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thedrifter
07-09-04, 09:01 AM
INFANTRY 1, TANK 0: Hand-Held Anti-Tank Weapons

Man versus machine, soldiers taking on tanks -- it's been a back-and-forth struggle, but infantry has the current advantage with EFP -- explosively formed penetrators.

It's the classic David and Goliath conflict: infantry versus armored vehicles. At the start of World War II, infantry held the distinct advantage in terms of battlefield survival. Though relatively small, the German 37mm Pak 36 and the British 40mm 2-pounder infantry guns were capable of defeating any armored vehicle in service in 1939, yet were light enough that they could be towed by a jeep, or even picked up and carried by their crews.
Unfortunately, this advantage didn't last long; by 1941 newer tanks had increased their armor. While larger AT guns had come into service to meet these up-armored threats, they were so large that they could only be organized into specialized anti-tank units. If an infantry unit ever found itself attacked by tanks without an attached AT unit, there was little to be done against the tanks. Since infantry were incapable of carrying effective AT guns by themselves, there was a need for a weapon light enough to be man-portable, yet powerful enough to destroy a tank. Sure, demolition charges, anti-tank mines, and grenades were effective in destroying tanks, but they were only useful in extremely confined environments such as villages, where infantry was able to sneak right up to the tank unseen.

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Modern EFP: This Canadian "Mach 6 aerodynamic EFP" was created by explosively deforming a contoured metal liner (photo from DRDC Suffield Website).

No, if these new weapons were going to be of any use, they would need some "standoff" capability which gave the infantry enough cover, while still preserving their ability to attack tanks in open terrain. Thus began the chain of technological innovations which have led to us to Explosively Formed Penetrators (EFP), or Self Forging Fragments.

Panzerfaust: Tank Fist

In 1942 the German Whermacht introduced the Panzerfaust 30. German for tank fist, the Panzerfaust was a hand-held rocket that weighed 10 pounds, had an effective range of 30 yards, and was capable of defeating any armored vehicle fielded during the war. The Panzerfaust (and similar weapons like the American Bazooka, British PIAT, and German Panzerschreck) achieved amazing performance through the use of a point-initiating, base detonating, shaped charge (SC) warhead.

The SC is an explosive compound formed around a metal (usually copper) cone, with the base of the cone oriented on the target. When the SC detonates, the energy wave created travels through the explosive until it reaches the angled walls of the cone. Once there, the wave's energy vector is redirected to a point just in front of the base of the cone, focusing all of the SC's energy upon a single point, thus reducing the copper cone into a superplastic state and superheated gas, called plasma. This metal plasma jet, traveling at the propagation speed of the explosive used to form the plasma (thousands of meters per second) would then strike the target, burning its way through the metal and spraying the interior of the vehicle with superheated gases and molten metal.

With the Panzerfaust and its brethren, infantry once again held the advantage over armored vehicles. While armor still commanded the open areas, it was a foolish tank commander who ventured too close to a village without infantry support. The SC principle was incorporated into full scale anti-tank cannon munitions to give field artillery, as well as other tanks, an anti armor capability. Known as High Explosive, Anti-Tank (HEAT), these munitions had the benefit of being uniformly effective throughout their entire range. Where the armor penetrating capabilities of a kinetic energy round fell off over distance (as the projectile bled off energy), the HEAT rounds were just as effective at their maximum range as they were at point blank range.

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In the beginning: The German Panzerfaust (photo from Tankmaster).

ATGMs, Explosive Reactive Armor, and Duplex Weapons: Adapt or Die

While the hand-held SC weapons used by the infantry were the most effective at destroying armored vehicles (a shaped charge warhead will penetrate a thickness of steel equivalent to 150-250% of the warhead's diameter, which made the oversized infantry weapons more effective than cannon launched munitions), their limited range meant that they were a risk that armored formations could manage against - simply avoid built-up areas or limited-visibility terrain where rocket carrying infantry might hide. The introduction of the ATGM (Anti Tank Guided Missile) in the 1950s changed all that.

Carrying a large SC warhead, with a range that in many cases was greater than most tank guns, the ATGM finally gave the infantry the ability to reach out and destroy armored vehicles with impunity. This was not a risk that armor could mitigate; out-ranged and outgunned (you could not hang enough steel on a tank to prevent SC burn-through), the introduction of the ATGM all but signaled the extinction of the tank.

