Shuttle Discovery's 15-story external tank is about half-full of supercold propellants as NASA presses ahead with a test aimed at pinpointing the cause of cracks in its aluminum-lithium hull.
The three-hour fuel-loading operation began on time at 7 a.m. as engineers first chilled down insulated lines that route liquid hydrogen and liquid oxygen from storage farms on either side of the shuttle launch tower to the external tank. Then engineers began slowly flowing propellant into separate liquid hydrogen and liquid oxygen vessels within the tank before transitioning to a fast-fill phase around 7:50 a.m.
Alicia Mendoza, the NASA external tank/solid rocket booster manager at Kennedy Space Center, said she expects the propellant-loading part of the test to be complete on time around 10 a.m. You can watch live NASA TV coverage right here in The Flame Trench. Click the NASA TV box on the right side of the page to launch our NASA TV viewer.
The tank is outfitted with 39 strain gauges and 50 thermocouples that are being used to gather data on the contraction and expansion of the aluminum-lithium hull as well as temperatures as the tank is filled and subsequently drained.
The data will help engineers determine the cause of cracks in beams that provide structural integrity to the ribbed mid-section of the tank -- an area that links the lower liquid hydrogen and upper liquid oxygen vessels witin the tank.
Four cracks were found in two of the 21-foot-long braces after a scrubbed Nov. 5 launch attempt. A significant leak of gaseous hydrogen from an attachment plate that links a hydrogen vent line to the tank caused the scrub. The ongoing tanking test will enable engineers to determine whether repairs to that plate fixed the problem.
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