HUNTSVILLE, ALA., SEPT. 4 -- A segment of the first redesigned shuttle booster rocket cracked after test-firing last Sunday because of ground cooling problems, but indications are that the design changes worked successfully, a space agency official said today.

"Everything in this design looks like it behaved just as we predicted," said Gerald Smith, manager of the booster program at the Marshall Space Flight Center. "It looks like we've got a good design."

He said engineers have inspected the inside of the booster but have not disassembled it to examine redesigned O-ring joints between fuel segments. A joint failure triggered the Challenger space shuttle explosion in January 1986.

The test-firing at the Morton Thiokol plant near Brigham City, Utah, was a major milestone toward the resumption of shuttle flights next June.

The crack in the redesigned booster's steel casing occurred after the two-minute firing and had nothing to do with the design changes, Smith said.

He said the crack was the result of overheating caused by the failure of a water spray system to keep molten slag from insulation and fuel residues that collected on the bottom of the inside of the burned-out rocket. The problem occurs only in horizontal ground firings.

The crack occurred in one of three sections comprising the booster's aft segment. Smith said the National Aeronautics and Space Administration will not be able to use the damaged segment in future tests, as was hoped.

Engineers are a day behind schedule in dismantling the rocket because of an investigation into the cracked segment, he said. If all goes well, the 126-foot booster will be disassembled in plenty of time for the next firing, tentatively set for Nov. 29, he said.lement of the test was to evaluate the performance of a new insulation design around the joints that includes a new feature called a "J-seal."

The J-seal is simply a gap in the insulation just above the point where two segments come together. When the motor is ignited, internal pressure forces the gap apart, which in effect creates a downward force to firmly press the insulation surfaces of two segments together, eliminating any path for hot gas to reach the O-ring joints.

"Looking at the J-seals as well as we can, which is simply looking at where the two pieces come together on the inside of the motor ... it looks just great," Smith said. "So there's nothing, again just from appearance inside the motor, that suggests any kind of a problem.

"The only reports I keep getting are everything looks just great. So we're very anxious to take the thing apart."

-- -- -- -- -- -- -- -- --

upi 09-04-87 01:42 ped