"Sonic boom is nothing to be scared of—prepare for it." an 8-year-old girl wrote in a composition for her third-grade class in a Chicago suburb. "Glass will brake. Vibrashun will bust ear drums. It will be loud as thunder. You should not be scared though."
This unsettling advice came when the Air Force announced that for three months of 1965, Strategic Air Command B-58 Hustler bombers would make simulated lone bombing runs on Chicago several times a| day. As part of a training program, each bomber had to accelerate to Mach 2, twice the speed of sound. on its bomb run down the length of Lake Michigan. The jet would be going 1,300 mph as it roared over the Loop at 42.000 feet.
Chicago is rarely overflown by planes traveling at such speeds. When this happens by accident, hundreds of frightened persons invariably call the police to report an "explosion." What they hear is an unpleasant bang called sonic boom, continually produced by a plane flying faster than the speed of sound. Two pressure waves, somewhat like the wake of a speedboat, trail behind the aircraft over the countryside. The "boom carpet" may extend 25 miles each side of the plane's path. unrolling for thousands of noisy miles as the plane speeds along.
An Air Force press release explaining the military need for the Chicago bombing exercise said: "The sonic boom has often been ealled 'The Sound of Freedom.'' A biting Chicago Daily News editorial disagreed: "Hogwash. The SAC crews do not have to shatter windows and nerves in a metropolitan area to learn their trade. Supersonic training flights can be made over the deserts and sparsely populated areas."
A bleak hunch was voiced by Congressman Roman Pucinski,. an Armv Air Forces flier in World War II whose Chicago district includes O'Hare Field, the nation's busiest airport. Pucinski noted America is designing a supersonic transport (SST) that will fly at three times the speed of sound. "Within 10 years, there may be no escaping sonic booms anywhere," he warned. "Supersonic commercial jets will be crisscrossing the country at all hours of the day and night, producing loud booms.. Nobody will be able to sleep then." It was Pucinski's suspicion that the Air Force was acting for the Federal Aviation Agency, developers of the SST, "to condition the public to sonic booms." The Daily News chimed in: "We are supposed to grow accustomed to the sonic boom as a 'sound of security.' Perhaps like Pavlov's dogs we are to develop a conditioned reflex."
Secretary of the Air Force Eugene Zuckert denied the allegations. He wrote Congressman Pucinski that it was vital for the B-58 crews to "conduct practice missions against targets in the United States that present a radar picture similar to those in the territories of potential enemies."
A 10-man Air Force damage-claims team awaited developments as the first of 49 booms began rattling windows and shaking walls. Most damage complaints told of cracked glass and plaster—but they added up. A city-owned parking garage wanted $950 to replace two large windows. An entire plaster ceiling in a 36-by-l6 foot conlference room collapsed at the Second Presbyterian Church of Evanston. The pastor, who helieved that repeated sonic booms had weakened the ceiling, presented a $5,000 repair bill. An angry man demanded compensation for his dog, which had to be destroyed, he said, because its epileptic seizures were triggered by the booms.
There were 16 injury claims in all. An 83-— year-old man claimed he was so startled by a sonic blast while painting his kitchen ceiling that he fell off a ladder. Fourteen-year-old Roderick Tyler was sitting a few feet from a window in his high-school English class when a boom resounded. A large pane of glass, which had been temporarily taped and glued over a broken window to shut out the cold draft, shattered over the back of his head. Doctors took 11 stitches to repair the damage.
Theoretically booms of the Chicago magnitude shouldn't cause much damage, but they did. The air around us normally presses down with a force of 2,116 pounds per square foot. A shock wave, which increases this normal pressure even briefly, can make for trouble. The Chicago booms measured by the National Aviation and Space Agency were relatively weak, ranging from 1.5 to 2 pounds overpressure. But, unpredictably, turbulent air sometimes magnified them. The supersonic transport is expected to create no more than 2 pounds overpressure—not enough, hopes the FAA. to shatter previously cracked windows (5 pounds needed), to knock bric-a-brac off a shelf (6 pounds) or crack plaster (6.5 pounds).
The supersonic age raises complex legal questions. Authorities say that in the 1970's, when scores of anonymous airline jets may be flying over America at Mach 3, claimants won't know whom to sue for boom damage. The claims chief for one of America's largest insurance companies describes himself as perplexed. "It will be chaos," he predicted. "If the airlines make themselves responsible, they will be eaten alive by claims."
Each relatively short supersonic flight over Chicago has already cost the U.S. Government well over $1,000 in damages, and all the claims have not yet been adjudicated. Over 7,650 written complaints have been made ande, and 2,520 official claims filed. Of these, 995 were disapproved, while 932 claimants have been paid $65,492.22. Some 590 other eomplaints are still pending.
A LOOK reporter saw some of the sonic-boom damage when he accompanied an Air Force claims investigator on his rounds in the Chicago area. "Most people are honest," said T/Sgt. Maylon Johnson. "But they may not have looked around their houses in vears and noticed wear and tear. After they hear booms, they suddenly see cracks and assume that the planes caused them." | Sergeant Johnson's main tool is a pocket knife with a long, thin blade. The reporter watched him probe with the knife inside plaster cracks on the walls and ceilings of a 70-year-old apartment house near the Stock Yards. The landlady there told him: "It felt like a big, heavy stove fell on the floor above whenever a jet went by." The sergeant, standing on a ladder. said nothing as his knife dislodged some debris from a wall crack. Outside the house, he said. "This is pretty flagrant. The cracks were there when the apartment was painted last about eight years ago. Maybe one of the dozens of cracks we saw was caused by a boom. The lady wants her whole house redecorated."
