[ WarPragmatics ] Message 884 (68 left): Mon Jan 28, 2002  12:00am
From: TTK here..
Subject: request for speculation

  Could a very large (80kg) HESH warhead kill an M1A2 on its front 
arc despite chobham/DU armor, or would the spacing + spall liner + 
heavy armor defeat any HESH regardless of size (within reason)?

  Is HESH entirely dependent on using contiguous armor to transmit 
its shock wave, or can the shock wave hop gaps between layers of 
armor?

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[ WarPragmatics ] Message 885 (67 left): Mon Jan 28, 2002  12:00am
From: George
Subject: Re: request for speculation

It would take something like two tons of HE in a bomb or HESH
warhead to spall anything through the frontal Burlington armor
of a M-1A2 tank.

Though it's not specifically designed to, its design features
nearly completely negate any effect a HESH type warhead has,
until it gets so significant as to implode the whole armor box
and cause the turret structure to fail on a gross manner.
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[ WarPragmatics ] Message 886 (66 left): Mon Jan 28, 2002  12:00am
From: jhdiii
Subject: Re(885): Re: request for speculation

Two *tons*?  References?

I'm as impressed with modern tank armor as the next person, but two tons is a
vast amount of explosive to wield against a tank.
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[ WarPragmatics ] Message 887 (65 left): Mon Jan 28, 2002  12:00am
From: George
Subject: Actually

Less than 2 tons will probably wrap the shockwave around and
implode the front or turret deck, on reflection.  but it would
take about that much to breach the main armor package by direct
effects.

I can't really discuss how Burlington works in this open of
a forum...
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[ WarPragmatics ] Message 890 (62 left): Tue Jan 29, 2002  12:00am
From: TTK here..
Subject: 2 tons, okay

  I can actually believe that, if a fraction of what I've seen 
speculated on chobham is true.  Thanks for putting that thought to 
rest.

  HESH doesn't actually breach armor; it instead transmits energy 
through it and destroys softer targets inside (like crew).  I was 
wondering if chobham was amenable to that, but more investigation 
yielded that the M1A2's chobham is spaced, and laminated, AND had 
a spall lining, all of which are considered useful defenses against 
HESH attacks.  Still, I wanted to ask, in case the real situation 
was less straightforward than it first appeared.

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[ WarPragmatics ] Message 891 (61 left): Tue Jan 29, 2002  12:00am
From: little punk
Subject: Re(890): 2 tons, okay

What I'm more curious about is whether or not the protecton which TTK mentioned
has been there since the advent of the M1A2.

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[ WarPragmatics ] Message 892 (60 left): Tue Jan 29, 2002  12:00am
From: TTK here..
Subject: ^^^

  As far as I know, the upgrade from M1A1 to M1A2 came with the 
full-on chobham laminated/spaced armor with a thick layer of DU 
goodness, upping the damned walking mountain to a mass of just 
under 70 tons.  It is the most heavily armored tank in the world 
in addition to having the most technologically advanced armor.

  Not sure if that's what you were asking .. ?

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[ WarPragmatics ] Message 894 (58 left): Tue Jan 29, 2002  12:00am
From: bama
Subject: ^^^

seems like you could just stick a potato in the air intake
and wait for the occupants to suffocate.

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[ WarPragmatics ] Message 896 (56 left): Tue Jan 29, 2002  12:00am
From: TTK here..
Subject: HEAT vs HESH

  [Responding to a post, not included here, about HEAT.]

  HEAT is an entirely different matter .. a HEAT warhead consists 
of a *very* precisely-machined hollow cone of high explosive, 
wide-part-forward, with a *very* precisely-machined inner lining 
of copper.  The angle of the cone is a function of the distance 
of the impact-sensor in the nose of the warhead, such that when 
the warhead hits, the explosive cone's energy is transferred into 
making the copper lining a very tightly aligned pencil-like jet, 
focussed precisely on the armor being penetrated.  It is specific 
to anti-tank munitions (eg, "High Explosive Anti-Tank").

  Spaced armor (one layer up front, to set off the warhead, and 
one layer a ways back, to give the jet time to defocus, without 
having to carry the extra mass of armor in the in-between space) 
is somewhat effective against HEAT.  Almost all modern MBT's have 
spaced armor, and almost all the rest are refitted with reactive 
(explosive) armor.  To counter these counters, some countries have 
devised dual-warhead HEAT munitions (ie, one warhead to penetrate 
the outer layer, and the other on a slight time-delay to penetrate 
the inner layer).  The Hellfire missile, carried by the Apache and 
some other US platforms, is a dual-warhead HEAT munition.

