CAPE CANAVERAL, Fla. – Small amounts of toxic ammonia leaked from a fluid line Sunday as two astronauts conducted the second of what could be a precedent-setting three spacewalks in nine days, upgrading the international space station's cooling system.
The liquid ammonia, which freezes into flakes when it hits the vacuum of space, did not appear to touch Michael Lopez-Alegria or Sunita Williams. Mission Control told them to continue their task of hooking up ammonia fluid lines from a temporary cooling system to a permanent one.
The astronauts looked over their spacesuits, gloves and helmets and found no ammonia residue.
"I think we're happy with what we see," Lopez-Alegria said.
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Mission Control told the astronauts that exposing their spacesuits to sunlight would "bake off" any ammonia residue that may have gotten on them. The astronauts experience a sunrise every 1 1/2 hours.
A tiny bit of ammonia also leaked during Lopez-Alegria's and Williams' first spacewalk Wednesday, but did not touch them. Nevertheless, Mission Control ordered them to take precautions since ammonia could cause respiratory problems for the three-person crew if enough of it got into the space station.
"They look like pinpoints," Lopez-Alegria said of the flakes Sunday. "They don't look like what we saw the other day, but they are coming out with some velocity."
Ammonia also leaked during a similar spacewalk by astronaut Robert Curbeam in 2001.
Lopez-Alegria and Williams successfully completed tasks almost identical to ones they did during the spacewalk Wednesday. Sunday's chores included hooking up the permanent cooling system, covering an obsolete radiator that was retracted by remote control from the ground and stowing a fluid line that was connected to an ammonia reservoir.
They then moved on to other jobs ahead of schedule: removing a sun shade, photographing a solar array that will be retracted during space shuttle Atlantis' mission next month and making electrical connections for a new system that will allow power from the station to be shared with a docked shuttle.
Engineers hope the digital photos will help them with next month's plans since flight controllers and spacewalking astronauts had difficulty retracting a similar solar array during the shuttle Discovery's visit to the space station in December. The extra power for the shuttles will allow them to stay docked for longer periods.
The third spacewalk is set for Thursday, marking the first time three spacewalks will have been conducted in such a short time at the space station without a space shuttle docked to it. Lopez-Alegria planned to conduct a fourth spacewalk with Russian flight engineer Mikhail Tyurin on Feb. 22.
If the schedule stays in place, both U.S. astronauts would hold spacewalking records by the end of the month. Williams will hold the record for the most by a woman, and Lopez-Alegria will be the U.S. champion, surpassed only by Russian cosmonaut Anatoly Solovyov for the all-time record.
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