High Explosive Projectile, Fragmentation and Armor Piercing, Mine, Explosion Principle and Damage Zone, What Ammunition Power and Shock Wave

People who follow the news feed quite often hear words such as landmine, high-explosive or high-explosive fragmentation mine in the description of emergency events and incidents. Today, in the era of the heyday of the terrorist threat, not only adults, but also children know what a landmine is. A high-explosive mine has become a favorite weapon of terrorists, with which they can keep the population of cities in fear, inflicting painful blows on social infrastructure. Although literally some 20 years ago such terminology was the lot of the military and in most cases we only heard about landmines in reports from military conflict zones.

The simplest land mine

Despite the fact that combat tactics have undergone significant changes, landmines continue to be used as a means of deterring enemy advances. Artillery of all calibers massively use fragmentation ammunition. Armor-piercing high-explosive ammunition continues to be used to equip tank units and anti-tank forces.

The ability to inflict enormous destruction and cause significant casualties in a matter of seconds makes the landmine the main fire weapon.

Damaging effect

High-explosive ammunition acts with the destructive force of the gases of the explosive charge and partly with the force of impact on the barrier.
In accordance with this, the power of a high-explosive projectile is determined by the weight and quality of the explosive contained in its shell, which determines the main requirement for such projectiles. Increasing the power of high-explosive projectiles within the same caliber is possible by increasing the capacity of the chamber for the explosive charge and using a more powerful explosive. The volume of the projectile chamber can be increased by lengthening the cylindrical part of the projectile and reducing the thickness of its walls. However, the length of the cylindrical part is limited by the total length of the projectile, due to its stability along the trajectory. However, the long cylindrical part is a characteristic feature of high explosive projectiles. Reducing the wall thickness of a high-explosive projectile shell is limited by the requirement of its strength when fired. In this regard, the use of high-explosive shells in mortars and howitzers is more advantageous than in cannons, due to the high pressures developing in the latter when fired.

Design features of high-explosive ammunition

The high-explosive action of projectiles requires a delay in the operation of the fuse, so all explosive compounds used for high-explosive projectiles must be insensitive to shock. This fully applies to ordinary projectiles, since otherwise they will simply explode in the cannon channel.

Ammunition has a limited shelf life. At the same time, they use very stable chemical explosive compounds hidden in a sealed housing. The shelf life according to the standards is deliberately underestimated several times. This is done for reliability, since an expired projectile becomes more sensitive to impacts, and the likelihood of it exploding in the gun channel increases. Theoretically, firing expired shells is possible, but they must be handled very carefully, and there should be no people in the affected area when firing.

Chemistry and physics of explosion

But still, the main destructive force of a high-explosive fragmentation grenade is the high explosive contained in it. After the delay set by the setting has been worked out, the fuse is triggered and a detonation wave runs through the explosive material at a speed of about 6.7-7 km/s - from a physico-chemical point of view, a combination of a “ordinary” supersonic shock wave and the front of an exothermic chemical reaction initiated by it. At its core, the trinitrotoluene molecule is a metastable formation with three NO2 nitro groups already present in its composition, which accumulate a significant amount of energy and are capable of releasing active oxygen in redox reactions. The chemical reaction that occurs during the detonation of trinitrotoluene can be written as:

2 C7H5N3O6 → 3 N2 + 5 H2O + 7 CO + 7 C

As can be seen from the formula, its gaseous products include nitrogen, water and carbon monoxide. The low oxygen content in the trinitrotoluene molecule leads to insufficient oxidation of carbon (hence the presence of carbon monoxide and soot), so ammotol, a mixture of trinitrotoluene with sodium nitrate HNO3 (sodium nitrate), is very often used in high-explosive fragmentation shells (OF-350 is no exception). Additional oxygen allows carbon to be completely oxidized and more gaseous reaction products are obtained. But even without this, trinitrotoluene is a powerful explosive. Let us make some quantitative estimates in relation to our case. 6 kg of trinitrotoluene with a density of 1.6 g/cm³ occupy a volume of 3750 cm³ (this is the volume of a cube with a side of 15.3 cm - very close to the OF-530 caliber, although in reality its chamber is bottle-shaped, but without a neck, axisymmetric form). The molar mass of trinitrotoluene is 0.227 kg/mol, so the amount of trinitrotoluene in the chamber is 26.4 mol. Now let's use the chemical formula of the reaction and see that every two moles of trinitrotoluene after detonation gives 3 moles of nitrogen, 5 moles of water vapor and 7 moles of carbon monoxide. As is known from chemistry, each mole of gas under normal conditions occupies a volume of 22.4 liters. As a result, 6 kg of trinitrotoluene generates 39.6 moles of nitrogen, 66 moles of water vapor and 92.4 moles of carbon monoxide, which together will occupy 4435 liters of volume under normal conditions. 1 liter is equal to 1 cubic decimeter, i.e. 1000 cm³. Let's see how much our theoretical estimate deviated from the experimental data - it is known that 1 kg of trinitrotoluene generates 975 liters of resulting gases under normal conditions, i.e. 6 kg will give 5850 liters. The estimate turned out to have an error of about 20-25% due to the conventions adopted in the chemical reaction formula. It is known that the process of autoxidation of trinitrotoluene is more complex; its output products also contain gaseous nitrogen oxides and hydrocarbons. But in the end, the gases formed after detonation turned out to be compressed in a volume that was 1560 times less than required, and even heated to a temperature of about 3700 ° C. Using the equation of the state of an ideal gas known from physics:

