Kennedy Space Center, Florida (CNN) -- The final launch of the space shuttle Endeavour was delayed Friday, temporarily putting off what promised to be an emotional moment for the mission's commander. Liftoff -- originally scheduled for 3:47 p.m. ET -- was delayed by at least 72 hours due to concerns with the shuttle's heating system. As part of NASA's examination of the problem, the shuttle's external fuel tank will be drained of its oxygen and hydrogen propellants. "The engineering team did not understand how this problem occurred and did not feel comfortable proceeding with a launch attempt," NASA spokesman George Diller said.
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NEW: Giffords expresses disappointment at delay in launch
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Endeavour's final mission has been delayed by 72 hours
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U.S. Rep. Gabrielle Giffords was scheduled to watch her husband's shuttle launch
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The shuttle will carry a $1.5 billion device to capture space particles
"I think all of us, with all the changes that are going on, with our country's space program and @placeholder, all of us professional astronauts are looking into our hearts to see what we're going to do next," Fincke said.