Warhead Design Research Articles

Influence of explosive type and constant γ in Mott’s stochastic model on terminal-ballistics parameters of high-explosive warheads using numerical simulations

The research examined the use of numerical simulations for high-explosive (HE) munitions. Lagrange and Euler solvers from Ansys Autodyn, whose brief theoretical synopsis is given, were utilized. Numerical program modeling of materials under dynamic loads (explosives and solid bodies) is also explained. The study also provides a brief summary of relevant research works that address numerical simulations of the fragmentation of HE projectiles (warheads). First, using data from other authors, the numerical model in this paper was effectively validated. The original research in the publication included an evaluation of the influence of explosive type on mass distribution, as well as velocity and the kinetic energy of fragments on cylindrical warheads, along with some recommendations and findings. Results show that ordered by values of initial fragment velocity are explosives: Trinitrotoluen (TNT), H6, Comp. B, Octol, PBX-9404-3, and LX-10-1. Explosives LX-10-1 and PBX-9404-3 showed similar performance because both explosives are HMX-based mixtures, with LX-10-1 having 0.5% more Octogen (HMX). The greatest (fastest) expansion of fragments (for the given time frame of 150 µs) is present in the most potent explosives (LX-10-1 and PBX-9404-3) since they have the largest detonation velocities. In the configurations with stronger explosives (Octol, LX-10-1, PBX-9404-3), the front and rear cover of the cylinder is more fragmented than in the case of weaker explosives. The highest number of fragments is obtained with PBX-9404-3 explosive, 142% higher than using TNT charge. Also, as part of the original research in the paper, an assessment of the influence of the constant γ in Mott’s stochastic fragmentation model on the mass distribution of fragments and their kinetic energy was made. Results indicate that constant γ has the greatest influence on the number of very small fragments, which can be used when calibrating this constant with experimental data. The masses of fragments are relatively uniform (for all γ values) up to the mass group of 50–100 g, above which the most massive fragments are obtained when γ = 5. Most of the fragments have relatively high energy where that is, fragments of mass 0.5–2 g have an average kinetic energy of 470–650 J, while fragments of masses 50–100 g have an average kinetic energy of 50–85 kJ. Described numerical simulations are a valuable tool for HE warhead designers, as they can minimize the time and expense associated with optimizing HE munition design and effectiveness evaluation when used in conjunction with available analytical techniques and experimentation procedures.

Test design and theoretical calculation of cook-off characteristics and thermal safety venting area of RBOE charge

RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive, whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead. Based on the thermal decomposition reaction characteristics and combustion characteristics of each component of RBOE explosive, the cook-off calculation models of RBOE warhead before and after ignition were established. In addition, closed and vented warheads were designed, as well as fast and slow cook-off test devices. The cook-off characteristics and thermal safety venting area of RBOE warhead were extensively studied. The results showed that the closed RBOE warhead underwent deflagration reaction under both slow and fast cook-off conditions. The calculation result of the shell wall temperature before slow cook-off ignition response of the warhead was 454.06K, with an error of +1.75% compared to the test result of 462.15K, and the temperature rise rate calculated was in good agreement with the test. The calculated ignition time of RBOE warhead under fast cook-off was 161s, with an error of + 8.8% compared to the test result of 148 s, which verified the accuracy of cook-off model of RBOE warhead before ignition. According to the cook-off calculation model of the warhead after ignition and cook-off test of the vented warhead, it was determined that the thermal safety venting area was 1124.61 mm2 for fast cook-off and 530.66 mm2 for slow cook-off, effectively preventing the reaction of warhead above combustion. Therefore, this study provides a scientific basis for the thermal safety design and evaluation of insensitive warheads.

