Kennedy Space Center, Florida - Despite objections from two senior NASA officials, the space agency is moving ahead with plans for a Saturday launch.

Michael Griffin, NASA Administrator

“the agency's top safety official and nasa's chief engineer are worried that foam could break-off from brackets securing pressurization lines and damage the shuttle's heat shield. ”

 In their analysis, the officials say that type of failure is "probable/catastrophic." Meaning it is probable that sometime in the final 17 flights, foam will be shed with "catastrophic results."   As you'll recall a large piece of foam doomed columbia in 2003.

And another large piece.. just missed Discovery when it took off last July. But NASA administrator Michael Griffin says this time there is no risk to the crew saying only small pieces of foam can brake off the brackets.

Michael Griffin, NASA Administrator

“if we're going to fly, we need to accept some programmatic risk and get on with it. the reason for the objections... concern over possible shuttle damage from foam loss. so the question is, can we fly a few times with this ice frost ramp without incurring a hazard and based on the data we've seen, I believe we can."”

And even if the shuttle is a hit... Griffin says camera and sensors will spot the damage and if the astronauts can't repair it.  The crew will be sent to the space station and wait for the shuttle atlantis to bring them back.

But Griffin also knows another catastrophe would bring an end to the shuttle program.

Michael Griffin, NASA Administrator

“if we were to lose another vehicle, i would be moving to shut the program down.."”