p1 × V1 / T1 = p2 × V2 / T2

you can calculate their pressure on the walls of the grenade: p1 = 100 kPa, V1 = 5850 l, T1 = 288 K (15°C), V2 = 3.75 l, T2 = 3700 K. As a result, p2 ≈ 2004000 kPa ≈ 20 thousand. atm. And since highly compressed gas is far from ideal, relative to the real situation the estimate turned out to be an order of magnitude underestimated: experience gives the pressure upon rupture of a trinitrotoluene charge, a pressure 10 times greater - 200 thousand atm. The grenade body cannot withstand such pressure, the ammunition ceases to exist as a single body and represents fragments of the body and a dense clot of hot gases, which tends to expand in its volume and come to thermodynamic equilibrium with the environment.

Design

High-explosive projectiles have the thinnest shells, a high filling factor, a high relative mass of the explosive charge and a low relative mass of the projectile.

According to their design, high-explosive shells of medium caliber ground artillery are solid-body, with a screw head or a screw bottom and a point for a head fuse, and shells of large calibers are with a solid head, a screw bottom and a point for a bottom fuse, or with a screw head and a screw bottom and point. under the head fuse. Large-caliber shells, in addition, can have two points: under the head and bottom fuses; The use of two fuses ensures trouble-free operation and complete explosion of the projectile.

Small-caliber high-explosive shells in aviation artillery were first used by the Germans in 20- and 30-mm aircraft guns during World War II. The body of the 20-mm projectile is thin-walled, stamped, with grooves pressed into it for the leading belt and core punching of the cartridge case. To increase strength when fired, the bottom of the body is made of a hemispherical shape. There are no centering bulges on the body, and the centering of the projectile in the barrel bore is carried out by the centering bulge on the fuse and the leading belt. The fuse is connected to the projectile using an adapter sleeve fixed in the body.

The required strength of such projectiles when fired was achieved through the use of a metal body with high mechanical properties [ source not specified 1036 days

] and its heat treatment.

The appearance of high-explosive shells in small-caliber aviation artillery in the 1940s is explained by the increased damaging effect of these shells compared to fragmentation shells due to the low sensitivity of modern aircraft to damage from fragments [ source not specified 1036 days

].
Therefore, it should be considered appropriate[ when?
] every possible increase in the high explosiveness of small-caliber fragmentation shells of anti-aircraft and aviation artillery.
The use of high-explosive shells in ground artillery is advisable only in guns with a caliber of 120 mm and above, since the insignificant weight of the explosive charge of shells of a smaller caliber does not ensure the destruction of even the lightest field shelters [ source not specified 1036 days
].

Types of fragmentation submunitions

Metal is used as fragmentation damaging elements in ammunition. The cheapest option for large caliber artillery uses cast iron and steel. The so-called jacket and body of the projectile are simultaneously torn apart by the action of explosives and turned into fragments. Hand fragmentation grenades use aluminum. The low weight of the ammunition is important there. Specialized anti-personnel projectiles have steel balls. Finally, the most exotic and expensive option is tungsten balls, steel darts and other striking elements. This design is used in anti-aircraft missiles, as well as in specialized projectiles to destroy radar stations.

A few words about shrapnel

When a standard high-explosive fragmentation projectile ruptures, it is difficult to ensure an even distribution of fragments. To solve this problem, British soldier Henry Shrapnel invented a special type of this ammunition, which was later named after him. This type of high-explosive fragmentation projectile is additionally equipped with a ready-made set of striking elements and compounds. Shrapnel is most effective at low altitudes. In modern versions, the striking element is given the shape of a feathered pyramid. In this form, shrapnel successfully hits even targets that are protected by light armor.

Fuse

For a long time, the only fuse used was the impact fuse, which was triggered when the projectile hit the target.

Impact fuses are the simplest and most reliable. Most fuses of this type can be set to contact or delayed mode. In the first case, the explosion occurs upon first contact with an obstacle and is intended to destroy objects around the obstacle. In the second case, the projectile is buried into the target and only there detonation occurs - this makes it possible to effectively destroy fortifications and buildings.

However, this type of fuses has a significant drawback - when falling into a viscous environment, a projectile may either not explode at all (which is associated with a large number of unexploded shells at the sites of former military operations), or explode too late, with a significant depth into the environment - a damaging effect in this case is approaching zero.

A significant step forward was the development of remote fuses. These fuses detonate ammunition at a certain distance from the gun, thereby providing fundamentally new possibilities for using OFS. The most significant are the capabilities of destroying helicopters from tank guns, the ability to fire over long ranges along very steep trajectories, as well as the ability to destroy concentrations of enemy personnel in open areas.

Russian T-80UK and T-90 tanks are equipped with the Ainet system, which ensures the detonation of the OFS at a given point in the trajectory. The fuse is installed automatically; the gunner only needs to measure the range with a laser rangefinder. Practice shows that the consumption of shells for each target is reduced by approximately half.

Features of a fragmentation projectile

This type of ammunition is intended primarily to destroy living targets. It is used in guns whose calibers are small or medium. A fragmentation projectile may have a ready-made additional destructive element. It usually uses cubes, balls, needles and other objects that cause additional damage to the enemy. This type of projectile is most often used specifically to destroy manpower. The main requirement for such ammunition is the effectiveness of the destructive power of the fragments contained in them. In addition to their number, the range over which they can fly apart during an explosion is also taken into account. This type of projectile is significantly inferior to a high-explosive projectile in terms of filling coefficient and the size of the explosive charge.

