Explosively formed penetrator

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Formation of an EFP warhead. USAF Research Laboratory. Explosively formed penetrator.gif
Formation of an EFP warhead. USAF Research Laboratory.

An explosively formed penetrator (EFP), 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 armor effectively, from a much greater standoff range than standard shaped charges, which are more limited by standoff distance. As the name suggests, the effect of the explosive charge is to deform a metal plate into a 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. [1] [2]

Contents

Difference from conventional shaped charges

Formation of an EFP Explosively formed penetrator animate.gif
Formation of an EFP
MPB mine showing the face of its explosively formed penetrator Mina-MPB.jpg
MPB mine showing the face of its explosively formed penetrator

A conventional shaped charge generally has a conical metal liner that is forced by an explosive blast into a hypervelocity jet of superplastic metal able to penetrate thick 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 same principle, but its liner is designed to form a distinct projectile that will maintain its shape, permitting it to penetrate armor at greater distance. [3] 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. [4]

An EFP's penetration is more strongly affected by the density of its liner metal compared to a conventional shaped charge. At 16.654 g/cm3, tantalum is preferable in delivery systems that have limitations in size, like the SADARM, which is delivered by a howitzer. For other weapon systems without practical limitations on warhead diameter, a less expensive copper liner (8.960 g/cm3) 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. [5] 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. [6]

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. [7] [8] A related device was the proposed nuclear pulse propulsion 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 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 SMArt 155 top-attack artillery round, the Low Cost Autonomous Attack System, the TOW-2B anti-tank missile, and the NASM-SR anti-ship missile.

An EFP eight inches [20 cm] in diameter threw a seven-pound [3 kg] 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 [57 g] and has a muzzle velocity of 900 meters per second.)

— Rick Atkinson, The Washington Post [9]

Use in improvised explosive devices

An improvised explosive device in Iraq. When activated, the concave copper shape on top becomes an explosively formed penetrator. Improvised explosive device explosively formed penetrator Iraq.jpg
An improvised explosive device in Iraq. When activated, the concave copper shape on top becomes an explosively formed penetrator.

EFPs have been used in improvised explosive devices against armoured cars, for example [10] in the 1989 assassination of German banker Alfred Herrhausen (attributed to the Red Army Faction) [11] and by Hezbollah in the 1990s. [12] They saw widespread use in IEDs by insurgents in Iraq against coalition vehicles. [13]

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), and many tanks. [14]

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. [15]

Detonation is controlled by cable, radio control, TV or IR remote controls, or remote arming with a passive infrared sensor, 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 [16] and 4649828 [17] 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. [18] 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. [19] [20] 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. [21] A police car was destroyed by an EFP detonated by a command wire in Strabane, Co Tyrone on 18 November 2022. [22]

Asteroid impactor

The spacecraft Hayabusa2 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. [23]

See also

Related Research Articles

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A rocket-propelled grenade (RPG) is a shoulder-fired rocket weapon that launches rockets equipped with an explosive warhead. Most RPGs can be carried by an individual soldier, and are frequently used as anti-tank weapons. These warheads are affixed to a rocket motor which propels the RPG towards the target and they are stabilized in flight with fins. Some types of RPG are reloadable with new rocket-propelled grenades, while others are single-use. RPGs are generally loaded from the front.

<span class="mw-page-title-main">Warhead</span> Section of a device that contains the explosive agent or toxic material

A warhead is the section of a device that contains the explosive agent or toxic material that is delivered by a missile, rocket, torpedo, or bomb.

<span class="mw-page-title-main">Shaped charge</span> Explosive with focused effect

A shaped charge is an explosive charge shaped 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, initiating nuclear weapons, penetrating armor, or perforating wells in the oil and gas industry.

<span class="mw-page-title-main">Reactive armour</span> Type of vehicle armour

Reactive armour is a type of vehicle armour used in protecting vehicles, especially modern tanks, against shaped charges and hardened kinetic energy penetrators. The most common type is explosive reactive armour (ERA), but variants include self-limiting explosive reactive armour (SLERA), non-energetic reactive armour (NERA), non-explosive reactive armour (NxRA), and electric armour. NERA and NxRA modules can withstand multiple hits, unlike ERA and SLERA.

<span class="mw-page-title-main">Armour-piercing ammunition</span> Ammunition type designed to penetrate armour

Armour-piercing ammunition (AP) is a type of projectile designed to penetrate armour protection, most often including naval armour, body armour, vehicle armour.

