How does a blast wave kill you?

[Michael Lewis]

I was reading Pegasus Bridge and it gave a report where a group of Brits were killed by the blast wave of a shell. The ghastly thing about it was that they were playing cards in a foxhole and were basically frozen in that position. My cousin who's in the army said that a .50 machine gun can kill you if it even hits a foot away from your head from the shock wave.

How does the blast wave kill


Thanks,

Michael

[Tegyrius]

As I understand the theory, an explosion has three different ways to kill you. I'm probably not using the proper medical terminology here, though.

The first is penetrating or blunt trauma from debris propelled by the explosion, even if the warhead or device isn't specifically designed for fragmentation (though this falls under 2.2 and Reflex's fragmentation damage, not blast damage).

The second is the kinetic effects of the shock wave compressing soft tissue, particularly in the torso's vital organs, which can tear that tissue and/or the embedded blood vessels. This effect may include a secondary possibility of brain or organ damage caused by compression-induced spikes in fluid pressure in the circulatory system.

The third is acceleration of the body (i.e. being propelled away from the explosion's epicenter) causing impact damage to the brain as it bounces around the inside of the skull, just like any other source of cranial acceleration trauma.

Also, I call shenanigans on the .50 caliber rumor until I see scientific proof otherwise. Yeah, it'll kill you if it hits a foot away from your head - if that "foot away" puts the impact in your torso. Hitting scenery a foot away I don't think it carries enough energy to generate that sort of overpressure in air.

- C.

[stg58fal]

Pressure. But a .50 isn't going to do it. The muzzle blast is impressive, but the projectile isn't big enough to do all the things it's said to do (tear your arm off if it comes within a foot of you, for example).

[Tegyrius]

Pressure. But a .50 isn't going to do it. The muzzle blast is impressive, but the projectile isn't big enough to do all the things it's said to do (tear your arm off if it comes within a foot of you, for example).

Yup. If that were the case, accuracy wouldn't matter with an M82.

- C.

[stg58fal]

debris propelled by the explosion

the kinetic effects of the shock wave compressing soft tissue

acceleration of the body

He said it better than I did. I was only thinking of the example Michael gave, i.e., how the Brits in that hole got aced by the explosion.

[HorseSoldier]

Yeah, mythology on the fifty cal. There is a lot of that, owing I think to the 50 cal being about the biggest, most powerful weapon an individual can direct lay and open up on people with.

The pressure wave from a blast is pretty under appreciated in Hollywood, etc, but can be absolutely devastating as noted up thread.

[Grimace]

Having been on the receiving end of blast overpressure, I can say a couple things with assurity.

First, the blast somehow manages to daze/stun you temporarily. I'm guessing it has something to do with what it does to your head. I don't know if it's from the sudden and intense change of air pressure or not. I didn't hit my head against anything, but the helmet I had was blown off my head from the blast.

Second, I felt "funny" for the next five minutes. I was partially protected by a solid object, but half of my torso (and head) was exposed. I felt as though someone had bounced on my chest a couple three or four times. It didn't *hurt* per se, but I felt as though my heart was beating differently than it normally does. My breathing was also slightly disrupted. I recovered my breath much, much faster than I was able to get rid of the "funny" feeling in my chest.

I could imagine if you were closer to a big enough concussive blast, it could probably have an adverse effect on your heart, and actually cause it to stop. I don't know about freezing your body, but I could see a blast killing a person by stopping their heart.

To my knowledge there are basically three methods, as Tegyrius mentioned, but they're slightly different than what he mentioned. Trauma from impact of the directly propelled object or from flying debris initiated by the object, concussive damage that damages the brain or internal organs, and shock caused by either trauma or blood loss. Considering that some people die from "blood loss" when they lose such a small portion of their blood, but go into shock from the blood loss, shock plays a fairly important and major role in causing death.

[Tegyrius]

Having been on the receiving end of blast overpressure, I can say a couple things with assurity.

First, the blast somehow manages to daze/stun you temporarily. I'm guessing it has something to do with what it does to your head. I don't know if it's from the sudden and intense change of air pressure or not. I didn't hit my head against anything, but the helmet I had was blown off my head from the blast.

Could have been concussion from your brain sloshing back and forth inside the skull as your head bounced back, could have been overpressure effects on your ears. Anatomy & physiology isn't my strong suit but I'd look to those first as possible causes.

I could imagine if you were closer to a big enough concussive blast, it could probably have an adverse effect on your heart, and actually cause it to stop. I don't know about freezing your body, but I could see a blast killing a person by stopping their heart.

Yeah, I'd expect the body to fall over in such a case. I mean... blam, dead, yeah, but rigor mortis ain't that fast.

To my knowledge there are basically three methods, as Tegyrius mentioned, but they're slightly different than what he mentioned. Trauma from impact of the directly propelled object or from flying debris initiated by the object, concussive damage that damages the brain or internal organs, and shock caused by either trauma or blood loss. Considering that some people die from "blood loss" when they lose such a small portion of their blood, but go into shock from the blood loss, shock plays a fairly important and major role in causing death.

Yep. I can see the shock and blood loss (whether it's external or internal bleeding) coming from the tissue damage I mentioned. Also, I do think the compression wave damage to organs and the deceleration trauma from being flung and hitting the ground/scenery are technically separate mechanisms of injury, though they may well have the same net effect. Still, it looks like we're mostly in alignment.

I will caveat (and should have done so earlier) that I'm speaking academically, not from personal experience. This topic came up in a medical course I took last summer, and I went back through my notes and the class handouts to verify my recollections, but I have neither firsthand experience nor extensive formal training with blast injuries. YMMV.