  By some estimates (since the precise composition, configuration, 
and effectiveness of the Chobham armor are guarded secrets), the 
Russian AT-15 150mm dual-warhead HEAT missile would be capable of 
defeating the M1A2's chobham armor on its frontal arc.  I don't 
remember the exact mass of its warheads offhand, but iirc it's in 
the ballpark of 50kg (sum of both).

  HESH ("High Explosive Squash-Head") is considered an inferior 
alternative to HEAT as an anti-tank munition.  A HESH warhead is 
comprised of a malleable mass of plastic high explosive, with a 
detonator in its base, enclosed in a thin outer shell.  When the 
HESH round hits its target, the explosive splats against it and 
spreads thin, somewhat resembling a cow-patty.  The detonator hits 
last, and the spread-out explosive transmits a wide, sharp shock 
wave through the impacted surface.  It was invented as a way of 
destroying concrete fortifications, but it was accidently found to 
be very effective against tanks with homogeneous (not spaced or 
laminated) armor, since the shock wave passes through the armor 
without penetrating it, and causes "spall" (little bits of metal 
broken off the inside armor surface) to kill the crew.  It was 
pretty neato at the time, but advances in armor overtook it very 
quickly.  The US doesn't have a HESH munition, but some NATO 
countries do, the UK in particular.  The Scorpion light tank, which 
has a very small and low-pressure main gun, carries HESH munitions 
as a matter of course -- it's still a great round for destroying 
hardened buildings, and lightly-armored or old-armor vehicles too, 
if you don't have anything better (there are lots and lots of old 
russian T-55 tanks rolling around the world, and HESH would be 
effective against them).

  Just for the sake of completeness, I should note that HEAT is 
widely considered inferior to a good APFSDS round fired from a 
high-pressure main gun.  America has metric buttloads of depleted 
uranium sitting around, which just happens to make really great 
penetrator rods for APFSDS munitions, which are simple kinetic 
energy weapons (ie, you fire the long, thin, saboted penetrator 
rod and make it go really fast, and when it hits the target it 
(hopefully) penetrates the armor).  Making a good armor against 
a good APFSDS is harder than making a good armor against HEAT.

  The potential advantage I was thinking of, when asking about 
using really big HESH to kill an M1A2, is that HESH munitions are 
cheap and easy to make.  They don't require the precise machining 
you need to make HEAT.  Precise machining is relatively cheap and 
available in rich, advanced America, but harder to come by in the 
countries where the M1A2 would be deployed.  (And America has a 
nasty tendency to bomb facilities in those countries which can do 
such precise machining.)

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[ WarPragmatics ] Message 897 (55 left): Tue Jan 29, 2002  12:00am
From: TTK here..
Subject: Re(894): ^^^

  Heh :-) actually, that's not too far from the truth.  The 
original molotov cocktail was sometimes used effectively against 
tanks' air intake, by throwing it against the tank's aft-deck.  
When the flaming fuel/motor-oil mix was sucked into the engine, 
it would lose power and occasionally stall altogether because 
of the reduced airflow.  Also, the engine's radiator is usually 
located just inside the air intake vent, and having hot flaming 
fuel covering its radiator would sometimes cause the engine to 
seize up.

  I don't know whether that would be effective against the M1 or 
not, but I doubt it matters much.  Supporting infantry is always 
used to keep enemy infantry away from our tanks (else they can do 
all sorts of mischief), and anyone with artillery good enough to 
precisely lob a napalm bomb onto the aft-deck of a tank is probably 
rich enough to afford "real" anti-tank weapons.

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[ WarPragmatics ] Message 899 (53 left): Tue Jan 29, 2002  12:00am
From: little punk
Subject: Re(892): ^^^

I knew that much.  I wasn't sure if there had been an iteration in chobham
technology or not. 

Incidentally, you did omit the discussion of reactive armor which would sound
ineffective against a HESH.  Is that accurate?

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[ WarPragmatics ] Message 900 (52 left): Tue Jan 29, 2002  12:00am
From: TTK here..
Subject: clarification

  The molotov-vs-tank didn't so much reduce the air flow, as the 
amount of oxygen in the air that flowed (since it would consume 
it in its own burning action).