Mixed Ammo Types

Today, the number of ammunition that only uses a land mine is used to load it has significantly decreased. A mixed-type projectile has much higher damaging characteristics and better efficiency. Thanks to this, such ammunition is widespread. When talking about what a land mine is, it should be borne in mind that there are several types of projectiles that use this type of charge to create them. Some of them are mixed. These, for example, include high-explosive fragmentation and armor-piercing high-explosive.

The first ones are the most universal and frequently used. They have high-explosive, fragmentation and delayed action types. The advantages of such shells include their relatively low cost. They are often used in the active army when organizing military exercises. However, due to their versatility, such ammunition is significantly inferior in destructive power to shells that are designed for only one type of target destruction. As for armor-piercing high-explosive shells, their purpose is to defeat various fortifications and armored vehicles. They became widespread in Great Britain, where they were invented. Currently, interest in them has noticeably decreased due to their low destructive power.

High explosive fuses

The first fuse for high-explosive fragmentation ammunition was an ordinary fuse, which was ignited when fired from a cannon and initiated the detonation of explosives after a certain time. However, after the advent of rifled guns and conical-shaped projectiles, which guaranteed that the front part of the hull would encounter an obstacle, impact fuses appeared. Their advantage was that the explosive exploded immediately after contact with the obstacle. For destruction, the impact fuses were equipped with a moderator. This allowed the ammunition to first penetrate the obstacle, thereby dramatically increasing its effectiveness. By equipping a landmine with such a fuse with a more massive body with thick walls (which made it possible, due to kinetic energy, to penetrate deep into the walls of long-term firing points), we obtained a concrete-piercing projectile.

By the way, at the initial stage of the Great Patriotic War, they successfully fought German armored vehicles with the help of 152-mm concrete-piercing shells. When a shell hit a medium or light German tank, due to its weight, it first destroyed the vehicle, tore off the turret, and then exploded. The disadvantage of impact fuses was that when they hit viscous soil (for example, a swamp), they did not work. This problem was eliminated by a remote fuse, which allows the ammunition to be detonated at a certain distance from the muzzle of the gun barrel. Currently, this type of detonator is used in almost all OFS. It allows, for example, firing tank guns at air targets (helicopters).

Promising developments

The theoretical limit has long been reached in the field of explosive compounds, so the efforts of developers are aimed at other aspects. There are two main directions. This is the development of guided projectiles and the improvement of fuses. Of the guided missiles, the Russian military-industrial complex currently produces only one variant - the Krasnopol projectile. This model performed very well in testing. Now its production volume amounts to tens of thousands of copies. All other technologically advanced armies in the world have their own designs of guided high-explosive projectiles.

Improvement of fuses is aimed at regulating the depth of detonation. If there is an explosion at the first contact with the surface, then this is not a high-explosive projectile. Excessive deepening is also undesirable. For example, when conducting combat operations in cities, this leads to shells exploding in the basements of buildings or being buried too far into the ground. All these shortcomings can be eliminated either by making an adjustable fuse or by using remote control.

A classic example of a variable fuze is anti-submarine grenades, bombs and shells. Before firing, they manually set the depth of the explosion depending on the depth of the detected target. Since the speed of a projectile in water depends little on the distance of the shot, this method is quite accurate. Adjustable fuzes have a built-in delay system on simple mechanisms, such as a hand grenade.

A projectile with a radio detonation will explode where a regular one will fly past. The radio detonation system has been developed for anti-aircraft shells since World War II.

Remote controlled fuses use a radio channel. The “Ainet” system can be considered an exemplary weapon of this class. Such a projectile can hit targets that are invulnerable to conventional projectiles. In combat conditions, the most dangerous are crews camouflaged on the ground with ATGMs, for example, Javelin. They need to be detected and defeated as quickly as possible. With the Ainet system this is done with one shot from the main tank gun.

Design and principle of operation

The device of an armor-piercing high-explosive projectile

In its design, an armor-piercing high-explosive projectile is generally similar to a conventional high-explosive projectile, but unlike the latter, it has a body with relatively thin walls, designed for plastic deformation when encountering an obstacle, and always only a bottom fuse. The charge of an armor-piercing high-explosive projectile consists of a plastic explosive and when the projectile meets an obstacle, it “spreads” over the surface of the latter. Contrary to popular myth, increasing the armor angle negatively affects the penetration and armor penetration of high-explosive armor-piercing shells, which can be seen, for example, in documents on testing the British 120mm L11 gun.

After the charge “spreads,” it is detonated by a delayed-action bottom fuse, creating a pressure of explosion products of up to several tens of tons per square centimeter of armor, dropping to atmospheric pressure within 1-2 microseconds. As a result, a compression wave with a flat front and a propagation speed of about 5000 m/s is formed in the armor; when it meets the rear surface of the armor, it is reflected and returns as a tension wave. As a result of wave interference, the rear surface of the armor is destroyed and spalls are formed that can damage the internal equipment of the vehicle or crew members. In some cases, through penetration of the armor may occur in the form of a puncture, break or knocked out plug, but in most cases it is absent. In addition to this direct effect, the explosion of an armor-piercing high-explosive projectile creates a shock impulse that acts on the tank's armor and can disable or tear off internal equipment, or injure crew members.

