Muzzle Blast

[Eridani]

Ok, I just had a weird occurence here-

I was busy cleaning out the Americans in Last Defence, my Tiger, out of HE, was sitting right up next (like 5-10 meters from) an Amirican Rifle Squad. I fired an AP round from this range and NOT A SINGLE AMERICAN WAS KILLED! I'm sorry, but the simple muzzle blast from the gun would have taken at least a few of them out. What's up with this?

Also, I found out the fun in telling a troop in the top story of one building to walk to the top story of another building... my quesion is, whats the exposure for a unit that's floating ten feet in the air in the complete open? (Other than the fact that all the enemies would sit their dumbstruck and be unable to shoot at him)

[Ben Galanti]

The floating unit thing was a bug that has been fixed in the final game. Dunno if muzzle blast is modeled or not (but it sounds like not from your little story...)

[Bullethead]

I'm curious about the effects of muzzle blast. I mean, I've seen somebody cite in another thread that the M1's 120mm gun's blast will kill people a long way out in front. But I have to wonder: does that mean "will always kill" or "might kill under freak conditions" or something in between?

Seriously, I've been shelled a few times, some of them pretty close and pretty big. The concussion bounced me around, knocked the wind out of me, and made my ears bleed, but I'm still here (although a bit deaf ).

OK, shell bursts aren't focused cones of blast like from a guntube, but what about naval guns? Kamikaze action reports are full of mention of light AA gunners being blasted by 5" guns cranked around to the limits of their traverse. You'd think this would be pretty close to being blasted by a Tiger, but it doesn't seem to have killed anybody, or even made them quit their posts, at least in the reports I've read.

Anyway, I'd like some more info on this phenomenon. Thanks in advance.

-Bullethead

[StuNZ]

As I understand it, the danger with the M1 isn't the muzzle blast that is dangerous to infantry in front, but the casing of the sabot round that falls away when fired.

Course I'm no expert though, and more likely wrong than not (disclaimer )

[Paul]

This comes from a "Battle for Mortain" book by Alwyn Featherston:

Sergeant Burick released the safety and raised the bazooka to fire again. The tank (fiftyfive-ton Tiger) was almost on top of him when he pulled the trigger a second time. At almost the same moment, the Tiger's 88mm cannon belched a tongue of flame.

The blast knocked Burick down, but the sergeant reloaded his bazooka, rose, and fired again just as the tank's main gun let loose another round.

Again Burick was knocked to the ground, this time badly wounded. He crawled to his foxhole and found another round for his bazooka. Burick loaded his weapon a third time. Unable to stand, he dragged himself to a firing position and loosed a third shot at the Tiger.

That was enough for the German tank commander. He put his monster into reverse and backed up the road.

"Burick, with utter disregard for his safety, tried to push another injured soldier into his foxhole," reported Lt. William Anderson. "Burick turned and called for more bazooka ammunition, then fell unconscious by the side of the road. Later, he died of his wound."

That is the kind of bazooka man I need on my team in CM.

Paul

[Guest JonS]

But Paul, that IS the kind of Bazooka team you have - he missed three times and died ...

Jon

(No disrespect to Sergeant Burick or his family intended!)

------------------

Quo Fas et Vino du Femme

[Bullethead]

<BLOCKQUOTE>quote:</font><HR>Again Burick was knocked to the ground, this time badly wounded.<HR></BLOCKQUOTE>

But what was he wounded by? The Tiger was shooting at him so it could well have gotten him with shrapnel or the bow MG. Or perhaps some other German had seen him pop up before was was sighting in on the rim of his hole waiting for him to try again.

I dunno, maybe I'm splitting hairs, but a small (see below) concussive effect doesn't give you a visible "wound" as in something poking a hole in you or otherwise making observable blood flow. So if he was "badly wounded," I figure something metal hit him. And blast is an area effect thing. If he was in the blast cone before and just got knocked down, why would it give him a fatal "wound" next time?

I guess part of my problem here is that while an 88 is a big gun for a WW2 tank, it's a small gun by any other standard. I've been within 20 yards of the muzzles guns a lot bigger (155mm and 203mm howitzers and naval 5"/54s), and closer than that to 122mm shell bursts, with no ill effects (eh, speak up, sonny ). Granted the guns weren't pointed RIGHT at me and a shellburst ain't a gun blast, but you can see why I'm skeptical of muzzle blast casualties from mere 88s.

