Journal Description
Aerospace
Aerospace
is a peer-reviewed, open access journal of aeronautics and astronautics published monthly online by MDPI. The European Aeronautics Science Network (EASN), and the ECATS International Association are affiliated with Aerospace and their members receive a discount on the article processing charges.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, and other databases.
- Journal Rank: JCR - Q1 (Engineering, Aerospace) / CiteScore - Q2 (Aerospace Engineering)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 22.3 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Companion journal: Astronomy.
Impact Factor:
2.6 (2022);
5-Year Impact Factor:
2.6 (2022)
Latest Articles
Influence of Rotor Inflow, Tip Loss, and Aerodynamics Modeling on the Maximum Thrust Computation in Hover
Aerospace 2024, 11(5), 357; https://doi.org/10.3390/aerospace11050357 (registering DOI) - 29 Apr 2024
Abstract
Comprehensive rotorcraft simulation codes are the workhorses for designing and simulating helicopters and their rotors under steady and unsteady operating conditions. These codes are also used to predict helicopters’ limits as they approach rotor stall conditions. This paper focuses on the prediction of
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Comprehensive rotorcraft simulation codes are the workhorses for designing and simulating helicopters and their rotors under steady and unsteady operating conditions. These codes are also used to predict helicopters’ limits as they approach rotor stall conditions. This paper focuses on the prediction of maximum rotor thrust when hovering (due to stall limits) and the thrust and power characteristics when the collective control angle is further increased. The aerodynamic factors that may significantly affect the results are as follows: steady vs. unsteady aerodynamics, steady vs. dynamic stall, blade tip losses, curvature flow, yaw angle, inflow model, and blade-vortex interaction. The inflow model and tip losses are found to be the most important factors. For real-world applications vortex-based inflow models are considered the best choice, as they reflect the blade circulation distribution within the inflow distribution. Because the focus is on the impact of aerodynamic modeling on rotor stall, the blade design and its flexibility are intentionally not considered.
Full article
(This article belongs to the Special Issue Vertical Lift: Rotary- and Flapping-Wing Flight)
Open AccessArticle
Analysis of the Synchronized Locking Dynamic Characteristics of a Dual-Sidestay Main Landing Gear Retraction Mechanism
by
Zhipeng Zhang, Shengxiao Wu, He Zhu, Hong Nie and Xiaohui Wei
Aerospace 2024, 11(5), 356; https://doi.org/10.3390/aerospace11050356 (registering DOI) - 29 Apr 2024
Abstract
As an advanced design technology for large wide-body airliners, the three-dimensional (3D) dual-sidestay (DSS) landing gear retraction mechanism can share the ground loads transferred by the landing gear, reducing the load on the wings. However, the addition of a strut system may significantly
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As an advanced design technology for large wide-body airliners, the three-dimensional (3D) dual-sidestay (DSS) landing gear retraction mechanism can share the ground loads transferred by the landing gear, reducing the load on the wings. However, the addition of a strut system may significantly impact the synchronous locking performance of the landing gear with extremely high sensitivity. To study this impact pattern, both a rigid–flexible-coupling dynamic model of DSS landing gear considering joint clearance and node deviation and a synchronous locking test platform are established in this paper, and the simulation model is validated through the experimental results. Based on the simulation model, this paper conducts a detailed study on the influence of different node deviations and joint clearance on the synchronous locking dynamic characteristics of the DSS landing gear. The results show that, as the node deviation increases, the locking of the lock link gradually lags until one side cannot be fully locked; the structural clearance has a smaller impact on the synchronous locking of the landing gear. The feasible region of parameters satisfying the synchronous locking condition is given, which provides a basis and support for the parameter design of dual-sidestay retraction mechanisms.
Full article
(This article belongs to the Section Aeronautics)
Open AccessArticle
Improvements in Probabilistic Strategies and Their Application to Turbomachinery
by
Andriy Prots, Matthias Voigt and Ronald Mailach
Aerospace 2024, 11(5), 355; https://doi.org/10.3390/aerospace11050355 (registering DOI) - 29 Apr 2024
Abstract
This paper discusses various strategies for probabilistic analysis, with a focus on typical engineering applications. The emphasis is on sampling methods and sensitivity analysis. A new sampling method, Latinized particle sampling, is introduced and compared to existing sampling methods. While it can increase
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This paper discusses various strategies for probabilistic analysis, with a focus on typical engineering applications. The emphasis is on sampling methods and sensitivity analysis. A new sampling method, Latinized particle sampling, is introduced and compared to existing sampling methods. While it can increase the quality of surrogate models, an optimized Latin hypercube sampling is mostly preferable as it shows slightly better results. In sensitivity analysis, the difficulty lies in correlated input variables, which are typical in engineering applications. First, the Sobol indices and the Shapley values are explained using an intuitive example. Then, the modified coefficient of importance is introduced as a new sensitivity measure, which can be used to reliably identify input variables without functional influence. Finally, these results are applied to a turbomachinery test case. In this case, the flow field of a compressor row is investigated, where the blades are subjected to geometric variability. The profile parameters used to describe the geometric variability are correlated. It is shown that the variability of the maximum camber and the thickness of the leading edge have a decisive influence on the variability of the isentropic efficiency.
