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Message 1 in thread
From: pcallah@ibm.net (pcallah@ibm.net)
Subject: Chobham armour
Newsgroups: sci.military.moderated
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Date: 1997/02/27
From pcallah@ibm.net

     This is what I know about Chobham armour:
     It is very resistant to conventional shaped charges.
     It is made by explosive forging.  This forging uses explosive
lenses of the two different velocity explosives sort so as to make a
"flat" planar compression wave. This was in Popular Science or some
such magazine.
     Reading between the lines, maybe it contains depleted uranium?
     I suspect from machining techniques it contains something like
transition metal nitride spheres - at a wild guess maybe 1 mm
diameter?  Maybe tungsten carbide? or really pure alumina?  What holds
it all together?   Maybe nickel - cobalt?
     Can anyone talk without getting into trouble?

I wonder if this question is prudent.

Paul Callahan

pcallah@ibm.net
Message 2 in thread
From: John M Atkinson (jatkinso@gmu.edu)
Subject: Re: Chobham armour
Newsgroups: sci.military.moderated
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Date: 1997/02/28
From jatkinso@gmu.edu (John M Atkinson)

On Thu, 27 Feb 1997 17:33:04 GMT, pcallah@ibm.net wrote:

%
%From pcallah@ibm.net
%
%     This is what I know about Chobham armour:

<questions snipped>

%     Can anyone talk without getting into trouble?
%
%I wonder if this question is prudent.

Unanswerable without violating security laws in both the US and UK,
don't know about other countries.  Any one who knows can't discuss it.

John M. Atkinson
jatkinso@gmu.edu
It is well that war is so terrible-we would grow too fond of it.
                                              - Robert E. Lee
Message 3 in thread
From: George Herbert (gherbert@crl.com)
Subject: Re: Chobham armour
Newsgroups: sci.military.moderated
View this article only
Date: 1997/03/03
From gherbert@crl.com (George Herbert)

John M Atkinson <jatkinso@gmu.edu> wrote:
>pcallah@ibm.net wrote:
>%     This is what I know about Chobham armour:
><questions snipped>
>%     Can anyone talk without getting into trouble?
>%I wonder if this question is prudent.
>
>Unanswerable without violating security laws in both the US and UK,
>don't know about other countries.  Any one who knows can't discuss it.

It is possible to find a lot of discussions of what it allegedly is
in open sources, enough so that I am reasonably sure I know how it
works after reading through the open materials and could make some
given a good reason and some money.  However, John is correct that
the actual formulas are still classified (lo, after these many years...)
and anyone who knows for sure won't talk about it as doing so is
(in the US) a federal felony espionage act violation etc.  
I think a summation of and discussion about the open source material
isn't inappropriate but all of it could well be wrong, so take anything
you see printed about Chobham/Burlington with a grain of salt.
We could all have the wrong ideas 8-)


-george william herbert
Retro Aerospace
gherbert@crl.com
Message 4 in thread
From: Moo's Access Point (moobox@access.digex.net)
Subject: Re: Chobham armour
Newsgroups: sci.military.moderated
View this article only
Date: 1997/03/12
From moobox@access.digex.net (Moo's Access Point)

>From gherbert@crl.com (George Herbert) 
>I think a summation of and discussion about the open source material
>isn't inappropriate but all of it could well be wrong, so take anything
>you see printed about Chobham/Burlington with a grain of salt.
>We could all have the wrong ideas 8-)

I thought that Chobham came from Brit experiments to make a better
explosion-proof fuel tank.  So basically, you have a bunch of very little
hollow-plated cells/mesh which act to spread out and contain a typical
shaped charge in order to disperse the energy and molten metal.(Which
makes sense if you think about the first evolution against HEAT, which was
spaced armor, then foam stuffed into the spaces). 

Add ceramics for the first generation armor and you have something which
is practically invulnerable to HEAT rounds.

Add depleted uranium or some other very "rigid" material to the cells/mesh
which can slow down or break up long-rod penetrators and you probably
have something close to the M1A2 armor.
-- 
	Doug Mohney				mohney@access.digex.net
 	                    Manager, ISP-TV
				DIGEX
	(V) 301-847-5105 		     	(F) 301-847-5215

Message 5 in thread
From: Damian and Heidi Kneale (damian@ois.com.au)
Subject: Re: Chobham armour
Newsgroups: sci.military.moderated
View this article only
Date: 1997/03/06
From damian@ois.com.au (Damian and Heidi Kneale)

Once jatkinso@gmu.edu (John M Atkinson) inscibed in stone:

><questions snipped>
>
>%     Can anyone talk without getting into trouble?
>%
>%I wonder if this question is prudent.
>
>Unanswerable without violating security laws in both the US and UK,
>don't know about other countries.  Any one who knows can't discuss it.

Not true.  Anyone who has been cleared on a subject already knows
their responsibilities regarding the information (and from what I know
tend to err on the side of caution in questionable cases) but anyone
else is perfectly free to discuss what they know, excepting specific
court orders, or states of emergency.

That said, there isn't much that I know of published regarding the
information you seek (Chobham armour).  Specifics on the makeup of the
armour have been slow to leak to the civilian world.  There may also
be slight variants on Chobham armour as we know it as well.  I don't
know whether the British intend to sell the armour "as is", or as I
suspect that in places such as the US (and possibly Germany) that it's
produced under licence with the respective country having the chance
to "play with the mix" as it were.  

Something to speculate on anyway.  Better yet, anyone who really knows
can't tell me I'm wrong.  *laugh*   The down side of a security
clearance is that you can't tell anyone the groovy things you learn!

Damian
Message 6 in thread
From: Bruce C. Fielder (bfielder@quadrant.net)
Subject: Re: Chobham armour
Newsgroups: sci.military.moderated
View this article only
Date: 1997/03/03
From "Bruce C. Fielder" <bfielder@quadrant.net>

I know nothing about it either, but I can make some guesses.

If it is made by explosive charging, then two metals (or a ceramic and a
metal) are being bonded.  This wouldn't be necessary unless the two
layers had very different properties. Probably, the outside layer is
hard (but brittle); the inside layer is softer, but resists sudden blows
(like, say, an anti-tank missle). The same thing could be done by three
layers: soft metal, ceramic, and hard metal.

The object is to use up the kinetic (and possibly chemical) energy of
the incoming missle before it penetrates the armour.  One thing that
would do it is if the armour fragmented into many small particles
(creating particles causes an increse in surface energy).  I suppose
that this could be done by including hard particles in a softer matrix,
say, as you said, 1 mm tungstun carbide particles in a steel matrix. 
Manufacturing this would require a modification of the sintering
process, perhaps even the blending of the hard particles with the soft
matrix and bonding them with explosives.

If this is an imprudent answer, well, I'm open for a job.

pcallah@ibm.net wrote:
> 
> From pcallah@ibm.net
> 
>      This is what I know about Chobham armour:
>      It is very resistant to conventional shaped charges.
>      It is made by explosive forging.  This forging uses explosive
> lenses of the two different velocity explosives sort so as to make a
> "flat" planar compression wave. This was in Popular Science or some
> such magazine.
>      Reading between the lines, maybe it contains depleted uranium?
>      I suspect from machining techniques it contains something like
> transition metal nitride spheres - at a wild guess maybe 1 mm
> diameter?  Maybe tungsten carbide? or really pure alumina?  What holds
> it all together?   Maybe nickel - cobalt?
>      Can anyone talk without getting into trouble?
> 
> I wonder if this question is prudent.
> 
> Paul Callahan
> 
> pcallah@ibm.net
>

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