Methods for obtaining the actual radial distribution of the fragment velocity through X-ray photography

Short charges are typically used in the measurement of radial fragment velocity distributions by pulsed X-ray photography, due to the arrangement constraint of X-ray tubes. However, the radial velocity distribution of the one-line asymmetrical initiation was found to be significantly influenced by the end rarefaction waves. This means that the fragment velocity distribution measured using short charges cannot reflect the real influence of the initiation styles or warhead designs. This study proposes new methods for measuring the radial velocity distribution using X-ray photography while eliminating the effect of end-rarefaction waves. It can provide important references for related X-ray test methods and the development of high-lethality warheads.

Fragment velocity distribution formula of the thin-walled structure subjected to two-line asymmetrically initiated explosion

The thin-walled structure enveloping an explosive charge makes an ammunition warhead. Numerous studies have been conducted on the structural dynamics of the center-initiated charge explosion, including the casing fragmentation behavior and the fragment velocity distribution. Although adopting asymmetrical initiation could enhance the casing fragment velocity and energy utilization, the fragment velocity distribution of a two-line asymmetrically initiated warhead has rarely been studied and few formulae exist. However, the velocity distribution formula is valuable and necessary in the rapid design and lethality evaluation of warheads. Based on the concepts of the stationary point and local charge ratio of the Gurney equation, this work establishes a new velocity distribution formula for the two-line asymmetrically initiated warhead. An asymmetrical ratio function of the stationary point is first proposed for the two-line initiation and validated against the verified numerical modeling. Thereafter, to solve the undetermined parameters of the asymmetrical ratio function, it is discovered that there exists an overlapping effect for fragments at angles of 45° and 135° of the asymmetrical two-line initiation of a 90° central angle. Finally, to validate the entire mathematical model, experiments are conducted using X-ray photography. The mathematical model agrees strongly with the experimental results. This work could offer a solid reference for the rapid design and lethality evaluation of warheads.

The Design, Synthesis and Mechanism of Action of Paxlovid, a Protease Inhibitor Drug Combination for the Treatment of COVID-19.

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has presented an enormous challenge to health care systems and medicine. As a result of global research efforts aimed at preventing and effectively treating SARS-CoV-2 infection, vaccines with fundamentally new mechanisms of action and some small-molecule antiviral drugs targeting key proteins in the viral cycle have been developed. The most effective small-molecule drug approved to date for the treatment of COVID-19 is PaxlovidTM, which is a combination of two protease inhibitors, nirmatrelvir and ritonavir. Nirmatrelvir is a reversible covalent peptidomimetic inhibitor of the main protease (Mpro) of SARS-CoV-2, which enzyme plays a crucial role in viral reproduction. In this combination, ritonavir serves as a pharmacokinetic enhancer, it irreversibly inhibits the cytochrome CYP3A4 enzyme responsible for the rapid metabolism of nirmatrelvir, thereby increasing the half-life and bioavailability of nirmatrelvir. In this tutorial review, we summarize the development and pharmaceutical chemistry aspects of Paxlovid, covering the evolution of protease inhibitors, the warhead design, synthesis and the mechanism of action of nirmatrelvir, as well as the synthesis of ritonavir and its CYP3A4 inhibition mechanism. The efficacy of Paxlovid to novel virus mutants is also overviewed.

Fracture behavior and mechanism of highly fragmented steel cylindrical shell under explosive loading

An in-depth understanding of the fracture behavior and mechanism of metallic shells under internal explosive loading can help develop material designs for warheads and regulate the quantity and mass distribution of the fragments formed. This study investigated the fragmentation performance of a new high-carbon silicon-manganese (HCSiMn) steel cylindrical shell through fragment recovery experiments. Compared with the conventional 45Cr steel shell, the number of small mass fragments produced by the HCSiMn steel shell was significantly increased with a scale parameter of 0.57 g fitted by the Weibull distribution model. The fragmentation process of the HCSiMn shell exhibited more brittle tensile fracture characteristics, with the microcrack damage zone on the outer surface being the direct cause of its high fragmentation. On the one hand, the doping of alloy elements resulted in grain refinement by forming metallographic structure of tempered sorbite, so that microscopic intergranular fracture reduces the characteristic mass of the fragments; on the other hand, the distribution of alloy carbides can exert a "pinning" effect on the substrate grains, causing more initial cracks to form and propagate along the brittle carbides, further improving the shell fragmentation. Although the killing power radius for light armored vehicles was slightly reduced by about 6%, the dense killing radius of HCSiMn steel projectile against personnel can be significantly increased by about 26% based on theoretical assessment. These results provided an experimental basis for high fragmentation warhead design, and to some extent, revealed the correlation mechanism between metallographic structure and shell fragmentation.