Full article
(This article belongs to the Special Issue Data-Driven Aerodynamic Modeling)
Open AccessArticle
CFD Simulations and Phenomenological Modelling of Aerodynamic Stall Hysteresis of NACA 0018 Wing
by
Mohamed Sereez, Nikolay Abramov and Mikhail Goman
Aerospace 2024, 11(5), 354; https://doi.org/10.3390/aerospace11050354 (registering DOI) - 29 Apr 2024
Abstract
Computational simulations of three-dimensional flow around a NACA 0018 wing with an aspect ratio of were carried out by using the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with the Shear-Stress Transport turbulence model closure. Simulations were performed to capture aerodynamic
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Computational simulations of three-dimensional flow around a NACA 0018 wing with an aspect ratio of were carried out by using the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with the Shear-Stress Transport turbulence model closure. Simulations were performed to capture aerodynamic stall hysteresis by using the developed pseudo-transient continuation (PTC) method based on a dual-time step approach in CFD OpenFOAM code. The flow was characterized by incompressible Mach number and moderate Reynolds number . The results obtained indicate the presence of noticeable aerodynamic hysteresis in the static dependencies of the force and moment coefficients, as well as the manifestation of bi-stable flow separation patterns, accompanied by the development of asymmetry in the stall zone. The URANS simulation results are in good agreement with the experimental data obtained for the NACA 0018 finite-aspect-ratio wing in the low-speed wind tunnel under the same test conditions. A new phenomenological bifurcation model of aerodynamic stall hysteresis under static and dynamic conditions is formulated and is proven to be able to closely match the experimental data.
Full article
(This article belongs to the Special Issue Recent Advances in Applied Aerodynamics)
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Open AccessArticle
Experimental Validation of a Passive-Adaptive Slat Concept and Characterization under Sinusoidal Fluctuations in the Angle of Attack
by
Piyush Singh, Florian Schmidt, Jochen Wild, Johannes Riemenschneider, Joachim Peinke and Michael Hölling
Aerospace 2024, 11(5), 353; https://doi.org/10.3390/aerospace11050353 (registering DOI) - 29 Apr 2024
Abstract
This article presents an experimental investigation of a passive-adaptive slat concept, an aerodynamic control mechanism aimed at avoiding separation in the inwards region of a horizontal axis wind turbine blade. The passive-adaptive slat is designed to autonomously adjust its position due to the
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This article presents an experimental investigation of a passive-adaptive slat concept, an aerodynamic control mechanism aimed at avoiding separation in the inwards region of a horizontal axis wind turbine blade. The passive-adaptive slat is designed to autonomously adjust its position due to the aerodynamic forces acting on it, without the need of any active control system or external power source. The slat opens when the angle of attack increases beyond a certain threshold so that stall is delayed and closes for smaller angles of attack to increase the lift-to-drag ratio of the airfoil. A thorough aerodynamic characterisation of the passive-adaptive slat is performed in the wind tunnel followed by testing it under different sinusoidal inflows generated by a 2D active grid. It is observed that the slat system is able to leverage the advantages of both a clean airfoil and an airfoil with a fixed slat. It has the capability of delaying stalls for higher angles of attack, as well as having higher lift-to-drag ratio for lower angles of attack. It is also observed that, for fluctuating inflow, the passive-adaptive slat is able to achieve similar mean lift values as an airfoil with fixed slat while showing significant reduction in the lift fluctuations.
