Aerospace

17 pages, 4173 KiB

Open AccessArticle

A Parameter Self-Tuning Rule Based on Spatial–Temporal Scale for Active Disturbance Rejection Control and Its Application in Flight Test Chamber Systems

by Zhuang Xu, Hehong Zhang, Yunde Xie, Chao Zhai, Xin Wang and Feng Huang

Aerospace 2025, 12(6), 465; https://doi.org/10.3390/aerospace12060465 - 23 May 2025

Abstract

Active disturbance rejection control (ADRC) emerges as a promising control approach due to its partial model-based characteristics and strong disturbance rejection capabilities. Nevertheless, it is a difficult problem to tune various parameters of ADRC in practical applications. To address the challenge of parameter [...] Read more.

Active disturbance rejection control (ADRC) emerges as a promising control approach due to its partial model-based characteristics and strong disturbance rejection capabilities. Nevertheless, it is a difficult problem to tune various parameters of ADRC in practical applications. To address the challenge of parameter tuning, this work develops a parameter self-tuning rule based on spatial–temporal scale transformations to simplify the tuning process and enhance its control performance. In particular, based on the transformations of spatial–temporal scale, the parameter tuning relationships for ADRC’s components, including tracking differentiator (TD), extended state observer (ESO) and feedback controller, are provided for a second-order nonlinear system. Numerical simulations show that the proposed method can conveniently and effectively provide a set of well-tuned parameters for ADRC to boost the efficiency of control. Finally, the proposed parameter tuning rule is applied to the intake pressure control of the flight test chamber system, further validating its effectiveness. The results demonstrate that the ADRC with the proposed parameter self-tuning method significantly improves the precision of the intake pressure under different operating conditions, thereby ensuring the reliability of aeroengine flight tests. Full article

(This article belongs to the Section Aeronautics)

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15 pages, 3780 KiB

Open AccessArticle

Experimental Investigation of Pure Hydrogen Flame in a Matrix Micro-Mixing Combustor

by Zhenzhen Feng, Xiaojing Tian, Liangliang Xu, Xi Xia and Fei Qi

Aerospace 2025, 12(6), 464; https://doi.org/10.3390/aerospace12060464 - 23 May 2025

Abstract

Pure hydrogen combustion is a critical pathway to achieving zero-carbon emissions for the gas turbine industry. Micro-mixing combustion is one of the most widely attractive hydrogen combustion methods in gas turbines. This study investigates pure hydrogen flame in a 3 × 3 matrix [...] Read more.

Pure hydrogen combustion is a critical pathway to achieving zero-carbon emissions for the gas turbine industry. Micro-mixing combustion is one of the most widely attractive hydrogen combustion methods in gas turbines. This study investigates pure hydrogen flame in a 3 × 3 matrix micro-mix combustor. The setup includes nine micro-mix injectors, each equipped with a bluff body and a hydrogen injection tube. The OH* chemiluminescence imaging and PIV (Particle Image Velocimetry) techniques were employed to visualize the single- and triple-flame morphology and flow field under various operating conditions. The results show that equivalence ratio, flow rate, and air injector exit angle can influence the flame structure and combustion characteristics, providing an insightful understanding of micro-mix pure hydrogen combustion. Full article

(This article belongs to the Special Issue Scientific and Technological Advances in Hydrogen Combustion Aircraft)

26 pages, 2677 KiB

Open AccessArticle

LLM-ACNC: Aerospace Requirement Texts Knowledge Graph Construction Utilizing Large Language Model

by Yuhao Liu, Junjie Hou, Yuxuan Chen, Jie Jin and Wenyue Wang

Aerospace 2025, 12(6), 463; https://doi.org/10.3390/aerospace12060463 - 23 May 2025

Abstract

Traditional methods for requirement identification depend on the manual transformation of unstructured requirement texts into formal documents, a process that is both inefficient and prone to errors. Although requirement knowledge graphs offer structured representations, current named entity recognition and relation extraction techniques continue [...] Read more.

