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Effect of neutral polymeric bonding agent on tensile mechanical properties and damage evolution of NEPE propellant

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Defence technology（防务技术） 2024年第2期32卷 357-367页

作者： M.Wubuliaisan Yanqing Wu Xiao Hou Kun Yang Hongzheng Duan Xinmei Yin State Key Laboratory of Explosion Science and technology Beijing Institute of TechnologyBeijing100081PR China The Fourth Institute of China aerospace Science and technology Corporation Xi'an710025PR China School of aerospace Engineering Beijing Institute of TechnologyBeijing100081PR China Science and technology on aerospace Chemical Power Laboratory Hubei Institute of Aerospace ChemotechnologyHubei441003PR China

Introducing Neutral Polymeric bonding agents(NPBA) into the Nitrate Ester Plasticized Polyether(NEPE)propellant could improve the adhesion between filler/matrix interface, thereby contributing to the development of new generations of the NEPE propellant with better mechanical properties. Therefore,understanding the effects of NPBA on the deformation and damage evolution of the NEPE propellant is fundamental to material design and applications. This paper studies the uniaxial tensile and stress relaxation responses of the NEPE propellant with different amounts of NPBA. The damage evolution in terms of interface debonding is further investigated using a cohesive-zone model(CZM). Experimental results show that the initial modulus and strength of the NEPE propellant increase with the increasing amount of NPBA while the elongation decreases. Meanwhile, the relaxation rate slows down and a higher long-term equilibrium modulus is reached. Experimental and numerical analyses indicate that interface debonding and crack propagation along filler-matrix interface are the dominant damage mechanism for the samples with a low amount of NPBA, while damage localization and crack advancement through the matrix are predominant for the ones with a high amount of NPBA. Finally, crosslinking density tests and simulation results also show that the effect of the bonding agent is interfacial rather than due to the overall crosslinking density change of the binder.

关键词： Solid propellant Bonding agent Mechanical properties Damage evolution Cohesive-zone model Interface debonding

Coupling effect on the thermal hazard assessment of hazardous chemical materials via calorimetric technologies and simulation approaches

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Defence technology（防务技术） 2024年第2期32卷 644-654页

作者： Yabei Xu Jiankun Shao Wei Wang Shengliang Xu Dongping Chen State Key Laboratory of Explosion Science and technology Beijing Institute of TechnologyBeijing 100081China Science and technology on aerospace Chemical Power Laboratory Hubei Institute of Aerospace ChemotechnologyXiangyang 441003China

The coupling effect of heat absorption and release exists in the thermal decomposition of a few chemical ***,the impact of the above coupling on thermal hazard assessment is not considered in the literature *** this work,nitroguanidine(NQ)and 1,3,5-trinitro-1,3,5-triazine(RDX)are selected as representative materials to explore the influence of the coupling effect on the thermal hazard assessment of chemical *** linear heating experiments of NQ and RDX are carried out by a microcalorimeter and synchronous thermal *** thermal decomposition curves are decoupled by advanced thermokinetics *** thermal decomposition and kinetic parameters before and after decoupling are *** results of TG experiment show that both NQ and RDX began to lose mass during the endothermic *** endothermic melting and exothermic decomposition of NQ and RDX are coupled within this *** coupling effect has different degrees of influence on its initial decomposition temperature and safety *** with the parameters in the coupling state,the initial decomposition temperature and adiabatic induction period after decoupling *** self-accelerating decomposition temperature increases,and internal thermal runaway time *** the thermal hazard assessment of chemical materials with coupling effects,the calculated parameters after decoupling should be taken as an important safety index。

关键词： Calorimetric technologies Kinetics Thermal hazard Phase transformation Thermal decomposition

Multidisciplinary design optimization of a dual-spin guided vehicle

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Defence technology（防务技术） 2024年第7期37卷 133-148页

作者： Jalal Karimi Mohammad Reza Rajabi Seyed Hossein Sadati Seyed Mahid Hosseini Department of aerospace Engineering Malek Ashtar University of TechnologyTehranIran

In this research,a Multidisciplinary Design Optimization approach is proposed for the dual-spin guided flying projectile design considering external and internal parts of the body as design *** this way,a parametric formulation is *** related disciplines,including structure,aerodynamics,guidance,and control are *** total mass,maximum aerodynamic control effectiveness,minimum miss distance,maximum yield stress in all subsystems,controllability and gyroscopic stability constraints are some of objectives/constraints taken into *** problem is formulated in All-At-Ones Multidisciplinary Design Optimization approach structure and solved by Simulated Annealing and minimax *** optimal configurations are evaluated in various *** resulted optimal configurations have met all design objectives and constraints.

