This
story was updated at 4:55 p.m. EDT.
HOUSTON - Two spacewalking astronauts
helped deliver a new orbital room to the International Space Station (ISS)
Friday and primed a massive solar power tower for its own move early next week.
Discovery astronauts
Scott Parazynski and Douglas Wheelock spent more than six hours working in
bulky spacesuits to ready the Italian-built
Harmony node for installation at the ISS among their other tasks.
"Now the
crews that are hot on our heels have a place to come," Parazynski said after
his crewmates Daniel Tani and Stephanie Wilson moved
the nearly 16-ton cylinder to a temporary spot on the station's Unity
module using the station's robotic arm.
About the
size of a small bus, Harmony increases the pressurized volume of the ISS by
2,666 cubic feet (75.4 cubic meters) and will serve as hub for new European and
Japanese laboratories that will launch toward the station on upcoming NASA
shuttle flights. The node was named by students
in a NASA contest and will be moved to its permanent home at the front of the
station's U.S. Destiny lab early next month by the outpost's Expedition 16
crew.
"It's just
a wonderful thing to see," John Shannon, head of Discovery's mission management
team, said Thursday of Harmony's ISS arrival. "This is the kind of mission that
we all came to NASA for. This is why we're here."
In addition
to aiding the Harmony module's installation, Parazynski and Wheelock stowed a
broken ISS antenna in Discovery's payload bay for return to Earth.
They also
prepared the station's Port 6 (P6) solar power truss segment for its planned
move, which is slated to begin Sunday. While disconnecting four coolant lines
between P6 and its Z1 truss base, Parazynski spotted several ice crystals of
toxic ammonia drift free. He underwent decontamination procedures to ensure his
spacesuit was clean after reentering the ISS airlock.
The
spacewalkers floated out of the ISS at 6:02 a.m. EDT (1002 GMT) as the station
passed over the west coast of South America.
They spent six hours and 14 minutes working outside the ISS.
Discovery
mission specialist Paolo Nespoli, an Italian astronaut from the European Space
Agency, choreographed the spacewalk from inside the shuttle and reminded his
crewmates to wave as the space station passed high over NASA's Mission Control
here in Houston, Texas.
"Great day
in outer space," Parazynski said.
Derek
Hassmann, NASA's lead ISS flight director, lauded Friday's successful spacewalk
and confirmed that Discovery's STS-120 crew will not have to conduct a
follow-up inspection of their spacecraft's heat shield on Saturday.
Instead,
the astronauts will spend time releasing some of the more than 700 launch
restraint bolts inside the Harmony node and outfitting it for orbital flight,
he added.
More
challenges ahead
Friday's
spacewalk marked the first of a record-tying five excursions planned for
Discovery's STS-120 mission, which NASA has called its most challenging
shuttle mission to date. Parazynski will perform four of the spacewalks,
while Wheelock will participate in three of them. Veteran shuttle flyer Pamela
Melroy is commanding Discovery's flight.
But despite
the complexity of today's Harmony node delivery, ISS mission managers said that
the upcoming move of the $276 million P6 solar array segment will be even more
difficult.
Over the
course of two spacewalks, astronauts will unbolt the 34,994-pound
(15,873-kilogram) truss, and then push the robotic arms aboard both the ISS and
Discovery to their performance edge to haul P6 from its mast-like perch above
the Unity node to a permanent spot on the left side of the station's
backbone-like main truss. Once P6 is reinstalled, its wing-like solar arrays
will have to be unfurled. NASA has encountered difficulties unfurling and
stowing them in the past.
"That's
quite a daunting task," said Kirk Shireman, NASA's deputy ISS program manager. "We'll all breathe a little easier once
we have it installed and the solar arrays deployed."
After
Friday's spacewalk, Shireman said mission managers will include an extra task
to the chore list for Parazynski and Tani - the astronaut team for Sunday's spacewalk.
One of the spacewalkers will inspect a rotary joint that turns the station's
starboard solar arrays to track the Sun.
The 10-foot
(three-meter) joint and its solar wings were installed at the ISS in June, but
it has recently shown signs of increased current and intermittent vibrations. A
loose thermal blanket or bolt could be causing slight friction, leading to the vibration,
Shireman told reporters.
Mission
Control roused Discovery's crew this morning with the song "Rocketman" by Elton
John, a tune specially chosen for Wheelock to celebrate
his first spacewalk.
Wheelock
now has one spacewalk of six hours and 14 minutes under his belt. Parazynski
has spent 26 hours and five minutes working outside a spacecraft during his
four spacewalks. Their excursion marked the 93rd spacewalk devoted
to space station assembly or maintenance since construction began in 1998, as
well as the 65th staged from the orbital laboratory itself.
"There
isn't a better job, is there?" Expedition 16 commander Peggy Whitson, the
station's first female commander, asked the spacewalkers as they headed out.
"Best job
in the universe," Parazynski replied.
NASA is broadcasting
Discovery's STS-120 launch and mission operations live on NASA TV. Click here for mission updates
and NASA TV from SPACE.com.
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