Agonizing Decision Awaits if Root Cause of Disaster Remains Elusive (SPACE SHUTTLE, NASA)

Hard as they try and long as they take, NASA engineers may never isolate the exact, root cause of the Columbia's fatal disintegration.

If it comes to that, the implications for the future of the space shuttles and the International Space Station could be profound, astronautical engineers and policy analysts say. Will shuttle flights have to be shut down while modifications are made on all suspect systems? Or will NASA make some changes, and accept other risks, to send the shuttles back into orbit sooner?

In either case, the decision will be as much political as it is technical. For any decision will depend on the priority given to keeping the multibillion-dollar space station in operation and honoring commitments to the 15 partners, including Russia, in the international endeavor.

Of growing importance in the weeks ahead could also be the respect and authority commanded by the investigation board convened to examine the debris, flight data, photographs and other evidence of what might have contributed to the disaster. If the board is seen as thorough and independent of NASA, its recommendations about future space flight could win support, however difficult to accept and controversial they may become.

Maj. Gen. Michael C. Kostelnik, NASA's deputy associate administrator for the shuttle and space station programs, said it was premature to speculate about the outcome of the investigation into what destroyed Columbia as it glided over Texas two weeks ago toward its planned landing at the Kennedy Space Center in Florida.

On Thursday, retired Adm. Harold W. Gehman Jr., chairman of the investigation board, announced that a hole in the aluminum skin of the left wing and possibly in a wheel compartment was the most likely immediate cause of the shuttle's breakup. The breach presumably allowed devastating superheated gas to move inside the structure, as Columbia re-entered the atmosphere over the Pacific Ocean.

Even if the analysis proved correct, both NASA and independent engineers emphasized, it left unanswered the critical question: what created the hole? Only when they answer that question will NASA know how to get the shuttles flying again with renewed confidence.

"The initiating event is the thing you have to fix," said John E. Pike, director of GlobalSecurity.org, a military and space consulting firm in Washington. "If NASA cannot identify that event, they are going to have to fly the shuttle with no idea of how safe it is, or else we cannot fly at all with that level of uncertainty."

Experts said it could be difficult, perhaps impossible, to reconstruct the chain of failures from the proximate cause, the hole, to the initiating event. They raised concerns that there may not be enough sensor data or other evidence to be certain of success in such an exercise in reverse engineering.

For example, the board's finding did not rule out damage from falling insulation debris at liftoff, a leading theory from the start. But some engineers said it seemed improbable that a few missing heat-resistant tiles alone could have directly caused such damage to the wing.

"NASA will probably be unable to confirm the precise cause of the failure," said Dr. Jerry Grey, director of science and technology policy at the American Institute of Aeronautics and Astronautics.

As unsatisfying as that result may be, it is not unusual in investigations of spacecraft or aircraft failures. Months after the unmanned Mars Observer dropped out of radio contact in 1993, a board of inquiry said it could find "no smoking gun" pointing to the exact cause. A fuel-line rupture was suspected, the board said, after nearly all other possible explanations were ruled out as improbable. The ignition source of the TWA Flight 800 explosion off Long Island in 1996 has never been explained.

The Columbia investigation could turn out to be similarly long and frustrating, experts say. By this time after the Challenger explosion in 1986, the probe had already focused on the failure of the O-rings on a booster rocket, which turned out to be the initiating culprit.

It was 32 months before shuttles were allowed to fly again.Dr. Grey, who is also a professor of mechanical and aerospace engineering at Princeton University, said that investigators need to seek out "the unique sequence of events that culminated" in the shuttle's disintegration. In addition, as occurred in the Challenger investigation, he said, the search will need to be extended "to identify all other potential failure modes and design weaknesses everywhere in the orbiter system, and engineer fixes for them."

Dr. Brian J. Cantwell, professor of aeronautics and astronautics at Stanford University, agreed that the true cause may never be known. The space agency, he said, "may have to live with several plausible scenarios" of what happened.

