Wednesday, December 15, 2010

Countdown to Friday tanking test expected to start tonight

Kennedy Space Center teams are expected to be called to Launch Control Center stations at 8:30 p.m. today to begin a countdown to a Friday morning tanking test on shuttle Discovery.

Overcoming extreme cold conditions, crews late Tuesday finished applying insulating foam to the tank's mid-section, where roughly 90 strain gauges and temperature sensors have been wired.

Fueling of the tank with more than a half-million gallons of liquid hydrogen and liquid oxygen is expected to begin at 7 a.m. Friday. NASA TV will provide live commentary.

Countdown clocks will begin ticking down from the T minus 33-hour mark, marching through five planned holds and following the same procedures as before a launch attempt.

The rotating gantry at launch pad 39A will be retracted Thursday evening to reveal Discovery.

The test is part of a weeks-long investigation into cracks found last month on two external tank support brackets called "stringers." Engineers suspect stresses during the loading of supercold propellants may have caused the cracks.

The test will also show if repairs to a hydrogen gas vent line attached to the tank have been successful. A hydrogen leak scrubbed Discovery's last launch attempt Nov. 5.

IMAGE: Space shuttle Discovery's external fuel tank is outfitted with approximately 89 strain gauges, thermocouples and wiring in preparation for a tanking test no earlier than Dec. 17 on Launch Pad 39A at Kennedy Space Center. Credit: NASA/Jim Grossmann

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