-Bullethead

[Paul]

Bullethead

I agree with you that blast probably did not wound him. In the article it mentions that the blast from the gun knocked him down and he was able to get up and try again. That is what I tried to support in response to Eridani's surprise that, quote; "simple muzzle blast from the gun would have taken at least a few of them out."

JonS

I guess you have a point there. He He. But, he did at least chase that Tiger away and shown an unbelievable amount of bravery. And he did not miss three times. He had a safety stuck, which I did not mention before.

[Guest TOBRUK]

Speaking of muzzles:

Has anyone noticed that in both Reisberg and Chance Encounter the muzzles of the Shermans have NO HOLES in them. Maybe this is why the enemy dies laughing....

Hope this is rectified in final version.

[Eridani]

I'm not saying that the muzzle blast would effect anyone 20 meters away... but when your 5 meters from the muzzle being fired AT. I know that in civil war re-enactments (I have friend who does that), when they fire the cannon blanks, they need to have people clear of a 45 degree cone out to about a range or 15 meters, inside that cone, (they say, I have not experienced this myself), the force is easily enough to knock you out, and I'm sure (after watching these things shoot) that it would EASILY kill a man at less than 10 meters.

Think about it, that concussion is strong enough to send a five-pound shell at 700 fps... that's a lotta force, enough to ruin some poor sucker's day.

[Bullethead]

<BLOCKQUOTE>quote:</font><HR>I'm not saying that the muzzle blast would effect anyone 20 meters away... but when your 5 meters from the muzzle being fired AT.<HR></BLOCKQUOTE>

Yeah, but the increased size of the blast from the bigger guns makes up for the difference in range to some extent, I'd think .

<BLOCKQUOTE>quote:</font><HR>I know that in civil war re-enactments ... when they fire the cannon blanks, they need to have people clear of a 45 degree cone out to about a range or 15 meters, inside that cone, ... the force is easily enough to knock you out, and I'm sure (after watching these things shoot) that it would EASILY kill a man at less than 10 meters.<HR></BLOCKQUOTE>

Well, blanks ain't safe things--they fire out chunks of whatever contained the powder. These leave the muzzle with enough speed to penetrate your body and kill you, although they are very light so slow down within a few meters. There's also the danger of flash burns near the muzzle. This, I'm pretty sure, is the main reason for the safety zone you describe.

What mechanism would the concussion use to kill you? As I understand it, to kill somebody by external force you need to seriously reshape parts of the body. Either crush him, or puncture him, or break his neck. Vital organs are pretty well protected by bone, you now. So sure, you can have a wave of air hit somebody in the head hard enough to knock him out, just like you can with your fist. But it's a long way from that to crushing his skull or ribcage.

There have been a lot of people killed by concussion from very near misses of very big shells and bombs. As I understand it, the pressure crushes their abdominal cavity and they die slowly and painfully from internal bleeding without any serious external damage. But this sort of thing requires serious firepower: 8" and bigger shells landing very close, or being next door to an Arclight impact area.

<BLOCKQUOTE>quote:</font><HR>Think about it, that concussion is strong enough to send a five-pound shell at 700 fps... that's a lotta force, enough to ruin some poor sucker's day.<HR></BLOCKQUOTE>

But it can only throw a round when focused into 1 direction by the guntube. The expanding gas follows the path of least resistance, so if you set off the same amount of powder in the open air with the round sitting on top, you wouldn't get nearly the velocity and range out of the round. Likewise, once the gas passes out the muzzle, it's free to expand in all directions (even backwards if the gun has a muzzlebrake). So it rapidly loses its concentrated force and, because gas is very light, it also slows down very quickly.

-Bullethead

[Doug Beman]

Bullethead said "As I understand it, the pressure crushes their abdominal cavity and they die slowly and painfully from internal bleeding without any serious external damage"

OOOhhh....EEeuuggghh...{puts down meatloaf} I'm not hungry anymore

DjB

[This message has been edited by Doug Beman (edited 12-15-99).]

[rugger]

It's very unlikely that you could be killed from muzzle blast. When I was in the Marine Corps, a friend of mine who was in artillery, told me a about a guy that walked out in front of the guns to take a leak. While he was doing his business, a quick fire mission was called in. The concussion from the guns bursted both his eardrums and knocked him unconscious. And that was from a 105 howitzer, actually about four or five, so I doubt the blast froma WW2 era tank would kill you. Although you would definitely feel it.

Whit

[Sten]

Doug,

as a MD with some experience from patients with concussion wounds I can tell you that what Bullethead said is not even half of it. What happens to the eardrums also happens to other organs in contact with air.

