Vulnerability is an important concept of target performance and a critical target characteristic,both in traditional fields,modern scientific and technological domains,and the military domain. At present,there are still prominent issues such as lack of unity,clarity and accuracy in the concept of target vulnerability. It brings a lot of problems to the research on target vulnerability,especially the assessment of target vulnerability. To clarify the related concepts of target vulnerability,the theoretical analysis,example illustration and other methods were used to explore it. A clear and precise definition of target vulnerability was provided,which refers to the degree of difficulty for a target to sustain functional damage under the conditions of being detected/perceived,subjected to damage element,and experiencing physical damage. The vulnerability includes perceived vulnerability,attack vulnerability,physical vulnerability,and functional vulnerability. Among these,physical vulnerability further includes structural vulnerability and material vulnerability. This definition is the broad sense of target vulnerability. In actual use,the narrow-sense definition of target vulnerability is mainly adopted,which refers to the degree of difficulty for a target to be damaged under the single action of a certain damage element or the combined action of multiple damage elements. This definition does not consider perceived vulnerability and attack vulnerability,but mainly considers physical vulnerability and functional vulnerability. Based on the clear definition of target vulnerability,the characteristic quantity/measurement of target vulnerability,the relationship between target vulnerability and weapon ammunition effectiveness,and the relationship between target damage probability and target survival probability were analyzed. The significance and method of target vulnerability research were discussed. This study has important theoretical reference significance for related research on target vulnerability.

During the vertical movement underwater,vehicles are highly susceptible to the marine environment,leading to unstable motion postures. Uncontrolled and unpowered launching has become inadequate in deep water and strong disturbance conditions. PID control,dynamic fluid body interaction,and dynamic nesting/sliding mesh techniques were employed to construct an integrated numerical calculation method that couples fluid dynamics,motion,and control in this paper. The motion process of underwater controlled-propulsion vehicles,analyzing the evolution of tail cavitation and ballistic characteristics under different tail jet pressures(6 MPa,10 MPa,12 MPa)were numerically simulated. The results show that during the merging process of supersonic jets and tail cavitation,the tail gas mass breaks due to interface instability and nozzle swaying,with the break occurring earlier as nozzle pressure increases. Inside the tail spray cavitation,a complex wave system structure exists. At higher nozzle pressures,the jet is under-expanded,resulting in multiple high and low-pressure areas formed by expansion and compression within the gas bubble. Over time,a Mach disk perpendicular to the axis appears near the nozzle exit. Additionally,the larger the nozzle pressure,the greater the disturbance torque caused by the tail spray flow. Increasing the nozzle pressure from 6 MPa to 12 MPa reduces the maximum deviation angle during motion by 18.5%,decreases the overshoot from 32% to 22%,resulting in less attitude fluctuation and better ballistic stability.

To study the thrust performance of underwater detonation engine(UDE),the thrust calculation method for the simplified UDE model was derived. Based on the VOF multiphase-flow model,the UDE with different nozzle-configurations using air as oxidant and gasoline vapor as fuel was numerically simulated. The thrust source of UDE and the propulsion performance of the engines under different equivalence ratios and nozzle configurations were discussed. The results show that the thrust sources of UDE mainly include three parts:internal thrust wall,annular thrust wall and nozzle wall. The thrust of internal thrust wall contributes more than 67% to total thrust,and the thrust of annular thrust wall contributes more than 16% to total thrust. The complex wave system and detonation products at the engine outlet interact with the engine wall,creating multiple peaks in the thrust curve of UDE. After installing different nozzles,the nozzles have a significant effect on the improvement of thrust performance. The convergent nozzle can enhance the intensity of the reflected shock wave of underwater detonation,but the negative thrust brought by the nozzle wall reduces the specific impulse and average thrust by 11.31% compared with the straight nozzle. The expansion nozzle weakens the transmission shock wave and reflection shock wave of underwater detonation,but the increase of the pressure area of the nozzle increases the specific impulse and average thrust by 28.09% compared with the straight nozzle,significantly improving the propulsion performance of UDE.

