Rockets and Missiles Over Ukraine: The Changing Face of Battle

Chapter 1

Introduction to Warheads

The primary role of the missiles and rockets is to destroy enemy personnel and equipment, structures and fortifications, and perform special tasks. The working edge of them is a warhead (Figures 1-1, 1-2) which inflicts the most damaging effects on the target. Detailed descriptions and explanations of particular warhead types will be discussed in the corresponding chapters.

Damaging effect is defined as the ability of ammunition to damage a target provided that it is already close to it and all its elements have operated without failure. The effectiveness of the damaging effect of ammunition on the target and its combat effectiveness should not, therefore, be confused. Obviously, the combat effectiveness depends not only on the effectiveness of the ammunition near a target but also on the accuracy of ammunition delivery, the reliability of all its elements (the fuze in particular), the ability to withstand the enemy’s defensive actions, and many other factors.

All ammunition is divided into the following types, depending on its main effects:1

•Fragmentation (with natural, controlled fragmentation, and preformed fragments; rod warheads; gunpowder and explosive shrapnel; case-shot),

•Penetrating (small-arms ammunition, armor-piercing, and concrete-piercing),

•Shaped charges (with single or tandem shaped charges; explosion-formed projectiles),

•High-explosive (blast) ammunition, including volumetric explosion ammunition (aerosol, thermobaric),

•Incendiary,

•Nuclear (based on fission or fusion),

•Unified by type of action.

Ammunition that does not damage targets but serves as a countermeasure to protect or reduce the damage from the enemy’s ammunition can be identified as a separate group. For the same purpose, active protection of armored vehicles is developed to destroy enemy ammunition as it approaches the target.

There are also many auxiliary and special-purpose munitions: lighting, smoke, and others that will not be considered here as well as the nuclear one.

To ensure a damaging effect on targets, it is necessary to exert any action on them. It is usual to highlight the following:

•Action of fragment flow,

•Penetrating action,

•Shaped charge action,

•Action of a shock wave and explosion products,

•Incendiary action,

•Action of penetrating, and

•Electromagnetic radiation of a nuclear explosion.

Despite the large variety of rockets and missiles designs, there are just a few ways for ammunition to act on targets. For the most part, all of them are determined either by the kinetic energy of the munition itself or by the chemical energy of the explosive that the munition is equipped with.

Missile and Rocket Explosion Effects

Modern versions of artillery guns and mortars are capable of a relatively high level of accuracy in an indirect fire role within their effective ranges. MLRS projectiles are generally spread over a sizable area which increases as the distance to the target increases. This limits their technical suitability for use against smaller or moving targets, especially in populated areas. Most indirect fire weapon systems used in today’s conflicts are incapable of achieving the high degree of accuracy required to hit a small point target with the first round, excluding the guided projectiles.2

Unguided artillery rockets fired from MLRS are neither accurate nor precise to some degree.

The main effects of high-explosive munitions comprise blast, heat and fragmentation originating from the munition, plus the secondary fragmentation and debris generated in the impact, or explosion of the munition, travelling at high velocity to considerable distance (see the next section for the technical description). These effects are compounded by firing a salvo of munitions simultaneously or sequentially and by their use in populated areas, which often results in large areas experiencing significant damage, as opposed to damage to a cluster of unconnected and localized points.

High-explosive munitions can cause a lot of damage to military objects, including the full destruction of the targeted object or area. In Ukraine, there are many urban areas used for military purposes such as factories and warehouses converted to ammunition depots and storage facilities. Many residential buildings such as schools, houses and buildings are used for military purposes. Explosives delivered either by unguided or guided munitions within populated areas are influenced substantially by the presence of built structures and geographical features. Structures may provide protection from primary and secondary explosive weapon effects, but also amplify these effects due to the channelling and reflection of blast waves. Buildings and vehicles may contribute bricks, concrete, glass, and other debris to the fragmentation originating from the weapon. Any fuel sources (liquid and gas) or toxic chemicals within the munition’s impact zone may pose a further hazard to humans, as does the compromised structural stability of buildings which may be prone to collapse.3

