Shuttle tank foam damaged before launch

CAPE CANAVERAL, Fla., March 11 (UPI) -- Foam insulation on shuttle Columbia's external fuel tank had been damaged and repaired prior to launch, the team tasked to find the cause of the spaceship's demise said Tuesday.

The problem report generated by Kennedy Space Center workers is among the thousands of documents and other records being scrutinized in an attempt to understand why the orbiter did not survive its re-entry into Earth's atmosphere on Feb. 1 after a 16-day research mission. Seven astronauts died in NASA's worst accident since the 1986 Challenger explosion.

The damaged insulation is of particular interest since the problem was reported in an area that shed debris during launch. Three pieces all coming from the tank's bipod area on the left side struck the leading edge of Columbia's left wing.

The investigators have determined that a breach somewhere in the left wing allowed hot gases to enter the structure, dooming the ship and its crew. The panel has not yet determined the exact location of the breach, nor if the debris impact during launch contributed to or caused the accident.

"What we're really looking at is a complex failure of a complex system," said Harold Gehman, a retired Navy admiral who chairs the Columbia Accident Investigation Board.

"It's possible that the foam striking a healthy orbiter would not have done enough damage to cause the loss of this orbiter. But it's possible that foam striking an unhealthy orbiter, (one) that had problems in it either due to stresses on launch, too much heating in transitions (in and out of the atmosphere) years before, aging ... or a whole number of other complex issues ... that you could do some damage ... that is the result of a normal event, which (Columbia) could have survived at age 10, maybe she couldn't survive it at age 21."

The investigation board also is studying unusually high wind shear stresses on the ship's left side during its launch on Jan. 16. Board member John Barry said a similar incident occurred during a previous launch of Columbia on an identical trajectory -- 39 degrees relative to the equator -- and with an identical external fuel tank.

NASA has two kinds of fuel tanks in use: a lightweight tank and a newer superlightweight version. Columbia used one of the two remaining lightweight tanks on what turned out to be its final mission. The shuttle had been flying since 1981 and was returning from its 29th spaceflight when it was destroyed.

The falling foam insulation was recorded by ground-based video cameras and detected the day after Columbia reached orbit. Although the board has not positively determined the foam played a role in Columbia's demise, NASA officials said the agency will change the way the foam is manufactured, processed and/or applied to make sure it stays on the tank during launch.

Engineers studying the video of the debris hit determined it would not pose a flight risk for Columbia. However, if the foam also contained heavier ice or part of its underlying ablative material -- which is designed to provide insulation by decomposing as it burns away -- the engineering analysis may not have been accurate. NASA plans to design a foam that does not use an ablative, Barry said.

Meanwhile, about 4,000 people per day are continuing to comb Texas and Louisiana for wreckage from the accident, Gehman said. As of Monday night, 28,286 pieces of debris had been logged at the Kennedy Space Center, where a hangar has been turned over for reconstruction and storage of the shuttle.

The board also has ordered wind tunnel tests to determine how much damage the ship would have had to account for the automated jet firings, body flap movements and other aerodynamic adjustments, each of which was radioed to ground control teams up until loss of contact with the ship at about 9 a.m. EST. Preliminary findings indicate the shuttle would have had to shed more than one of its leading carbon-carbon reinforced leading edge wing shields to account for the ship's responses.

A newly released timeline of the shuttle's final moments indicates a master alarm was going off and the ship was banking sharply and uncontrollably to the left. In addition, the commander or the pilot may have tried to take over manual control of the shuttle. Another possibility is that the flight stick was inadvertently bumped, or the data are erroneous.