In order to study the penetration resistance of the corrugated aluminum plate filled with ceramic rod composite structure under different impact positions,a multi-ceramic-rod reinforced composite structure composed of trapezoidal corrugated aluminum plate was designed,followed by ballistic impact test and numerical simulation. By comparing the failure mode,energy absorption efficiency and velocity variation patterns under different impact points,the anti-penetration mechanism of the structure at three typical positions was obtained. The results show that the energy absorption of the multi-ceramic-rod reinforced trapezoidal corrugated aluminum plate is composed of the crushing energy dissipation of the ceramic panel,the shear expansion and plastic deformation of the trapezoidal corrugated aluminum plate,the fracture and crushing of multiple ceramic rods,and the tensile failure of the PE backplate. The ballistic resistance exhibits significant position-dependent characteristics,particularly influenced by ceramic rod spatial distribution and backplate support capacity. In composite structures,compared the midpoints of the upper and lower bases of the trapezoid with the midpoint of the oblique side,the protective area of the ceramic rod is larger,the ceramic crushing area is larger,and the anti-penetration ability is stronger. During high-velocity penetration of the target plate,due to the common constraints of the aluminum plate and the PE backplate behind the ceramic rod,the ceramic fragmentation near the midpoint of the lower base is more thorough compared to the upper base,leading to a further improvement in anti-penetration performance. The anti-penetration ability is improved,resulting in 20.45% and 8.14% increases in ballistic limit velocity compared with the other two places. The research results provide a theoretical guidance for the design of the reinforced corrugated structure.

The rotating band engraving process during artillery firing is transient in duration,which involves intense interactions between the rifling and the rotating band,exerting significant influence on the initial state of projectile motion within the barrel. Standardized modeling and setup procedures is a critical prerequisite for comparing the dynamic responses of rotating band engraving under different internal bore structures. Regarding this issue,basic parameterization of the finite element analysis process for rotating band engraving was studied. Specifically,mesh node coordinates were calculated through scripting,and the correspondence between mesh nodes and elements was established to generate finite element models of rifled barrels. Additionally,the execution logs of finite element software were compiled to proceduralize the modeling of the projectile rotating band and the preprocessing of rotating band engraving. A GUI plugin capable of one-click generation of rifled barrel and projectile rotating band finite element models,along with automated preprocessing configurations,was developed. The engraving processes under varying internal bore structural parameters were analyzed. The study focused on the effects of structural differences in rifling profiles,land height and land width on the rotating band engraving process. Dynamic simulation shows that in hybrid rifled barrels,the resistance encountered by the rotating band during engraving is smaller than that in uniform-twist rifled barrels,and the maximum stress at engraving completion is also lower. Reduced land height or narrowed land width decreases the internal bore resistance during rotating band engraving,resulting in faster engraving velocities.

Subject to the limitations of confined projectile spatial dimensions and diminutive control surfaces,glide-guided projectiles are characterized by diminished lift-to-drag ratios,constrained maneuverability,and compromised disturbance rejection capabilities,thereby rendering them highly susceptible to intricate external stochastic perturbations. To unravel the propagation dynamics of uncertainties within the stochastic nonlinear systems governing glide projectiles and to quantify the sensitivity of multiphase full-trajectory behaviors to heterogeneous stochastic uncertainties,this study formulates a high-fidelity multidimensional dynamical model that rigorously encapsulates uncertainties inherent to system modeling approximations,initial state variabilities,aerodynamic coefficient fluctuations,and meteorological parameter stochasticity. Employing a Latin hypercube sampling methodology,a composite uncertainty quantification and propagation framework is devised,synergizing non-intrusive spectral polynomial chaos expansion with stochastic response surface methodology. The efficacy of this framework is empirically validated through high-dimensional uncertainty propagation simulations spanning the entire projectile trajectory,with rigorous benchmarking against Monte Carlo simulation(MCS)outcomes. Numerical experiments demonstrate that the integrated trajectory exhibits markedly amplified sensitivity to aerodynamic parameter uncertainties relative to perturbations in booster propulsion mean thrust and atmospheric density profiles,with the former dominating terminal precision degradation. Moreover,the proposed framework attains computational acceleration exceeding conventional MCS by orders of magnitude while preserving statistical fidelity,thereby circumventing the curse of dimensionality endemic to high-order uncertainty propagation analyses. These findings furnish a foundational paradigm for probabilistic trajectory optimization and resilience enhancement in next-generation precision-guided munitions.

