To investigate the effect of inducer blade thickness on cavitation performance, the liquid oxygen turbopump of a liquid rocket engine is taken as the research object. Four inducers with different blade thicknesses are designed by changing the thickness at the blade root, and the thickness at the blade tip changes accordingly with the change in blade root thickness. Strength verification and cavitation performance analysis are conducted for the inducers of these four schemes. The research results show that selecting thinner inducers can improve the cavitation performance of turbopumps while ensuring blade strength. Meanwhile, the thickness at the blade tip also has a significant impact on the cavitation performance of the turbopump.

Aiming at the trajectory optimization problem of the ascending stage of launch vehicle in the atmosphere with complex and multi constraints, a trajectory optimization method based on simultaneous method is proposed. The method adopts the direct method under the simultaneous framework, discretizes the state variables and control variables through the finite element orthogonal collocation method, and then solves the discrete nonlinear programming problem by the interior point method, so as to balance the calculation efficiency and solution accuracy, and improve the autonomy and task adaptability of trajectory optimization. Aiming at the problem that the larger the scale of the discrete nonlinear programming problem is, the more time-consuming the gradient matrix calculation is, making full use of the sparsity of the partial derivative matrix, the solution of the non-zero term in the NLP gradient is transformed into the solution of the partial derivative of the original optimal control problem, so as to further improve the efficiency of trajectory optimization. The simulation results show that this method can complete the flight mission well and meet constraints.

Heat exchangers are extensively used in rocket power system for gas supply and distribution. Three-dimensional numerical simulations of two different heat exchangers through straight and curve tubes, respectively, are performed by commercial software FLEUNT. Comparisons are made between numerical and empirical results. The investigation indicates that the total heat transfer coefficient obtained by FLUENT using the flow-heat coupled algorithm agrees well with that from the empirical formula. Moreover, compared with heat exchanger through straight tubes, the centrifugal force exerted on the hot air in the heat exchanger through curve tubes leads to higher heat transfer efficiency. As a result, the total heat transfer coefficient of heat exchanger through curve tubes is approximately 10% greater than that through straight tubes given other flow and geometry factors fixed.

In order to achieve the purpose of precision strike of reentry vehicle under complex electromagnetic interference conditions, a side window cover throwing technology for radar/infrared dual-model combined guidance is proposed. Through simulated analysis and ground tests, the rationality of heat seal structure of infrared window and the reliability of cover throwing scheme is verified, and the motion track and flight attitude of cover are obtained under high-Mach and high dynamic pressure conditions. The results show that the heat sealing performance of infrared window is effective, which can prevent the external heat flow into the interior of the vehicle successfully. The cover can be thrown successfully when it's needed, the cover can fly out the shock wave-affected zone and always move away from the vehicle continuously, which can not crash the vehicle. The infrared glass is in good condition, which is not broken and polluted. The research provides a technical support for the investigation on cover throwing technology for reentry vehicle.

To address the issues of scattered management, lack of standardization, and traditional analysis methods in the data of liquid rocket engine tests, a big data-based liquid propulsion test data analysis system has been designed. The system adopts an advanced big data architecture, combines data preprocessing technology, distributed storage, and data center modeling, forms a specialized data warehouse, optimizes data organization, retrieval, and analysis processing capabilities, and achieves comprehensive collection, efficient storage, fine management, and intuitive display of test data. Application results show that the system not only realizes the standard management and central storage of test data, but also provides functions for data analysis such as engine adjustment calculations, significantly improving data processing efficiency and analysis quality, which provides valuable exploration and practice for the digital transformation in the field of liquid propulsion and holds promising application prospects.

