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22 pages, 7116 KiB

Open AccessArticle

LEO Satellite Navigation Based on Optical Measurements of a Cooperative Constellation

by Pei Chen, Xuejian Mao and Siyu Chen

Aerospace 2023, 10(5), 431; https://doi.org/10.3390/aerospace10050431 - 3 May 2023

Viewed by 2005

Abstract

Autonomous, anti-jamming, and high-precision satellite navigation are of great importance to current and future space technologies. This paper proposes a cooperative constellation navigation system for low Earth orbit (LEO) satellites that use only the optical measurements of cooperative satellites. Based on photometry, an [...] Read more.

Autonomous, anti-jamming, and high-precision satellite navigation are of great importance to current and future space technologies. This paper proposes a cooperative constellation navigation system for low Earth orbit (LEO) satellites that use only the optical measurements of cooperative satellites. Based on photometry, an optical transmission link model of the system is built. With the pixel coordinates of the cooperative satellites on the optical images, the line of sight (LoS) vectors of the cooperative satellites with respect to the LEO spacecraft are first calculated, and a single-point positioning method based on the LoS vectors’ inner products is proposed. The single-point positioning results are then fed into a least square batch filter to estimate a high-precision spacecraft orbit. Simulations are conducted to evaluate the potential navigation accuracy. With a cooperative satellite ephemeris error of 100 m and an optical measurement noise level of 5 arcsecs, position accuracies of single-point positioning and dynamic orbit determination in the order of hundreds of meters and eight meters, respectively, are realized. In addition, the influences of the orbital altitude of the cooperative constellation, the ephemeris error of the cooperative satellite, the noise level of the optical measurements, and the Earth’s gravitational model on navigation accuracy are investigated via comparative simulations. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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19 pages, 6642 KiB

Open AccessArticle

Retrieval of the Stratospheric Density by the Star Occultation

by Kedong Wang, Zhennan Li and Shaoxiong Zhang

Aerospace 2023, 10(3), 313; https://doi.org/10.3390/aerospace10030313 - 22 Mar 2023

Viewed by 1509

Abstract

The navigation by the stellar refraction is important for a LEO (Low-Earth-Orbit) satellite, especially in a GNSS (Global Navigation Satellite System)-denied environment, since it is totally autonomous. However, the biggest barrier to the accurate navigation by the stellar refraction lies in the accurate [...] Read more.

The navigation by the stellar refraction is important for a LEO (Low-Earth-Orbit) satellite, especially in a GNSS (Global Navigation Satellite System)-denied environment, since it is totally autonomous. However, the biggest barrier to the accurate navigation by the stellar refraction lies in the accurate stratospheric density. Therefore, the retrieval of the stratospheric density by the star occultation is proposed in this paper to acquire the stratospheric density globally with the high accuracy. Compared with the retrieval of the stratospheric density by the GPS (Global Positioning System) radio occultation, the retrieval by the star occultation can achieve a high vertical resolution. The retrieval of the stratospheric density by the star occultation is first derived in principle. Then, the performance of the retrieval, including the spatial resolution, the atmospheric attenuation, and the accuracy, was investigated in detail. The performance of the retrieval was also comprehensively verified by simulations. The simulation results prove that the retrieval of the stratospheric density by the star occultation can achieve a similar accuracy to that by the GPS radio occultation, but it has a higher vertical resolution than that by the GPS radio occultation, which is good for improving the accuracy of the navigation by the stellar refraction. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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21 pages, 2374 KiB

Open AccessArticle

The Low Fuel Consumption Keeping Method of Eccentricity under Integrated Keeping of Inclination-Longitude

by Lijun Ye, Chunyang Liu, Fucheng Liu, Wenzheng Zhang and Hexi Baoyin

Aerospace 2023, 10(2), 135; https://doi.org/10.3390/aerospace10020135 - 31 Jan 2023

Cited by 1 | Viewed by 1631

Abstract

The influence of the natural perturbation force will cause the eccentricity of the GEO satellite to produce a periodic motion with a period of years, and then cause the east–west station of the GEO satellite to oscillate. From the perspective of the best [...] Read more.

The influence of the natural perturbation force will cause the eccentricity of the GEO satellite to produce a periodic motion with a period of years, and then cause the east–west station of the GEO satellite to oscillate. From the perspective of the best fuel-saving or the failure of the thruster used for station keeping, some scholars have proposed a method of slightly deflecting the thrust used for north–south station keeping (NSSK) to the east or west to achieve the integrated keeping of inclination and longitude. The disadvantage of this strategy is that the eccentricity cannot be maintained, and even causes the continuous divergence of the eccentricity. Based on the above problems, this paper proposes a low fuel consumption keeping method for eccentricity under the integrated maintenance of inclination and longitude. Assuming that the satellite is only equipped with a south (north) direction thruster for station keeping, on the premise of not affecting the satellite’s Earth observation, the satellite’s forward flight and backward flight are switched every year at the spring equinox and autumn equinox, which can prevent the eccentricity divergence when performing mean longitude keeping. When the accuracy of the east–west station keeping is not pursued, this method can not only effectively save the fuel consumption of the station keeping, but also greatly reduce the number of eccentricity maintenance interventions and the interference to the whole satellite due to the eccentricity keeping, which has a certain engineering application value. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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14 pages, 3957 KiB

Open AccessArticle

Life Cycle Assessment of the Cellulosic Jet Fuel Derived from Agriculture Residue

by Ziyu Liu, Haobo Liu and Xiaoyi Yang

Aerospace 2023, 10(2), 129; https://doi.org/10.3390/aerospace10020129 - 31 Jan 2023

Cited by 7 | Viewed by 2475

Abstract

The purpose of this paper is to discover the impacts of contradictory factors in the application of agricultural residue with sustainable biofuel benefits. Based on the Life cycle assessment (LCA) approach, the quantitative LCA assessment model and approach have been established, coupling upstream [...] Read more.

The purpose of this paper is to discover the impacts of contradictory factors in the application of agricultural residue with sustainable biofuel benefits. Based on the Life cycle assessment (LCA) approach, the quantitative LCA assessment model and approach have been established, coupling upstream cultivation and downstream jet biofuel product, which would benefit agriculture residue choice. The LCA model investigated the effects of interaction factors on energy consumption, including land release and agriculture residue use change. The computational framework of the LCA model is classified into three sub-models, including the cultivation and harvesting model, the refining process and distribution model, and the flight model. According to uncertainty analysis by the LCA model, the positive energy gains have been conducted at a wide range of hydrogen production and methanol production. The application model is represented by six types of typical aircraft widely used in China, including the LTO cycle module, actual cruising distance and maximum cruising distance module, actual payload, and maximum payload module. In the whole life cycle assessment, GHGs of agriculture residue is 17.9 gCO₂e/MJ while petroleum-based jet fuel is 90.2 gCO₂e/MJ. The order of GHGs in WTW (well to wheel) is agriculture residue < corn stover < beanstalk < wheat straw < rice straw. The land release conducted obviously to the total GHGs emission for rice straw, which indicated that land release should involve in the LCA. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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28 pages, 9015 KiB

Open AccessArticle

The Influence of Thrust Chamber Structure Parameters on Regenerative Cooling Effect with Hydrogen Peroxide as Coolant in Liquid Rocket Engines

by Chuang Zhou, Nanjia Yu, Shuwen Wang, Shutao Han, Haojie Gong, Guobiao Cai and Jue Wang

Aerospace 2023, 10(1), 65; https://doi.org/10.3390/aerospace10010065 - 9 Jan 2023

Cited by 5 | Viewed by 6456

Abstract

Liquid rocket engines with hydrogen peroxide and kerosene have the advantages of high density specific impulse, high reliability, and no ignition system. At present, the cooling problem of hydrogen peroxide engines, especially with regenerative cooling, has been little explored. In this study, a [...] Read more.

Liquid rocket engines with hydrogen peroxide and kerosene have the advantages of high density specific impulse, high reliability, and no ignition system. At present, the cooling problem of hydrogen peroxide engines, especially with regenerative cooling, has been little explored. In this study, a realizable k-epsilon turbulence model, discrete phase model, eddy dissipation concept model, and 10-step 10-component reaction mechanism of kerosene with oxygen are used. The increased rib height of the regenerative cooling channel causes the inner wall temperature of the engine increases, the average temperature of the coolant outlet decreases slightly, and the coolant pressure decreases. The overall wall temperature decreases as the rib width of the regenerative cooling channel increases. However, in the nozzle throat area, the wall temperature increases, the average coolant outlet temperature decreases, and the coolant pressure drop increases. A decrease in the inner wall thickness of the regenerative cooling channel results in a significant decrease in the wall temperature and a small increase in the average coolant outlet temperature. These findings contribute to the further development of the engine with hydrogen peroxide and can guide the design of its regenerative cooling process. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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12 pages, 1587 KiB

Open AccessArticle

Experimental Study of Suppressing the Thermoacoustic Instabilities in a Rijke Tube Using Microsecond Discharge Plasma

by Jiangge Deng, Ting Li, Jinkui Wang and Chicheng Gao

Aerospace 2022, 9(12), 836; https://doi.org/10.3390/aerospace9120836 - 16 Dec 2022

Cited by 3 | Viewed by 1782

Abstract

Thermoacoustic instabilities occur when heat release is coupled with pressure fluctuation, which may cause performance degradation of the combustor and serious structural damage. This study focued on an active control method using discharge plasma and showed experimentally that discharge plasma can make a [...] Read more.

Thermoacoustic instabilities occur when heat release is coupled with pressure fluctuation, which may cause performance degradation of the combustor and serious structural damage. This study focued on an active control method using discharge plasma and showed experimentally that discharge plasma can make a difference in controlling the thermoacoustic instabilities in a Rijke tube. A vertically placed Rijke tube thermoacoustic system using induction heating tungsten mesh as a heat source was built. The results show that the high repetition rate discharge can effectively suppress the thermoacoustic oscillations in the Rijke tube and that they will not re-occur for some time. Additionally, their effectiveness depended more on average power than energy per pulse. Combining the collected pressure, schlieren data, and theoretical analysis, it can be suggested that the plasma discharge could heat the inlet airflow, which could influence the heat exchange and then could break thermo-acoustic coupling, and its high-frequency pressure perturbation might increase the dissipation of the energy of sound. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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19 pages, 9399 KiB

Open AccessArticle

An Integrated UWB-IMU-Vision Framework for Autonomous Approaching and Landing of UAVs

by Xin Dong, Yuzhe Gao, Jinglong Guo, Shiyu Zuo, Jinwu Xiang, Daochun Li and Zhan Tu

Aerospace 2022, 9(12), 797; https://doi.org/10.3390/aerospace9120797 - 5 Dec 2022

Cited by 11 | Viewed by 2497

Abstract

Unmanned Aerial Vehicles (UAVs) autonomous approaching and landing on mobile platforms always play an important role in various application scenarios. Such a complicated autonomous task requires an integrated multi-sensor system to guarantee environmental adaptability in contrast to using each sensor individually. Multi-sensor fusion [...] Read more.

