This
story was updated at 10:11 p.m. EDT.
Two
schoolteachers-turned-astronauts floated outside the International Space
Station Monday to wrap up some unfinished work, but were stymied by a stuck
cargo carrier on the orbiting lab.
Discovery
shuttle astronauts Joseph Acaba and Richard Arnold II pushed and pulled on the
jammed carrier with all their strength, then attacked it with a hammer to
push aside a pin that was incorrectly installed in a Saturday spacewalk.
But their efforts
were to no avail, perplexing the spacewalkers. Engineers believe the catch
securing the mechanism may be too stiff for spacewalkers to budge by hand.
"I just
don't see anything in the way," one of the astronauts said.
The
spacewalkers ultimately lashed
down the swing-out carrier, which is intended to hold future spare parts,
using sturdy tethers to keep it in place until engineers on Earth can come up
with a fix. Mission Control canceled plans for the spacewalkers to swing out a
second spare parts platform because of the glitch.
Mission
managers said the stuck carrier could remain tied down for years if necessary,
but NASA wants to use both cargo platforms to store much-needed spare parts at
the station later this fall.
"Certainly,
we can't fly that mission that's bringing up these critical spares for us until
we get this problem resolved," lead space station flight director Kwatsi
Alibaruho told reporters late Monday from the Johnson Space Center in Houston.
Alibaruho said he wasn't too disappointed with the stuck carrier because there
is time in the months ahead to fix it and Discovery's spacewalkers achieved all
their most critical goals.
Acaba
and Arnold spent 6 1/2 hours working outside the space station without
concern of a piece of space junk that was predicted to buzz by the orbiting lab
during their spacewalk. Their piece of mind came on Sunday, when astronauts
used thrusters on Discovery to move the docked shuttle and space station clear
of the 4-inch (10-cm) piece of a spent Chinese satellite rocket stage.
Monday's
spacewalk was the second for Acaba and Arnold, and the first time a pair
of former schoolteachers has ventured out into space together. Both
astronauts joined NASA's spaceflying ranks in 2004 as part of its cadre of
educator astronauts and are making their first spaceflight.
"Take your
time, enjoy it and do good work," station commander Michael Fincke told the
astronauts as they began their work at 11:37 a.m. EDT (1537 GMT).
In addition
to tackling the stubborn cargo carrier, Acaba and Arnold moved an equipment
cart from the port side of the space station's backbone-like main truss to the
starboard side. They also greased up the grappling end of the space station's
robotic arm and performed other maintenance work.
Monday's
spacewalk marked the 123rd dedicated to space station construction and the
third and last planned for Discovery's 13-day mission to deliver a new
crewmember and the outpost's last
pair of gleaming solar wings.
Acaba and
Arnold each performed an earlier spacewalk with astronaut Steven Swanson, who
choreographed Monday's orbital work from inside Discovery. Acaba finished
today's work with 12 hours and 57 minutes during his two excursions, while
Arnold wrapped up with 12 hours and 34 minutes of spacewalking time.
Altogether,
Discovery's crew spent a total of 19 hours and four minutes working outside the
space station.
"Thanks for
the hard work," Discovery commander Lee Archambault told the spacewalkers.
"You've left the space station a much better place than it was 6 1/2 hours
ago."
Discovery
is due to undock Wednesday from the space station and head toward a planned
Florida landing on Saturday.
SPACE.com
is providing continuous coverage of STS-119 with reporter Clara Moskowitz and
senior editor Tariq Malik in New York. Click here for mission
updates and SPACE.com's live NASA TV video feed.
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