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Problems With Space Station's Robotic Arm Delay Shuttle Visits
The next two flights of space shuttles to the International Space Station will each be delayed at least three weeks as engineers try to resolve problems with the station's new robotic arm, National Aeronautics and Space Administration officials said today.
The launching of the shuttle Atlantis, which is to attach a specially designed air lock to the station, will be deferred to July 2, at the earliest, from June 20. And the flight of Discovery, which is to take up a new resident crew and supplies for the orbiting outpost, was pushed back to at least Aug. 3 from July 12, officials said.
John Curry, lead flight director for station construction, said at a news conference today at the Johnson Space Center in Houston that the extra time was needed to work to solve problems in the Canadian-built arm, which could require astronauts to replace parts on spacewalks.
Canadarm2, a flexible, 57-foot-long construction crane delivered to the station in April, worked fine when operating with its primary systems of electronics and computers, officials said, but problems have arisen when using backup systems intended to take over if the primary systems failed.
The air lock carried by Atlantis cannot be installed without Canadarm2, making its proper operation critical. A smaller robot arm carried on space shuttles is too short to place the air lock on the Unity node connecting the Russian and United States' parts of the station complex.
Mr. Curry said flight rules required that both primary and backup operating modes of the arm be functioning fully before launching the air lock, a pressurized, two-chamber unit that is to be the primary doorway for spacewalks from the station by astronauts using Russian or American spacesuits.
Aaron Goldenthal, NASA's robotics officer for the station, said the problem appeared to be in an electronics box in the arm's shoulder pitch joint, one of seven joints that allow the flexible crane to reach all areas of the station.
One option engineers are examining is creating computer commands to bypass use of this joint in backup mode to see if the arm can do its job with a different set of movements using the other six joints, he said.
Mr. Goldenthal said the robot arm, critical to all future construction on the station, is designed to have all of its parts replaced when needed. While the shoulder joint can be replaced, no replacement is aboard the station and one would have to be sent from Earth later.
A replacement arm computer unit is aboard the station and project managers will decide Friday whether to ask the station's resident crew to expand a planned June 8 spacewalk to change this unit in the arm.
The station commander, Russian Yuri V. Usachev, and the American flight engineer, James S. Voss, were to do a short walk from the Russian end of the station to reposition a docking device, but that venture could be extended to allow traveling to the American side of the station to work on the arm. NASA officials said it was unclear if replacing the arm's computer unit would help solve its problems.
The shuttle flight delays also would mean that the station crew, which includes Col. Susan B. Helms of the United States Air Force, would have to extend its stay.
The crew, the second to operate the station, arrived in March for a four-month tour and was supposed to return to Earth on July 23 aboard Discovery, which is to carry three replacement astronauts.
Mr. Curry said the crew had been told it would be staying longer, and all members said they were pleased to put in the extra time.
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