June 1, 2006

International Space Station crew starts spacewalk

By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - The two astronauts
aboard the International Space Station ventured out of the
orbital complex on Thursday to begin a spacewalk aimed at
conducting nearly six hours of repairs and maintenance.

In the first of two spacewalks planned during their
six-month stay in space, station commander Pavel Vinogradov and
flight engineer Jeffrey Williams planned to set up a new vent
for a balky Russian oxygen generator, replace a camera needed
for future station assembly tasks and retrieve a science
experiment for return to Earth.

Before a spacewalk, astronauts must breathe pure oxygen to
purge nitrogen from their bloodstreams. The nitrogen can cause
a dangerous condition known as "the bends," which commonly
afflicts divers who surface from deep water too quickly.

Vinogradov, who was making his sixth spacewalk, and
Williams, who has made one previous spacewalk, spent more than
two weeks collecting equipment and practicing procedures for
their outing. They had to resort to two backup plans when a
foot restraint needed to anchor Vinogradov to a work boom and
the original packaging for the science experiment could not be

"It's a lot like your house," said Paul Boehm, who oversaw
the development of the spacewalk for NASA. "You set your car
keys down somewhere and hopefully you find them when you're
ready to go somewhere."

The U.S. space agency tries to keep track of the thousands
of items aboard the station with a computerized bar-code
system. But sometimes crew members move things and do not put
them back in the same place, said Kirk Shireman, deputy manager
of the space station program.

"I suspect we'll find both these items," Shireman said
during a briefing before the spacewalk.

Substituting a U.S.-made tether for the missing foot
restraint, Vinogradov was to begin the spacewalk by setting up
a telescoping boom on the Russian segment used to move
spacewalkers and equipment to various worksites around the

Williams was to drive his commander to the Zvezda service
module so he could open a cap and set up a new hydrogen vent
port for the Elektron oxygen generator.

The device, which produces oxygen by separating hydrogen
and oxygen from water, has been sharing a vent since its
original one became contaminated.

Powering off the machine so that another device can use the
vent has been causing problems, however. The new vent should
allow the Elektron to operate continuously, Shireman said.