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New Rules Gauge Whether Shuttle Launches

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By MARCIA DUNN, The Associated Press

Published: December 9, 2007

CAPE CANAVERAL - With fuel gauges still a possible threat, NASA aimed for a launch today of space shuttle Atlantis after senior managers signed off on a plan to tighten flight rules and shoot for a slim one-minute window.

Managers think the extra precautions will keep Atlantis and its seven-man crew as safe as possible if the shuttle lifts off with a European lab intended for the International Space Station.

Under the new rules, NASA will proceed with the countdown only if all four of the gauges in Atlantis' big hydrogen tank are working properly.

Two failed when the shuttle's tank was filled for liftoff Thursday and a third subsequently acted up.

NASA passed up launch tries on Friday and Saturday because of the perplexing problem, which has plagued the shuttle program off and on for more than two years. After meeting again Saturday, shuttle managers decided to press ahead with an afternoon liftoff today, but only if all the fuel gauges behave.

The fuel gauges, or engine cutoff sensors, are in a critical backup system for preventing the shuttle's main engines from running too long in the climb to orbit.

If the engines kept running and the fuel tank was empty because of a leak or unexpected trouble, they could ignite or explode.

Last year, after struggling with the problem, NASA loosened its launch rules to require only three of the four fuel gauges to be working before liftoff.

Managers went back to the four-of-four rule Saturday after concluding that Atlantis' system was suspect and that it would be too risky to attempt a launch without every gauge functioning.

NASA also decided to shorten the five-minute launch window to a single minute to put Atlantis on a more direct path to the space station and keep more fuel in the tank, in case of sensor trouble. New instrumentation for monitoring the condition of the fuel gauges will be used in the flight.

The plan was put forth by the astronauts.

Packed aboard Atlantis is the European Space Agency's $2 billion science laboratory, Columbus. It will be the second lab added to the space station; Japan's Kibo lab, or Hope, will follow on successive shuttle flights next year.

Columbus has been waiting to fly for years. It was stalled first by NASA space station design problems, then by Russian space station holdups, then by the Columbia tragedy in 2003, which grounded all shuttle flights for 2 1/2 years.

NASA is up against a tight deadline for launching Atlantis in December. If the shuttle isn't flying by Thursday or possibly Friday, the mission will have to wait until January because of unfavorable sun angles and computer concerns.

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