A pair of
spacewalking astronauts will head outside the International Space Station (ISS)
Monday to install a pair of massive girders and two new solar wings to boost
the outpost’s power grid.
Atlantis
shuttle astronauts Jim
Reilly II and Danny Olivas will don their white NASA spacesuits and step
into space at 2:53 p.m. EDT (1853 GMT) today for a 6.5-hour construction job attaching
the 17.5-ton truss segments and solar arrays to the station’s starboard side.
“[W]e’ll be
balancing out the station with the solar arrays on that side,” Reilly said in a
NASA interview. “And that’s our primary, and relatively simple, objective, when
you look at it from that standpoint.”
Working in
concert with robotic arm-wielding astronauts inside the space station, Reilly
and Olivas will install the joined Starboard
3/Starboard 4 (S3/S4) trusses and arrays which, once extended to their full
240-foot (73-meter) wingspan, will increase the space station’s power supply. At
35,678 pounds
(16,183 kilograms), they make up the heaviest addition to the ISS to date.
“We’ll have
much more redundancy in the power system,” Kirk Shireman, NASA’s deputy ISS
program manager, said Sunday of the S3/S4 installation. “And we’ll be in a
better configuration for later on in building the space station.”
The new
solar arrays, which ultimately produce about 14 kilowatts of usable power, will
boost the station’s power capacity up by about seven kilowatts once an older
solar wing is furled later in the mission, Shireman said. Its installation will
help the ISS power future modules and laboratories waiting to fly.
Reilly and
Olivas will also follow a new NASA rule to check their
spacesuit glove-clad hands after each task, especially those handling
objects near sharp edges. During NASA’s last ISS construction mission in
December 2006, one of the gloves worn by spacewalker Robert Curbeam suffered a
three-quarters inch (two-centimeter) cut to its outermost protective layer,
which prompted the new rule.
“The plan
is to check after every task, so you do a task and you check your glove,”
Shireman said. “We’re optimistic that we won’t have any damage, but that’s
certainly going to be the procedure from now on.”
Commanded
by veteran shuttle flyer Rick Sturckow, Atlantis’ STS-117 mission is the first
of four-planned ISS construction flights this year. The astronauts launched
spaceward June 8 and arrived at the space station Sunday afternoon.
Old job,
sticky bolts, new tools
The primary
tasks of today’s truss and solar wing installation are a near-mirror image of
those performed during NASA’s STS-115 shuttle flight, which delivered the Port
3/Port 4 (P3/P4) trusses and solar arrays to the port side of the ISS in
September 2006.
But Reilly
and Olivas will have a new
tool at their disposal that their STS-115 predecessors did without - a
torque multiplier - that amplifies by 12 times the amount of force applied by a
spacewalker on stubborn bolts. In order to fully prepare the S3/S4 truss for
use at the ISS, the spacewalkers must complete remove or unlock a series of
bolts, restraints and launch locks no matter how tightly secured they may be.
“We’re
going to be able to install S3/S4 even more flawlessly that the way P3/P4 went
up,” Olivas said in a NASA interview.
Like its
portside counterpart, the two separate elements of the S3/S4 truss structure is
joined at the midpoint by a massive joint that allows the outer S4 section to
rotate like paddlewheel so that its solar arrays can track the Sun. The arrays
themselves are due to be unfurled on Tuesday.
The inner,
S3 element will be attached to the space station’s Starboard 1 element -- there
is no Starboard 2 section -- via the station’s robotic arm, wielded by former
ISS flight engineer Sunita Williams and shuttle pilot Lee Archambault, at about
11:08 a.m. EDT (1608 GMT) before the spacewalkers exit the station’s Quest
airlock. Shuttle astronauts plucked the S3/S4 truss out of Atlantis’ cargo bay
late Sunday, at times with only inches separating it from the shuttle’s inner
walls, using the orbiter’s arm to then hand it off to the station’s own
appendage.
“It is
delicate work, and the tolerances are small, but we have good aids on board,”
Archambault has said of today’s truss installation.
Reilly, a
veteran spacewalker, will make the fourth extravehicular activity (EVA) of his
astronaut career during today’s orbital work and will wear red-striped
spacesuit. Olivas, meanwhile, is making his first spacewalks, as well as his
first spaceflight, during the STS-117 mission and will don an all-white
spacesuit.
“I’m very
much looking forward not only to turning around and looking at Earth…but also
turning around and looking into space,” Olivas said before flight. “[R]eally,
the only thing separating you and the rest of the universe is, you know, a
think visor. I think it’s going to be a pretty neat experience.”
NASA is
broadcasting the space shuttle Atlantis' STS-117 mission live on NASA TV. Click here for mission updates and
SPACE.com's video feed.
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