The effectiveness of armor targets, in American documents, is estimated as up to 1.3 of the caliber.

Chips on the inside of the armor from exposure to armor-piercing high-explosive shells

Due to its operating principle, an armor-piercing high-explosive projectile is effective against homogeneous armor and, like cumulative projectiles, its action depends little on the speed of the projectile and, accordingly, the firing distance. At the same time, the action of an armor-piercing high-explosive projectile is ineffective against combined armor, which poorly transmits the explosion wave between its layers, and is practically ineffective against spaced armor. Even against conventional homogeneous armor, the effectiveness of the armor-piercing high-explosive projectile can be significantly reduced or even negated by installing anti-fragmentation lining on the inside of the armor.

Two more disadvantages of the armor-piercing high-explosive projectile arise from its design features. The thin-walled body of the projectile forces it to limit its initial velocity compared to other types of ammunition, including cumulative ones, to less than 800 m/s. This leads to a decrease in trajectory flatness and an increase in flight time, which sharply reduces the chances of hitting moving armored targets at real combat distances. The second disadvantage is due to the fact that an armor-piercing high-explosive projectile, despite the significant mass of the explosive charge, has a relatively small fragmentation rate, since its body has thin walls, and its mechanical properties are designed primarily for deformation, and not for the effective formation of fragments, as in specialized high-explosive fragmentation or multi-purpose cumulative projectiles. Accordingly, the effect of the shells against enemy manpower is insufficient, which is considered a serious drawback of armor-piercing cumulative shells, since with the refusal of the overwhelming majority of Western tanks from high-explosive fragmentation shells, the role of the latter in the fight against manpower falls on cumulative or armor-piercing high-explosive shells shells.

Another cumulative myth

At the dawn of the practical use of cumulative ammunition, during the Second World War, they were quite officially called “armor-burning”, since in those days the physics of the cumulative effect was unclear. And although in the post-war period it was precisely established that the cumulative effect has nothing to do with “burning through”, echoes of this myth are still found in the philistine environment. But in general, we can assume that the “armor-burning myth” has safely died. However, “a holy place is never empty” and one myth regarding cumulative ammunition was immediately replaced by another...

This time, the production of fantasies about the effects of cumulative ammunition on the crews of armored vehicles was put on stream. The main postulates of the dreamers are as follows: • tank crews are supposedly killed by excess pressure created inside an armored vehicle by cumulative ammunition after breaking through the armor; • Crews who keep the hatches open are supposedly kept alive due to the "free exit" for excess pressure. Here are examples of such statements from various forums, websites of “experts” and printed publications (the original spelling has been preserved; among those cited there are very authoritative printed publications):

“- Question for experts. When a tank is hit by cumulative ammunition, what damaging factors affect the crew? - Excessive pressure first. All other factors are related”;

“Assuming that the cumulative jet itself and fragments of pierced armor rarely affect more than one crew member, I would say that the main damaging factor was the overpressure... caused by the cumulative jet...”;

“It should also be noted that the high destructive power of shaped charges is explained by the fact that when a jet burns through the hull, tank or other vehicle, the jet rushes inside, where it fills the entire space (for example, in a tank) and causes severe damage to people...”; “The tank commander, Sergeant V. Rusnak, recalled: “It’s very scary when a cumulative projectile hits a tank. “Burns through” armor anywhere. If the hatches in the turret are open, then a huge pressure force throws people out of the tank..."

“...the smaller volume of our tanks does not allow us to reduce the impact of INCREASED PRESSURE (the shock wave factor is not considered) on the crew, and it is the increase in pressure that kills them...”

“What is the calculation made for, because of which actual death should occur, if the drops did not kill, let’s say, the fire did not break out, and the pressure is excessive or it simply tears into pieces in a confined space, or the skull bursts from the inside. There's something tricky about this excess pressure. That’s why they kept the hatch open”;

“An open hatch sometimes saves the day because a blast wave can throw a tanker out through it. A cumulative jet can simply fly through a person’s body, firstly, and secondly, when in a very short time the pressure increases very much + everything around heats up, it is very unlikely to survive. From eyewitness accounts, the tank crews’ turret is torn, their eyes fly out of their sockets”;

“When an armored vehicle is hit by a cumulative grenade, the factors that affect the crew are excess pressure, armor fragments and a cumulative jet. But taking into account the measures taken by the crews to prevent the formation of excess pressure inside the vehicle, such as opening hatches and loopholes, armor fragments and a cumulative jet remain the factors affecting personnel.”

There are probably enough “horrors of war” presented by both citizens interested in military affairs and the military personnel themselves. Let's get down to business - refuting these misconceptions. First, let's consider whether it is in principle possible for the appearance of supposedly “lethal pressure” inside armored vehicles from the impact of cumulative ammunition. I apologize to knowledgeable readers for the theoretical part, they may miss it.

PHYSICS OF THE CUMULATIVE EFFECT

Rice. 1. Tandem cumulative ammunition of the German RPG “Panzerfaust” 3-IT600. 1 – tip; 2 – precharge; 3 – head fuse; 4 – telescopic rod; 5 – main charge with a focusing lens; 6 – bottom fuse.

Rice. 2. Pulsed X-ray image of shaped charge detonation. 1 – armored barrier; 2 – cumulative charge; 3 – cumulative recess (funnel) with metal lining; 4 – charge detonation products; 5 – pestle; 6 – head part of the jet; 7 – removal of barrier material.

