ABS
In the 70s, a German forest ranger made an interesting discovery – caught in an avalanche, he owed his survival to the game he was carrying on his shoulders, since the latter allowed him to remain on the surface of the snow. Experiments with voluminous canisters and balloons followed. The idea for the avalanche airbag was born.
In 1980, Peter Aschauer acquired the patent after a first-hand avalanche experience. He founded the company ABS Peter Aschauer GmbH and started to develop a system that allowed avalanche victims to gain a sufficient increase in volume within seconds, without obstructing their ability to move.
Think of an avalanche as a mass in motion. It consists of vast quantities of tiny snow crystals, which start rotating as they slide downhill. As a result of this rotation, all objects with a volume greater than the individual snow crystal are automatically pushed up towards the surface. This is called the "segregation process". Close to the surface, however, the force of rotation declines and with it the lift. Here it is important for the skier's volume to be at least equal (for the same mass) to the volume of the snow in the avalanche. The snow in a loose snow avalanche in the middle of winter has a volume that is 2.5 times greater per kilogram than the volume of a human being. In hard figures, one kilogram of loose snow has a volume of about 2.5 liters. One kilogram of human being has a volume of 1.03 liters, in other words just over a liter. So if a person weighs a total of 100 kilograms, he or she would have a volume of 103 liters. 100 kilograms of avalanche snow in the middle of winter, however, has a volume of 250 liters. To ensure than a person will float on top of the avalanche snow, an extra volume of at least 150 liters is required.
The ABS avalanche airbag is designed for these extreme conditions. It has a volume of about 170 liters, more than enough to make up the difference for a skier weighing 100 kilograms. This prevents the skier being buried/reduces the burial depth, multiplying the chances of survival. Put simply: the lift generated by the rotation of the snow crystals brings the avalanche victim up to the surface. The airbag provides the missing volume and prevents the victim sinking back down into the snow.
(For information: The lift generated by the rotation of the snow particles is also the reason why only about half of all avalanche victims are buried. Through sheer good luck, at the moment they are raised to the surface, they happen to be pushed out of the avalanche flow because of the terrain or for some other reason, avoiding burial in that way.)