NASA's willingness to bend rules for today's launch draws reproof

CAPE CANAVERAL, Fla. — With the countdown entering its final hours and a fuel gauge problem still unexplained, NASA said it is prepared to bend its long-standing safety rules to launch the shuttle today on the first flight since Columbia's doomed mission 2 1/2 years ago.

Discovery and a crew of seven were set to blast off for the international space station at 8:39 a.m. MDT, after a two-week delay caused by a malfunctioning hydrogen fuel gauge in the spaceship's giant external tank.

Nature, rather than the fuel gauge, could ultimately decide whether Discovery takes off. Forecasters put the odds of good launch weather at 60 percent, with rain and storm clouds both posing threats.

NASA had the paperwork ready to go in case the equipment trouble reappeared and the space agency's managers decided to press ahead with the launch with just three of the four fuel gauges working. That would mean deviating from a rule instituted after the 1986 Challenger explosion.

"It's an acceptable risk and actually it's quite a low one," NASA Administrator Michael Griffin said in an interview with The Associated Press late Monday afternoon. If the same fuel gauge problem occurs, "we would be good to go," he said. "If we see some other signature than what we saw before, then we're not going. We're absolutely not going."

The fuel gauges are designed to prevent the main engines from running too long or not long enough, in case the fuel tank is leaking or some other major breakdown occurs. An engine shutdown at the wrong time could prove catastrophic, forcing the astronauts to attempt a risky emergency landing overseas or leading to a ruptured engine.

Griffin noted that multiple failures would have to occur in multiple systems for the worst-case scenario to come true.

Only two gauges, or sensors, are needed to do the job. But ever since NASA's return to space in 1988, the space agency has decreed that all four have to work to proceed with launch.

NASA test director Pete Nickolenko said he did not remember the last time one of these launch rules was waived. But he expressed confidence in NASA's game plan and said the space agency had done everything to understand the fuel gauge problem, which first cropped up during a test in April and resurfaced during the launch attempt July 13.

Over the past few days, NASA rewired two of the sensors to try to diagnose the trouble and repaired faulty electrical grounding aboard Discovery in hopes that would solve it.