The principle of operation of cumulative ammunition is based on the physical effect of accumulation (cumulation) of energy in converging detonation waves formed when an explosive charge having a funnel-shaped recess is detonated. As a result, a high-speed flow of explosion products—a cumulative jet—is formed in the direction of the excavation focus. An increase in the armor-piercing effect of a projectile in the presence of a notch in the bursting charge was noted back in the 19th century (Monroe effect, 1888)[2], and in 1914 the first patent for an armor-piercing cumulative projectile was received[3].

The metal lining of the recess in the explosive charge makes it possible to form a high-density cumulative jet from the lining material. The so-called pestle (the tail part of the cumulative jet) is formed from the outer layers of the cladding. The inner layers of the cladding form the head of the jet. A lining made of heavy ductile metals (for example, copper) forms a continuous cumulative jet with a density of 85-90% of the material density, capable of maintaining integrity at high elongation (up to 10 funnel diameters). The speed of the metal cumulative jet reaches 10-12 km/s at its head. In this case, the speed of movement of parts of the cumulative jet along the axis of symmetry is not the same and amounts to up to 2 km/s in the tail part (the so-called velocity gradient). Under the influence of the velocity gradient, the jet in free flight is stretched in the axial direction with a simultaneous decrease in the cross section. At a distance of more than 10-12 diameters of the shaped charge funnel, the jet begins to disintegrate into fragments and its penetrating effect sharply decreases.

Experiments on trapping a cumulative jet with a porous material without destroying it showed the absence of the recrystallization effect, i.e. the temperature of the metal does not reach the melting point, it is even below the point of first recrystallization. Thus, a cumulative jet is a metal in a liquid state, heated to relatively low temperatures. The temperature of the metal in the cumulative jet does not exceed 200-400° degrees (some experts estimate the upper limit at 600° [4]).

When meeting an obstacle (armor), the cumulative jet slows down and transfers pressure to the obstacle. The jet material spreads in the direction opposite to its velocity vector. At the boundary between the materials of the jet and the barrier, pressure arises, the magnitude of which (up to 12-15 t/sq.cm) is usually one or two orders of magnitude greater than the tensile strength of the barrier material. Therefore, the barrier material is removed (“washed out”) from the high pressure zone in the radial direction.

These processes at the macro level are described by hydrodynamic theory, in particular, the Bernoulli equation is valid for them, as well as that obtained by M.A. Lavrentiev. hydrodynamic equation for shaped charges[5]. At the same time, the calculated depth of penetration of an obstacle does not always agree with experimental data. Therefore, in recent decades, the physics of interaction between a cumulative jet and an obstacle has been studied at the submicro level, based on a comparison of the kinetic energy of impact with the energy of breaking interatomic and molecular bonds of a substance [6]. The results obtained are used in the development of new types of both cumulative ammunition and armored barriers.

The armor-protecting effect of cumulative ammunition is ensured by a high-speed cumulative jet that penetrates the barrier and secondary armor fragments. The jet temperature is sufficient to ignite powder charges, fuel vapors and hydraulic fluids. The damaging effect of the cumulative jet and the number of secondary fragments decrease with increasing armor thickness.

HIGH-EXPLOSIVE EFFECT OF CUMULATIVE AMMUNITION

Rice. 3. Inlet (A) and outlet (B) holes punched by a cumulative jet in a thick-armored barrier. Source: [4]

Now let's talk more about excess pressure and shock waves. The cumulative jet itself does not create any significant shock wave due to its small mass. The shock wave is created by the detonation of an explosive charge of ammunition (high-explosive action). A shock wave CANNOT penetrate a thick-armored barrier through a hole pierced by a cumulative jet, because the diameter of such a hole is negligible and it is impossible to transmit any significant impulse through it. Accordingly, excess pressure cannot be created inside the armored object.

The gaseous products formed during the explosion of a shaped charge are under a pressure of 200-250 thousand atmospheres and heated to a temperature of 3500-4000°. Explosion products, expanding at a speed of 7-9 km/s, strike the environment, compressing both the environment and the objects in it. The layer of medium adjacent to the charge (for example, air) is instantly compressed. Trying to expand, this compressed layer intensively compresses the next layer, and so on. This process propagates through an elastic medium in the form of a so-called SHOCK WAVE.

The boundary separating the last compressed layer from the normal medium is called the shock wave front. At the front of the shock wave there is a sharp increase in pressure. At the initial moment of formation of the shock wave, the pressure at its front reaches 800-900 atmospheres. When the shock wave breaks away from the detonation products that lose their ability to expand, it continues to independently propagate through the medium. Typically, separation occurs at a distance of 10-12 reduced radii of the charge [7].

The high-explosive effect of the charge on a person is ensured by the pressure in the front of the shock wave and the specific impulse. The specific impulse is equal to the amount of motion carried by the shock wave per unit area of the wave front. During the short duration of the shock wave, the human body is affected by the pressure at its front and receives an impulse of movement, which leads to contusions, damage to the external integument, internal organs and skeleton[8].

The mechanism for the formation of a shock wave when an explosive charge is detonated on surfaces differs in that, in addition to the main shock wave, a shock wave reflected from the surface is formed, which is combined with the main one. In this case, the pressure in the combined shock wave front almost doubles in some cases. For example, during an explosion on a steel surface, the pressure at the front of the shock wave will be 1.8-1.9 compared to the detonation of the same charge in the air [9]. This is exactly the effect that occurs when shaped charges of anti-tank weapons detonate on the armor of tanks and other equipment.