Full article
(This article belongs to the Special Issue Gust Influences on Aerospace)
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Open AccessArticle
Numerical Simulation of Water Film Flow and Breakup on Anti-Icing Surface
by
Changxian Zhang, Lei Liu, Yaping Hu and Pengfei Li
Aerospace 2024, 11(5), 352; https://doi.org/10.3390/aerospace11050352 (registering DOI) - 29 Apr 2024
Abstract
The flow and morphological characteristics of liquid water on the icing and anti-icing surfaces of aircraft are closely related to the icing characteristics and anti-icing surface temperature distribution. To predict the flow and breakup characteristics of a water film, a 3D model of
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The flow and morphological characteristics of liquid water on the icing and anti-icing surfaces of aircraft are closely related to the icing characteristics and anti-icing surface temperature distribution. To predict the flow and breakup characteristics of a water film, a 3D model of continuous water film flow and a model of water film breakup into rivulets on an anti-icing surface were constructed based on the icing model, and the corresponding methods for solving the models were developed. Using the NACA0012 airfoil as a simulation object, the changing characteristics of height and velocity for a continuous water film with time and the morphological characteristics of rivulets formed from the breakup of a continuous water film were simulated numerically. The results indicate that, with an increase in inflow velocity, the time required for the water film to completely cover the surface and reach stability decreases. Downstream in the water droplet impact zone, the calculated values of continuous water film height align well with experiments, as well as the stream height at the continuous water film rupture location with the experimental values. With the reasonable contact angle, the calculation error of the stream width is within 10%.
Full article
(This article belongs to the Special Issue Deicing and Anti-Icing of Aircraft (Volume III))
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Open AccessArticle
Dense Feature Matching for Hazard Detection and Avoidance Using Machine Learning in Complex Unstructured Scenarios
by
Daniel Posada and Troy Henderson
Aerospace 2024, 11(5), 351; https://doi.org/10.3390/aerospace11050351 (registering DOI) - 28 Apr 2024
Abstract
Exploring the Moon and Mars are crucial steps in advancing space exploration. Numerous missions aim to land and research in various lunar locations, some of which possess challenging surfaces with unchanging features. Some of these areas are cataloged as lunar light plains. Their
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Exploring the Moon and Mars are crucial steps in advancing space exploration. Numerous missions aim to land and research in various lunar locations, some of which possess challenging surfaces with unchanging features. Some of these areas are cataloged as lunar light plains. Their main characteristics are that they are almost featureless and reflect more light than other lunar surfaces. This poses a challenge during navigation and landing. This paper compares traditional feature matching techniques, specifically scale-invariant feature transform and the oriented FAST and rotated BRIEF, and novel machine learning approaches for dense feature matching in challenging, unstructured scenarios, focusing on lunar light plains. Traditional feature detection methods often need help in environments characterized by uniform terrain and unique lighting conditions, where unique, distinguishable features are rare. Our study addresses these challenges and underscores the robustness of machine learning. The methodology involves an experimental analysis using images that mimic lunar-like landscapes, representing these light plains, to generate and compare feature maps derived from traditional and learning-based methods. These maps are evaluated based on their density and accuracy, which are critical for effective structure-from-motion reconstruction commonly utilized in navigation for landing. The results demonstrate that machine learning techniques enhance feature detection and matching, providing more intricate representations of environments with sparse features. This improvement indicates a significant potential for machine learning to boost hazard detection and avoidance in space exploration and other complex applications.
Full article
(This article belongs to the Special Issue Advances in Entry, Descent, and Landing (EDL) for Planetary Exploration)
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Open AccessArticle
Dynamic Behavior of Satellite and Its Solar Arrays Subject to Large-Scale Antenna Deployment Shock
by
Jie Zhang, Pengfei Wu, Qinghu Han, Xin Wei and Yi Duan
Aerospace 2024, 11(5), 349; https://doi.org/10.3390/aerospace11050349 (registering DOI) - 28 Apr 2024
Abstract
Satellites should be equipped with more and more deployable, large, flexible appendages to improve their service efficiency and reduce launch costs. The spring-driven deployment method of flexible appendages has been widely applied and generates great instantaneous shock loads on satellites, maybe affecting the
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Satellites should be equipped with more and more deployable, large, flexible appendages to improve their service efficiency and reduce launch costs. The spring-driven deployment method of flexible appendages has been widely applied and generates great instantaneous shock loads on satellites, maybe affecting the safety of other flexible appendages, but the current related investigations for satellites with multiple large flexible appendages are insufficient. In this study, the deployment test of the antenna itself was conducted, and the attitude changes in a satellite during antenna deployment were telemetered. Then, a related dynamical model of the satellite was established and verified by the telemetry values of the satellite. Finally, the shock mechanism transmitted to solar arrays was analyzed, and the effect of solar array attitude was discussed. The results show that the simulated method of antenna deployment equivalent to the shock loads tested was thought to be efficient, though it could cause a small non-zero constant of the simulated angular velocities in the antenna deployment direction. The shock-induced moments, except the rotation direction of the solar array drive assembly (SADA), should be highlighted for the antenna deployment dynamic design of satellites, and the solar array attitude has few effects on the shock-induced loads at the SADA.
