Ever noticed SRS engraved on your steering wheels, or dashboard? SRS mean Supplemental Restraint System or in layman's language, it is Airbags. For years now, seat belts were the sole form of restraint in any car, helping the occupants from collision impacts. But as the history took shape and many advanced technologies started to be a part of our automobiles, Airbags came into limelight.
In continuation to our safety series, we will discuss in detail about the airbags, its functionality, usage, benefits and disadvantages.
What are airbags?
Airbags are soft pillow like balloons, which come into play as soon as a car gets into collision, at a speed higher than 50 kmph. Embedded in various places, according to the safety standards and impact studies, airbags in their primary form are like balloons without air, which inflates on collision. The first patent of an airbag is dated back to World War II and after many years, appeared in automobiles.
By 1988, all the new cars in the U.S were mandated to have airbags for both the driver and the passenger. The two airbag system was later extended to six and eight airbags system. According to some statistics, airbags have reduced the risk of dying in a direct frontal crash by about 30 percent.
Science behind the airbags
Like any other safety equipment, airbags too are made to minimize the reduce the damage to the occupants, but they only come into action when an impact took place. The science behind the airbags is simple, to reduce the damage to the passengers and the driver of the car, once an accident takes place. The momentum comes into play as soon as a car gets hit.
Momentum is that force, which comes into action when a moving object suddenly stops. So when a moving car gets hit, the immediate result is, the car gets stopped, whereas the passenger still remaining in motion, which leads the front passengers to hit the dashboard or the front window for that matter. The goal of any supplemental restraint system is to help stop the passenger while doing as little damage to him or her as possible.
Following the goals of the airbags, they slow the passenger's speed to zero with little or no damage. The airbags occupies the space between the passenger and the dashboard (primary airbags). Within fraction of seconds the car hits something, the airbags comes into play, by inflating and creating a cushion for the passenger or driver. As soon as the occupants hit the airbag, their speed also gets slow, reducing the risk of injuries.
There are four basic components of an airbag, which help it to reduce the passenger's frontal impact:
1. Bag - The bag in itself is made of a thin, nylon fabric and is kept folded into the steering wheel, dashboard and other places, as per the need.
2. Sensor - The sensors, like in any other system, helps find any change in the standard values. When any collision occurs, an accelerometer records the change, above 20kmph to 30kmph speed, which in turn inform the sensor to inflate the bags.
3. Inflation system - At last, there is a cannister filled with chemical gases, that help the bag to inflate. The cannister reacts sodium azide (NaN3) with potassium nitrate (KNO3) to produce nitrogen gas. Hot blasts of the nitrogen inflate the airbag.
Airbags inflation process
The inflation process, as explained above, has a very simple process, ending with an inflated bag. But that is not as simple as it sounds. The early efforts to develop such a system failed drastically, since the release of the compressed gas posed many questions like - If there was enough room in a car for a gas canister? How the bag could be made to expand quickly and reliably at a variety of operating temperatures and without emitting an ear-splitting bang?
The answer came in the form of a small solid-propellant inflators. What these solid propellants do is burn, burn at extremely rapid pace to produce gases that inflate the bag. How fast you may ask? The whole process happens in only one-fifth of a second, that fast! As soon as the gases reach the fabric bag, it burst out of the dash at speeds as high as 300kmph.
After the airbags have performed their task of preventing any serious injury, they quickly deflate within a second, via small holes in the bag, to create a space for the movement. And all the dramatic effect that is created by those floating powder and all is actually your regular talcum powder, which keeps the bag lubricated inside the dash.
Airbag Safety Concerns
As much as airbags save a person from collision impact, they can be dangerous too. Studies have found that, the more you are close to the airbag, the more is the chance of you hurting yourself. A distance of 10 inches has been determined safe from the airbags, and hence is the use of seat-belts. All the airbags today are connected to the seatbelt and if you are not wearing a seatbelt, airbags won't work.
Also, seat belts are mandatory as the airbags only open after a certain speed limit. So if the collision occurs below that speed, the airbags won't work, and hence seat belt act as a primary safety device. But all these theories and studies nullifies as soon as a child comes into the scenario. An airbag, no matter what, can cause serious injury, or in some cases, death to an infant or child.
Hence rules were made, not to sit children in the front seat. Or if necessary, with precautions like a front-facing child safety seat, a booster seat or a properly fitting lap/shoulder belt, and the seat should be moved as far back as possible.
Location of airbags
While the initial years of airbags were only limited to the steering mounted bags, later years saw the airbags covering the dashboard too, hence saving the passenger's life. But as the technology is advancing, so are new ways coming to mount the airbags.
1. Steering wheel mounted airbags - to save the driver.
2. Dashboard mounted airbags - to save the passenger.
3. Side airbags - Airbags placed in doors/ door pillars, to save the occupants from the side impact.
4. Head airbags - To save the occupant from any neck and head injury.
5. Curtain airbags - Another option for head protection in side impacts can be the curtain airbag.
6. Bonnet airbags - Not relative to the occupants, the bonnet airbags are meant for the pedestrians in the event of any frontal accident.