HOUSTON
– Two spacewalking astronauts added a new piece to the growing
International Space Station (ISS) Saturday while engineers on Earth
analyzed a U.S computer glitch and damage to the shuttle Endeavour.
STS-118
mission specialists Rick Mastracchio and Dave Williams bolted a new Starboard 5
(S5) spacer truss to the end of the space station's metallic backbone, among
other construction tasks, during their six-hour-and-17-minute spacewalk.
"You
guys were awesome," shuttle commander Scott Kelly told the two
spacewalkers after they finished their work.
Known
affectionately as "Stubby," the S5 truss makes way for a new solar
array on the growing orbital laboratory. Addition of the 4,010-pound
(1,818-kilogram) block gives the ISS an end-to-end length of 246 feet (75
meters) and a weight of about 513,000 pounds (233,000 kilograms).
About the
only hitch while Mastracchio and Williams toiled outside the orbital laboratory
occurred inside the station's U.S. segment.
At about
3:52 p.m. EDT (1952 GMT), the station's primary U.S. command and control
computer shut down inside NASA's Destiny laboratory, forcing two backups to
take over as designed. The six-year-old computer's shutoff had no effect on
Saturday's spacewalk, but engineers are studying the problem to track the failure's
source.
Computer
failures plagued the station's last visiting shuttle mission in June, when
computers governing the station's Russian navigation and control systems
crashed. The space station's current Expedition 15 crew revived the ailing
machines by installing jumper cables to bypass faulty components. More repairs
for those computer systems are slated to begin Sunday while Endeavour is docked
to the ISS.
The
computer failure occurred just one day after NASA engineers discovered damage
to the heat-resistant belly of Endeavour, prompting mission managers' concerns
for safe reentry to Earth.
Engineers
think a spray of ice chiseled out pieces of heat-resistant tiles just under a
minute after Endeavour's launch on Wednesday evening, but need more information
to fully assess the extent of damage. STS-118 crewmembers hope to scan the damage
in detail using the space shuttle's sensor-tipped extension boom on Sunday at
about 12:06 p.m. EDT (1606 GMT).
Growing
laboratory
While
hooking up the S5 truss to the space station, astronauts had a nearly
unobstructed view of the blue planet 214 miles (344 kilometers) beneath them.
"The
view is incredible," Williams said during the installation of the $11
million, Boeing-built truss.
The
spacewalking astronauts also relocated a spare grappling fixture, which allows
the space station's robotic arm to safely grab space station components and
move them around. After the relocation, Mastracchio and Williams retracted a radiator
on the station's mast-like Port 6 truss, clearing the massive segment for
relocation to the orbital laboratory's port-most side later this year.
"You
guys look like those toys in a souvenir shop," mission specialist Tracy
Caldwell told the astronauts outside of her space station window during the
retraction. Caldwell served as spacewalk choreographer, delivering instructions
and advice during the busy construction outing.
With time
to spare after their primary tasks, Mastracchio and Williams squeezed in
several "get-ahead" tasks to accelerate construction of the space
station.
Endeavour's
seven-astronaut crew is delivering spare ISS hardware, 5,000 pounds (2,267
kilograms) of fresh cargo and replacing a failed gyroscope to the space station
during the their up-to-14 day mission.
Throughout
Saturday's spacewalk, teacher-astronaut
Barbara Morgan oversaw the transfer some of that cargo. Morgan waited 22
years for the opportunity, following the loss of the 1986 Challenger crew. She
was assigned to Endeavour's STS-118 mission in 2002 after becoming a
full-fledged astronaut in 1998.
STS-118
astronauts are expected to perform at least two more spacewalks during the next
six days, although a new device that shares space station solar power with
Endeavour could allow for a fourth spacewalk. Mission managers will decide by
Sunday afternoon whether or not to extend the mission by three days.
"[It]
may make us, if it works properly, the longest docked mission to the space
station to date," Kelly said in an interview with SPACE.com.
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