Full article
(This article belongs to the Special Issue Deployable Space Structures and Mechanisms)
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A Spacecraft Onboard Autonomous Task Scheduling Method Based on Hierarchical Task Network-Timeline
by
Junwei Zhang and Liangqing Lyu
Aerospace 2024, 11(5), 350; https://doi.org/10.3390/aerospace11050350 (registering DOI) - 27 Apr 2024
Abstract
To address the inherent challenges of deep space exploration, such as communication delays and the unpredictability of spacecraft environments, this study focuses on enhancing spacecraft adaptability and autonomy, which are essential for Autonomous Space Scientific Exploration. A pivotal aspect of this endeavor is
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To address the inherent challenges of deep space exploration, such as communication delays and the unpredictability of spacecraft environments, this study focuses on enhancing spacecraft adaptability and autonomy, which are essential for Autonomous Space Scientific Exploration. A pivotal aspect of this endeavor is the advancement of spacecraft task scheduling, which is integral to increasing spacecraft autonomy. Current research in this domain predominantly revolves around mission timing planning and is primarily executed from ground stations. However, these plans often lack the granularity required for direct implementation by spacecraft. In response, our study proposes an innovative approach to augment spacecraft autonomy, introducing a method that articulately describes mission objectives and resource information. We designed a novel hierarchical task network-timeline (HTN-T) algorithm, an amalgamation of the HTN scheduling method and the distinctive elements of existing research. This algorithm addresses time constraints through horizontal and vertical expansions, building upon the resolution of logical constraints found in conventional planning methods. Furthermore, it introduces a priority-based strategy for resolving resource conflicts in spacecraft tasks. This algorithm is substantiated through validation, including proof-of-principle demonstrations and assessments within a Space–ground Collaborative Management and Control System encompassing both ground and spacecraft operations. The findings indicate that our proposed algorithm achieves high rates of scheduling success and operational efficiency within a feasible timeframe, thus effectively navigating the complexities of autonomous spacecraft task scheduling.
Full article
(This article belongs to the Section Astronautics & Space Science)
Open AccessArticle
A Study of Lunar Regolith Obtained during the Apollo and Luna Space Programs Based on Principal Component Analysis
by
Jacek Katzer, Janusz Kobaka and Karol Seweryn
Aerospace 2024, 11(5), 348; https://doi.org/10.3390/aerospace11050348 (registering DOI) - 27 Apr 2024
Abstract
In this study, a modern principal component analysis (PCA) of the chemical properties of lunar soils was conducted. American and Soviet results acquired during the Apollo and Luna missions, respectively, were analyzed and compared. The chemical composition of the lunar soil was the
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In this study, a modern principal component analysis (PCA) of the chemical properties of lunar soils was conducted. American and Soviet results acquired during the Apollo and Luna missions, respectively, were analyzed and compared. The chemical composition of the lunar soil was the focus of our analysis, the main aim of which was to assess any possible differences between the results provided by the missions in question. The results were visualized in two- and three-dimensional spaces. The use of PCA virtual variables enabled the chemical composition of the lunar soil to be fully visualized—something impossible to achieve using traditional techniques—and key similarities and differences among the properties of the lunar soil samples were determined. The sources of any differences were then conceptualized. The work reported in this paper offers new directions for future studies, especially research into the design of new lunar soil simulants for lunar construction and civil engineering programs.
Full article
(This article belongs to the Special Issue Planetary Exploration)
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Open AccessArticle
Empirical Modeling of Subcritical Hopf Bifurcation of Thermoacoustic Stirling Engine
by
Chuan-Heng Lai and Shu-Han Hsu
Aerospace 2024, 11(5), 347; https://doi.org/10.3390/aerospace11050347 - 26 Apr 2024
Abstract
This study models the subcritical Hopf bifurcation in thermoacoustic Stirling engines using the Stuart–Landau model, highlighting the role of nonlinear dynamics. By inducing self-sustained oscillations and measuring pressure fluctuations across different temperature gradients imposed on the regenerator, we reveal the engine’s transition to
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This study models the subcritical Hopf bifurcation in thermoacoustic Stirling engines using the Stuart–Landau model, highlighting the role of nonlinear dynamics. By inducing self-sustained oscillations and measuring pressure fluctuations across different temperature gradients imposed on the regenerator, we reveal the engine’s transition to a nonlinear domain, characterized by heightened oscillation amplitudes and unique periodic patterns. Interpreted Landau constants and growth rates illuminate the stabilizing effects of nonlinear dynamics, demonstrating the Stuart–Landau model’s applicability in thermoacoustic engine analysis. Our research confirms that this empirically refined model reliably describes oscillation amplitudes and transient phenomena, contributing valuable perspectives for advancing thermoacoustic engine design and operational understanding.
