The space agency concluded that damage from such breakaway foam did not threaten shuttle safety and determined the fuel tank attached to Endeavour was "safe to fly with no new concerns and no added risk," according to newly released documents from the
National Aeronautics and Space Administration.
The documents revealed for the first time some of NASA's reasons for deciding months ago that such risks were insufficient to delay shuttle launches, even as agency officials already were looking into what they perceived as a frustrating, recurring problem.
The findings were included in more than 1,000 pages of internal reports NASA released late Thursday about the most recent shuttle missions.
Investigators believe insulating foam that struck Columbia's left wing on liftoff peeled away from the same region of the external fuel tank, called its bipod ramp. That may have damaged delicate protective tiles on the wing and allowed superheated air to fatally penetrate the spacecraft during its fiery re-entry on Feb. 1.
The bipod is a V-shaped structure connecting Columbia near its nose landing gear to the orange-colored external fuel tank. Metal attachments on the tank are covered with ramp-shaped insulating foam that protrudes noticeably from the tank's surface.
Tank specialists at NASA identified the foam problem on Oct. 31, 2002, as their only "special topic" of concern prior to the liftoff of Endeavour on Nov. 23, the shuttle flight immediately preceding Columbia's. They cited troubling reports on three earlier missions of foam breaking away from the tank's bipod ramp.
But they defended NASA's work, saying the foam was applied with proven craftsmanship by "experienced practitioners" with 20 years of such work. They also noted that the process of applying foam to that part of the tank had not changed since 1993.
Moreover, they said, there were only a handful of previous foam problems near the bipod area on more than 100 fuel tanks that had flown into space. The risk of foam breaking off that area was "no higher/no lower" than previous flights, they concluded.
NASA has said previously it was aware of four flights since 1983 where foam broke off that part of shuttle fuel tanks, most recently on a 10-day mission to the International Space Station by Atlantis that began Oct. 7, 2002. That flight immediately preceeded
Endeavor's, when the foam problem was flagged by NASA tank experts as their singular concern.
"We knew we needed to understand it prior to the next flight," Ron Dittemore, the shuttle program manager, said at a news conference last month. "So we were already aggressively on a path that was going to try and help us understand whether or not that represented any concern to us."
By Ted Bridis