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NASA to Give Preliminary Shuttle Report Thursday

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Times Staff Writer

NASA investigators will give their preliminary findings on the Challenger space shuttle disaster to members of a presidential panel Thursday, apparently concluding that a flawed joint design was the underlying cause of the explosion that killed seven crew members.

After hauling tons of wreckage from the ocean floor, searching records and conducting about 300 tests focusing on the solid rocket joint that spewed smoke and flame in the seconds after the shuttle lifted off, experts have been unable to find anything that set the doomed booster apart from others launched in the shuttle program.

J. R. Thompson, chief investigator for the National Aeronautics and Space Administration, told reporters in Florida on Tuesday that he expects that “several factors” will be determined to have played a part in the tragedy, which has brought the U.S. space program to a standstill.

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High-Altitude Wind Shear

He said he finds “plausible” a two-step scenario in which a leak was created in a joint of Challenger’s right solid rocket booster a split-second after ignition but did not become a catastrophic problem until the spacecraft hit a heavy, high-altitude wind shear.

The team conducting NASA’s internal investigation of the accident is due to give its final report to the presidential commission on April 18, but Thompson described Thursday’s meeting with commission members at the agency’s Marshall Space Flight Center in Huntsville, Ala., as an occasion for “a major data dump.”

The presidential panel is to report its finding of the accident’s probable cause in early June.

Focus on Four Factors

Thompson said the NASA inquiry is now focused on four factors that could have been involved in the sequence leading to the explosion 72 seconds after Challenger was launched Jan. 28:

--”Joint rotation” occurring with engine ignition and creating enormous pressure inside the solid boosters.

--Performance of the putty that is designed to protect the airtight seal in the joints between the rockets’ segments.

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--Effects of subfreezing temperatures through the night before the spacecraft was launched.

--Alignment of the rocket segments, which had to be forced into position when the booster was assembled a month before launch.

‘Edge of a Cliff’

Thompson said that several factors could have been involved, beginning at ignition and continuing until the shuttle erupted in a massive fireball. But rather than the accident being caused by something unique about the Challenger vehicle, he told reporters: “I think we were walking right on the edge of a cliff, and several of these factors just pushed us over.”

He refused to discuss the continuing search for debris from Challenger’s crew compartment, but he said the top priority now is to find pieces of the right solid booster in hopes of finding the section of the rocket joint where the failure occurred.

The theory that a high-altitude wind shear could have been a factor in the accident was raised at a meeting of the presidential commission last month when Maj. Gen. Donald J. Kutyna observed that the shuttle “was going on a fairly bumpy road” just before the explosion.

According to this theory, the joint might have been “weakened” upon ignition but still sealed and performing adequately until the shuttle reached the period of maximum launch stress and encountered a wind shear in the upper atmosphere.

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