Full article
(This article belongs to the Special Issue Predicting the Onset and Control of Thermoacoustics)
Open AccessArticle
Damage Effects and Mechanisms of High-Power Microwaves on Double Heterojunction GaN HEMT
by
Zhenyang Ma, Dexu Liu, Shun Yuan, Zhaobin Duan and Zhijun Wu
Aerospace 2024, 11(5), 346; https://doi.org/10.3390/aerospace11050346 - 26 Apr 2024
Abstract
In this paper, simulation modeling was carried out using Sentaurus Technology Computer-Aided Design. Two types of high electron mobility transistors (HEMT), an AlGaN/GaN/AlGaN double heterojunction and AlGaN/GaN single heterojunction, were designed and compared. The breakdown characteristics and damage mechanisms of the two
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In this paper, simulation modeling was carried out using Sentaurus Technology Computer-Aided Design. Two types of high electron mobility transistors (HEMT), an AlGaN/GaN/AlGaN double heterojunction and AlGaN/GaN single heterojunction, were designed and compared. The breakdown characteristics and damage mechanisms of the two devices under the injection of high-power microwaves (HPM) were studied. The variation in current density and peak temperature inside the device was analyzed. The effect of Al components at different layers of the device on the breakdown of HEMTs is discussed. The effect and law of the power damage threshold versus pulse width when the device was subjected to HPM signals was verified. It was shown that the GaN HEMT was prone to thermal breakdown below the gate, near the carrier channels. A moderate increase in the Al component can effectively increased the breakdown voltage of the device. Compared with the single heterojunction, the double heterojunction HEMT devices were more sensitive to Al components. The high domain-limiting characteristics effectively inhibited the overflow of channel electrons into the buffer layer, which in turn regulated the current density inside the device and improved the temperature distribution. The leakage current was reduced and the device switching characteristics and breakdown voltage were improved. Moreover, the double heterojunction device had little effect on HPM power damage and high damage resistance. Therefore, a theoretical foundation is proposed in this paper, indicating that double heterojunction devices are more stable compared to single heterojunction devices and are more suitable for applications in aviation equipment operating in high-frequency and high-voltage environments. In addition, double heterojunction GaN devices have higher radiation resistance than SiC devices of the same generation.
Full article
(This article belongs to the Special Issue Lab-on-a-Chip Devices and Systems for Microgravity Simulation and Aerospace Applications)
Open AccessArticle
Rapid Tracking Satellite Servo Control for Three-Axis Satcom-on-the-Move Antenna
by
Jiao Ren, Xiaoxiang Ji, Lei Han, Jianghong Li, Shubiao Song and Yafeng Wu
Aerospace 2024, 11(5), 345; https://doi.org/10.3390/aerospace11050345 - 26 Apr 2024
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To overcome the possible gimbal lock problem of the dual-axis satcom-on-the-move (SOTM) antenna, a three-axis tracking satellite SOTM antenna structure appears. The three-axis SOTM antenna is realized by adding a roll axis to the azimuth axis and pitch axis in the dual-axis SOTM
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To overcome the possible gimbal lock problem of the dual-axis satcom-on-the-move (SOTM) antenna, a three-axis tracking satellite SOTM antenna structure appears. The three-axis SOTM antenna is realized by adding a roll axis to the azimuth axis and pitch axis in the dual-axis SOTM structure. There is coupling among the azimuth axis, pitch axis and roll axis in the mechanical structure of the three-axis SOTM antenna, which makes the kinematic modeling of the antenna difficult. This paper introduces a three-axis SOTM antenna kinematic modeling method based on the modified Denavit–Hartenberg (MDH) method, named the new modified Denavit–Hartenberg (NMDH) method. In order to meet the modeling requirements of the MDH method, the NMDH method adds virtual coordinate systems and auxiliary coordinate systems to the three-axis SOTM antenna and obtains the kinematic model of the three-axis SOTM antenna. During the motion of the carrier, the SOTM antenna needs to adjust the antenna pointing in real time according to the changes of the location and attitude of the moving carrier. Therefore, this paper designs a servo control system based on the active disturbance rejection controller (ADRC), introducing a smooth and continuous ADRC function to enhance the tracking speed of the servo control system and reduce the overshoot of the output response. Finally, system experiments were carried out with a 60 cm caliber three-axis SOTM antenna. The experiment results show that the proposed servo control method achieves higher antenna tracking satellite accuracy and better communication effects.