Unmanned Aerial Vehicles (UAVs) autonomous approaching and landing on mobile platforms always play an important role in various application scenarios. Such a complicated autonomous task requires an integrated multi-sensor system to guarantee environmental adaptability in contrast to using each sensor individually. Multi-sensor fusion perception demonstrates great feasibility to compensate for adverse visual events, undesired vibrations of inertia sensors, and satellite positioning loss. In this paper, a UAV autonomous landing scheme based on multi-sensor fusion is proposed. In particular, Ultra Wide-Band (UWB) sensor, Inertial Measurement Unit (IMU), and vision feedback are integrated to guide the UAV to approach and land on a moving object. In the approaching stage, a UWB-IMU-based sensor fusion algorithm is proposed to provide relative position estimation of vehicles with real time and high consistency. Such a sensor integration addresses the open challenge of inaccurate satellite positioning when the UAV is near the ground. It can also be extended to satellite-denied environmental applications. When the landing platform is detected by the onboard camera, the UAV performs autonomous landing. In the landing stage, the vision sensor is involved. With the visual feedback, a deep-learning-based detector and local pose estimator are enabled when the UAV approaches the landing platform. To validate the feasibility of the proposed autonomous landing scheme, both simulation and real-world experiments in extensive scenes are performed. As a result, the proposed landing scheme can land successfully with adequate accuracy in most common scenarios. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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23 pages, 3772 KiB

Open AccessArticle

A Novel Fuzzy-SAE Control Method for an Improved Test Wind Tunnel Simulating Sand/Dust Environment

by Ke Li, Yuangan Li, Liang Ma, Meng Liu and Jun Wang

Aerospace 2022, 9(12), 784; https://doi.org/10.3390/aerospace9120784 - 1 Dec 2022

Viewed by 1686

Abstract

The sand/dust environment is an important cause of aircraft failure. A sand/dust environment simulation experiment must be devised to meet the standard technical requirements. Therefore, this article designs the control system for a sand/dust environment test tunnel, including a wind speed control system [...] Read more.

The sand/dust environment is an important cause of aircraft failure. A sand/dust environment simulation experiment must be devised to meet the standard technical requirements. Therefore, this article designs the control system for a sand/dust environment test tunnel, including a wind speed control system and a pneumatic conveying and concentration control system. A fuzzy intelligent control method and a deep neural network are used to track and control experimental parameters. Compared to the classic PID algorithm, this method achieves smaller overshoot, faster response speed, no steady error and a better dynamic response curve, as demonstrated by both the test result in the wind tunnel and a simulation result. Both the classic PID control method and the high-precision fuzzy control method are fast, stable, and robust. The fuzzy-SAE intelligent control method not only has the high accuracy of the classic PID control method but also has the high speed, stability, and robustness of fuzzy control, which can meet the intelligent control requirements of the sand/dust environment test equipment. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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26 pages, 21791 KiB

Open AccessArticle

Two-Scale Asymptotic Homogenization Method for Composite Kirchhoff Plates with in-Plane Periodicity

by Zhiwei Huang, Yufeng Xing and Yahe Gao

Aerospace 2022, 9(12), 751; https://doi.org/10.3390/aerospace9120751 - 25 Nov 2022

Cited by 3 | Viewed by 1970

Abstract

This paper develops a two-scale asymptotic homogenization method for periodic composite Kirchhoff plates. In this method, a three-dimensional (3D) periodic plate problem is simplified as a Kirchhoff plate problem, which is governed by a fourth-order uniformly elliptic partial differential equation (PDE) with periodically [...] Read more.

This paper develops a two-scale asymptotic homogenization method for periodic composite Kirchhoff plates. In this method, a three-dimensional (3D) periodic plate problem is simplified as a Kirchhoff plate problem, which is governed by a fourth-order uniformly elliptic partial differential equation (PDE) with periodically oscillating coefficients. Then, a two-scale solution in an asymptotic expansion form is presented for the PDE, and it is found that the first-order perturbed displacement in the asymptotic solution is zero. Additionally, periodic boundary and normalization constraint conditions are proposed to determine the unique solution to unit cell problems. Moreover, standard finite element formulations for calculating the perturbed displacements are derived from the principle of virtual work. Physical interpretations of the influence functions are presented by analyzing the properties of self-balanced quasi-load vectors used for solving the influence functions. Numerical comparisons show that the present method is physically acceptable and highly accurate. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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10 pages, 1136 KiB

Open AccessArticle

The Association of Occupational Stress with Anxiety among Chinese Civil Pilots: The Moderating Role of Type A Behavior Pattern

by Yanlong Wang, Wei Guo, Lin Cheng, Ruipeng Ji, Yizhi Zhou, Xinhua Liu, Yanzeng Zhao, Ziyu Liu and Lijing Wang

Aerospace 2022, 9(12), 740; https://doi.org/10.3390/aerospace9120740 - 22 Nov 2022

Cited by 3 | Viewed by 1545

Abstract

Pilots are highly susceptible to anxiety symptoms due to the uncertainty of the dangers of aviation operations and the potential terror and insecurity that pilots experience over time. This research aims to understand the complex relationship between the occupational stress and group anxiety [...] Read more.

Pilots are highly susceptible to anxiety symptoms due to the uncertainty of the dangers of aviation operations and the potential terror and insecurity that pilots experience over time. This research aims to understand the complex relationship between the occupational stress and group anxiety symptoms of Chinese civil aviation pilots, and to analyze the type A behavior pattern (TABP) as a mediator for both issues. The occupational stress, anxiety symptoms and TABP of Chinese civil aviation pilots are investigated by using questionnaires based on the effort-reward-imbalance (ERI) scale, the Zung Self-Rating Anxiety Scale (SAS) and a TABP scale established based on Chinese people’s inherent characteristics. The study revealed that higher occupational stress experienced by Chinese civil aviation pilots exacerbated their anxiety symptoms, and that overcommitment and TABP mediated the relationship between occupational stress and anxiety symptoms. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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23 pages, 5135 KiB

Open AccessArticle

Neural-Network-Based Terminal Sliding Mode Control of Space Robot Actuated by Control Moment Gyros

by Xinhui Xia, Yinghong Jia, Xinlong Wang and Jun Zhang

Aerospace 2022, 9(11), 730; https://doi.org/10.3390/aerospace9110730 - 19 Nov 2022

Cited by 5 | Viewed by 1928

Abstract

This paper studies the trajectory tracking control of a space robot system (SRS) in the presence of the lumped uncertainties with no prior knowledge of their upper bound. Although some related control methods have been proposed, most of them have either not been [...] Read more.

This paper studies the trajectory tracking control of a space robot system (SRS) in the presence of the lumped uncertainties with no prior knowledge of their upper bound. Although some related control methods have been proposed, most of them have either not been applied to SRSs or lack rigorous stability proof. Therefore, it is still a challenge to achieve high accuracy and rigorous theoretical proof for tracking control of SRSs. This paper proposes a new integrated neural network- based control scheme for the trajectory tracking of a SRS actuated by control moment gyros (CMGs). A new adaptive non-singular terminal sliding mode (ANTSM) control method is developed based on an improved radial basis function neural network (RBFNN). In the control method, a new weight update law is proposed to learn the upper bound of the lumped uncertainties. With the advantages of RBFNN and ANTSM, the controller has high control accuracy, fast learning speed and finite-time convergence. Different from most on-ground robotic manipulator controllers, a kinematic controller with position and attitude control laws is also designed for the satellite platform to remain stable. The stability of the closed-loop system is proved by the Lyapunov method with a high mathematical standard. Comparative simulation results demonstrate the effectiveness of the proposed control scheme with preferable performance and robustness. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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19 pages, 5606 KiB

Open AccessArticle

Bio-Inspired Self-Organized Fission–Fusion Control Algorithm for UAV Swarm

by Xiaorong Zhang, Wenrui Ding, Yufeng Wang, Yizhe Luo, Zehao Zhang and Jing Xiao

Aerospace 2022, 9(11), 714; https://doi.org/10.3390/aerospace9110714 - 12 Nov 2022

Cited by 4 | Viewed by 2084

Abstract

Swarm control has become a challenging topic for the current unmanned aerial vehicle (UAV) swarm due to its conflicting individual behaviors and high external interference. However, in contrast to static obstacles, limited attention has been paid to the fission–fusion behavior of the swarm [...] Read more.

Swarm control has become a challenging topic for the current unmanned aerial vehicle (UAV) swarm due to its conflicting individual behaviors and high external interference. However, in contrast to static obstacles, limited attention has been paid to the fission–fusion behavior of the swarm against dynamic obstacles. In this paper, inspired by the interaction mechanism and fission–fusion motion of starlings, we propose a Bio-inspired Self-organized Fission–fusion Control (BiSoFC) algorithm for the UAV swarm, where the number of UAVs in the sub-swarm is controllable. It solves the problem of swarm control under dynamic obstacle interference with the tracking function. Firstly, we establish the kinematic equations of the individual UAV and swarm controllers and introduce a fission–fusion control framework to achieve the fission–fusion movement of the UAV swarm with a lower communication load. Afterward, a sub-swarm selection algorithm is built upon the topological interaction structure. When a swarm is faced with different tasks, the swarm that can control the number of agents in a sub-swarm can accomplish the corresponding task with a more reasonable number of agents. Finally, we design a sub-swarm trapping algorithm with a tracking function for the dynamic obstacles. The simulation results show that the UAV swarm can self-organize fission sub-swarms to cope with dynamic obstacles under different disturbance situations, and successfully achieve the goal of protecting the parent swarm from dynamic obstacles. The experimental results prove the feasibility and effectiveness of our proposed control algorithm. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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19 pages, 3852 KiB

Open AccessArticle

Comparative Study of the Thermal Enhancement for Spacecraft PCM Thermal Energy Storage Units

by Shisong Wang, Xu Hou, Jianbao Yin, Yuming Xing and Zixian Wang

Aerospace 2022, 9(11), 705; https://doi.org/10.3390/aerospace9110705 - 10 Nov 2022

Cited by 10 | Viewed by 2352

Abstract

To access the enhancement effect of the topology optimization and porous foam structure, numerical studies were conducted to investigate the heat conduction enhancement (by metal foam, graphite foam, topologically optimized fins, and combinations of metal foam and topologically optimized fins) of phase change [...] Read more.

