Spacewalkers Overhaul Part of ISS Cooling System

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  Space News Business

Spacewalkers Overhaul Part of ISS Cooling System

By TARIQ MALIK
Space News Staff Writer
posted: 08 February 2007
10:59 am ET



NEW YORK – Two NASA astronauts kicked off the first of four tightly packed spacewalks outside the international space station (ISS) Jan. 31 by carefully overhauling part of the orbital laboratory’s cooling system despite the last-minute find of a few toxic ammonia flakes.

 

During a spacewalk that lasted nearly eight hours, 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.

 

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.

 

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,” said 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 planned over a nine-day period. 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.

 

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.

 

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 during 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. NASA commentator Rob Navias likened the activity to working on your car engine while clad in a snowsuit and gloved hands.

 

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.

 

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.