Spacewalking repairmen replace space station's leaky pump

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By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - A pair of spacewalking astronauts wrapped up a hastily planned repair job on Saturday to replace a suspect coolant pump needed to keep the International Space Station at full power.

NASA astronauts Chris Cassidy and Tom Marshburn put on spacesuits and left the space station's airlock shortly before 9 a.m. EDT to attempt to stem an ammonia coolant leak that cropped up on Thursday.

Over the next four hours, they installed a spare pump, then positioned themselves to check for signs of escaping ammonia ice crystals when the system was turned back on.

"No flakes," Cassidy reported to flight controllers at the Johnson Space Center in Houston.

Engineers will monitor the system over the next several days and beyond to make sure the pump replacement fixed the problem.

"We certainly have come a long way in identifying a potential source," said NASA mission commentator Rob Navias as the astronauts returned to the station's airlock. The entire spacewalk lasted 5-1/2 hours.

The station crew discovered a steady stream of ammonia flakes flowing away from the far left side of the station's exterior frame on Thursday. Flight controllers spent the next 48 hours diagnosing the problem and coming up with potential solutions.

Engineers believed the leak most likely was coming from in or around a 260-pound (118-kg) pump that pushes ammonia throughout the system. The coolant dissipates heat from electronics in space station's solar-powered electrical system.

The station can be reconfigured to compensate for a system shutdown, but if a second problem should occur, that likely would mean a cutback in power available for the experiments.

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Spacewalking repairmen replace space station's leaky pump

Spacewalking Astronauts Hopeful New Pump Fixes Space Station Leak

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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 theammonia leak,"NASA spokesperson Rob Naviassaid 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.

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Spacewalking Astronauts Hopeful New Pump Fixes Space Station Leak

Spacewalkers hopeful new pump fixes space station coolant leak

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Astronaut helmet camera captures video of NASA engineers Chris Cassidy and Tom Marshburn replacing a pump on International Space Station suspected of leaking ammonia.

By Tariq Malik, Space.com

Two spacewalking astronauts may have fixed an ammonia leak outside the International Space Station on Saturday, 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 theleak 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. ET, 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 theammonia leak,"NASA spokesperson Rob Naviassaid 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. ET Saturday, 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.

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Spacewalkers hopeful new pump fixes space station coolant leak

Spacewalkers hopeful new pump control fixes space station coolant leak

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Astronaut helmet camera captures video of NASA engineers Chris Cassidy and Tom Marshburn replacing a pump on International Space Station suspected of leaking ammonia.

By Tariq Malik, Space.com

Two spacewalking astronauts may have fixed an ammonia leak outside the International Space Station on Saturday, 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 theleak 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. ET, 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 theammonia leak,"NASA spokesperson Rob Naviassaid 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. ET Saturday, 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.

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Spacewalkers hopeful new pump control fixes space station coolant leak

Spacewalking Astronauts Hunt for Space Station Ammonia Leak

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Two spacewalking astronauts are hunting for an ammonia leak outside the International Space Station today (May 11) in the hopes of bringing the outpost's vital cooling system back up to full strength.

Clad in bulky spacesuits, NASA astronauts Chris Cassidy and Tom Marshburn floated outside the space station at 8:44 a.m. EDT (1244 GMT), beginning what officials have described as a six-hour detective's investigation in orbit to find - and hopefully fix - the ammonia coolant leak. The space station uses liquid ammonia as a vital coolant to keep its systems cool. You canwatch the spacewalk live here on SPACE.comvia NASA TV.

Cassidy, who is leading today's spacewalk, reported seeing "no smoking gun" as he and Marshburn began their inspection of an ammonia pump control box suspected to be the source of the leak. Later, they removed the box and repoted no signs of flakes of ammonia ice. Cassidy said he did see a brown spot that "looks like a coffee stain" on some equipment, but it is unclear if it is related. Mission Control asked for photos of the spot. [Emergency Spacewalk to Fix Space Station Leak in Photos]

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, leading to today's emergency spacewalk to search for the leak. It is the fastest spacewalk plan of its kind ever devised for a space station crew, mission managers have said.

