LIVE IMAGES: The images above are from live video feeds in the Launch Complex 39 area at Kennedy Space Center, where shuttle Endeavour is being readied for a critical fuel-loading test. They will automatically refresh to the most up-to-the-minute image every 30 seconds.
About 40 minutes into this morning's fuel-loading test, liquid hydrogen is being "fast filled" into space shuttle Endeavour's external tank at Kennedy Space Center's launch pad 39A.
More than 390,000 gallons of the fuel will be loaded into a tank that sits at the bottom of the 15-story tank. Another 145,000 gallons of liquid oxygen will fill an upper tank.
The propellants are loaded at a rate of 1,035 gallons per second - fast enough to to fill a medium-sized backyard swimming pool every 18 seconds, according to external tank manufacturer Lockheed Martin Corp.
More tank trivia: it's 154 feet tall and 27.6 feet in diameter. It weighs about 58,000 pounds when empty, but holds 1.6 million pounds of propellant.
NASA expects to know after 9 a.m. whether it has succeeded in loading the liquid hydrogen without springing a leak of hydrogen gas.
That problem scrubbed two launch attempts in June, and must be fixed if Endeavour is to lift off on its new targeted date of July 11.
Some of the extremely cold liquid hydrogen boils off during the fueling process, and a seven-inch vent line routes excess vapor out of the tank to make sure proper pressure is maintained.
Too much gas leaked from the vent line, which engineers determined was connected to a plate on the fuel tank that was slightly misaligned.
NASA has replaced a seal and taken steps to eliminate movement in the line to try to correct for the misalignment.
The leaks have cropped up when the tank was nearly full, a stage that is more than an hour away.
So far, no problems are reported with the fuel-loading test that started at at 7 a.m.
You can follow live coverage of the test by clicking on the NASA TV still images above and on the right side of this page to launch a viewer.
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