Body Armour Effectiveness

[Dirtweasle]

Originally posted by LTC G:

... I just returned back from a year in Iraq and did my senior thesis on ballistic armor when I earned my engineering degree, so I know a thing or two...

...If anyone has any questions about Iraq or body armor, I'll be happy to answer them.

Glenn

First, thank you very much for your service Glenn.

How about a question on Iraq and Body Armor? In the press you read stories about guys having to buy body armor. The typical line in most stories is the stuff on the open market is better than what is bought by DOD. My guess is that sure there are always going to be small lot makers of really good gear and combined with the stereotypical image of DOD purchasing, ($500 hammers, etc...), it's probably more of the same. Given what it takes to produce body armor in large quantities is there an argument to be made that body armor for the troops was especaily off? The question in general; Is this gear with the troops as good as we should expect?

[hellfish]

Being a defense contractor now, it's very easy to see how hammers can cost $500.

[LTC G]

Mr. Battlefront.com,

To expound on your points:

Fatigue has less to do with weight than training. What do you want to bet that I can strap a 55 Lb. ruck on my back and yet still beat you in a 5K race? Why, because I train to a high physical standard (my 5k run time is 21:56-not bad for a 46-yr old). You generally will not find that amongst third-world armies or a guerilla force.

Boron Tetracarbide ceramic plates are issued to every soldier and most civilians in Iraq. The military calls them SAPI (Small Arms Protective Insert) plates and cover the chest and upper abdomen front and back. Currently being issued are side SAPI plates. The front and back plates each weigh about 10 pounds apeice and the side plates are supposed to be another 5 each. Yes, it's a lot, but no one turns down protection. Note that individuals do not have the choice of what to wear with the exception of a few SF guys. The key function of the side plates is to help protect against IEDs and VBIEDs (Vehicle-borne IEDs) which generally strike the side of a vehicle and can puncture the kevlar only side of body armor. VBIEDs are the most dangerous thing to us since you can load a 1000 lbs. of explosive into a truck or car as opposed to an IED constiting of an artillery shell. The kevlar by itself is good for fragmentation and ammo up to 9mm. The SAPI plates are rated to take 7.62 NATO ammo for four hits (in different areas aobviously) per plate.

As to your categories of fire, I would suggest the following threats to a soldier:

1. Debris from and explosion. Sand and gravel flying around will cut up and stun, but not generally disable a soldier. Does creat a lot of blood though.

2. Small fragmentation. Can be stopped by body armor and vehicles easily, but will disable exposed arms and legs.

3. Large Fragmentation. Not to sound defeatist, but there is essentially nothing that can protect you from large fragmentation except vehicle armor. It does not even have to penetrate your body armor to simply impart enough kenetic energy to remove your head or cause hydrostatic shock to your internal organs.

4. Small arms. This can range from the AK round (7.62x39 to 5.56x54(?) and is frankly all about the same. The NATO round has better penetration due to its higher velocity. Neither can penetrate U.S. Body Armor and both can penetrate an unarmored body, so I don't see any difference, except possibly for acting against a steel helmet.

5. Blast. This includes RPGs as well as our latest nemisis in Iraq - the EFP (Explosively Formed Penetrators) which is a platter charge able to penetrate anything less than an Abrams. This forms a molten slug out of the platter and will take out the drive and front passenger of a HMMWV while leaving everyone else essentially unharmed. Obviously, body armor menas nothing in this context.

Hope this helps - always glad to share my experiences.

Glenn

[LTC G]

Dirtweasle,

The news reports about troops buying body armor are either old or bull. All troops receive body armor including the latest SAPI plates. There was a problem in the first year of the war, but that has long been solved ever since that famous question in Kuwait.

There is a problem with different manufacturers claiming that their armor is better and they should be allowed to sell it to troops. The Army has gone to the extent of banning any non-regulation armor. The logic is that we don't want to create an "arms race" amongst troops who will go out and spend $1000 on something that some magazine says is the latest greatest stuff, but isn't necessarily and then everyone else wants that too.

I'll admit, it didn't do a lot for morale when the Marines issued a recall notice on their body armor last year, but told all the troops that their armor was fine. My understanding is that the Marines are now going to a slightly different armor (Dragon Skin), but there really isn't any significant difference.

Just as an aside, the hardest thing to do with your armor on is reach for something. Can't really put the butt of your weapon against the shoulder either, so the upper bicep just takes the bruises.

[Battlefront.com]

Glenn,

Mr. Battlefront.com,

Hehe... I kinda like the sound of that, but Steve will do just fine

Fatigue has less to do with weight than training. What do you want to bet that I can strap a 55 Lb. ruck on my back and yet still beat you in a 5K race? Why, because I train to a high physical standard (my 5k run time is 21:56-not bad for a 46-yr old). You generally will not find that amongst third-world armies or a guerilla force.

