Discovery take off today despite snag

The countdown continues for a scheduled Tuesday launch of the Space Shuttle Discovery, as programme managers said they would be willing to b...

The countdown continues for a scheduled Tuesday launch of the Space Shuttle Discovery, as programme managers said they would be willing to blast off even if a balky fuel sensor fails again.

But National Aeronautics and Space Administration (NASA) officials admitted the choice to go ahead despite an unexplained glitch in the shuttle electronics could appear questionable since the agency is still trying to shed an image of sloppiness after the loss of the Space Shuttle Columbia more than two years ago. ‘‘I wake up every day and ask myself, ‘Are we pushing too hard?’’’ Wayne Hale, the deputy shuttle programme manager, said at a news briefing at Kennedy Space Center in Florida. ‘‘We are still struggling with the ghosts of Columbia.’’ NASA administrator Michael Griffin denied the agency was suffering from launch fever. ‘‘We’re trying to make reasoned judgments,’’ he said.

Columbia’s seven astronauts died in 2003 when the orbiter broke up while attempting a landing at the space centre. An investigatory panel later said the accident was caused by a piece of lightweight foam that fell off the external fuel tank and struck the left wing. The panel also cited a NASA culture that, among other things, was preoccupied with meeting launch schedules.

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Discovery, the first launch since the Columbia tragedy, was originally scheduled to lift off July 13. But a faulty sensor in the liquid hydrogen portion of the fuel tank caused the launch to be deferred.

After testing hundreds of possibilities in the ‘‘fault-tree’’ between the sensors and the orbiter’s computer, investigators have narrowed the cause to either a problem with the sensor or wiring in the point sensor box, that receives signals from the sensors at the bottom of the fuel tank.

There is also some concern that changes made to the fuel tank after Columbia, including the addition of heaters on the surface to prevent the formation of ice, could be causing electromagnetic interference that is short-circuiting the sensor.