The theoretical development of weapon equipment system of systems engineering is reviewed from three aspects of the formation process of combat System of Systems, such as mutual reference relationship and connotation, research status of main links, intelligence, toughness and emergence, and the theoretical development of weapon equipment System of Systems engineering under the guidance of system engineering theory is summarized and analyzed. In the space field, the System of Systems project is the main carrier to carry out application exploration in two aspects of technology and management, based on which the future development direction is prospected.

The engine nozzle is prone to work with a state of over-expansion in a high-pressure underwater environment, which will influence the jet flow field and thrust. Experiments of over-expansion supersonic underwater gas jets at different co-flow velocities are conducted using a circulating water tunnel, various forms of wake cavity and their corresponding thrust time-frequency characteristics are analyzed. It is shown that at low velocities, the over-expanded gas jet is difficult to form a cavity attached to the wake or a pulsating foam-type wake cavity. Under such flow conditions, the vehicle experiences pronounced thrust oscillations with a rich frequency spectrum (36 to ${743}\mathrm{\;{Hz}}$). As the Froude number at the co-flow velocity increases to ${Fr}= {8.57}$, the jet eventually forms an intact tail cavity, at which point the amplitude of the thrust oscillations decreases significantly and the mean thrust value increases significantly. The internal gas reflux phenomenon in the jet-induced tail cavity is also directly observed, and the observed reflux velocity at ${Fr}= {8.57}$ is about ${1.13}\mathrm{\;m}/\mathrm{s}$.

During the flight of aircraft, a coupling effect between the fluid aerodynamic forces and the structural elastomer will be formed, and this interaction may cause different degrees of damage to the divergence and jitter of the elastomer, resulting in safety risks. A numerical simulation method of fluid-structure coupling based on time-space conserved element solution and immersion boundary is proposed. The method of time-space conserved element solution is used to calculate the fluid domain, and the submerged body-fitted mesh boundary method is used to identify the fluid-structure coupling boundary surface. Taking NACA0018 as an example, the cloud image of wing outflow field pressure and velocity at different angles of attack is obtained through simulation data. At the same time, the buffeting amplitude of the wing under different inlet velocity and its rule are studied. The research shows that the fluid-structure coupling method has high accuracy and stability in solving high-speed compressible flows with complex flow patterns, including shock wave or detonation and large deformation problems, providing a reference research method for related research.

To achieve attitude stability and depth control of a underwater vehicle, the dynamic characteristics and the influence of the tail rudders and sliding force on its dynamic characteristics are analyzed. The system is divided into three loops, and the controllers are designed for them. According to the damping characteristics of the system, pole placement is performed on the diagonal rate loop, followed by hysteresis correction on the overload loop based on the frequency domain characteristics of the system. Finally, the time domain characteristics of the depth loop are improved by adjusting the gain. Through simulation experiments, it has been verified that the control law designed can achieve attitude stability and depth control of a underwater vehicle, and has certain anti-interference ability. The linear control methods used in the article are common in engineering practice, and the calculation of controller parameters is based on the system's time-domain and frequency-domain performance indicators. The physical meaning is clear, and it has certain reference significance for engineering practice related to underwater vehicle attitude control.

In response to the complex and time-consuming process of adjusting the center of gravity of aircraft, k-means clustering method is used to cluster the historical data of aircraft counterweight. Based on the clustering results of samples, the standard counterweight of aircraft under different samples is calculated. Then, the centroid offset of aircraft with standard counterweight is calculated through simulated assembly, and a series of statistical data are obtained. After that, the comprehensive evaluation method based on entropy weight is used to compare the results of centroid adjustment, and the optimal standard counterweight of aircraft is selected, thus simplifying the adjustment process of aircraft centroid and greatly improving the producting efficiency of aircraft.

