history of airbags

While the initial concept for many pieces of automotive equipment grew out of the early days of automotive history, the idea of the airbag did not surface until the early fifties. As with many good inventions, it begins with a good story. John W. Hetrick, a retired industrial engineer, was out for a Sunday drive with his wife and 7-year old daughter Joan in 1952. Driving a 1948 Chrysler Windsor as they tooled down the road just outside Newport, Rhode Island, the three sat together on the bench seat, a happy fifties family. Just after they crested a hill, suddenly and quite unexpectedly a large boulder appeared in the road. Hetrick threw on the brakes and veered into a ditch. As he did so, both his wife and he instinctively threw their arms into the air in front of their daughter— to shield her from hitting the dashboard. After their nerves settled and they found that no one was hurt, Hetrick found himself still marveling at the close call.

When they reached home, Hetrick went right to the drawing board. He had been a naval engineer and as he thought about some way to shield passengers from a car's sudden stop, an event from his earlier days replayed itself in his mind. In 1944, as he set about repairing a torpedo there had been a sudden release of the compressed air that powered the torpedo, resulting in instant inflation of its canvas cover. The torpedo shot to the ceiling and, understandably, made quite an impression on the young engineer. Patented in 1952 (# 2,649,311), Hetrick developed a "safety cushion" for cars, the forerunner of today's airbags. His design included an under-hood tank for compressed air and front passenger inflatable bags situated on the steering wheel, the glove compartment, and the middle of the dashboard. For rear passengers the airbags were on the back of the front seat. When a spring-loaded weight sensed a quick deceleration, it opened a valve in the compressed air tank and the bag inflated. Hetrick didn't have the funds to develop his idea further, though. He wrote to the big car companies to interest them in his invention but got no response. It's worth noting, however, that both Ford and GM started working on an inflatable restraint system in the late 50's. They determined that for an airbag to be effective a sensor would have to detect a collision accurately and reliably, and the airbags would have to inflate within milliseconds. The Hetrick sensor was not refined enough and his compressed air idea simply not fast enough to meet the bill.

German inventor Walter Linderer got his German patent (# 896312) for a similar idea about the same time. In his inflatable cushion system, however, the compressed air would be released either by an impacted bumper or by the driver himself.

Innovations in the airbag continued into the sixties when Yasusaburo Kobori, President of the Good Idea Center in Tokyo, demonstrated an inflatable restraint system in Detroit (1962). Carl Clark was thinking about airbags, as well. Head of the Life Sciences Division of Martin's (later Lockeed Martin) Engineering Department in the early sixties, he began working with the idea of airbags to protect astronauts if a space craft crashed. Perhaps recalling stories of WWII fighter pilots who inflated their life vests prior to a crash, he developed a system known as the Airstop Restraint System—which he later tested as an automotive restraint system. It utilized reusable airbags mounted in front of the chest, in front of the feet, and under the seat, inflatable seats, and pressurized air canisters to inflate them. A radar system could detect a coming crash and inflate the bags before impact. Though cars did not come equipped with radar systems, of course, in 1966 at an Iowa conference Clark showed a sketch of his safety car system, promoted the advantages of airbags, and warned of their possible dangers to children. He also testified before Congress, included an early reference to side airbags, and helped legislators determine they wanted to learn more about the efficacy of an airbag system. Clark was definitely a true believer, so much so that at his death in 2006 it was reported that he had been at work on bottle-sized airbags to be embedded in under garments for the elderly to prevent hip fractures.

The first to score a major breakthrough with sensors for airbags was Allen Breed, a former RCA engineer. About 1967 he invented a $5 electromechanical sensor that was safe and reliable. He also secured U.S. patent #5,071,161 on airbags that used two layers of fabric and were vented in such a way that after a passenger came into contact with the airbag, some gas was allowed to escape, providing a safer, less rigid cushion. (Note: In 1987, he formed Breed Automotive to market his safety systems.)

After General Motors had come to Talley Defense Systems (known for its work on propellants for fighter ejection seats) asking for an alternative to the use of compressed air, chemist John Pietz delivered. In 1968 he began using a nitrogen-generating, non-toxic solid propellant--sodium azide and a metallic oxide. That system took up less space than earlier systems but because sodium azide is toxic when ingested in large amounts, its use did little to win converts to the idea of airbag safety. Still, it beat other early ideas hands down. Reasonable attempts were made to use nitrogen, Freon, and carbon dioxide—but there was at least one more adventurous experimenter who used gun powder to heat Freon, producing poisonous phosgene gas which had been used as a lethal chemical weapon during WWI.

Ford meanwhile had approached Eaton, Yale, and Towne, Inc. for assistance, and Eaton invested several million dollars in developing car airbags. Scientist Charles Simon produced an "Auto-Ceptor" air-pillow system, which was ready for rollout by 1971. A sensor was mounted on a car's firewall and, in a crash situation, it activated in 40 milliseconds and sent a signal to the detonator that released nitrogen (pressurized at 2500 psi) into urethane-coated woven nylon airbags. In 1969 Ford demonstrated its ongoing work on airbags. When a team of Ford engineers went to Washington to show the Department of Transportation what they'd been working on, they pushed a button—and (can you guess?) nothing happened. Some innovation. When Henry Ford II heard of the debacle, he was infuriated. Saying he didn't want a Rube Goldberg device in his car, he ended the program— at least temporarily.