Rational Identification of Novel Antibody-Drug Conjugate with High Bystander Killing Effect against Heterogeneous Tumors.

Bystander-killing payloads can significantly overcome the tumor heterogeneity issue and enhance the clinical potential of antibody-drug conjugates (ADC), but the rational design and identification of effective bystander warheads constrain the broader implementation of this strategy. Here, graph attention networks (GAT) are constructed for a rational bystander killing scoring model and ADC construction workflow for the first time. To generate efficient bystander-killing payloads, this model is utilized for score-directed exatecan derivatives design. Among them, Ed9, the most potent payload with satisfactory permeability and bioactivity, is further used to construct ADC. Through linker optimization and conjugation, novel ADCs are constructed that perform excellent anti-tumor efficacy and bystander-killing effect in vivo and in vitro. The optimal conjugate T-VEd9 exhibited therapeutic efficacy superior to DS-8201 against heterogeneous tumors. These results demonstrate that the effective scoring approach can pave the way for the discovery of novel ADC with promising bystander payloads to combat tumor heterogeneity.

Study on the Influence of Missile Cabin on Fragment Velocity under Explosive Detonation Impact

For the air-to-air missile warhead, there is a cabin with a certain thickness at a distance around the fragments. At present, the influence of missile cabin has not yet been taken into account in the study of fragment velocity. In this paper, based on the law of conservation of energy, the theoretical equation of fragment velocity considering the kinetic energy of cabin debris was deduced. Then, the rationality of the theoretical formula is validated through the static explosion experiments of two prototype warheads, one with a titanium alloy cabin and the other without any cabin. It was found that after the warhead is equipped with the cabin, part of the energy is consumed to drive the cabin debris, resulting in a decrease in fragment velocity, but the velocity of cabin debris was greater than that of fragment of warheads without any cabin. Besides, through numerical simulation, the driving process of fragments and cabin debris during explosive detonation loading of the warhead with the cabin was studied, which can be divided into six stages, and the error between numerical result and experimental value is not more than 4.8%. Finally, the variety regulation of fragment velocity and cabin debris velocity at different interval distances was further studied by numerical simulation. The results indicate that fragment velocity of warheads with cabin at different interval distances is basically the same, but cabin debris velocity decreases with the increase of interval distance. This conclusion can provide a reference for the structural design and fragment velocity evaluation of warheads with cabin.

Experimental study on fragments dispersion characteristics of elliptical cross-section casing under explosive loading

To better understand the fragments dispersion characteristics of elliptical cross-section warhead (ECSW), static explosion experiments were conducted with four ECSWs and one circular cross-section warhead (CCSW). The warheads were designed with the same mass ratio of charge to the metal casing, and the difference in cross-section shape was indicated by the shape ratio. The experimental results indicated that ECSW fragments dispersion in their radial direction deviated from the normal direction of casing under explosive loading. The radial deviation angle decreased with the higher shape ratios. In the axial direction, the axial projection angle of fragment increased gradually from the major to the minor axis. Additionally, the fragment velocity and density in the minor axis direction increased noticeably compared to the major axis, and the difference reduced as the shape ratio increased. A formula for predicting the radial velocity distribution of the fragments was proposed, and the maximum relative error between the calculation and experiment results is less than 5 %. Finally, the driving mechanism of ECSW was preliminarily revealed. The findings serve as a fundamental basis for future research on ECSW and offer valuable insights for the development of innovative warhead designs.