To access the enhancement effect of the topology optimization and porous foam structure, numerical studies were conducted to investigate the heat conduction enhancement (by metal foam, graphite foam, topologically optimized fins, and combinations of metal foam and topologically optimized fins) of phase change material (PCM (n-octadecane)) based tubular thermal energy storage unit for spacecraft. The results showed that metal foam performed better than topologically optimized fins and a combination of metal foam and topology optimized fins, of which conductive material, unit mass, and volume fraction of PCM were the same. Graphite foam (140 W/(m·K)) had the best heat transfer enhancing effect, making PCM melt much faster than other enhancing methods investigated. A multi-criteria decision-making (MCDM) method integrated with the combined weight and TOPSIS method was introduced to evaluate the preferred alternatives’ performance based on the energy storage time, equivalent density, and energy storage. The evaluation pointed out that 3% topologically optimized aluminum fins with 98% copper foam had the best comprehensive performance. This study guided the optimal design of latent heat thermal energy storage units for spacecraft under microgravity. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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26 pages, 11974 KiB

Open AccessArticle

Wind Tunnel Tests of 3D-Printed Variable Camber Morphing Wing

by Sijia Jia, Zhenkai Zhang, Haibo Zhang, Chen Song and Chao Yang

Aerospace 2022, 9(11), 699; https://doi.org/10.3390/aerospace9110699 - 9 Nov 2022

Cited by 6 | Viewed by 3876

Abstract

This paper introduces the realization and wind tunnel testing of a novel variable camber wing equipped with compliant morphing trailing edges. Based on the aerodynamic shape and compliant mechanisms that were optimized in advance, a wind tunnel model called mTE4 was developed, in [...] Read more.

This paper introduces the realization and wind tunnel testing of a novel variable camber wing equipped with compliant morphing trailing edges. Based on the aerodynamic shape and compliant mechanisms that were optimized in advance, a wind tunnel model called mTE4 was developed, in which the rigid leading edge, rigid wing box, and compliant trailing edge were manufactured by 3D printing technology using three different materials. Due to difficulties in the detailed design of a small-scale model, special attention is devoted to the implementation procedure. Additionally, the static and dynamic characteristics of the proposed wind tunnel model were evaluated by ground tests, and the aerodynamic characteristics were evaluated by numerical methods. Then, the aerodynamic performance and the static aeroelastic deformation of the compliant trailing edge were investigated in a low-speed wind tunnel. The load-bearing ability of the proposed compliant morphing trailing edge device was validated and the continuous outer mold surface was found to persist throughout the entire testing period. Notably, a maximum deflection range of 37.9° at the airspeed of 15 m/s was achieved. Additionally, stall mitigation was also achieved by periodically deflecting the morphing trailing edge, enabling a stall angle delay of approximately 1° and 13% increase in post-stall lift coefficient. Finally, the development procedure was validated by comparing the lift between numerical and experimental results. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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24 pages, 8509 KiB

Open AccessArticle

A Conceptual Design and Optimization Approach for Distributed Electric Propulsion eVTOL Aircraft Based on Ducted-Fan Wing Unit

by Tielin Ma, Xiangsheng Wang, Nanxuan Qiao, Zilun Zhang, Jingcheng Fu and Mingmin Bao

Aerospace 2022, 9(11), 690; https://doi.org/10.3390/aerospace9110690 - 5 Nov 2022

Cited by 8 | Viewed by 4307

Abstract

The distributed electric propulsion (DEP) eVTOL aircraft has gained rising interest for its promising potential in high-speed cruise compared with conventional tilt-rotor configuration. The aerodynamic interference of the DEP units and wing could become more complicated with a variable thrust in multiple flight [...] Read more.

The distributed electric propulsion (DEP) eVTOL aircraft has gained rising interest for its promising potential in high-speed cruise compared with conventional tilt-rotor configuration. The aerodynamic interference of the DEP units and wing could become more complicated with a variable thrust in multiple flight conditions. Thus, it requires considerable effort to trade off in the whole design process. Aimed at improving the design efficiency in iteration cycling of a ducted-fan DEP eVTOL aircraft, a conceptual design and optimization approach is proposed in this paper regarding the single-ducted fan and its surrounding wing section as the basic unit. The optimization of the ducted-fan wing (DFW) unit is targeted at improving both hover and cruise efficiencies. After the verification of the span independence of the lift-and-drag coefficients of the DFW unit, a novel DEP eVTOL aircraft conceptual design approach is established based on the vertical meridional plane DFW unit performance analysis. In the following case study, the optimized DFW unit and the conceptual method are applied on a canard configuration, achieving 720 km/h maximum speed, a hovering efficiency of 76.3%, and a 10.7 cruise lift-to-drag ratio. The remarkable performance and concise workflow in the case study both demonstrated the applicability and effectiveness of the proposed design schemes for DEP eVTOL aircraft. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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27 pages, 13058 KiB

Open AccessArticle

Modeling and Simulation of Flight Profile and Power Spectrum for Near-Space Solar-Powered UAV

by Liang Zhang, Dongli Ma, Muqing Yang, Xiaopeng Yang and Yayun Yu

Aerospace 2022, 9(11), 672; https://doi.org/10.3390/aerospace9110672 - 30 Oct 2022

Cited by 2 | Viewed by 2507

Abstract

Currently, several solar-powered unmanned aerial vehicles (UAVs) have achieved 24 h uninterrupted cruise. However, models that can cruise for weeks or even months without interruption are in the minority. The technological progress requires the improvement of subsystems and also depends on the accurate [...] Read more.

Currently, several solar-powered unmanned aerial vehicles (UAVs) have achieved 24 h uninterrupted cruise. However, models that can cruise for weeks or even months without interruption are in the minority. The technological progress requires the improvement of subsystems and also depends on the accurate planning of flight profile and power spectrum in a long working cycle. Combined with the test data obtained during the development of a solar-powered UAV, this paper establishes systematic mathematical and physical models of aerodynamic, energy, and propulsion systems, which can reflect the change in performance parameters with flight conditions and the performance attenuation with time. Further, a track control strategy based on the principle of maximum energy utilization is proposed, and the energy balance model of each flight stage is established. On the basis of the strategy, the typical flight profile and power spectrum of a solar-powered UAV are analyzed. Finally, the input parameters are decomposed into task parameters (takeoff time window, flight season, flight latitude, takeoff weight) and performance parameters (lift–drag ratio, secondary battery density), and their effects on mission feasibility are studied respectively. The research methods and conclusions of this paper have reference significance for the mission and track planning of solar-powered UAVs. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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17 pages, 11060 KiB

Open AccessArticle

Numerical Optimization of Electromagnetic Performance and Aerodynamic Performance for Subsonic S-Duct Intake

by Bin Wang and Qiang Wang

Aerospace 2022, 9(11), 665; https://doi.org/10.3390/aerospace9110665 - 28 Oct 2022

Cited by 6 | Viewed by 2132

Abstract

In order to improve the performance of subsonic unmanned aerial vehicle (UAV), a knapsack S-duct intake has been designed. The influences of an S-bend diffuser on aerodynamic performance and electromagnetic performance were analyzed firstly. The viscous flow field has been simulated by solving [...] Read more.

In order to improve the performance of subsonic unmanned aerial vehicle (UAV), a knapsack S-duct intake has been designed. The influences of an S-bend diffuser on aerodynamic performance and electromagnetic performance were analyzed firstly. The viscous flow field has been simulated by solving Favre averaged Navier–Stokes equations using a shear stress transport (SST) k-ω turbulence model. The surface current has been simulated by solving Maxwell equations using a multi-level fast multipole method (MLFMM). The multi-objective optimization of the S-duct intake was studied by using the diffuser as the optimized object. The parametric expression of the diffuser model was realized using the fourth order function geometric representation technique. The efficient model based on the Kriging model and non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ) were used to accelerate the optimization progress. By analyzing the results of an optimal intake chosen from the Pareto front, the total pressure distortion (TPD) index DC60 has decreased by 0.24 at the designed Mach number of 0.9, and the average Radar Cross Section (RCS) has decreased by 2db at the frequency of 3GHz. The optimized S-duct intake could have both excellent aerodynamic performance and electromagnetic performance at various complex conditions. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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15 pages, 3674 KiB

Open AccessArticle

Experimental Investigation into the Effect of Fin Shapes on Heat Dissipation Performance of Phase Change Heat Sink

by Xu Liu, Keyong Zhu, Yijie Wei, Ziwei Chen, Mingming Ge and Yong Huang

Aerospace 2022, 9(11), 664; https://doi.org/10.3390/aerospace9110664 - 28 Oct 2022

Cited by 2 | Viewed by 1865

Abstract

In this paper, the thermal management of missile-borne components in a flight state is studied. Avoiding excessive component temperatures under the high-temperature circumstances brought by aerodynamic heat is a requirement to guarantee the equipment’s safe and reliable operation. In this work, we designed [...] Read more.

In this paper, the thermal management of missile-borne components in a flight state is studied. Avoiding excessive component temperatures under the high-temperature circumstances brought by aerodynamic heat is a requirement to guarantee the equipment’s safe and reliable operation. In this work, we designed four finned shell constructions for a phase change module using the phase change temperature control method and then studied their effects on the module’s ability to dissipate heat using an experimental approach. Three sizes of 30 mm, 40 mm, and 50 mm heating pads were used to replicate heat sources with various heat flux densities and heat dissipation regions, with reference to the heating characteristics of various chips. The results demonstrated that the square-shaped fin had the best heat dissipation effect after operating for 10 min under the power of 10 W and 20 W, while the strip-shaped fins exhibited the highest performance under the power of 30 W. The square-shaped fins had the best heat dissipation effect when reducing working time to 5 min. This paper proposes the optimal fin scheme under different power densities, as well as an enhanced heat dissipation idea for the melting process of the phase change materials based on the test results. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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19 pages, 5496 KiB

Open AccessArticle

Key Parameters of a Design for a Novel Reflux Subsonic Low-Density Dust Wind Tunnel

by Hao Wu, Meng Liu, Youzhi Mi, Jun Wang and Menglei Guo

Aerospace 2022, 9(11), 662; https://doi.org/10.3390/aerospace9110662 - 27 Oct 2022

Cited by 2 | Viewed by 1931

Abstract

The dust storm on the surface of Mars is a severe threat to Mars exploration missions. Taking adequate measures to avoid the impact of the harsh wind-blown dust environment is indispensable. Ground simulation of the Martian high-speed windblown dust environment is helpful for [...] Read more.

