An explosively formed penetrator (EFP), also known as an explosively formed projectile (EFP), a self-forging warhead, or a self-forging fragment, is the product of a
shaped charge
A shaped charge is an explosive charge shaped to form an explosively formed penetrator (EFP) to focus the effect of the explosive's energy. Different types of shaped charges are used for various purposes such as cutting and forming metal, init ...
designed to penetrate
armor
Armour (British English) or armor (American English; see spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially direct contact weapons or projectiles during combat, or fr ...
effectively. As the name suggests, the effect of the explosive charge is to deform a metal plate into a jet, slug or rod shape and accelerate it toward a target. They were first developed as
oil well perforators by American oil companies in the 1930s, and were deployed as weapons in World War II.
Difference from conventional shaped charges
A
shaped charge
A shaped charge is an explosive charge shaped to form an explosively formed penetrator (EFP) to focus the effect of the explosive's energy. Different types of shaped charges are used for various purposes such as cutting and forming metal, init ...
generally has a metal liner that is forced by an explosive blast into a metal jet or slug able to penetrate thick steel armor and knock out vehicles. A disadvantage of this arrangement is that the jet of metal loses effectiveness the further it travels, as it breaks up into disconnected particles that drift out of alignment.
An EFP operates on the principle designed to form a distinct projectile (slug or jet), permitting it to penetrate armor at distance. The dish-shaped liner of an EFP can generate a number of distinct projectile forms, depending on the shape of the plate and how the explosive is detonated.
An EFP's penetration is affected by the density of its liner metal. At 16.654 g/cm
3,
tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that is ...
is preferable in delivery systems that have limitations in size, like the
SADARM, which is delivered by a
howitzer
A howitzer () is a long- ranged weapon, falling between a cannon (also known as an artillery gun in the United States), which fires shells at flat trajectories, and a mortar, which fires at high angles of ascent and descent. Howitzers, like ot ...
. For other weapon systems without practical limitations on warhead diameter, a less expensive copper liner (8.960 g/cm
3) of double the diameter can be used instead. An EFP with a tantalum liner can typically penetrate steel armor of a thickness equal to its diameter – or half that amount with a copper liner instead. By contrast, a conventional shaped charge can penetrate armor up to six times its diameter in thickness, depending on its design and liner material.
Some 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, which causes the liner to fragment into multiple penetrators.
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 a target can be finely controlled based on the design of the liner and the manner in which the explosive charge is detonated. A nuclear-driven MEFP was apparently proposed by a member of the
JASON group in 1966 for terminal
ballistic missile defense
Missile defense is a system, weapon, or technology involved in the detection, tracking, interception, and also the destruction of attacking missiles. Conceived as a defense against nuclear-armed intercontinental ballistic missiles (ICBMs), ...
. A related device was the proposed
nuclear pulse propulsion
Nuclear pulse propulsion or external pulsed plasma propulsion is a hypothetical method of spacecraft propulsion that uses nuclear explosions for thrust. It originated as Project ''Orion'' with support from DARPA, after a suggestion by Stanislaw ...
unit for
Project Orion.
Extensive research is going on in the zone between jetting charges and EFPs, which combines the advantages of both types, resulting in very long stretched-rod EFPs for short-to-medium distances (because of the lack of aerostability) with improved penetration capability.
EFPs have been adopted as warheads in a number of weapon systems, including the
CBU-97
The CBU-97 Sensor Fuzed Weapon is a United States Air Force -class freefall Cluster Bomb Unit. It was developed and produced by Textron Defense Systems. A CBU-97 used in conjunction with the Wind Corrected Munitions Dispenser guidance tail kit i ...
and
BLU-108 air bombs (with the Skeet
submunition
A cluster munition is a form of air-dropped or ground-launched explosive weapon that releases or ejects smaller submunitions. Commonly, this is a cluster bomb that ejects explosive bomblets that are designed to kill personnel and destroy vehicl ...
), the
M303 Special Operations Forces demolition kit The M303 Special Operations Forces demolition kit is a kit containing various metal and plastic parts which the SOF operator packs with C4 explosive to produce a shaped charge or an explosively formed penetrator. The kit also contains a tripod
...
, the
M2/M4 Selectable Lightweight Attack Munition (SLAM), the
SADARM submunition, the
SMArt 155
SMArt 155 is a German 155 mm artillery round, designed for a long range, indirect fire top attack role against armoured vehicles. The SMArt carrier shell contains two submunitions with infrared sensor and millimeter wave radar, which descen ...
top-attack artillery round, the
Low Cost Autonomous Attack System, and the
TOW-2B anti-tank missile
An anti-tank guided missile (ATGM), anti-tank missile, anti-tank guided weapon (ATGW) or anti-armor guided weapon is a Missile guidance, guided missile primarily designed to hit and destroy Armoured fighting vehicle, heavily armored military v ...
.
Use in improvised explosive devices
![Improvised explosive device explosively formed penetrator Iraq](https://upload.wikimedia.org/wikipedia/commons/b/be/Improvised_explosive_device_explosively_formed_penetrator_Iraq.jpg)
EFPs have been used in
improvised explosive device
An improvised explosive device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mechan ...
s against
armoured cars
Armored (or armoured) car or vehicle may refer to:
Wheeled armored vehicles
* Armoured fighting vehicle, any armed combat vehicle protected by armor
** Armored car (military), a military wheeled armored vehicle
* Armored car (valuables), an arm ...
