By Michael Cabbage,The Orlando Sentinel

CAPE CANAVERAL, Fla. – Space shuttle Discovery’s liftoff is on track for July, NASA managers announced Wednesday after deciding the hazard posed by foam shed from the ship’s redesigned fuel tank was “an acceptable risk.”

Shuttle officials concluded during two days of deliberations at the Kennedy Space Center that foam insulation still will break loose from the tank’s exterior during launch, but the debris likely will be too small to cause serious damage. However, one unchanged part of the tank continues to cause worry.

“There will continue to be foam coming off the external tank,” said Wayne Hale, NASA’s shuttle program manager. “What we have done in a very systematic manner is eliminate the largest hazards.”

The debris review was ordered in the wake of Discovery’s flight last July.

During launch, the tank shed more than a dozen large pieces of debris, including a one-pound piece of a foam ramp that narrowly missed hitting the spaceship. The mission was the first to test a two-year redesign of the tank that was ordered after a debris strike caused the Columbia accident in 2003.

The large ramp that lost foam during Discovery’s launch has been removed. However, concern remains about 34 smaller foam ramps that prevent ice from building up on brackets used to attach fuel-pressurization lines and a tray of electrical cables to the tank’s exterior. Some engineers are worried that in a worst-case scenario, matchbox-sized pieces of foam weighing up to 3 ounces could break off and cause critical damage.

A redesign of the ramps is under way and engineers considered modifying them before Discovery’s launch. But wind tunnel tests showed that new, pared-down versions of the ramps lost more foam than the current design.

Shuttle managers opted to postpone changes to the smaller ramps until the impact of the larger ramp’s removal can be studied after Discovery’s launch. A redesign of the small ramps remains two or three flights away.

“We think they are a hazard,” Hale said. “They are an area of foam insulation that we very definitely need to deal with. But the principle that we have to remember, however, is that in a flight test you want to make one major change at a time.”

Wednesday’s decision helps clear the path for the shuttle to lift off during a launch window extending from July 1-19. Additional work examining the aerodynamic effect of design changes to the tank is expected to be completed before Discovery’s Flight Readiness Review on June 16.

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