Rice. 4. An example of the affected area by the high-explosive action of a cumulative ammunition with a reduced mass of 2 kg when it hits the center of the right side projection of the turret. The zone of lethal damage is shown in red, and the zone of traumatic damage in yellow. The calculation was carried out according to the generally accepted methodology [11] (without taking into account the effects of the shock wave flowing into the hatch openings)

Rice. 5. The interaction of the shock wave front with a dummy in a helmet during the detonation of a 1.5 kg C4 charge at a distance of three meters is shown. Areas with excess pressure over 3.5 atmospheres are marked in red. Source: NRL's Laboratory for Computational Physics and Fluid Dynamics

Due to the small dimensions of tanks and other armored vehicles, as well as the detonation of shaped charges on the surface of the armor, the high-explosive effect on the crew in the case of OPEN HATCHES of the vehicle is ensured by relatively small charges of shaped ammunition. For example, if it hits the center of the side projection of a tank turret, the path of the shock wave from the point of detonation to the hatch opening will be about a meter; if it hits the front part of the turret, it will be less than 2 m, and if it hits the rear part, it will be less than a meter. If a cumulative jet hits the dynamic protection elements, secondary detonation and shock waves arise, which can cause additional damage to the crew through the openings of open hatches.

Rice. 6. The damaging effect of the "Panzerfaust" 3-IT600 RPG cumulative ammunition in a multi-purpose version when firing at buildings (structures). Source: Dynamit Nobel GmbH

Rice. 7. M113 armored personnel carrier, destroyed by a Hellfire ATGM hit

The pressure at the shock wave front at local points can either decrease or increase when interacting with various objects. The interaction of a shock wave even with small objects, for example with the head of a person in a helmet, leads to multiple local changes in pressure [12]. Typically, this phenomenon is observed when there is an obstacle in the path of the shock wave and penetration (as they say, “flowing”) of the shock wave into objects through open openings.

Thus, the theory does not confirm the hypothesis about the destructive effect of excess pressure of cumulative ammunition inside the tank. The shock wave of cumulative ammunition is formed when an explosive charge explodes and can penetrate inside the tank only through hatch openings. Therefore, hatches SHOULD BE KEEPED CLOSED. Those who do not do this risk receiving a severe concussion, or even dying from a high-explosive action when a shaped charge is detonated.

Under what circumstances is a dangerous increase in pressure inside closed objects possible? Only in those cases when the cumulative and high-explosive action of an explosive charge makes a hole in the barrier sufficient for the explosion products to flow in and create a shock wave inside. The synergistic effect is achieved by a combination of a cumulative jet and the high-explosive action of a charge on thin-armored and fragile barriers, which leads to structural destruction of the material, ensuring the flow of explosion products behind the barrier. For example, the ammunition of the German Panzerfaust 3-IT600 grenade launcher in a multi-purpose version, when breaking through a reinforced concrete wall, creates an excess pressure of 2-3 bar in the room.

Heavy ATGMs (type 9M120, Hellfire) when hitting a light-class armored fighting vehicle with bulletproof protection, with their synergistic effect, can destroy not only the crew, but also partially or completely destroy the vehicles. On the other hand, the impact of most wearable PTS on armored fighting vehicles is not so sad - here the usual effect of the armor effect of a cumulative jet is observed, and the crew is not damaged by excess pressure.

PRACTICE

Rice. 8. Three hits from cumulative RPG shots in an infantry fighting vehicle. Despite the dense grouping of holes, no breaches are observed. Source: [13]

We had to fire a cumulative projectile from 115-mm and 125-mm tank guns, and a cumulative grenade from an RPG-7 at various targets, including a stone-concrete bunker, an ISU-152 self-propelled gun and an armored personnel carrier BTR-152. An old armored personnel carrier, full of holes like a sieve, was destroyed by the high-explosive effect of the projectile; in other cases, no allegedly “crushing effect of the shock wave” was detected inside the targets. Several times I examined damaged tanks and infantry fighting vehicles, mostly damaged by RPGs and LNG. If there is no explosion of fuel or ammunition, the impact of the shock wave is also imperceptible. In addition, no concussion was noted among the surviving crews whose vehicles were damaged by RPGs. There were wounds from shrapnel, deep burns from metal splashes, but there were no concussions from excess pressure.

Numerous evidence and facts during the campaigns in the Chechen Republic about the destruction of tanks, armored personnel carriers and infantry fighting vehicles by cumulative RPG and ATGM ammunition did not reveal the influence of excess pressure: all cases of death, injury and shell shock of crews are explained either by damage to the cumulative jet and fragments of armor, or by the high-explosive effect of cumulative ammunition[ 13].

There are official documents describing the nature of damage to tanks and crews by cumulative ammunition: “The T-72B1 tank ... was manufactured by the Uralvagonzavod Production Association (Nizhny Tagil) in December 1985. Participated in actions to restore constitutional order in the Chechen Republic in 1996 and received combat damage that led to the death of the tank commander... When examining the facility, specialists identified 8 combat damage. Of these: • on the hull – 5 damages (3 hits by a cumulative grenade in areas of the side protected by the remote sensing device, 1 hit by a cumulative grenade on the rubber-fabric screen not protected by the remote sensing device, 1 hit by a fragmentation grenade on the stern sheet); • on the turret – 3 damage (1 hit each from a cumulative grenade in the front, side and rear parts of the turret).

