CAPE CANAVERAL, Fla. -- The $60 billion International Space Station construction project is scheduled to resume high above Earth this week as astronauts set out to equip the outpost with an orbital doorway that will double as a locker room for spacewalkers.
With a recent spate of station computer and robot arm troubles now under control, crane operators aboard the outpost and shuttle Atlantis will join forces with two spacewalkers to mount a $164 million airlock near the top of the 17-story complex.
And once the chamber is put in place, station crews no longer will have to rely so heavily on visiting shuttle astronauts to carry out 145 spacewalks still required to finish raising and maintaining the complex over the next five years.
"The big thing is that you won't be tied to having the shuttle attached to the space station to do those spacewalks," said Robert Cabana, NASA's deputy manager of international station operations. "We'll have a self-sufficient capability onboard the space station."
Now nestled in the cargo bay of Atlantis, the so-called Joint Airlock is scheduled for launch from Kennedy Space Center at 5:04 a.m. EDT (0904 GMT) Thursday along with a crew of five shuttle astronauts.
The station's new $600 million Canadian robot arm will be used to move the airlock up to the starboard side of the U.S. Unity Module, where it will serve as a staging area for future spacewalks to be conducted outside the outpost.The shuttle's shorter robot arm will serve as a cherry picker, hoisting the spacewalkers up to that site so they can attach the airlock to a berthing port. Four high-pressure oxygen and nitrogen tanks needed to replenish air supplies within the chamber then will be latched to the airlock's aluminum shell.
The weeklong assembly operation - which calls for three spacewalking sorties -- will mark the first time two robot arms have been used in concert to carry out a station construction job.
And since the cranes at times will swing within inches of each other, the work will require a high degree of choreography between the Atlantis quintet and the station's three resident tenants.
"That's going to be one of the more complicated parts of this whole operation -- the joint operation of both arms," said Atlantis spacewalker Michael Gernhardt.
"There's always a concern about making sure that the arms don't collide at any point," added shuttle pilot Charles Hobaugh.
Less a concern are recent problems with the station's command-and-control computers and its new robot arm.
The computers crashed in April, hampering station operations, but since have been outfitted with new hard drives and are working as advertised.
Start-up troubles with the shoulder joint of the arm also have been overcome in recent weeks, largely negating the fear that a failure might leave the airlock stranded at the end of the 57.7-foot (17.5-meter) station crane.
"We have high confidence that we can get the airlock installed," said NASA flight director Paul Hill, who will oversee the assembly work from the agency's Mission Control Center in Houston.
Added station flight engineer Susan Helms: "We can't think of a single thing that's holding us back, and we're very excited about the (shuttle) crew coming up here with the airlock and the gas tanks and working with us."
Weighing in at 6.5 tons, the airlock will give station tenants an unprecedented level of independence and flexibility, enabling them to carry out spacewalking work in either U.S. or Russian spacesuits at times when a visiting shuttle isn't docked to the outpost.
Twenty of 21 spacewalks performed at the station to date have been staged from shuttle airlocks. The other took place within a spherical section of the station's Russian-built crew quarters, which can be converted into a makeshift airlock.
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