Yup, that's exactly what I meant. In game terms the OPFOR usually will have lower Experience and Fitness ratings than US soldiers. However, that is not a sure bet. Recent report out of from the head of the NG states that fully 2/3rds of the units are not prepared for combat, either due to equipment, training, manpower, or physical condition. This reminds me of what happened during Desert Shield, where NG units were put through several months of intensive "catch up" training while Iraq was bombed day and night.

My point being that physical abilities differ not because one Human body is inherently better due to its place of residence, but due to how much it has been sculpted into a fighting force. Expect lots of highly trained and fit US forces in CM:SF's stock scenarios, expect the opposite from the OPFOR. At least most of the time

Boron Tetracarbide ceramic plates are issued to every soldier and most civilians in Iraq.

OK, that's what I thought. One of the maddening things about researching CM:SF is so much of what we learned yesterday was changed today and expected to change tomorrow. There are so many things changing it makes my head spin I liked the good old days when a contractor would say "we got a contract for x number of OD widgets, and they will be in service by the end of the year" and you could either move the date up by 4 years or simply disregard it as never ever going to be used. Now... man, we have to actually take the press releases at near face value!

Thanks for your suggestions about how to treat armor vs. threats. Notes taken!

Oh, and welcome back I don't know if you ever had contact with COL Rich Seim (retired SF Aug 2001, last posted to Bosnia), but he was a great early supporter of our work. Unfortunately(?), his first civilian job was with FEMA's response team to WMD a month before 9/11. Haven't hardly heard from him since, no small wonder.

Steve

[ August 08, 2006, 02:12 PM: Message edited by: Battlefront.com ]

[flamingknives]

Mr. flamingpicky would like to point out that EFP slugs are not molten. Technically the constituent material remains in its solid state, but the explosive pressures exceed its bulk yield stress.

The same applies to shaped-charge jets.

Not that this detracts from your post in any way, but

a) I am a notoriously pedantic.

The common misconception of a 'red-hot jet/slug' really bugs me.

[Battlefront.com]

LTC G, be forewarned... we have a lot of Mr. Pickies here on this Forum Fortunately, some of them actually know what they are talking about. Just avoid discussions about Bren Tripods and the difference betwen an MG42 in the heavy and light roles and you'll likely keep your sanity

Steve

[ August 08, 2006, 02:29 PM: Message edited by: Battlefront.com ]

[dan/california]

Flamingpicky, you are right about the misconception. It just so happens that if you are dealing with it from any perspective other than a CAD screen trying to improve armor or warheads the distinction is just irrelevant.

[ August 08, 2006, 02:52 PM: Message edited by: dan/california ]

[LTC G]

Mr. Flamingpicky,

Being a degreed engineer, I try to avoid using highly technical terms when describing things because most people just get lost.

An EFP is a platter charge, not a shaped charge as most people misconstrue. The platter's used by the Iraqi insurgents are typically 4-6" in diameter and "soften" to a slug about 3/4 thier original diameter. Molten was not to imply liquid, which is a state the metal does not reach, otherwise it would splatter against the vehicle armor.

A shaped charge forms a plasma jet of superheated gas which melts metallic armor. While this works well against a tank or IFV, it has little effect against the thin armor of a HMMWV.

I'd much rather be hit by a shaped charge rather than an EFP when driving around Iraq. Good discussion.

Glenn

[juan_gigante]

LTC G (or anyone else), if I could ask for you to expand on one of your earlier points?

Originally posted by LTC G:

4. Small arms. This can range from the AK round (7.62x39 to 5.56x54(?) and is frankly all about the same. The NATO round has better penetration due to its higher velocity. Neither can penetrate U.S. Body Armor and both can penetrate an unarmored body, so I don't see any difference, except possibly for acting against a steel helmet.

What types of rounds are you assuming here? I don't know as much about different types of rifle rounds as some, but I know that different types of rounds, even within the same calibur, have different penetration figures. Are there special 7.62 X 39mm rounds that can penetrate US body armor that Syrian SF might have? What about 5.45 and the AK-74?

At what sorts of ranges can the armor stop what rounds? As I understood it, US armor wouldn't necessarily stop a point-blank 7.62 round.

Thanks for any clarification you can provide!

[LTC G]

Juan,

As someone else pointed out, even the SVD sniper rifle failed to penetrate a soldier's body armor at fairly close range.

Remember, the SAPI plates only protect the chest and upper abdomen, there are still plenty of places our soldiers get shot and killed, although it is usually a bleed-out, not instant kill. The neck and groin and especially vulnerable areas which we do protect with soft Kevlar, but that will not be effective against rifle fire.