Figure 1-1: Warhead types: High Explosive – HE (top); High Explosive Fragmentation – HE FRAG (middle); cluster munition (bottom). (Source: A.P. Orlov, Osnovi ustroistva i finkcionirovania snaryadov RSZO, modified by author)

Figure 1-2: Shaped Charge (cumulative). (Source: A.P. Orlov, Osnovi ustroistva i finkcionirovania snaryadov RSZO, modified by author)

The intuitive reflex among those targeted (both military and civilians) to seek shelter from an explosive-weapon attack in buildings, vehicles, and similar enclosed spaces poses a lethal risk. The intensification of the weapon effects in a populated area is mainly due to the reflecting blast waves and presence of a number of people and structures within the amplified effective range of a munition(s), as well as sources of secondary fragmentation. This results in a higher proportion of fatalities than would be likely in open spaces.4

Humans are particularly vulnerable to blast overpressure and reflected blast waves. Surviving an explosive-weapon attack with only surface bruises visible does not exclude ruptured eardrums, damaged lungs, internal bleeding, brain damage, infections and poisoning, and bone fracturing. Depending on the layout of structures in a populated area and the type of explosive weapon used in an attack, the probability of survival for a human may indeed increase when away from the proximity of structures (prone on the ground in a small depression or narrow ditch).

Mortar and artillery systems continue to be walked on to the target using the method of observing the impact location and thereafter correcting the aim. The first projectiles often impact areas outside the intended target. To maximize accuracy and precision during such procedures, extensive training, frequent weapon testing, access to modern technologies, and detailed intelligence are paramount, supported by robust targeting policies and comprehensive and competent collateral damage estimates.

Explosion Effects on Targets

The impact of explosive munitions can be broken down into the principal damage mechanisms and their primary effects, and the secondary and tertiary effects occasioned by these. This section focuses on the primary damage mechanisms and secondary effects of explosives.5

The primary effects of explosive weapons are defined as those caused directly by the destructive effects that radiate from a point of initiation and include blast overpressure, fragmentation, heat and light. These are attributed directly to the principal damage mechanism of an explosive weapon – blast, fragmentation, and heat. The term blast refers to a high-pressure blast wave moving at supersonic speed, referred to as the shock wave, which is followed by blast winds. Primary fragmentation comprises fragments that originate directly from the explosive munition. The third damage mechanism is the thermal energy released during detonation of the explosive.

Most high-explosive warheads are not designed to deliver an augmented incendiary effect and the thermal effect is limited to the immediate area of the detonation, as well as by its extremely short duration. Generally, the primary thermal hazard posed by an explosive weapon is less significant than the blast and fragmentation threats. Secondary effects of explosive weapons derive from the environment in which the munition detonates. The most significant secondary effects include secondary fragmentation, firebrands, ground shock, and cratering.

Secondary fragmentation originates from objects that have been affected by the detonation and can include such objects as pieces of masonry or glass from structures, or bone fragments from human or animal targets. Secondary fragments are generally larger than primary fragments and tend not to travel as fast, or as far.

Ground shock results from the energy imparted to the ground by the shock wave caused by an explosion and can result from a detonation under or on the ground, or in the air above. Ground shock poses an additional threat to the structural integrity of buildings (which has significant effect in the urban areas), as the ground conducts the shock wave into the foundations and walls.