Traditional methods for requirement identification depend on the manual transformation of unstructured requirement texts into formal documents, a process that is both inefficient and prone to errors. Although requirement knowledge graphs offer structured representations, current named entity recognition and relation extraction techniques continue to face significant challenges in processing the specialized terminology and intricate sentence structures characteristic of the aerospace domain. To overcome these limitations, this study introduces a novel approach for constructing aerospace-specific requirement knowledge graphs using a large language model. The method first employs the GPT model for data augmentation, followed by BERTScore filtering to ensure data quality and consistency. An efficient continual learning based on token index encoding is then implemented, guiding the model to focus on key information and enhancing domain adaptability through fine-tuning of the Qwen2.5 (7B) model. Furthermore, a chain-of-thought reasoning framework is established for improved entity and relation recognition, coupled with a dynamic few-shot learning strategy that selects examples adaptively based on input characteristics. Experimental results validate the effectiveness of the proposed method, achieving F1 scores of 88.75% in NER and 89.48% in relation extraction tasks. Full article

30 pages, 2092 KiB

Open AccessArticle

Wetted and Projected Area Relationships in Commercial Airplane Design

by Pasquale M. Sforza

Aerospace 2025, 12(6), 462; https://doi.org/10.3390/aerospace12060462 - 23 May 2025

Abstract

Using generally available geometric data, calculations of wetted and projected areas of major components, that is, wings, fuselages, empennage, and engine nacelles, for 55 airplanes were compiled into a database comprising four groups: commercial, supersonic, all-wing, and military airplanes. Attention is primarily focused [...] Read more.

Using generally available geometric data, calculations of wetted and projected areas of major components, that is, wings, fuselages, empennage, and engine nacelles, for 55 airplanes were compiled into a database comprising four groups: commercial, supersonic, all-wing, and military airplanes. Attention is primarily focused on subsonic and supersonic commercial airliners, and the wetted areas of the components of each are discussed and shown to be reasonably estimated by simple functions of airplane geometry, like gross wing planform area, fuselage length and diameter. Comparisons of total wetted areas of 13 commercial airplanes and 5 military airplanes with results reported by 14 independent studies showed good agreement. Total wetted areas for all the airplanes were shown to be well-represented by simple functions of wing planform area S alone. Relationships between the projected and wetted areas of the commercial airplanes were explored to illustrate the implications for airplane design, including accommodation of fuselage stretch, trends in component wetted area fractions, correspondence of wetted areas to planform envelope—that is, the product of wingspan and fuselage length, relation of frontal areas to wetted areas, and application of a planform configuration parameter, B = (bAR)^3/16(1 + 3.5/AR^9/4)^−1/2, to estimation of (L/D)_max—and prediction of wetted area as a function of gross weight based on the square–cube relation between area and volume. Full article

(This article belongs to the Section Aeronautics)

32 pages, 2538 KiB

Open AccessArticle

RBF-Learning-Based Many-Objective Metaheuristic for Robust and Optimal Controller Design in Fixed-Structure Heading Autopilot

by Nattapong Ruenruedeepan, Sujin Bureerat, Natee Panagant and Nantiwat Pholdee

Aerospace 2025, 12(6), 461; https://doi.org/10.3390/aerospace12060461 - 23 May 2025

Abstract

This paper presents an innovative many-objective metaheuristic (MnMH) algorithm designed to tackle the challenges of robust and optimal controller design for fixed-structure heading autopilots. The proposed approach leverages the radial basis function (RBF)-learning operator during the reproduction phase of the MnMH to generate [...] Read more.

This paper presents an innovative many-objective metaheuristic (MnMH) algorithm designed to tackle the challenges of robust and optimal controller design for fixed-structure heading autopilots. The proposed approach leverages the radial basis function (RBF)-learning operator during the reproduction phase of the MnMH to generate high-quality solutions. A key feature of the method is its generation of a target Pareto front, in which a z-surrogate model makes predictions to guide design solutions toward achieving optimal performance. The effectiveness of the new algorithm is validated through both fixed-structure heading autopilot controller design problems and standard benchmark optimization problems. Results consistently show that the proposed algorithm outperforms several existing MnMHs across all tested scenarios. This study offers valuable insights into many-objective optimization and demonstrates the algorithm’s potential for enhancing robust controller design in heading autopilot systems. Full article

(This article belongs to the Special Issue Advanced Aircraft Structural Design and Applications)

16 pages, 6724 KiB

Open AccessReview

Nanosecond Laser Etching of Surface Drag-Reducing Microgrooves: Advances, Challenges, and Future Directions

by Xulin Wang, Zhenyuan Jia, Jianwei Ma and Wei Liu

Aerospace 2025, 12(6), 460; https://doi.org/10.3390/aerospace12060460 - 23 May 2025

Abstract

With the increasing demand for drag reduction, energy consumption reduction, and low weight in civil aircraft, high-precision microgroove preparation technology is being developed internationally to reduce wall friction resistance and save energy. Compared to mechanical processing, chemical etching, roll forming, and ultrafast laser [...] Read more.

