CAPE CANAVERAL, Fla. – NASA chief Michael Griffin is taking a calculated gamble by going ahead with the launch of Discovery, overruling two top managers who fear foam flying off the fuel tank might harm the space shuttle.
The world will soon know if his gamble pays off.
Discovery was scheduled to blast off from the Kennedy Space Center at 3:49 p.m. EDT Saturday, the first launch of a space shuttle in almost a year and only the second since the Columbia disaster in 2003.
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Storm clouds forecast for Saturday afternoon remained the chief obstacle to launch.
The seven astronauts say they are confident of Griffin's decision to go ahead, but hardly any astronaut ever publicly expresses fears before a launch.
"I believe we'll be as safe as we were on my other flights," said Steve Lindsey, Discovery's commander, who has flown on three previous shuttle missions. "I haven't really seen a decision made that I didn't agree with."
Faced with a 2010 deadline to finish building the international space station and end the shuttle program, Griffin wants to get the shuttles flying again and believes a delay now would create scheduling pressure toward the end of the decade.
He has acknowledged, though, that he would likely shut down the shuttle program if there is another vehicle lost like Columbia or Challenger.
"Looking at the whole picture, I'm willing to take a little bit of programatic risk now — notice I did not say crew risk ... in order to prevent an excessive build-up of programatic risk later on," Griffin said recently. "This is, in fact, what they pay me to do."
The board that investigated the Columbia accident faulted NASA three years ago for placing schedule concerns ahead of safety, squelching dissent and steamrolling over the concerns of engineers who worried that foam from the huge external fuel tank had hit Columbia.
Fiery gases were able to penetrate the wing where the foam knocked a hole, causing the shuttle to disintegrate. All seven astronauts were killed.
This time around, NASA has aired its internal dissent publicly.
Bryan O'Connor, the space agency's chief safety officer, and chief engineer Christopher Scolese recommended at a meeting two weeks ago that the shuttle not fly until further design changes were made to 34 areas on the fuel tank known as ice-frost ramps.
These wedge-shaped brackets run up and down the tank holding in place pressurization lines. Foam insulation is used to prevent ice from building up on the tank when it is filled with supercold fuel. Small pieces of foam have snapped off during previous launches.
At the meeting, Scolese wrote in a report that he signed, "I remain no-go based upon the potential loss of the vehicle."
NASA has refused Freedom of Information Act requests from The Associated Press, Florida Today and perhaps other news organizations for recordings of the meeting, even though the agency released the same information last year.
NASA engineers redesigned the external fuel tank after the Columbia accident, and again after a 1-pound piece of foam insulation came off the tank during the launch of Discovery last summer.
In the most recent change, more than 35 pounds of foam have been removed in what NASA describes as the biggest aerodynamic change ever made to the shuttle's launch system.
NASA tried other design changes to the ice-frost ramps, such as removing foam, but they didn't hold up well in wind tunnel tests.
O'Connor and Scolese agreed with Griffin's rationale that the risk was only to the shuttle and not the crew, since the astronauts could take refuge in the international space station until a rescue vehicle is sent up. They did not appeal Griffin's decision.
"It's clearly a risk. Mike knows it's a risk," said John Logsdon, director of the Space Policy Institute at George Washington University, who served on the board that investigated the Columbia accident. "What's good about this process is the people who think the risk is too great had their case fully heard with ... I believe, a prudent judgment to its outcome."
NASA managers concede some foam will fall off the tank, but they don't think the pieces will be large enough to cause damage.
"There will always be a risk associated with human spaceflight," Douglas Osheroff, a Stanford physics professor who served on the Columbia Accident Investigation Board, said in an e-mail. "I am not so concerned about the ice-frost ramps, assuming that NASA has done its homework."
Discovery's seven-member crew will test shuttle inspection and repair techniques, bring supplies and equipment to the international space station and deliver the European Space Agency's Thomas Reiter for a six-month stay aboard the orbiting outpost.
Astronauts Piers Sellers and Mike Fossum will make two spacewalks and possibly a third, which would add a day to what is planned to be a 12-day mission.
Astronaut colleagues of the Discovery crew say it makes sense to launch the shuttle now to see how it flies with the current changes to the tank.
"What we don't want to do is smash-down too far on one side where we're so interested in listening to everybody's point of view and doing more testing that we actually don't launch again," said astronaut Pam Melroy, who will become the second female commander of a space shuttle next year. "We also don't want to go too far the other way, where we say 'Shut up everybody. We're going to go fly!'"