In order to study the ability of laser-guided weapons to capture targets in various environments such as sea and land, mathematical models such as flight trajectory, backscatter and target diffuse reflection of laser-guided weapons are established, and whether the guided weapons could capture targets normally are judged by comparing the field of view, backscatter power density and target diffuse reflection power density of laser-guided weapons. Simulation calculations show that under the same conditions, the same laser weapon captures the target later at sea than in the land and other environments, the capture distance is closer, and the backscattering is more serious. Under normal circumstances, the backscattering effect of laser-guided weapons is more serious in the initial 4.4s time period of this projection, and the backscattering effect can be avoided by reducing the outlet energy of the laser irradiator or increasing the distance between the central axis of the laser-guided weapon and the optical path of the laser irradiator to more than 250m.

Along with the surge of radio application, electronic communication in interference environments has become increasingly important. The spectrum sensing technique matters in surmounting the frequency conflict of radio. However, the complex environment hinders the efficient feature extraction from the received spectrum signal and reduces the signal practicality. Recently, the artificial intelligence has been widespread in communication field and crucially influenced the electronic countermeasures. Consequently, based on the deep learning, this work proposes a spectrum sensing method to mix DenseNet and MLP-Mixer. Firstly, the model processes and transforms the spectrum signal data to feature images by Deepinsight Net and the generative adversarial networks renew an image. After obtaining the feature image, aspectrum sensing method integrating DenseNet and MLP-Mixer is used in order to sense the channel occupancy of primary user. Compared with the existing model through ablation experiments, the proposed method improves the detection probability of spectrum sensing better.

Taking the hydrogen-oxygen expansion cycle engine as the research object, based on the idea of modular modeling and simulation, the dynamic model of engine components is given, and the liquid rocket engine system model is constructed based on the working principle of the engine system, and the transient state of the hydrogen-oxygen expansion cycle engine is developed simulation Research. According to the simulation results and combined with the test data, the engine system model is verified and optimized, and the optimized model is simulated and calculated in the whole process of engine dynamics. The simulation results show that the main performance parameters during the dynamic change of the engine are in good agreement with the test data, which verifies the simulation model accuracy and design feasibility.

In order to improve the transpiration cooling efficiency at the stagnation point of the nose cone of the near space vehicle, a wedge-shaped porous nose cone with a gradient porosity layout is proposed and the phase change transpiration cooling is experimentally and numerically investigated under different coolant injection ratio. The experimental results indicate that the gradient porosity layout can effectively improve the cooling efficiency at the stagnation point and the overall temperature uniformity of the porous surface. When the coolant injection ratio $M$ is 0.125%, the cooling efficiency at the stagnation point is increased by 52.4%, and the overall cooling efficiency is increased by 31.7%. The numerical results indicate that the gradient porosity layout increases the coolant mass flux at the leading edge and optimizes coolant distribution by moving the maximum pressure value at the stagnation point downstream. When the coolant injection ratio $M ={0.15}\%$, the coolant mass flux at the stagnation point is increased 76%. In addition, the film formed by the coolant flows out of the porous structure is more uniform.

As a high-value military target, it is difficult to directly conduct damage research on real aircraft. Designing equivalent targets to replace real targets in damage tests and simulation research are important means for target vulnerability and damage. A target design method is proposed based on the damage characteristics and usage requirements of equivalent objects, with a focus on the "physical and functional" damage equivalent tecnology of aircraft components/subsystems under the threat of fragments. On this basis, a detailed design process for equivalent targets of aircraft is established by comprehensively considering the equivalence of the target's internal and external environment, as well as various factors such as processing and transportation. Then, based on the proposed method, an equivalent design target is carried out for the radar antenna cover of the early-warning-aircraft (EWA), and ground static explosion damage tests are carried out on the equivalent components. After verifying the accuracy of the simulation method with the test results, the ballistic limit velocity and corresponding critical penetration energy thresholds of diffrerent areas for the typical fragment hitting radar antenna cover are determined through impact finite element simulation, the rationality and usability of the proposed equivalent target design method is verifyed. The equivalent target design method proposed can provide support for the inspection and evaluation of the damage ability of air defense weapons and ammunition, the formulation of aircraft target damage standards, and joint combat training activitis.