HOUSTON -- Astronauts aboard the International Space
Station (ISS) partially tucked away one of the orbital laboratory's solar
wings Wednesday and started up a power-producing paddlewheel on the outpost's
port side.
After more
than 40 attempts and six hours of work to stow a six-year-old solar array on
the station's mast-like Port
6 (P6) truss, the joint ISS and Discovery
shuttle crews settled for a semi-retracted state that was enough to allow a
newer
set of solar wings to begin tracking the Sun
[image].
"It just
wasn't going to work for us today, but that stuff happens and I'm sure we'll
get through it," said Expedition
14 commander Michael
Lopez-Alegria told flight controllers, apparently
disappointed in the partial array
retraction.
"Well Mike,
actually, we consider it a success," NASA astronaut Steve
Robinson, serving as spacecraft communicator, replied adding that the P6
array was hauled in enough to activate the station's massive port Solar Alpha
Rotary Joint (SARJ) [image].
"We're looking at the SARJ rotating on the big screen and up there and we're
quite happy about it."
The
portside SARJ joint allows the station's Port 3/Port
4 (P3/P4) solar arrays to rotate like a paddlewheel and efficiently
generate power by tracking the Sun while
the ISS orbits the Earth [image].
That rotation is vital for the space station's future, since the P3/P4 solar
arrays will serve as the prime source of power after two planned spacewalks set
for Thursday and Saturday of this week.
Robinson
added that mission controllers are now discussing whether to add additional
tasks to the planned Saturday spacewalk for Discovery's STS-116 crew, add a
fourth spacewalk altogether to the mission, or reserve the remaining P6 array
retraction for a later ISS crew-only extravehicular activity (EVA) [image].
Stop and
go retraction
Wednesday's
retraction work marked the first time astronauts attempted to furl the 115-foot
(35-meter) P6 array, known as P6-4B, since the solar wing's initial
deployment in December
2000.
Retraction
began in earnest at about 1:28 p.m. EST (1828 GMT), but astronauts quickly
found that the array, which originally stretched out over the P3/P4 truss, was
prone to errant folds [image].
Slack in some array guide wires also caused some strife.
"It's
kind of like folding a map up," said Discovery's STS-116
commander Mark Polansky said as he watched the
process. "You have the folds in the paper, and if you
start folding it and the fold is going the wrong way, you can try a little bit
but there gets a point where it just bows out and there's nothing you can do
other than to pop it back in place or unfold it and try again."
That
prompted astronauts aboard the ISS to retract the P6-4B array until an errant
fold occurred, then extend the solar wing back out and try again, a technique that
newly arrived ISS
astronaut Sunita "Suni"
Williams said produced favorable results.
"Okay Suni, that's good news to hear. You've got a bunch of guys
about to turn blue here," astronaut Terry Virts told the ISS crew, prompting
laughs at NASA's Mission Control here since flight controllers said the same
thing to Neil
Armstrong and Buzz Aldrin after their 1969 Moon landing.
Solar
array rotation begins
In order to
begin rotating the P3/P4 truss, astronauts had to retract at least 40-percent
of the P6-4B array into its storage boxes.
Each
U.S.-built solar array aboard the ISS is made up of two "blankets" connected to
a pop-up mast divided into 31 ½ sections known as bays. To rotate the P3/P4
arrays, ISS and Discovery astronauts could leave a maximum of 19 mast bays of
the P6 array still deployed.
After hours
of back and forth motion, the astronauts managed to retract the array enough to
leave about 17 ½ bays exposed.
That gave ISS
flight controller the room they needed to commence rotation of P3/P4, which
began at about 8:00 p.m. EST (0100 Dec. 14 GMT). They also began filling an ISS
cooling system with its ammonia coolant.
Today's
array rotation and retraction work, along with the remaining STS-116
spacewalkers, are vital steps building up the ISS for the arrival of future
modules and laboratories, NASA officials said.
"The
station, for all this time, has been in this infant stage," John Curry, NASA's
ISS flight director for the STS-116 mission. "We need to go to the permanent
system so that we can add the Japanese
module Kibo and the [European Space Agency's] Columbus
later."
Those
modules are due to arrive at the ISS in 2007 and 2008, he added.
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