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[ WarPragmatics ] Message 901 (51 left): Tue Jan 29, 2002  12:00am
From: TTK here..
Subject: Re(899): Re(892): ^^^

  That is accurate.  Reactive armor is ineffective against HESH.

  Frankly, I don't know what the state of the art in chobham-style 
armor is, and I suspect those that know (eg, George) won't tell. 
If I understand correctly, the UK (who invented it), Americans, and 
Germans all have their own implementations of chobham armor, and 
they are all more or less contemporary with each other.

  The German Leopard-II's chobham armor is lighter/thinner than 
the M1A2's, making the Leopard-II much more nimble and capable of 
using bridges, etc, while still proofing it against most attacks 
(and incidentally making it harder to hit, and easier to overrun 
enemy forces).

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[ WarPragmatics ] Message 902 (50 left): Tue Jan 29, 2002  12:00am
From: kzin
Subject: Re(896): HEAT vs HESH

>  Just for the sake of completeness, I should note that HEAT is 
>widely considered inferior to a good APFSDS round fired from a 
>high-pressure main gun.

You sure about that?  I know I haven't followed this stuff in about
10 years, but I know that the physics of the HEAT liquid-metal
penetrator and the penetrator dart of an APFSDS round are identical.
And, the HEAT penetrator doesn't have to worry about as much aerodynamic
drag (to slow it down and degrade its penetration) over its very small
range to target vs the sabot penetrator's relatively long range.

Though, I suppose that could balance against the copper vs DU used
in each.  I think that about the time I was really studying the shaped
vs sabot stuff, tungsten was still the main sabot penetrator material.
DU could have altered that equation quite a bit. (though, now I'm trying
to remember if tungsten was the corrent memory there)


I've always wondered how much it would alter the dynamics of the armor
if you filled the spacing with water.  Though, admittedly, it would
only really help you against the first hit, and after that it might be
fairly useless (until you plugged the hole and refilled).  But it
might help to disperse the shockwave, and act as another type of reaction
to the penetrator, especially a liquid metal penetrator (and especially
if the water is pressurized, if it might provide extra drag as the
breach in the compartment causes the water to try to squirt back out
against the penetrator).  Not that it would completely cool the liquid
penetrator, but that it could cause some irregular partial cooling
which would disrupt the penetrator _enough_ to degrade it's ability
to penetrate the inner armor layer.

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[ WarPragmatics ] Message 903 (49 left): Tue Jan 29, 2002  12:00am
From: TTK here..
Subject: Re(902): Re(896): HEAT vs HESH

  I'm just a layperson; all I know is that the consensus among the 
supposed experts is that a good APFSDS is better.  Also, American 
forces in Desert Storm carried primarily APFSDS, though that may 
have been so that we could dump a few tons of depleted uranium in 
someone else's country while we had an excuse to do so (and we did 
supposedly fire off significant tonnage of the stuff, according to 
sources in sci.military.moderated).

  DU vs tungsten does change the equation significantly.  DU has 
the (apparently fortuitous, rather than designed) qualities of self-
sharpening as it ablates on its way through armor, and of igniting 
on its way through too, making it a better penetrator than tungsten 
and spewing flaming toxic death on the tank's innards when it does 
penetrate.  I think tungsten is still the primary penetrator metal 
in Russian APFSDS, though.

  HEAT's main advantage in today's battlefield is that it doesn't 
have to impact at a high velocity, since as you point out the actual 
penetrator gets its energy from the explosive part at time of impact. 
This makes it suitable for (relatively) slow-moving missiles, which 
have a longer range than a tank's main gun, and self-guiding ability, 
and also for small or low-pressure main guns.

  Regarding filling the spacing with water, the russian T-80U does 
something sort of like that; it fills the space in-between with a 
malleable lightweight plastic, with ceramic tiles suspended inside. 
Some Iraqi tanks fill their armor spacing with layers of rubber and 
aluminum, which is apparently somewhat effective.

  (Frankly, something I haven't been able to figure out is whether 
there are *any* modern MBT's which have air-filled cavities in 
their spaced armor, or if they all use fillers.  Someday when I have 
money, I should buy some of the Jane's Defense books and read them. 
They probably spell out that kind of thing.)

  George knows this kind of stuff really well .. maybe he can speak 
to (at least speculate) the effects of water on APFSDS?  My primary 
thought is that water would be too heavy to be worthwhile (since the 
point of spaced armor is to increase protection while reducing mass) 
but again, I'm just a layperson.