Cratering

Cratering refers to the buckling and deformation of the ground around the detonation point (Figure 1-3). Both ground shock and cratering can cause substantial damage to underground shelters and bunkers as well as critical infrastructure. This may be a deliberate effect of explosive munitions optimized for cratering, intended to obstruct avenues of approach or to disrupt infrastructure.6

Spalling presents an additional danger in urban environments. It is a stress-wave effect most commonly observed in materials more brittle than metal. This occurs when an impact strikes the outer surface of a solid body, causing fragments to break off from the inside surface. The projectile or the fragment does not need to penetrate the solid body; merely striking the outer surface with sufficient energy may result in spalling. A possible scenario resulting in spalling is a brick wall being struck by a blast wave, or in some cases a projectile or a sufficiently energetic fragment, causing secondary fragmentation inside the building. A significant hazard unique to urban environments is the risk of fatally compromised structural integrity of buildings caused by the blast waves. Any people in and around those buildings and structures may be crushed by their partial, or complete collapse.7

Figure 1-3: Typical crater from an explosion; d is the crater diameter, W is the crater width. (Source: G.F. Kinney and K.G. Graham, Explosives Shock in Air)

An impressive aspect of a surface explosion is its resulting crater (Figure 1-4). The great variability in crater formation is indicated by standard deviations of about one-third the diameter given by equation in Figure 1-3.

The depth of the crater created by an explosion ordinarily is about one-quarter its diameter, but this depends on the type of soil present (Figure 1-4). The diameter of the crater from an explosion also depends on the location of the explosion relative to surface level. Thus, explosions above a surface may not create any crater at all. For explosions below the surface, crater diameter initially increases with depth of explosion, reaches a maximum, then decreases substantially.8

Figure 1-4: Tochka-U crater near Makeevka (top); a pool-size crater in Slovyansk after impact (bottom). (Source: Author’s archive)

There is a comparatively good correlation between crater radius and sympathetic detonation distance (Figure 1-5), an observation that confirms the thought that sympathetic detonation is affected by the tangible physical means of missile or fragment impact (Figure 1-6).

Figure 1-5: During the explosion in the ground three characteristic zones are formed (top). (Source: S. Jaramaz, Physics of Explosion); Crater shapes as affected by burst geometries (bottom). (Source: Cratering by Explosion, Compendium)

Figure 1-6: Impact geometry. (Source: Cratering by Explosion, Compendium)

One of the interesting cratering phenomena often misinterpreted in the media is when photos show a missile tail sticking out of the ground. Often this is interpreted as an unexploded missile which is not true. These kinds of photos present the motor/propulsion section of the unguided or guided missile fired from the MLRS which at a certain point in the trajectory is separated from the rest of the missile but continues on the ballistic trajectory with the spin which stabilizes it on the path. Upon impact, almost under some angle, it can penetrate deeply into the ground. Taking into consideration the mass and the velocity of the tail section, these impacts can cause significant damage even if there is no explosion involved, but rather a sheer momentum of inertia (Figure 1-7).

Figure 1-7: Unusual even in a war, this Russian BM-30 rocket propulsion section impact was so high that it tore open the truck side and penetrated into the ground half length. (Source: avia.pro)

Blast Effects

An explosive is a material that is capable of producing an explosion by releasing the potential energy contained within it. All high explosives produce heat and gas. When a high-explosive charge detonates, it produces a blast wave (overpressure) that consists of two parts: a shock wave and a blast wind. The blast wave pushes outwards from the core of the detonation at supersonic speed. The outer edge of the blast wave is made up of the compressed gases contained in the surrounding air. This layer of compressed air is more properly described as a shock wave or shock front. In open air, the blast decays extremely quickly with time and distance; typically it can be measured in milliseconds.9

The blast wave has two phases (Figure 1-8). The positive-pressure phase pushes a large portion of the surrounding air away from the core of the detonation at supersonic speed, leaving a broad partial vacuum behind it. When the blast wave of the positive-pressure phase loses momentum, the partial vacuum behind it causes the compressed and displaced gases to reverse their movement and rush inward to fill the void. The negative-pressure phase moves less quickly than the positive phase and it generally lasts approximately three times as long.

Figure 1-8: Blast scaling law, named Hopkins-Cranz law. (Source: V. Karlos and G. Solomos, Calculation of Blast Loads for Application to Structural Components)

The effect of the pressure wave upon a structure depends on what the structure is composed of and how it is built. In essence, it is dependent upon the structure’s natural frequency of vibration compared with the duration of the blast wave. When the supersonic shock front from a detonation encounters a solid structure, some of the energy is reflected, and some of the energy is transmitted into the structure; the relative amounts depend on the properties of the structure.

