Spacewalker Nicole Stott works inside the payload bay of shuttle Discovery during a spacewalk outside the International Space Station, the first for the STS-128 mission, on Sept. 1, 2009.
Credit: NASA TV
Two spacewalkers carefully removed a massive tank from its mooring outside the International Space Station late Tuesday as their crewmates unpacked a treadmill named after comedian Stephen Colbert.
Astronauts Danny Olivas and Nicole Stott spent 6 1/2 hours working outside the station to unhook an old ammonia coolant tank and retrieve experiments from the orbiting laboratory?s hull.
The spacewalkers took special care because of the sheer size of the ammonia tank, which will be replaced with a new one on Thursday. The old tank has been at the station since 2002 and will return home aboard Discovery for an overhaul on Earth.
The tanks are some of the most massive pieces of gear to be handled by spacewalkers and weigh about 1,800 pounds (816 kg) when full, making them bulky - if weightless - loads to haul in space.
The one wrangled by Stott and Olivas was nearly empty of toxic ammonia, but still massive at about 1,300 pounds (589 kg). It?s almost 5 feet long, 7 feet wide and 4 feet tall (1.5 m by 2.1 m by 1.2 m), so they were careful to keep it under control until it could be grappled by the station?s robotic arm.
Olivas and Stott also retrieved a European technology experiment from the end of the station?s Columbus laboratory, as well as a materials exposure experiment that folds up like a briefcase to be returned to scientists on Earth. Stubborn bolts and pins made the job a bit harder, but the astronauts - and some extra elbow grease - won out in the end.
?Good job,? Olivas told Stott. ?A good day?s work.?
Tuesday?s spacewalk was not without its hiccups.
About 1 1/2 hours into the excursion Olivas spotted some fraying on the index finger of his spacesuit?s right glove, but Mission Control said the defect posed no risk for the astronaut and the spacewalk was allowed to go on.
Soon after, a sensor in Stott?s spacesuit inexplicably signaled high levels of carbon dioxide in her spacesuit, but she told Mission Control she felt fine. Mission Control said the sensor appeared to be giving a false reading.
Then a severe storm over a relay station in Guam cut off communications between Mission Control and spacewalkers, as well as the space station and shuttle, for just over a half hour.
?You?re going to be on your own,? Mission Control told the astronauts.
Astronaut Patrick Forrester, who choreographed the spacewalk from inside Discovery, said they?d do what they could. The spacewalkers took photographs while waiting out Earth?s silence.
COLBERT boards space station
While the spacewalkers worked outside, the 11 astronauts inside the station moved the new $5 million treadmill named after comedian Stephen Colbert - of the Comedy Central?s ?Colbert Report? - into a storage spot aboard the orbiting lab.
Colbert, with the help of his fans, won the naming rights for a new space station room during an online NASA poll earlier this year. But NASA opted to the name the room, which launches to the station next year, Tranquility to honor of the Apollo 11 moon landing 40 years ago last month.
As a consolation prize, NASA dubbed the station?s new treadmill the Combined Operational Load Bearing External Resistance Treadmill, or COLBERT. It arrived at the station in more than 100 pieces and packed in several bags.
Stott, who joined the station?s crew after arriving Sunday on Discovery, and her crewmates will assemble the treadmill in mid-September. NASA officials said it should take 20 hours to complete, so the astronauts will wait until after Discovery's departure and the arrival of an unmanned Japanese cargo ship next month to build it.
Even in pieces, the treadmill is apparently already trying to steal the limelight. It banged a video camera on its way into the space station.
?Looks like COLBERT may have dislodged the camera on his way through,? Mission Control radioed the astronauts, one of whom quickly moved the camera back into place.
In addition to the treadmill, astronauts also moved a new astronaut bedroom and air-scrubbing equipment into the space station.
Tuesday?s spacewalk was the first for Stott. Her family watched her 6-hour, 35-minute walk in space from Mission Control in Houston.
It was the third career spacewalk for Olivas, who is leading the three spacewalks planned for Discovery?s 13-day mission. He ended the day with 20 hours and 48 minutes. The spacewalk was the 131st dedicated to space station construction or maintenance.
More unpacking is on tap for station and shuttle astronauts on Wednesday. They plan to unload a pair of sophisticated new experiment racks to study fluid physics and new materials in weightlessness. The next spacewalk is set for Thursday.
- New Video - STS-128 Spacewalk Overview
- New Video - Meet the STS-128 Shuttle Astronauts
- Video - Stephen Colbert to NASA: 'No Chubby Astronauts'
SPACE.com is providing complete coverage of Discovery's STS-128 mission to the International Space Station with Managing Editor Tariq Malik and Staff Writer Clara Moskowitz in New York. Click here for shuttle mission updates and a link to NASA TV.