The dust storm on the surface of Mars is a severe threat to Mars exploration missions. Taking adequate measures to avoid the impact of the harsh wind-blown dust environment is indispensable. Ground simulation of the Martian high-speed windblown dust environment is helpful for analysis of the environmental effects and evaluations of the suitability of the components and materials. In this paper, a novel reflux subsonic low-density dust wind tunnel is presented to simulate the high-speed windblown dust environment of the Martian atmosphere with a velocity of more than 100 m/s. The sand and dust are fed into the wind tunnel through the ejector assembly together with the compressed gas, resulting in high uniformity of particles in the test section. The construction design of the Mars wind tunnel is introduced. The key parameters, which are the nozzle parameters and the contraction curve, are discussed in detail. The convergent nozzle is most suitable for the ejector assembly. Moreover, the bicubic curve is selected as the contraction curve. The gas-particle two-phase computational fluid dynamic (CFD) simulations demonstrate the rationality of the wind tunnel design. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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16 pages, 4008 KiB

Open AccessArticle

An Inversion Method Based on Inherent Similarity between Signals for Retrieving Source Mechanisms of Cracks

by Yue Kong, Weimin Chen, Ning Liu, Boqi Kang and Min Li

Aerospace 2022, 9(11), 654; https://doi.org/10.3390/aerospace9110654 - 26 Oct 2022

Cited by 2 | Viewed by 1376

Abstract

The knowledge of cracking mechanisms is significant for evaluating the healthy condition of aircraft structures and can be retrieved by moment tensor inversion based on the acoustic emission (AE) phenomenon. For engineering applications, the inversion method cannot compute accurate results because the waveforms [...] Read more.

The knowledge of cracking mechanisms is significant for evaluating the healthy condition of aircraft structures and can be retrieved by moment tensor inversion based on the acoustic emission (AE) phenomenon. For engineering applications, the inversion method cannot compute accurate results because the waveforms recorded by sensors are commonly contaminated by noise. Consequently, the correlation calculation of de-noising is introduced into the inversion and sufficient correlation functions are needed. In this paper, the correlation function of raw waveforms is proposed and based on the inherent similarity between the signals induced by one source and recorded by different sensors. According to the synthetic tests, the error of the inversion method based on the new correlation function is approximately 1/10 of that of the commonly used amplitude method. Although the inversion accuracy is influenced by the phase differences and the ratio of noise frequency to signal frequency, the influence is limited and the new correlation function is suitable for most practical cases. The inversion method based on the new correlation function does not require the knowledge of noise spectra or any complex calculation processes and provides a new way to improve the inversion accuracy of cracking mechanisms with little additional computation consumption. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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19 pages, 7806 KiB

Open AccessArticle

Analytical Study on Lift Performance of a Bat-Inspired Foldable Flapping Wing: Effect of Wing Arrangement

by Dawei Bie, Daochun Li, Huadong Li, Zi Kan and Zhan Tu

Aerospace 2022, 9(11), 653; https://doi.org/10.3390/aerospace9110653 - 26 Oct 2022

Cited by 5 | Viewed by 2395

Abstract

In this work, we use a three-dimensional computational fluid dynamics (CFD) simulation to comprehend how the two wing arrangement variables, i.e., inner/outer wing proportion and mid-stroke dihedral, affect the lift characteristic of a bat-inspired span foldable flapping wing. The employed flapping mechanism is [...] Read more.

In this work, we use a three-dimensional computational fluid dynamics (CFD) simulation to comprehend how the two wing arrangement variables, i.e., inner/outer wing proportion and mid-stroke dihedral, affect the lift characteristic of a bat-inspired span foldable flapping wing. The employed flapping mechanism is based on previous work. In this study, the structure parameters of the flapping mechanism remain unchanged across all simulations. Based on the CFD results, the tendency and work point regarding maximum lift generation can be found by changing both of the variables. As a result, when modifying the inner/outer wing proportion without changing the total wing shape and area, the maximum time-averaged lift appears in the case of the inner wing occupying half of the semi-span. In addition, when changing the dihedral, the maximum time-averaged lift was obtained when the inner wing dihedral was equal to zero. To discuss the lift variation of the foldable flapping wing, pressure distribution and vorticity of the flow field at certain time points were provided corresponding to the instantaneous lift curves. The conclusions of this research are able to help understand the wing arrangement of birds and bats issued from natural selection, and also support the future design of flapping wing micro-aerial-vehicles. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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27 pages, 2683 KiB

Open AccessArticle

Dynamics Modeling and Characterization of Sunk Screw Connection Structure in Small Rockets

by Xiaotian Zhang, Ruiqing Wang, Xiaogang Li, Chengyang Lu, Zhengkang Wang and Wenlong Wang

Aerospace 2022, 9(11), 648; https://doi.org/10.3390/aerospace9110648 - 25 Oct 2022

Cited by 1 | Viewed by 1817

Abstract

Bolted flange joints are widely used in engineering structures. Sunk screw connection structures commonly used in small rockets and missiles exhibit significant nonlinear characteristics when subjected to forces. In this article, a study of the dynamic characteristics of sunk screw connection is conducted. [...] Read more.

Bolted flange joints are widely used in engineering structures. Sunk screw connection structures commonly used in small rockets and missiles exhibit significant nonlinear characteristics when subjected to forces. In this article, a study of the dynamic characteristics of sunk screw connection is conducted. A 3-dof trilinear dynamic model is proposed, based on the study of the stiffness characteristics of the connection structure and considering contact nonlinearities. The connection surface is simplified as two axial trilinear springs and a lateral linear spring. The motion of the system can be divided into nine regions by the turning point of the trilinear springs. So that the motion of the system in each region can be completely resolved, the dynamic characteristics of the 3-dof trilinear system under impulse load and simple harmonic load are studied by means of semi-numerical analytical method. It is found that the response frequency of the system remains unchanged under a small impulse load, and the response can be obtained by approximate analytical expressions. When the impulse load is large, the response frequency is fluctuant, which reflects the sensitivity of the nonlinear system to the magnitude of impulse load. Under the simple harmonic excitation of bending moment, the response frequency curve of the system presents good single peak characteristics when the excitation amplitude is small. When the amplitude is large, the peak frequency of the system shifts, and the phenomenon of multi-peak resonance is shown in a certain range. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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22 pages, 6512 KiB

Open AccessArticle

Investigations into Gas-Pore Effects on Fatigue Strength with a Peridynamic Approach

by Binchao Liu, Bocai Chen, Songsong Lu, Qiuyi Wang and Rui Bao

Aerospace 2022, 9(11), 641; https://doi.org/10.3390/aerospace9110641 - 24 Oct 2022

Cited by 5 | Viewed by 1599

Abstract

Fatigue evaluations are one of the main challenges to applying additively manufactured primary structural elements onto aircraft, especially for the gas-pore effects on fatigue strength. In this work, a bond decomposition strategy (BDS) in peridynamics (PD) is proposed; combined with our previously proposed [...] Read more.

Fatigue evaluations are one of the main challenges to applying additively manufactured primary structural elements onto aircraft, especially for the gas-pore effects on fatigue strength. In this work, a bond decomposition strategy (BDS) in peridynamics (PD) is proposed; combined with our previously proposed model for fatigue damage, numerical simulations were performed to study the effect of Gas Pore (GP) on fatigue strength. Compared with the strategies in original paradigm of peridynamics, BDS achieves more elaborate description for bond status, predicts deformation fields around discontinuities with improved accuracy, and makes the spacing of material points become independent of discontinuity geometries. Two initiation modes are found in PD simulations, which exert an obvious impact on the final fatigue lifetimes; furthermore, it is revealed that GP not only leads to lower fatigue strength but also results in dispersity of fatigue strength data, in which dispersity is more severe if the GP size is larger, and the decline of fatigue strength is the most severe if the GP is located at subsurface for the same GP size. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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24 pages, 11053 KiB

Open AccessArticle

Numerical Investigation on Particle Erosion Characteristics of the Elbow Pipe in Gas-Steam Ejection Power System

by Qifei Chen and Guozhu Liang

Aerospace 2022, 9(11), 635; https://doi.org/10.3390/aerospace9110635 - 22 Oct 2022

Cited by 3 | Viewed by 1875

Abstract

In gas-steam ejection power systems, the Al₂O₃ particles in combustion products can cause severe erosion on the downstream elbow pipe. To calculate the particle erosion, a modelling approach is developed by combining a discrete phase model with a flow-thermal coupling [...] Read more.

In gas-steam ejection power systems, the Al₂O₃ particles in combustion products can cause severe erosion on the downstream elbow pipe. To calculate the particle erosion, a modelling approach is developed by combining a discrete phase model with a flow-thermal coupling model and introducing wall temperature parameters into the erosion model. Furthermore, the influence of particle size, total temperature and pressure, and particle mass flow rate was investigated. The results show that high temperature erosion depth can be expressed as the product of the time integral of temperature factor and the erosion rate at room temperature and is 1.63–3.57 times that at room temperature under different particle sizes. With the increase of particle size, the maximum erosion position tends to the inlet of the bend, and its value increases first and then decreases with the peak value 0.418 mm at particle diameter of 100 µm. The decrease in total temperature and total pressure reduces the erosion rate by reducing the particle velocity. The particle mass flow rate affects the gas-particle flow which, may cause the erosion to change greatly, especially when particle diameter is below 40 µm. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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25 pages, 6767 KiB

Open AccessArticle

Simulation of Forced Convection Frost Formation in Microtubule Bundles at Ultra-Low Temperature

by Youzhi Mi, Meng Liu, Hao Wu, Jun Wang and Ruikai Zhao

Aerospace 2022, 9(10), 630; https://doi.org/10.3390/aerospace9100630 - 21 Oct 2022

Cited by 1 | Viewed by 2113

Abstract

Hypersonic vehicles are an important area of research in the aerospace field today. One of the important issues is the power of the engine. In order to achieve large-span flight speeds, a more efficient approach is to use combined power systems. However, the [...] Read more.

Hypersonic vehicles are an important area of research in the aerospace field today. One of the important issues is the power of the engine. In order to achieve large-span flight speeds, a more efficient approach is to use combined power systems. However, the problem of pre-cooler icing can occur in combined engine applications. The flow in the pre-cooler is extremely complex. Outside the tube is the high-temperature wet air entering from the engine intake, and the tube cooling is the ultra-low temperature cooling medium. Icing not only increases the heat exchange resistance of the pre-cooler during operation and affects the heat exchange performance of the pre-cooler, but also causes a large total pressure loss, resulting in a degradation of the engine performance. There is a lack of research on the icing law of the pre-cooler under different parameters. Therefore, it is necessary to conduct a corresponding numerical calculation study on pre-cooler icing and explore the influence of various influencing factors on icing. In this paper, a mathematical model of icing (frost) is established for the frosting phenomenon that may occur during the operation of the pre-cooler. Additionally, the principle of heat and mass transfer in the icing process is described by the mathematical model, and the influence of different parameters on the frosting parameters is explored by using the computational fluid dynamics (CFD) method. The law of tube bundle icing under different parameters was calculated, and the variation laws of frost layer morphology and wet air pressure drop were obtained. The laws of tube bundle icing under different parameters were calculated, and the changes in frost layer pattern and wet air pressure drop when each parameter was changed, which can provide guidance for the design and application of pre-coolers in the future. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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16 pages, 6853 KiB

Open AccessArticle

Stability Enhancement and Noise Reduction of an Axial Compressor with Foam Metal Casing Treatment

by Jia Li, Xu Dong, Dakun Sun, Yuqing Wang, Chunwang Geng and Xiaofeng Sun

Aerospace 2022, 9(10), 628; https://doi.org/10.3390/aerospace9100628 - 21 Oct 2022

Cited by 4 | Viewed by 1989

Abstract

Foam metal is a foam-like substance with a high porosity; it has been used in flow control, vibration abatement, and acoustic absorption, mainly based on its physical properties. The aim of the current paper is to investigate the effect of foam metal casing [...] Read more.

