* Astronauts to hook up spare radiator
* Station maneuvered to avoid space debris
* Russian cargo ship arrives
By Irene Klotz
CAPE CANAVERAL, Fla., Nov 1 A pair of
spacewalking astronauts floated outside the International Space
Station on Thursday to attempt to bypass a leak in one of the
outpost's cooling systems.
Engineers suspect a micrometeoroid or tiny piece of space
debris may have punched a hole no bigger than the width of a
hair into one of the station's radiators.
The devices dissipate heat from batteries and other
equipment aboard the solar-powered station, a $100 billion
laboratory for biological, fluid physics and other science
experiments now flying about 255 miles (410 km) above Earth.
Station commander Sunita Williams and flight engineer
Akihiko Hoshide left the station's Quest airlock around 8:30
a.m. EDT (1230 GMT) for what was expected to be a 6.5-hour
spacewalk to reconfigure ammonia coolant lines and hook up a
The leak is small so it will take several weeks to determine
if the radiator was the source, said space station program
manager Mike Suffredini.
If routing ammonia through the spare radiator does not stem
the leak, another spacewalk to replace a pump or other equipment
in the system may be needed.
Unless it is fixed, the leak eventually would trigger the
cooling system to shut down, leaving the station without a
backup system for a section of the station's solar arrays.
The cooling system holds about 50 pounds (22.7 kg) of
ammonia. It would automatically shut down if the ammonia level
drops to 40 pounds (18 kg), said flight director Mike Lammers.
As ground control teams prepared for the spacewalk on
Wednesday, the station had to maneuver to avoid another piece of
debris. This piece was part of the wreckage from the 2009
collision of an Iridium communications satellite and a Russian
The maneuver fell a bit short due to a software issue that
prevented all the thrusters on a Russian cargo ship attached to
the station from firing. NASA said the station, a project of 15
nations, was repositioned out of harm's way, with no further
rocket firings needed.
While Williams and Hoshide worked outside, their four
crewmates began unpacking another Russian Progress cargo ship
that arrived on Wednesday.