The primary goal of today's spacewalk is to inspect the suspect ammonia pump control box for any signs of damage or leaks. The box is 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.

While the leak poses no danger to the space station's crew, if it goes unchecked it could impact the amount of power available for daily operations on the orbiting laboratory, mission managers have said.

If Cassidy and Marshburn find definite evidence of the ammonia leak in the pump box, they can replace the box with a spare stored on the truss segment. If no leak is found, they will re-install the original pump control box and return inside the space station, NASA officials have said.

So far, however, the spacewalkers have found no obvious signs of ammonia leaking from the pump control box.

"I can't think of anything to tell you other than nominal," Cassidy said as he described what he was seeing at the pump control box's location.

The two astronauts will also take extra care of their spacesuits while working near the ammonia pump control box. They have brushes and other tools to clean the spacesuits of any toxic ammonia flakes that may stick to them, and can perform a "bake out" to allow any ammonia to evaporate in sunlight, if needed.

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Spacewalking Astronauts Hunt for Space Station Ammonia Leak

After Last-Minute Spacewalk Fix, It's Wait-and-See on Space Station

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A spacewalk outside the International Space Station today (May 11) appeared to fix a leak of liquid ammonia, though astronauts and Mission Control will be in wait-and-see mode until they know for sure if the repairs succeeded.

Two NASA astronauts Chris Cassidy and Tom Marshburn ventured outside the football field-size orbital complex to investigate a leak that had sprung in the station's cooling system, which uses liquid ammonia to transfer heat away from electronic power systems. Although they found no signs of damage that might explain the leak, the spacewalkers replaced a suspect coolant pump, which appeared to halt the flow of ammonia for now.

It will be weeks, or even months, though, before it's clear if the leak has fully stopped. [Emergency Spacewalk to Fix Space Station Leak in Photos]

"The crew looked and watched for any obvious signs of leaks and didn't see anything," Joel Montalbano, deputy space station program manager, said during a press conference after the spacewalk today at NASA's Johnson Space Center in Houston. "We're very happy."

Engineers on the ground will continue to study the troubled area in hopes of understanding what caused the leak.

"We'll see if anything becomes obvious," said NASA flight director Ed Van Cise. "From what we saw during the EVA [extravehicular activity, or spacewalk] itself, nothing really stood out in terms of what may have been the culprit."

NASA officials said they don't yet know if the problem is related to a leak that was spotted in the same coolant channel in 2007. That leak was so slow it posed no immediate problem, and a November 2012 spacewalk that replaced a radiator for the system appeared to stop it.

On Thursday (May 9), the six-man crew of the space station's Expedition 35 mission noticed the leak had worsened, with visible white snowflakes of frozen ammonia floating out into space.

"It was just two days ago that the slight leak we were observing in the thermal control system took a change to where it was a pretty dramatic leak," Van Cise said.

The urgency of the problem caused NASA to "pretty much bring everyone to the table" to address the situation and plan the spacewalk at the last minute, he added. "Space station is a very large, complicated and complex vehicle built all across the world. There are going to be engineers and very smart people all over the place that need to help us address these situations. We draw upon that when we have to and when the vehicle throws something at us that we need all those resources."

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After Last-Minute Spacewalk Fix, It's Wait-and-See on Space Station

International Space Station Ammonia Leak Prompts Spacewalk Preps / NASA / ISS – Video

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International Space Station Ammonia Leak Prompts Spacewalk Preps / NASA / ISS
Aboard the International Space Station a leak of ammonia coolant was detected on May 9, coming from a location on the station #39;s P6 truss. Credit: NASA SPACE ...

By: ThunderAerospace

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International Space Station Ammonia Leak Prompts Spacewalk Preps / NASA / ISS - Video