First theory on Columbia may be best

Deseret News (Salt Lake City), Apr 6, 2003 by Marcia Dunn AP aerospace writer

SPACE CENTER, Houston -- Two months after the shuttle Columbia shattered in the skies over Texas, accident investigators have considered every possible theory, no matter how wild -- a killer micrometeorite, some sort of high-altitude electrical zap and even the scientific experiments on board.

Yet the strongest theory still seems to be the one that emerged the first day -- the theory that foam insulation ripped off the fuel tank just after liftoff and smashed somewhere on the shuttle's left wing, causing enough damage to lead to disaster.

"This is a leading contender, but we don't have the final proof," said Scott Hubbard, a member of the Columbia Accident Investigation Board and a high-ranking NASA official.

The weeks of investigation since the Feb. 1 accident that killed seven astronauts have mostly uncovered more evidence backing that original theory.

NASA knew early in Columbia's 16-day mission that foam debris had broken off the fuel tank and hit the left wing. But mission officials had concluded it did not pose a danger.

Just this past week, tape from an old-fashioned reel-to-reel data recorder pulled from the Texas mud revealed that heating problems that developed during Columbia's return to Earth began much earlier than thought.

The recorder detected an unusual warming trend in the left wing barely a minute after the shuttle first hit Earth's atmosphere over the Pacific.

To investigators, that is evidence that Columbia was mortally wounded early on, and that plumes of scorching air had entered a pre- existing gash in the wing and started burning through.

They have been unable to come up with a plausible theory that the gash in the wing came from space junk or something else in orbit, leaving the foam debris strike as the most likely culprit.

In the coming weeks, experts will be conducting rigorous tests to determine how much damage the foam could have caused. In fact, NASA officials were so concerned about the foam that two days after the shuttle disaster they called a research institute to ask about setting up foam impact tests.

Those tests are now planned in a week or so. The findings from them, combined with other clues, may offer at least strong circumstantial evidence for determining the root cause of the accident.

Now that investigators know Columbia was experiencing trouble so early in its re-entry, they may take a harder look at the famous cockpit video -- the one showing smiling crew members calmly going about their work.

When it was first seen, no one believed it offered any investigative value because it ended four minutes before what was thought to be the first sign of trouble.

But now that investigators know the first temperature spike happened earlier, they are considering whether anything new can be gleaned from the cockpit gauges and screens or the window views of the blast furnace-like atmospheric flashes outside, an official close to the board said late last week.

The official said no one is suggesting the seven astronauts knew anything was amiss early on. But he noted: "Nothing has been totally ruled out at this point. We're looking at everything."

At the same time, the head of the accident inquiry said it's still too early to be wedded to the foam theory.

Retired Navy Adm. Harold Gehman Jr., has said repeatedly he and his colleagues "are leery of falling in love with the theory of the day."

"We're not about to quit," Gehman stressed last week.

Just because a mysterious object floating away from Columbia on its second day in orbit was most likely a panel from the left wing for instance, does not mean such a panel was the location of the breach, according to the board.

"You just can't make that leap of faith," said board member Roger Tetrault, a former nuclear submarine builder.

Gehman has a hunch that peeling foam won't be the only problem NASA has to fix before launching another shuttle. The age of the spacecraft and possibly ground equipment may wind up being contributing factors.

Columbia first flew in 1981 and was on its 28th mission.

"In my opinion, foam hitting a healthy orbiter probably couldn't hurt it," Gehman said. "But foam hitting an orbiter which was kind of worn and torn a little bit ... It turns out that Columbia has a history of slightly hotter landings and rougher wings and more I- loads on takeoff. Well, you add all these things up -- which we are doing -- and maybe you've got an orbiter which is, by one measure, older than we think it is."

Last week investigators cited a new theory for what might have weakened the shuttle's wing. Pinholes have been spotted on the heat- resistant carbon panels that line the leading edges of the wings. These signs of corrosion may have been caused by paint primer leaching from NASA's old launch towers, and could have weakened the panels enough to break when struck by a 2-pound, 2-foot-long chunk of foam, some experts say.

So the board has a team looking at the wear and tear that has occurred for years on NASA's aging shuttles.