SONIC BOOMS MAY GET LESS BANG PLANES' REDESIGN COULD CUT SOUND.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - The sonic boom, that wall-shaking, heart-stopping proclamation of man's victory over the sound barrier, could be reduced to a mere boomlet by redesigning supersonic aircraft.

That was the conclusion announced Thursday by Northrop Grumman, which spent $7 million researching technologies that would make future supersonic aircraft fly more quietly.

``Based on those studies, an experimental aircraft could eventually be built that will produce a noticeably quieter sonic boom.'' said Charles Boccadoro, Northrop Grumman's program manager for the Defense Advanced Projects Research Agency's Quiet Supersonic Platform.

The theory was proven Wednesday during a set of flight tests at Edwards Air Force Base using two F-5E fighters, one with a specially modified nose section. The jets were flown, one at a time, over a test range with ground sensors measuring the sonic booms.

The findings eventually could mean eased restrictions for military aircraft now allowed only in certain flight ranges and the Concorde passenger jet, now limited to supersonic flight over the ocean.

``The demonstration has proven the theory that you can reduce sonic boom intensity by changing aircraft shape, and engineers will be able to study the data to learn more about the effects of aircraft shaping on sonic overpressure,'' Boccadoro said.

The research program was aimed at developing technologies for future high-speed business and military aircraft, and on Thursday Northrop Grumman claimed success in proving sonic booms could be softened by altering a jet's shape.

The data comparison of the two aircraft signatures clearly showed a reduction in intensity of the sonic boom produced by the F-5E with a modified fuselage. An identical test later in the day confirmed these results, Northrop Grumman announced.

The sonic boom research, called the Shaped Sonic Boom Demonstration program, is jointly sponsored by DARPA, Northrop Grumman Corp.'s Integrated Systems sector and the National Space and Aeronautics Administration's Langley Research Center in Virginia. The flight tests were conducted by NASA Dryden Flight Research Center at Edwards.

For the sonic boom research, a Navy F-5E was outfitted with a specially shaped ``nose glove'' and the addition of aluminum substructure and composite skin to the underside of the fuselage.

The QSP program is not aimed at building an operational aircraft, but at providing technologies that could lead to new or improved bombers and fighters, reconnaissance aircraft and supersonic commercial aircraft, according to DARPA.

Such technologies would allow commercial and military aircraft to fly unrestricted over land rather than being restricted to certain test ranges or, as in the case of the Concorde passenger jet, being restricted to trans- Atlantic flights.

For the military, the technologies could lead to a small supersonic strike aircraft that would perform more missions per day, deliver more weapons on target and provide a rapid, long-range response capability, DARPA officials said.

The objectives of the QSP program are to create an aircraft that would weigh 100,000 pounds; cruise at speeds of Mach 2 to Mach 2.4, roughly between 1,400 mph and 1,680 mph; and have an unrefueled range of 6,000 miles.

By comparison, DARPA said, the Concorde weighs 400,000 pounds, cruises at Mach 2, and has an unrefueled range of 3,550 miles.

The program's goals are for the aircraft to create a sonic boom carrying an air pressure no greater than 0.3 pounds per square foot. A Concorde flying at an altitude of 50,000 feet creates a sonic boom of 1.94 pounds per square foot; a space shuttle returning to Earth causes a sonic boom of 1.25 pounds per square foot.

Jim Skeen, [phone]

james.skeen(at)dailynews.com