Fragmentation field of an anti-aircraft guided missile BUK

The fragmentation field produced by a missile assembly detonation has a number of features, the main ones being a significant increase in the number of fragments and an increase in their meridional angle of dispersion. Even if the warhead alone is detonated (without the missile bodies), in addition to the prefabricated projectiles, the field of effect is also formed by the detonation products. The 9H314M warhead weighs about 70 kilograms. If one subtracts the mass of prefabricated projectiles (~28.7 kg) and explosive charge (~33.5 kg) from the total mass of the warhead, then several kg would remain (cap, bottom, cap and other warhead shell elements) that create additional factors and have a noticeable impact on the engagement field. An even greater impact is caused by the missile's compartments close to the warhead. As an example (Figure 5.2.3), an exterior view of a fragment of a target layout (witness sheet) containing three types of penetrations: prefabricated projectiles (PEAs), hull projectiles (fragments of compartment bodies which may not have the same dimensions as the PEAs) and detonation products (1-3 mm holes) are shown.

Figure 5.2.3 - General view of fragment 2.1 of target No. 2

All types of through-hole are clearly visible in the close-up view of this fragment shown in Figure 5.2.4.

Figure 5.2.4 - Close-up of Fragment 2.1 of Target No. 2. Entry holes vary in configuration from an elongated compact shape to a distinctive "butterfly" shaped hole for off-the-shelf projectiles and hull fragments, and small holes (1-3 mm) from detonation products.

A similar pattern of damage was obtained in the second experiment with the IL-86 target aircraft, where a missile assembly was detonated. Figure 5.2.5 shows a photograph of a fragment of the target aircraft ("FR 2") with all three types of penetrations, including the distinctive butterfly-shaped penetration. The damage characteristics of the 9H314M type 1-10 (I-beam, Bow-tie) are described in more detail in subsection 6.1 and paragraph 6.2.2 of Field Experiment Report (2016).

Figure 5.2.5 - Close-up of fragment "FR 2" of target GB-86

Schematic representation of the fragmentation field in the meridional of the plane after the detonation of an assembled missile is depicted at figure 5.2.6.

Figure 5.2.6 - Static fragmentation field in the meridional plane

That is, under static conditions, the fragments (prefabricated and hull-shaped projectiles) after detonation propagate in the meridional plane in virtually all directions, as confirmed by field experiments and tests conducted by the Corporation.

In doing so, a few of the most important parameters should be highlighted:
1. The position in space of the area of dense flow of the impacting elements (the area of maximum density of ready impacting elements, the so-called "scalpel") in which more than 42% of the mass of all fragments and more than 50% of the kinetic energy of the fragmentation field of destruction are concentrated. The presence of the "scalpel" and the results of its effects have been confirmed experimentally. The importance of determining the "scalpel" area is important because traces of its impact are one of the markers for determining the position of the missile relative to the aircraft at the time of detonation.
2. The positions in space of the trailing boundary of the debris field. The importance of defining it lies in the fact that the orientation of the trailing boundary of the debris field determines the forward boundary of the fragment cloud. Accordingly, the correct definition of the fragmentation trailing boundary affects the accuracy of determining the position of the missile relative to the aircraft at the moment of detonation.

Dynamic conditions

When firing at an airborne target, the warhead is detonated while the missile is in flight. The velocity vector of the missile is always tangential to its trajectory. The fragments of the warhead (preformed fragments + body) have a translational velocity equal to that of the missile VM. When the warhead is detonated, the translational velocity is geometrically added to the intrinsic velocity VSE, which is obtained by the fragment from the energy of the warhead. Since the velocity vector of the missile VM does not coincide with the longitudinal axis of the missile OX1, the values of the flyaway angles are not the same for different cross sections of the dynamic region. That is, under dynamic conditions, even when only the velocity of the missile is taken into account, the fragmentation field is not symmetric about the longitudinal axis of the missile. The asymmetry of the fragmentation field cross section is even more pronounced if the relative velocity of the projectiles, VPE.OTH:

where: - the relative velocity vector of the missile.

The nature of the fragment dispersion with respect to relative velocity (taking into account the velocities of the preformed fragments, missile and aircraft) is shown in Figure 5.2.9.

Figure 5.2.9 - Relative velocity of the impactor (out of scale)

As shown above, the fragmentation field under dynamic conditions is not symmetric about the missile's axis, so a spherical diagram of fragment dispersion obtained by extrapolation by rotation around the missile's longitudinal axis will have significant errors.

The rear front of the shattering field is the most affected. Figure 5.2.10 shows the simulation results fragmentation field for conditions within the range of DSB conditions: missile velocity VM = 600 m/s, angle between aircraft and missile axes AZwarhead = –30°.

Figure 5.2.10 - Unbalanced cross-section of the fragmentation field in the meridional plane under dynamic conditions

The software used by the Corporation's specialists takes all these features into account and calculates the trajectories of each of the fragments, taking into account the influence of velocity projections in the three planes. The results of the comparative modelling show that the asymmetry of the fragmentation field (left and right side relative to the longitudinal axis of the missile) depends primarily on the variation of angles between the missile and the aircraft and the final velocity of the missile: As the angle between the longitudinal axes of the aircraft and the AZwarhead missile increases at the moment of detonation, the value of the angle characterising the rear boundary of the fragmentation field increases (up to 3° in an angle range of -30° to -60°); As the missile's final velocity VM increases at the moment of detonation, the value of the angle characterizing the fragmentation field back-front also increases (up to 12° with an increase in the missile's final velocity from 600 m/s to 800 m/s). The maximum differences occur when the angle between the longitudinal axes of the aircraft and rocket AZwarhead and the terminal velocity of the rocket VM are varied simultaneously. In this case, errors can be as high as 15° or more (Figure 5.2.11), where: for the trailing boundary of the shattered field, the difference is 116°-101°= 15°.

Figure 5.2.11 - Effect of simultaneous change in final missile velocity VM and angle between longitudinal axes of aircraft and missile AZwarhead:
top - VM = 800 m/s, AZwarhead = 30°;
bottom - VM = 600 m/s, AZwarhead = 60°

The fragment dispersal model (preformed and hulled striking elements) used by specialists of Almaz-Antey Corporation calculates the velocity and coordinates of each of the fragments (more than 12,900 trajectories) at any time, as well as the fragment field density distribution at any selected distance and direction from the detonation point. The fragments (separately Heavy and Light fractions, as well as Shell fragments) in the software package are modelled using material points and their motion is described by kinematic equations of motion, taking into account the initial (x_0i, y_0i, z_0i) and current coordinates (x_i, y_i, z_i), and components of fragment velocities (v_xi, v_yi, v_zi).

During computational experiments associated with the development of software modules responsible for simulating fragment dispersal under dynamic conditions, various variants of models were tested: fragment dispersal from a "point"; fragment dispersal from a "segment" corresponding to the linear dimensions of the warhead; fragment dispersal from an "elliptical cylinder" whose shape virtually coincides with the actual shape of the warhead. In the course of the experiments it was established that the shape of the warhead specified in the model had a considerable influence on the simulation results. This is due to the close proximity of the warhead to the surface of the aircraft (about 1.6-2.0 m), which is comparable to the linear dimensions of the warhead itself (over 0.5 m). Therefore, the final version of the fragment dispersion model took into account the shape of the warhead.