskiy and Mikhail Tyurin round out the orbiting outpost's Expedition 38 crew.


http://news.yahoo.com/nasa-astronauts-perform-1st-3-holiday-spacewalks-saturday-001521962.html

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Spacewalking Astronauts Remove Faulty Space Station Pump Ahead of Schedule
SPACE.com
By Robert Z. Pearlman, SPACE.com Contributor  1 hour ago



Astronaut Rick Mastracchio holds the failed pump module during a spacewalk Dec. 21.



HOUSTON — Two astronauts working speedily outside the International Space Station removed a faulty pump module ahead of schedule, potentially negating the need for a planned Christmas Day spacewalk as they work to repair the outpost’s critical cooling system.

NASA astronauts Rick Mastracchio and Mike Hopkins ventured outside the space station at 7:01 a.m. EST (1101 GMT) today (Dec. 21), just 10 days after a flow control valve malfunctioned inside the pump module that they were set to remove and replace during another 6.5-hour spacewalk on Monday. Saturday’s spacewalk ended at 12:29 p.m. EST (1729 GMT), five hours and 28 minutes after it began.

Originally, the astronauts were just going to prepare the faulty pump for removal today, but the spacewalkers completed the majority of the planned tasks for Saturday’s spacewalk in just three hours. The astronauts were then given a go by Mission Control in Houston to press ahead with removing the faulty refrigerator-size pump module and stow it on a nearby platform.

“We’re about an hour and a half ahead of the timeline, so, choosing your own adventure, we’re going to go ahead and look forward to doing the pump module exit,” Mission Control advised the astronauts.


Ahead of the spacewalk schedule

The early removal could mean that a third spacewalk planned for Dec. 25, Christmas Day, may not be needed.

The faulty valve, which regulates the temperature of ammonia flowing through the pump, ceased working properly on Dec. 11. Non-critical systems and science experiments in two of the station’s laboratories have been powered down since.

Saturday’s spacewalk was originally focused on only disconnecting the fluid lines from the failed pump module and installing a “jumper” box to keep the ammonia from over pressurizing during the pump’s replacement.

Working along the starboard, or right, side of the station’s backbone truss, Mastracchio (riding on the end of the Canadarm2 robotic arm) and Hopkins first set about demating “quick disconnect” fluid lines from the faulty pump.

As their name implies, the quick disconnects were designed to be plugged in and out, but past spacewalks, including an August 2010 outing to replace the same pump module, ran into problems getting the pressurized lines loose. Learning from previous experiences, the pressure in the lines was reduced in preparation for Saturday’s spacewalk.

As such, Mastracchio and Hopkins were able to disconnect the first two fluid lines with little trouble. The first of the lines was unplugged an hour and 45 minutes into the spacewalk.


Space station snow

As the lines were loosened though, the spacewalkers did report seeing “snow” — flakes of frozen ammonia — floating from the connectors.

"I do see some snow, very little," Masstrachio said. "Very small flakes coming from the forward side of the [quick disconnect]. Very small flakes."

Mastracchio, responding to an inquiry from Mission Control, confirmed that the flakes may have landed on his and Hopkins’ spacesuit. One of the dangers of working with the toxic ammonia is contamination, though the small solid flakes were not of great concern.

With the first two lines released from the pump module, Mastracchio and Hopkins next worked to connect them to a "jumper" box, which routes the ammonia back into the coolant loop to keep it in a liquid phase. That task was followed by the astronauts disconnecting the remaining fluid lines and five electrical lines from the pump module to be replaced.

“Very nice, came out beautifully,” Masstracchio radioed, commenting on the release of one of the lines. “Almost no loads on that thing at all, came off very cleanly.”


'Very, very cold'

It was the ease in which the lines were removed that allowed the time for the pump module to be removed. Mastracchio had only one note of concern for the additional work: his cold toes.

“The only issue that I personally am having is it's very, very cold,” Mastracchio said. “Because I'm just floating here on the [robotic] arm, I've got very, very good airflow in my boots but my toes are quite cold.”

To remove the 780-pound (355 kilogram) pump module, four bolts holding the module in place needed to be released. Mastracchio, still riding on the arm, then pulled the bulky pump out of the space station’s truss part of the way so Hopkins could install a robotic arm grapple fixture on its side.

Working from inside the station, Japan Aerospace Exploration Agency (JAXA) astronaut Koichi Wakata then controlled the arm to “fly” Mastracchio, holding the pump module, to the pump’s temporary storage location, called the POA (Payload/Orbital Replacement Unit Accommodations).

At the start of the spacewalk, Hopkins had also been scheduled to ready the replacement pump module to be installed on Monday, but after consulting with Mastracchio, Mission Control agreed to end the outing after the faulty pump module was stowed.


Snorkels in spacesuits

Saturday’s extra-vehicular activity (EVA or spacewalk) was the first to use U.S. spacesuits since July, when water unexpectedly flooded into Italian astronaut Luca Parmitano’s helmet. Hopkins wore Parmitano’s suit for this spacewalk but with a new filter assembly, replacing the faulty component.