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Open AccessArticle
DBO-CNN-BiLSTM: Dung Beetle Optimization Algorithm-Based Thrust Estimation for Micro-Aero Engine
by
Baijun Lei, Haozhong Huang, Guixin Chen, Jianguo Liang and Huigui Long
Aerospace 2024, 11(5), 344; https://doi.org/10.3390/aerospace11050344 - 26 Apr 2024
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Thrust constitutes a pivotal performance parameter for aircraft engines. Thrust, being an indispensable parameter in control systems, has garnered significant attention, prompting numerous scholars to propose various methods and algorithms for its estimation. However, research methods for estimating the thrust of the micro-turbojet
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Thrust constitutes a pivotal performance parameter for aircraft engines. Thrust, being an indispensable parameter in control systems, has garnered significant attention, prompting numerous scholars to propose various methods and algorithms for its estimation. However, research methods for estimating the thrust of the micro-turbojet engines used in unmanned aerial vehicles are relatively scarce. Therefore, this paper proposes a thrust estimator for micro-turbojet engines based on DBO (dung beetle optimization) utilizing bidirectional long short-term memory (BiLSTM) and a convolutional neural network (CNN). Furthermore, the efficacy of the proposed model is further validated through comparative analysis with others in this paper.
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Open AccessArticle
Flight Trainee Performance Evaluation Using Gradient Boosting Decision Tree, Particle Swarm Optimization, and Convolutional Neural Network (GBDT-PSO-CNN) in Simulated Flights
by
Lei Shang, Haibo Wang, Haiqing Si, Yonghu Wang, Ting Pan, Haibo Liu and Yixuan Li
Aerospace 2024, 11(5), 343; https://doi.org/10.3390/aerospace11050343 (registering DOI) - 25 Apr 2024
Abstract
Flight simulation training is one of the most important methods in early-stage civil aviation flight training. In this regard, flight simulation competitions are effective tools for evaluating the flight skills of trainees. In this study, a model is developed for evaluating the flight
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Flight simulation training is one of the most important methods in early-stage civil aviation flight training. In this regard, flight simulation competitions are effective tools for evaluating the flight skills of trainees. In this study, a model is developed for evaluating the flight skills of trainees by integrating GBDT (Gradient Boosting Decision Tree), PSO (Particle Swarm Optimization), and CNNs (Convolutional Neural Networks). Flight data from simulations is employed for model training. Initially, performance data and scores are gathered from a simulated flight competition platform. The GBDT algorithm is then applied to filter and identify essential flight parameters from the collected data. Subsequently, the PSO-CNN model is utilized to train on the extracted flight parameters. The proposed GBDT-PSO-CNN model achieves a recognition rate of 93.8% on the test dataset. This assessment system is of significant importance for improving the specific maneuvering skill level of flight trainees.