Foam metal is a foam-like substance with a high porosity; it has been used in flow control, vibration abatement, and acoustic absorption, mainly based on its physical properties. The aim of the current paper is to investigate the effect of foam metal casing treatments on the stability and acoustic level of a low-speed axial flow compressor. The experimental results show that the casing treatment improves the stall margin by 14.9%, without any efficiency loss. In terms of noise, the SPL of the tonal noise at the third order of BPF is reduced by 3.2 dB, while the SPL of the broadband noise is reduced up to 2.4 dB. The comparison in evolutions of the tip structure in a smooth casing condition and with a casing treatment indicates that the casing treatment affects the origination and the development of the tip leakage vortex. The working mechanism is also discussed. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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16 pages, 13229 KiB

Open AccessArticle

Formation Mechanism and Modeling Method of Wrinkling Defects in Variable Angle Tow Steering Fiber Placement

by Minghui Yi, Fei Liu, Wuxiang Zhang and Xilun Ding

Aerospace 2022, 9(10), 620; https://doi.org/10.3390/aerospace9100620 - 19 Oct 2022

Cited by 2 | Viewed by 2265

Abstract

Variable angle tow steering technology is capable of manufacturing complex aviation parts with a trajectory of intricate curvature planned based on stress or profile characteristics, which greatly improves the forming efficiency, design flexibility and mechanical properties of composite structures. In view of the [...] Read more.

Variable angle tow steering technology is capable of manufacturing complex aviation parts with a trajectory of intricate curvature planned based on stress or profile characteristics, which greatly improves the forming efficiency, design flexibility and mechanical properties of composite structures. In view of the forming defects such as buckling and wrinkles caused by the lateral bending of fiber prepreg tow, a theoretical buckling model based on the Rayleigh Ritz method, the principle of minimum potential energy and the viscoelastic foundation is established, in which the adhesion coefficient is characterized by the degree of intimate contact to introduce process parameters. On the basis of the contact mechanics analysis, the distribution of the compaction pressure and bending stress is studied to improve the theoretical model, and the critical buckling load and the minimum radius of the tow under the normal and tangential contact conditions are determined precisely. Finally, the finite element models of compaction and variable angle steering placement are proposed, and the theoretical model and simulation model are verified by corresponding trials. It is demonstrated that defects can be effectively suppressed through optimizing process parameters. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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18 pages, 4916 KiB

Open AccessArticle

A New Method for Analyzing the Aero-Optical Effects of Hypersonic Vehicles Based on a Microscopic Mechanism

by Bo Yang, He Yu, Chaofan Liu, Xiang Wei, Zichen Fan and Jun Miao

Aerospace 2022, 9(10), 618; https://doi.org/10.3390/aerospace9100618 - 18 Oct 2022

Cited by 4 | Viewed by 2427

Abstract

Aero-optical effects are the key factors that restrict the accuracy of the optical sensors of hypersonic vehicles, and the numerical simulation of aero-optical effects is a powerful tool with which to analyze aero-optical distortion. Most existing research focuses on the simulation analysis of [...] Read more.

Aero-optical effects are the key factors that restrict the accuracy of the optical sensors of hypersonic vehicles, and the numerical simulation of aero-optical effects is a powerful tool with which to analyze aero-optical distortion. Most existing research focuses on the simulation analysis of refraction distortion based on the density field at the macro level via the ray-tracing method. In this paper, a method for analyzing aero-optical effects based on the interaction between photons and gas molecules is proposed and can explain the optical distortion and energy dissipation caused by aero-optical effects at the micro level. By establishing a transmission model of photons in turbulence, a simulation method of aero-optical effects based on a microscopic mechanism is designed and breaks through the limitations of a traditional macro method in energy analyses. The optical distortion parameters based on photonics are compared with the physical quantities of traditional aero-optical effects, which verifies the effectiveness of the micro analysis on the macro scale and provides a new idea for studying the microscopic mechanism of aero-optical effects. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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18 pages, 6577 KiB

Open AccessArticle

Aerodynamic Characteristics of Bristled Wings in Flapping Flight

by Tong Shen, Zhan Tu, Daochun Li, Zi Kan and Jinwu Xiang

Aerospace 2022, 9(10), 605; https://doi.org/10.3390/aerospace9100605 - 15 Oct 2022

Cited by 1 | Viewed by 2009

Abstract

This study focuses on the aerodynamics of the smallest flying insects’ bristled wings. We measured and analyzed wing morphological data from 38 specimens of Mymaridae. Bristled wing flight was numerically simulated at Reynolds numbers from 1 to 80. The aerodynamic force, power, and [...] Read more.

This study focuses on the aerodynamics of the smallest flying insects’ bristled wings. We measured and analyzed wing morphological data from 38 specimens of Mymaridae. Bristled wing flight was numerically simulated at Reynolds numbers from 1 to 80. The aerodynamic force, power, and efficiency of bristled wings using lift-based stroke, drag-based stroke, and clap-and-fling mechanism were evaluated. An unusual clap-and-fling pattern considering bristle crossing was first proposed. Our study shows that with a reduction in the wingspan of Mymaridae, the proportion of the wingtip bristled area increases. A lift-based stroke is superior to a drag-based stroke in terms of vertical force production and aerodynamic efficiency at 5 ≤ Re ≤ 20. Bristled wings employing the clap-and-fling mechanism achieve both vertical force and efficiency augmentation, while bristle crossing incurs a substantial horizontal force and contributes little to vertical force augmentation. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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16 pages, 1850 KiB

Open AccessArticle

Dynamics, Deployment and Retrieval Strategy for Satellite-Sail Transverse Formation with Model Inaccuracy

by Yini Zhong and Rui Zhong

Aerospace 2022, 9(10), 602; https://doi.org/10.3390/aerospace9100602 - 14 Oct 2022

Cited by 3 | Viewed by 1730

Abstract

One of the important applications of the space tethered system is formation flying. To satisfy the requirement for interferometry of ground targets by remote-sensing satellites, a new type of tethered solar sail spacecraft has been proposed in recent research. The replacement of subsatellites [...] Read more.

One of the important applications of the space tethered system is formation flying. To satisfy the requirement for interferometry of ground targets by remote-sensing satellites, a new type of tethered solar sail spacecraft has been proposed in recent research. The replacement of subsatellites of conventional tethered satellite systems with solar sail spacecraft allows for a special formation configuration in which the main satellite is in sun-synchronous orbit and the subsolar sail is in displaced orbit. If the solar sail is at the appropriate attitude, the main satellite and the solar sail spacecraft connected by metal tethers could move side by side, hence this formation system is called transverse formation. The relative baseline of this transverse formation system is perpendicular to the ground trajectory of the satellite, effectively solving the problem that the relative baseline of conventional orbital formations varies in a trigonometric cycle. Researchers on the past ignored the mass and elasticity of the tether, and considered the tether just a constraint in the model system. Since the solar sail is generally quite light compared to the other components of the system, the model inaccuracy caused by ignoring the mass of the tether on the dynamic model and control is extremely obvious. This paper investigates the relative dynamics and control of a proposed system during the deployment process with the mass of the tether. Two precise models of satellite-sail systems are established. One is based on the dumbbell model with the mass tether for the tethered satellite system, and the other is on the basis of the beads model of a tethered satellite system. The rigid one is for control design and the flexible one is for dynamic simulation. It is concluded that the length of the tether and attitude angle of the transverse formation configuration can be decoupled and controlled separately. On the basis of the models, a length rate and LQR control law is developed and the control of the deployment and retrieval process of the tethered solar sail system is investigated. Numerical simulations are performed to verify the accuracy of the conclusions. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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20 pages, 17616 KiB

Open AccessArticle

Prediction of Crack Growth Life at Elevated Temperatures with Neural Network-Based Learning Schemes

by Songsong Lu, Binchao Liu, Rong Yang, Qiuyi Wang and Rui Bao

Aerospace 2022, 9(10), 600; https://doi.org/10.3390/aerospace9100600 - 14 Oct 2022

Cited by 2 | Viewed by 1867

Abstract

Applying the machine learning (ML) technique in the modelling of crack growth (CG) behavior is a potential way to improve the efficiency and precision of CG assessment. However, research in this field at elevated temperatures is limited, although a lot of achievements have [...] Read more.

Applying the machine learning (ML) technique in the modelling of crack growth (CG) behavior is a potential way to improve the efficiency and precision of CG assessment. However, research in this field at elevated temperatures is limited, although a lot of achievements have been obtained in CG assessment at room temperature. Neutral network (NN)-based methods to model the CG at elevated temperatures were therefore investigated in this paper. An “indirect” method (NNK method) assessing the CG by modelling and integrating the crack growth rate (CGR) was established. A “direct” method (ENNIL method) was built by further developing the NN-based increment learning scheme. The NNK method shows high accuracy in CG prediction with relatively short CG life, while the ENNIL method gives perfectly predicted results for cases with relatively long CG life. The combination of these two methods may be an effective way to further improve CG assessment at elevated temperatures. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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17 pages, 2380 KiB

Open AccessArticle

Hopf Bifurcation Analysis of the Combustion Instability in a Liquid Rocket Engine

by Xuanye Liang, Lijun Yang, Gaofeng Wang and Jingxuan Li

Aerospace 2022, 9(10), 593; https://doi.org/10.3390/aerospace9100593 - 11 Oct 2022

Cited by 7 | Viewed by 2568

Abstract

The bifurcation process of self-sustained combustion instability pressure perturbations in a liquid rocket combustor is investigated based on the Helmholtz equations and a pressure dependent flame describing function. The modal frequency and growth rates are numerically resolved by the commercial software COMSOL multiphysics. [...] Read more.

