Spacewalking Astronauts Hopeful New Pump Fixes Space Station Leakhttp://news.yahoo.com/spacewalking-astronauts-hopeful-pump-fixes-space-station-leak-173443062.html (http://news.yahoo.com/spacewalking-astronauts-hopeful-pump-fixes-space-station-leak-173443062.html)
By Tariq Malik | SPACE.com – 3 hrs ago...(http://l.yimg.com/bt/api/res/1.2/qr_PfkBlUSvX4AgH8qT5Xg--/YXBwaWQ9eW5ld3M7Zmk9aW5zZXQ7aD00MzQ7cT03OTt3PTU3NQ--/http://media.zenfs.com/en_US/News/SPACE.com/Spacewalking_Astronauts_Hopeful_New_Pump-ee0685bc7d0dc634d88c8c62585bbafd)
NASA astronauts Chris Cassidy (top) and Tom Marshburn work outside the International Space Station after replacing an ammonia coolant pump on May 11, 2013.
Two spacewalking astronauts may have fixed an ammonia leak outside the International Space Station today (May 11), perhaps bringing the outpost's vital cooling system back up to full strength.
Clad in bulky spacesuits, NASA astronauts Chris Cassidy and Tom Marshburn replaced a pump control box thought to be responsible for the leak of ammonia, which cools down the orbiting lab's systems. It looks like this fix did the trick, as no ammonia flakes were seen streaming into space when Mission Control turned on the newly installed gear.
"We're not seeing anything," Cassidy said at around 12:35 p.m. EDT (1635 GMT), several minutes after the pump was turned on. "No snow." [Emergency Spacewalk to Fix Space Station Leak in Photos]
NASA officials stopped short of declaring total victory, however, saying that time will tell if the fix holds.
"It will take some diagnostics, still, over the course of the next several days by the thermal systems specialists to fully determine that we have solved the problem of the ammonia leak," NASA spokesperson Rob Navias said during live mission commentary. "But so far, so good."
An emergency spacewalk
Cassidy and Marshburn floated outside the space station at 8:44 a.m. EDT (1244 GMT) today, beginning what officials described as a six-hour detective's investigation to find — and hopefully fix — the ammonia leak.
Cassidy, who led the spacewalk, reported seeing "no smoking gun" as he and Marshburn began their inspection of the old ammonia pump control box, one of several on the space station's far left segment, known as the Port 6 truss. It is part of the cooling system for the two wing-like solar arrays extending from the Port 6 segment.
Upon removing the box, the spacewalkers still saw no signs of ammonia flakes.
"It looks really, really clean, surprisingly so," Cassidy said while peering deep inside the box using what looked like a dentist's mirror.
The ammonia leak was first spotted by space station astronauts on Thursday (May 9), when the crew reported seeing flakes of frozen coolant floating outside. They recorded video of the ammonia leak and sent it down to Mission Control for analysis.
While the leak posed no danger to the space station's crew, it could have impacted the amount of power available for daily operations on the orbiting laboratory if left unchecked, NASA officials said. So Cassidy and Marshburn were sent out on an emergency spacewalk to attempt a fix.
The roughly 48-hour turnaround made this the fastest spacewalk plan of its kind ever devised for a space station crew, mission managers have said.
By about 1:00 p.m. EDT (1700 GMT), a little more than four hours into the spacewalk, Cassidy and Marshburn were getting ready to head back to a space station airlock, where they must clean their spacesuits to make sure they don't bring any toxic ammonia into the orbiting lab.
A history of ammonia leaks
This is not the first time astronauts have had to tackle ammonia leaks in the space station's cooling system during a spacewalk.
Last year, astronauts Sunita Williams of NASA and Akihiko Hoshide of Japan performed a spacewalk to fix a leak that was also found on the Port 6 truss. That ammonia leak was in the same coolant loop as the current leak, but engineers do not yet know if the two leaks are related.
The station's Port 6 truss is the oldest piece of the space station's scaffolding-like backbone and carries two of the outpost's eight wing-like solar arrays. It launched in November 2000 and was originally installed on the station's roof, towering over the orbiting lap. In 2007, visiting shuttle astronauts relocated the P6 truss to its final location on the station's far left side.