关键词： Flying projectile optimal design All-at-ones multidisciplinary optimization Structure discipline Guidance and control discipline Aerodynamic discipline

Full lifetime demonstration of a Micro-Cathode-Arc thruster evolution characteristics

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Chinese Journal of Aeronautics 2024年第6期37卷 38-49页

作者： Zhe ZHANG Zijing ZHAO Xiangyang LIU Ningfei WANG School of aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

Ground lifetime test is the most crucial experiment to assess the performance,*** flight qualification of electric propulsion,and it can bring new insights for understanding the operation *** work demonstrates a full lifetime test of 140000 cycles on a Micro-Cathode-Arc Thruster(μCAT)with 160μs charging time and 86 mJ charging energy.A four-probe resistivity measurement method is utilized to investigate variations in the conductive film thickness and resistivity throughout the thruster *** film parameters show that the lifetime of theμCAT can be divided into three *** the initial stage,the film thickness decreases by 1.2μm and the resistivity increases significantly due to the high discharge intensity and intense film ablation;In the steady stage,the change of the film thickness is within 5%,and the resistivity of the film increases slowly from 0.050Ω·mm to 0.223Ω·*** the end stage,the resistivity exponentially increases from 0.223Ω·mm to 1.176Ω·mm,with the increase accounting for 81%,ultimately resulting in the failure of the thruster open ***,the evolution of discharge parameters,and the variation of plume parameters are measured throughout the *** discharge characteristics also show significant differences in the duration of voltage and current in these three *** results of plume shape and plasma parameters are also well con-sistent with the discharge parameters and film *** results suggest that,for evaluating the steady stage lifetime of thrusters,the film thickness is the best indicator compared to the variations in resistivity and voltage-current *** the end stage,the plasma plume *** duration,and plume parameters can conveniently and clearly characterize the thruster failures and irregularity.

关键词： Electric propulsion Lifetimetest Micro-Cathode-ArcThruster(uCAT) Conductive film Dischargecharacteristics Plasma parameters

Initial costates derived by near-optimal reference sequence and least-squares method

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Chinese Journal of Aeronautics 2024年第5期37卷 377-391页

作者： Shaozhao LU Yao ZHANG Quan HU School of aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

In this paper,we present a novel initial costates solver for initializing time-optimal trajectory problems in relative motion with continuous low *** proposed solver consists of two primary components:training a Multilayer Perceptron(MLP)for generating reference sequence and Time of Flight(TOF)to the target,and deriving a system of linear algebraic equations for obtaining the initial *** overcome the challenge of generating training samples for the MLP,the backward generation method is proposed to obtain five different training *** training database and sample form are determined by analyzing the input and output correlation using the Pearson correlation *** best-performing MLP is obtained by analyzing the training results with various hyper-parameter combinations.A reference sequence starting from the initial states is obtained by integrating forward with the near-optimal control vector from the output of ***,a system of linear algebraic equations for estimating the initial costates is derived using the reference sequence and the necessary conditions for *** results demonstrate that the proposed initial costates solver improves the convergence ratio and reduce the function calls of the shooting ***,Monte-Carlo simulation illustrates that the initial costates solver is applicable to different initial velocities,demonstrating excellent generalization ability.

关键词： Relative motion Expanding training database Multilayer perceptron Initial costates Least-squares method

Characteristics of the electromagnetic wave propagation in magnetized plasma sheath and practical method for blackout mitigation

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Chinese Physics B 2024年第5期33卷 489-499页

作者：吴翔张珈珲董果香石磊 School of aerospace Science and technology Xidian UniversityXi'an 710071China

“Magnetic window”is considered as an effective method to solve the communication blackout *** software package based on the finite element method is utilized to simulate the propagation of right-handed circularly polarized wave in the magnetized plasma *** assume a double Gaussian model of electron density and an exponential attenuation model of magnetic *** propagation characteristics of right-handed circularly polarized wave are analyzed by the observation of the reflected,transmitted and loss *** numerical results show that the propagation of right-handed circularly polarized wave in the magnetized plasma sheath varies for different incident angles,collision frequencies,non-uniform magnetic fields and non-uniform plasma *** notice that reducing the wave frequency can meet the propagation conditions of whistle mode in the weak magnetized plasma *** the transmittance of whistle mode is less affected by the variation of the electron density and the collision *** can be used as a communication window.