Efficiency Analysis of Fragmentation Warheads Through Advanced Modeling Techniques: Experimental and Numerical Study

This research investigates the efficiency of fragmentation warheads through a comprehensive comparison of numerical and analytical modeling techniques, supplemented by arena tests. Advanced numerical models developed within Ansys Autodyn, alongside the mean area of effectiveness software, demonstrate robust capabilities in predicting warhead‐soft target interactions. Our numerical model is supplemented with a complex analytical model, and the integration of these two approaches addresses a significant research gap by providing a thorough evaluation of warhead efficiency. This integrated model serves as a valuable tool for warhead design and optimization. Validated with experimental results, the simulation outcomes show excellent agreement with the arena test data, confirming the accuracy and reliability of the developed models. This study explicitly addresses key research gaps, including the integration between experimental and numerical analyses, the gap between explosive propulsion and the determination of efficiency, and the need for a comprehensive tool for warhead design and optimization. By exploring various warhead design configurations and initiation methods, the research offers critical insights for optimizing warhead performance. Notably, nonuniform barrel‐shaped warheads exhibit a wider fragment distribution, significantly improving weapon‐target interactions, particularly at lower impact angles. The study delves into the key parameters influencing warhead performance, providing detailed justifications for their selection and evaluating the sensitivities of these parameters on the results. This analysis underscores the importance of choosing appropriate parameters for accurate predictions and effective warhead design. In addition, the research highlights the original achievements in overcoming major difficulties and challenges in the field, such as integrating complex numerical and analytical models for comprehensive evaluation. The findings contribute to the advancement of fragmentation warhead design, offering designers reliable tools and guidelines to enhance lethality and efficiency in weapon‐target engagements. Future work aims to expand the software’s capabilities to include diverse targets, fragment types, and interaction geometries, further advancing the field of fragmentation warhead design. By addressing the gaps and challenges identified, this research paves the way for more effective and optimized warhead configurations, enhancing their overall performance and impact.

Double casing warhead with sandwiched charge: The axial distribution of fragments velocities

The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity, and the previous work has presented a calculation formula to determine the maximum fragment velocity. The current work builds on the published formula to further develop a formula for calculating the axial distribution characteristics of the fragment velocity. For this type of warhead, the simulation of the dispersion characteristics of the detonation products at different positions shows that the detonation products at the ends have a much larger axial velocity than those in the middle, and the detonation products have a greater axial dispersion velocity when they are closer to the central axis. The loading process and the fragment velocity vary with the axial position for both casing layers, and the total velocity of the fragments is the vector sum of the radial velocity and the axial velocity. At the same axial position, the acceleration time of the inner casing is greater than that of the outer casing. For the same casing, the fragments generated at the ends have a longer acceleration time than the fragments from the middle. The proposed formula is validated with the X-ray radiography results of the four warheads previously tested experimentally and the 3D smoothed-particle hydrodynamics numerical simulation results of several series of new warheads with different configurations. The formula can accurately and reliably calculate the fragment velocity when the length-to-diameter ratio of the charge is greater than 1.5 and the thickness of the casing is less than 20% its inner radius. This work thus provides a key reference for the theoretical analysis and the design of warheads with multiple casings.

Design of Visualization Simulation Software for Fire Planning Based on Unity 3D Technology

How to evaluate the effective firepower intensity generated by ammunition in war is an important basis for tactical decision-making. In order to calculate the firepower kill range formed by the combined action of multiple high explosive bombs, this paper uses digital simulation methods to establish a firepower planning model for multiple high explosive bombs based on the hit rate model and power model of the ammunition. A visual simulation software for explosive bomb firepower planning based on C + + programming language and Unity 3D engine is designed to support rapid calculation and visual display of firepower planning results. The results show that the visual simulation software for fire plan can effectively calculate the distribution pattern and fire damage of ammunition, dynamically visualize the entire terminal damage process, evaluate the effective fire distribution results, and lay a foundation for the design of warheads and the efficient use of ammunition.

