09:27 PM PDT on Monday, July 25, 2005

Associated Press

CAPE CANAVERAL, Fla. - Still perplexed by a fuel gauge problem, NASA managers said Monday they are prepared to bend their own safety rules to launch Discovery on Tuesday on the first shuttle flight since the Columbia tragedy 2 ½ years ago.

They said they may approve a waiver - or an exception to the launch rules - if the problem crops up again during fueling.

At the same time, Pete Nickolenko, a NASA test director, expressed confidence the sensor would work properly.

“Personally, I think that we’ve done an extensive degree of troubleshooting and analysis ... to best understand what we’ve got,” he said. “We fully expect that it should work as designed.”

Engineers still do not fully understand why one of the four hydrogen sensors in the big external fuel tank gave a misreading July 13, forcing NASA to scrub the first flight as the astronauts were boarding Discovery. The rescheduled launch is set for 10:39 a.m. Tuesday.

The space agency’s own launch rule - in place since the 1986 Challenger disaster - requires that all four sensors be working properly, though only two are actually needed.

NASA workers rewired some of the sensors and made other electrical repairs after the failure, and Nickolenko said that after extensive troubleshooting, “I think we’re smarter in understanding exactly what we have.”