The bifurcation process of self-sustained combustion instability pressure perturbations in a liquid rocket combustor is investigated based on the Helmholtz equations and a pressure dependent flame describing function. The modal frequency and growth rates are numerically resolved by the commercial software COMSOL multiphysics. Validation of the numerical approach is firstly conducted on a Rijke tube combustor, and a supercritical bifurcation for the first longitudinal mode is observed. The bifurcation diagrams for the first transverse mode for different time delays and gain index of the flame describing function are analyzed. Only the supercritical bifurcation presents for this configuration. The trajectory of Hopf points and the bifurcation diagram feature period motions with increasing the time delay. The effect of flame length distributions on the bifurcation diagrams is analyzed by considering a non-uniform flame length distribution model. Results show that the distribution has a large impact on the bifurcation process, e.g., the first transverse mode is more unstable for the non-uniform distribution. Finally, a subcritical bifurcation is found when a more complicated flame describing function is considered; the bistable region presents and the condition for this is discussed. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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16 pages, 1191 KiB

Open AccessArticle

Three-Dimensional Analytical Solutions for Acoustic Transverse Modes in a Cylindrical Duct with Axial Temperature Gradient and Non-Zero Mach Number

by Jiaqi Nan, Jingxuan Li and Lijun Yang

Aerospace 2022, 9(10), 588; https://doi.org/10.3390/aerospace9100588 - 10 Oct 2022

Viewed by 1993

Abstract

Cylindrical ducts with axial mean temperature gradient and mean flows are typical elements in rocket engines, can combustors, and afterburners. Accurate analytical solutions for the acoustic waves of the longitudinal and transverse modes within these ducts can significantly improve the performance of low [...] Read more.

Cylindrical ducts with axial mean temperature gradient and mean flows are typical elements in rocket engines, can combustors, and afterburners. Accurate analytical solutions for the acoustic waves of the longitudinal and transverse modes within these ducts can significantly improve the performance of low order acoustic network models for analyses of acoustic behaviours and combustion instabilities in these kinds of ducts. Here, we derive an acoustic wave equation as a function of pressure perturbation based on the linearised Euler equations (LEEs), and the modified WKB approximation method is applied to derive analytical solutions based on very few assumptions. The eigenvalue system is built based on the proposed solutions and applied to predict the resonant frequencies and growth rate for transverse modes. Validations of the proposed solutions are performed by comparing them to the numerical results directly calculated from the LEEs. Good agreements are found between analytical reconstruction and numerical results of three-dimensional transverse modes. The system with both mean temperature profile and mean flow presents a larger absolute value of the growth rate than the condition of either uniform mean temperature or no mean flow. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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13 pages, 3806 KiB

Open AccessArticle

A Planar Underactuated Compaction Mechanism with Self-Adaptability for Automated Fiber Placement Heads

by Fei Liu, Wuxiang Zhang, Junfan Shang, Minghui Yi, Shenru Wang and Xilun Ding

Aerospace 2022, 9(10), 586; https://doi.org/10.3390/aerospace9100586 - 9 Oct 2022

Cited by 4 | Viewed by 1854

Abstract

Automated fiber placement (AFP) systems accommodate complex-shaped structures by pressing fibers against the non-planar surfaces of mandrels, in which compaction mechanisms are of crucial significance. A conventional compaction mechanism utilizes an independent actuator with compacting rollers to conform surfaces. Compared with these mechanisms, [...] Read more.

Automated fiber placement (AFP) systems accommodate complex-shaped structures by pressing fibers against the non-planar surfaces of mandrels, in which compaction mechanisms are of crucial significance. A conventional compaction mechanism utilizes an independent actuator with compacting rollers to conform surfaces. Compared with these mechanisms, underactuated mechanisms can improve self-adjustability and functionality. This research introduces the concept design and the analysis of a planar underactuated compaction mechanism for automated fiber placement heads. Firstly, the requirements and design premise are determined. Then, a novel planar underactuated compaction mechanism with a bistable structure is constructed based on the metamorphic design theory. Secondly, the analytical models are established to give insight into the motion characteristics of the mechanism. Moreover, the example and simulation results are presented to verify the conceptual design. Furthermore, the standard deviation of the contact force of the planar underactuated compaction mechanism is much lower than that of a conventional compaction mechanism under equal conditions. Finally, the potential application of the underactuated mechanisms is discussed. Thus, this research shows that the designed compaction mechanism increases the adjustability, robustness, and high repeatability in positioning and can be used to simplify the motion planning for AFP systems when producing complex structures. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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13 pages, 4241 KiB

Open AccessArticle

An Available-to-Implement Thermal Facility for Dynamic Bleed Air Test of Aircraft Environmental Control System

by Yonggui Zheng, Meng Liu, Hao Wu, Jun Wang, Peng Xu and Side Jin

Aerospace 2022, 9(10), 584; https://doi.org/10.3390/aerospace9100584 - 8 Oct 2022

Viewed by 3221

Abstract

As a critical system of onboard aircraft equipment, the environmental control system (ECS) has an essential impact on flight safety. The performance of the ECS is usually tested using the thermal test facility. The facility comprises temperature and pressure simulation units to simulate [...] Read more.

As a critical system of onboard aircraft equipment, the environmental control system (ECS) has an essential impact on flight safety. The performance of the ECS is usually tested using the thermal test facility. The facility comprises temperature and pressure simulation units to simulate the engine bleed air. Currently, the ECS often fails due to the dynamic and rapid changes in the temperature and pressure of bleed air. To achieve the dynamic bleed air simulation, the most critical problem is to simulate the bleed air’s rapid heating and boost process during the actual engine working process. However, the temperature simulation unit has the characteristics of nonlinear and large inertia. Moreover, temperature and pressure control are strongly coupled. These characteristics usually lead to temperature and pressure dynamic control failure. This paper introduces a novel facility that adopted the hot and cold blending method to realize the rapid response of the temperature. Furthermore, it used a particular system structure to reduce pressure and temperature control coupling. In addition, it adopted the lookup-table-based PID (LPID) controller to acquire the rapid response and good steady-state performance of temperature and pressure control. Experimental control results are presented and discussed. The results showed that the facility could meet ECS’s dynamic and steady-state test requirements. The novel facility makes up for the insufficient dynamic test capacity of the previously developed ECS test facilities. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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18 pages, 6449 KiB

Open AccessArticle

Simulation of and Experimental Research on Rivulet Model on Airfoil Surface

by Yanxia Lou, Xueqin Bu, Xiaobin Shen, Guiping Lin, Ruchen Zhang, Feixiong Zeng, Haichuan Jin, Kuiyuan Ma and Dongsheng Wen

Aerospace 2022, 9(10), 570; https://doi.org/10.3390/aerospace9100570 - 29 Sep 2022

Cited by 3 | Viewed by 2307

Abstract

The occurrence of aircraft icing can significantly affect flight performance. One of the most important aspects in the study of anti-icing technology for aircraft is the distribution of overflow water. Owing to the external airflow pressure, shear stress, and surface tension, the water [...] Read more.

The occurrence of aircraft icing can significantly affect flight performance. One of the most important aspects in the study of anti-icing technology for aircraft is the distribution of overflow water. Owing to the external airflow pressure, shear stress, and surface tension, the water film breaks up to form steady rivulets. Experiments on NACA0012 airfoil surfaces were conducted based on an open straight-flow and low-speed wind tunnel. Simultaneously, an engineered three-dimensional rivulet model considering the surface roughness was established based on the energy-minimum principle. A comparison between the simulation and experimental results shows that the errors in the water film breakup location and the flow velocity of rivulets are less than 20%, and the errors in the spacing and width of rivulets are less than 40%. In addition, the effects of surface temperature and uniform roughness on water film breakup were investigated. Furthermore, the rivulet model was applied to the numerical calculation of the thermal performance of hot-air anti-icing systems. The simulations reveal that the uniform roughness of the wing surface causes the water film to break earlier. As the surface roughness increases, the thickness, spacing, and width of the rivulets increase, and the rivulet flow velocity decreases. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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19 pages, 4560 KiB

Open AccessArticle

A Time Cooperation Guidance for Multi-Hypersonic Vehicles Based on LSTM Network and Improved Artificial Potential Field Method

by Jia Song, Xiaowei Xu, Xindi Tong and Kai Zhao

Aerospace 2022, 9(10), 562; https://doi.org/10.3390/aerospace9100562 - 28 Sep 2022

Cited by 9 | Viewed by 2502

Abstract

Time cooperation guidance is a key technology which can greatly increase the success rate of flight missions. However, it is difficult to satisfy all the strict constraints when designing the guidance system for multiple hypersonic vehicles. To solve these problems, a time cooperation [...] Read more.

Time cooperation guidance is a key technology which can greatly increase the success rate of flight missions. However, it is difficult to satisfy all the strict constraints when designing the guidance system for multiple hypersonic vehicles. To solve these problems, a time cooperation framework is proposed. In this paper, the longitudinal predictor–corrector guidance law is firstly applied to meet the terminal and path constraints simultaneously. To settle the inaccurate estimation problem of residual flight time, a long short-term memory network (LSTM network) is trained and adopted in a time decision module, whose inputs are selected as six-dimensional feature vectors combined with the features of the sequential ballistics. In the time control module, the traditional artificial potential field method is modified to handle the no-fly zone constraints problem. Furthermore, the time potential field as a new type of potential field is added to indirectly control the flight time of hypersonic vehicles. The final simulation results show that the novel time potential field is compatible with the traditional potential field, which can satisfy the no-fly zone and flight time constraints at the same time. Meanwhile, compared with other time cooperative guidance, the algorithm proposed in this paper performs better in terms of time adjustable range. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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14 pages, 7890 KiB

Open AccessArticle

A Novel Efficient Prediction Method for Microscopic Stresses of Periodic Beam-like Structures

by Yufeng Xing, Lingyu Meng, Zhiwei Huang and Yahe Gao

Aerospace 2022, 9(10), 553; https://doi.org/10.3390/aerospace9100553 - 26 Sep 2022

Cited by 4 | Viewed by 1827

Abstract

This paper presents a novel superposition method for effectively predicting the microscopic stresses of heterogeneous periodic beam-like structures. The efficiency is attributed to using the microscopic stresses of the unit cell problem under six generalized strain states to construct the structural microscopic stresses. [...] Read more.

