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Space shuttle Discovery sits on launch pad 39B at the Kennedy Space Center in Cape Canaveral, Fla.
Mark Wilson/Getty Images
Enlarge image to read about the main changes designed to make Discovery safer during launch and in-flight.
CAPE CANAVERAL, Fla. (AP) - Thunderstorms forced NASA to call off Saturday's launch of Discovery, delaying the first space shuttle flight in a year by a day.
More bad weather was forecast for Sunday and for the rest of the Independence Day weekend.
As storm clouds moved in and out of the launch zone throughout the nine-minute mark, it became clear the weather would not improve, and launch director Mike Leinbach announced a one-day delay.
"We're not going to make it today," Leinbach said. "It's not a good day to launch the shuttle. So we're going to try again tomorrow."
The seven astronauts aboard the fueled spaceship immediately began backing out of their launch procedures. "It wasn't our time today, and we'll launch when we're ready and hopefully, tomorrow will look better," shuttle commander Steven Lindsey replied.
NASA had just five minutes to launch the shuttle Saturday because of the need to intercept the international space station in orbit. The next launch attempt was scheduled for 3:26 p.m. EDT Sunday.
The delay was a disappointment for NASA, which last flew the shuttle in July 2005 and was eager to get flights to the international space station back on track. Among the space agency's guests at the launch were Vice President Cheney and several members of Congress.
The only technical problem that popped up during the countdown Saturday was a failed heater for one of Discovery's thrusters, needed to keep the fuel from freezing. Mission managers decided to proceed with the launch, since the thruster was not needed during liftoff, and work around the problem in orbit.
As it has since the Columbia disaster, the overriding concern remained the foam insulation on the external fuel tank.
NASA Administrator Michael Griffin decided to proceed with the 12-day mission despite the concerns of two top agency managers who wanted additional foam repairs.
Bryan O'Connor, the top safety officer, and chief engineer Christopher Scolese recommended at a flight readiness review meeting two weeks ago that the shuttle remain grounded until design changes are made to 34 areas on the fuel tank known as ice-frost ramps. These wedge-shaped pieces of foam insulate brackets on the tank that hold long pressurization lines in place. The intent is to keep ice or frost from forming on these metal brackets once the tank is filled with super-cold fuel.
"We now have a NASA in which senior officials feel free to discuss and debate openly complex, difficult and subtle technical topics that affect the flight," Griffin told The Associated Press on Saturday morning. "No matter what decision I made, I would have been disappointing somebody."
Griffin noted that the foam is important -- "shame on us that we didn't realize it before" the Columbia tragedy. But he stressed that it is hardly the only thing that poses a flight risk.
If foam came off and struck Discovery, causing serious damage, the seven astronauts could move into the space station and await a rescue by shuttle Atlantis. But that would be risky, too, and something NASA would try to avoid if at all possible.