The tank was fired upon with cumulative grenades from hand grenade launchers of the RPG-7 type (armor penetration up to 650 mm) or RPG-26 “Mukha” (armor penetration up to 450 mm) and fragmentation grenades of the VOG-17M type from under-barrel grenade launchers or AGS-17 “Plamya”. Analysis of the nature of the lesions and their relative position with a fairly high degree of probability allows us to conclude that at the moment the shelling of the tank began, the turret and its gun were in the “stowed” position, the Utes anti-aircraft gun was turned back, and the commander’s hatch cover was slightly open or fully open. The latter could lead to the defeat of the tank commander by the products of the explosion of a cumulative grenade and explosive device when it hits the right side of the turret without penetrating the armor. After the damage received, the vehicle retained the ability to move under its own power... The vehicle body, chassis components, engine-transmission unit, ammunition and internal fuel tanks, and in general the body equipment remained operational. Despite the through penetration of the turret armor and some damage to the A3 and STV elements, there was no fire inside the vehicle, the ability to fire manually was retained, and the driver and gunner remained alive (emphasis added by the author)”[14].

EXPERIMENT

Rice. 9. The degree of danger of the damaging factors of cumulative ammunition

Finally, the last nail in the coffin of the myth under discussion. Irrefutable facts obtained experimentally.

The Defense Research Service of the Danish Armed Forces tested the effectiveness of cumulative submunitions for 155-mm projectiles, choosing the Centurion tank as the object. The Danes used a static testing technique, placing submunitions on the turret and body of the vehicle at different angles. Pressure, temperature, and acceleration sensors were placed inside the vehicle, in the crew seats in the crew compartment, and throughout the tank. During the research process, 32 submunition explosions were carried out on the tank. The power of cumulative ammunition was such that the cumulative jet often pierced the tank from top to bottom, and even left a crater in the ground under the bottom. At the same time, the sensors installed in the tank DID NOT RECORD AN INCREASE IN PRESSURE AND TEMPERATURE[15].

In 2008, at the 24th International Symposium on Ballistics, Dr. Manfred Held from the Defense and Security Systems department of the aerospace corporation EADS presented a report “Behind Armor Effects at Shaped Charge Attacks” [16]. The report summarizes the results of the latest experiments, using modern measuring instruments and techniques, to study the damaging factors of cumulative ammunition. There is no point in citing hundreds of figures obtained during experiments here. A general picture of the armor effect of cumulative ammunition, shown in the final figure from the report, is sufficient. The effect of excess pressure (Blast) that interests us is marked as INsignificant (according to the domestic classification - zero degree of damage, see Table 1). Which, in fact, was not subject to doubt in specialist circles. But the cumulative jet itself (Residual Jet Material) and fragments (Spalls) pose a serious danger. A medium degree of danger from the high-explosive action of ammunition on the outside of the armor was also noted, which once again emphasizes the harmfulness of the myth under discussion.

FINAL CONCLUSION

If the cumulative jet and fragments of armor do not hit people and fire/explosive equipment of the tank, then the crew will survive safely: provided they are inside the armored vehicles and the hatches are closed!

[1] See “Artillery Course, Book 5. Ammunition” // M.: Voenizdat, 1949, Pp. 37. [2] See “Reactive Armor,” Travis Hagan // Explosives Engineering MNGN 498; March 18, 2002. [3] HEAT ammunition received widespread practical use during the Second World War and in the post-war period, right up to the present day. [4] See “Domestic anti-tank grenade launcher systems”, Lovi A.A. and others // M.: “Eastern Horizon”. [5] See “Penetration of a cumulative jet into multilayer and cermet materials”, Pashkeev I.Yu. // Chelyabinsk, South Ural State University. [6] See “Metalphysical research and energy distribution”, Pond R., Glass K. In the book: High-speed impact phenomena // M.: Mir, 1973. [7] Reduced radius: the radius of a spherical charge whose mass is equal to the mass explosive charge. [8] Primary damage from high-explosive action affects almost all organs and parts of the human body: the brain and spinal cord, hearing organs, abdominal and thoracic cavities, and the vascular system. Hemorrhages in the frontal and paranasal sinuses and ruptured eardrums are often detected. Damage to the vascular system manifests itself in the form of dissection or rupture of the walls of blood vessels. (https://www.med-pravo.ru/SudMed/Dictionary/LetterVav.htm) [9] See “Fundamentals of explosives”, Epov B.A. // M.: Voenizdat, 1974. [10] Reduced explosive mass: the mass of an explosive when detonated in the air, creating pressure at the front of the shock wave of the explosion, similar to the detonation of a charge on a steel surface. [11] See “Unified Safety Rules for Blasting Operations”, PB 13-407-01 // M.: NPO OBT, 2002. [12] See “Blast-Induced Pressure Fields Beneath a Military Helmet for Non-Lethal Threats ", David Mott et al. // 61st Annual Meeting of the APS Division of Fluid Dynamics, 2008. [13] See "Tanks in the battles for Grozny. Part 1”, Vladislav Belogrud // “Front Illustration”, M.: “KM Strategy”, 2008. “Tanks in the battles for Grozny. Part 2”, Vladislav Belogrud // “Front Illustration”, M.: “KM Strategy”, 2008. [14] “Report on new developments of protective devices for armored vehicles”, military unit 68054, 1999. [15] https:/ /www.danskpanser.dk/Artikler/Destruerede_kampvogne_for_skud_igen.htm [16] https://www.netcomposites.com/netcommerce_features.asp?1682

Fuse

For a long time, the only fuse used was the impact fuse, which was triggered when the projectile hit the target.

