NASA yesterday announced a new "planning date" of Aug. 4 for the next shuttle launch as the space community prepared to mark the second anniversary of the Challenger disaster and a former top space official called the long delay in flights "totally unacceptable."

Officials of the National Aeronautics and Space Administration said recent shuttle hardware problems can be resolved by August. "The flags are back at full staff, the program and the people on this team are looking forward and I think that's what our friends {the seven crew members who died aboard Challenger} would expect from us," said Richard H. Truly, head of the space flight program.

On the eve of the Jan. 28, 1986, Challenger disaster anniversary, Christopher Kraft, who became a familiar figure to television viewers as director of flight operations at the Johnson Space Center in Houston during the Apollo moon program, took issue with policymakers' decisions to ground the shuttles for so long.

"If we see space flight as a necessary element in our formula for national survival, then a 2 1/2-year hiatus is totally unacceptable," he told a National Geographic Society audience last night.

He said his comments were intended "not to necessarily criticize what has transpired but to prepare for what is likely to happen again. More specifically, if every time there is a fatal accident in space, the result is a long and frankly unnecessary delay before continuing, then we should reevaluate our objectives."

"Flying in commercial airplanes, driving on the freeway, or walking across the street have their risks, but we have all accepted the gains commensurate with these risks," Kraft said. "Why should space flight be treated in any other way?"

Since the Challenger accident, NASA has reviewed virtually the whole shuttle system, redesigning and retesting large parts of it.

Truly, appearing before a House space subcommittee yesterday, said the latest launch delay and recovery demonstrates that "we have struck the proper balance between our first priority of safety and quality while maintaining our commitment to return the shuttle to flight just as quickly as we can reliably do so."

The first post-Challenger launch was previously scheduled for June 2, but the date was postponed for the third time in two years because of a failure in a part of the booster nozzle assembly during a Dec. 23 test firing.

Officials were delayed in announcing a new date this week when faulty welds were discovered in other pieces of shuttle hardware -- the booster aft skirts and main engines. However, Truly said yesterday, engineers have determined that the problems can be handled within the new schedule.

Officials have also decided to require three more full-scale test firings of the solid fuel rocket boosters before the next flight. They hope to fully verify the redesigned O-ring joints, whose failure caused the Challenger to explode 73 seconds after launch. Only two such tests were previously considered mandatory.

Aug. 4 is the "internal planning date" for the next launch, for purposes of coordinating complex activities leading up to the flight, officials said, but they stressed that an official launch date could later be set for anytime in August.

Under the current schedule, the shuttle Discovery will be rolled out to the launch pad at Cape Canaveral on May 13, with a "readiness" test firing of the main engines and other propulsion systems on June 13.