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Modelling the effect of deposited grid material on the power coupling of radio frequency ion thrusters

Journal of Electric Propulsion 2025年第1期4卷 1-27页

作者： Cui, Yunwei Ren, Junxue Wu, Kunlong Chen, Nanyi Pan, Ruojian Mao, Renfan Tang, Haibin School of Space and Environment Beihang University Shahe Higher Education Park Beijing102206 China School of Astronautics Beihang University Shahe Higher Education Park Beijing 102206 People’s Republic of China Beijing102206 China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies of the Ministry of Education Beijing102206 China Laboratory of Space Environment Monitoring and Information Processing Ministry of Industry and Information Technology Beijing102206 China

For radio-frequency(RF) ion thrusters, under nominal operating conditions, sputtering of the screen grid can lead to the formation of a conductive film of the grid material on the inner walls of the discharge chamber which leads to a decrease in RF coupling to the plasma. When the ion beam becomes unfocused, either due to off nominal operating conditions or as a result of lifetime degradation, this process can be accelerated. An RF ion thruster performance model is developed, which can quantitatively simulate the performance degradation caused by sputter deposition on the thruster. This model couples an RF power transmission model, a zero-dimensional thruster discharge chamber model, and a sputter deposition model. An experiment that intentionally enhances the erosion of the accelerator grid to accelerate the formation of the conductive film confirms the power transmission process described by the model. As a result, the deposition on the discharge chamber walls primarily originates from the sputtering of the accelerator grid by the ion beam. At a xenon flow rate of 0.63 sccm and RF power of 42 W, a 2.015 μm copper film deposited on the walls resulting in a decrease in thruster screen grid current. The simulated results indicate that the power absorbed by the plasma decreases after deposition, which is the primary cause of the screen grid current reduction. Using materials with low conductivity for the deposition layer in the construction of the accelerator grids can reduce the impact of the deposition layer on the thruster screen grid current. © The Author(s) 2025.

关键词： Conductive films

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Numerical analysis of hydrogen peroxide injection effect on the combustion characteristics of a staged combustion aft-injected hybrid rocket motor

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Acta Astronautica 2025年 234卷 429-444页

作者： Luojun Deng Li Ping Changrui Chen Weizong Wang Guangchuan Zhang Yuxin Yang School of Astronautics Beihang University Beijing 100191 China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Beijing 100191 China The Institute of Xi'an Aerospace Solid Propulsion Technology Xi'an 710025 China National Key Laboratory of Solid Rocket Propulsion Xi'an 710025 China

The staged combustion aft-injected hybrid rocket motor is a novel propulsion system that utilizes an independent fuel-rich solid propellant gas generator, with high performance and promising application prospects. However, its performance is significantly influenced by the hydrogen peroxide injection scheme. Therefore, a three-dimensional numerical model based on the Euler-Lagrange framework for multiphase turbulent flow and combustion is established. Based on the validated model, the detailed flow and combustion characteristics are carefully discussed. It is found that the combustion flow field exhibits distinct partition characteristics. And the recirculation zones appearing in the motor head enhance mixing combustion. Then, the effects of axial injection angles and axial/swirl injection ratios on the combustion flow field and motor performance are investigated. The results indicate that the larger the axial injection angle, the deeper and earlier the mixing of hydrogen peroxide and primary combustion gas occurs, thereby enhancing the combustion efficiency and specific impulse. To achieve better motor performance, the axial injection angle should not be less than 30°. Additionally, a smaller axial/swirl injection ratio leads to more droplets accumulating near the wall, resulting in incomplete mixing evaporation and hence motor performance loss. However, this also significantly decreases the temperature near the motor head and wall, which positively impacts the motor's thermal protection. This study suggests that the axial/swirl injection ratio should be controlled around 4:1, as the specific impulse decreases by only 2.3 %. This paper provides valuable guidance for the design of injection schemes for the staged combustion aft-injected hybrid rocket motor.

