Former astronaut Robert Crippen, NASA's deputy director of shuttle operations, will give the final "Go" for the next shuttle launch, his boss told a Senate hearing yesterday.

"Crippen will be the last man to sign off," said Arnold Aldrich, head of shuttle operations. The launch, twice rescheduled, is now planned for sometime in August.

Crippen has flown a record four shuttle missions, including the first in April 1981, and is one of an increasing number of astronauts who have joined National Aeronautics and Space Administration management since the Jan. 28, 1986, Challenger disaster, which killed a crew of seven.

Frederick Hauck, commander of the next flight, told the Senate science, technology and space subcommittee that the astronauts who have been monitoring the redesign of the booster and other parts of the shuttle feel that their concerns have been given a fair hearing. He said he feels "confident and comfortable" with the actions taken by NASA.

NASA officials said at the hearing that they expect to select one of two astronaut escape techniques that are now being tested in time for it to be installed in Discovery for the next flight.

One approach would fire tractor rockets to pull astronauts clear of the shuttle in an emergency under certain conditions. The other would use a pole, somewhat like a firemen's pole, that would extend through the hatch and allow the astronauts to slide clear.

Hauck said the astronauts would prefer the sliding pole, if the tests are successful, because unlike the rockets it does not require carrying explosives in the cockpit.

NASA officials said the August launch is possible if no new problems develop.

An outer boot ring, which failed in a test firing in December and caused a delay in the launch date, has been replaced with a backup.

Senators, and members of independent advisory panels who testified, emphasized the importance of quality control in the manufacturing and assembling process for the solid rocket boosters.