May 24, 2007

MY EARLIER POST ON THE AIR-POWERED CAR led a lot of readers to write with questions about crashworthiness. Reader Hank Bradley wrote: “I too lust after that Air Car. It’s exactly right for urban conditions. HOWEVER: with a tank full of air at 4350 psi behind your seat, you’d better consider the effects of a collision, say one that pierces that tank with a piece of metal with several thousand pounds of auto behind it. If your car didn’t suddenly simulate an Iraqi car bomb, it may elect to simulate a jet plane, or at very least provide you with spontaneous ejection seats for you and the whole family.”

I don’t know how dangerous it is — a gas tank is potentially explosive, too, after all — but the likelihood is that these things will appear first in places like India and China, where neither the government nor consumers care as much about safety. And from the standpoint of oil consumption and greenhouse emissions, early introduction in those places is actually better, since (1) oil and greenhouse emissions are fungible; but (2) the automobile market there is growing much, much faster than in Western countries, and consumers are more interested in urban commuter vehicles than in Interstate / Autobahn cruisers.

UPDATE: Matt Sullivan, who wrote the air car piece for PM, emails:

Just checked out your interesting back-and-forth on the air-powered car. Thought I’d give you the lowdown on the air tank safety–an important part of this innovation that I couldn’t fit into a tiny story for the magazine.

The tanks are actually very safe, because MDI (the company that makes the car) has developed an explosion-proof carbon fiber compressed air tank. It’s so non-flammable, in fact, that Airbus has contracted MDI to build the
carbon fiber tanks for their planes. More here (link) and video here (Link), and MDI’s spokesman told me

“We’re really going to try to optimize the technology because the air tank is one of the major things–one of the major innovations–in the car. We’ve really focused on having the best kind of air tank because, obviously, in case of accidents, we can’t afford having any problems.”

And Tobias Buckell notes that a lot of people have an exaggerated idea of air tanks’ explosiveness, based on the movie Jaws. He notes that “Mythbusters”, er, exploded this myth a while back:

Here’s the mythbuster link:

I know you scuba dive from reading your blog (as did I when I lived in the Caribbean) so you’ll know the average air tank is pressurized at 2-3,000 PSI, which is only looking to be about 1,000 less than the air car, so this not all that different from handling scuba equipment.

Secondly, one would expect engineers to put a simple crumple zone around the pressure tank as well.

So no blowing up, crumple zone, and according to the mythbusters episode here’s what happens when you shoot a dive tank:

“When the tank was punctured by a bullet it simply decompressed quickly, causing it to fly around like a compressed-air rocket. The team was only able to make the tank explode in the end by using explosives.”

So the car might get shoved around a bit, but depending on how much air, how bad the crash, or if there is no crumple zone.

Frankly, I’d rather sit on compressed air than a fuel tank!

Yeah, gasoline’s pretty explosive.

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