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Efficient Semantic Splatting for Remote Sensing Multiview Segmentation

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IEEE Transactions on Geoscience and Remote Sensing 2025年 63卷

作者： Qi, Zipeng Chen, Hao Zhang, Haotian Zou, Zhengxia Shi, Zhenwei Beihang University School of Astronautics State Key Laboratory of Virtual Reality Technology and Systems Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Ministry of Education Department of Aerospace Intelligent Science and Technology Beijing100191 China Shanghai Artificial Intelligence Laboratory Shanghai200232 China

Remote sensing multiview image segmentation is essential for achieving accurate and consistent stereoscopic perception of target scenes. This task involves processing RGB images from multiple viewpoints to generate high-accuracy, view-consistent semantic segmentation across all views. Traditional training-based methods struggle with maintaining cross-view consistency, while optimization-driven approaches using implicit neural networks improve view consistency but suffer from slow parameter optimization and inference. To overcome these limitations, we propose a novel Gaussian splatting-based semantic segmentation framework. Our method efficiently projects the color attributes and semantic features of 3-D Gaussians onto the image plane, enabling the simultaneous generation of both RGB images and segmentation outputs. By leveraging explicit spatial structures and a splatting rendering strategy, our approach significantly enhances optimization efficiency and rendering speed. In addition, we incorporate SAM2 to generate pseudo-labels for boundary regions, addressing the lack of supervision in sparsely labeled views (e.g., 3%). To further enforce cross-view consistency and feature coherence of 3-D Gaussians, we introduce a two-level aggregation loss that operates at both the 2-D feature map and 3-D spatial levels. Extensive experiments across nine datasets demonstrate the superiority of our method, achieving competitive segmentation quality with limited supervisory views. Notably, our approach reduces rendering (inference) times by 90%, while improving the average mean intersection over union (mIoU) by up to 3.5%. © 1980-2012 IEEE.

关键词： Semantic Segmentation

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Text2Earth: Unlocking Text-driven Remote Sensing Image Generation with a Global-Scale Dataset and a Foundation Model

arXiv

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arXiv 2025年

作者： Liu, Chenyang Chen, keyan Zhao, Rui Zou, Zhengxia Shi, Zhenwei The Department of Aerospace Intelligent Science and Technology School of Astronautics The State Key Laboratory of Virtual Reality Technology and Systems Beihang University Beijing100191 China The Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Ministry of Education China Shanghai Artificial Intelligence Laboratory Shanghai200232 China Shen Yuan Honors College of Beihang University Beijing100191 China The Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore

Recently, generative foundation models have significantly advanced large-scale text-driven natural image generation and have become a prominent research trend across various vertical domains. However, in the remote sensing field, there is still a lack of research on large-scale text-to-image (text2image) generation technology. Existing remote sensing image-text datasets are small in scale and confined to specific geographic areas and scene types. Besides, existing text2image methods have struggled to achieve global-scale, multi-resolution controllable, and unbounded image generation. To address these challenges, this paper presents two key contributions: the Git-10M dataset and the Text2Earth foundation model. Git-10M is a global-scale image-text dataset comprising 10.5 million image-text pairs, 5 times larger than the previous largest one. The dataset contains essential resolution information and covers a wide range of geographic scenes and contains essential geospatial metadata, significantly surpassing existing datasets in both size and diversity. Building on Git-10M, we propose Text2Earth, a 1.3 billion parameter generative foundation model based on the diffusion framework to model global-scale remote sensing scenes. Text2Earth integrates a resolution guidance mechanism, enabling users to specify image resolutions. A dynamic condition adaptation strategy is proposed for training and inference to improve image generation quality. Text2Earth not only excels in zero-shot text2image generation but also demonstrates robust generalization and flexibility across multiple tasks, including unbounded scene construction, image editing, and cross-modal image generation. This robust capability surpasses previous models restricted to the basic fixed size and limited scene types. On the previous text2image benchmark dataset, Text2Earth outperfoms previous models with a significant improvement of +26.23 FID and +20.95% Zero-shot Cls-OA metric. Our project page is https://chen-y

关键词： Optical remote sensing

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Model-free adaptive optimal design for trajectory tracking control of rocket-powered vehicle

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Chinese Journal of Aeronautics 2020年第6期33卷 1703-1716页

作者： Wenming NIE Huifeng LI Ran ZHANG School of Astronautics Beihang UniversityBeijing 100083China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Ministry of EducationBeijing 100083China

An adaptive optimal trajectory tracking controller is presented for the Solid-RocketPowered Vehicle(SRPV)with uncertain nonlinear non-affine dynamics in the framework of adaptive dynamic ***,considering that the ascent model of the SRPV is non-affine,a model-free Single Network Adaptive Critic(SNAC)method is developed based on the dynamic neural network and the traditional SNAC *** developed model-free SNAC method overcomes the limitation of the traditional SNAC method that can only be applied to affine ***,a closed-form adaptive optimal controller is designed for the non-affine dynamics of *** controller can adjust its parameters under different flight conditions and converge to the approximate optimal controller through online ***,the convergence to the approximate optimal controller is *** theoretical analysis of the uniformly ultimate boundedness of the tracking error is also *** results demonstrate the effectiveness of the proposed controller.