, for example in the 1989 assassination of German banker
Alfred Herrhausen (attributed to the
Red Army Faction
The Red Army Faction (RAF, ; , ),See the section "Name" also known as the Baader–Meinhof Group or Baader–Meinhof Gang (, , active 1970–1998), was a West German far-left Marxist-Leninist urban guerrilla group founded in 1970.
The ...
) and by
Hezbollah
Hezbollah (; ar, حزب الله ', , also transliterated Hizbullah or Hizballah, among others) is a Lebanese Shia Islamist political party and militant group, led by its Secretary-General Hassan Nasrallah since 1992. Hezbollah's parami ...
in the 1990s. A recent development is their widespread use in
IEDs
An improvised explosive device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mecha ...
by
insurgents in Iraq against coalition vehicles.
The charges are generally cylindrical, fabricated from commonly available metal pipe, with the forward end closed by a concave 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.
The effects of traditional explosions like blast-forces and metal fragments seldom disable armored vehicles, but the explosively formed solid copper penetrator is quite lethal—even to the new generation of
mine-resistant vehicles (which are made to withstand an
anti-tank mine
An anti-tank mine (abbreviated to "AT mine") is a type of land mine designed to damage or destroy vehicles including tanks and armored fighting vehicles.
Compared to anti-personnel mines, anti-tank mines typically have a much larger explosive c ...
), and many tanks.
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.
Detonation is controlled by
cable
Cable may refer to:
Mechanical
* Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof
* Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...
,
radio control
Radio control (often abbreviated to RC) is the use of control signals transmitted by radio to remotely control a device. Examples of simple radio control systems are garage door openers and keyless entry systems for vehicles, in which a small ...
,
TV or IR remote controls, or remote arming with a
passive infrared sensor
A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors. PIR sensors are commonly used in security alarms ...
, or via a pair of ordinary cell phones. EFPs can be deployed singly, in pairs, or in arrays, depending on the
tactical situation.
Non-circular explosively formed penetrators
Non-circular explosively formed penetrators can be formed based on modifications to the liner construction. For instance, U.S. patents 6606951 and 4649828 are non-circular in design. US6606951B1 is designed to launch multiple asymmetric explosively forged penetrators horizontally in 360 degrees. US4649828A is designed to form several clothespin shaped EFPs, increasing hit probability.
In addition, a simplified EFP (SIM-EFP) can be made using a rectangular liner, similar to a
linear shaped charge or modified platter charge. This design can be further modified to be similar to US4649828A with multiple cut and bent steel bars lined side by side instead of a singular liner.
In Northern Ireland similar devices have been discovered that were developed by dissident Republican groups for intended use against the police.
In Northern Ireland, the weapon was first used in March 2014 when a PSNI Land Rover was targeted as it travelled along the Falls Road in west Belfast.
A police car was destroyed by an EPF detonated by a command wire in Strabane, Co Tyrone on 18 November 2022.
Asteroid impactor
The spacecraft ''
Hayabusa2
is an asteroid sample-return mission operated by the Japanese state space agency JAXA. It is a successor to the ''Hayabusa'' mission, which returned asteroid samples for the first time in June 2010. ''Hayabusa2'' was launched on 3 December 2 ...
'' carried a small carry-on impactor. It was dropped off ''Hayabusa2'' on to an asteroid and detonated. The explosion created a copper explosively formed penetrator, which hit the asteroid with a velocity of 2 km/s. The crater created by the impact was a target for further observations by the onboard instruments. The shaped charge consisted of 4.5 kg of plasticized
HMX and a 2.5 kg copper liner.
See also
*
High-explosive anti-tank
High-explosive anti-tank (HEAT) is the effect of a shaped charge explosive that uses the Munroe effect to penetrate heavy armor. The warhead functions by having an explosive charge collapse a metal liner inside the warhead into a high-velocity ...
*
M21 mine The M21 is a circular United States anti-tank landmine that uses a Misznay Schardin effect warhead. The mine uses an M607 pressure fuse, which can be adapted as a tilt rod fuze. The mine is triggered either by pressure, or by the tilt rod being fo ...
(landmine which uses an EFP)
*
MAHEM
*
Misznay–Schardin effect
The Misznay–Schardin effect, or platter effect, is a characteristic of the detonation of a broad sheet of explosive.
Description
Explosive blasts expand directly away from, and perpendicular to, the surface of an explosive. Unlike the blast ...
*
Munroe effect
A shaped charge is an explosive charge shaped to form an explosively formed penetrator (EFP) to focus the effect of the explosive's energy. Different types of shaped charges are used for various purposes such as cutting and forming metal, ini ...
*
TMRP-6
The TMRP-6 (Serbo-Croatian, Croatian, Bosnian : ''Protivtenkovska Mina Razorno Probojna -6'', Cyrillic script : ''Противтенковска Мина Разорно Пробојна -6'' ) is a former Yugoslavian anti tank EFP mine.
Histo ...
(landmine which uses an EFP)
References
Further reading
* ''Fundamentals of Shaped Charges'', W.P. Walters, J.A. Zukas, John Wiley & Sons Inc., June 1989,
* ''Tactical Missile Warheads'', Joseph Carleone (ed.), Progress in Astronautics and Aeronautics Series (V-155), Published by AIAA, 1993,
* ''The Good Soldiers'', David Finkel, Picador, 2009,
External links
Photo of a Canadian "Mach 6 aerodynamic EFP"
Video of EFP trying to take out a Humvee
{{DEFAULTSORT:Explosively Formed Penetrator
Ammunition
Bombs
Explosives
Improvised explosive devices
Tactics of the Iraqi insurgency (2003–2011)