CAPE CANAVERAL, Fla. - NASA fueled Discovery's external tank this morning in a bid to troubleshoot problems with critical engine sensors and valves.
The shuttle launch team began the three-hour fueling operation around 5:30 a.m. By late morning, engineers were studying data and inspectors clad in orange coveralls were scouring the launch pad.
Preliminary results are expected late this afternoon after more than 500,000 gallons of supercold propellants (liquid oxygen and liquid hydrogen) are drained from the 15-story tall orange fuel tank.
"From first look, we're having a very good experience with the tanking test," NASA Administrator Michael Griffin said this morning during a visit to the Kennedy Space Center.
The shuttle team took advantage of the fueling test to get another look at how and where ice forms on the tank in addition to how the redesigned foam insulation performs in general. The ice and debris inspection team remained at the pad until almost noon, searching for dangerous ice build-up or other problems.
However, the primary reason for doing a second tanking test was to figure out a problem that cropped up during a similar test in April.
During that test, sensors that serve as fuel gauges and a pressure-relief valve failed to operate properly. The sensors produced an intermittent stream of data, and the valve opened and shut more than expected.
Engineers want to pinpoint the causes and fix them before launching the agency's first mission since the 2003 Columbia accident. The flight is set to lift off between July 13 and July 31.
The fuel-depletion sensors constantly measure the amount of propellant left in the 15-story tank as the shuttle makes its nine-minute climb to orbit.
The relief valve keeps pressures within the tank at proper levels during fuel-loading operations and flight.
NASA plans to move Discovery from launch pad 39B to the KSC Vehicle Assembly Building as early as Tuesday so the ship can be outfitted with a new external tank equipped with a fuel pipeline heater.
Managers decided to make that move after dangerous amounts of ice built up around the 70-foot pipeline on the outside of Discovery's tank during last month's fuel-loading test.
NASA feared ice could break off during launch and damage the shuttle's fragile thermal tiles and wing panels.
Serious damage to a wing panel doomed Columbia and its seven astronauts as re-entered Earth's atmosphere in a landing attempt on Feb. 1, 2003.
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