New Circuit Breaker... Breaks

Remember that gyroscope circuit breaker astronauts installed during an EVA last year? It was supposed to replace a circuit breaker that had failed, leaving the International Space Station with only two gyros to stabilize it and keep it oriented in such a way that the solar panels were directed toward the sun. Well, the replacement circuit breaker apparently needs to be replaced.

The new part failed Wednesday, once again leaving the ISS with just two of its four gyros in working order. There is a spare on board, but replacing the replacement part will be especially difficult since there are still only two crew members aboard the station. If they leave the station on a spacewalk, there won't be anyone inside to keep things running while they're gone. One other gyro has been inop for three years, and is scheduled to be replaced during the next shuttle mission.

Despite the breakdown, NASA reported Commander Leroy Chiao and Flight Engineer Salizhan Sharipov maintained a normal schedule, including a maintenance stint on one of the oxygen generators.

The gyro affected is the same one knocked out when a circuit breaker failed in April 2004. Two months later, Commander Gennady Padalka and NASA ISS Science Officer Mike Fincke staged a daring spacewalk (above) -- leaving the station unmanned -- to repair it.

But this time, the gyro problem could cause problems for the space shuttles' return to flight. NASA plans to launch Discovery in about two months, the first shuttle flight since the in-flight destruction of Columbia on February 1st, 2003. That mission may have to wait, though, if there are any questions about the station's stability in orbit.

But Chiao and Sharipov are already scheduled for an EVA on March 28th, where they are to perform routine maintenance tasks. There is no word yet on whether the troublesome breaker might be repaired during that spacewalk -- but there is at least a window of opportunity.

FMI: http://spaceflight.nasa.gov/station