The sergeant's next call was at a South Side house. where a woman showed him a gas hot-water heater lying on the ground out back. The tank was badly rusted and dented. "Our tenant heard the water hissing out of the tank right after a sonic boom." said the woman. "The glass liner was cracked. It's only a vear old." The sergeant said nothing until he got back to his car: "That heater looks like it's 10 years old."
Major Robert Atwood, one of the claims officers in Chicago. believes much apparent damage is due to natural causes. "Take television tubes." he said. "Evert day in a metropolitan area of four million people, you can count on a couple hundred picture tubes burning out. If this happens shortly after somebody hears a sonic boom. vou can't convince him a plane wasn't responsible."
Reactions to a boom's sudden noise vary. A LOOK editor stationed in Chicago was invariably startled for the split second that a sharp double boom-boom resounded. After a particularly loud boom shook his bedroom walls, he notedl: "It feels as though a sledge hammer has hit the house a ssharp blow, twice in rapid succession. The walls rattle, the windows rattle, the storm doors downstairs rattle. A boom this loud would certainly wake me up at night."
According to Air Force magazine, a halfpound boom sounds like thunder, and a l-pound boom is like "the loudest sound heard in a boiler factory.'' Gordon M. Bain, FAA deputy administrator for supersonic transport development, says: "People react to the boom like any new type of noise. but the great majority will adjust." Bain admits that booms may disturb some sleepers, but he believes that they will adapt to this noise, "just as they have to the roar of a passing train." To make sure, the FAA soon intends to test the reactions of sleeping persons in some American city. Bain says that he currently holds no great hopes for lowering the boom's intensity. He is encouraged, however, by experimenters' theories that changing the jet's design may cut down on the pressure wave. There is also a possibility, he adds, that the great length of the supersonic transport will produce waves whose frequencies won't affect buildings as much as the waves from today's smaller planes.
Big cities will be spared the worst of a supersonic transport's takeoff noise, Bain feels. Planes will climb at less than full power, since their engines are designed for the tremendous capacity needed to accelerate to supersonic speedls. By the time the pilot turns on full power, the aireraft will be 100 to 150 miles away from the airport and 40,000 feet high. The planes will take 12 minutes to reach supersonic speeds, and this will be the noisiest part of the flight, with a 2-pound boom. At cruising speed. 70,000 feet above the ground. the boom will drop to 1.5 pounds. When a jet becomes lighter after burning up some fuel, it will produce only 1.3 pounds of boom for the last two thirds of the flight. Before starting their descents about l00 miles from the airport, the planes will slow down to quieter subsonic speeds.
The FAA says that in two major tests it found no evidence that booms still prove unacceptable. either because of noise or damage. Oklahoma Citv last year underwent 1,253 booms--eight a day—for six months. The FAA had engineers examine nine rented houses after each boom for signs of damage —and they found none. But an FAA advisory eommittee commented that although a boom may not be strong enough to shatter glass, repeated booms may result in nails gradually popping, paint gradually peeling off, wall covering tearing and cracking of plaster . . . " There are 4,793 formal claims for damages. of which 262 have been so far settled for $17,330.74 and 4,485 have been denied.
Most Oklahomans adjusted to the bangs, reports the FAA. although telephone complaints ran from 192 to 1,711 a week. The National Opinion Reseach Center of the Universitv of Chicago was hired to interview 2,033 residents during the six-month test. At first, only 10 percent were greatly bothered by the booms. said the researchers. But "at the end . . . about one fourth of all people felt they could not (underlined) learn to accept the booms."
Earlier this vear. the FAA tested the effect of 1,494 booms upon a small "village" it built on the New Mexico desert at White Sands Missile Range. Pressures ranged up to 20 pounds. with 680 successivessive booms at.5 pounds. It pleased the FAA that "moderately severe" damage did not occur much under 10 pounds. It also pleased the agency that 2,000 chicken eggs hatched in an incubator despite the incessant booming.
An aviation authority who opposes development of a supersonic transport has warned that pilots will not be able to avoid occasional "superbangs" perhaps five to ten times more powerful than usual. The authority, B.K.O. Lundberg, director general of the Aeronautical Research Institute of Sweden, says, "Thus, if the average intensity is allowed to be 1.5 pounds per square foot. booms will frequently damage buildings, break windows and shock people."
Congressman Pucinski agrees. He has introduced a bill that would forbid a civilian supersonic plane from producing over a 1..5 boom. "It's time we act now, and not 10 years from now, when we will be told that sinc e the nation has invested a billion dollars in developing a supersonic transport, we must learn to put up with the noise."
"We put up with a lot of things nowadays," says Thomas Whisler, professor of industrial relations at the graduate School of Business of the University of Chicago. "In our cities. we put up with traffie jams, air pollution. erime and dirt. I fear that the sonic boom will be just another inconvenience of the 1970's."