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How quickly airbags of automobiles inflate in automobiles of 2023?

 by  Maryam Hussain

What is an airbag? What was its need?

Since it is neither viable nor it is desirable to build vehicles as strong as armor fighters, it is definitely required that the basic structures must be designed to collapse in a controlled manner in an accident. In 1951, John Hetrick, an industrial engineering technician, invented airbags. An airbag is a safety device that is usually packed in the center of the steering wheel and in the dashboard in front of the passenger seat. An airbag quickly inflates with air or with some other gas during a head-on collision & cushions a car’s occupants from the impact of the collision.

Where is an airbag ergonomic display in driver panel?

Whenever the ignition of the car is turned ON to the first step, then, besides other lights within the driver’s panel, the airbag light should glow ON for a short while and then go OUT. If the airbag warning light keeps on glowing, then this indicates a fault within the airbag operating system and in case of an accident, the fault in the airbag operating system may prohibit the trigger or may inhibit the inflation of the airbag to the required position. So it is recommended to bring the car to the relevant maintainer and get the fault rectified.

What were the four safety features added to the car to protect the driver’s rib cage?

In the safety design of an automobile car regarding the safety of the cabin crew & especially the driver, consideration is always given to prevent the steering wheel from crushing or penetrating the driver’s chest or neck as a result of accident impact. One of these measures was the provision of telescopic or concertina-type collapsible discrete elements in the steering column which had the feature of being collapse of itself and thus played its role of halting the accident progression towards the chest of driver.

The second of these measures was an increase in the area of the hub of the wheel, to reduce the concentrated impact of the steering wheel on the chest of the driver.

The third of these measures was to reduce the hardness of the material of the steering wheel, to allow bending/tilting of this wheel upon contact with the driver’s chest rather than penetrating the chest & ribs of the driver.

The steering wheel also serves to store the airbag & aim it in the right direction at the right time & within the right duration. It should point towards the chin to decelerate both the head and chest (upper torso) at the same time.

The fourth measure is already known to you; a seat belt.

What is the appropriate position of the automobile driver?

The timing of the airbag inflation is critical. According to tests outcomes & recent research, the collision detection time by sensor + resultant airbag full inflation time allows the head and shoulders of a person, in a vehicle traveling at 50 km/h, to travel 5 inches forward to hit the airbag at about 23 km/h with a rebound speed of about 10 km/h.

In order to allow this 5 inches of movement for both the driver and the airbag, the driver should be at least 10 inches away from the airbag before it inflates.

If the driver-to-airbag distance is substantially lesser than 10 inches, the inflating airbag will have an ‘early hit’ and will move the occupant rearward. The result of this could be a dramatic increase in the occupant’s head and/or upper torso rebound velocity.

If the driver-to-airbag distance is substantially greater than 10 inches, there will be a ‘late hit’ on a deflating airbag that is too soft to prevent contact with the hard portions of the steering wheel.

Therefore, it should be clear to all readers that the position of the driver’s head is critical for the proper functioning of the airbag and this discussion should be told or be appropriately communicated to all automobile drivers, to the driving instructors & to the general public.

What will be the probable scene when an automobile gets a collision while its driver already had put on seat belt and the automobile lacked the airbag?

Let us consider the case of driver safety during an accident of a vehicle that has a driver seat belt but no airbag. Research has shown that a belted driver will have facial contact with the steering wheel if the vehicle deaccelerates suddenly; where the sudden deceleration is at about 23 km/h.

Therefore, the airbag must inflate @ deceleration rate lesser than 23 km/h to prevent facial contact with the steering wheel. The airbag inflation triggering point w.r.t sudden deceleration rate should be near about but lesser than 23 km/h but it should not be so low (like 10 or 16 km/h) to avoid unnecessary airbag inflation.

What is the role of chemistry in the design of airbags?

The provision of airbags in vehicles like cars, buses, trucks, & vans, etc. is mandatory to protect the driver and passengers in the event of a head-on collision. Such bags are rapidly inflated with nitrogen gas, which is generated by the rapid decomposition of sodium azide, in the presence of potassium nitrate & silica through the following reaction:

2NaN3 (s) → 2Na (s) + 3 N2 (g)

Where

NaN3    : Azide

KNO3    : Potassium nitrate

Na         : Sodium

N2          : Nitrogen gas

The sodium produced in the reaction is converted to sodium nitrate, a non-reactive salt in ambient & accident conditions, by virtue of KNO3 and silica. When a car decelerates in a head-on collision, an electrical contact is made in the sensor unit. The propellant detonates, releasing nitrogen gas, and the folded nylon bag explodes out of the plastic housing to become a cushion between the cruising vehicle parts & human face, head, shoulders, ribs, and stomach body.

The airbag gets full inflation in about <  0.050 seconds which is an essential requirement because the typical automobile collision lasts for about 0.125 seconds.

Because the driver-steering room is relatively low as compared to that of the side passenger-dashboard room, therefore driver-side airbags inflate with 35–70 L of N2 gas, whereas passenger airbags hold about 60–160 L. The actual volume of the airbag will depend on the moles of nitrogen gas generated during the chemical reaction.

The bag deflates within 0.2 seconds via tiny holes in the bottom of the bag and this meets the requirement to be greater than the collision impact duration (about 0.125 seconds).

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