Lungs. Not pretty. Very fatal.

Sinuses. Serious pain from fractured facial bones. Sometimes fatal, suffocation from the swelling of the back part of the pharynx.

In case of the blast coming from the side, corneal ruptures, sometimes shedding of the retina.

The amount of force required to inflict these wounds can of course vary greatly, but an 88 surely exceeds the required force by a wide margin.

Sten

[Brian Rock]

Proximity is a big issue here. I'd expect the concussion to cause a bit of damage at 10 cm, whereas 30 meters wouldn't worry me a great deal.

You need to bear in mind that with infantry units, the graphic essentially indicates centre of mass. The actuall troops in the unit are dispersed around the immediate area.

So when Eridani says "right up next (like 5-10 meters from)", this could be anywhere from virtually adjacent to the gun to maybe 20+ meters away. As a general rule I'd expect the latter figures, as most GIs would have enough sense not to stick their heads next to an 88.

Finally, from a coding point of view, I expect that troops killed or seriously injured by concussion would be a very rare occurrence, and not worth modelling.

[Bullethead]

<BLOCKQUOTE>quote:</font><HR>as a MD with some experience from patients with concussion wounds I can tell you that what Bullethead said is not even half of it.<HR></BLOCKQUOTE>

Doc, I know that sufficient concussive force can not only squash organs but can rip off limbs. But my question is all about what is "sufficient." Hopefully, you can help clear this up. Can you tell us what type of explosions caused the injuries you've seen, and how close the victims were to them? I've been pretty close to bigger bangs than Tigers could do and was no worse off than Tom Hanks in "Private Ryan" (perfect depiction of the effect in that movie, IMHO)

-Bullethead

[Sten]

Bullethead,

I've seen 6 patients with concussion injuries:

- Two were from exercise hand grenades (= ~normal amount of explosives but no fragmentation), in one of these cases the patient had more or less thrown himself on the grenade, resulting in severe ruptures of both lungs as well as internal bleeding. Despite our efforts, it was fatal. The other case caused 'only' the rupture of the eardrum/s of three people. They were about 6 meters from the grenade, but in a building.

- One case was a high pressure bottle of gas (nitrogen, N2, not petrol) that fell and the tap came loose. The bottle careened about in the room and the blast from the bottle struck the patient in the face. She got some pretty severe damage to one eye, I don't know how severe.

- Another gas bottle blew up in a fire. The patient was blown off the landing he was standing on. He was hurt more from the fall than the blast.

- An explosive charge used for construction work exploded prematurely. The patient was ~4 meters from the charge and lost the lower part of his arm. It was a bit unclear whether the damage was caused by a foreign object or the blast itself. I was told the amount of explosives was about equal to 0.4 kg of TNT, but I really have no idea.

- A demonstration for military firemen went wrong and a plastic oil drum purpousley filled with a perfect gasoline/air mixture blew up with the patient standing about two meters from it. Dislocation of the left shoulder, fracture of the right femur (=thigh bone), some intracranial bleeding and some fractured facial bones. He recovered.

As you can see from these cases it is almost impossible to judge what 'sufficient' force is. Also, some of these cases were inside and in only three of the cases can even a rough estimate as to what the explosive forces really were be done (grenade cases and construction site case). You probably could calculate it in the oil drum case as well, but I don't know how to do that. Someone else?

As you said, proximity is a major factor (the two grenade cases) with the force diminishing exponentially from the center of the blast. The amount of 'channeling' of the force will also play a part in this. The patient blown off the landing is a good example of this. The force from the exploding bottle would probably not have been sufficient to blow him off the landing, had the bottle not been standing in a small storage room with the door facing the landing.

I think the term 'sufficient' is probably ill chosen. There is no 'sufficient' force, only cicumstances combined with the force in every case. A prone person 10 meters away from a given artillery detonation might be killed outright. Make the earth just a little more porous and that person could walk away with a ruptured eardrum.

I'm still often surprised with how much abuse the human body can take and just shrug it off, and I'm equally often surprised with how even small amounts of abuse sometimes prove fatal.

How close to a muzzle blast is always fatal? I have no idea. How far away is always safe? I have no idea.

I don't think there is an answer.

Sten

[This message has been edited by Sten (edited 12-23-99).]

[Thomm]

In discussions about shockwaves the term 'force' should be substituted with 'pressure'. A shock wave is basically an sudden change of pressure and velocity and the damage is done by the difference of pressure in front and behind the shock wave. But forces in the strict sense are not imposed.