The traditional impact point prediction guidance methods require a lot of iterations in the solution process,and the real-time processing ability of information is poor. The impact point prediction model based on machine learning method can reduce the prediction time and improve the prediction accuracy. However,the existing impact point prediction model is mostly trained by the uncontrolled flight data of the projectile,without considering the influence of control force and torque,resulting in a remarkable difference from the actual flight state of the guided projectile. In this paper,a guidance and control method based on machine learning was proposed. The flight state parameters of the projectile in the controlled state were used as the training set,and the controlled landing point prediction model was established. Combined with the proportional-differential control law,the guidance and control process based on this landing point prediction model was constructed. The simulation results show that the impact point prediction model trained by BP neural network can accurately predict the impact point,and the proposed guidance and control method can achieve high-precision guidance and control. The relative error of the range direction of the hit point is about 0.01%,and the relative error of the sideslip direction is about 3.1%. The feasibility and effectiveness of the designed guidance and control method are verified,which can provide reference for the in-depth application of machine learning method in the field of controlled projectile technology.

In order to maintain excellent aerodynamic characteristics of extended-range guided projectiles in the entire flight airspace while enhancing their maximum range and flight efficiency,morphing vehicle technology was applied to large-caliber extended-range guided projectiles. The aerodynamic shape and variable swept wing of a variable swept wing extended-range guided projectiles was designed. Furthermore,a trajectory optimization methodology specifically adapted for extended-range guided projectiles featuring continuous variable swept wing capability was proposed. By introducing a deformation parameter to characterize the variation of the fin swept angles of the projectile,a longitudinal dynamics model for extended-range guided projectiles with variable swept wing was constructed. Particle swarm optimization algorithm was employed,with maximum overall lift-to-drag ratio as the objective function,to simultaneously optimize wing sweep angles and rudder deflection angle. Ballistic simulation was carried out for the variable swept wing extended-range guided projectiles and its fixed shape respectively. The simulation results show that the variable swept wing extended-range guided projectiles can continuously adjust wing sweep angles according to the flight velocity of the projectile,thereby modulating aerodynamic drag and lift to maintain optimal lift-to-drag ratio characteristics throughout the ballistic glide phase. Compared to the guided projectile with fixed shape,the guided projectile with variable swept wing achieves significant range increase of 8.9%. The research method provides a theoretical foundation and reference for the optimal design of the ballistic trajectory of the continuous variable sweep wing extended-range guided projectiles.

The gliding-guided projectile employs in-flight power-on for alignment. The roll angle is utilized to initialize the inertial navigation and resolve guidance command. Therefore,roll angle accuracy is vital for precisely striking of the guided projectile. In this paper,a new method was proposed to improve the roll angle accuracy of guided projectile by online estimate and real-time correction of roll angle errors during the glide phase. Firstly,based on the attitude kinematics and roll stabilization control,the roll alignment was achieved by gyroscope. Secondly,the guidance and control model incorporating roll alignment error was built. The mathematical relationship between roll alignment error and overload in quasi body frame was derived to modify the roll angle on basis of the instantaneous equilibrium principle and projectile trajectory feature. Finally,the overloads in quasi body frame can be estimated by extracting the satellite velocity signal using differential-tracker. Simulation results show that the roll angle alignment error can reach 15.5° due to various influencing factors. Considering all deviation conditions,the roll angle accuracy is improved to within 5°through the proposed method,demonstrating both effectiveness and strong robustness. Besides,the results based on the flight experiment also show the effectiveness of the proposed method,which can be applicated in engineering implementation.