<span class="mw-page-title-main">Composite armour</span> Type of vehicle armour

Composite armour is a type of vehicle armour consisting of layers of different materials such as metals, plastics, ceramics or air. Most composite armours are lighter than their all-metal equivalent, but instead occupy a larger volume for the same resistance to penetration. It is possible to design composite armour stronger, lighter and less voluminous than traditional armour, but the cost is often prohibitively high, restricting its use to especially vulnerable parts of a vehicle. Its primary purpose is to help defeat high-explosive anti-tank (HEAT) projectiles.

<span class="mw-page-title-main">Terminal ballistics</span> Projectiles behavior after reaching their targets

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<span class="mw-page-title-main">High-explosive anti-tank</span> Type of shaped charge explosive

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 shaped charge jet; this is capable of penetrating armor steel to a depth of seven or more times the diameter of the charge. The shaped charge jet armor penetration effect is purely kinetic in nature; the round has no explosive or incendiary effect on the armor.

A tandem-charge or dual-charge weapon is an explosive device or projectile that has two or more stages of detonation, assisting it to penetrate either reactive armour on an armoured vehicle or strong structures.

<span class="mw-page-title-main">Anti-tank mine</span> Type of land mine designed to destroy tanks

In anti-tank warfare, an anti-tank mine is a type of land mine designed to damage or destroy vehicles including tanks and armored fighting vehicles.

<span class="mw-page-title-main">Vehicle armour</span> High-strength plating used to fortify important vehicles against bullets, shells etc.

Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighting vehicles like tanks, aircraft, and ships.

<span class="mw-page-title-main">CBU-97 Sensor Fuzed Weapon</span> Anti-vehicle "smart" cluster bomb

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The following is a list of ammunition fired by the 125 mm smoothbore gun series used in the T-64, T-72, T-80, M-84, T-90, PT-91, T-14 Armata, and other tanks derived from those designs, as well as the 2A45 Sprut anti-tank gun.

An active protection system (APS) is a system designed to actively prevent certain anti-tank weapons from destroying a vehicle.

<span class="mw-page-title-main">Spaced armour</span> Armour with plates spaced a distance apart

Armour with two or more plates spaced a distance apart falls under the category of spaced armour. Spaced armour can be sloped or unsloped. When sloped, it reduces the penetrating power of bullets and solid shot, as after penetrating each plate projectiles tend to tumble, deflect, deform, or disintegrate; spaced armour that is not sloped is generally designed to provide protection from explosive projectiles, which detonate before reaching the primary armour. Spaced armour is used on military vehicles such as tanks and combat bulldozers. In a less common application, it is used in some spacecraft that use Whipple shields.

<span class="mw-page-title-main">Top-attack</span> Top-attack is a weapon employment or targeting method, usually used against armoured vehicles.

A top attack weapon is designed to attack armored vehicles from above, to take advantage of the fact that the armour is usually thinnest on the top of an armoured vehicle. The device may be delivered as a smart submunition or a primary munition by an anti-tank guided missile (ATGM), mortar bomb, artillery shell, or even an emplaced munition such as a mine. Top attack munitions use either a shaped charge warhead, or an explosively formed penetrator (EFP) warhead fired while over the target.

<span class="mw-page-title-main">Selectable Lightweight Attack Munition</span> Dark green, small explosive device.

Selectable Lightweight Attack Munition or is a small United States multi-purpose landmine produced by ATK Precision Fuze Company in Janesville, Wisconsin from 1992 to 2002. It has a passive infrared sensor, and a magnetic influence sensor which allow it to be used as a demolition munition, off-route mine, or full width belly attack mine.

<span class="mw-page-title-main">Krakatoa (explosive)</span> Modular explosive used for ordinance disposal & demolitions

Krakatoa is a modular explosive device used for explosive ordnance disposal (EOD) or demolitions developed by the British company Alford Technologies. The device is designed to fire a number of different projectiles, operates both in air and underwater, and can be used in a vertical or horizontal orientation.

<span class="mw-page-title-main">Ammunition</span> Material fired, scattered, dropped, or detonated from a weapon or weapon system

Ammunition is the material fired, scattered, dropped, or detonated from any weapon or weapon system. Ammunition is both expendable weapons and the component parts of other weapons that create the effect on a target.

