Modern day automobiles employes many systems like ABS, ESP, ESC etc to keep car safer and safer. Air Bag system is another important safety feature used commonly. The system helps in protecting the driver from serious injury that could be caused as a result of crashing onto steering wheel or dashboard during an accident. True, the seat belts help in restraining driver’s movement forward, but for fatal collisions even seat belt aren’t that effective.
In comes Air Bag into play, basically the functioning of Air Bag could be explained through Newton’s second law basically larger the momentum change, larger the force or impact experienced. The driver’s body lunges forward due to inertia of motion during a collision, but the car has come to a halt hence when the driver’s skull crashes on the steering wheel, the impact is sufficiently large to cause fatal damages.
Hence comes Air Bag into play that inflates and provides a cushion to increase the impact time to lower the magnitude of impact to zero. With this knowledge now let’s look into the functioning of Air Bags i.e. how they work?
The Air Bag system on any automobile has the following mechanisms:
Impact Detection or Trigger mechanism
Bag Deploying or Inflation Mechanism
There is a sensor planted into the car which receives data from the accelerometer. It triggers the bag deploying mechanism when it detects severe change in acceleration, generally it triggers when it detects an impact of magnitude similar to head on collision into a concrete wall at a speed in of 19-23 kmph (12-14 mph). Upon detection it sends an electric signal to bag deployment mechanism.
Now the signal is received by the inflator (device that inflates the Air Bags) it ignites a mixture of Sodium Azide (NaN3) and Potassium Nitrate (NaNO3) which reacts vigorously to produce Nitrogen Gas (N2) which fills in the wrapped up nylon fabric inflating it completely to provide cushioning to the crashing driver.
All of this process takes place fewer than 30 milliseconds as that is time taken by the impact to reach the driver travelling through bumper and other front structures of vehicle. It deflates one second after deployment releasing the gas inside.
An important thing to note here is that the driver is advised to have at least 10 inches (25.4 centimeter) gap between his/her breast and the steering wheel as any distance lower than that might prove fatal because the inflation rate of airbag is very high and it can also produce tremendous impact force.