SPACEWALKING ASTRONAUTS HUNT FOR BIG STATION LEAK

In this image made from
video provided by NASA,
astronauts Chris Cassidy,
foreground, and Tom
Marshburn prepare for a
possible spacewalk from the
International Space Station
on Friday, May 10, 2013.
NASA will decide later Friday
if the two astronauts will
step outside the station to
work on a leaking coolant
line. The line chills power
systems but power was
rerouted and is operating
normally. The six-member
crew is not in danger. (AP
Photo/NASA)
CAPE CANAVERAL, Fla. (AP) —
Two astronauts took a hastily
planned spacewalk Saturday to
find and, possibly, fix a serious
leak at the International Space
Station.
Flakes of frozen ammonia
coolant were spotted Thursday
drifting from the long frame
that holds the solar panels on
the left side. Less than 48 hours
later, Thomas Marshburn and
Christopher Cassidy emerged
from the orbiting lab to hunt
for the leak. They were
prepared to replace a pump, if
necessary.
NASA said the leak, while
significant, poses no safety
threat. But managers wanted to
deal with the trouble now,
while it's fresh and before
Marshburn returns to Earth in
just a few days.
The space agency has never
staged such a fast, impromptu
spacewalk for a station crew.
Even during the shuttle days,
unplanned spacewalks were
rare.
At the beginning of the
spacewalk, neither astronaut
spotted any flakes of ammonia
or anything else amiss as they
reached the spot in question
and began an inspection.
"I see nothing off-nominal,"
Cassidy said. He noted some
smudges, but nothing more.
The astronauts needed to take
pictures of the equipment, but
the connection to the camera's
flash was not working and
Marshburn had to wait until
the space station reached the
daylight side of Earth.
Flight controllers in Houston
worked furiously to get ready
for Saturday's operation,
completing all the required
preparation in under 48 hours.
The astronauts trained for just
such an emergency scenario
before they rocketed into orbit;
the repair job is among NASA's
so-called Big 12.
This area on the space station is
prone to leaks. The ammonia
coursing through the plumbing
is used to cool the space
station's electronic equipment.
There are eight of these power
channels, and all seven others
were operating normally. As a
result, life for the six space
station residents was pretty
much unaffected, aside from
the drama unfolding Saturday
255 miles above the planet.
NASA's space station program
manager Mike Suffredini said
it's a mystery as to why the
leak erupted. One possibility is
a micrometeorite strike. If
there is nothing to suggest that
the old pump is at fault, then
the spacewalkers expect to
leave it in place and go back
inside as flight controllers
figure out the next step.
Marshburn has been on the
space station since December
and is set to return to Earth
late Monday. Cassidy is a new
arrival, on board for just 1½
months.
"Suddenly very busy,"
Marshburn said via Twitter on
Friday.
By coincidence, the two
performed a spacewalk at this
troublesome spot before, during
a shuttle visit in 2009.