Explosively formed penetrator

An explosively formed penetrator (EFP), is a type of petard also known as an explosively formed projectile, a self-forging warhead, or a self-forging fragment, is a special type of shaped charge designed to penetrate armour effectively at stand-off distances. They are also used extensively in the oil and gas industry [http://www.globalsecurity.org/military/systems/munitions/bullets2-shaped-charge.htm] . They were first developed during WWII. [Military.com article on the evolution of hand-held anti-tank technology http://www.military.com/soldiertech/0,14632,Soldiertech_EFP,,00.html]

Difference from conventional shaped charges

USAF Research Laboratory.

A conventional shaped charge generally has a conical metal liner that projects a hypervelocity jet of metal able to penetrate to great depths into steel armour; however, in travel over some distance the jet breaks up along its length into particles that drift out of alignment, greatly diminishing its effectiveness at a distance.

An EFP eight inches in diameter threw a seven-pound copper slug at Mach 6, or 2,000 meters per second. (A .50-caliber bullet, among the most devastating projectiles on the battlefield, weighs less than two ounces and has a muzzle velocity of 900 meters per second.). "Washington Post" [ [http://www.washingtonpost.com/wp-dyn/content/article/2007/09/30/AR2007093001675_5.html http://www.washingtonpost.com/wp-dyn/content/article/2007/09/30/AR2007093001675_5.html] ]

An EFP, on the other hand, has a liner in the shape of a shallow dish.The force of the blast molds the liner into any of a number of configurations, depending on how the plate is formed and how the explosive is detonated. [U.S. Air Force Research Laboratory description of an EFP http://www.afrlhorizons.com/Briefs/Dec04/MN0407.html] Sophisticated EFP warheads have multiple detonators that can be fired in different arrangements causing different types of waveform in the explosive, resulting in either a long-rod penetrator, an aerodynamic slug projectile or multiple high-velocity fragments. A less sophisticated approach for changing the formation of an EFP is the use of wire-mesh in front of the liner: with the mesh in place the liner will fragment into multiple penetrators. [U.S. Patent 5540156: Selectable effects EFP warhead http://www.google.com/patents?id=VHUgAAAAEBAJ&dq=5540156]

In addition to single-penetrator EFPs (also called single EFPs or SEFPs), there are EFP warheads whose liners are designed to produce more than one penetrator; these are known as multiple EFPs, or MEFPs. The liner of an MEFP generally comprises a number of dimples that intersect each other at sharp angles. Upon detonation the liner fragments along these intersections to form up to dozens of small, generally spheroidal projectiles, producing an effect similar to that of a shotgun. The pattern of impacts on target can be finely controlled based on the design of the liner and the manner in which the explosive charge is detonated.

The (single) EFP generally remains intact and is therefore able to penetrate armour at long range, delivering a wide spray of fragments of liner material and vehicle armour backspall into the vehicle's interior, injuring its crew and damaging other systems. [DoD Directive 2000.19E, "Joint Improvised Explosive Device Defeat Organization (JIEDDO)", February 14, 2006 http://www.dtic.mil/whs/directives/corres/html/200019.htm]

As a rule of thumb, an EFP will perforate a thickness of armour equal to only about the diameter of its charge, whereas a typical shaped charge will go through six or more diameters.fact|date=May 2008

EFPs have been adopted as warheads in a number of weapon systems, including the CBU-97 and BLU-108 air bombs (with the Skeet submunition), the M303 Special Operations Forces demolition kit, the M2/M4 Selectable Lightweight Attack Munition (SLAM), the SADARM submunition, the Low Cost Autonomous Attack System and the TOW-2B anti-tank missile.

Use in improvised explosive devices

. ["Salon", "Surge of danger for US troops", January 22, 2007 http://www.salon.com/news/feature/2007/01/22/ieds/print.html]

The charges are generally cylindrical, fabricated from commonly available metal pipe, with the forward end closed by a copper or steel disk-shaped liner to create a shaped charge. Explosive is loaded behind the metal liner to fill the pipe. Upon detonation, the explosive projects the liner to form a projectile at a speed well over 1 km/s, depending on the design and type of explosive used.

Because they use explosives to form a solid copper penetrator instead of using an explosive blast or metal fragments, these charges are extremely dangerous, even to the new generation of MRAPs (which are made to withstand an anti-tank mine), and many tanks. ["USA Today","As explosives in Iraq get deadlier, makers of armored vehicles alter plans", August 2, 2007 http://www.usatoday.com/news/military/2007-08-01-force-protection-mraps_N.htm]

Often mounted on crash barriers at window level, they are placed along roadsides at choke points where vehicles must slow down, such as intersections and junctions. This gives the operator time to judge the moment to fire, when the vehicle is moving more slowly. ["The Telegraph", "The precision-made mine that has killed 17 British troops", June 25, 2006 http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2006/06/25/wirq225.xml&sSheet=/news/2006/06/25/ixnews.html]

Detonation is controlled by cable, radio control, or remote arming with a passive infrared sensor. EFPs can be deployed singly, in pairs, or in arrays, depending on the tactical situation.

References

* "Fundamentals of Shaped Charges", W.P. Walters, J.A. Zukas, John Wiley & Sons Inc., June 1989, ISBN 0-471-62172-2
* "Tactical Missile Warheads", Joseph Carleone (ed.), Progress in Astronautics and Aeronautics Series (V-155), Published by AIAA, 1993, ISBN 1-56347-067-5

ee also

*High explosive anti-tank
*Misznay-Schardin effect
*Munroe effect

External links

* [http://www.military.com/soldiertech/0,14632,Soldiertech_EFP,,00.html Photo of a Canadian "Mach 6 aerodynamic EFP"]
* [http://shock.military.com/Shock/videos.do?displayContent=151465&page=1 Video of EFP trying to take out a Humvee]
* [http://www.liveleak.com/view?i=8b3_1197614944 video of an artillery-borne EFP hitting targets]
* [http://www.liveleak.com/view?i=1c3_1215487601 Video shows EFP disable humvee]