Two More Shuttle Safety Defects Cited

Columbia accident investigators said Thursday they have discovered at least two serious safety defects on the space shuttle fleet that must be corrected before flights can resume.

The first of the new defects, which involves explosive bolts that hold the solid rocket boosters to the shuttle’s external tank and then release them, is under scrutiny as a possible cause of the Columbia accident, investigators revealed for the first time.

Although investigators remain committed to the theory that insulating foam damaged Columbia’s wing shortly after liftoff, they cannot rule out the possibility that a 40-pound fragment of an explosive bolt fell away from the shuttle about two minutes into the launch and slammed into the orbiter.

Investigators said that as many as 17 possible accident causes may remain permanently unresolved and that NASA engineers will have to spend substantial efforts to understand those uncertainties after the formal investigation is closed.

“There are going to be elements [of the investigation] that are not going to be able to be closed out,” warned Maj. Gen. John Barry, a member of the Columbia Accident Investigation Board.

The second of the new defects found in the board’s investigation into every aspect of the shuttle program involves another set of explosive bolts that release the shuttle from the launch pad three seconds after the main engines ignite.

In a launch last year, a mechanism that activated one of four massive hold-down bolts failed, forcing the use of a backup system that performed correctly. But the board still has questions about whether NASA adequately dealt with the malfunction and whether the issue slipped through the cracks of the agency’s bureaucracy, said board chairman Harold Gehman Jr.

Gehman said officials at different NASA centers disclaimed responsibility for the problem when asked about the malfunction and told investigators that the problem was another office’s concern. Although the launch pad bolts are not under investigation in the Columbia accident, they could cause a problem on a launch, the board said.

If the board formally recommends that NASA correct or otherwise resolve the two new safety defects, it would add to two problems identified. NASA is working to come up with a system to prevent foam debris from falling off the external tank and methods to better inspect the thermal protection system on the leading edges of the wings.

Board investigators also disclosed Thursday new information about the foam tests conducted last week in San Antonio. A foam block shot from a gun at a replica of Columbia’s wing caused more extensive damage than thought. The shot caused a 5.25-inch crack in a wing panel, a crack in an adjoining T-seal and a crack in an attachment point behind the panel, said board member Scott Hubbard.

But investigators cannot yet say that the cracks alone would have allowed superheated gases to penetrate the wing and cause the disaster during reentry. Hubbard said small cracks caused at launch could have grown from any number of stresses later in the mission. The board will conduct at least two more series of foam gun tests this month, and the outcome of those tests may give the board more evidence that the foam damaged the shuttle’s wing.

New doubts were also cast on NASA’s understanding of why foam even falls off the external tank. Physicist Douglas Osheroff, a board member, said an experiment conducted in his kitchen punctured NASA’s explanations. “It behooves NASA to understand these processes better,” he said.

The new defect involving the rocket boosters has opened up an alternative possible explanation of the accident.

During the Columbia launch, a radar picked up unexplained debris shed off the shuttle 128 seconds after it left the pad. That coincides with the point where the solid rocket boosters are separated from the external tank by two sets of explosive bolts. The two solid rocket boosters provide the majority of thrust for the shuttle’s ascent.

After the boosters burn out, the 80-pound bolts are designed to blow apart into 40-pound halves, allowing the spent rockets to fall back into the ocean.

The pieces of the bolts are not supposed to fly into space because they would cause catastrophic damage if they struck the orbiter. Metal structures called “bolt catchers” are supposed to retain the chunks.

Gehman said the board found that the bolts explode with nearly as much force as the catchers are designed to absorb, leaving no safety margin. When investigators conducted a ground test of the system, they found the catchers fractured.

The discovery surprised NASA officials, who had recently switched to a new contractor for the bolt-catcher devices. The Columbia investigation has also raised questions about quality-control procedures by the manufacturer of the bolt catchers, Gehman added.

Gehman said he is confident that weak bolt catchers did not cause the Columbia disaster and that no other data indicate the bolts struck the orbiter. However, Gehman warned that the problem “has the potential” to cause the loss of another spaceship.

NASA said it already is dealing with the issue. “This is something we are going to have fixed before we return to flight,” said spokesman Allard Beutel.

The accident board also held its final public hearing Thursday, taking testimony from some of the nation’s top space policy experts.

Marcia Smith of the Congressional Research Service said the Columbia accident could not be directly linked to NASA’s tight budgets.

“It’s very difficult ... to say that because of budget cuts, the Columbia tragedy happened,” Smith said. “If NASA did not fully appreciate the damage associated with foam hitting the orbiter, I don’t know that bigger budgets would have helped that.”

Retired aerospace executive Tom Young, an elder statesman in space policy circles, said NASA probably “went too far” in ceding responsibility to shuttle contractors. He called for the creation of a strong safety organization to serve as a “third set of eyes” monitoring NASA and its contractors.

The space program “is a one-strike-and-you’re-out kind of business,” Young said. “You really need to have the best of government and the best of industry. I don’t believe the government can pass that [responsibility] on.”

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Alonso-Zaldivar reported from Washington, Vartabedian from Los Angeles.