Every year, many cars go off roads and docks into rivers and harbours. Others are swept away by floods. Tragically, sometimes people die in these incidents.

So, put six airbag cartridges round the perimiter of the vehicle, in the front and rear bumpers, and under the wheel arches. Put mulitple water sensors inside the car to fire the airbags when there's a significant amount of water inside. The airbags should be sized so that the car and a full load of passengers will just about float on any four of the six bags.

If the car ends up in water, it will float, at least for a while, giving the occupants time to escape.
-- 8th of 7, Jun 19 2002

(?) shafi shaficet12@gmail.com
[shaficet12, Feb 04 2009]

I think I'm going to settle on aftermarket retrofit kits of escape hatches secured with explosive bolts, both floor and roof Integral_20Side_20A..._20Window_20Breaker
So that option ought to come with this package. [normzone, Feb 04 2009]

Well if the car flipped over, it would make a good glass-bottomed boat, though I wouldn't want to be in traffic in a convertible caught in a sudden downpour.
-- FarmerJohn, Jun 19 2002


and maybe the same airbag can be used as a cushion for collisions. If the giant airbag inflates around the car, then maybe that can save people from car to car collisions. But i don't know how the airbag would know when to inflate. i guess the driver can push an "inflate" button when he thinks he's gonna crash.
-- consumer, Jun 19 2002


Like FarmerJohn, I believe the car will simply flip over with air bags as described. Which will precisely *not* give the occupants time to escape.
-- DrCurry, Jun 20 2002


FarmerJohn, DrCurry: As long as the attachment points on the car are above its centre of gravity, it won't flip. The airbags would tend to fold up around the car, allowing it to settle slightly for stability, but not actually sink. Remember, these bags deploy from the sides, front and rear, not from underneath. Buoyancy will force them upwards.
-- 8th of 7, Jun 20 2002


"The airbags would tend to fold up around the car..."
Which might make it tough to get out of the car. Unless you have a sunroof.
-- phoenix, Jun 20 2002


If the airbags were mounted near the top of the car, you would quite probably end up with a situation where the airbags were above water, but the car was not.

There is an additional risk in that when a car goes into water, it will tend to be near a dock, river bank, bridge, etc, which will quite likely interfere with the inflation of a large airbag. This will possibly cause the car to tilt sideways or get caught up, or puncture the airbags.

A car full of water will weigh more than 5 tonnes (remember, one cubic metre of water weighs a tonne). You're going to need a lot of airbags to lift that any distance above the surface. Not to mention a lot of compressed air. Care to do the sums, [8th of 7]?
-- pottedstu, Jun 20 2002


[pottedstu]: The point is to inflate the airbag before that much water finds its way into the passenger compartment. Even so, all that water effectively weighs nothing while at or below the external waterline, so in fact very little air bag volume is needed to raise that mass ever-so-slightly above the waterline. The internal water, being fluid, will tend to leak back out of the car. Thus the car will rise slowly and continue to drain until just enough of the car's frame and occupants' bodies are above water to exactly balance the buoyancy of the air bags.

The air bag material might need to be different, though. More like a vinyl-rubber raft than the thin stuff deployed for crash protection. Otherwise the gas would leak out too quickly to be much help.
-- BigBrother, Jun 20 2002


Pottedstu: OK, then.

Let us assume that the laden weight of the car is 1500 Kg; 1000 Kg for the vehicle, and 500 Kg for the passengers and luggage. On entering the water, the vehicle partially floods, triggering the airbags. If we assume that the vehicle is not water tight, we can negelct buoyancy; the water level with equilibrate quite rapidly. In fact, the more the car leaks, the better. So we have to support 1500 Kg by buoyancy. This involves displacing 1500 litres of water (assuming fresh water at 15 Centigrade, and taking the density of air as negligible compared to water) - Archimedes. Further, assume two of the six airbags are compromised. Therefore 1500/4= 350 litres or .35 of a cubic metre submerged, which isn't very big. It's a sphere less than a metre in diameter. (V= 1.33 x Pi x R ^3).

You don't have to support the whole 5 tonne weight of a water filled car ..... if all the airbags work, it will actually stay quite a long way out of the water.

Phoenix: Yes, the sunroof would be the best means of egress. The airbags would be mounted along the periphery at bumper level.
-- 8th of 7, Jun 20 2002


u have said about the weight of the vehicle lifted by the airbag when the vehicle starts sinking....here u have said that the air bags wil make the 1500kg vehicle float..one important thing should also be considered,i think...that is the fluid pressure at a certain depth wil also add the vehicle's weight..so the air bag wil have to be made to carry both these weights..Also the fluid forces the inflation of airbags....so the gas inside the airbags should be at high pressure. u discussed about the case when the vehicle is not fully sunk..i am curios about the fully submerged case.
-- shaficet12, Feb 04 2009



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