Spacewalkers Overhaul Part of ISS Cooling System
Expedition 14 spacewalkers Sunita Williams (left) and Michael Lopez-Alegria disconnect a series of flex hoses and fluid lines from an unneeded ISS ammonia coolant reservoir during their Jan. 31, 2007 excursion.
Credit: NASA TV.

WASHINGTON -- Two NASA astronauts kicked off the first of four tightly-packed spacewalks outside the International Space Station (ISS) Wednesday by carefully overhauling part of the orbital laboratory's cooling system despite the last-minute find of a few toxic ammonia flakes.

ISS Expedition 14 commander Michael Lopez-Alegria and flight engineer Sunita Williams successfully switched four liquid ammonia coolant lines from a temporary set up to their permanent configuration during almost eight hours of spacewalking work high above the Earth [image].

The work was slow and demanding, but paid off as Lopez-Alegria and Williams activating the new cooling loop near the midpoint of the seven-hour, 55-minute spacewalk [video].

The only hint of leaking ammonia occurred near the end of the spacewalk, when Williams reported about four small "flakes" of frozen, yet toxic, ammonia drifting out of a fluid line cap during a completely different task.

"Whoa," Williams said, adding that the coolant did not appear to contaminate her Lopez-Alegria's spacesuit. "I am pretty positive that it didn't get in any contact with his spacesuit."

Ammonia contamination has been a concern since 2001, when a cloud of frozen ammonia flakes bloomed around NASA astronaut Robert Curbeam as he too handled ISS cooling system lines.

"At very low levels it could be an irritant," Derek Hassman, NASA's lead Expedition 14 flight director in a post-spacewalk briefing, of ammonia coolant, adding that higher levels could have more serious effects. "It can have a significant impact on the crew's respiratory function."

But unlike the 2001 incident, where contamination was known and required extreme cleanup measures, today's ammonia sighting fell under "suspected contamination" and called for only minor preventative steps, NASA officials said, adding that all tests were negative for ammonia contamination.

"We didn't introduce any ammonia into the airlock or into the habitable region of the space station," Hassman said.

Lopez-Alegria later described the flakes as rectangular and narrow, adding that a bit of plastic he saw earlier in the cooling line work may indeed have been bit of frozen ammonia.

The spacewalk, Lopez-Alegria's seventh career extravehicular activity (EVA), marked the first of an unprecedented three excursions in nine days (and four overall in the coming month) for an ISS crew. It is the most densely packed series of spacewalks to date for space station astronauts outside of a visiting space shuttle mission.

The EVA marked Williams' second career spacewalk.

Wrangling cooling lines

The spacewalk began at 10:14 a.m. EST (1514 GMT) as the ISS passed 220 miles (354 kilometers) over the South Atlantic. Expedition 14 flight engineer Mikhail Tyurin, who remained inside the ISS during the spacewalk, helped his crewmates don and doff their spacesuits and watched over the station's systems [image].

"Beautiful," said Lopez-Alegria as he and Williams began their spacewalk. "Looks like just a little bit of a circular storm down there."

During their cooling system overhaul, Lopez-Alegria and Williams rerouted ammonia cooling lines from their temporary track through the space station's mast-like Port 6 truss into a final setup that runs through a series of heat exchangers in the outpost's U.S. Destiny laboratory [image].

"It was worth it taking our time," Lopez-Alegria said. "We ran into a few things, but it's all good."

The work is vital to prepare the station's power and cooling systems to handle future international laboratories. It also helps to ready the station's Port 6 truss for its relocation to the edge of the orbital lab's port truss segment in a September shuttle mission.

The astronauts primarily handled the station's Loop A cooling lines, which transport heat away from the Destiny module's environmental control systems and experiment hardware. But it was hard work, especially on the astronauts' hands. NASA commentator Rob Navias likened the activity to working on your car engine while clad in a snowsuit and gloved hands.

"My hands are toast," Lopez-Alegria said near the spacewalk's end.

The station's Loop B cooling system, which oversees station payloads and flight avionics, will be reconfigured in a mirror image of today's spacewalk set for Feb. 4.

In addition to their cooling system work outside the ISS, the Expedition 14 astronauts also primed a pair of cables to help transfer power between the ISS and NASA shuttles during future missions. They also secured a defunct ISS radiator -- no longer needed after today's cooling system overhaul -- and stripped one of two fluid lines from an unneeded ammonia coolant reservoir [image].

Lopez-Alegria and Williams ultimately ran out of time and were unable to complete a laundry list of extra chores set aside for them, but they or future spacewalkers will have the opportunity.

Glenda Laws, NASA's lead Expedition 14 spacewalk officer, said the extra tasks -- known as get aheads -- could be added to one or both of the next ISS spacewalks, but completing the cooling system overhaul remains a priority.

Wednesday's spacewalk marked the 78th EVA dedicated to ISS assembly, the 50th staged from the orbital laboratory itself, and the 30th to begin at the outpost's U.S. Quest airlock.

The spacewalk also pushed Lopez-Alegria to the rank of fourth all-time spacewalker (up from 13th), with a total EVA time of 47 hours and 31 minutes. Williams, for her part, is now the second all-time female spacewalker with 15 hours and 26 minutes.

The second of the upcoming four Expedition 14 spacewalks is scheduled begin at 8:30 am. EST (1330 GMT) on Sunday, Feb. 4, and will be broadcast live on NASA TV.