Optimal design and power research of the rod-type damage element warhead

In order to improve the damage power of linear multiple explosively formed penetrators, three rod-type damage element structures were designed, and the formation of different structures was studied through numerical simulation. The final rod-type damage element structure was optimized. Under explosive loading, a rod-type penetration body with an aspect ratio of 4.1 can be formed. Combined with the optimization design of the rod-type damage element, the warhead power experimental research was carried out. The results show that the resulting rod-type penetrating body has good formation, stable flight and high-efficiency damage ability to thick-walled targets.

The penetration performance and matching design method of tandem warhead against ultra-high strength concrete

The penetration performance of the tandem warhead against ultra-high strength concrete and the matching relationship between the precursor shaped charge and the following kinetic energy warhead of the tandem warhead are researched to enhance the damage effect. For the precursor shaped charge, the formation and penetration properties of jet are studied in a combined experimental and numerical way. The value of kinetic energy/target borehole volume of C130 ultra-high strength concrete under the penetration of titanium alloy jet is obtained and the relationship of the depth and diameter of the precursory penetrating cavity is developed. For the following kinetic energy warhead, the numerical simulation of penetrating the pre-damage C130 ultra-high strength concrete is carried out and significant influence of the pre-damage crater’s depth and diameter on the relay penetration depth is observed. The matching method for the pre-damage crater resulting from the precursor shaped charge and the follow-through depth of the following kinetic energy warhead is set up on the basis of obtained penetration rules of two stages, which could provide helpful reference for the preliminary fast design of tandem warhead against ultra-high strength concrete.

Experiment and instantaneous driving simulation of explosion dispersion process of central tube for submunition

In order to study the influence of explosion dispersion of submunition on the dispersion velocity and pressure characteristics of subunits, the experimental study of explosive dispersion of the central tube was carried out when the explosives with low detonation velocity were applied in central tube as the main charge. In addition, the explosion dispersion test process was recorded by high-speed photography. RDX-based aluminized explosive samples with low detonation velocity were prepared and tested, and the low detonation velocity performance changes under different charge diameters and densities were obtained. Based on the explosive dispersion test of the central tube of the submunition, the physical model and three-dimensional axisymmetric finite element model of the central tube, subunit and aluminium alloy shell with prefabricated grooves are established. The fluid-structure coupling calculation method is used to simulate the explosive dispersion process. The simulation results are compared with the test results, and the pressure distribution characteristics of the subunit and the variation law of the dispersion velocity are analyzed. The effectiveness of the engineering calculation method of JWL equation model parameters is verified. The results show that using RDX based aluminized low detonation velocity explosive as the main charge of the central tube structure can achieve the design goal of the explosive dispersion for submunition, and the explosion dispersion model of submunition can accurately describe the dispersion characteristics of the subunit. The research results can be used to guide the structural design of submunition warhead.

Research Status and Development Trend of Tandem Armor-Breaking Warheads

In order to cope with the continuous progress of tank protection technology, it is imperative to optimize and improve the ability of existing armor-breaking warheads. This paper mainly introduces the development history of explosive reactive armor, shaped charge jet formation theory, shaped charge jet penetration theory, armor-breaking warhead technology, series armor-breaking warhead technology and research status of armor-breaking/killing compound warhead technology. Finally, the development trend of armor-breaking warhead in the future is described, in order to provide some enlightenment for the design and improvement of armor-breaking warhead in the future.

