Two
Russian cosmonauts will inspect and remove an explosive bolt from the Russian
Soyuz spacecraft during a Thursday spacewalk outside the International Space
Station.
The
spacewalk is slated to begin at 2:20 p.m. EDT (1820 GMT) as part of the ongoing
Russian investigation into a malfunction that sent the two previous Soyuz
spacecraft off-course
during reentry. NASA officials have kept
close watch on the proceedings.
"To
date they haven't come to a conclusive answer as to what was the cause," said Mike
Suffredini, program manager for the space station, at a Tuesday briefing. "They
continue to look at different scenarios."
Ten
explosive pyro bolts fire to help separate the Soyuz spacecraft from its
propulsion module. The maneuver normally allows the Soyuz to turn its
protective heat shield downward before reentry, but Russian engineers suspect
that a failed explosive bolt caused the Soyuz modules to separate late during
the most recent descent on April 19 this year.
The
delayed separation subjected the latest Soyuz crew — including cosmonaut
commander Yuri Malenchenko, U.S. astronaut and Expedition 16 commander Peggy
Whitson and South Korea's first astronaut So-yeon Yi — to a bumpy ballistic
reentry with higher than normal gravitational loads. Yi described the frightening
experience in detail and later underwent hospital
treatment for neck and back pain.
6
hours in space
Space
station commander Sergei Volkov and flight engineer Oleg Kononenko will
undertake the nearly six-hour spacewalk, with Volkov wearing a red-striped
Orlan spacesuit and Kononenko wearing a blue-striped spacesuit. Kononenko's
spacesuit helmet will also carry cameras normally worn on U.S. spacesuits.
That
leaves U.S. astronaut Greg Chamitoff, the third member of the space station
crew, to sit inside the Soyuz during the spacewalk. The Pirs airlock that the
crew might normally use to evacuate will be used for the spacewalk, so ground
controllers want Chamitoff in the Soyuz in case of the unlikely event that the
airlock could not be re-pressurized.
The
cosmonauts will ride the Strela hand-powered crane to the Soyuz and put
protective covers on the nearby thrusters to prevent accidental contamination
from debris.
Knonenko
will use a knife for the first time during a spacewalk to cut away insulation,
which then would allow him to inspect and photograph the area. He will also
install a handrail and cover to protect fluid lines.
The
knife was described as "serrated with a dull tip" by Bob Dempsey, spacewalk
flight director for the space station.
Volkov
will then cut a wire tie between two explosive bolts next to the suspect bolt,
and detach an electrical connector before unscrewing the bolt. He will remove
the explosive bolt — which has power roughly equivalent to a large M-80
firecracker — and place it inside a stainless steel case that should hold
against any unlikely firing of the bolt.
"We
are very confident that this is a safe operation to do," Dempsey said.
Suffredini
noted that accidental firings of the pyro bolts are unheard of during the Soyuz
spacecraft's operational history. Russian engineers want to examine the bolt
once it returns to Earth for any possible signs of space environment damage
from electromagnetic or plasma forces surrounding the space station.
Building
boom
NASA
officials also dismissed any coincidence between the malfunctions and the
recently accelerated production of Soyuz spacecraft. The Russians have begun
building more spacecraft to support the jump in the space station's population
next year, from three astronauts to a six-person crew.
The
Soyuz will also serve as the only spacecraft capable of ferrying people to and
from the space station when the space
shuttle retires in 2010, until NASA's Orion
spacecraft comes online in 2014.
"We
have a good deal of confidence in their ability to produce those things,"
Suffredini said.
If
the cosmonauts have time at the end, they will also install a docking target on
the Zvezda service module to prepare for a Russian mini-research module's
arrival on a future mission.
A
second spacewalk is scheduled for July 15, when Volkov and Kononenko will need
to outfit the Russian segment's exterior, install a scientific experiment and
retrieve another.
NASA will
broadcast the Expedition 17 crew's spacewalk live on NASA TV beginning at 2:20 p.m.
EST (1820 GMT) on July 10. Click here
for SPACE.com's
live coverage and mission updates.
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