In case of a direct hit in vulnerable areas (turret hatches, engine compartment radiator, ejection screens of the aft ammunition rack, etc.), the OFS can disable a modern tank. Also, the shock wave and fragments, with a high degree of probability, disable surveillance and communication devices, weapons placed outside the armor volume, and other systems installed in large quantities on modern armored vehicles.

People who follow the news feed quite often hear words such as land mine, high-explosive mine or high-explosive fragmentation mine in the description of emergency events and incidents. Today, in the era of the heyday of the terrorist threat, not only adults, but also children know what a landmine is. A high-explosive mine has become a favorite weapon of terrorists, with which they can keep the population of cities in fear, inflicting painful blows on social infrastructure. Although literally some 20 years ago such terminology was the lot of the military and in most cases we only heard about landmines in reports from military conflict zones.

What type of projectile should I use?

Basic rules when choosing between armor-piercing and high-explosive fragmentation shells:

Use armor-piercing shells against tanks of your level; high-explosive fragmentation shells against tanks with weak armor or self-propelled guns with open deckhouses.
Use armor-piercing shells in long-barreled and small-caliber guns; high-explosive fragmentation - in short-barreled and large-caliber. The use of small-caliber HE shells is pointless - they often do not penetrate, and therefore do not cause damage.
Use high-explosive fragmentation shells at any angle, do not fire armor-piercing shells at an acute angle to the enemy's armor.
Targeting vulnerable areas and shooting at right angles to the armor are also useful for HE - this increases the likelihood of breaking through the armor and taking full damage.
High-explosive fragmentation shells have a high chance of inflicting small but guaranteed damage even if they do not penetrate armor, so they can be effectively used to knock down a grapple from the base and finish off opponents with a small margin of safety.

For example, the 152mm M-10 gun on the KV-2 tank is large-caliber and short-barreled. The larger the caliber of the projectile, the greater the amount of explosive it contains and the more damage it causes. But due to the short length of the gun's barrel, the projectile is fired with a very low initial velocity, which leads to low penetration, accuracy and range. In such conditions, an armor-piercing projectile, which requires an accurate hit, becomes ineffective, and a high-explosive fragmentation one should be used.

Detailed review of shells

High explosive projectile. Operating principle

The main area of application of high-explosive ammunition is the destruction of buildings and structures, shelters and shelters for manpower. In field and combat conditions, these are, as a rule, trenches and dugouts, brick and wooden structures and structures. High-explosive artillery shells are most often used as a fire engineering tool used by large-caliber artillery systems. When a projectile hits a target, as a result of the detonation of explosives, a high-explosive effect on objects occurs. The power of the ammunition to impact objects is determined by the high explosiveness of the charge. High explosiveness characterizes the ability of an explosive to create a certain amount of explosion products in a short period of time that can have a destructive effect.

It should be taken into account that the high explosiveness of the charge may be different. The measure of high explosiveness of each ammunition depends on the potential of the explosive (HE) and the specific energy released by it at the moment of explosion. The performance of explosives used to fill ammunition may vary. The force and power of the explosion are influenced by the specific volume and composition of gaseous products resulting from the detonation of explosives. It is quite difficult to accurately determine the actual performance of a particular explosive, therefore the high explosiveness of a certain explosive charge is usually expressed in relative units. As a rule, the high-explosive effect of an explosive is compared with the result of the action of a certain amount of TNT. The specific volume of products resulting from the explosion is measured in TNT equivalent.

Based on these data, we can draw a conclusion. The power of a high explosive projectile is determined by the amount and type of explosive. An increase in the number of explosives leads to an increase in the caliber of ammunition. More powerful explosives make it possible to achieve the required destructive effect without increasing the caliber of the projectile. For example, for armor-piercing high-explosive anti-tank shells, the main thing is not the caliber, but a certain damaging effect. Due to their high penetrating power, such projectiles can penetrate deep into the armor, after which the high-explosive charge leads to its further destruction.

What is the difference between a high-explosive charge and a high-explosive projectile?

It should be said right away that an artillery shell, mine or aerial bomb is a munition device that may differ in the principle of impact, purpose and scope of application. However, all of the ammunition listed is based on one single principle - high-explosive action, i.e. striking effect. Both mines and shells can be high explosive. Any ammunition that contains an explosive substance is high explosive. This can be either a concrete-piercing or high-explosive fragmentation projectile or anti-tank ammunition with a combined effect.

Land mine in action

High explosive charge is an engineering term describing a certain amount of explosive used for detonation. The blast wave in this case is the main damaging effect. The secondary damaging factors in a landmine explosion are the explosion products. Detonation of explosives can be of direct or indirect action. As a rule, an electric discharge, chemical reaction, fire method, or mechanical action are used to activate a high-explosive charge. An electric spark and a fire cord are the main means of detonating a stationary high-explosive charge, while the impact mechanism and incendiary tube become detonators of directional ammunition. The explosive, enclosed in a casing or container, is an already defined type of ammunition, ready for use. The high-explosive projectile and aerial bomb are the main ammunition of artillery systems and aviation, the mine is the main fire engineering and technical means.