With the increasing demand for drag reduction, energy consumption reduction, and low weight in civil aircraft, high-precision microgroove preparation technology is being developed internationally to reduce wall friction resistance and save energy. Compared to mechanical processing, chemical etching, roll forming, and ultrafast laser processing, nanosecond lasers offer processing precision, high efficiency, and controllable thermal effects, enabling low-cost and high-quality preparation of microgrooves. However, the impact of nanosecond laser etching on the fatigue performance of substrate materials remains unclear, leading to controversy over whether high-precision shape control and fatigue performance enhancement in microgrooves can be achieved simultaneously. This has become a bottleneck issue that urgently needs to be addressed. This paper focuses on the current research status of nanosecond laser processing quality control for microgrooves and the research status of laser effects on enhancing the fatigue performance of substrate materials. It identifies the main existing issues: (1) how to induce surface residual compressive stress through the thermo-mechanical coupling effect of nanosecond lasers to suppress micro-defects while ensuring high-precision shape control of fixed microgrooves; and (2) how to quantify the regulation of nanosecond laser process parameters on residual stress distribution and fatigue performance in the microgroove area. To address these issues, this paper proposes a collaborative strategy for high-quality shape control and surface strengthening in fixed microgrooves, an analysis of multi-dimensional fatigue regulation mechanisms, and a new method for multi-objective process optimization. The aim is to control the geometric accuracy error of the prepared surface microgrooves within 5% and to enhance the fatigue life of the substrate by more than 20%, breaking through the technical bottleneck of separating “drag reduction design” from “fatigue resistance manufacturing”, and providing theoretical support for the integrated manufacturing of “drag reduction-fatigue resistance” in aircraft skins. Full article

(This article belongs to the Section Aeronautics)

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21 pages, 1167 KiB

Open AccessArticle

Towards Optimal Wing Design for Novel Airframe and Propulsion Opportunities

by Nicolas F. M. Wahler and Ali Elham

Aerospace 2025, 12(6), 459; https://doi.org/10.3390/aerospace12060459 - 23 May 2025

Abstract

Strict sustainability objectives have been established for the upcoming generation of aircraft. A promising innovative airframe concept is the ultra-high-aspect-ratio Strut-Braced-Wing Aircraft (SBWA). Hydrogen-powered concepts are strong candidates for sustainable propulsion. The study investigates the influence of Liquid Hydrogen (LH2) propulsion on the [...] Read more.

Strict sustainability objectives have been established for the upcoming generation of aircraft. A promising innovative airframe concept is the ultra-high-aspect-ratio Strut-Braced-Wing Aircraft (SBWA). Hydrogen-powered concepts are strong candidates for sustainable propulsion. The study investigates the influence of Liquid Hydrogen (LH2) propulsion on the optimal wing geometry of medium-range SBWA for minimum-cost and minimum-emission objectives. Multiobjective optimizations are performed in two optimization frameworks of differing fidelity for both kerosene- and LH2-propelled SBWA concepts. Furthermore, a range of Pareto-optimal designs show the changes in the optimized planform for variable weighting of the two objectives. The results show that the differences in the optimal wing geometry between the kerosene- and LH2-powered results for each respective objective function are small. For both aircraft, the minimum-emission objective optimizes for lower fuel burns and hence lower emissions, albeit at an increase in wing structural mass. The minimum-cost objective balances the reductions in structural and fuel masses, resulting in a lighter design at lower aspect ratios. Other wing-shape parameters only have minor contributions. Although the wing aspect ratios for both objectives differ by ca. 50%, the actual changes are only 2.5% in fuel and 1.5% in Direct Operating Cost (DOC). Due to a larger set of design variables used in the higher-fidelity optimizations, further parasite and wave drag reduction opportunities result in increased optimal aspect ratios. Full article

(This article belongs to the Special Issue Overall Aircraft Design for New Airframe Technologies, New Energy Systems and New Operations)

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30 pages, 3459 KiB

Open AccessArticle

Comparative Study of Sphere Decoding Algorithm and FCS-MPC for PMSMs in Aircraft Application

by Joseph O. Akinwumi, Yuan Gao, Xin Yuan, Sergio Vazquez and Harold S. Ruiz

Aerospace 2025, 12(6), 458; https://doi.org/10.3390/aerospace12060458 - 23 May 2025

Abstract

In this study, we propose a long prediction horizon finite control set model predictive control (FCS-MPC) framework for PMSMs. Initial simulations using a one-norm cost function resulted in instability in switching frequency control, particularly due to the inherent limitations imposed by the sampling [...] Read more.

