CAPE CANAVERAL, Fla. -- Two U.S. astronauts carried out a flawless test of the International Space Station's new robot arm Thursday, reducing fears that start-up problems with the crane might recur on an outpost assembly mission next month.
Working inside the station's U.S. Destiny lab, Susan Helms and Jim Voss put the $600 million arm through a dry run of its first major job: Mounting a $164 million airlock on the frontier outpost.
And while the astronauts encountered some difficulty with a key station camera system, the Canadian-built arm operated without problems during the test.
"There were no failures whatsoever," said NASA station flight director John Curry. "Everything worked perfectly."
That was good news for NASA and 15 other nations involved in the $60 billion station construction project, which has been on hold in recent weeks while engineers sorted out fleeting problems with the construction crane.
Delivered to the station in April, the 57.7-foot (15.5-meter) robot arm must be working properly to install the 6.5-ton airlock, which will serve as a staging area for spacewalking sorties to be carried out at the complex.
Shorter shuttle robot arms are not long enough to hoist the airlock into position on the starboard side of the station's U.S. Unity Module, which is located toward the upper reaches of the 17-story outpost.And in recent weeks, project managers have been concerned that the arm's shoulder joint might fail during the upcoming mission, stranding the airlock at the end of the crane while astronauts are attempting to install it.
Problems with the shoulder joint first cropped up in late May, raising the possibility that the arm would automatically shut itself down during the airlock installation job. Engineers since have traced the problems to a computer chip associated with an electronics unit that enables the shoulder joint to be maneuvered.
NASA robotic systems engineer Skip Hatfield said a simple software patch would be beamed up to the station next week, enabling the arm to carry out the construction job even if the shoulder joint problem recurs during the installation of the airlock.
Consequently, Curry said that station project managers are "highly confident" that the arm will work as intended when astronauts aboard shuttle Atlantis haul the airlock up to the station after a planned July 12 launch from Kennedy Space Center.
The successful dry run was the second in as many weeks, and while the arm worked as advertised, Helms and Voss ran into difficulties with a television camera system that will play a crucial role in the airlock installation work.
With no way to directly eyeball the job at hand, the astronauts will be relying on camera views from the television system to install the airlock. Both Helms and Voss, however, have had trouble getting the proper camera views to appear on TV monitors during the dry run tests.
The problem in this case lies within the ability to route the proper video signal to the TV monitors connected to robot arm computer control stations within the Destiny lab.
"It turns out that our video system is a little bit complicated," Curry said, likening the situation to the type of problems people have when trying to hook up TVs, VCRs and direct broadcast satellite receivers.
"That's what we've got here," he said. "You need to route these video signals through the various boxes on the space station to get them to output" on outpost monitors.
Curry, however, said ground controllers and the station crew are confident that the trouble can be sorted out prior to the upcoming construction mission.
Atlantis, meanwhile, rolled out to launch pad 39B here at Kennedy Space Center Thursday as the station crew was carrying out the robot arm test. Now housed in an environmentally controlled payload room at the pad, the airlock is to be loaded into the shuttle's cargo bay next week.
A three-day countdown to the Atlantis launch is scheduled to pick up July 9, and an on-time liftoff would lead to a July 23 landing here at NASA's coastal Florida spaceport.
Shuttle Discovery remains scheduled for launch Aug. 5 on a mission to ferry a new crew to the station and then return to Earth with Helms, Voss and outpost commander Yuri Usachev. Curry said that launch, however, could slip back a few days if there are any minor delays in getting the Atlantis flight airborne.
Now undergoing tests in KSC's 52-story Vehicle Assembly Building, Discovery is tentatively scheduled to roll out to launch pad 39A next Wednesday. An Aug. 5 launch would lead to an Aug. 23 return to terra firma for Helms, Voss and Usachev, capping a 162-day stay in space.
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