For NASA, Misjudgments Led to Latest Shuttle Woes

From The New York Times:

"We are ready to fly."

It was June 24, and William W. Parsons, NASA's shuttle program manager, was speaking to reporters on a telephone conference call from the Kennedy Space Center at Cape Canaveral, Fla. Two and a half years of study and struggle, he told them, were over at long last. The shuttle Discovery could blast off in July.

At a closed-door meeting that afternoon, senior shuttle managers had ruled that the chances that debris from the giant external fuel tank would strike the Discovery at liftoff - in the kind of accident that doomed the Columbia and its seven astronauts in February 2003 - had been reduced to "acceptable levels."

The possibility that a large chunk of insulating foam might break away from a section of the tank called the protuberance air load ramp - PAL for short - never came up. It had been ruled out months earlier, checked off on a long list of items no longer worthy of urgent action.

Last Tuesday morning, NASA's contention that it had produced the safest fuel tank in shuttle history was shattered two minutes into the Discovery's mission to the International Space Station...