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[ WarPragmatics ] Message 904 (48 left): Tue Jan 29, 2002  12:00am
From: George
Subject: Effects of water...

...would be like the effects of diesel fuel.  Strangely enough,
the hull front armor package on the Abrams utilizes its two
hull front fuel tanks as part of the protection system.  In fact,
Burlington (commonly known as Cohbham after the research establishment
which discovered it) was developed by researchers looking at fuel tank
usage in armor systems.

Particularly against shaped charges, large depths of a mildly resistant
liquid are an excellent protection mechanism, with actually a higher
resistance per unit weight of material than steel gives, diesel fuel
having about 3.1 times as much resistance per unit weight as steel.

The generic formula is a square-root of the relative densities.
This is based on the hydrodynamic model for shaped charge jets,
which is the most accurate.

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[ WarPragmatics ] Message 905 (47 left): Tue Jan 29, 2002  12:00am
From: kzin
Subject: ^^

That'd make sense (re: cohbham and fuel tanks) since the workups
I've seen about cohbham are basically squared off tubes of armor
filled with a composite, and then offset in each row of depth (and
then coated with another composite).

(or was it filled and/or coated with a ceramic?  I don't remember)

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[ WarPragmatics ] Message 906 (46 left): Tue Jan 29, 2002  12:00am
From: The Elder Dan
Subject: Re(902): Re(896): HEAT vs HESH

> I've always wondered how much it would alter the dynamics of the armor
> if you filled the spacing with water.  Though, admittedly, it would
> only really help you against the first hit, and after that it might be
> fairly useless (until you plugged the hole and refilled).

You might be able to alleviate this somewhat if the water were in cells of
 some sort of lightweight but fairly strong material, something elastic so
 that the dispersal could travel from cell to cell but the actual cell(s)
 that were pierced would be the only place water was lost.

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[ WarPragmatics ] Message 907 (45 left): Tue Jan 29, 2002  12:00am
From: TTK here..
Subject: Re(905): ^^

  I'm curious, where did you see these workups?  And what shape 
exactly were these "squared off" tubes?  Do you have any idea 
what the composites inside and outside of the tubes were?

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[ WarPragmatics ] Message 908 (44 left): Tue Jan 29, 2002  12:00am
From: kzin
Subject: Re(903): Re(902): Re(896): HEAT vs HESH

> to (at least speculate) the effects of water on APFSDS?  My primary 
> thought is that water would be too heavy to be worthwhile (since the 
> point of spaced armor is to increase protection while reducing mass) 

Depends on what your purpose is in reducing mass.  You might be able
to arrange it such that you fill the water tank(s) on station, which
still makes them heavier during deployment, but not during transport
(via ship or airplane).


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[ WarPragmatics ] Message 909 (43 left): Tue Jan 29, 2002  12:00am
From: kzin
Subject: Re(907): Re(905): ^^


>   I'm curious, where did you see these workups?  And what shape 
> exactly were these "squared off" tubes?  Do you have any idea 
> what the composites inside and outside of the tubes were?

1) it was a data book on the gulf war, explaining about different
armor depths of different tank models, the effective penetration of
different rounds (rated in ability to penetrate inches of plain steele),
etc.  It tried to give a basic overview of cohbham armor.  It wasn't
a game book, but it was written/published by a game company (GDW), and
was marketed more toward the public than toward their game customers
(though, they also did ANOTHER book which was marketed to gamers, with
similar titles and similar names, but very different interior information.)

I have no idea where my copy is (it's in storage _somewhere_).

That's where most of my memory of it comes from.  But I've also seen
stuff on cohbham from other sources.  Nothing I could specifically
name, though.


2) probably "rounded square" is a better descritor.  Think of rectangular
tubes where the edges have been rounded instead of being sharp corners.
And the thickness is maybe 10% of the overall width of the tube.  Sorta
like:

   +--------+
   |        |
   |        |

where the +'s are rounded instead of sharp, and the straight pieces are
1/10th of the measure of the entire width shown.

3) No memory at all of what the composite or ceramic materials actually
were.  I'll give a basic look through my boxes to see if I can find the
book, and if I do find it, I'll give a more detailed summary.  But I
don't think they said anything more than "ceramic" and/or "composite"
either.  It was a book for the general public, not for people designing
tanks :-)  (I thought it was a kind of interesting book, but was actually
wanting something with game material in it, and was so disappointed that
I didn't even look at their later book (the one that WAS gamer oriented)
until after they were both out of print).