Atlantis' high-power main engines worked properly during the spaceship's climb to orbit Friday, despite the failure of a critical temperature sensor halfway to orbit, officials said Saturday.

The shuttle's burned-out solid-fuel boosters, meanwhile, were towed toward Port Canaveral, Fla., Saturday for a detailed inspection to find out how redesigned O-ring seals worked during the second post-Challenger shuttle launch.It was an O-ring booster failure that doomed Challenger, and while redesigned seals worked perfectly in the first post-Challenger flight Sept. 29, engineers anxiously awaited Atlantis' rockets to confirm the performance of the new joint design. A complete inspection was expected to take several days.

Unlike the 14-story boosters, which burn for just two minutes or so before falling away for a parachute descent to the ocean, the shuttle's three main engines fire the entire 81/2 minutes it takes to reach orbit.

About 41/2 minutes after blastoff Friday, a critical temperature sensor in Atlantis' main engine No. 3 failed, causing ground controllers a moment of anxiety: had a second sensor failed shortly thereafter, the ship's crew could have faced an abort. But the second sensor worked properly.

"When that little red flag comes on the (computer) screen at 270 seconds, yeah, the old heart beats a step or two faster," said an engineer with Rocketdyne, builder of the hydrogen-fueled powerplants. "And then you realize what's happening and you just watch it."

Engine performance is monitored 50 times a second by computers mounted on each powerplant and if problems are detected, an orderly shutdown sequence can be ordered.

Depending on when an engine shutdown occurred, a shuttle crew could be faced with attempting a harrowing return-to-launch-site abort, a trans-Atlantic abort to an emergency runway in Spain or Africa or an abort to a lower-than-planned orbit.

The only in-flight abort in the shuttle program occurred July 29, 1985, when the center engine of the shuttle Challenger shut down prematurely five minutes and 45 seconds after blastoff, prompting a safe abort to orbit.