关键词： magnetized plasma sheath communication blackout finite element incident angle whistler wave

A unified intelligent control strategy synthesizing multi-constrained guidance and avoidance penetration

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Science China(Information Sciences) 2024年第7期67卷 329-330页

作者： Sibo ZHAO Jianwen ZHU Weimin BAO Xiaoping LI School of aerospace Science and technology Xidian University College of Missile Engineering Rocket Force University of Engineering China aerospace Science and technology Corporation

Satisfying various terminal constraints and achieving evasive flight in no-flying-zones (NFZs) are two important flight missions undertaken by high velocity vehicles. We studied an intelligent maneuvering guidance strategy using deep reinforcement learning (DRL) methods to achieve the coordination and unification of evasive flight and multi-constrained guidance with minimal energy loss.

关键词： Energy dissipation

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A novel evasion guidance for hypersonic morphing vehicle via intelligent maneuver strategy

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Chinese Journal of Aeronautics 2024年第5期37卷 441-461页

作者： Xun LI Xiaogang WANG Hongyu ZHOU Yu LI Department of Aerodynamics Harbin Institute of TechnologyHarbin 150001China Beijing aerospace technology Institute Beijing 100074China

This paper presents a novel evasion guidance law for hypersonic morphing vehicles,focusing on determining the optimized wing's unfolded angle to promote maneuverability based on an intelligent ***,the pursuit-evasion problem is modeled as a Markov decision *** the agent's action consists of maneuver overload and the unfolded angle of wings,which is different from the conventional evasion guidance designed for fixed-shape *** reward function is formulated to ensure that the miss distances satisfy the prescribed bounds while minimizing energy ***,to maximize the expected cumulative reward,a residual learning method is proposed based on proximal policy optimization,which integrates the optimal evasion for linear cases as the baseline and trains to optimize the performance for nonlinear engagement with multiple ***,offline training guarantees improvement of the constructed evasion guidance law over conventional ***,the guidance law for online implementation includes only analytical *** maps from the confrontation state to the expected angle of attack and the unfolded angle while retaining high computational *** show that the proposed evasion guidance law can utilize the change of unfolded angle to extend the maximum overload *** it surpasses conventional maneuver strategies by ensuring better evasion efficacy and higher energy efficiency.

关键词： Hypersonic vehicles Variable-sweep wings Evasion guidance Reinforcement learning Pursuit-evasion problem

Effect of kerosene injection states on mixing and combustion characteristics in a cavity-based supersonic combustor

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Chinese Journal of Aeronautics 2024年第4期37卷 308-320页

作者： Xu LIU Peibo LI Fei LI Hongbo WANG Mingbo SUN Chao WANG Yixin YANG Dapeng XIONG Yanan WANG Science and technology on Scramjet Laboratory College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410073China

It has been found that the static pressure distribution along the axial direction of liquid kerosene is lower than that of the gaseous kerosene under the same flow condition and overall equivalent ratio from previous *** further investigate this phenomenon,a compressible two-phase parallel simulation method is utilized to analyze the mixing and combustion characteristics of gaseous and liquid kerosene jets in a cavity-based supersonic *** numerical results are consistent with the experiments and demonstrate that gaseous injection leads to a cavity shear layer that dives deeper into the cavity,forming two recirculation zones in the front and rear of the *** contrast,the cavity shear layer is closer to the mainstream during liquid injection,and only a large recirculation zone is formed in the rear of the *** a result of the cavity shear layer and the recirculating flow,the fuel vapor of gaseous injection accumulates in the front of the cavity,while for the liquid injection,the fuel vapor disperses in the cavity,cavity shear layer,and the region above,and the rear of the cavity has a higher fuel vapor concentration than the *** unique fuel distribution causes the combustion area to be concentrated in the cavity during the gaseous injection but dispersed inside and downstream of the cavity during the liquid *** a result,forming a thermal throat under the same conditions is more challenging during liquid injection,and the generated static pressure distribution is lower than that during the gaseous injection.

关键词： Gaseous injection Liquid injection Mixing process Combustion Supersonic flow