Probe Trying to Reconstruct Launching Dispute

Investigative teams from the presidential commission on the Challenger disaster privately interviewed key witnesses in three cities Friday, trying to reconstruct a crucial engineering debate that led the manufacturer of the space shuttle’s rockets to withdraw its opposition to the launching.

National Aeronautics and Space Administration officials who debated with engineers from Morton Thiokol Inc. the night before the Jan. 28 flight declared on Friday that they would not discuss the matter until a public commission hearing Tuesday. Nonetheless, there were widespread reports that NASA had applied “an incredible buildup of pressure” to persuade Morton Thiokol management to overrule its own engineers and consent to the launching.

Engineers Overruled

Sources have said that 15 Morton Thiokol engineers opposed launching the Challenger because of subfreezing temperatures at Kennedy Space Center, Fla., but were overruled by four senior management executives after hours of intense discussion. The engineers believed that the extreme cold could hamper the performance of crucial seals of synthetic rubber that prevent hot gases from escaping through booster rocket seams.

“Why they were overruled and why all the pressure came to reverse their judgment is the unanswered question,” said Sen. Donald W. Riegle Jr. (D-Mich.), who has spoken with a key participant in the prelaunching discussions.

At the Kennedy Space Center, commission members Sally K. Ride, Richard P. Feynman and Robert B. Hotz interviewed officials who participated in the discussions.

It has been disclosed that several top NASA officials who decided to proceed with the flight were never told of the debate with Morton Thiokol engineers.

Team in Huntsville

Another commission team was in Huntsville, Ala., where NASA rocket operations are centered, to conduct interviews with the handful of space agency officials who participated in the debate with Morton Thiokol engineers. A third team was at a Morton Thiokol facility in Utah.

All of those interviewed are scheduled to testify before the full commission in Washington on Tuesday and Wednesday in sessions that should shed further light on the question of why NASA officials and Morton Thiokol executives ignored a unanimous opinion by the rocket engineers.

“We’re going to try to develop all the facts involved in the decision-making process,” the commission chairman, William P. Rogers, said.

Friday evening was the deadline for NASA officials and Morton Thiokol executives involved in the prelaunching discussion to deliver to the commission any personal notes, memoranda or other documents relating to the matter. Rogers said he intends to spend the weekend reviewing the material.

Two of the scheduled principal witnesses are Allan McDonald, the top Morton Thiokol representative at Kennedy and the most adamant opponent of the launching, and Lawrence Mulloy, who, as NASA’s solid rocket project manager, has been identified as challenging the Morton Thiokol engineers.

‘Not Your Concern’

Riegle interviewed McDonald earlier this week and was told by the engineer that, at one point in the discussion, which was conducted over several hours, a NASA official told McDonald: “This is not your concern.”

In fact, McDonald was empowered to sign the Morton Thiokol consent form approving the launching. He refused even after four senior executives disregarded the advice of the 15 engineers and voted to recommend a launching.

The primary concern had been how the rocket’s synthetic rubber O-rings would hold up in cold weather; McDonald and other Morton Thiokol engineers cited data indicating that cold weather might alter the performance of the crucial rings when the rocket ignited, allowing gases from the propellant to escape through a seam between sections of the rocket.

Aviation Week and Space Technology reported Friday that NASA had access to studies that showed how wind coming off the shuttle’s liquid fuel tank in freezing weather could make the right solid booster even colder than the ambient temperature. The usually reliable trade publication said that the space agency did not make use of the studies in deliberations on the Challenger flight.

It has since been learned that, on the morning of launching, technicians recorded temperatures as low as 7 degrees on the bottom of the right solid rocket booster.

Cold Increased Peril

Riegle said McDonald had told him that NASA wanted to launch no matter how cold it was--even though the danger increased by each degree that the temperature dropped. “The decision was to go, period,” Riegle said. “There was no lower limit on temperature below which the launch would not take place.”

According to Riegle, McDonald argued also that 30-foot seas and stiff offshore winds would make it hazardous for NASA ships to recover the reusable booster rockets. Finally, Riegle said, the engineer noted that alterations in the way the rockets were to be fired would produce additional stress on the joints.

“Why there was this incredible buildup of pressure to go at that moment and override all of these warning signals remains the central mystery here,” Riegle said.

Meanwhile, Sen. Ernest F. Hollings (D-S.C.) called for a Senate investigation into the decision to launch, contending that the presidential commission’s inquiry is inadequate. Hollings charged that the commission lacks experienced investigators and is failing to promptly inform the public of its findings.

Staff writer Kim Murphy at Kennedy Space Center, Fla., contributed to this story.