This paper presents a novel superposition method for effectively predicting the microscopic stresses of heterogeneous periodic beam-like structures. The efficiency is attributed to using the microscopic stresses of the unit cell problem under six generalized strain states to construct the structural microscopic stresses. The six generalized strain states include one unit tension strain, two unit bending strains, one unit torsion strain, and two linear curvature strains of a Timoshenko beam. The six microscopic stress solutions of the unit cell problem under these six strain states have previously been used for the homogenization of composite beams to equivalent Timoshenko beams (Acta. Mech. Sin. 2022, 38, 421520), and they are employed in this work. In the first step of achieving structural stresses, two stress solutions concerning linear curvatures are transformed into two stress solutions concerning unit shear strains by linearly combining the stresses under two unit bending strains. Then, the six stress solutions corresponding to six generalized unit beam strains are combined together to predict the structural microscopic stresses, in which the six stress solutions serve as basic stresses. The last step is to determine the coefficients of these six basic stress solutions by the principle of the internal work equivalence. It is found that the six coefficients, in terms of the product of the inverse of the effective stiffness matrix and the macroscopic internal force column vector, are the actual generalized strains of the equivalent beam under real loads. The obtained coefficients are physically reasonable because the basic stress solutions are produced by the generalized unit strains. Several numerical examples show that the present method, combining the solutions of the microscopic unit cell problem with the solutions of the macroscopic equivalent beam problem, can accurately and effectively predict the microscopic stresses of whole composite beams. The present method is applicable to composite beams with arbitrary periodic microstructures and load conditions. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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27 pages, 8845 KiB

Open AccessArticle

Reverse Design of Solid Propellant Grain for a Performance-Matching Goal: Shape Optimization via Evolutionary Neural Network

by Wentao Li, Wenbo Li, Yunqin He and Guozhu Liang

Aerospace 2022, 9(10), 552; https://doi.org/10.3390/aerospace9100552 - 26 Sep 2022

Cited by 3 | Viewed by 4642

Abstract

The reverse design of solid propellant grain for a performance-matching goal, one of the most challenging directions of the solid rocket motor designing work, is limited by the traditional semi-empirical parameter-driven optimization methods based on some predefined grain configurations. Grain designers call for [...] Read more.

The reverse design of solid propellant grain for a performance-matching goal, one of the most challenging directions of the solid rocket motor designing work, is limited by the traditional semi-empirical parameter-driven optimization methods based on some predefined grain configurations. Grain designers call for a new method that can automatically provide brand-new grain shapes beyond the traditional ones. In this work, a shape optimization method based on the evolutionary neural network is proposed to achieve the reverse design of two-dimensional (2D) grains. Firstly, the modified ellipse-form eikonal equation is solved by using the finite element method to realize the burn-back analysis of 2D grains in any shape on a fixed unstructured mesh. Then, the neural network is introduced to determine the spatial distribution of the propellant to define the grain shape. The hyperparameters of the network are continuously evolved with the aid of the genetic algorithm. Finally, the optimal grain shape that matches the performance goal most is obtained. The method is verified in different scenarios. The result shows that the design can precisely match the given pressure-time curve of star grains and slotted-tube grains. Furthermore, the method can automatically evolve a new dendritic-shaped grain that matches the given dual-thrust pressure-time curve. Since the reverse design uses the concept of shape optimization, it does not require any pre-selection of the grain shape, and the designers shall be free from defining different kinds of geometric parameters for specific grain configurations. Consequently, the method has the potential to apply in the reconstruction of an actual grain and the conceptual design of innovative grain configurations. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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19 pages, 9515 KiB

Open AccessArticle

Parametric Study on Aerodynamic Performance of a Flapping Wing Rotor MAV Capable of Sustained Flight

by Ziyu Wang, Zi Kan, Huadong Li, Daochun Li, Shiwei Zhao and Zhan Tu

Aerospace 2022, 9(10), 551; https://doi.org/10.3390/aerospace9100551 - 26 Sep 2022

Cited by 9 | Viewed by 2524

Abstract

By combining the flapping and rotary motion, a flapping wing rotor (FWR) shows unique kinematics of motion. It can produce a significantly higher aerodynamic efficiency and lift coefficient than insect-like flapping wings. However, due to the lack of controllable FWR aerial vehicles, the [...] Read more.

By combining the flapping and rotary motion, a flapping wing rotor (FWR) shows unique kinematics of motion. It can produce a significantly higher aerodynamic efficiency and lift coefficient than insect-like flapping wings. However, due to the lack of controllable FWR aerial vehicles, the effect of different flapping parameters of the FWR on aerodynamic characteristics and efficiency remains to be evaluated experimentally. In this work, we conduct experimental studies to investigate the FWR’s lift performance based on our previous vehicle design, which has demonstrated sustained stable hover and maneuver. In particular, by using such flyable FWR as the test platform, the changes in attack angle of the wing, the torsion of wings, different neutral positions, different up and down flapping angles, and different flapping amplitudes, were studied respectively. CFD simulation was used as an auxiliary and supplementary means for validation. As a result, design essentials to lift maximization of the FWR are proposed. The result proves that changing the attack angle and the torsion of the wing will have a certain impact on the lift. In addition, the ideal lift force can be generated when the neutral position tend to zero degrees and the up and down flapping angles tend to be equal. With the growth of the flapping amplitude, the lift force increases continuously. These experimental results provide important design cues for maximizing lift and payload capability of FWR-MAVs. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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20 pages, 15860 KiB

Open AccessArticle

Numerical Investigation on Mechanisms of MHD Heat Flux Mitigation in Hypersonic Flows

by Zhifeng Zhou, Zhichao Zhang, Zhenxun Gao, Ke Xu and Chun-Hian Lee

Aerospace 2022, 9(10), 548; https://doi.org/10.3390/aerospace9100548 - 25 Sep 2022

Cited by 3 | Viewed by 2686

Abstract

Numerical simulations of hypersonic magnetohydrodynamics (MHD) flow over a typical sphere–cone blunt body are carried out based on the assumption of a low magnetic Reynolds number. The effects of an external dipole magnetic field on the surface heat flux are analyzed in detail, [...] Read more.

Numerical simulations of hypersonic magnetohydrodynamics (MHD) flow over a typical sphere–cone blunt body are carried out based on the assumption of a low magnetic Reynolds number. The effects of an external dipole magnetic field on the surface heat flux are analyzed in detail, and multiple mechanisms of the MHD heat flux mitigation are revealed systematically for the first time. The following is found: (1) The external magnetic field can effectively reduce the stagnation point heat flux, and the increase in the boundary layer thickness due to the effect of counter-flow Lorentz force, which is equivalent to adding an adverse pressure gradient, is the main reason. (2) In the head region of the blunt body, the relative surface heat flux shows a complex trend of rising and falling because there are two mechanisms which could produce the opposite effects on the surface heat flux. One is that the counter-flow Lorentz force results in an increase in the boundary layer thickness, and the other is that the Joule heating increases the static temperature behind the shock wave. (3) In the shoulder region of the blunt body, the Lorentz force component, normal to streamline, could change the flow direction of the fluid elements, causing the streamline to deviate from the wall or even separate, thus affecting the surface heat flux. (4) In the large area downstream of the blunt body, the surface heat flux could still be reduced by more than 30% due to the “upstream historical effect”. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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16 pages, 3314 KiB

Open AccessArticle

EEG Feature Analysis Related to Situation Awareness Assessment and Discrimination

by Chuanyan Feng, Shuang Liu, Xiaoru Wanyan, Hao Chen, Yuchen Min and Yilan Ma

Aerospace 2022, 9(10), 546; https://doi.org/10.3390/aerospace9100546 - 25 Sep 2022

Cited by 12 | Viewed by 2435

Abstract

In order to discriminate situation awareness (SA) levels on the basis of SA-sensitive electroencephalography (EEG) features, the high-SA (HSA) group and low-SA (LSA) groups, which are representative of two SA levels, were classified according to the situation awareness global assessment technology (SAGAT) scores [...] Read more.

In order to discriminate situation awareness (SA) levels on the basis of SA-sensitive electroencephalography (EEG) features, the high-SA (HSA) group and low-SA (LSA) groups, which are representative of two SA levels, were classified according to the situation awareness global assessment technology (SAGAT) scores measured in the multi-attribute task battery (MATB) II tasks. Furthermore, three types of EEG features, namely, absolute power, relative power, and slow-wave/fast-wave (SW/FW), were explored using spectral analysis. In addition, repeated analysis of variance (ANOVA) was conducted in three brain regions (frontal, central, and parietal) × three brain lateralities (left, middle, and right) × two SA groups (LSA and HSA) to explore SA-sensitive EEG features. The statistical results indicate a significant difference between the two SA groups according to SAGAT scores; moreover, no significant difference was found for the absolute power of four waves (delta (δ), theta (θ), alpha (α), and beta (β)). In addition, the LSA group had a significantly lower β relative power than the HSA group in central and partial regions. Lastly, compared with the HSA group, the LSA group had higher θ/β and (θ + α)/(α + β) in all analyzed brain regions, higher α/β in the parietal region, and higher (θ + α)/β in all analyzed regions except for the left and right laterality in the frontal region. The above SA-sensitive EEG features were fed into principal component analysis (PCA) and the Bayes method to discriminate different SA groups, and the accuracies were 83.3% for the original validation and 70.8% for the cross-validation. The results provide a basis for real-time assessment and discrimination of SA by investigating EEG features, thus contributing to monitoring SA decrement that might lead to threats to flight safety. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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20 pages, 3441 KiB

Open AccessArticle

Influence of Flow Rate Distribution on Combustion Instability of Hypergolic Propellant

by Yushan Gao, Bingbing Zhang, Jinbo Cheng, Jingxuan Li and Qingfei Fu

Aerospace 2022, 9(10), 543; https://doi.org/10.3390/aerospace9100543 - 23 Sep 2022

Cited by 5 | Viewed by 2113

Abstract

Combustion instability is the biggest threat to the reliability of liquid rocket engines, whose prediction and suppression are of great significance for engineering applications. To predict the stability of a combustion chamber with a hypergolic propellant, this work used the method of decoupling [...] Read more.

Combustion instability is the biggest threat to the reliability of liquid rocket engines, whose prediction and suppression are of great significance for engineering applications. To predict the stability of a combustion chamber with a hypergolic propellant, this work used the method of decoupling unsteady combustion and acoustic system. The turbulence is described by the Reynolds-averaged Navier–Stokes technique, and the interaction of turbulence and chemistry interaction is described by the eddy-dissipation model. By extracting the flame transfer function of the combustion field, the eigenvalues of each acoustic mode were obtained by solving the Helmholtz equation, thereby predicting the combustion stability for the combustion chamber. By predictions of the combustion chamber instability with different flow rate distributions, it was found that the increasing of inlet flow rate amplitude will improve the stability or instability of combustion. The combustion stability of the chamber was optimized when the flow rate distribution for the oxidant was set more uniform in the radial direction. The heterogeneity of the flow rate distribution in the circumferential direction is not recommended, considering that a homogeneous flow rate distribution in the circumferential direction is beneficial to the combustion stability of the chamber. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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25 pages, 1594 KiB

Open AccessArticle

Active Fault-Tolerant Control for Quadrotor UAV against Sensor Fault Diagnosed by the Auto Sequential Random Forest

by Shaojie Ai, Jia Song, Guobiao Cai and Kai Zhao

Aerospace 2022, 9(9), 518; https://doi.org/10.3390/aerospace9090518 - 17 Sep 2022

Cited by 13 | Viewed by 2576

Abstract

Active disturbance rejection control (ADRC) is a model-independent method widely used in passive fault-tolerant control of the quadrotor unmanned aerial vehicle. While ADRC’s effectiveness in actuator fault treatment has been proven, its tolerance to sensor faults requires improvements. In this paper, an ADRC-based [...] Read more.