In this study, we propose a long prediction horizon finite control set model predictive control (FCS-MPC) framework for PMSMs. Initial simulations using a one-norm cost function resulted in instability in switching frequency control, particularly due to the inherent limitations imposed by the sampling interval when no control effort was applied. To mitigate this, we reformulated the MPC framework using a two-norm cost function within a sphere decoding algorithm (SDA), which, at high sampling intervals (>40

μ

s), resulted in an undershoot in the direct-quadrature axis. Extensive simulations were conducted over a range of sampling intervals (1–

80 μ

s), revealing that while a

10 μ

s interval achieved the lowest THD, it also led to an increased switching frequency. To address this trade-off, a weighting factor tuning approach was employed, effectively reducing switching frequency while maintaining acceptable THD levels. Further investigations analyzed the effects of three-step and five-step prediction horizons, as well as parameter mismatches in the long prediction formulation, providing critical insights into controller robustness. These findings underscore the importance of norm selection, sampling interval optimization, and weighting factor adjustments in balancing THD reduction and switching frequency. The proposed approach enhances system efficiency, reliability, and overall performance, offering significant implications for high-performance aerospace PMSM applications. Full article

(This article belongs to the Special Issue Aircraft Electric Power System: Design, Control, and Maintenance)

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15 pages, 11215 KiB

Open AccessArticle

Effects of Reduced Frequency on the Aerodynamic Characteristics of a Pitching Airfoil at Moderate Reynolds Numbers

by Teng Zhou, Huijing Cao and Ben Zhao

Aerospace 2025, 12(6), 457; https://doi.org/10.3390/aerospace12060457 - 23 May 2025

Abstract

Aerodynamic characteristics of a pitching NACA 0012 airfoil, including the load performance and flow field features, are studied using numerical simulations in this paper. Large Eddy Simulations (LESs) have been performed, and the chord-based Reynolds number is set to

6.6 \times 10^{4}

[...] Read more.

Aerodynamic characteristics of a pitching NACA 0012 airfoil, including the load performance and flow field features, are studied using numerical simulations in this paper. Large Eddy Simulations (LESs) have been performed, and the chord-based Reynolds number is set to

6.6 \times 10^{4}

. Pitching frequency varies from 3 to 20 Hz, corresponding to a reduced frequency of 0.094–0.628 (

k = π f_{p} c / U_{\infty}

, where

f_{p}

is the pitching frequency, c is the chord length, and

U_{\infty}

refers to the incident flow speed). As the pitching frequency increases, the maximum lift coefficient achieved in one pitching cycle decreases, and the direction of the lift hysteresis loop changes as the pitching frequency exceeds a certain value, leading to a change in the lift of the sign at the zero-incidence moment, which is a result of the instantaneous flow patterns on the airfoil surface. As the pitching frequency increases, flow unsteadiness develops less in one pitching cycle, and the time duration in which the turbulence boundary layer can be detected in one pitching cycle shrinks. Additionally, for the pitching airfoil, combinations of the flow patterns on the upper and lower sides, such as laminar separation and the turbulent boundary layer, or laminar separation and the laminar separation bubble, were observed on the airfoil surface, and these were not detected on a static airfoil at the corresponding Reynolds number. This is considered an effect of the pitching motion that is in addition to the phase-lag effect. Full article

(This article belongs to the Special Issue Aerodynamics and Aeroacoustics of Unsteady Flow)

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20 pages, 8468 KiB

Open AccessArticle

Numerical Investigation of Fuel Cooling in Sudden Expansion Structures of Scramjet Engines

by Qingjun Wang, Minglei Hu, Zongjie Quan and Yu Chen

Aerospace 2025, 12(6), 456; https://doi.org/10.3390/aerospace12060456 - 22 May 2025

Abstract

Local overheating in cavities seriously threatens the safe operation of scramjet engines. To investigate the formation mechanism and control methods of local overheating, this paper conducts numerical simulations on the cooling process of cavity sudden expansion (S-E) structures. A three-dimensional numerical model coupled [...] Read more.