Even though car makers had been actively investigating airbag systems, they were not altogether satisfied with the results they saw. The cost of adding airbags, customers' disinterest, and potential liabilities facing them if the airbags failed kept them from moving forward. But the U.S. Government was beginning to become more involved in car safety issues. In August 1966, the National Traffic and Motor Vehicle Safety Act was passed giving the federal government power to regulate car safety. While Henry Ford II memorably said the requirement for lap and shoulder seat belts would force his company to close its doors, few were listening. Roughly a year later the National Highway Traffic Safety Administration (NHTSA) announced a requirement that cars have seat belts by January 1, 1968. When, in 1969, the government proposed passive restraints in cars, largely to protect passengers not wearing seatbelts, GM warned that children sitting too close to an activated airbag could be seriously injured— or worse.

Despite repeated efforts to prevent or delay the mandate for airbags— and questions about what would happen to those who wore glasses or dentures or smoked a pipe— car manufacturers knew the introduction of airbags or some other passive restraint couldn't be far away. Events of the seventies made that expectation a reality. Because seat belt usage was still low then (about 15% used them), some thought that airbags could replace seat belts. It didn't take long, however, for investigators to conclude they could not replace belts, only supplement them.

In 1970 the NHTSA ordered passive restraints for the 1974 model year. Car makers could either install automatic seat belts or airbags; car makers opposed either option. Ford, however, did build an experimental fleet of cars equipped with airbags and was the first manufacturer to say it would introduce airbags in its 1971 line of full-size Lincolns and Mercurys. Their chief body engineer Stuart Frey, however, nixed that idea. He argued there were still poor performance issues, tests on child-size dummies showed injuries were likely, and windshields often broke when airbags were activated. While insurance companies favored the use of passive restraints, car manufacturers continued to oppose them and sued to challenge the rule requiring them.

Armed with complaints and not content to sit and wait for the administrative process to work things out, in April, 1971, Henry Ford II (chairman of Ford) and Lee Iacocca (Ford's president) met with President Nixon in the Oval Office. They related to him that the new safety regulations would put the U.S. at a competitive disadvantage in competing with Japanese car makers and would harm the U.S. economy. Ford's leaders claimed they'd spent $240 million in safety research that had resulted in the addition of new safety features— like the collapsible steering column. But they deemed other devices— like the airbag— a complete waste of money. Just three days after that meeting Nixon's Assistant for Domestic Affairs John Ehrlichman called Secretary of Transportation Volpe to tell him Nixon wanted him to put the brakes on a passive restraint requirement. Soon thereafter a revised ruling, one agreed to by car manufacturers, called for a three-year delay from the '74 models to the '77 ones. When Volpe faced significant political opposition to the delay, he asked to move the mandate to '76 models. Nixon checked with the Big Three, and got their OK.

With a looming deadline, car manufacturers went back to the drawing board. In 1973, GM offered airbags for use in 1,000 Chevrolet Impala fleet cars for testing. The Olds Toronado rolling off production lines in 1974 was GM's first consumer car to be equipped with airbags, optional at a cost of $225. Among the problems facing GM in developing its airbags were: redesign of the car interior to accommodate airbags, unacceptably high sound levels, and test dummies lacking the variability to test for a range of car occupant sizes. Despite all those challenges, the airbags utilized in the seventies were in some ways superior to those now in use. They included adjustable inflators so that in less severe crashes, the airbags did not inflate as rapidly. They also included a driver knee restraint as well as torso airbag and a front passenger combination airbag that included cushioning for the torso and the knees. Despite those advanced features, the cars came only with lap belts— no shoulder belts.

As Ford and GM continued to test their airbags, they found that they performed well— but with airbag-equipped vehicles seven deaths occurred in accidents nonetheless and one, that of an unrestrained infant, was blamed on airbags. It didn't help, either, that in 1974 closely-held results from a Volvo study made their way into the U.S. debate about airbags. In that study two dozen baby pigs (roughly the same size and weight of children aged 3-6) were anesthetized, situated 4-6 inches from airbags, and strapped into cars going less than 25 mph. When the cars crashed, only three pigs escaped without serious injuries. Most succumbed from serious heart and lung damage.

Still, in 1974, GM (which enjoyed a competitive advantage over Ford in airbag production) began making some Cadillacs, Oldsmobiles, and Buicks with optional airbags. Edward Cole, GM president from 1969 to 1974, had initially wanted to test airbags in 150,000 cars but when the 1973 oil crisis came along and pumped gas prices sky high, it was hard to convince consumers to lay out more cash for safety features. After three years' experience with optional airbags and total sales of a little more than 10,000, GM reverted to type (claiming that safety didn't sell) and dropped the poorly-selling feature.