This
story was updated at 10:50 p.m. EST.
Astronauts
stepped outside the International Space Station Monday on the last leg of a
four-spacewalk marathon to clean and grease a vital, but damaged, solar array
gear.
Endeavour
shuttle astronauts Steve
Bowen and Shane Kimbrough spent just over six hours outside the station
cleaning metal grit from one last spot on the outpost's starboard solar
array-rotating gear and greasing up a working port side gear for good measure.
"Finally!" Bowen exclaimed after replacing a damaged bearing, cleaning
and lubricating the starboard side gear.
"Thanks
for your work," astronaut Terry Virts radioed up from Mission Control in Houston, which
erupted with applause when the tune-up concluded.
"You're
welcome," replied Bowen, but joked that he hopes to never visit the gear again.
After all, he worked on three
of the four spacewalks dedicated to the gear's repair on Endeavour's
spaceflight.
Before
Monday's spacewalk began, NASA mission managers extended Endeavour's initial
15-day mission by one more day in order to make more repairs to the space
station's beleaguered urine recycler. The system is designed to convert urine
back into drinkable water, but has been afflicted by early shutdowns.
Station
commander Michael Fincke and Endeavour astronaut Don Pettit removed vibration
dampeners from the system on Sunday in an unsuccessful
attempt to fully restore the system. They added a pair of extra brackets to
lock down the system's distilling centrifuge more securely today and began
processing new samples of urine.
If
the test is successful, station astronauts will continue to process urine for
further checks. But if it fails, mission controllers will consider pulling out
the problematic urine distiller and returning it to Earth for repairs aboard Endeavour, lead station flight
director Ginger Kerrick said late Monday.
Monday's
six-hour, seven-minute spacewalk ended earlier than its planned 6 1/2 hours due
to elevated levels of carbon dioxide in Kimbrough's spacesuit. While never in
danger, he was ordered back to the station airlock as a precaution once the
spacewalkers completed most of their assigned tasks.
"You
guys do amazing work," spacecraft communicator Mark Vande Hei called up from Mission Control.
Foundation for larger crews
The
space station's solar array-turning gears and its new urine recycler are two
essential systems to help the orbiting laboratory sustain
six-person crews and increased scientific research. The first six-person
crew is due to arrive at the station next May.
The
10-foot (3-meter) wide gear is designed to rotate the space station's solar
wings like a paddlewheel so they can always face the sun, which maximizes power
production. The starboard side gear has been mottled and damaged by metal
shavings from grinding parts for more than a year before Endeavour's crew
arrived.
NASA
plans to test drive the refurbished gear's ability to track the sun early
Tuesday at about 5:30 a.m. EST (1030 GMT).
The
space station's port side gear has been working fine, though the spacewalkers
did notice some slight wear as they greased its mechanism in some preventative
maintenance.
"It's
sort of a little junior version of what we have on the other side," Bowen said.
In
addition to their solar array gear work, Bowen and Kimbrough also added a video
camera and one of two antennas to the station's exterior to prepare for the
arrival of an unmanned Japanese cargo ship next year.
Endeavour
astronauts have spent about 26 hours and 41 minutes working outside the station
during the flight's four excursions. Monday's spacewalk marked the 118th
dedicated to station construction and the second for Kimbrough, who ended with
12 hours and 52 minutes of orbital work. It was the third excursion for Bowen,
who ended with 19 hours and 56 minutes of spacewalking time.
Watching water recycle
Meanwhile,
astronauts loaded the space station's water recycler with a new batch of urine
late Monday to check if their new repair attempt did the trick.
They
have managed to collect some samples from the system for the return to Earth,
but NASA managers want to collect as much data as possible before Endeavour
undocks on Friday. The system will be studied for about 90 days before
astronauts can take their first taste test of the recycled water, NASA has
said.
The
water recycler is part of a $250 million regenerative life support system
designed to recover 93 percent of the water from urine, sweat and other
wastewater for reuse by station astronauts. If it works properly, it can reduce
the amount of water delivered to the space station by about 743 gallons (2,850
liters) per year, NASA has said.
Fincke
told Mission Control he welcomed the chance for Endeavour's crew to stay docked
an extra day. All 10 astronauts will now spend Thanksgiving together before the
shuttle's Friday departure. Endeavour is due to land on Sunday at 1:18 p.m. EST
(1818 GMT).
"We
really enjoy having these guys up here and if we can only extend by one day that
will have to do," he said.
NASA is
providing live coverage of Endeavour's STS-126 mission on NASA TV. Click here for SPACE.com's
mission coverage and NASA TV feed.
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