Full article
(This article belongs to the Section Air Traffic and Transportation)
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Open AccessArticle
Investigation of the Internal Flow Characteristics of a Tiltrotor Aircraft Engine Inlet in a Gust Environment
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Haicheng Zhu, Xiaoming He, Yue Zhang, Daishu Cheng, Ziyun Wang, Yufeng Huang and Huijun Tan
Aerospace 2024, 11(5), 342; https://doi.org/10.3390/aerospace11050342 - 25 Apr 2024
Abstract
In the vertical take-off and landing (VTOL) state of tiltrotor aircraft, the inlet entrance encounters the incoming airflow at a 90° attack angle, resulting in highly complex internal flow characteristics that are extremely susceptible to gusts. Meanwhile, the flow quality at the inlet
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In the vertical take-off and landing (VTOL) state of tiltrotor aircraft, the inlet entrance encounters the incoming airflow at a 90° attack angle, resulting in highly complex internal flow characteristics that are extremely susceptible to gusts. Meanwhile, the flow quality at the inlet exit directly affects the performance of the aircraft’s engine. This work made use of an unsteady numerical simulation method based on sliding meshes to investigate the internal flow characteristics of the inlet during the hover state of a typical tiltrotor aircraft and the effects of head-on gusts on the inlet’s aerodynamic characteristics. The results show that during the hover state, the tiltrotor aircraft inlet features three pairs of transverse vortices and one streamwise vortex at the aerodynamic interface plane (AIP). The transverse vortices generated due to the rotational motion of the air have the largest scale and exert the strongest influence on the inlet’s performance, which is characterized by pronounced unsteady features. Additionally, strong unsteady characteristics are present within the inlet. Head-on gusts mainly affect the mechanical energy and non-uniformity of the air sucked into the inlet by influencing the direction of the rotor’s induced slipstream, thereby impacting the performance of the inlet. The larger head-on gusts have beneficial effects on the performance of the inlet. When the gust velocity reaches 12 m/s, there is a 1.01% increase in the total pressure recovery (σ) of the inlet, a 25.72% decrease in the circumferential distortion index (DC60), and a reduction of 62.84% in the area where the swirl angle |α| exceeds 15°. Conversely, when the gust velocity of head-on gusts reaches 12 m/s in the opposite direction, the inlet’s total pressure recovery decreases by 1.13%, the circumferential distortion index increases by 14.57%, and the area where the swirl angle exceeds 15° increases by 69.59%, adversely affecting the performance of the inlet. Additionally, the presence of gusts alters the unsteady characteristics within the inlet.
Full article
(This article belongs to the Special Issue Gust Influences on Aerospace)
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Open AccessArticle
Redundant Space Manipulator Autonomous Guidance for In-Orbit Servicing via Deep Reinforcement Learning
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Matteo D’Ambrosio, Lorenzo Capra, Andrea Brandonisio, Stefano Silvestrini and Michèle Lavagna
Aerospace 2024, 11(5), 341; https://doi.org/10.3390/aerospace11050341 - 25 Apr 2024
Abstract
The application of space robotic manipulators and heightened autonomy for In-Orbit Servicing (IOS) represents a paramount pursuit for leading space agencies, given the substantial threat posed by space debris to operational satellites and forthcoming space endeavors. This work presents a guidance algorithm based
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The application of space robotic manipulators and heightened autonomy for In-Orbit Servicing (IOS) represents a paramount pursuit for leading space agencies, given the substantial threat posed by space debris to operational satellites and forthcoming space endeavors. This work presents a guidance algorithm based on Deep Reinforcement Learning (DRL) to solve for space manipulator path planning during the motion-synchronization phase with the mission target. The goal is the trajectory generation and control of a spacecraft equipped with a 7-Degrees of Freedom (7-DoF) robotic manipulator, such that its end effector remains stationary with respect to the target point of capture. The Proximal Policy Optimization (PPO) DRL algorithm is used to optimize the manipulator’s guidance law, and the autonomous agent generates the desired joint rates of the robotic arm, which are then integrated and passed to a model-based feedback linearization controller. The agent is first trained to optimize its guidance policy and then tested extensively to validate the results against a simulated environment representing the motion synchronization scenario of an IOS mission.
Full article
(This article belongs to the Special Issue Advances on Autonomous Navigation for Spacecraft Proximity Operations and Formation Flying: Algorithms Development and Verification Methods)
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Ascending Performance of Scientific Balloons with Buoyant Gas–Air Mixture Inflation for Designated Ceiling Height
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Shenghong Cao, Yanchu Yang, Hangyue Zhang, Rong Zhao, Rongchen Zhu, Donghui Zhang and Lin Song
Aerospace 2024, 11(5), 340; https://doi.org/10.3390/aerospace11050340 - 25 Apr 2024
Abstract
This paper aims to investigate a new method that uses buoyant gas mixed with air to control the floating height of scientific balloons. Firstly, the static characteristics and thermophysical properties of mixed-gas balloons are analyzed. Subsequently, the inflation model and the thermal-dynamic coupled
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This paper aims to investigate a new method that uses buoyant gas mixed with air to control the floating height of scientific balloons. Firstly, the static characteristics and thermophysical properties of mixed-gas balloons are analyzed. Subsequently, the inflation model and the thermal-dynamic coupled model are established. Furthermore, based on theoretical research, a GUI program is compiled to simulate the ascent of mixed-gas balloons. Finally, flight tests are conducted. As the balloon volume expands to the maximum, the vertical velocity begins to decay and eventually oscillates around 0 m/s, which is consistent with the simulation. In addition, there is a noticeable shift in which the balloon starts to float after climbing to the target altitude, and the difference values between the test and the simulation are less than 350 m. Moreover, the trajectory results are similar to the prediction, and the errors of the end position are less than 2.5 km in horizontal distance. Consequently, this paper provides guidance for balloon-designated ceiling height technology which can allow a single balloon system to be used for tests at multiple heights.