Local overheating in cavities seriously threatens the safe operation of scramjet engines. To investigate the formation mechanism and control methods of local overheating, this paper conducts numerical simulations on the cooling process of cavity sudden expansion (S-E) structures. A three-dimensional numerical model coupled with pyrolysis reactions is established and validated through experiments. The effects of thermal pyrolysis reactions and cooling channel parameters on flow distribution are analyzed, and comparative studies with different channel parameters are performed. The results show that S-E structures are prone to uneven fuel flow distribution, leading to local over-temperature phenomena, and thermal pyrolysis reactions will aggravate this phenomenon to a certain extent. Increasing the aspect ratio of the channel can enhance the pressure drop at the inlet of the S-E structure and improve the uniformity of flow distribution. When the aspect ratio increases from one to eight, the mass flow distribution deviation ϕ_m decreases from 0.954 to 0.181. More uniform flow distribution under a larger aspect ratio avoids local over-temperature in the S-E structure, and reduces the coking risk caused by local excessive pyrolysis. This work reveals the fundamental characteristics of cooling heat transfer in the S-E structure of Scramjet engines and can provide recommendations for the design of cooling channels. Full article

(This article belongs to the Section Aeronautics)

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16 pages, 3228 KiB

Open AccessArticle

Symbolic Regression-Based Modeling for Aerodynamic Ground-to-Flight Deviation Laws of Aerospace Vehicles

by Di Ding, Qing Wang, Qin Chen and Lei He

Aerospace 2025, 12(6), 455; https://doi.org/10.3390/aerospace12060455 - 22 May 2025

Abstract

The correlation between aerodynamic data obtained from ground and flight tests is crucial in developing aerospace vehicles. This paper proposes methods for modelling this correlation that combine feature extraction and symbolic regression. The neighborhood component analysis (NCA) method is utilized to extract features [...] Read more.

The correlation between aerodynamic data obtained from ground and flight tests is crucial in developing aerospace vehicles. This paper proposes methods for modelling this correlation that combine feature extraction and symbolic regression. The neighborhood component analysis (NCA) method is utilized to extract features from the high-dimensional state space and then symbolic regression (SR) is applied to find the concise optimal expression. First, a simulation example of the NASA Twin Otter aircraft is used to validate the NCA and the SR tool developed by the research team in modeling the aerodynamic coefficient deviation between ground and flight due to an unpredictable inflight icing failure. Then, the method and tool are applied to real flight tests of two types of aerospace vehicles with different configurations. The final optimized mathematical models show that the two vehicles’ pitching moment coefficient deviations are related to the angle of attack (AOA) only. The mathematical model built using NCA and the SR tool demonstrates higher fitting accuracy and better generalization performance for flight test data than other typical data-driven methods. The mathematical model delivers a multi-fold enhancement in fitting accuracy over data-driven methods for all fight cases. For UAV flight test data, the average root mean square error (RMSE) of the mathematical model demonstrates a maximum improvement of 37% in accuracy compared to three data-driven methods. For XRLV flight test data, the prediction accuracy of the mathematical model shows an enhancement exceeding 80% relative to Gaussian kernel SVM and Gaussian process data-driven models. The research verifies the feasibility and effectiveness of the data feature extraction combined with the symbolic regression method in mining the correlation law between ground and flight deviations of aerodynamic characteristics. This study provides valuable insight for modeling problems with finite data samples and explicit physical meanings. Full article

(This article belongs to the Special Issue Flight Dynamics, Control & Simulation (2nd Edition))

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22 pages, 35357 KiB

Open AccessArticle

LumiLoc: A Low-Light-Optimized Visual Localization Framework for Autonomous Drones

by Ruokun Qu, Zhiyuan Wang, Yelu Liu, Chenglong Li, Hui Jiang and Chen Fang

Aerospace 2025, 12(6), 454; https://doi.org/10.3390/aerospace12060454 - 22 May 2025

Abstract

In low-light conditions, UAV localization faces substantial challenges due to reduced visibility, elevated noise levels, and diminished contrast. To address these issues, we propose a low-light-optimized visual localization framework that integrates an attention-based image enhancement module, a robust feature extraction network tailored for [...] Read more.

