Star-Ledger February 4, 2003
The signs of a slowly building catastrophe: Reports of tiles falling west of Texas would give NASA a clearer picture
By KEVIN COUGHLIN AND KITTA MacPHERSON
Star-Ledger Staff
Somewhere in the Southwest, a few small tiles could hold the key to knowing what doomed the space shuttle Columbia.
NASA officials said yesterday they were searching for the "missing link"-- and that could be tiles measuring just 6 inches square that witnesses claim fell from the shuttle as it streaked over California, Arizona and New Mexico before breaking apart above Texas.
And, reversing prior statements, investigators last night characterized a pillow-size piece of insulation that struck Columbia's wing at liftoff as the most likely cause of the calamity.
But, they said, they still lacked crucial information to fully explain what heated the space vessel before its catastrophic breakup Saturday morning.
"There's some other event, there's some other missing link that we don't have yet that is contributing to this temperature increase, and we have to go find that," said Ron Dittemore, the shuttle program manager.
NASA hopes tiles found from the left wing would provide answers.
The space agency is performing computer calculations to guess where the shuttle's heat-insulating tiles fell. Each tile bears a code, and investigators aim to match up any recovered tile with its location on the spacecraft by the code. That is, if the code is recognizable after a disaster that occurred nearly 40 miles up while the craft was traveling nearly 3 1/2 miles per second, and if the tiles can be located over thousands of square miles of widely varied terrain.
Discovery of debris near Fort Worth, Texas -- to the west of Columbia's breakup -- has lent more credence to eyewitness accounts from farther west.
Dittemore conceded it's a needle-in-a-haystack hunt but said it may be NASA's best shot at solving the mystery.
"It's extremely important to us," he said of the search. "It's the real key in the puzzle."
Dittemore acknowledged yesterday that NASA's best and brightest engineers may have made a tragic error in downplaying the impact of insulation foam that struck the shuttle's left side -- foam that fell from the external fuel tank about 80 seconds after liftoff on Jan. 16. The agency is re-doing its initial damage predictions from scratch.
"We're making the assumption from the start that the external tank was the root cause of the problem that lost Columbia," Dittemore said.
But he also cautioned: "We may never know the root cause."
Columbia broke up just 16 minutes from its scheduled landing in Cape Canaveral, Fla. NASA said temperature data showed that the left side -- the side hit by the hardened foam -- heated up sharply just before the shuttle disintegrated.
During the mission's final eight minutes, sensors showed temperatures on and near Columbia's left wing rose quickly and to previously unseen levels.
Though initial signs of trouble were hinted at by excessive drag on the left wing, and by odd sensor readings in the left wheel well and fuselage, Dittemore said those modestly elevated readings probably reflected more serious trouble elsewhere -- the precise, still-unknown site of the breach.
"What they're trying to deduce is whether there's a missing piece to the puzzle," said J. Richard Gott, a Princeton University astronomy professor and author of books on spaceflight. "Are the temperature events that we see what led to the shuttle's destruction? Or is it much more than that?"
NASA officials said that photos showed a piece of insulation, about 16 by 6 by 20 inches and weighing about 2.67 pounds, that could have smashed into the thermal tiles on the underside of the left wing area.
NASA engineers initially calculated the damage as minor, based on a similar episode involving the shuttle Atlantis in October, and on computer calculations with software that usually errs on the side of caution, said Dittemore. One scenario had calculated the risks from a single damaged tile; a second scenario predicted the outcome from several damaged tiles.
Sorting through billions of bits of data, recorded from thousands of instruments and sensors laced through the spacecraft's skeleton, investigators are looking for what may be the pivotal signature event -- the moment when something broke down, setting the catastrophe in motion.
"What NASA is trying to determine at this point is what was the first thing that went wrong, that resulted in the breakup and incineration of the flight vehicle," said Doyle Knight, a professor of mechanical and aerospace engineering at Rutgers University.
"The shuttle infrastructure is a very complex one," said Michael Kostelnik, NASA's deputy associate administrator of space shuttle and International Space Station programs, from National Aeronautics and Space Administration headquarters in Washington, D.C. "There are a lot of hints. There are a lot of ideas as to what has really happened. It would be speculative to make a judgment now, but there are a lot of clues."
And, he added, "we are working with the best and brightest minds in this country to ferret that out."
Some experts speculated Columbia was doomed by a gradual "unzipping" of thermal tiles, exposing the spacecraft's sensitive aluminum skin to blazing heat.
This domino effect could have been triggered by the liftoff incident, or perhaps by wear and tear on the 22-year-old craft, some scientists theorized.
Ice could have formed between the shuttle's tiles in space, and then exploded from the heat of re-entry, said Charles Vick, a chemical engineer who consults for Globalsecurity.org.
"Clearly, it wasn't an explosion," said Mark Drela, a professor of aeronautics at the Massachusetts Institute of Technology. "People saw pieces come off the shuttle as early as California. It suggests the damage was being done progressively."
While an explosion of the shuttle's hydrazine fuel was possible, he said, it would have been "a result, not a cause" of the disaster.
Scorched or burned debris might bear out the theory that thermal shielding failed to protect the spacecraft upon re-entry into the Earth's atmosphere, according to Bill Waldock of Embry-Riddle Aeronautical University in Arizona. If enough parts are gathered, NASA may be able to trace which areas failed.
Debris from the 1996 crash of TWA Flight 800 off Long Island showed bulging and rupturing of the fuel tank, "a fairly obvious fuel explosion," Waldock said. Debris from the Pan Am flight bombed over Scotland in 1988, on the other hand, showed a shatter pattern that radiated outward.
But Jerry Gray, of the American Institute of Aeronautics and Astronautics, cautioned that even in routine airplane crash investigations, "your first guess as to what caused it is almost always wrong."
Star-Ledger wire services contributed to this report.
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