Handy things to know
4 Responses to “Handy things to know”
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December 14th, 2006 at 5:25 pm
Good post, but I not sure if the BATFE factored in overpressure from the intial blast. While in the first Gulf War I found bodies on the Kawaite highway that had not a single mark on them. Found out later that they died from suffacation from the overpressure sucking all of the oxygen from around them.
December 16th, 2006 at 4:57 am
The lethal air blast radius is much smaller. I didn’t post that information because it can be used for offensive purposes (how big of a bomb do I need to kill someone if I can get ‘this’ close to them?).
The lethal air blast doesn’t kill by removing the oxygen from the area. You can easily survive a minute without oxygen in the air and a bomb isn’t going to keep the air away for that long. In a closed area a fuel air explosive can do that sort of thing because it consumes oxygen.
In open space the lethal air blast radius is because the overpressure ruptures the lungs and you then suffocate. It’s pretty interesting… there is a very sharp transistion zone you pretty much either fully recover (well, maybe not your hearing) or you die. You lungs either burst or don’t. Someone just a couple feet closer dies in a few minutes and the first person walks away dazed with bleeding from the ears.
That’s the air blast effects. Death from flying objects and from you being thrown through the air have different radii and probability density functions that depend on more variables.
December 16th, 2006 at 11:55 am
That’s interesting. How much protection does cover afford in these situations? For instance, can you be closer if you’re in a car? Would, say, being on the other side of a hill give any protection from the blast front? And is Minimum Safe Distance the distance at which you don’t have to worry about shrapnel flying through the air?
December 17th, 2006 at 2:37 pm
The minimum evacuation distance is outside the radius where you would be hurt by direct blast effects. If you were downstream from the dam being blown up you could still be in trouble. The same goes for being downwind of a toxic chemical facility.
Yes, cover helps a great deal. One of the biggest threats is flying objects. But within the “lethal air blast” radius it doesn’t matter unless you are in a nearly airtight container able to resist, in the neighborhood of, 200 psi pressures. A car, a culvert, or a mound of dirt won’t protect your lungs from rupturing from the sudden over pressure. You can probably work out some of the distances from here but I’m not going to explicitly give it away.
You also need to worry about falling glass. If you are on the street and the building beside you has it’s windows shattered two (or twenty) stories up then you can get sliced in half. The minimum evacuation distance takes this into account.