关键词： Adaptive dynamic programming dynamic neural network Model-free Solid-rocket-powered vehicle Trajectory tracking

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Numerical and experimental research on axial injection end-burning hybrid rocket motors with polyethylene fuel

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Chinese Journal of Aeronautics 2024年第8期37卷 91-105页

作者： Xiangyu MENG Hui TIAN Lingfei HE Jingfei GAO Xiaoting NIU Guobiao CAI School of Astronautics Beihang UniversityBeijing 100191China Key Laboratory of Spacecraft Design Optimization&Dynamic Simulation Technologies Ministry of EducationBeijing 100816China

This study investigates the end-burning hybrid rocket motors with polyethylene fuel by the numerical simulation and *** on computational fluid dynamics,a numerical model is *** model is validated by two firing tests in this hybrid rocket motor,which uses oxygen and polyethylene as *** results show that the numerical and experimental data are in good agreement,and the error of the chamber pressure is less than 2.63%.Based on the simulation mode,the blowoff limit of the end-burning hybrid rocket motors is *** the nozzle throat diameter and the inner diameter of grain are large,it is more difficult for the hybrid rocket motor to achieve end-burning mode,i.e.,the flame spreading is prevented in the narrow *** main reason is that when the nozzle throat and the grain port are large,chamber pressure and oxidizer flow velocity are ***,the friction velocity considering the pressure and flow velocity is *** critical friction velocity is about 4.054–4.890 m/s in the hybrid rocket *** the friction velocity exceeds the critical friction velocity,the combustion mode in hybrid rocket motors changes from the flame spreading mode to the end-burning ***,the regression rate formula is obtained by fitting,which shows that the regression rate has a good correlation with combustion chamber *** critical friction velocity and regression rate formula can provide an important reference for end-burning hybrid rocket motors.

关键词： Hybrid rocket motor End burning Blowoff limit Flame propagation Regression rate

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A comprehensive fluid-solid coupling dynamic simulation for spatiotemporal distribution of regression rate in hybrid rocket motors

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Chinese Journal of Aeronautics 2024年第9期37卷 100-112页

作者： Tianfang WEI Guobiao CAI Hui TIAN Xiangyu MENG Xianzhu JIANG Xiaoming GU School of Astronautics Beihang UniversityBeijing 100191China Key Laboratory of Spacecraft Design Optimization&Dynamic Simulation Technologies Ministry of Education Beijing 100191China

The spatiotemporal distribution characteristics of the regression rate are crucial aspects of the research on Hybrid Rocket Motor(HRM). This study presents a pioneering effort in achieving a comprehensive numerical simulation of fluid dynamics and heat transfer in both the fluid and solid regions throughout the entire operation of an HRM. To accomplish this, a dynamic grid technique that incorporates fluid–solid coupling is utilized. To validate the precision of the numerical simulations, a firing test is conducted, with embedded thermocouple probes being used to measure the inner temperature of the fuel grain. The temperature variations in the solid fuel obtained from both experiment and simulations show good agreement. The maximum combustion temperature and average thrust obtained from the simulations are found to deviate from the experimental results by only 3.3% and 2.4%, respectively. Thus, it can be demonstrated that transient numerical simulations accurately capture the fluid–solid coupling characteristics and transient regression rate. The dynamic simulation results of inner flow field and solid region throughout the entire working stage reveal that the presence of vortices enhances the blending of combustion gases and improves the regression rate at both the front and rear ends of the fuel grain. In addition, oscillations of the regression rate obtained in the simulation can also be well corresponded with the corrugated surface observed in the experiment. Furthermore, the zero-dimension regression rate formula and the formula describing the axial location dependence of the regression rate are fitted from the simulation results, with the corresponding coefficients of determination(R^(2)) of 0.9765 and 0.9298, *** research serves as a reference for predicting the performance of HRM with gas oxygen and polyethylene, and presents a credible way for investigating the spatiotemporal distribution of the regression rate.

