[mdlug] OT - IR jamming

[Dave Arbogast]

>Right now, the worst thing out there is a device called
>an EFP (explosively formed projectile).  It's an upgrade
>of a successful assassination method -- the platter charge
>attached to the bottom of a man-hole cover.
>
>An EFP is a steel can, normally set in concrete...the can
>is filled with explosive, with the detonator near the front,
>and then covered with a shallow dish made of copper (concave
>into the can.  When the explosive charge blows, the copper
>blows-outwards while still maintaining a bond with the
>rim of the steel can...as pressure builds, the copper
>distends (easily because it is a ductile metal)...the
>center of the now outward-bowing bowl is travelling
>faster than the edges...once the edges release/tear from
>the rim of the can, they snap inwards...forming a very
>slender projectile, which by this time is moving at a
>speed in the range of Mach 4 to Mach 6.
>
>As you can imagine, this is extremely devastating to
>anything it runs into -- even an M1 tank :-/
>  
>
I think you missed one part of the physics of the copper in a EFP - it 
becomes molten at that point and acts like a plasma cutter when it comes 
in contact with simple armor. That is why the M1 and other advanced 
systems employ composite armor in many places - steel on the outside for 
conventional projectiles, and other layers of other materials 
(classified) to stop the plasma injection. The M60 in the Nam had simple 
steel armor easily penetrated by the Russian RPG with their cone shaped 
copper in the explosive, so the troops would get badly burned from the 
molten copper injecting into the tank. This copper at that point did 
little damage other than burn everything.  So, reactive armor panels 
were added to the outside of the steel - basically explosive charges 
that would detonate when the molten copper entered them, thus blowing 
the plasma away.
-dave

PS - the demolition crews world wide use this technique to topple steel 
structures like old buildings - they have sticks of plastic explosive 
about 2.5" in diameter with about a 1" copper piece in the shape of a 90 
degree right angle running the length of the explosive. It will cut 
through quite a chunk of structural steel.