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  sci-tech > space > story pagecorner  

Endeavour launch scrubbed following computer glitch

CAPE CANAVERAL, Florida (CNN) -- An unexplained problem with a key computer system has forced NASA to scrub Tuesday's planned launch of the space shuttle Endeavour.

Space shuttle


The earliest Endeavour could now launch is February 9.

Steady rain and thick clouds thwarted attempts to launch Endeavour on Monday afternoon -- and problems mounted as technicians worked on a balky avionics box in Endeavour's aft engine compartment.

While the six-person crew made its way back to quarters on rain-slicked roads, engineers were troubleshooting a problem with one of two so called Master Events Controllers which relay critical commands from the shuttle's computers to jettison the external fuel tank and the solid-rocket boosters.

It is "absolutely critical that they work," according to Shuttle Program Manager Ron Dittemore.

Since the two Master Events Controller are redundant, the loss of one would not create a problem. But if that were to happen, the shuttle would be only one failure away from a so-called "Criticality One" failure -- meaning catastrophic loss of the vehicle and crew.

As a result, NASA has a firm flight rule not to launch if there is uncertainty about the health of one of the controllers.

The suspect controller failed a routine health check as the countdown reached T-minus 20 minutes. Computers send the 65 pound, microwave-sized avionics boxes a series of commands that prompt a response. In this case the response was not what was hoped for.

"It's looking for a particular pattern of ones and zeroes. If it recognizes the right pattern you pass the health check and if it looks like the ones and zeros are in the wrong places you fail the health check," said Dittemore.

The balky Controller passed a second health check -- but that is not enough to satisfy the launch team. Until they fully understand why it failed the first test, they will not fly.

"We don't know exactly what happened to it, but we know not to fly with it", NASA spokesman George Diller told CNN.

These boxes have caused NASA headaches before. In 1984, the maiden voyage of Discovery was delayed a day while the launch team cobbled together a software patch to fix a glitch in a Master Events Controller.

And in 1995, Columbia's crew had to wait a week while technicians replaced a balky controller that failed 20 seconds before the planned liftoff.

Endeavour's six person crew is set to fly an 11-day $600 million radar mapping mission. The 3-D topographic map will cover 70 percent of the Earth's surface -- and be use by scientists and the Pentagon.

Space Correspondent Miles O'Brien contributed to this report.

Space Correspondent Miles O'Brien contributed to this report.

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