By the way: tell me when I am becoming a pain in the you-know-what with my definitions !

Thomm

[Sten]

Thomm,

not a pain, but rather a severe itch.

But, force IS excerted. The FORCE comes in part from the PRESSURE gradient, as you rightly stated, but FORCE in the very strictest of definitions can stem from differences in pressure as well as, say, a bullet or a push from another person. The expanding gasses in an explosion most certainly applies FORCE to its surroundings.

When discussing injuries from blasts, they are often partly from the sudden change in pressure, and partly from the force excerted on the body. Differentiating the two has more academical than clinical implacations, as patients suffering from one invaribly suffers from the other.

Sten

[Thomm]

... when itching turns into pain ...

Pressure = Force / Area.

If you multiply the normalized surface normal vector with the local pressure and the area of a small surface element, then you get a force vector.

If you integrate all those (pressure) force vectors over the surface of e.g. an arm, you will get the resultant force vector ... which will rip off the arm in the worst case. This is what you mean and you are right.

Now my point is: if there is no arm then there is no surface then there is no force, but there is still a pressure. Force is no variable to describe a state. Pressure is a state variable and the pressure jump in the shockwave is the proper measure for the effect of the blast in my humble opinion. The same is true for heat, for example. You cannot describe a state with 'heat'. Heat is a process property, such as force. The respective variable to describe the state is: temperature.

Ahhh, I could go on for hours, but unfortunately I have to buy Christmas presents.

<hr>

MERRY CHRISTMAS AND A HAPPY NEW YEAR !!!

Thomm

[Bullethead]

Sten said:

<BLOCKQUOTE>quote:</font><HR>How close to a muzzle blast is always fatal? I have no idea. How far away is always safe? I have no idea. I don't think there is an answer.<HR></BLOCKQUOTE>

Thanks Doc . That helped a lot. Looks like if you're right on top of the blast, it's impact can damage you. If you're a bit further away, the blast itself might not do much really dangerous, but it might toss you so you get hurt in landing, or throw some object into you. Very hard to draw lines, though..

Guess I've been lucky. The times I've been tossed, I've landed OK .

-Bullethead

[Bullethead]

<BLOCKQUOTE>quote:</font><HR>Now my point is: if there is no arm then there is no surface then there is no force, but there is still a pressure<HR></BLOCKQUOTE>

As the shockwave is traveling between surfaces, isn't it exerting a force on all the air molecules in it's path?

-Bullethead

[Guest aaronb]

The discussion has two elements:

1) how much pressure comes out of the barrel of an 88 (or other cannon) at what distance and orientation to the barrel, and

2) how much pressure will kill someone?

The answer to 1) can be estimated by doing a little study on interior ballistics: someone with Charles' knowledge could do this.

Gas pressure at the muzzle of WWI guns might even be in a reference book, as it would relate to barrel wear (although breach pressure is more relevant to barrel erosion). Gas pressure at a distance can be estimated by the cube-root rule modified for muzzle brakes and the initial vector of the propellant mass.

for 2), overpressure effects are well known and studied because of their relevance to nuclear blasts.

Damage Overpressure (in psi)

Light housing destroyed 5

Brick housing/commercial buildings destroyed

10

Reinforced concrete structures destroyed

20

Severe lung damage/eardrum rupture in humans

20-30

Death of humans 40-100

Shallow buried structures destroyed 45-280

Do a web search on 'overpressure death' and find the numbers for yourself.

So, if Charles and Steve decide to model overpressure casualties, they can develop a realistic way to handle it.

[Bullethead]

aaronb said:

<BLOCKQUOTE>quote:</font><HR>Damage Overpressure (in psi)

Brick housing/commercial buildings destroyed

10

Reinforced concrete structures destroyed 20

Severe lung damage/eardrum rupture in humans

20-30

Death of humans 40-100<HR></BLOCKQUOTE>

Ah, thanks. This is just the sort of data I was hoping somebody could turn up.

It looks like it takes more overpressure to turn a man into a casualty (incapacitated/killed as opposed to stunned) than it does to blow down the 3rd little pig's brick house.

So, looks like whatever pressure an 88 generates, it isn't enough to make a casualty in CM terms. It can break windows and temporarily stun (suppress) guys, but I've never heard of one blowing down a house just with muzzle blast alone. Ergo, CM shouldn't have muzzle blast casualties.

Thanks again.

-Bullethead