Beyond-armour effect is a term coined by Försvarets Fabriksverk (FFV), a semi-governmental Swedish defense firm, while developing the AT4. From the 1980s this phrase was used in its brochures, press releases, weapon instruction manuals and other documentation to denote the post-penetration effect of the AT4's HEAT anti-armour warhead against the interior and occupants of armoured vehicles.

References

  1. ↑ Ismay, John (2013-10-18), "The Most Lethal Weapon Americans Faced in Iraq", At War blog, The New York Times, archived from the original on 2018-01-04, retrieved 2018-03-26
  2. ↑ William P. Walters (1 October 1990). "The Shaped Charge Concept, Part III. Applications of Shaped Charges" (PDF). U.S. Army Ballistic Research Laboratory. Archived (PDF) from the original on 28 April 2017. Retrieved 26 March 2018.
  3. ↑ "DoD Directive 2000.19E, "Joint Improvised Explosive Device Defeat Organization (JIEDDO)", February 14, 2006". Archived from the original on February 15, 2007. Retrieved February 13, 2007.
  4. ↑ "U.S. Air Force Research Laboratory description of an EFP". Archived from the original on 2006-03-16. Retrieved 2006-03-29.
  5. ↑ ng.pdf, on the web, US military testing of SOFDK
  6. ↑ U.S. Patent 5540156: Selectable effects EFP warhead
  7. ↑ Explosively Produced Flechettes; JASON report 66-121, Institute for Defense Analysis, 1966
  8. ↑ Interview with Dr. Richard Blankenbecler Archived 2011-09-12 at the Wayback Machine
  9. ↑ Atkinson, Rick (1 October 2007). "There was a two-year learning curve ... and a lot of people died in those two years". The Washington Post . Archived from the original on 4 December 2016. Retrieved 24 December 2010.
  10. ↑ Stratfor, "The Imminent Spread of EFPs" Archived 2020-01-03 at the Wayback Machine , April 11, 2007
  11. ↑ Hambling, David (July 29, 2008). "Superbomb Mystery: The Herrhausen Assassination". Wired. Archived from the original on January 18, 2009. Retrieved November 5, 2008.
  12. ↑ Gareth Porter (October 25, 2008). "POLITICS: U.S. Military Ignored Evidence of Iraqi-Made EFPs". Archived from the original on 2008-11-12. Retrieved 2008-11-05.
  13. ↑ Robert Bryce (January 22, 2007). "Surge of danger for US troops". Salon. Archived from the original on 2008-06-27.
  14. ↑ "The truck the Pentagon wants and the firm that makes it - USATODAY.com". usatoday30.usatoday.com. Archived from the original on 2012-06-26. Retrieved 2020-07-09.
  15. ↑ Correspondent, Sean Rayment, Defence (2006-06-24). "The precision-made mine that has 'killed 17 British troops'". The Daily Telegraph. ISSN   0307-1235. Archived from the original on 2020-07-09. Retrieved 2020-07-09.{{cite news}}: CS1 maint: multiple names: authors list (link)
  16. ↑ Klein, Arnold S. "Bounding anti-tank/anti-vehicle weapon". patents.google.com/. Archived from the original on 2020-02-29. Retrieved 2020-02-29.
  17. ↑ "Explosively forged penetrator warhead". patents.google.com. Archived from the original on 2020-02-29. Retrieved 2020-02-29.
  18. ↑ "How to build your own armour killers". privat.bahnhof.se. Archived from the original on 2020-02-18. Retrieved 2020-02-29.
  19. ↑ "Dungannon man Patrick Carty charged over 'Iraq-style IED'". BBC News. February 13, 2012. Archived from the original on January 2, 2019. Retrieved June 20, 2018.
  20. ↑ "Derry bomb was 'Iraq style mortar'". UTV Live News. 2012-12-07. Archived from the original on 2012-12-13.
  21. ↑ "New IRA claims responsibility for Strabane mortar attack on PSNI". Irish News. November 25, 2022. Retrieved November 25, 2022.
  22. ↑ "New IRA claims responsibility for Strabane mortar attack on PSNI". Irish News. November 25, 2022. Retrieved November 25, 2022.
  23. ↑ Saiki, Takanao; Sawada, Hirotaka; Okamoto, Chisato; Yano, Hajime; Takagi, Yasuhiko; Akahoshi, Yasuhiro; Yoshikawa, Makoto (2013). "Small carry-on impactor of Hayabusa2 mission". Acta Astronautica. 84: 227–236. Bibcode:2013AcAau..84..227S. doi:10.1016/j.actaastro.2012.11.010.

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