Morton Thiokol Inc. engineers are hailing as a success a test in which a redesigned rocket nozzle was drowned in a flood of water to verify its ability to withstand pressures of launch.

The test conducted Sunday at 3 p.m. was the last in a series of 20 sub-booster firings in advance of the shuttle Discovery's launch, now scheduled for late October."The test was quite successful," said Ed Snow, Morton Thiokol spokesman. "We're very happy the test article is stronger than we expected."

Using a truck from an oil company, Snow said water pressure was pumped and built up until it reached 1,800 pounds per square inch on the booster part.

The redesigned case-to-nozzle joint, which attaches the nose of the booster to the body, was required to exceed by nearly 11/2 times the amount of pressure found in actual flight.

"That was our requirement, to meet that 1.4 level, and that was 1,288 psi," Snow said. "We're very happy the test article did not fail until 1,800 psi and that's very good; that's more than we expected."

The test was the last small-scale examination required before shuttle flights resume.

A flawed Thiokol-built booster rocket was blamed in part for the shuttle Challenger explosion that killed seven astronauts and put the U.S. space program on hold.

If Discovery is launched as expected, it will be the first shuttle flight since Challenger blew up in January 1986.

Engineers are readying for a full 2-minute firing of a booster rocket, scheduled for Thursday. The test, set for 1 p.m. at Thiokol's Wasatch Operations facility in the desert 23 miles west of Brigham City, is the last to qualify the shuttle before Discovery takes to the skies.

Results of Sunday's test probably won't be known until Friday, Snow said.