HOUSTON -- NASA mission managers are
weighing plans to address a stubborn
solar array left half-exposed above the International Space
Station (ISS), and lauded a successful
Thursday spacewalk to rewire the orbital laboratory.
ISS flight controllers plan to
conduct a "wiggle" test on one of two solar wings of the station's mast-like
Port 6 (P6) truss by 11:00 a.m. EST (1600 GMT) today to jar a sticky
guide wire loose, said John Curry, NASA's lead ISS flight director for the STS-116
shuttle mission aboard Discovery.
"We suspect that with some minor
excitation of the arrays, these will clear themselves," Mike Suffredini, ISS program manager for NASA, told reporters
here at the Johnson
Space Center.
The P6 array, which stretches out
over the space station's port side, has been idle
in mid-retraction since Wednesday, when initial efforts by Discovery and
ISS astronauts to pack it away remotely were stymied by incorrect folds [image].
Friction between the array's guide wires as they thread through a series of
grommets appears to be the culprit, and if the wiggle test doesn't do the
trick, mission managers will meet and discuss whether to try a second
technique, flight controllers said [image].
"There's actually another technique
that will make you laugh a little," Suffredini said.
That technique basically calls for
an astronaut, possibly one of the
space station's Expedition
14 crewmembers, to go through a vigorous aerobic workout using the
outpost's Interim Resistive Exercise Device (IRED), Suffredini
explained. An intense workout of lifts and squats on the bungee-bar device by NASA
astronaut Leroy Chiao during the station's Expedition
10 mission caused vibrations that visibly shook the P6 solar arrays in the
past, he added [image].
"It turned out he was doing more of
a workout than just on himself," Suffredini
said of Chiao. "He was working out the arrays as
well."
ISS flight controllers hope either
of the two non-spacewalk approaches will be successful since mounting a fourth
spacewalk during Discovery's STS-116 mission not only carries time
pressures, but also shock hazards along with the inherent
risk of leaving a spacecraft for orbital work. The space station's Expedition
14 mission also has a packed spacewalk schedule, mission managers said.
"I think we'll clear this with [intravehiclar] steps," Suffredini
said, adding that if one of the two internal approaches is successful today the
P6 array could be retracted later this afternoon. "No matter what we do, the
array will always be structurally sound."
While it need not be retracted
completely during the STS-116
mission, the solar wing and another on the P6 truss must be packed away
before the segment can be relocated to the end of the recently
installed Port 5 truss later next year, and may have to be addressed before
a Russian spacecraft docks at an Earth-facing berth in April.
If a spacewalk is required, flight
controllers believe a simple tug on the stuck guide wire is enough to free
snags, but are still debating whether to use the station's robotic
arm or foot restraints to hold a spacewalker in place. To squeeze in a
fourth spacewalk for Discovery's STS-116 crew by Flight Day 9 of their mission,
ISS managers would have to make the decision by the end of today. A Flight Day
10 spacewalk plan could give managers an extra day to decide, Suffredini said.
Discovery astronauts concluded
Flight Day 6 of their 12-day mission when they went to sleep at 1:47 a.m. EST
(0447 GMT) today.
Spacewalk success
In addition to discussing the space
station's stubborn solar array, ISS flight controller lauded the near-perfect
Thursday spacewalk by STS-116 astronauts Robert
Curbeam and Christer Fuglesang.
The astronauts spent five hours
rewiring half of the space station's power system to shift from a temporary
arrangement to its permanent form and also activated the orbital laboratory's
primary cooling system for the first time.
"Today went as close to without a
hitch as you can possibly have a spacewalk can go," Curry said Thursday,
admitting that the sheer amount of tools, equipment and machinery that had to
work as advertised was daunting. "And all that stuff worked exactly and
precisely the way folks designed it...the crew, both of them, they were just
machines."
The spacewalk's
success bolsters hopes that a similar plan to rewire the remaining half of the
ISS power grid on Saturday will go as planned, NASA officials said.
Saturday's spacewalk, the third and
final excursion currently planned for the STS-116 crew, is scheduled to begin
at 2:37 p.m. EST (1537 GMT). Curbeam and newly
arrived ISS flight engineer Sunita Williams, who is replacing European Space Agency
astronaut Thomas
Reiter during Discovery's docked mission, will perform the planned six-hour
spacewalk.
The joint ISS and Discovery shuttle
crews have a rather light day ahead of them Friday. They are scheduled to
perform a series of cargo transfers and speak with reporters on Earth
throughout the day, with some time reserved for personal time, NASA officials
said.
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