This was the fourth spacewalk for both Marshburn and Cassidy, and the 168th total to support space station assembly and maintenance. Inside the International Space Station, commander Chris Hadfield of Canada and Russian cosmonauts Roman Romanenko, Alexander Misurkin and Pavel Vinogradov followed the spacewalkers' progress.
Today's spacewalk comes just two days before Hadfield, Marshburn and Romanenko are due to return to Earth to end their five-month mission in space.
The three men are due to leave the space station on Monday (May 13) and land on the steppes of Kazakhstan in Central Asia. Those plans are still going forward, space station mission managers said.
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In this image made from video provided by NASA, astronaut Christopher Cassidy, foreground, holds a power wrench as he stows away a suspect coolant pump on the International Space Station on Saturday, May 11, 2013. Thomas Marshburn is at left. The two astronauts made the spacewalk to replace the pump after flakes of frozen ammonia coolant were spotted outside the station on Thursday. (AP Photo/NASA)
CAPE CANAVERAL, Fla. (AP) — Astronauts making a rare, hastily planned spacewalk replaced a pump outside the International Space Station on Saturday in hopes of plugging a serious ammonia leak.
The prospects of success grew as the minutes passed and no frozen flecks of ammonia appeared. Mission Control said it appeared as though the leak may have been plugged, although additional monitoring over the next few weeks, if not months, will be needed before declaring a victory.
"No evidence of any ammonia leakage whatsoever. We have an airtight system — at the moment," Mission Control reported.
Christopher Cassidy and Thomas Marshburn installed the new pump after removing the old one suspected of spewing flakes of frozen ammonia coolant two days earlier. They uncovered "no smoking guns" responsible for the leak and consequently kept a sharp lookout for any icy flecks that might appear from the massive frame that holds the solar panels on the left side.
"Let us know if you see anything," Mission Control urged as the fresh pump was cranked up. Thirty minutes later, all was still well. "No snow," the astronauts radioed.
"We have our eyes on it and haven't seen a thing," Marshburn said.
NASA said the leak, while significant, never jeopardized crew safety. But managers wanted to deal with the trouble now, while it's fresh and before Marshburn returns to Earth in just a few days.
The space agency never before staged such a fast, impromptu spacewalk for a station crew. Even during the shuttle days, unplanned spacewalks were uncommon.
The ammonia pump was the chief suspect going into Saturday's spacewalk. So it was disheartening for NASA, at first, as Cassidy and Marshburn reported nothing amiss on or around the old pump.
"All the pipes look shiny clean, no crud," Cassidy said as he used a long, dentist-like mirror to peer into tight, deep openings.
"I can't give you any good data other than nominal, unfortunately. No smoking guns."
Engineers determined there was nothing to lose by installing a new pump, despite the lack of visible damage to the old one. The entire team — weary and stressed by the frantic pace of the past two days — gained more and more confidence as the 5 1/2-hour spacewalk drew to a close with no flecks of ammonia popping up.
"Gloved fingers crossed," space station commander Chris Hadfield said in a tweet from inside. "No leaks!" he wrote a half-hour later.
Flight controllers in Houston worked furiously to get ready for Saturday's operation, completing all the required preparation in under 48 hours. The astronauts trained for just such an emergency scenario before they rocketed into orbit; the repair job is among NASA's so-called Big 12.
This area on the space station is prone to leaks.
The ammonia coursing through the plumbing is used to cool the space station's electronic equipment. There are eight of these power channels, and all seven others were operating normally. As a result, life for the six space station residents was pretty much unaffected, aside from the drama unfolding Saturday 255 miles above the planet. The loss of two power channels, however, could threaten science experiments and backup equipment.
"We may not have found exactly the smoking gun," Cassidy said, "but to pull off what this team did yesterday and today, working practically 48 straight hours, it was a remarkable effort on everybody's behalf."
NASA's space station program manager Mike Suffredini said it's a mystery as to why the leak erupted. Possibilities include a micrometeorite strike or a flawed seal. Ammonia already had been seeping ever so slightly from the location, but the flow increased dramatically Thursday.
Marshburn has been on the space station since December and is set to return to Earth late Monday. Cassidy is a new arrival, on board for just 1½ months.
By coincidence, the two performed a spacewalk at this troublesome spot before, during a shuttle visit in 2009.
"This type of event is what the years of training were for," Hadfield said in a tweet Friday. "A happy, busy crew, working hard, loving life in space."