What are airbags, why do we need them? How they are triggered and many more questions for all of them find answers in the text below.
Invention of airbags
On 5th August 1952 American inventor John W. Hetrick filed for an airbag patent. Airbag patent was granted #2,649,311 by the United States Patent Office on 18 August 1953.
Why do we need airbags?
First, it’s important to understand why we need airbags. Inertia. If something heavy is moving at 60 miles an hour, its momentum and mass work together to keep it going that way. If your car is going 60 miles an hour, everything inside it, including you, is going 60 miles an hour as well. So if you hit another car with enough force to reduce your speed a lot, every part of your car is going to exert its inertial force. Just because the frame of the car has stopped does not mean that everything between you and the groceries in the back seat don’t plan on maintaining speed. Sure, seatbelts are good for stopping your chest from hitting the steering wheel, but your head, and arms are liable to snap forward and bang against the wheel even though your torso is held in place.
How airbags are triggered?
It takes 50 milliseconds for you to hit the steering wheel in a crash. Meaning airbag deployment must go down even faster than that. Your car has to be able to detect when a potentially deadly crash is happening. You don’t want your airbag deploying every time you hit a pothole or get in a fender-bender. Your car has an accelerometer — several, actually, in case one fails or goes off by mistake — that detects sudden, rapid changes in velocity. In one model, a ball bearing is normally held in place by a magnet, but in a crash, it comes flying free. And it flies right into an electrical circuit that tells the car’s computer to deploy the airbags.
Airbag deployment
Airbags don’t just fill with gas like a balloon blowing up. That’d be way too slow. The gas that fills airbags is actually produced by a chemical reaction. The classic example is sodium azide, which is stable until it’s heated. In a crash, a small explosive or heating element called a squib goes off and ignites the sodium azide which decomposes quickly to nitrogen gas and sodium metal.
That sodium metal could react with water in the air to produce corrosive sodium hydroxide. Airbag manufacturers include some other compounds to react it into sodium oxide and alkaline silicate instead. By the way, this technology we described is a little outdated. And accelerometers have changed with the times, too. They’re a lot more sophisticated than the ball bearing thing.
Meanwhile, the nitrogen gas is totally harmless, being the main ingredient in. Just a small handful of sodium azide can produce 67 liters of nitrogen. That volume of gas creates enough pressure to fill the airbag in less than 40 milliseconds. When your car hits something, it stops, but your body keeps moving forward. And if it keeps moving forward right into the steering wheel or dashboard, that’s bad news for you.
So the airbag is there to slow you down more gradually than a steering wheel would. But this rapidly inflating cushion isn’t actually pillow soft. The front face of the airbag moves toward you at between 150 and 250 mph. And if you were to hit it while it was still inflating, that might be almost as bad as hitting the steering wheel.
To properly slow you down, an airbag has to have blown up already when you hit it. Between 1987 and 2015, frontal airbags saved 44,869 lives.
That’s a summer evening at Dodger Stadium’s worth of people.
