NASA postpones shuttle launch a second time
Safety concerns prompt officials to nix recently announced plans for May 22 launch.
NASA said Thursday that engineers have uncovered new safety concerns with the space shuttle's heat shield and fuel system, problems that will keep the shuttle Discovery from launching as planned next month.
Discovery had been poised for a May 22 liftoff with seven astronauts on the first space shuttle mission in more than two years. The flight has been rescheduled for no earlier than July 13. Discovery will be removed from its launch pad and returned to a hangar for repairs.
It is the second postponement since April 21, when NASA announced it needed an extra week to finish what it characterized as mostly paperwork on several safety modifications made in the aftermath of the Columbia disaster.
"We're not going to rush to launch. We want to be right," NASA Administrator Michael Griffin told reporters in his second news conference since taking the helm of the space agency three weeks ago.
NASA's progress implementing return-to-flight requirements set out by the Columbia Accident Investigation Board was in question long before Griffin was appointed to the post.
Griffin said senior managers brought a postponement recommendation to him late Thursday. They had spent the day deliberating the results of two days of technical reviews that concluded Wednesday at Johnson Space Center in Houston, Texas.
The NASA chief said two safety organizations established to comply with accident board requirements--the Independent Technical Authority in Washington and the Engineering and Safety Center in Hampton, Va.--were influential in the decision to postpone. "Those organizations empowered people to speak up, and I think they have, and we've heard them," he said.
The new concerns center on the results of a fueling test at the Florida launch site April 14 and on continuing analysis of debris hazards posed to the shuttle's heat shield.
The fueling test was designed to uncover any technical problems lurking at the launch pad, which last was used in October 2002. Engineers pumped 528,000 gallons of liquid hydrogen and oxygen into Discovery's external fuel tank. They noticed a pressurization problem with the tank and the failure of two of four sensors that are supposed to indicate when the tank is empty or full.
The repair work likely will include adding a heater in a spot on the fuel tank where ice tends to form once the tank is filled with cryogenic propellants. Shuttle program managers say the ice poses a danger to the shuttle and its crew.
Because a debris strike to Columbia's delicate heat shield was responsible for the shuttle's fatal breakup in February 2003, much of NASA's recovery effort has focused on eliminating sources of debris. NASA's top priority was the main debris source, the fuel tank, which it redesigned to greatly reduce chances of foam insulation breaking loose and hitting the orbiter.
Mitigating ice buildup on the tank has been a more difficult task, because NASA has no control over weather conditions that can affect the density and thickness of ice. Engineers thought they had the problem under control. But Wayne Hale, deputy shuttle program manager, told reporters they were surprised recently when a "shake test" at the Army's Redstone Arsenal in Huntsville, Ala., liberated a 20-cubic-inch chunk of ice from a mocked-up section of shuttle fuel pipe.