"I am sure the shuttle will fly again," Dr. Cantwell said, "but it could easily be as much as a year and a half, and the types of missions flown will probably be restricted to those where the space station can be used as a safe haven."

The orbiting space station, currently occupied by two Americans and a Russian, imposes pressures for an early resumption of shuttle flights that did not exist when the Challenger exploded. That creates both engineering and political problems, and the temptation to rush the shuttles back into operation.

"Everyone will say, `If we don't fly shuttles, the space station is going to fall out of the sky,' " Mr. Pike said.

A definitive explanation of what destroyed Columbia, accompanied by well-considered fixes of the problems, will make it easier to justify clearing the shuttles to fly again. General Kostelnik, the NASA official, expressed confidence that there was "a great deal of information available which will help the investigation board understand this event."

Others, supporters and critics alike, fear that the investigation may end short of a full understanding of the root cause or causes behind the tragedy.

That will make the post-investigation decisions about when and to what purpose shuttle flights are to be resumed all the more difficult and probably contentious.

They should be able to slightly pressurize the wings to determine if there are any leaks. If every future flight goes to the space station, they could to a visual tile check and a pressurization check on the wings before re-entry. If the shuttle fails either test, they could stay on the station until either another shuttle or a Russian re-entry module gets them back down. Any orbiter that can't return could remain as part of the space station or could possibly be used as a ferry.

Adm. Harold W. Gehman Jr., chairman of the investigation board, announced that a hole in the aluminum skin of the left wing and possibly in a wheel compartment was the most likely immediate cause of the shuttle's breakup.

This guy is really the master of the obvious. This is like saying that a person died because his heart stopped beating and he quit breathing.

By this time after the Challenger explosion in 1986, the probe had already focused on the failure of the O-rings on a booster rocket, which turned out to be the initiating culprit.

Actually, the "initiating culprit" was gross mismanagement by NASA bosses. O-ring performance at low temperatures was a known issue. Engineers were jumping up and down and screaming at management not to launch. Many of them resigned on the spot when management decided to launch anyway.

When management decided to launch, it was because they were getting hammered by the press and Washington politicians who were impatient with launch delays. NASA didn't bother to ask the question 'What does it do for your precious PR when the shuttle is raining debris all over Florida?' Their decision shows that press PR comes first and shuttle safety is a lower priority.

Will shuttle flights have to be shut down while modifications are made on all suspect systems? Or will NASA make some changes, and accept other risks, to send the shuttles back into orbit sooner?

How did it become acceptable for a shuttle to rain debris all over Kennedy Space Center every time it launches? They might want to start with solving that problem.

The term "root cause" is not a political term, it is a logical and scientific term.

The search for cause and effects is sometimes difficult to conduct, and the process is often called "drilling down" (present participle), as the question, "and what caused THAT?", is asked at each step of the process.

So in this case, they determine that the wing departed from the shuttle. So what caused that? Possible causes could be An immediate weakening of the structure, tire explosion, exceptionally strong aerodynamic or other forces, inherent wing design flaw, aging of the structure, etc.

So we do a drilling down on each of these. What would cause the immediate weakening of the structure? Heat, impact, etc. What would cause a tire to explode? Internal pressure from expansion due to heat, damage from another body, etc.

As you can see, the process of finding the root cause can grow geometrically or exponentially. Probability and possibility always enter into the cause-effect evaluation, too, introducing the possible, and uncomfortable, conclusion that a "likely" scenario is the only explanation left.

I think that a probabalistic distribution study of the prior impact data of foam damage to tiles on prior flights could give a strong possibility that liberated foam could be in the chain of events. The root causes of loss of vehicle from that could be the PC foam and/or the susceptability of the tiles. In that second case, there should have been boost protective covers installed on the nose and leading edges of the wings and tail to minimize damage to the tiles during launch.

"Actually, the "initiating culprit" was gross mismanagement by NASA bosses.

I agree with that, especially after seeing these "expert's" presentations in the last 2 weeks.

There are some serious problems at NASA, not the least of which is the serious damage caused by heavy leakage of politics and political correctness into the system.

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