As a precaution, NASA engineers had both astronauts outfit their suits with absorption pads and makeshift snorkels, but they were not needed. Mastracchio’s and Hopkins’ helmets remained water-free throughout the spacewalk, as confirmed during periodic checks.

This was Mastracchio’s seventh career spacewalk and Hopkins’ first. Overall, it was the 175th spacewalk in support of the assembly and maintenance of the International Space Station.

Monday’s spacewalk will pick up where Saturday’s excursion ended, with Mastracchio and Hopkins working to install the spare pump module where the faulty unit had been removed. Depending on how far they get with the new pump module’s connections on Monday, a Christmas day outing planned to reconnect the quick disconnect fluid lines and stow the old pump module for possible future servicing may not be necessary.


http://news.yahoo.com/spacewalking-astronauts-remove-faulty-space-station-pump-ahead-174513914.html

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NASA Astronauts End Spacewalk Early After 5 Hours
Good Morning America
By SUSANNA KIM  13 minutes ago






Two American astronauts conducted an urgent repair outside the International Space Station Saturday during a spacewalk that lasted five hours and 28 minutes.

The astronauts ran about an hour and a half ahead of what NASA expected to be their timeline.

Rich Mastracchio and Mike Hopkins, Expedition 38 Flight Engineers, began at 7:01 am EST Saturday morning to replace a degraded ammonia pump module associated with one of the station's two cooling loops that keeps internal and external equipment cool, NASA said.

Mastracchio, the lead spacewalker, conducted six previous spacewalks, and holds the record for the 14th longest number of hours of spacewalking. Hopkins made his first spacewalk.

NASA's website offered the public a live video feed showing the astronauts and Mission Control.

During the repairs, the astronauts communicated with Mission Control Houston about the procedure. The spacewalk ended after five hours, 28 minutes and 11 seconds, shorter than the 6.5-hour expected spacewalk, because Mastracchio complained about chilly temperatures in his space suit.

After the cooling line broke down on Dec. 11 at the International Space Station, flight controllers tried but failed to fix the bad valve through remote commanding, the Associated Press reported.

The 780-pound pump is about the size of a double-door refrigerator and difficult to handle, with plumbing full of toxic ammonia, AP reported.

NASA said Saturday's spacewalk is the 175th in support of space station assembly and maintenance.

The work of the two astronauts on Saturday is part of a series of spacewalks to replace the ammonia pump module. The astronauts prepared the pump for removal on Saturday and is expected to be replaced during a spacewalk on Monday.

NASA says a third spacewalk would occur on Christmas Day if necessary to finalize the installation of the replacement pump module. It would be the first Christmas spacewalk for NASA.

The two astronauts received guidance on the spacewalk procedures from NASA astronauts Doug Wheelock and Tracy Caldwell-Dyson, who replaced the ammonia pump at the same location during three spacewalks in August 2010, NASA said.


http://news.yahoo.com/nasa-astronauts-end-spacewalk-early-5-hours-182229365--abc-news-topstories.html

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Spacewalking astronauts make speedy station repairs
AFP
By Kerry Sheridan  2 hours ago



This March 7, 2011 A NASA image shows a close-up of the International Space Station in an image photographed by an STS-133 crew member on space shuttle Discovery



Washington (AFP) - Two American astronauts made quick progress during a spacewalk outside the International Space Station on Saturday to replace a broken equipment cooling system, NASA said.

The risky outing was called for earlier this week after a cooling valve failed on December 11, leaving NASA no other option but to replace an ammonia pump at the orbiting lab.

The problem caused a partial shutdown in the system that regulates equipment temperature at the space station, but did not pose any danger to the six-man crew, NASA said.

Saturday's spacewalk began at 7:01 am (1201 GMT) and ended at 12:29 (1729 GMT), an hour earlier than planned.

Astronauts made fast work of their key task for the day, disconnecting the old pump, and were also able to take on the extra task of removing the pump.

A second spacewalk is set for Monday to work on installing the new pump module.



A NASA photo obtained June 18, 2013 shows a view of Earth as seen from the Cupola on the Earth-facing side


"They will be replanning that spacewalk," a NASA commentator said, in light of the extra progress made on Saturday.

The venture outside the space station was the seventh for veteran spacewalker Rick Mastracchio, 53, and the first for rookie Mike Hopkins, 44.

Japanese astronaut Koichi Wakata operated the station's 50-foot (15-meter) robotic arm, hoisting Mastracchio and the refrigerator-sized ammonia pump module from one section of the lab to another.

With Mastracchio grasping the 780-pound (350-kilogram) module and unable to see where he was going, Wakata eased him into the right spot for stowing the pump.

The two US astronauts sported helmet cameras, and NASA TV showed the operations in real-time from the perspective of the spacewalkers.



NASA images released on December 21, 2013 show two US astronauts who stepped outside the International Space Station


NASA also had to rig up some last-minute contingency gear inside the US-made spacesuits, which had not been used since a helmet water leak nearly drowned a European astronaut in July.