The coupled aerodynamic heating and ablation deformation on the surface of hypersonic projectiles induce significant aerodynamic configuration evolution,which subsequently impacts flight stability and external ballistic performance. Therefore,multi-condition aerodynamic heating calculation method for different projectile structures,flight conditions,and environments is crucial for optimizing thermal protection system and advancing engineering applications in hypersonic projectiles. Based on the existing aerodynamic heating calculation methods for hypersonic projectiles flying at zero angles of attack,a spherical coordinate system was established in response to the stagnation point offset phenomenon induced by angles of attack in spherical cone. The conversion relationship between the projectile coordinate system and the velocity coordinate system was utilized to carry out aerodynamic heating simulation analysis of three-dimensional spherical cone shaped projectiles flying at angles of attack. The distribution of heat flux density on the busbar of the spherical head and the conical body was obtained. The heat flux density and heating status were compared with and without an angle of attack. The calculation results are basically consistent with experimental data. The simulation results show that the heat flux density of the spherical head is much higher than that of the conical body,and the heat flux density of the windward busbar with an angle of attack is greater than that of the leeward side. The calculation method used in this article can satisfy the accuracy and speed requirements for simulation and design of ultra high speed flight trajectories. The proposed calculation method and results provide a foundation for the rapid coupling calculation of aerodynamic ablation and external trajectory of hypersonic projectiles in the future.

Upon primer ignite the firing charge,the combustion gases propel gunpowder particles through controlled axial propulsion. The sloping chamber,which is a gradual shrinkage section between the chamber and the barrel bore,will inevitably be subjected to the irregular collision of the gunpowder particles,resulting in localized erosive wear. In the initial ballistic stage,with high chamber pressure,fast particle velocity and large particle size,the erosive wear caused by the impact of gunpowder particles on the sloped chamber is more prominent. In order to focus on this collision damage effect,according to the characteristics of particle motion,collision and gas-solid two-phase flow in the initial ballistic phase,a three-dimensional unsteady gas-solid two-phase flow model was established based on the Euler-Lagrange approach,using the computational fluid dynamics-discrete element method(CFD-DEM)coupled method. Numerical simulation of the erosion and wear of the gunpowder particles on the sloped chamber of a 155 mm artillery was carried out. The results show that the erosive wear in the starting section of the sloping chamber is significant and has an annular distribution,while the erosive wear in the rest of the area is minor and has an irregular cloud-like distribution. The mass loss of the sloping chamber increases exponentially with time. When the taper of the sloping chamber is increased from 1/10 to 1/5,the mass loss of the sloping chamber increases with the increase of taper,and the larger the taper is,the larger the rate of mass loss is.

The high-temperature,high-pressure,partially reacted jet ejected from the deflagration launcher undergoes secondary reactions with the ambient air when entering the initial the chamber,generating intense thermal shock and ablation effects on the launcher. To mitigate the adverse impacts,the influence of secondary reactions on the deflagration launcher and projectile interior ballistics was investigated in this paper. Thermodynamic properties of the launcher's deflagration products were calculated using the minimum free energy method. The chemical reaction mechanism of secondary reactions within the initial chamber was described based on the finite-rate/eddy-dissipation model. The projectile's motion was simulated via a dynamic mesh layering technique,establishing a secondary reaction flow model in the initial chamber with moving boundaries. The validity of the model was verified through comparison with experimental data. Research results indicate that chambers experiencing secondary reactions exhibit faster temperature rise rates and higher peak temperatures compared to non-reaction chambers. As O₂ in the chamber depletes,temperatures gradually decrease. The energy released from secondary reactions enables the projectile to achieve greater acceleration in shorter time intervals while maintaining peak acceleration levels briefly. Consequently,the projectile attains higher velocity and greater displacement within the equivalent timeframe. Expanding the initial chamber volume can alleviate excessive projectile loading by reducing acceleration growth rates and peak acceleration magnitudes. These findings provide theoretical foundations for the design of deflagration launcher and interior ballistics performance.

