A circuit
breaker has failed aboard the International Space Station (ISS), cutting off
power to one of three gyroscopes used to keep the orbital facility oriented
properly.
It is the
second time in less than a year that the circuit breaker, called a remote power
control module (RPCM), has failed, leaving the ISS dependent on two operational
gyroscopes - the minimum required - to maintain attitude control.
NASA spokesperson
Kylie Clem told SPACE.com that the faulty circuit breaker will be
discussed Thursday during a regular scheduled ISS mission management meeting.
While no
action by the space station's current crew, Expedition 10 commander Leroy Chiao
and flight engineer Salizhan Sharipov, is immediately required, today's glitch
mirrors one that occurred on
April 21, 2004, less than a day after the Expedition 9 crew boarded the ISS.
The circuit
breaker failure occurred this morning in a device that has already been replaced
once by space station astronauts. Expedition 9 crewmembers Gennady Padalka and
Michael Fincke swapped out the device during one of the four spacewalks of
their mission.
Expedition
10's Chiao and Sharipov are scheduled to conduct an unrelated spacewalk on March
28 - aimed at preparing the ISS to receive a European cargo ship - but whether
they will have to perform an additional extravehicular activity was not
immediately known. At least one spare RPCM is available aboard the ISS.
The ISS
actually carries four of the large U.S.-built gyroscopes used to orient itself
in space, though one has been inoperable
since 2002. The RPCM device functions as both power plug and circuit breaker
for ISS gyroscopes and today's glitch has left the station without a spare
should another one fail. Russian thrusters, which fire propellant to push the
station, can also be used to orient the ISS.
NASA
already has plans to ship a replacement gyroscope to the ISS aboard the
Discovery space shuttle during STS-114, currently set to launch in mid-May,
though the space station must be able to maintain its position for the
spacecraft to dock properly.
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