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]

Originally Posted by Tegyrius

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]

Originally Posted by 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.

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.

[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]

Originally Posted by 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).

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

- C.

[Graebarde]

Originally Posted by 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

You know reading this again I KNOW what blast killed those boys. It was the RSM that caught them playing cards and not a shell. The shell story is the coverup to protect the innocent. <grin>

[dragoon500ly]

Came across this description of being under heavy artillery fire…

“The most clichéd but accurate metaphor for the sound of incoming shells in flight is that of an old-fashioned steam express train rushing past a few feet away. Depending on their distance, speed and angle, shells tunneling through the air make slightly different noises, so a heavy barrage weaves itself into a bewildering cacophony of sounds; but the rushing always ends the same way, with a thunderclap detonation. Hollywood’s microphones fail to convey either the sharpness or the loudness of battlefield explosions; and the visual effects normally used to simulate shellfire---with plastic bags of gasoline and aluminum silicate---are equally misleading. In reality the eye usually registers a shell burst as an instantaneous orange-yellow flash inside a dark, leaping fountain of mixed smoke and pulverized earth, sometimes studded and fringed with large pieces of slower-moving debris. The bigger, heavier chunks of earth and stones thrown up by the explosion fall near by first; the smaller debris, blown much higher, comes pattering and clinking down for a considerable time afterwards and over a wider area.”

“The instantaneous pressure wave from the explosion moves outwards at supersonic speed---this is the expanding ring effect seen fleetingly in, for example, aerial footage showing the explosions of sticks of bombs. It is followed after a slight, but appreciable interval by a blast wind---the bulk of hot gases, fragments and ground debris away from the explosion. People in the target area experience the pressure wave as a sharp squeezing sensation in the chest, and its shock is also felt through the ground underfoot; this shuddering of the earth is powerful enough to make those sheltering in trenches fear (justifiably!) that they are about to be buried alive, and those who are lying flat feel themselves being shrugged violently into the air. These sensations are accompanied by stupefying noise and under heavy and persistent fire all the physical senses are overwhelmed. Completely impotent to affect their chances of survival, soldiers find sustained shelling and mortaring the worst ordeal of battle; those experiencing it often become temporarily unhinged, losing all muscular control (including of the bladder and sphincter) and the capacity for any rational thought. These effects are particularly marked among those exposed to shellfire for the first time.”

“In the minority of cases when men suffer a virtually direct hit from artillery, the result is complete destruction of the body. The shell literally destroys the body, leaving, perhaps, a booted foot, a section of the human cranium, a bunch of fingers, a bit of clothing. When a body is blown up, the spinal column---surprisingly resilient---often survives; after a shell has fallen among a group of men, counting the remaining spines is often the only way to determine the number of dead.”

“Most injuries, however, occur further out from the site of the explosion. Blast injuries to the human body are categorized as primary, secondary and tertiary. The first is the direct effect of the pressure wave; the second the effects of fragments and debris carried by the blast wave; the third, the result of the body being thrown through the air and striking the ground or other obstacles.”

“The most obvious sign of primary injury is rupture of the eardrums, which may occur when air pressure rises to anything between 5 and 15 pounds per square inch; men who are killed by blast often appear peacefully asleep apart from the tell-tale bleeding from the ears. The lethal internal damage caused by pressures of 50psi and upwards do not present dramatic outward signs. It is the gas-containing organs which sustain immediate and often fatal damage from the pressure wave; the lungs and occasionally the colon suffer catastrophic injury from the instantaneous compression effect of the blast. Large, blood-filled cavities are formed in the spongy alveoli of the lung, and fatal air embolisms are released into the arterial system; less often, the bowels may rupture, as may the spleen and liver.”

“Secondary injures will be more obviously dramatic. When a shell bursts the steel case breaks up into fragments of all shapes and sizes, from tiny beads to twisted chunks weighing several pounds. These, together with stones, pieces of weapons and equipment, and even large bone fragments from casualties nearer the blast---whirl outwards from the center at different speeds. The effects of being stuck by shell fragments vary as widely as the size and speed of the shards. Sometimes a man is unaware that he has been pierced by a small splinter until somebody points out the bloodstained hole in his clothing. Larger fragments, cart wheeling unevenly through the air edged with jagged blades and hooks, can dismember and disembowel.”

“In many cases the evidence confronting an eyewitness is all too vivid. In others the immediate reaction is one of simple puzzlement: blast and steel can play such extreme games with the human form that the observer does not understand what he is looking at. When some random physical reference point suddenly jerks the whole image into a comprehensible pattern, the shock of recognition may be appalling. The results of massive destruction, the ruined hulk of a torso, the crimson rack of ribs, the glistening entrails, limbs ripped away and scattered, a severed head---have a charnel house squalor that denies all human dignity. On chilly evenings, the warm, gaping body cavities steam visibly, and the opened up bowels gave off the stick of feces.”

Source is “The Last Valley, Dien Bien Phu and the French Defeat in Vietnam”