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Glitches bedevil space station steering

The space station is relying on Russian-made thrusters for major maneuvers due to problems with the gyroscopic control system, NASA says.
/ Source: The Associated Press

NASA is relying on Russian-made thrusters to periodically turn the international space station following a new malfunction with the U.S. motion-control system, officials said Friday.

Flight controllers detected spikes in current and vibration in one of the station’s three operating gyroscopes on Nov. 8. Last week, when the gyroscopes were used again to shift the position of the orbiting outpost, all three worked fine.

The three gyroscopes still are being used for day-to-day cruising. But to prevent further trouble and give engineers time to evaluate everything, the spinning wheels will not be used for major maneuvers for at least the next month and the Russian thrusters will assume control at those times, said flight director Joel Montalbano. The station must be periodically moved into a new position to prevent the exterior from getting too hot from the sun.

The main drawback is the use of thruster fuel. For now, the two-man station has more than enough fuel to spare, said program manager Bill Gerstenmaier.

A fourth gyroscope broke in 2002. Only two good gyroscopes are needed at any given time to control the space station.

“It’s not where we want to be and we definitely don’t want to get there, but we have much backup capability ... and we’re not in any kind of real crisis,” Gerstenmaier said.

Gyroscopes are too big to fit into a Russian supply ship, so NASA cannot send up a spare until the shuttles are flying again. The shuttle fleet has been grounded since Columbia broke apart during re-entry in February.