First Spacewalk from ISS May Include Robot Arm Repair Work

 By Todd Halvorson
 Cape Canaveral
 Bureau Chief
 posted: 04:00 pm ET
 25 May 2001

 CAPE CANAVERAL, Fla. -- A U.S. astronaut and a Russian cosmonaut might
 swap out a balky electronics box on the International Space Station's new
 $600 million robot arm next month during what will be the first spacewalk
 ever staged from within the outpost.

 Station commander Yuri Usachev and flight engineer Jim Voss already plan
 to don spacesuits on June 8 and move a cone-like docking device that will
 be used to latch a new Russian docking compartment to the outpost when it
 arrives at the station in August or September.

 The job will take place inside a spherical section at the end of the
 station's Russian-built crew quarters, which will be depressurized for
 what is known as an "internal spacewalk."

 "Even though they're in vacuum, they're never really outside the
 spacecraft," NASA space station flight director Robert Castle said
 Friday.

 And any time an astronaut or cosmonaut is in a vacuum in a space suit,
 Russian space officials consider the activity a spacewalk.

 Usachev and Voss, however, still may end up working outside the station.

 The reason: An electronics box located near the elbow of the station's
 new Canadian-built robot arm has been acting erratically in recent weeks,
 and station project managers might have the spacewalking pair replace it.

 That would involve exiting a hatch on the bottom side of the sphere-like
 end section of the crew quarters and then moving across the outside of a
 Russian space tug and a U.S. docking module in order to get to the
 57-foot (17-meter) arm.

 The balky electronics box then would be replaced with a spare before
 Usachev and Voss returned to the confines of the station.

 The so-called Arm Controller Unit is a device that routes computer
 commands from work stations inside the U.S. Destiny lab to the new
 construction crane.

 The unit has two so-called "strings," or pathways, over which computer
 commands can travel. But the back-up string failed to work properly
 during two recent tests, nixing the arm's ability to move its wrist
 during one test and its shoulder joint during the other.

 Engineers think a software glitch is the likely culprit, and if the
 problem can be fixed during the next two weeks, tentative plans to send
 Usachev and Voss outside the station to replace the Arm Controller Unit
 will be scrapped.

 That's not to say, however, that maintenance work outside the station
 won't become commonplace between now and the time station construction is
 completed in mid-2006.

 Visiting shuttle crews already have performed 124 hours of spacewalking
 construction work at the station, and as stands, 1,261 additional hours
 of assembly work will be required to finish the station over the next
 five years.

 But during that same time, NASA officials estimate that astronauts and
 cosmonauts will spend another 344 hours doing spacewalking maintenance
 work outside the outpost.

 "This is like any other technological project," said Castle. "Things are
 going to break. We are going to have to replace things. We are going to
 have to have spare parts and then install those spares."

 The internal spacewalk, meanwhile, originally was to be conducted by the
 first resident crew of the international station. It was put off,
 however, when the planned February launch of the Russian Docking
 Compartment was delayed.

 The cone-like device to be moved originally served as the receiving end
 of a drogue-and-probe docking device used to link the Russian Zvezda crew
 quarters to the station's Zarya space tug. Ultimately, it will be used to
 dock a Russian-made Science Power Platform to the station.

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