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(This article belongs to the Special Issue Mission Analysis and Design of Lighter-than-Air Flying Vehicles (2nd Edition))
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Open AccessArticle
A Weighted Feature Fusion Model for Unsteady Aerodynamic Modeling at High Angles of Attack
by
Wenzhao Dong, Xiaoguang Wang, Qi Lin, Chuan Cheng and Liangcong Zhu
Aerospace 2024, 11(5), 339; https://doi.org/10.3390/aerospace11050339 - 25 Apr 2024
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Unsteady aerodynamic prediction at high angles of attack is of great importance to the design and development of advanced fighters. In this paper, a weighted feature fusion model (WFFM) that combines the state-space model and neural networks is proposed to build an unsteady
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Unsteady aerodynamic prediction at high angles of attack is of great importance to the design and development of advanced fighters. In this paper, a weighted feature fusion model (WFFM) that combines the state-space model and neural networks is proposed to build an unsteady aerodynamic model for the precise simulation and control of post-stall maneuvers. In the proposed model, the influences of the physical model on neural networks are considered and adjusted by introducing a standardization layer and a new weighting method. A long short-term memory (LSTM) network is used to fuse two mappings: one from flight states to aerodynamic loads, and the other from low-fidelity data to high-fidelity data. Data from wind tunnel oscillation experiments at high angles of attack using a new kind of wire-driven parallel robot and the traditional tail support are used for verifying the proposed aerodynamic model. The output of the WFFM is also compared with predictions from other models, such as the state-space model, single LSTM model, and feature fusion model not including a feature weighting layer. Results demonstrate improved accuracy of the proposed model in the interpolation and extrapolation tests. Furthermore, the WFFM is applied to the flight simulation of F-16 with different control inputs. Compared with conventional models, the WFFM shows improved accuracy and better generalization capability.
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Open AccessArticle
Numerical Investigations on the Effects of Dome Cooling Air Flow on Combustion Characteristics and Emission Behavior in a Can-Type Gas Turbine Combustor
by
Chenzhen Ji, Wentao Shi, Enlei Ke, Jiaying Cheng, Tong Zhu, Chao Zong and Xinyan Li
Aerospace 2024, 11(5), 338; https://doi.org/10.3390/aerospace11050338 - 25 Apr 2024
Abstract
To meet the requirements of achieving higher efficiency and lower NOx pollution, the flame temperature in gas turbine combustors increases continually; thus, the effusion-cooling technology has been used to ensure the combustor liner remains within the allowed temperature, by which the combustion characteristics
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To meet the requirements of achieving higher efficiency and lower NOx pollution, the flame temperature in gas turbine combustors increases continually; thus, the effusion-cooling technology has been used to ensure the combustor liner remains within the allowed temperature, by which the combustion characteristics and emission behavior are possibly influenced. In order to investigate the effects of dome cooling air flow on combustion characteristics and NOx emissions, three-dimensional combustion simulations for a swirl-stabilized can-type gas turbine combustor are carried out in this work by using the computational fluid dynamics (CFD) method. Through adjusting the ratio of the dome cooling air flow and the dilution cooling air flow, the characteristics of flow field, temperature distribution and NOx emissions under each work condition are analyzed. At different ratios of the dome-cooling air flow to the total air flow, the flow velocity field in the region near the center of the combustion chamber is not changed much, while the velocity field near the chamber wall shows a more significant difference. The temperature in the outer recirculation zone within the combustion chamber is effectively reduced as the dome cooling air flow increases. By analyzing the distribution characteristics of the concentration of OH*, it is demonstrated that the dome cooling air flow does not have a direct effect on the reaction of combustion. It is also found that as the ratio of the dome cooling air flow to the total air flow increases from 0 to 0.15, the value of the NOx emissions drops from 28.4 to 26.3 ppmv, about a 7.4% decrease. The distribution of the NOx generation rate in the combustion chamber does not vary significantly with the increasing dome cooling air flow. Furthermore, by calculating the residence time in different stages, when the the ratio of the dome cooling air flow to the total air flow varies from 0 to 0.15, the residence time in the pilot stage decreases obviously, from 42 ms to 18 ms. This means that reduction in residence time is the main factor in the decrease of NOx emissions when the dome cooling air flow increases.
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(This article belongs to the Special Issue Progress in Turbomachinery Technology for Propulsion)
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