Airbag technology through the years.
Once upon a time, airbag sensors were relatively simple switches that detected sudden changes in an automobile’s velocity. These two switches would ‘close,’ altering the designated path of an electrical current so that it would then flow to the air bag modules. The air bag would then be deployed.
The mechanisms in place today are far more sophisticated, however. Firstly, binary switches have been replaced with electronic sensors that actively measure a vehicle’s deceleration. This information is processed mathematically and contrasted with pre-programmed results from crash tests. If the new value indicates that the oncoming potential accident is more severe than the results of the crash tests, the electrical current will be released to the airbag modules.
The manner in which the electrical current operates hasn’t changed, of course: The current heats up what’s known as a “squib” within the inflation device. The squib itself houses a container of chemically explosive material, and inside of that container is a tiny filament that heats up enough to start burning the chemicals. One of the chemicals burnt is called sodium azide, which will produce nitrogen gas and various byproducts. (In some cases, a pressurized gas—often a combination of argon and helum—will be used instead of sodium azide. The result is the same.) The gas produced will rapidly fill the airbag, which is folded over the inflater.
The pressure of the expanding airbag will force it through the plastic casing. The expansion will cease once the airbag has reached its maximum size. Driver airbags typically take a round shape that’s slightly larger than the steering wheel, and between 12-20 inches thick once filled. Passenger-side airbags are anywhere between 2-4 times larger than driver-side airbags, and can be as wide as 3 feet. They require more force in order to make sure that such a larger airbag is inflated properly in the same amount of time as the driver’s airbag. The entire process of the automobile sensing a collision and then inflating the airbags takes about one-tenth of a second. If a person is pushed against an airbag, the pressure will cause gas to be released through tiny holes in the airbag’s frabric.
Side airbags, or rollover airbags, utilize a similar process. A sensor built into the structure of the car—often the front door—will react to rapid deceleration as well as the possibility of the vehicle rotating during a rollover crash. The electrical current travels to the side and/or rollover airbags, causing them to deploy. Side airbags will break through the plastic casing located either along the side of the seat closest to the door, or a panel along the side of the automobile, and are much more flat and usually smaller than frontal airbags. Rollover airbags are also very flat, though they cover the side of the vehicle as well in order to protect the passenger or driver from injury as well as the possibility of being thrown from the vehicle.
Nonetheless, the modern airbag system is complex and that complexity can lend itself, at times, to error. A defect in any of the machine’s parts can lead to a malfunction of the entire system. In some instances, an airbag will deploy when unnecessary—during a minor collision, for instance—and the results are often catastrophic for the driver or passenger. Adversely, there have been times wherein an airbag will not deploy even when the recorded, sudden deceleration should have triggered the airbag’s release.
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