We suffered some KIA in Iraq through the round entering the chest through the armpit or down through the neck, but those were freak shots that you can't really do much against.

Glenn

[Dirtweasle]

Thanks for the reply, that's what I thought, just wanted to know if I had it right. The topic comes up every now and then.

Originally posted by LTC G:

...the round entering the chest through the armpit or down through the neck, but those were freak shots that you can't really do much against.

Glenn

ISTR that to mitigate against rounds hitting through the armpit hole that is why soldiers and marines orient their torso at 90' angle to the likely vector of incomming fire. Unlike how we learned to shoot hunting where your body is more or less parallel to the target.

[flamingknives]

Originally posted by LTC G:

Mr. Flamingpicky,

Being a degreed engineer, I try to avoid using highly technical terms when describing things because most people just get lost.

An EFP is a platter charge, not a shaped charge as most people misconstrue. The platter's used by the Iraqi insurgents are typically 4-6" in diameter and "soften" to a slug about 3/4 thier original diameter. Molten was not to imply liquid, which is a state the metal does not reach, otherwise it would splatter against the vehicle armor.

A shaped charge forms a plasma jet of superheated gas which melts metallic armor. While this works well against a tank or IFV, it has little effect against the thin armor of a HMMWV.

I'd much rather be hit by a shaped charge rather than an EFP when driving around Iraq. Good discussion.

Glenn

Actually, a shaped charge doesn't produce a gas jet and certainly doesn't 'melt' through armour. Like the EFP it's technically solid. It just happens to be moving at more that 6 km/s. It will drill a narrow hole through a large amount of armour, but is less effective against light armour, like a Humvee. Still, I wouldn't want to be anywhere near one when it goes off, much less in line with it.

If EFPs were liquid, however, it would still be liquid with a density of more than 8 g/cm^3 and travelling at 2km/s. Impacts at that speed do not follow conventional rules, so it would still do about as much damage.

I think dan/california has it right, though

[LTC G]

Flamingknives,

Shaped charges are indeed a plasma jet. By definition, plasma (in physics) is gas that is so hot it is stripped of its electrons.

I have fired many a shaped charge into the ground(for cratering charges) there is cerainly nothing solid at the end of the hole and it is quite hot.

If it remained solid, you are implying that it penetrates kinetically, which wouldn't make sense since a shaped charge works better the slower it is going. Take a look at some knocked out WW2 tanks and you'll see where it does melt through the armor and splatters the interior of the vehicle.

As to the other comment. It would matter greatly whether an object was liquid or not upon impact. A liquid is incompressable and would expand out along the path of least resistance. Energy is still transferred, but deformation would be minimal. That's why we use fire hoses instead of sandbalasters for crowd control!

[Imperial Grunt]

Sandblasters for crowd control...why did'nt I think of that?!

[YankeeDog]

I'm probably way out of my element here, but everything I have read on Shaped Charge Physics argues that the penetrator is a hyperfluidic solid, and *not* a plasma, and that extremely high temperatures are not involved. The mechanism is, rather, hyperbaric plastic deformation.

And, furthermore, everything I've read seems to agree that the penetration is achieved through plastic deformation of the armor, not via "melting" as such, though the net result is indeed similar.

This article seems to agree with other stuff I've read in regards to the above:

Global Secuity Shaped Charge Page

Quoting from the above:

"On reaching a target, the pressure developed between the jet tip and the forming crater can be as high as 10 Mbar (10 million atmospheres), several times the highest pressure predicted in the Earth's core."

And later:

"It is universally agreed that conical liner collapse and target penetration both occur by hydrodynamic flow. However, it has been established by X-ray diffraction that the jet is solid metal and not molten. Additionally, best estimates of jet temperature by incandescence colour suggest a mean value of about 450°C, and copper melts at 1083°C at atmospheric pressure."

So there we have it, I guess. No plasma. No searing hot temps. Helluva lotta pressure, tho.

Cheers,

YD

[flamingknives]

Thanks YankeeDog. An accurate description and extra-fancy words to boot.

I'd add that you can take X-rays of a shaped charge jet, which you wouln't be able to do with a gas

[LTC G]

Yankee Dog,

I would question the authority of one source, especially since the next line says:

"One recent theory that would help explain this is that the jet has a molten core but with a solid outer sheath."

So apparently it is molten? Your article is merely a cut and paste of other articles so it is hard to get anything definitive out of it.

Most sources state that the mechanisms of a shaped charge jet are not fully understood. However, every article has agreed with the following:

"Explosive energy is released directly away from (normal to) the surface of an explosive, so shaping the explosive will concentrate the explosive energy in the void. If the void is properly shaped (usually conically), a high-velocity jet of plasma will form."

