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Space station gyroscope fails; spacewalk needed

By Michael Coren

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(CNN) -- NASA announced Thursday that the second of the International Space Station's four stabilizing gyroscopes failed on Wednesday night, but neither the station nor the crew were in immediate danger.

The malfunction was caused by a power failure, forcing controllers to rely on the two remaining gyroscopes to keep the structure's position in orbit.

The first gyroscope broke two years ago as a result of a bearing failure. Two more are still operating -- the minimum required -- but one has exhibited power surges and vibrations over the past year. If another gyroscope breaks, thrusters on the docked Russian capsule and the station would have to assume control over the massive orbiting structure for as long as a year.

"It's not alarming to the team, it's just something we're trying to work through," said Mike Suffredini, operations manager for the International Space Station. "I'm several failures away from not being able to control the vehicle."

The most recent problem developed at 4:18 p.m. ET Wednesday afternoon, less than a day after the new crew, Astronaut Michael Fincke and cosmonaut Gennady Padalka, arrived at the station. Five people, including the previous crewmembers and an astronaut from the European Space Agency, are now living temporarily aboard the station.

On Wednesday night, controllers watched as the second gyroscope slowly came to a halt. To stabilize the station, thrusters onboard the Soyuz were fired five times to maintain control of the station as two other gyroscopes -- wheels spinning at 6600 revolutions per minute -- were brought on-line.

NASA believes an electrical circuit housed in what is known as a remote power control module failed. It ruled out a mechanical problem after engineers failed to detect a power surge or erratic motion of the instrument. Scientists said metal oxide inside the circuit had probably broken down leading to premature failure.

The agency expects to send two station astronauts on a four-hour spacewalk to resolve the problem. The station has two suitable spare parts to repair the gyroscope's power supply, but Suffredini estimated that would not happen for at least another month.

Astronauts will need to unscrew a panel on the exterior of the station and replace what amounts to a fuse box servicing the gyroscope. Eventually, NASA hopes to replace all of the station's gyroscopes with updated models.

Repairs are complicated because the space shuttles were grounded following Columbia's breakup on re-entry in 2003. The shuttles are not scheduled to fly again until 2005, or perhaps longer, when NASA can recertify the fleet as flightworthy. Until then, the 4-foot wide gyroscopes are too big to fit through the hatch of the small, unmanned Progress capsules arriving to resupply the station.

The latest Expedition 9 crew is not scheduled to return to Earth for another six months. The previous crew plans to leave the station April 29. The next resupply vehicle, known as Progress 14, will lift off for the station in May.

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