Based on the AMSAA model, which is centered on the failure data of the same or similar products collected during the R&D stage, the principle of minimization of discrete coefficients is innovatively introduced as an optimization criterion, which is used to guide the selection of goodness-of-fit test statistics. After integrating multivariate information such as mean and variance, a new algorithm for solving the time-environmental folding coefficients is constructed, aiming at effectively folding the original failure data and then accurately estimating various parameters of the model. By solving the resulting folding coefficients, the one-sided lower confidence limits of MTBF (Mean Time Between Failure) are calculated one by one for each of the 10 different confidence settings when the product design is being molded. Example studies show that when the confidence interval is between 0.9 and 0.99, the method consistently produces better results than the existing literature regardless of the same confidence level, i.e., the accuracy of the method is significantly improved for predicting the reliability growth of aerospace products. In addition, the values of the time-environment folding coefficients solved by the improved method do not change at different confidence levels, i. e., the quantitative relationship between the environmental stresses and the real environmental stresses for each test item does not change due to the increase in confidence level, which also proves that the improved method is closer to the engineering practice from another perspective.

Vibration testing is one of the key methods for verifying the structural performance of solid rocket engines. It involves securing the test piece on the vibration table with fixtures to ensure accurate transmission of vibration loads, preventing resonance or tailing phenomena, which are the desired outcomes of vibration testing for solid rocket engines. This research focuses on a certain model solid rocket engine shell vibration testing fixture clamping methods and proposes a vibration testing fixture optimization method based on a proportionality coefficient. A simulation model of the solid rocket engine shell and the fixtures is established. Modal analysis and harmonic response analysis are carried out for the structure under different proportionality coefficients of the clamping methods. The vibration testing of the shell is conducted on a ${90}\mathrm{{kN}}$ electromagnetic vibration table. The test results indicate that a proportionality coefficient of 0.9 is the optimal clamping method for the vibration testing of the solid rocket engine shell with a slenderness ratio of 2.6, which is generally consistent with the simulation analysis results. This clamping optimization method has practical reference value for vibration testing of solid rocket engine shells.

Aiming at the characteristics of multiple hypersonic vehicles cooperative combat, a time cooperative reentry guidance scheme based on deep deterministic policy gradient and linear quadratic regulator (DDPG-LQR) is proposed. Firstly, the sequential convex programming method is used to generate the time cooperative reentry trajectory satisfying multiple constraints and its corresponding steady-state control quantity. The Radau pseudospectral method is used to discretize the motion equations to improve the discretization accuracy of trajectory optimization. Secondly, the linear quadratic regulator (LQR) is used to track the time cooperative reentry trajectory. In order to improve the cooperative guidance accuracy and guidance effect, the deep deterministic policy gradient (DDPG) is used to optimize the weight matrix coefficients of the LQR online. In the DDPG algorithm, the optimization performance of the algorithm is improved by introducing an appropriate reward function. The simulation results show that the cooperative guidance scheme proposed has better cooperative guidance effect and guidance accuracy than the traditional LQR controller in the case of initial state error and uncertainty.

Aiming at the active anti-interception game confrontation between hypersonic aircraft and accompanying defense aircraft to avoid interceptor attacks, an active defense intelligent guidance method for hypersonic aircraft is proposed based on deep reinforcement learning algorithm. In the case of insufficient maneuverability of the target aircraft, this method can achieve a higher success rate. Aiming at the sparse reward problem in the reinforcement learning training process, a reward function shaping method is proposed, which improves the convergence efficiency and training stability of the reinforcement learning algorithm. Finally, the effectiveness of the proposed method is verified by numerical simulation. The simulation results show that the proposed method can successfully achieve flight vehicle game confrontation, and has a higher game success rate than traditional game guidance methods.

When the design input is limited during the initial stage of scheme argumentation, in order to solve the problem of how to conduct control capability analysis quickly and effectively, the adaptability of traditional control capability analysis method is analyzed. A set of controllability analytical method for reentrant launch vehicles is researched by dynamic modeling and original method improving. And under the premise of limited control capability, the constraint conditions for allowable flight conditions is limited preliminary in order to quickly locate and feedback the closure of the overall unit control capability.

