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Circuit Breaker Fails Again Aboard ISS

A circuitbreaker has failed aboard the International Space Station (ISS), cutting offpower to one of three gyroscopes used to keep the orbital facility orientedproperly.

It is thesecond time in less than a year that the circuit breaker, called a remote powercontrol module (RPCM), has failed, leaving the ISS dependent on two operationalgyroscopes - the minimum required - to maintain attitude control.

NASA spokespersonKylie Clem told that the faulty circuit breaker will bediscussed Thursday during a regular scheduled ISS mission management meeting.

While noaction by the space station's current crew, Expedition 10 commander Leroy Chiaoand flight engineer Salizhan Sharipov, is immediately required, today's glitchmirrors one that occurred onApril 21, 2004, less than a day after the Expedition 9 crew boarded the ISS.

The circuitbreaker failure occurred this morning in a device that has already been replacedonce by space station astronauts. Expedition 9 crewmembers Gennady Padalka andMichael Fincke swapped out the device during one of the four spacewalks oftheir mission.

Expedition10's Chiao and Sharipov are scheduled to conduct an unrelated spacewalk on March28 - aimed at preparing the ISS to receive a European cargo ship - but whetherthey will have to perform an additional extravehicular activity was notimmediately known. At least one spare RPCM is available aboard the ISS.

The ISSactually carries four of the large U.S.-built gyroscopes used to orient itselfin space, though one has been inoperablesince 2002. The RPCM device functions as both power plug and circuit breakerfor ISS gyroscopes and today's glitch has left the station without a spareshould another one fail. Russian thrusters, which fire propellant to push thestation, can also be used to orient the ISS.

NASAalready has plans to ship a replacement gyroscope to the ISS aboard theDiscovery space shuttle during STS-114, currently set to launch in mid-May,though the space station must be able to maintain its position for thespacecraft to dock properly.

  • Complete Coverage: ISS Expedition 10

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