The Air Force Research Laboratory (AFRL) was formed in October 1997. has a budget this year of US$1.2 BN is based at Wright-Patterson Air Force Base (WPAFB) and has the goal of discovering, integrating and delivering affordable technologies for improved warfighting by leading a partnership of government, industry, and academia.

Dr. James N. Wilson, Dr. David E. Lambert, and Mr. Joel B. Stewart, of the AFRL are available to give you a guide to the basic physics and operation of these devices. You can find a very handy guide here.

Scientists use design models and shock physics codes to predict terminal shape of projectiles.

Explosively formed projectiles (EFP) are a form of what in the Middle Ages were called Petards. A heavy metal balst proof cylinder is charged with explosive,and stopped up with a metal ball. Through a lit fuse the explosive force drive forward, hopefull knocking a few men over, walls down.

Sometimes the whole damn thing exploded and killed the operator - Hoist on their own petard!

The modern EFP ( or what the militaru and the Press like to call an Improvised Explosive Device) uses these simple principles but adds a sophistication, which is inexpensive, easily constructed and lethal, especially to lightly armoured vehicles.

The leap forward was when quite independently during World War two scientists Misznay, a Hungarian, and Schardin, a German discovered what is now called the Misznay-Schardin effect . Simply, when a sheet of explosive detonates in contact with a heavy backing surface (for example, a metal plate), the resulting blast is primarily directed away from the surface in a single direction. Schardin spent some time developing the device as a side-attack anti-tank weapon, but development was incomplete at the end of the war.

Development was taken up after the war in the USA which led to the Claymore mine which used steel balls as projectiles - this ultimately became the Claymore M18A1 Anti-personnel mine

A simple Misznay-Schardin device consists of a strong metal circular cylinder of explosive, with a shallow cavity in one end that is fitted with a thin metallic liner. Upon detonation, the liner (copper or an alloy ) dynamically transforms into an aerodynamic projectile traveling at high velocity (typically 1500-2000 m/s).

Pic shows the dynamic deformation.

With a mass of 500 g or more, a velocity of 2000 m/s, and kinetic energy on the order of 1 MJ, these projectiles are capable of penetrating more than 10 cm of armor.

The design of the liner is critical and ultimately computerised analysis has shown various trade offs in design - the Geometry of the top surface of the liner relative to the bottom surface changes the mass distribution and strength of the liner across its radius. These effects determine the shape of the liner late in the EFP formation process. While the explosive charge accelerates the liner, the center begins to move with a greater velocity than the outer edge resulting in the deformed, molten hot slug , too thick or thin and edge leads to break up . A correctly designed liner balances the competing effects and forms the perfect and most lethal projectile.

The IED is basically a steel tube, maybe the bottom of a gas cylinder, packed with explosive - of which the Iraqi's seem to have plentiful supplies - with a concave face, the prepared copper liner fitted. (see pic ***) Detonation after selecting a sutiable site is bu electrical firing and may be manually remote or triggered by something as simple as a trip wire, or a passive infra red detector and by wireless - although signals can readily be suppressed.

Something that can and is knocked up in any modest workshop. Cheap, highly effective and frighteningly effective - especially if used in multiples like a Stalin organ.

No need to trouble the munitions manufacturers of Iran.

*** The 3 anonymous guys who introduced these fmailiar pictures if Iranian weapons found in Iraq forbid any pictures, filming,mobils were consfiscated for the Press conference, no devices were shown, just the pictures.

Surprise surprise ..... CNN - "Top general casts doubt on Tehran's link to Iraq militias" Video available.