Spacewalkers Suit Up For Tranquility Delivery

Two American astronauts are preparing to head outside the International Space Station tonight for a spacewalk aimed at delivering a final large section for the U.S. side of the orbital outpost.

Endeavour mission specialists Bob Behnken and Nicholas Patrick are slated to exit the station's U.S Quest airlock around 9:09 p.m. and then prep the newly arrived Tranquility module for a lift out of the shuttle's cargo bay. They'll also act as spacewalking spotters while crane operators Terry Virts and Kay Hire put Tranquility in place, and then they'll route power and data cables to link it with the U.S. Unity module and rest of the station.

Sounds simple enough. But the job requires some intelligence.

"Even though they went to, you know, MIT and Cal Tech, they are still really smart guys," joked crewmate Steve Robinson, who got his masters and doctoral degrees in engineering at Stanford University.

And spacewalking work requires sound bodies, too.

"It's kind of like going to the gym all day while you are at the same time in a chess tournament," said Robinson, a veteran spacewalker who will direct tonight's spacewalk from inside the joined shuttle-station complex.

"It's a very, very challenging mental exercise to plan ahead every second, and these guys are the best you're going to see. They're very awesome at that."

The first order of business tonight:

Crawling hand-over-hand from the airlock to the shuttle's cargo bay -- or about the length of a football field.

Once there, the spacewalkers will disconnect power lines that have kept the cylindrical module warm since it was launched from Kennedy Space Center on Monday.

That move will start a thermal clock ticking. Failure to finish installing Tranquility within the next 24 hours might irreparably damage the module and its attached Italian observation deck. Total cost: $400 million.

NASA Lead Shuttle Flight Director Kwatsi Alibaruho calls it "a fairly complicated process."

So much so that he gave the Endeavour crew a half-day off Wednesday to prepare for the spacewalk and two other excursions that will follow within five days.

Alibaruho wanted to "go ahead and give them some off duty time on the front end (of the mission) so they'll be well-rested to start a period of really heavy activity."

The second and third spacewalks required to finish the Tranquility installation are scheduled for Saturday and next Tuesday.

Endeavour's astronauts are scheduled to depart the station Feb. 18 and land at KSC on Feb. 20.

Mission managers are thinking about extending the shuttle's stay at the station by a day to increase the amount of Tranquility outfitting that can be accomplished. In that case, landing would be set for Feb. 21.

ABOUT THE IMAGE: Click to enlarge the NASA TV screen grab of International Space Station Commander Jeffrey Williams helpping Endeavour lead spacewalker Bob Behnken sit up for the first of three spacewalks planned during Endeavour's stay at the outpost.