Now the helmets carry an extra absorption pad and a snorkel inside, in case there is a malfunction in the water pump system in the 35-year-old suits.

The investigation into the cause of the helmet leak is ongoing. Hopkins wore the suit that had the problem, though its inner water pump had been replaced.

NASA checked with the astronauts at regular intervals throughout the day to make sure they were not feeling any "squishy" sensation behind their necks, which might have indicated a water buildup and would cut short the spacewalk, space agency commentators said.

The astronauts reported dry conditions and no problems in their spacesuits or gloves, NASA said.

At one point, Mastracchio said his toes were getting cold, but they warmed again once he alerted mission control in Houston and heaters were activated in his spacesuit boots.

The astronauts trained for the emergency spacewalks by watching video of a previous outing to replace an ammonia pump in 2010.

A third spacewalk was initially projected for December 25, but it is possible the astronauts will be able to complete all their work Monday.

If not, the Christmas Day outing would be the first since 1974, when a pair of NASA astronauts did work outside the Skylab space station.

Saturday's spacewalk was the 175th for maintenance and repair aboard the 15-year-old ISS, NASA said.


http://news.yahoo.com/us-astronauts-begin-spacewalk-station-repairs-001514723.html

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Astronauts nail first spacewalk to fix station's cooling system
Reuters
By Irene Klotz  1 hour ago



The International Space Station crew opens a hatch at 4:10am EDT (8:10am GMT) to begin unloading cargo in this NASA handout photo



CAPE CANAVERAL, Florida (Reuters) - Two NASA astronauts, their spacesuits rigged with snorkels in case of a water leak, floated outside the International Space Station for 5-1/2 hours on Saturday, successfully completing the first steps to fix the outpost's cooling system.

The spacewalk, which was broadcast live on NASA Television, was the first for NASA since July when the spacesuit helmet worn by Italian astronaut Luca Parmitano began filling with water, a situation that could have caused him to drown.

No such leaks were detected in Saturday's spacewalk, the first of two or possibly three that will be needed to complete the cooling system repair.

The operation was prompted by the December 11 shutdown of one of the station's two U.S. ammonia cooling systems, which forced the crew to turn off non-essential equipment and shut down dozens of science experiments.

While the six-member crew is not in danger, the remaining cooling system cannot support the three laboratories and other modules on the U.S. side of the $100 billion station, a project of 15 nations. The Russian side of the station has a separate cooling system.

Engineers at the Johnson Space Center in Houston tried devising ways to bypass a suspected faulty pump valve, but with time running short, managers decided to have astronauts replace the pump, located outside the station, with a spare.

The work, which began shortly after 7 a.m. EST (1200 GMT), went smoothly, with station flight engineers Rick Mastracchio and Mike Hopkins finishing up an hour earlier than expected.

They were able to not only disconnect the old pump, but also remove it from its pallet on the station's exterior truss, a task originally slated for a second spacewalk on Monday. A third spacewalk, if needed, is scheduled for Wednesday.

"Beautiful day. Awesome view," Mastracchio, a veteran of six previous spacewalks, said as opened the airlock's hatch and saw the view from 260 miles above the southern Atlantic Ocean.

He and Hopkins wore spacesuits that were modified to protect them from another possible water leak. The problem in July was traced to contamination in piece of equipment called a fan pump separator that circulates water and air in the spacesuit and removes moisture from air.

How the water-separator portion of the device became clogged remains under investigation.

Hopkins, who was making his first spacewalk, wore Parmitano's spacesuit, but it had been outfitted with a new fan pump separator.

In addition, both Hopkins and Mastracchio rigged their helmets with homemade snorkels, fabricated out of pieces of plastic tubing and Velcro, which they could have used for breathing in case of another water leak.

The helmets also included water-absorbent pads.


FAILED PUMP

During Saturday's spacewalk, Mastracchio and Hopkins disconnected electrical and fluid lines and removed the 780-pound (354 kg), 5-foot (1.5 meter) wide cooling system pump.

The failed pump, which was then anchored in a temporary storage site, will remain on the station for possible future repair and reuse.

It was installed in 2010 during an unexpectedly difficult series of spacewalks by astronauts Doug Wheelock and Tracy Caldwell Dyson.

"What makes this pump very difficult (to work on) are (the) fluid disconnects because they are so large and they are pressurized and they contain liquid ammonia, so that's a hazard for us if it were to come in contact with us or our suits," Caldwell Dyson said in an interview with a NASA TV mission commentator.

Maintaining focus also can be a challenge, she added. "When you're on one of those pallets, you really have that sensation that you are sticking out on the edge of a skyscraper. Especially when you look down, you see your feet and then you see the Earth going 17,500 mph beneath you, it really does get your attention," she said.

Mastracchio and Hopkins encountered no major problems during Saturday's outing.

"These guys really went out there and were so efficient," Caldwell Dyson said. "It may be more difficult to remove the pump because you don't know exactly what to expect," she added.


http://news.yahoo.com/snorkel-clad-spacewalkers-leave-station-begin-crucial-repair-130446357.html