An adaptive sliding mode control method for spacecraft with attack angle constraints is proposed based on a direct force/aerodynamic composite control strategy for agile maneuvering control at high angles of attack. Firstly, a longitudinal direct force/aerodynamic composite control model and a lateral jet interference model are established respectively. By designing a prescribed performance nonlinear mapping function, the attitude control problem of the missile body pitch channel with attack angle constraints can be transformed into an unconstrained angle of attack error adjustment control problem. Secondly, an attack angle error-based nonlinear integral sliding mode surface is designed. Under the framework of Backstepping control, an integral Backstepping sliding mode control method for adaptive estimation of lateral jet interference is proposed, in which the upper bound of lateral jet interference can be estimated online to achieve agile and accurate control. Finally, based on Lyapunov stability theory, the asymptotic stability of the designed closed-loop control system is analyzed. Numerical simulation results demonstrate that compared to the classical sliding mode control method, the proposed method reduces steady-state time by 79.16%, overshoot by 24.68%, and energy consumption by 34.54%.

A 5B70 aluminum alloy sheet with ${1.5}\mathrm{\;{mm}}$ thickness is welded by tungsten inert gas (TIG) welding with 5B71 filler wire. The micro-structure evolution and refinement characteristics of the welded joints are investigated. The research results indicated that weld joints with excellent formation can be obtained by adopting reasonable welding parameters. The internal structure of the weld seam shows that the weld zone is mainly composed of equiaxed crystals forming a cast structure, the size of the grain structure is uneven, there are widely larger grains with a diameter of ${40}\sim {50\mu}\mathrm{m}$, as well as ultrafine grain areas with a diameter of about ${20\mu }\mathrm{m}$ which distributes in fine strips and small blocks. The area of the ultrafine grain region is obviously smaller than other areas. It mainly distributes in the direction parallel to the fusion line, with a few distributed on the weld surface. Sc and Zr were used as modificator to refine the grains. The ${\mathrm{{Al}}}_{3}\left({\mathrm{{Sc}},\mathrm{{Zr}}}\right)$ second phase particles are precipitated in the welding pool during solidification. The function of such particle is to form heterogeneous nucleation particles, reduce nucleation power and increase the number of crystal nuclei. The area where Sc elements are enriched had a higher degree of grain refinement. The “undercooling” zone is formed along the front of the solid-liquid boundary, which promotes the formation of equiaxed grains. It results in a higher degree of grain refinement, which size is only about one half of other zones.

In response to the low detectability requirements of micro radar detectors, a hybrid polarization-frequency selective rasorber (PFSR) is proposed. Firstly, based on the equivalent circuit analysis method derived from transmission line theory, the mechanism for achieving wave absorption and transmission compatibility is explored. Furthermore, by employing a bilaterally asymmetric loading approach with resistive sheet, the polarization-selective functionality of the transmission window is realized. Finally, through a hybrid design of resistive sheet, the challenge of achieving wideband absorption and transmission compatibility is addressed. Simulation results indicate that when TE waves are incident, this structure exhibits integrated functionalities with wave transmission in the frequency range of 6.8 to ${7.8}\mathrm{{GHz}}$ and low scattering across 2.2 to${18.0}\mathrm{{GHz}}$. In contrast, when TM waves are incident, it demonstrates an effective wave-absorbing capability with low scattering in the frequency range of 3.2 to 18.0 GHz. This design offers a viable solution for enhancing wideband low detectability in flight communication platforms such as satellites.

Bistatic radar is widely used in military field by virtue of its good anti-jamming ability and accurate detection and identification ability, and how to effectively jam this transceiver-split radar system has become a current research hotspot. Typical jammers have large fluctuations of bistatic RCS with angle change and weak bistatic scattering strength, which are not advantageous in countering bistatic radar. Therefore, a new type of combined jammer against bistatic radar is proposed by analyzing the bistatic scattering characteristics of four types of typical jammers. Afterwards, electromagnetic simulation calculations are carried out on the new combined jammer monomer/array of different bands, sizes and spacings to study the bistatic scattering characteristics under different parameters, and compared with typical jammers. The results show that the new combined jammer monomer/array has strong bistatic scattering strength and the fluctuation amplitude of its RCS with respect to angle is smaller, with good bistatic scattering characteristics, providing technical support for effectively jamming of bistatic radar.