Posted: March 16, 2005A circuit breaker aboard the international space station popped open early today, interrupting power to one of the three operational gyroscopes used to maintain the lab's orientation in space. NASA officials said the failure would have no immediate impact and that the space station's orientation could be maintained with just two gyros while engineers study the problem.The circuit breaker in question, known as a remote power controller, wasinstalled during a spacewalk last June by Expedition 9 commander GennadyPadalka and flight engineer Mike Fincke. The unit replaced one that failedApril 21, 2004. It is not yet known what caused the replacement RPC to failat 3:17 a.m. EST (0817 GMT) today.The space station is equipped with four massive control momentgyroscopes. By controlling how fast the gyros spin, the station can bere-oriented or maintained in a desired "attitude" without using Russianrocket thrusters and tapping into limited amounts of on-board fuel.CMG-1 failed and shut down June 8, 2002. A replacement will be carriedaloft aboard the shuttle Discovery in May for installation during one ofthree spacewalks by shuttle astronauts Stephen Robinson and Soichi Noguchi.While the station can operate with just two gyros, NASA wants to restorefull redundancy as soon as possible to protect against additional failuresdownstream.The loss of CMG-2, assuming it cannot be brought back on line, is not inand of itself a constraint to Discovery's launch. But without threeoperating gyros, the combined station-shuttle crews would not be able tore-position Discovery with the ship's robot arm for possible repairs if anymajor debris-related damage is incurred during launch.While no one expects such damage, NASA is viewing Discovery's mission as atest flight of sorts to make sure modifications to the shuttle's externalfuel tank will work to minimize foam shedding. Just in case, flightcontrollers have devised plans for re-orienting the shuttle after it isdocked to the station to provide access if repairs in hard-to-reach areasare, in fact, required.At least one spare RPC already is aboard the space station andDiscovery's crew will deliver four more. But no decisions about a possiblespacewalk replacement will be made until flight controllers and engineershave exhausted ongoing efforts to restore the RPC to service by remotecontrol."Flight controllers will continue to try commanding that RPC closed todayand mission managers will assess the condition of the circuit breaker ...tomorrow morning," said a NASA spokeswoman in mission control at the JohnsonSpace Center in Houston.In other developments, the space station's Russian Elektron oxygengenerator, which shut down late last week, is back in operation. After extensive troubleshooting, the unit was successfully restarted at 7:53 a.m. EST today.Telescopes.comLargest selection and the best prices anywhere in the world. Free shipping on select items.
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