- C.

[raketenjagdpanzer]

A friend of a friend was in an MRAP that hit a mine on Route Irish outside of Baghdad. No injuries, nothing. Started having serious emotional problems that were ascribed to PTSD, so they gave him a fistful of xanax to take on a daily basis and a desk job (still in country) and he was still having issues. Got rotated home, VA kept sending him for "talking therapy" and more and more and stronger and stronger antidepressants until finally he went to a civilian hospital and got the full MRI the VA insisted he didn't need and found out lo and behold his pineal gland had gotten detached. It was still there and still connected but it had been pushed around and damaged while nothing else in his skull had been. Left him prone to fits of rage, impotent...just a fucking mess.

So...that's how. Just another mm or so of movement would've left him dead.

[TrailerParkJawa]

A friend of a friend was in an MRAP that hit a mine on Route Irish outside of Baghdad. No injuries, nothing. Started having serious emotional problems that were ascribed to PTSD, so they gave him a fistful of xanax to take on a daily basis and a desk job (still in country) and he was still having issues. Got rotated home, VA kept sending him for "talking therapy" and more and more and stronger and stronger antidepressants until finally he went to a civilian hospital and got the full MRI the VA insisted he didn't need and found out lo and behold his pineal gland had gotten detached. It was still there and still connected but it had been pushed around and damaged while nothing else in his skull had been. Left him prone to fits of rage, impotent...just a fucking mess.

So...that's how. Just another mm or so of movement would've left him dead.

I think it's sad that he didn't get the proper care or check up he needed from the VA.

[Targan]

I was a little bit too close to a few explosions back when I was a shotfirer (aka powder monkey). I know exactly what Grimace says about the "funny feeling" you get in your chest. I suspect he's talking about an explosion that occurred near him in actual combat, and I'll wager that he was somewhat closer to his explosions than I was to mine.

During my explosives training we let off a couple of fairly big ANFO explosions that were detonated virtually on the surface on flat, dirt ground. Mainly to show us what a bigger explosion looks and feels like. Upwards of 50 or 60 kilos, with a half a dozen sticks of Powergel to ensure a good initial detonation (I've seen much more ANFO go up but only with delayed detonations, the individual charges were smaller). We were crouched behind a low berm probably half a football field distant and you could clearly see the shock wave spread out from the epicentre. You feel the "crumph" right through your body. The first couple of times it creeps you out.

[Graebarde]

I think it's sad that he didn't get the proper care or check up he needed from the VA.

However the VA was the SECOND ones that failed, the military medical facilities should have checked him out too. Wonder how many other PTSD victims are of a similar nature

[WallShadow]

---snip---You feel the "crumph" right through your body. The first couple of times it creeps you out.

Like being in close proximity to a bunch of bagpipers, only much less damaging!
NOTE: I really do love the pipes, but I couldn't resist the free shot.

[Medic]

As one of the resident medics, I believe, I could clarify the effects of pressure waves on people.

Now, explosion is a sudden, rapid combustion. It causes heat and a shockwave, both of which have potential to kill.

Heat causes burns and combusts flammable materials. Clothing protects from the worst of it, but if it is not fire resistant, it might combust. Especially synthetic materials often have a nasty tendency to melt when subjected to great heat.

The shockwave is caused by the overpressure, caused by the air expanding due to the explosion. This has several results.

Depending on the force of the explosion, the shockwave sends things flying. The only problem is, it also leaves a vacuum in the ground zero, and should the explosion be powerful enough, the vacuum takes up to a couple of seconds to fill. This means, with bigger explosions, you need to duck not once but twice, as all the stuff that flew off with the shockwave has the nasty tendency of coming back shortly. Best idea is to sit in a foxhole and keep your head down.

Human body has about 60-70% of water and water is a relatively good conductor for a shockwave. While the bones form a rigid case around the lungs, but it isn't enough to stop the shockwave. While the overpressure from the shockwave simply compresses the gases inside the sinuses of the body, the rapid decompression after the shockwave causes the gases to expand so rapidly, the tissues can not compensate. Particularly vulnerable to damage from this kind of decompression is the bowel, filled with fecal matter and gas. It has been documented that people subjected to explosion shockwaves have had extensive damage to their bowels, up to several meters of bowel splitting open inside the abdominal cavity, which leads to a very nasty infection.

Overpressure in turn can cause damage to ears as the tympanic membrane , though flexible, can stand only up to so much. And it is not only the tympanic membranes in the ears that can be damaged. Hearing works through the tympanic membrane moving two very small and delicate bony structures - the hammer and the anvil, both very vulnerable to damage.

Overpressure also causes (usually small) tears in the lung tissue, due to the pressure differences outside and within the thoracic cavity. Lungs are not the only inthe thoracic cavity, that can be damaged. Heart in itself can be damaged by violent external pressure - for an example the F1 driver, Ayrton Senna, died of cardiac contusion after colliding the track wall in high speed.

In a nutshell, if you encounter someone who has been close to an explosion and that person is bleeding from his ears, it is safe to assume that he has a) perforated eardrums and b) perforated bowel until proved otherwise.

A great deal of injuries in explosions are so called secondary injuries that come not from the debris or the explosion itself but falling over or falling from somewhere. As a rule of fist, falling from higher than your own height is considered to be a high energy injuries.

[Michael Lewis]

Wow

Wow. I looked up body cavities. There's quite a lot of them.