Cased telescoped ammunition(CTA)is a novel type of ammunition which adopts a two-stage ignition combustion technology. The first-stage ignition provides the projectile with a certain initial velocity along the guiding barrel in the barrel,impacting the slope of chamber. While the second-stage ignition generates propellant gas to drive the projectile out of the barrel at high speed. To deeply study the internal ballistic characteristics of the two-stage ignition combustion technology in CTA,a 40 mm short barrel experimental platform was designed and constructed. High-speed video recording and a pressure sensor were utilized to measure the impacting velocity and pressure of the sloped of chamber during the test. The test results show that the projectile impacts the sloped of chamber with a velocity of 22 m/s after the first-stage ignition and stop at the sloped of chamber. Then,the projectile flies out of the barrel quickly after the two-stage ignition is activated. Additionally,a zero-dimensional internal ballistic numerical model of the two-stage ignition of the CTA under the test conditions was established to simulate the two-stage ignition process of the CTA under identical loading conditions. Comparative analysis between numerical simulations and experimental data validated the accuracy of the proposed model. The internal ballistic performance of the 40 mm armor-piercing projectile of CTA was simulated to analyze the effects of different loading charges on the projectile movement process. This study provides a reference for the subsequent research on the two-stage ignition technology of the CTA.

Based on the background of a kind of uniform-diameter barrel gas gun and considering its working principles and structural characteristics,the internal ballistic equations of the gas gun were established,taking into account gas leakage through the gap of projectile and barrel. A simulation model of the gas gun was developed in Autodyn. The correctness of the simulation model was verified by comparing the calculated results of the simulation model with those of the theoretical model. Computations were conducted on both simulation model and theoretical model with different gaps between projectile and barrel. The results show that with the increase of gap size,the gas leakage rises gradually,and the muzzle velocity of projectile shows a corresponding gradual decrease. The launching device under the two conditions of using conical obturator ring and tail skirt obturator ring was simulated and calculated respectively through Autodyn. The obtained projectile velocities were compared with the projectile velocity without an obturator ring. The results show that the projectile velocities using obturator ring are obviously higher than those without an obturator ring. Multiple monitoring points were applied to the two kinds of obturator rings. The radial displacement and pressure of the two kinds of obturator rings under the coupled effects of high-pressure gas,barrel and projectile constraints were recorded by the monitoring points. The mechanism of the obturator ring was studied,and the difference of the sealing effect of the two kinds of obturator rings was analyzed. Analytical results revealed that the tail-skirted obturator ring exhibits superior sealing effectiveness compared to its conical counterpart.

Aiming at the dynamic characteristics of missile vertical cold launch under ship swaying motion,based on the theory of interior ballistics,a coupled interior ballistic theoretical model under ship swaying motion was established. Based on coupled and uncoupled interior ballistic models,interior ballistic calculations of ship unidirectional and composite motion were carried out for typical scenarios. The results imply that under six-level sea condition,compared to the uncoupled model,the upper and lower limit of the range of the outlet velocity obtained by the coupled model change by -0.04 m/s and 0.05 m/s,when the ship performs rolling motion. When the ship performs pitching motion,the upper and lower limit of the range of the outlet velocity obtained by the coupled model change by -0.46 m/s and 0.48 m/s. When the ship performs heaving motion,the upper and lower limit of the range of the outlet velocity obtained by the coupled model change by -0.43 m/s and 0.47 m/s. When the ship performs a composite motion of roll,pitch and heave,compared to uncoupled model,the upper and lower limit of the range of the outlet velocity obtained by the coupled model change by -1.02 m/s and 0.98 m/s. Compared to the uncoupled model,the range of outlet velocity obtained by the coupled model is significantly narrowed. The model can provide reference for the simulation of vertical cold launch interior ballistics of missiles under ship motion.