CAPE CANAVERAL, Fla. — NASA on Tuesday postponed next month's launch of space shuttle Atlantis after a hail storm left hundreds of small dents on the spacecraft's external fuel tank and on a wing.
The launch, which had been set for March 15, was pushed back to at least late April to give NASA time to make repairs.
NASA technicians planned to move the orbiter back to a giant hangar to examine the damage and decide if repairs can be made at the Kennedy Space Center.
"This constitutes, in our evaluation, the worst damage we have ever seen of hail on the external tank," said Wayne Hale, manager of the space shuttle program.
The need to make repairs had raised the likelihood that the launch would be delayed since NASA only had four extra days to spare in its launch-preparation schedule.
The damage was concentrated in the upper third of the 153-foot-tall external tank, a section which holds liquid oxygen propellant.
During their 11 days in space, Atlantis' astronauts must deliver a 35,000-pound addition to the international space station, the heaviest ever, along with a new pair of solar arrays. Crew members are also supposed to unfurl the solar arrays, fold up an old pair and conduct at least three spacewalks.
Monday evening's thunderstorms moved quickly and had winds of up to 60 miles per hour. The size of the hail was between a half inch and two inches and landed only at the NASA space center. The National Weather Service considers three-quarters-of-an-inch-sized hail to be "severe," said David Sharp, a meteorologist with the weather service.
"Most people didn't see thunderstorms, let alone severe thunderstorms," Sharp said. "It only occurred in one location, and that was NASA's Kennedy Space Center complex."
In 1999, hail from a storm made 650 divots in space shuttle Discovery's external tank, forcing NASA to delay a launch and return the spacecraft to the Vehicle Assembly Building. In 1995, space shuttle Discovery was sent back to the Vehicle Assembly Building because of fuel-tank damage caused by a pair of woodpeckers that drilled about 200 holes in the rust-colored foam insulation, apparently in an attempt to roost and build nests.
Hail also hit the external tank of space shuttle Atlantis in 1990, causing minor damage.
The insulating foam on the external tank is of special concern to NASA since foam flew off space shuttle Columbia during lift off in 2003 and struck the orbiter. The damage allowed fiery gases to penetrate Columbia during re-entry, breaking up the craft and killing its seven astronauts.
NASA redesigned the external tank, removing large amounts of foam, before last year's three successful shuttle missions. The space agency plans another design change to the tank before the shuttle program ends in 2010.
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