Countdown Underway Toward Tuesday Shuttle Launch

Buoyed by hopes its mysterious fuel-tank sensor problems have been resolved, NASA has resumed the countdown toward a Tuesday launch of the space shuttle Discovery.

"No doubt there is some degree of finger crossing," NASA test director Pete Nickolenko said before the clock began to run Saturday. "But the other side of the coin is that we have really performed a very thorough troubleshooting analysis to a great degree, an excruciating degree of detail with all the shuttle program experts and the contractors that we can get." Nickolenko was quoted by the Associated Press.

Fourteen teams of engineers scouring the shuttle and its mammoth, orange external fuel tank for clues about the malfunction found and repaired three possible wiring malfunctions over the weekend. In each case, engineers suspected poor grounding was responsible for the July 13th glitch that forced them to scrub the much-vaunted Return to Flight.

They also switched out wiring within the tank itself, between the suspect fuel depletion sensor and another, similar device.

In the process of all this, engineers said they had eliminated more than 300 possible causes of the flight-scrubbing glitch. Still, there was no sense of certainty at the Kennedy Space Center that the problem had been solved.

If it hasn't, then NASA managers are considering a rule change.

In the wake of the 1986 Challenger disaster, NASA ruled that all four of the sensors in the external fuel tank must be operative in order to launch. But the space agency may now allow the orbiter to fly with only three of the sensors operating -- provided the inoperative sensor is the same one that failed during the July 13th launch attempt and the symptomology is similar.

That, however, might raise the ire of government watchdogs who've been keeping an eye on the process of returning the space shuttle fleet to operational status more than two years after the Columbia disintegrated on re-entry. As in the Challenger tragedy, all seven astronauts aboard Columbia were lost.

Then there's the weather. Forecasters Sunday said there was a 40-percent chance of a weather-spawned launch scrub.

FMI: www.nasa.gov