Lawrence B. Mulloy, the shuttle rocket chief who pushed to launch Challenger over the objections of engineers, was moved to a new job yesterday, the National Aeronautics and Space Administration announced.

In what a NASA spokesman termed a "lateral transfer," Mulloy was appointed assistant to the director of the science and engineering directorate at the Marshall Space Flight Center in Huntsville, Ala. The post is new, according to spokesman Ed Medal, but it will carry the same salary and civil service rank as Mulloy's former job as manager for NASA's solid rocket project.

This was the third time a figure who played a key role in the decision to launch has left his position at Marshall since the space shuttle Challenger disaster on Jan. 28 that killed the crew of seven.

In an announcement released late yesterday, William Lucas, director of the Huntsville center, named Gerald Smith to replace Mulloy. Smith has been serving as deputy manager of the group redesigning the rocket booster joint which, evidence shows, caused the Challenger to break up.

Officials offered no comment as to the reasons for the transfer. Mulloy could not be reached.

Mulloy, who has taken the brunt of criticism over the Challenger disaster, has staunchly defended the decision to launch, his role in it and the basic design of the rocket joint, given the constraints of the program and his information at the time. He said as recently as last Saturday in an interview with The Washington Post that he expected to remain head of the project.

On the eve of the flight, engineers for Morton Thiokol Inc., the maker of the shuttle booster rockets, unanimously recommended a launch delay because they were concerned about the effects of cold weather at the Florida launch site on critical rubber seals in the joints between the booster segments.

Mulloy challenged the engineers to prove their conclusions and insisted that test data did not support their recommendation. After a telephone conference with the engineers, Morton Thiokol managers recommended the launch, overruling their own engineers, and top NASA officials were not informed of the engineers' concerns about the temperature.

Stanley Reinartz, shuttle projects office manager, told the presidential commission investigating the accident that he made the decision not to tell officials higher up about the dispute that night. A month ago, he asked to be reassigned to his old job as manager of special projects at Marshall.

George Hardy, assistant director of the Marshall science and engineering directorate, retired last Friday. He took part along with Mulloy and Reinartz in the launch-eve meetings.

Since the launch, a series of reports and witnesses have indicated that NASA and contractor engineers had been concerned about the joint design as far back as 1977.

Also yesterday, NASA announced that it will ask a panel of independent experts to oversee the redesign of the booster joints. The action came in the wake of reports that some members of the presidential commission were angered by indications that the agency's redesign team might be settling for a "quick fix" of the joint problem.