But in 1967, the German research scientist Manfred Held, while in Israel conducting experiments on tanks destroyed during the Six-Day War, discovered that an explosive "counter blast" could greatly reduce the effectiveness of SC weapons; thus, Explosive Reactive Armor (ERA) was born.

ERA, essentially a layer of explosive material sandwiched between metal plates, defeats SC weapons by disrupting and prematurely dissipating the metal plasma jet. Attached as blocks to vulnerable sections of the vehicle, ERA is detonated when the jet from a SC penetrates the outer metal plate. The resulting explosion travels at the same velocity as the plasma jet, but in the opposite direction, disrupting the precise flow of the jet, dispersing its energy and greatly reducing its effectiveness.

Though effective, ERA had its limitations; tanks equipped with ERA posed a serious risk to accompanying infantry who could be killed or injured by the exploding blocks. In addition, ERA was ablative and effective only once, so multiple weapons, or weapons with multiple (duplex) warheads would still be able to destroy a tank by pre-detonating the ERA blocks in one location. Nonetheless, ERA, and the later development of Chobham composite armor in the 1970s, once again neutralized the infantry's advantage over armor on the battlefield.

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A modern version of the shaped charge warhead: the MGM-164A has a range of about 140 km (87 miles). (Lockheed Martin photo).



continued.....

thedrifter
07-09-04, 09:05 AM
Self Forging Fragments: Pint-Sized Penetrators

Once again, the issue became how infantry could penetrate the armor of contemporary main battle tanks. One solution was to develop a kinetic energy weapon that was small enough to be transportable, yet powerful enough to penetrate modern armor using only mechanical force. This concept eventually led to the development of Explosively Formed Penetrators (EFP), or Self Forging Fragments.

The principle behind the EFP is very similar to that of the shaped charge. In the EFP a conical metal plate (or lens) is deformed, under explosive pressure, but unlike the SC, which converts the lens into a metal vapor plasma, the EFP lens retains its solid state and is instead reshaped into an aerodynamically efficient penetrator moving at an extremely high velocity (5,000+ meters/second.) Although an EFP cannot penetrate as much armor as a conventional SC (owing to its larger and more physical mass), the EFP is relatively "cool" when compared to the plasma jet of a conventional SC, and is less likely to set off any ERA mounted on the target, and so is more difficult to counter. In addition, while vehicles can be modified to resist the effects of EFPs, they cannot typically be modified to defend against both threats (counter measures which work against EFP are ineffective against SC, and vice versa).

EFP weapons can be fabricated in a variety of sizes, from crew-served missiles (such as the American TOW IIB) capable of defeating a tank's frontal armor, to smaller cluster bomb like sub-munitions (such as the CBU-97 sensor fused weapon or the M93 Hornet sensored anti-tank mine), which are area attack weapons that shoot through a vehicle's top armor. Infantry are, once again, holding their own against tanks, but for how long?

EFP in Action: The XM303 Special Operations Forces Demolition Kit

As a prominent example of EFP put to use, check out the XM303 Special Operations Forces Demolition Kit (SOFDK), designed for the Army's Special Operations Forces. The object behind the creation of the kit was simple: give Soldiers the components needed to accomplish their missions safely, efficiently, and effectively, with less risk. The SOFDK allows soldiers to remotely acquire their targets at extended standoff distances using munitions that defeat targets using less explosives than conventional demolition operations.

The EFP warheads in this kit are set up on standard camera tripods, and aimed with a built-in Omega sight or with one sight from the soldiers' standard set of four interchangeable carbine sights. The warheads are primed with standard blasting caps or detonation cord, and when initiated, form the EFP or "Cannon Ball" that is explosively projected with high velocity at the target. The warheads can be used in all environments, and even in total darkness, when used in tandem with standard visible laser or infra-red (night vision goggle-compatible) laser sighting. The EFP warheads can defeat targets ranging from eight-inch thick reinforced concrete block walls to three-inch thick armor plate.

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The latest generation of portable EFP weaponry, the Kestrel missile ...

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... and its devastating results. The missile has dual mode laser and magnetic sensors to detect the target, and trigger detonation.


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One big hole: a 55-gallon drum after getting hit by an EFP (Photo from National Institute of Justice).


XM303 Kit: EFP Warhead Complement
EFP_ Type_ Standoff_ Target
Small _ 1ft.-50m >_ 1 in.RHA
Medium _ 2ft.-50m >_ 2 in. RHA
Large_ 10ft.-50ft. 8"-24"_ Concrete


Ellie