Numerical simulation research on fragments formation of cylindrical cased charge based on SPH method

In order to obtain the fracture and fragmentation of a cased charge under blast loading, the JWL equation of state of HMX-based PBX was fitted based on a cylinder test firstly, then the smooth particle hydrodynamics (SPH) method was used to perform a simulation of cased charge under interior blast loading, in the meantime, an blast test of cased charge was conducted. The results show that the parameters of JWL equation of state and the simulation method were reasonably. The simulated fragments velocities and calculated results from empirical formula agreed well with each other, the maximum error did not exceed 9.5%. Under the direct loading of the detonation wave, the fragments velocities increased to more than 1000m/s immediately within 5us, and then the fragments were continuously accelerated by detonation products and shock wave until the fragments reached the maximum velocities in the later 250us. Eventually, the shape of expansion contour of the casing tended to be ellipsoid. The method and results can provide references for the power design of the fragment warhead, as well as the protection design against the fragments.

Review of Evaluation Methods of Underwater Explosion Power of Explosives

Reasonable evaluation of underwater explosion power of explosives is very important for underwater warhead design and other tasks. This paper summarizes the typical experiments of underwater explosion power evaluation, discusses the power characterization methods involved in the tests, and focuses on the explosion bulge test of plate structure and its corresponding dimensionless deflection characterization means. Based on the existing research results, it is proposed to establish a standardized effect target evaluation method, strengthen the research on the relationship between work parameters, explosive detonation parameters and load parameters, and apply the dimensionless deflection method in explosion expansion test to the characterization of underwater explosion power.

Acceleration Measurement Analysis on Warhead Penetration/Explosion on Concrete Targets

Blast wave will be generated in concrete when hit by projectiles at a high velocity. Such blast wave will severely threaten structures. The impact acceleration on the structure surface is an instinctive indicator of the propagation of blast wave, since the acceleration is closely linked to the penetration and explosion state of the warhead. This paper conducted acceleration measurement and analysis on the penetration and explosion of penetration warheads on reinforced concrete target. In addition, test results, on-board testing results and numerical results have been compared to analyze the damage process and mechanism of the target, providing basis for warhead design, target design, simulating calculation and damage efficacy evaluation.

AI 공격용 드론 개발 방향 및 시사점

The role of attack drones in the ongoing war between Ukraine and Russia is drawing worldwide attention. In order to prepare for changes in the defense security environment and rapid decline in military resources, the Ministry of National Defense announced the National Defense Innovation 4.0 Basic Plan in March 2023, and established the concept of joint operation by reflecting the operation of AI-based manned and unmanned complex systems and new concept weapon systems. did Drones are the most important force in building manned and unmanned complex systems, and the dronebot combat system will be the basis for promoting Defense Innovation 4.0. Drones are a system that can be operated for multiple purposes that change their use according to mission equipment, and it is key to have advanced technology that is suitable for the future battlefield environment and efficient. If the existing attack drone is an operating system in which combatants remotely control the ground control device while watching the ground control device, the future direction of the development of attack drones for the Korean military to apply to dronebots is an AI attack drone in which the drone detects the target by itself and directly strikes and self-destructs. will develop into In order to develop AI attack drones, not only the performance of the drone system, but also AI-based cutting-edge technology for object tracking technology, object identification technology and shape recognition technology of reconnaissance equipment (EO/IR), which is mission equipment, as well as attack ammunition or Small, high-performance warhead design technology, ultra-small fuze design technology, shock absorption and launch control device technology, etc. must be developed to mount the projectile. In addition, as the amount of image information acquired through mission equipment increases, high-speed data transmission technology development to improve the transmission rate between the aircraft and the ground control equipment in real time must be simultaneously developed. It is necessary to quickly overcome drone and AI technologies, which are currently very poor compared to advanced countries, and take the lead in developing intelligent AI attack drones with excellent autonomy based on Korea's excellent ICT technology. Therefore, this study aims to find out the technological trends of domestic and foreign attack drones and to consider the development plans and tasks of AI attack drones.