关键词： Hybrid Rocket Motor(HRM) Transient numerical simulation Fluid-solid couplingheat transfer Spatiotemporal distribution of regression rate dynamic grid

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Index allocation for a reusable LOX/CH4 rocket engine

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Chinese Journal of Aeronautics 2021年第2期34卷 432-440页

作者： Yi LI Jie FANG Bing SUN Kaiyang LI Guobiao CAI School of Astronautics Beihang UniversityBeijing 100083China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies(Beihang University) Ministry of EducationBeijing 100083China

Reusable rocket engines are the core components of reusable launch vehicles, and have thus become a major focus of aerospace engineering research in recent years. In practice, subsystem design is based on the overall index allocation of an engine;therefore, a multidisciplinary optimization approach is necessary. In this study, design of a reusable methane/liquid oxygen(LOX/CH4)rocket engine with a gas generator cycle was investigated using multidisciplinary optimization. Two parameters were chosen as design variables: pressure and fuel mix ratio of the main combustion chamber. optimization objectives were specific impulse, structural mass, and life cycle cost of the reusable rocket engine, and constraints were assigned to each discipline according to rocket design requirements. Then, an optimization model was developed, and optimal design parameters were acquired for the LOX/CH4 rocket engine. The proposed method is effective for designing the index allocation of reusable rocket engines and takes into account the multidisciplinary nature of complex systems.

关键词： Index allocation Mass model Multidisciplinary optimization Reliability Rocket engines

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Multi-disciplinary design optimization with fuzzy uncertainties and its application in hybrid rocket motor powered launch vehicle

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Chinese Journal of Aeronautics 2020年第5期33卷 1454-1467页

作者： Pengcheng WANG Hui TIAN Hao ZHU Guobiao CAI School of Astronautics Beihang UniversityBeijing 100083China Key Laboratory of Spacecraft Design Optimization&Dynamic Simulation Technologies of Ministry of Education Beihang UniversityBeijing 100083China

In this paper,an Uncertainty-based Multi-disciplinary design optimization (UMDO)method combining with fuzzy theory and Multi-Discipline Feasible (MDF) method is developed for the conceptual design of a Hybrid Rocket Motor (HRM) powered Launch Vehicle (LV).In the method proposed,membership functions are used to represent the uncertain factors,the fuzzy statistical experiment is introduced to analyze the propagation of uncertainties,and means,standard deviations and credibility measures are used to delineate uncertain responses.A geometric programming problem is solved to verify the feasibility of the Fuzzy-based Multi-Discipline Feasible(F-MDF) method.A multi-disciplinary analysis of a three-stage HRM powered LV involving the disciplines of propulsion,structure,aerodynamics and trajectory is implemented,and the mathematical models corresponding to the F-MDF method and the MDF method are established.A two-phase optimization method is proposed for multi-disciplinary design optimization of the LV,including the orbital capacity optimization phase based on the Ziolkowski formula,and the scheme trajectory verification phase based on the 3-degree-of-freedom point trajectory *** correlation coefficients and the quadratic Response Surface Method (RSM) based on Latin Hypercube Sampling (LHS) are adopted for sensitive analysis of uncertain factors,and the Multi-Island Genetic Algorithm (MIGA) is adopted as the optimization *** results show that the F-MDF method is applicable in LV conceptual design,and the design with the F-MDF method is more reliable and robust than that with the MDF method.

关键词： Fuzzy theory Hybrid Rocket Motor(HRM) Launch Vehicle(LV) Sensitive Analysis(SA) Uncertainty-based Multi-disciplinary design optimization(UMDO)

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Three-dimensional numerical analysis on combustion performance and flow of hybrid rocket motor with multi-segmented grain

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Chinese Journal of Aeronautics 2020年第4期33卷 1181-1191页

作者： Hui TIAN Yu DUAN Hao ZHU School of Astronautics Beihang UniversityBeijing 100083China Key Laboratory of Spacecraft Design Optimization&Dynamic Simulation Technologies Ministry of EducationBeihang UniversityBeijing 100083China

This paper presents the combustion characteristics in hybrid rocket motors with multisegmented grain through three-dimensional numerical ***-segmented grain is composed of several thin grains with two or more *** numerical model consists of Navier-Stokes equations with turbulence,solid fuel pyrolysis,chemical reactions,a fluid–solid coupling model and a regression rate *** simulations adopt 90%Hydrogen Peroxide(HP)and PolyEthylene(PE)as the propellant *** effects of the rotation,port number,fuel grain segment number and mid-chamber length on the flow field and combustion performances are *** results indicate that the multi-segmented grain configuration can strengthen the flow field,and the regression rate and combustion efficiency are *** the cases with two grain segments and three ports for example,the regression rate is increased by 32.4%-45.1%and the combustion efficiency increases by 6%-8.6%in different rotation angles.

关键词： Combustion efficiency Hybrid rocket motor Multi-segmented grain Regression rate Rotation angle

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