"Never Before .. ."

Oft in the stilly nights of the 1970s, the earth's peace will be torn by a thunderous crash as a sleek, supersonic airliner passes high overhead. Such airliners represent the fondest hope of commercial aviation, but they also present serious problems. Writes Bo Lundberg, director of Sweden's Aeronautical Research Institute, in Britain's New Scientist: "A 180-ton Mach 2 or 3 airliner flying at 70,000 ft. would sweep the earth's surface with a thunder-like noise along the entire supersonic flightpath. rattling and often shattering windows, and awakening sleeping people within a band some 70 miles wide. Never before in history would so many have been disturbed by so few."

The noise will come from the shock waves: shells of compressed air that spread in a giant cone behind the speeding airplane. People who live near present-day military airfields are unhappily familiar with supersonic bangs from fighter planes, but, says Lundberg, when commercial air travel goes supersonic, the boom will girdle the globe.

The U.S. aircraft industry agrees with Lundberg, in part. "This is a major concern to all of us," says Charles Blake, transport systems manager at Convair. "If we were in danger of bothering people's sleep or damaging their health, we would have to design a plane to get around this, or there wouldn't be any supersonic airliner." But he thinks that a big airliner flying supersonically at 70,000 ft. will cause a bang no louder than very distant thunder. At lower altitudes the noise will be louder, but the plane will not go supersonic until it reaches 30,000 or 40,000 ft. At that point it will still be climbing steeply, so its shock waves will shoot upward and never hit the ground.

Nobody knows just how much supersonic booming the public will stand. To find out, air authorities have a plan to test public reactions this summer by flying supersonic military airplanes over thickly populated areas at various altitudes, speeds and rates of climb. After the airplane manufacturers have evaluated public protests, they should be able to estimate the extent of their difficulties.

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