Disaster Blamed on O-Rings, Pressure to Launch

In 1977, Marshall engineers Leon Ray and John Q. Miller wrote a report calling for a redesign of the joint, saying, "We see no valid reason for not designing to accepted standards." Redesign, they said, was "mandatory to prevent hot gas leaks and resulting catastrophic failure." NASA rejected the judgment of its engineers.

In 1980 a NASA panel appointed to review the safety of the shuttle in preparation for its first flight wrote that the lab findings showed the O-rings "inadequate to provide operational program reliability and marginal to provide adequate safety factor confidence." Despite this, NASA declared the joints safe enough to fly and continued to do so, even as Thiokol engineers warned in memos of potential "catastrophe."

Over the years, the report says, concern about the problem grew only slowly until 1985 when a rash of O-ring damage cases, including a severe instance in 53-degree weather, caused Thiokol to reexamine the seal's reliability. The company tested the effects of temperature on O-ring resiliency, the ability to spring back from a squeezed condition and maintain a seal as the joint's gap widens. The findings indicated that at 75 degrees, resiliency was diminished and at 50 degrees, virtually nonexistent.

"As the joint problems grew in number and severity," the report says, "NASA minimized them in management briefings and reports. Thiokol's stated position was that 'the condition is not desirable but is acceptable.' "

"At no time," the commissioners wrote, "did management either recommend a redesign of the joint or call for the shuttle's grounding until the problem was solved."

The report says nothing about what happened to the crew as the cabin fell. Privately, however, some commissioners say there is reason to believe the crew may have been alive and conscious for at least the first few seconds after the cabin emerged from the fire.

Loss of pressure and oxygen as well as the forces of rapid tumbling, they say, probably rendered crew members unconscious after perhaps 10 to 20 seconds.

The seven crew members killed in the accident were shuttle commander Francis R. (Dick) Scobee, pilot Michael J. Smith, mission specialists Ellison S. Onizuka, Judith A. Resnik and Ronald E. McNair, payload specialist Gregory B. Jarvis and teacher in space Christa McAuliffe.

In the chapter called "The Silent Safety Program," the commission documents the almost total absence of a safety program in prelaunch decision-making.

The report singles out for attention a 1983 change requested by Martin Raines, director of safety, reliability and quality assurance at the Johnson Space Center in Houston, which eliminated much reporting of flight safety problems to top NASA officials.

"With this action, Level II [top shuttle program managers] lost all insight into safety, operational and flight schedule issues resulting from Level III [middle managers such as the Marshall propulsion officials]," the report says. Raines had said the change was to "streamline the system" after it had become "operational."

The safety program at Marshall "should have tracked and discovered the reason" for a "striking change in performance" of the booster joints beginning in January 1984.