Figure 1-9: Damage pattern due to the nearby explosion (top), Mariupol building (bottom).

In the process of striking the target, the shock front will impart significant momentum to the exterior components (Figure 1-9). These components will be pushed towards the interior by the positive-pressure wave, straining the resisting elements of the structure (such as support columns, building facades, etc.). Some of those resisting elements, windows in particular, will fail. As the negative-pressure phase of the pressure passes back through the structure, the direction of the energy is reversed. Unlike the reflection of sound waves, which have a negligible effect on the medium through which they are travelling, shock waves are moving at such high speed and contain so much energy that they change the medium itself. When the shock wave hits the ground, it is reflected back into the still-advancing blast wind. This amplifies the blast overpressure anywhere up to twenty times that of the initial detonation.10

Fragmentation

Primary fragmentation originates from the casing of the metallic shell surrounding the high-explosive charge. Fragments can take a variety of shapes and sizes, and are primarily effective in an anti-personnel capacity (Figures 1-10, 1-11).11

Figure 1-10: Schematic representation of the HE warhead detonation process. (Source: M. Lloyd, Conventional Warhead Systems, Physics and Engineering Design (Progress in Astronautics and Aeronautics), Vol. 179)

The type of steel used in the manufacture of the artillery shell plays a significant role in determining the nature of the natural fragmentation that is produced. High-explosive shells are typically made from either forged or cast steel or iron. Cast metals are melted down and poured into molds to form the shape of the projectile, whereas forged steel projectiles are formed by beating red-hot steel ingots into the desired shape. MLRS rockets have the thinner pre-formed shells or tight packed cubes to reduce the weight. The same is true of anti-aircraft missiles where the primary defeating elements are fragments.

Calculating the effects of primary fragmentation is more complicated than the blast effect, owing to the number of known unknowns. In many cases, the initial velocity (speed and impact angle) of the shell at the time of detonation is not known, nor is the exact shape, weight, and aerodynamic performance of each fragment. The type of fuze will also affect the fragmentation pattern. Due to the greater variation in the size and number of fragments caused by the explosion, natural fragmentation is more difficult to predict and model. The effect of fragmentation on human targets is particularly unpredictable, as the amount of exposed body area and the posture of the target can have a marked influence on the potential harm.12

The angle at which a munition impacts the target has a significant bearing on the size and shape of the lethal area. In simple terms, the higher the angle (toward vertical 90°) of fall, the larger the lethal area will be. In order to maximize lethal area, at higher angles of fall (45–90°) the optimal height for detonation is approximately 2m above ground, although even at just above ground, the lethal area is increased (Figure 1-11).13

Fragmentation is very important in surface-to-air missile warheads (Figures 1-12 top, 1-13). One of the variants of the fragmentation warhead is the one which uses rods (Figure 1-12 bottom). These types of warheads are in use in some anti-aircraft missiles.

Figure 1-11: Warhead fragments distribution: a) angle impact; b) vertical impact; c) vertical impact with distance activation (top and middle). (Source: A.P. Orlov, Osnovi Ustroistva i Funkcionirovaniya Snaryadov RSZO); formation of damaging sectors on the ground (bottom). (Source: I. Balagansky, Damaging Effects of Weapons and Ammunition)

Figure 1-12: SAM Fragmentation warhead explosion kinematic schematics with fragment velocity distribution (top); rod warhead action (bottom). Rods are made in the form of steel rods of square or round sections, laid on the surface of the explosive charge, as a rule, at a slight angle to its central axis. The rods can be firmly connected (welded) alternately with upper and lower ends. In this case, when throwing a system of rods, a continuous ring is formed. If the rods are not interconnected, then a field with many long fragments is formed. To prevent destruction during the explosion of the charge,