Disaster Blamed on O-Rings, Pressure to Launch

"Not recognizing and reporting this trend can only be described, in NASA terms, as a 'quality escape,' a failure of the program to preclude an avoidable problem. If the program had functioned properly, the Challenger accident might have been avoided," the report says.

"The space shuttle's solid rocket booster problem began with the faulty design of its joint and increased as both NASA and contractor management first failed to recognize it as a problem, then failed to fix it and finally treated it as an acceptable flight risk," the report says.

Among the commission's chief findings:

*The cause of the Challenger accident was determined to be the failure of O-rings in the right-hand booster joint to contain the pressure of hot gases produced by burning rocket fuel. Flames burned through the booster wall, causing the booster to tear away from the external tank, which ruptured, spilling highly flammable liquid hydrogen and liquid oxygen.

*Low temperatures on launch day stiffened the rubber O-rings so much that they could not maintain a seal in a joint that, because of poor design, opened the gap the rings were supposed to seal in the first second after ignition.

*Neither NASA nor booster manufacturer Morton Thiokol Inc. understood how the joints worked nor did they test the joints in a reasonable simulation of how they would be used in flight.

*Both NASA and Thiokol were playing "a kind of Russian roulette" by continuing to fly the shuttle despite known problems. They "accepted escalating risk apparently because they 'got away with it last time.' "

*Although NASA officials repeatedly told the commission that there was no correlation between cold temperatures and O-ring problems on previous flights, the commission found the opposite and said that NASA should have, too. In all four prior flights that launched below 65 degrees, there was damage to O-rings. By contrast, of 20 flights in warmer weather, only three experienced O-ring damage.

*Top NASA officials in Washington received a sufficiently detailed briefing on the O-ring problems in August 1985 to have stopped shuttle flights long enough to correct the problem. But they did not.

*The commission was "surprised" that in all the testimony it heard, "NASA's safety staff was never mentioned." A report chapter, called "The Silent Safety Program," says no member of the safety staff was invited to key meetings leading to launch. Cutbacks in safety department staffing weakened its role, and at Marshall and the Kennedy Space Center, safety offices are supervised by the same people they are supposed to check on.

*The night before launch, when Thiokol management reversed the no-go recommendation of its engineers, the switch was made not on the basis of sound safety concerns but "to accommodate a major customer."

*On the morning of Jan. 28, when orbiter manufacturer Rockwell International advised against launch because of ice on the launch tower, the company's degree of expressed concern was ambiguous -- but NASA should have scrubbed anyway.