HOUSTON - NASA revealed unprecedented spacewalking
plans today that could mend a maimed solar wing at a far end of the
International Space Station (ISS) on Saturday.
The space
agency said astronauts will attempt to repair the working power-generating solar
array, which partially tore at its hinges during deployment on Oct. 30. Mission managers indicated most details are set for the spacewalk, but gave themselves a
1:08 a.m. ET (0508 GMT) deadline early Friday to ship complete instructions up to astronauts.
"We're
faced with a difficult situation," said David Wolf, head of the EVA branch for the
astronaut office, here at Johnson Space Center. "I think we're onto a solution that should work
and get us pretty close to a permanently acceptable situation."
The
extravehicular activity, or EVA, will send STS-120
astronaut Scott Parazynski on a one-hour ride on an extended robotic arm to
the damage site while fellow astronaut Doug Wheelock looks on. Donning
protective goggles, astronauts in space worked today to craft "cuff
links" that should button up the 2.5-foot (0.76-meter) tear in the array.
If
Parazynski does not effect a repair from his 90-foot-long (27-meter-long) robotic
ride, mission managers said spacewalkers could try again on a following day.
Derek
Hassmann, ISS lead flight director for the STS-120 mission, said teams are
still working around the clock to get the complete details together for the
fourth spacewalk. Management teams delayed
the EVA to Saturday to buy more time.
"We
knew it would be a full-court press to get there on Friday, and I'm disappointed
that we didn't get there," Hassmann said. "But I'm satisfied we made a good
call."
Tricky
choreography
Engineers
who scrutinized solar array photographs think a piano-wire-like guide line caught
on a hinge of the 4B solar array, unzipping it along the way. The solar wing
was deployed about 80 percent before astronauts on board the space station
aborted the operation.
Lead
STS-120 spacewalk officer Dina Contella said two tears--one large and one
small--might be somehow related to the cable.
"We
know that there's a snag there, but we're not sure ... if it's something really
easy to clear," Contella said, noting that Parazynski will be toting a
pack of tools to work with.
Whatever
the case, Parazynski will get an up-close-and-personal look at the damage—at
which time flight controllers will huddle to decide what steps to take next.
"When
Scott is out there with his helmet cameras right at the repair (site), that
will be our first really close look at this problem," Wolf said. "we're
going to have to as a team ... quickly develop a plan of action."
Shocking
danger?
Hassmann
said the EVA carries a risk of electric shock via the 110 volts coursing through
one part of the solar wing, which generates about 13.4 horsepower (that of medium-sized
backup generator).
"Once
[solar arrays] are deployed, they start producing power as they're designed to
do," Hassmann said of the 110-foot (33.5-meter) sail of solar cells.
"There's nothing we can safe or turn off the array while it's
deployed."
But mission
managers noted that any extra risks they may place Parazynski under during the
6.5-hour EVA will be under control.
"Our
job is to think of all those possible ways where a bad outcome could occur ... and
be sure that every hazard is mitigated and handled," Wolf said. "We
can come up with hazards, including electrocution--and thus we are sure that we
have mitigated that hazard within any reasonable means."
The STS-120
space station construction mission launched with the space shuttle Discovery on
Oct. 23 and is slated to depart the space station on Nov. 5 for a Nov. 7 daylight landing. There are enough supplies on board the spacecraft to extend
the already
extended mission by another two days, if necessary.
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