HEAT...Re: New 'electrical active' Armour to defeat hand held anti-tank rounds

> At 7:29 PM +0200 9/14/02, Oerjan Ohlson wrote:
[snip]

> the plasma 'makes' the electrical circuit which then disrupts the

Ok, sorry to drag up an old conversation here. What is the jet from a shaped
charge. What material state best describes it and it's characteristics?

Ryan: You may find this a bit helpful if anyone questions the "plasma" again.
From:
http://www4.janes.com/K2/doc.jsp?t=Q&K2DocKey=/content1/janesdata/mags/i
dr/history/dsm95/dsm00172.htm@current&QueryText=%3CAND%3E%28%3COR%3E%28%
28%5B80%5D%28HEAT+%3CAND%3E+warheads+%3CAND%3E+plasma%29+%3CIN%3E+body%2
9%2C+%28%5B100%5D%28%5B100%5D%28HEAT+%3CAND%3E+warheads+%3CAND%3E+plasma
%29+%3CIN%3E+title%29+%3CAND%3E+%28%5B100%5D%28HEAT+%3CAND%3E+warheads+%
3CAND%3E+plasma%29+%3CIN%3E+body%29%29%29%29&Prod_Name=IDR&

First paragraph last 1/2, after the heading of Text:

  The 1940s saw the rapid development of High Explosive Anti-Tank (HEAT)
  shaped-charge weapons, which used an explosive-backed copper cone to
melt through armour plate, using the focused energy of hot gas and molten
copper or plasma. This had a dramatic effect on armour configurations and
design, which has lasted for over 50 years.

If Jane's isn't good enough for you, there's many other references out there,
tell me what you consider authoritative and I'll supply the reference.

Although, I do have to agree with the original cut:
  "There is nothing "plasma-like" about the metal jet from a HEAT
round."
Frankly, there's nothing plasma-like.  It _IS_ plasma.

Rand.

[quoted original message omitted]

I don't want to jump *between* the response that may be coming
from Oerjan on this one (that might hurt ^_- ) but I thought I
would offer this quote as a couterpoint to the Jane's reference below:

"Detailed discussions of the shaped charge concept and an extensive list of
sources (too numerous to list here) are available elsewhere, e. g., [1], [2],
[3], [4]. This concept is not well understood by people outside the warhead
community. For example, the jet is not a “cutting plasma”, it is not a
liquefied or molten metal jet, the cone does not impact the armor intact, the
jet temperature is not 20,000 C, and the density of the jet is not several
times that of steel, and the jet does not burn its way through armor, as
reported in many
newspaper, TV, and even semi-technical journal articles."

Referencing Ryan's original question as to what material state best describes
the jet (formed from the liner) from a shaped charge: "The pressures generated
during the liner collapse far exceed the yield strength of the liner material
and thus the liner behaves approximately as an inviscid, incompressible
fluid!"

These are from the introduction to "An Overview of the Shaped Charge Concept"
by William Walters, Department of Mathematical Sciences, US Military Academy,
West Point, NY. Dunno who he is,
but he self-references a few papers or books at the end, so
presumably he's been doing this for a bit.

This article is located at:
www.dean.usma.edu/math/research/msce/11th_AUTS/papers/Walters.pdf

Hope this helps!
                          Aaron

> --- rljoiner@mindspring.com wrote:
http://www4.janes.com/K2/doc.jsp?t=Q&K2DocKey=/content1/janesdata/mags/i
dr/history/dsm95/dsm00172.htm@current&QueryText=%3CAND%3E%28%3COR%3E%28%
28%5B80%5D%28HEAT+%3CAND%3E+warheads+%3CAND%3E+plasma%29+%3CIN%3E+body%2
9%2C+%28%5B100%5D%28%5B100%5D%28HEAT+%3CAND%3E+warheads+%3CAND%3E+plasma
%29+%3CIN%3E+title%29+%3CAND%3E+%28%5B100%5D%28HEAT+%3CAND%3E+warheads+%
3CAND%3E+plasma%29+%3CIN%3E+body%29%29%29%29&Prod_Name=IDR&
> First paragraph last 1/2, after the heading of Text:

> At 1:34 PM -0500 1/13/04, rljoiner@mindspring.com wrote:
again.
> From:

Well, there's a lot of misinformation about the Monroe effect creating plasma
from the liner. I'm really looking for our fried that works on the bloody
things to pipe up. Oerjan?

'really looking for our fried that works on the'

Now, I'm sure he has INTIMATE knowledge of the subject, but fried...?
;->=

*knock of the NBS* For what I'm about to receive...

The_Beast

> Although, I do have to agree with the original cut: "There is

> plasma from the liner. I'm really looking for our fried that works on
As somebody who works with the stuff I can tell you the liner has very little
to do the penetrating effect. We use among other things (linear) shaped
charges to cut through projectile casings that consists of a roll

of flexible explosives with a V shaped incision. All this is embedded in
adhesive backed foam. I really doubt the ability of foam to become
plasma ;-)

Sorry for the delay, Ryan - I got home too late last night to read any
emails :-(

> Ryan Gill wrote:

> Once again, there is no such thing as a "plasma jet" from a HEAT

For metals at least (*) it is best described either as a solid or as a liquid,
depending on exactly what characteristic you're after: it *is* a

solid, but it is under such a high strain that ydrodynamics equations give
a better model for how it deforms than the normal solid-state mechanics
equations do (IOW, it *behaves* roughly as if it were an incompressible
inviscid liquid).

(*) We don't use any of the more exotic liner materials like glass or
ceramics in our warheads, so I have no experience with how they behave -

but I'd be somewhat surprised if they behaved just like metals :-/

If you haven't already, read the paper Aaron quoted (
http://www.dean.usma.edu/math/research/msce/11th_AUTS/papers/Walters.pdf
)
- it is one of the best "shaped charges for dummies" texts I've seen to
date. It doesn't go into how reactive armours work, but it covers the
important aspects of the shaped charges themselves without losing either

itself or the casual reader in complicated maths... and it explicitly
punctures a number of general-public misconceptions along the way <g>

(BTW, Aaron, jumping in front of my response doesn't hurt as long as you're
right and thus save me from extra typing! :-) )

As for the Jane's quote Randall posted, well... it wouldn't be the first

time Jane's got something seriously wrong :-/

Later,

> Ludo Toen wrote:

> Although, I do have to agree with the original cut: "There is

> plasma from the liner. I'm really looking for our fried that works on

Increasing the penetration by a factor of three or more - sometimes
*much*
more - is "very little"?!? OK, in a linear charge applied directly to
the target the liner might not improve the penetration that much, but in
modern military HEAT warheads it certainly does. (Doesn't make the jet any
more

plasma-like, of course <g>)

Later,