Two astronauts will step outside the International Space
Station (ISS) Tuesday afternoon to install a new piece to the orbital
laboratory’s metallic backbone.
Clad in
white NASA spacesuits, Discovery shuttle astronauts Robert
Curbeam and Christer
Fuglesang are expected to exit the space station’s Quest airlock at
3:42 p.m. EST (2035 GMT) and spend about six and a half hours working in orbit.
Their
primary goal is the installation of a new piece of the ISS—the Port
5 (P5) spacer—to the portside end of the station’s main truss.
Small, but
vital, the boxy P5
truss is designed to serve as a bridge between the station’s Port 3/Port
4 (P3/P4) solar arrays and the Port
6 (P6) solar array element. The P3/P4 extends off to the station’s
port side, but the older P6 array reaches upward, mast-like
from the orbital laboratory’s centerline and will be moved during a later
shuttle mission [image].
“This
truss that we’re bringing up, the P5 truss, is almost like a spider,”
said Curbeam, who is the lead spacewalker of STS-116,
in a preflight NASA interview. “It allows us to take the P6 truss, which
has been up there for several years now…and put it in its rightful place,
if you will.”
Curbeam’s NASA spacesuit, known as an Extravehicular Mobility Unit (EMU), will
sport a red stripe and U.S. flag, while that of Fuglesang—who
represents the European Space Agency—is all-white and carries a Swedish
flag in honor of his homeland. Shuttle pilot William
Oefelein will coordinate the spacewalkers’ movements from the flight
deck of Discovery.
Today’s
spacewalk will mark the fourth extravehicular activity (EVA) for Curbeam and the first for Fuglesang.
The EVA is also the first of three planned during their STS-116
mission to install P5 and rewire
the space station’s electrical grid.
A tight
squeeze
Discovery
astronauts plucked the two-ton P5 truss out of the shuttle’s payload bay
after docking
at the ISS late Monday. They later it to the end of the space station’s
robotic arm, leaving it in a parked position for today’s spacewalk.
Later
today, STS-116 mission specialist Joan
Higginbotham and newly arrived ISS astronaut Sunita
Williams–who rode
up to the station aboard Discovery–will ease P5 into position with a
delicate touch, relying on Fuglesang to call out distances and directions as
the truss comes within inches of space station hardware.
“Picture
as if you’re helping a friend park in a very tight spot,” lead
STS-116 spacewalk officer Tricia Mack said of today’s truss installation.
“You’re going to want to give them a, ‘Whoa, back a little to
the right, a little to the left.’”
The parking
analogy is more than apt since, 11 feet (3.3 meters) long, the P5 truss is about
the length of a compact car, NASA officials said. Built by Boeing, the truss
element is also 14 feet (4.5 meters) wide and stands about 13 feet (4.2 meters)
high.
Higginbotham
said she will be depending on Fuglesang’s verbal calls to avoid damaging
P5 or the ISS.
“There
are very few cameras on that side of the truss,” Higginbotham said before
flight, adding that she is especially wary of hitting an electronics box on a
nearby P3/P4 truss solar array. “We’re coming within inches of that
box, and it’s a box that, you know, if you hit it, you can cause
sparks.”
Curbeam and
Fuglesang will remove a series of launch locks and restraints from P5 before it
is in place, then secure it to the ISS via drill-driven bolts.
In addition
to installing P5, Curbeam and Fuglesang plan to relocate a grapple fixture on the
segment and replace a broken camera elsewhere on the space station’s main
truss.
For
Fuglesang, who is making his first spaceflight as well as his first spacewalks
during the STS-116 mission, today’s EVA debut is a welcome challenge.
“I’m
sure it’s going to be fantastic,” Fuglesang said in a NASA interview.
“But, really, going out, you cannot be more in space than doing a
spacewalk.”
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