CAPE CANAVERAL - Discovery's heat-shield tiles sustained significantly less damage during NASA's second post-Columbia test flight, a sign that the agency is starting to get a deadly foam-shedding problem under control, a NASA official said.
During post-landing inspections, engineers noted a drop of about 33 percent in the number of damage spots on heat shield tiles on the belly of the orbiter.
There also was almost a 50 percent decrease in the number of hits greater than one inch - defects more susceptible to sustaining further damage when exposed to extreme temperatures during atmospheric reentry.
"The vehicle looked very good," Thomas Ford, a member of NASA's ice-debris inspection team at Kennedy Space Center, said Wednesday. "It's definitely gratifying."
Columbia and seven astronauts were lost on re-entry in February 2003 when hot gases surged into the orbiter through a hole created when its heat shield was struck by a 1.67-pound piece of external tank foam insulation about 82 seconds into flight.
Since then, NASA engineers have modified the tank to try to prevent chunks of foam large enough to cause severe damage from breaking free at critical times during launch.
Ford said 96 hits were tallied on the underside of Discovery after its July 17 landing. In comparison, 152 strikes were found on the shuttle's belly after NASA's first post-Columbia flight last summer.
Only 11 strikes larger than one inch were found on Discovery during inspections conducted on Kennedy Space Center's three-mile runway earlier this month. Inspectors found 21 after last summer's flight.
The drop is a sign that safety modifications meant to prevent the shedding of large foam chunks are working, Ford said. NASA engineers still are working on other design changes that should reduce the problem even further.
"Do we have a handle on it? Yes. Is it still a problem? Yes," the Merritt Island resident said. "But we're getting better at it."
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