Active disturbance rejection control (ADRC) is a model-independent method widely used in passive fault-tolerant control of the quadrotor unmanned aerial vehicle. While ADRC’s effectiveness in actuator fault treatment has been proven, its tolerance to sensor faults requires improvements. In this paper, an ADRC-based active fault-tolerant control (AFTC) scheme is proposed to control the flying attitude against sensor fault for reliability enhancement. Specifically, a semi-model-dependent state tracker is raised to reduce the influence of slow tracking, and accentuate the sensor fault even in varying maneuvers. Derived from the random forest, an enhanced method named auto sequential random forest is designed and applied to isolate and identify faults in real time. Once the tolerance compensation is generated with the fault information, a high-performance AFTC is achieved. The simulation results show that the proposed method can effectively follow the residual when a sensor fault and a change of maneuver occur concurrently. Precise fault information is obtained within 0.04 s, even for small faults on the noise level. The diagnosis accuracy is greater than 86.05% (100% when small faults are excluded), and the identification precision exceeds 97.25%. The short settling time (0.176 s when the small fault is excluded) and modest steady-state error validate the advanced and robust tolerance performance of the proposed AFTC method. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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20 pages, 4343 KiB

Open AccessArticle

Model Predictive Control-Based Attitude Control of Under-Actuated Spacecraft Using Solar Radiation Pressure

by Lei Jin and Yingjie Li

Aerospace 2022, 9(9), 498; https://doi.org/10.3390/aerospace9090498 - 7 Sep 2022

Cited by 1 | Viewed by 3409

Abstract

An attitude control strategy for an under-actuated spacecraft with two reaction wheels is proposed, using the active assistance of solar radiation pressure torque. By changing the rotation angles of the solar panels, the magnitude and direction of the solar radiation pressure torque is [...] Read more.

An attitude control strategy for an under-actuated spacecraft with two reaction wheels is proposed, using the active assistance of solar radiation pressure torque. By changing the rotation angles of the solar panels, the magnitude and direction of the solar radiation pressure torque is assumed to be adjustable in this paper. The attitude dynamic model of a rigid spacecraft with two reaction wheels and two solar panels is established and transformed into the form of a non-linear system. An integrated control scheme based on dual-mode model predictive control is proposed, which obtains the rotation speeds of the solar panels and the rotation accelerations of the reaction wheels directly as control quantities. Using this control method, not only are the constraints of rotation speeds and rotation angles of the panels satisfied, but also the robustness of the closed-loop system is ensured. The simulation results prove the validity of the proposed control method. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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Review

Jump to: Research

20 pages, 870 KiB

Open AccessReview

Survey on Mission Planning of Multiple Unmanned Aerial Vehicles

by Jia Song, Kai Zhao and Yang Liu

Aerospace 2023, 10(3), 208; https://doi.org/10.3390/aerospace10030208 - 23 Feb 2023

Cited by 18 | Viewed by 4346

Abstract

The task assignment issue and the path planning problem of Multiple Unmanned Aerial Vehicles (Multi-UAV) are collectively referred to as the Mission Planning Problem (MPP). This review article provides an update on the progress of the MPP on Multi-UAV. Focusing on the burning [...] Read more.

The task assignment issue and the path planning problem of Multiple Unmanned Aerial Vehicles (Multi-UAV) are collectively referred to as the Mission Planning Problem (MPP). This review article provides an update on the progress of the MPP on Multi-UAV. Focusing on the burning issue of task assignment, this paper focuses on the comparison of the characteristics of the mathematical programming method, heuristic algorithm, negotiation algorithm and neural networks. According to different constraints, trajectory planning can be divided into 2 dimension coverage, 3 dimension cooperation, and 4 dimension space-time cooperation. Combined with typical research, common collaborative guidance methods are introduced, and the key development direction of this field is prospected. The article shows that, although the MPP has been extensively studied, ongoing research is required. In particular, it is necessary to pay attention to the timeliness of the task assignment, the information coupling exists in MPP, and the problems caused by multiple constraints of Multi-UAV and environmental uncertainty. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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27 pages, 4629 KiB

Open AccessReview

A Review of Research on the Vacuum Plume

by Guobiao Cai, Lihui Liu, Bijiao He, Guilong Ling, Huiyan Weng and Weizong Wang

Aerospace 2022, 9(11), 706; https://doi.org/10.3390/aerospace9110706 - 11 Nov 2022

Cited by 23 | Viewed by 3761

Abstract

Chemical and electrical thrusters are generally utilized to control the attitude and orbit of spacecraft in aerospace. When they are firing, the exhaust expands into the vacuum environment, known as the vacuum plume. The plume flow can collide with spacecraft surfaces due to [...] Read more.

Chemical and electrical thrusters are generally utilized to control the attitude and orbit of spacecraft in aerospace. When they are firing, the exhaust expands into the vacuum environment, known as the vacuum plume. The plume flow can collide with spacecraft surfaces due to sufficient expansion, exerting adverse effects on the spacecraft, such as heating load, force/torque, contamination, and sputtering. Therefore, it is vital to investigate the vacuum plume to ensure the function and safety of the spacecraft. This review introduces the ground test and numerical simulation methods of the vacuum plume for chemical and electrical thrusters. The vacuum environment, invasive, and non-invasive (optical) measurements of the ground test are concluded. Numerical simulation of plume flow and its effects is exampled. The hybrid CFD-DSMC (computational fluid dynamics and direct simulation Monte Carlo) algorithm is employed to simulate the gas plume flow spanning continuum and transitional and free molecular flow regimes for chemical thrusters. By contrast, the PIC-DSMC (particle-in-cell plus direct simulation Monte Carlo) algorithm is used for the plasma plume flow containing charged particles exhausted by electrical thrusters. Moreover, the topics of fast prediction of the vacuum plume, plume–surface interaction, and plume–Lunar/Mars regolith interaction are proposed for future research. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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20 pages, 869 KiB

Open AccessReview

Vision-Based Autonomous Landing for the UAV: A Review

by Long Xin, Zimu Tang, Weiqi Gai and Haobo Liu

Aerospace 2022, 9(11), 634; https://doi.org/10.3390/aerospace9110634 - 22 Oct 2022

Cited by 34 | Viewed by 11321

Abstract

With the rapid development of the UAV, it is widely used in rescue and disaster relief, where autonomous landing is the key technology. Vision-based autonomous landing has the advantages of strong autonomy, low cost, and strong anti-interference ability. Moreover, vision navigation has higher [...] Read more.

With the rapid development of the UAV, it is widely used in rescue and disaster relief, where autonomous landing is the key technology. Vision-based autonomous landing has the advantages of strong autonomy, low cost, and strong anti-interference ability. Moreover, vision navigation has higher guidance and positioning accuracy combined with other navigation methods, such as GPS/INS. This paper summarizes the research results in the field of vision-based autonomous landing for the UAV, and divides it into static, dynamic, and complex scenarios according to the type of landing destination. Among them, the static scenario includes two categories: cooperative targets and natural landmarks; the dynamic scenario is divided into two categories: vehicle-based autonomous landing and ship-based autonomous landing. The key technologies are summarized, compared, and analyzed and the future development trends are pointed out, which can provide a reference for the research on vision-based autonomous landing of UAVs. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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22 pages, 8257 KiB

Open AccessReview

A Review on Solid-State-Based Additive Friction Stir Deposition

by Hongrui Dong, Xiaoqiang Li, Ke Xu, Zhenyu Zang, Xin Liu, Zongjiang Zhang, Wenlong Xiao and Yong Li

Aerospace 2022, 9(10), 565; https://doi.org/10.3390/aerospace9100565 - 29 Sep 2022

Cited by 20 | Viewed by 8427

Abstract

Additive manufacturing (AM) is an important technology in Industry 4.0. In recent years, solid-state-based additive friction stir deposition (AFSD) has attracted much attention, as it can avoid the inherent defect of melting and rapid solidification in electron beam-based or laser-based AM technologies. The [...] Read more.

Additive manufacturing (AM) is an important technology in Industry 4.0. In recent years, solid-state-based additive friction stir deposition (AFSD) has attracted much attention, as it can avoid the inherent defect of melting and rapid solidification in electron beam-based or laser-based AM technologies. The macro and micro laws, finite element simulation, and engineering application technology of the AFSD process are still in their early stages. This paper mainly reviews the equipment, mechanism, the effect of process parameters on macro/micro characters, and the engineering applications of the AFSD process. Further, based on the complex loading conditions during the AFSD process, some perspectives are proposed, including the characterization method, unified constitutive model, novel composite manufacturing technology, and systematic study of the AFSD process. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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32 pages, 4993 KiB

Open AccessReview

A Review of Non-Destructive Evaluation (NDE) Techniques for Residual Stress Profiling of Metallic Components in Aircraft Engines

by Zhaoyu Shao, Chengcheng Zhang, Yankai Li, Hai Shen, Dehan Zhang, Xudong Yu and Ying Zhang

Aerospace 2022, 9(10), 534; https://doi.org/10.3390/aerospace9100534 - 21 Sep 2022

Cited by 9 | Viewed by 4534

Abstract

Residual stresses are one of the main factors determining the failure of aircraft engine materials. It is not possible to reliably and accurately predict the remaining service life of aircraft engine components without properly accounting for the presence of residual stresses. The absolute [...] Read more.

Residual stresses are one of the main factors determining the failure of aircraft engine materials. It is not possible to reliably and accurately predict the remaining service life of aircraft engine components without properly accounting for the presence of residual stresses. The absolute level and spatial distribution of the residual stress is uncertain in aircraft engines because the residual stress profile is highly susceptible to variations in the manufacturing process. In addition, residual stresses keep evolving under complex thermal-mechanical loadings. Non-destructive techniques are desired by the aerospace industries for the regular monitoring of subsurface residual stress profile in aircraft engine components. The insufficient penetrating capability of the only currently available non-destructive residual stress assessment technique X-ray diffraction has prompted an active search for alternative non-destructive techniques. This paper provides an overview of the principle, practical applications, advantages, and limitations of four categories of nondestructive (diffraction, ultrasonic, and electromagnetic) techniques for residual stress profiling of metallic components in aircraft engines. Full article

(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)

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