Caveat - I am not claiming to be an expert (but I did stay at a Holiday Inn Express last night) on shaped charges, I think you need a PhD. to fully understand some of these articles. I personally have trouble accepting the solid theory since it would not seem to account for spaced armor defeating shaped charges. I would think only a liquid or gas would expand into the annular space. If it were a true solid, like a long rod penetrator, APFSDS, then spaced armor would not work. The theory above about a molten core with solid-behaving outside works for me - maybe we're both right.

Glenn

[YankeeDog]

I simply used the Global Security page as a general reference. But I have read a few scientific article on the subject, written by bona fide lab-coat types, and none of them asserted that the penetration jet was a plasma. But if you know of one, please do post and I will gladly read it.

Don't claim to be an expert in hyperbaric fluids, either, but my understanding Plasmas have distinctive radition signatures, and as such are very easy to detect. If the penetration jet were a plasma, I would think this would have been incontrovertably proven by now.

But there is clearly disagreement as to exactly what is going on with the jet, among those who study this sort of thing. It's a very cutting edge area of Physics.

I would note however, that by my layman's undertanding, the temperature and x-ray diffraction evidence is difficult to refute, and pretty conclusively proves that the jet is not a plama. As you state, though whether the jet is completely solid, or some mixture of solid and molten, is apparently open to debate.

I do find it hard to see how you'd get liquid copper at 450 degrees F, underhyperbaric conditions, though. Liquifaction temperature goes up with pressure, not down (remember the NPT matter state curve?).

Be careful, too, of confusing "liquid" with "fluid." All liquids are fluids, as are gases and plasmas. But rigid solids can, under the right conditions, become fluids. One such condition under which some normally rigid solids become fluids, is extremely high pressure. One type substance that does this particularly well is metals. Interestingly, this may explain why ceramic composite armors resist Shaped Charge warheads more effectively -- Ceramics are among the most un-fluid solids known, even at high pressures. The can be brittle, and crack or shatter, but they rarely flow.

Finally, as far as spaced armor, a hyperbaric, fluid solid is nothing at all like a rigid solid penetrator such as APFSDS. Apples and Oranges. Whether the jet penetrator is solid, liquid, or plasma, it is well known that it only remains focused for a few feet. Beyond that, the extremely high pressures that created it fall off, and it loses the focused shape that allows it to transfer its energy into the armor so efficiently. The behavior matches the hyperbaric fluid solid, molten liquid, and plasma model. You wouldn't expect any of them to say focused and coherent, once pressure drops down out of the exotic physics realm, and back into the normal world. . .

Cheers,

YD

[flamingknives]

A basic hollow charge might create a gas jet, but modern shaped charges have a liner. There's plenty of studies into stress-strain characteristics of jets, which implies that it cannot be gas, since stress and strain do not exist in a fluid.

The jet travels at between four and ten kilometres per seconds, which is between twelve and thirty thousand fps (roughly) and there is a velocity gradient between tip and tail. It's pretty unstable, so if you can disrupt it slightly (like with spaced armour or distance, so as to exploit manufacturing imperfections) then it will spray all over the place and not hit any given location with enough mass to cause significant damage. Plus you've got to consider aerothermal effects.

[Battlefront.com]

Plus you've got to consider aerothermal effects.

Oh, but of course! (he says trying to sound intelligent, realizes nobody is buying it, goes back into tree and hides until someone starts talking about how many buttons there are on the new Army ACU or some other such uniform related tidbit)

Steve

[Michael Dorosh]

Originally posted by Battlefront.com:

</font><blockquote>quote:</font><hr />Plus you've got to consider aerothermal effects.

Oh, but of course! (he says trying to sound intelligent, realizes nobody is buying it, goes back into tree and hides until someone starts talking about how many buttons there are on the new Army ACU or some other such uniform related tidbit)

Steve </font>

[flamingknives]

Mwa-ha-ha!

You should see what I'm like when I'm trying to confuse people!

It basically means heating caused by aerodynamic drag. At 8kmps you'll be generating alot of heat through friction with the air.

But yes, aerothermal does rate highly on the 'cool engineering term' scale.

[dan/california]

The best example I have seen to explain the way a shaped charge works is the linear charges they use to cut the big beams in building for controlled explosive demolition. It is just a strip of copper bent bent into a V shape. They attach it to the beams and add when detonated the the copper ling cuts the beam cleaner than most welders could. Check picture below

http://en.wikipedia.org/wiki/Image:LinearShapedCharge.png

Wikipedia has a very through article. When the Pentagon starts talking about building high performance ones it gets stupid complicated, supercomputer simulations, DU and other fancy liner materials, the whole nine yards.

[dan/california]

One additional fact, the shell /missile can't be going above some limiting velocity, otherwise the charges geometry is destroyed by impact before it can detonate properly/completely.