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NASA: Shuttle on track for July launch

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NASA is preparing to launch the space shuttle Discovery sometime in July.

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National Aeronautics and Space Administration (NASA)
Space Programs
Marshall Space Flight Center

(CNN) -- NASA is on track to launch the space shuttle Discovery in July after analysis of wind tunnel tests determined that the external fuel tank was safe, NASA Administrator Michael Griffin said Friday.

The decision clears the way for a mission sometime between July 1 and July 19.

Despite concerns about the potential for insulating foam loss from structures on the external tank called ice-frost ramps, program managers and space agency engineers decided to leave them in place for the next launch.

"At the end of the day, the decision going forward was to fly, leaving these ice-frost ramps as is," said Shuttle Program Manager Wayne Hale.

Foam shedding has been a problem for NASA, beginning with the loss of the shuttle Columbia in 2003.

The orange external fuel tank is covered in insulating foam to keep ice from forming on the tank when super-cold liquid hydrogen and oxygen propellant are pumped into it in hours before launch. The foam goes on like shaving cream and becomes brittle when it dries.

An accident investigation board concluded that a 1.6-pound piece of the foam broke loose from Columbia's external tank during the 2003 launch, cracking a hole in the wing that eventually led to the destruction of that spacecraft and the deaths of the seven astronauts onboard.

Last summer, a one-pound piece of foam broke loose from Discovery's external tank on NASA's return-to-flight mission, just missing the orbiter.

After that close call, NASA engineers determined that the piece of foam that nearly hit Discovery was from a 40-pound wedge of insulation called the PAL ramp. They said that piece would have to be removed before the shuttle could fly again.

Managers commissioned wind tunnel tests to make sure the change would not adversely affect the shuttle's aerodynamics on its supersonic trip from the launch pad to orbit.

In those tests, engineers have focused on two foam features: the large PAL ramp, which smoothes the flow of air over pressurization lines and a cable tray that runs along the side of the external tank, and the smaller ice-frost ramps, which cover the brackets that hold those structures in place.

Small pieces of ice-frost ramp foam have shed from external tanks on past missions.

At a meeting Thursday at Marshall Space Flight Center in Huntsville, Alabama, NASA officials, shuttle program managers and engineers met to discuss the results of the tests and analysis of the data.

In the end, they decided that the next mission will fly using an external tank without a PAL ramp, and modifications to the ice-frost ramps will be considered on subsequent missions.

"It is more appropriate to make one change at a time, to take care of the biggest problem that we have, and then work our way to the next situation that we'd like to improve," Hale said.

"When you make a major change, you should fly that major change without other major changes, to see how it performed. And then if you have subsequent changes to be made, you make those in subsequent flights."

But Hale acknowledged that flying the next mission with the ice-frost ramps does pose some risk.

"The worst case, if it came off with the maximum mass ... and [it] comes off at the worst time, and follows the worst possible trajectory to the most vulnerable part of the orbiter, it would not be what we would like to have," he said. "I don't know how to characterize it more than that. It would cause what we call critical damage."

Hale stressed that modifications to the shuttle's external tank likely will be ongoing for the remainder of the program's life.

NASA officials intend to retire the shuttle fleet in 2010 after the space agency completes assembly of the international space station.

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