Shuttle Back Home; Engine Failure to Be Probed

The space shuttle Challenger cruised to a smooth landing here Tuesday, and engineers said they would begin an investigation today into the cause of the engine shutdown that threatened the shuttle’s launching eight days ago.

Space agency technicians were scheduled this morning to remove suspect sensors that are believed to be responsible for the premature, computer-ordered shutdown of one of the craft’s three main engines. The sensors will be sent to their manufacturer for what the agency called an “expedited analysis.”

About 18,000 spectators watched and cheered here as the Challenger glided out of a cloudless sky, touching down at 12:46 p.m. The shuttle’s return was delayed one day to allow additional scientific information to be collected aboard the Spacelab 2 flight.

Jesse M. Moore, director of the shuttle program, described the flight as “the most important scientific mission the shuttle has flown,” and praised the shuttle team’s ability to produce the scientific rewards even after last Monday’s harrowing launching.

The premature engine shutdown was the first during flight in the history of the nation’s manned space program. After the engine turned off about five minutes after liftoff, the remaining two engines pushed the shuttle into a low orbit.

The shuttle does not use its main engines on its return to Earth, instead burning its auxiliary thrusters to leave orbit.

“That bird out there on the lake bed really performed beautifully,” said mission commander Gordon Fullerton. But he added, “we are going to recommend that it be sent back to the shop for an engine tuneup.”

NASA said the temperature sensors, which indicated the engine had overheated minutes after lift-off, probably sent incorrect information to the craft’s computers.

The space agency said technicians would also begin a hurried analysis of the engine today in case the temperature sensors were correct.

At a press conference following the landing Moore said it apparently did not produce a repeat of brake problems that have plagued recent landings. Initial inspections showed the brakes to be in good condition, Moore said.

The Spacelab mission, which was designed to collect information about the sun and Earth’s upper atmosphere, returned with a wealth of material, NASA scientists said.

Initially, the scientists said, the low orbit of the Challenger and a shortage of fuel seemed to produce what one official called “insurmountable problems.”

Adding to those woes, the primary piece of hardware aboard the winged spacecraft--a $60-million pointing system for four telescopes--failed to perform some of its functions for the first few days of the flight.

But by the end of the mission, said Burton Edelson, director of science programs for the shuttle, virtually all of the projects were able to carry out most of their work.

Besides Fullerton, the crew for this flight included pilot Roy D. Bridges Jr.; medical researcher F. Story Musgrave, and astronomers Loren W. Acton, John-David Bartoe, Anthony England and Karl Henize.