In a car crash it is most likely that sharp cutting surfaces will be created by broken metal or plastics. This would render air bags useless. Aside from that, many car owners purchase vehicles on the fantasy basis they are getting mach 10 spaceships or military vehicles. Design would be almost impossible to conform to this fantasy with external air bags.

Air bags are to hold the person in place and prevent the person from impacting surfaces inside the vehicle. If the bags are outside, the person inside is still going to flop around. Also, the cost of an air bag is far greater than most damages repaired in a bump shop. Sometimes the vehicle is totalled just because the air bags deployed. In the future, with the new materials being developed called Carbon Nanotubes, this may be a practical idea.

I suppose you could make the airbags out of tear-resistant fabric like kevlar. Also, [junkie], the airbags don't have to be taken away from the interior—both can be in place. The real problem is how the bag would be triggered. If it's only in place to prevent scratches and minor dents, this idea is overkill. If it's meant to shield against midspeed crashes, you'd need to be able to detect approaching vehicles or surfaces. There's also the chance that a rogue airbag could deploy because someone bumped into it, causing serious harm.

I'm not sure this would work the way you envision it. Don't you think the bags would have to be enormous to be effective in a collision over 20 mph? Remember the surface area has to support around 9500 lbs plus the added force of speed. I believe that the super structure of the vehicle would still collaspe/bend/crack even if you could find a material that wouldn't rip on impact. Now what might be worth looking at is if the entire outside of the vehicle was inflatable. If you have an accident all you do is patch the hole and reinflate the panel(s) that were damaged.

We already have airbags built into the exterior of cars. They're just made of steel, and they're called crumple zones. Airbags are not powerful enough to stop that much metal moving at that speed.

I realize this is not what you want (a virtually undamaged vehicle), but the last thing on the mind of your design team when discussing crashes is damage to the car.

I like a full containment seat with a six point harness. I also don't mind climbing over a rollcage (all three of which I've had experience with). Those things need to be designed to not bend as much as possible. The rest of the car should be used for dampening.

Best example of this design principle? Good old motorsports. Top fuel dragsters, formula one, and unlimited hydroplanes all have one thing in common when they crash - the vehicle essentially disintegrates to dissapate enegry in the crash. The driver is left behind in the rollcage.

Research into external airbags,is at an advanced stage for carsand by some manufacturers of trucks, take a look at this website PDFthis needs publicising and companies not currently researching ways to save VRU lives need to be urgently made aware of this site.http://www.aprosys.com/Documents/deliverables/D212AB_updated.pdf