In low-light conditions, UAV localization faces substantial challenges due to reduced visibility, elevated noise levels, and diminished contrast. To address these issues, we propose a low-light-optimized visual localization framework that integrates an attention-based image enhancement module, a robust feature extraction network tailored for degraded environments, and a lightweight pose estimation algorithm that fuses geometric and convolutional features. Extensive evaluations on both real-world and synthetic low-light datasets reveal significant improvements in accuracy, noise resilience, and adaptability to dynamic lighting. Moreover, experimental results validate the framework’s feasibility for applications in night operations, urban air traffic management, and disaster response, thereby effectively overcoming the critical limitations of UAV positioning under low-light conditions. Full article

(This article belongs to the Special Issue Advances in UAV Technology: Dynamics, Guidance, Navigation, and Control of Transformative Aerial Vehicles)

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22 pages, 4423 KiB

Open AccessArticle

Design and Cushioning Performance Analysis of Spherical Tensegrity Structures

by Jing Zhang, Chuang Shi, Kun Geng, Yanzheng Chen, Hongwei Guo, Rongqiang Liu and Ziming Kou

Aerospace 2025, 12(6), 453; https://doi.org/10.3390/aerospace12060453 - 22 May 2025

Abstract

This study aims to design a novel combined spherical tensegrity structure and evaluate its cushioning performance to offer a new option for a planetary exploration landing mechanism. Initially, based on the circumferential assembling method, a “class II” spherical tensegrity structure was constructed using [...] Read more.

This study aims to design a novel combined spherical tensegrity structure and evaluate its cushioning performance to offer a new option for a planetary exploration landing mechanism. Initially, based on the circumferential assembling method, a “class II” spherical tensegrity structure was constructed using the square frustum tensegrity unit as the basic element. Then, the equilibrium equations for the structure were formulated in accordance with the principle of virtual work to confirm the self-equilibrium of the tensegrity configuration, and the stability of the designed structure was assessed by determining the type of the tensegrity structure according to the Maxwell criterion and the character of the stiffness matrix. Subsequently, the simulation and analysis of the compressive stiffness of the structure under different parameters were carried out based on the finite element analysis method. The landing collision was simulated by using dynamic software to analyze the influence of the structure parameters on the cushioning performance. Finally, an experimental model was built to verify the above analysis, which demonstrates that the designed spherical tensegrity structure offered a large loading space and great cushioning performance. Full article

(This article belongs to the Special Issue Advanced Design for Lightweight Space Materials and Structural Systems)

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38 pages, 14799 KiB

Open AccessArticle

Investigation of Tilt-Proprotor Loads Correlation Between Wind Tunnel Test Data and Comprehensive Modeling

by Yin Ruan, Weite Wang and Wei Zhang

Aerospace 2025, 12(6), 452; https://doi.org/10.3390/aerospace12060452 - 22 May 2025

Abstract

The loads of a model tilt-proprotor with a gimbaled hub were measured in the wind tunnel of CHRDI, operating at 90°, 80°, 70°, 60°, and 45° inclination angles to represent the rotor loads of helicopter and transient flight modes. The flap, lead-lag moments, [...] Read more.

The loads of a model tilt-proprotor with a gimbaled hub were measured in the wind tunnel of CHRDI, operating at 90°, 80°, 70°, 60°, and 45° inclination angles to represent the rotor loads of helicopter and transient flight modes. The flap, lead-lag moments, and pitch rod forces were measured. A comprehensive model was established with both linear inflow and free-wake non-linear inflow models. It is shown that there is a better correlation of alternating flap bending moments between test data and linear inflow model predicted values for the helicopter mode and a good correlation between measured data and free-wake predicted values for transition modes. The static moments are well captured by all inflow models at high thrust coefficients, while they fail to reflect the flap bending direction of the blade root at low thrust coefficients. Neither of the inflow models captured higher harmonics of the blade flap bending moments. The measured 2/rev harmonics of the lag bending moments lie between the linear inflow model and the free wake model predicted values. The current model with no dynamic stall model failed to capture the oscillating loads of the pitch rod. Full article

(This article belongs to the Special Issue Recent Advances in Flight Testing)

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31 pages, 1465 KiB

Open AccessArticle

Intelligent Flight Procedure Design: A Reinforcement Learning Approach with Pareto-Based Multi-Objective Optimization

by Yunyang Huang, Yanxin Zhang, Yandong Zhu, Zhuo Zhang, Longtao Zhu, Hongyu Yang and Yulong Ji

Aerospace 2025, 12(6), 451; https://doi.org/10.3390/aerospace12060451 - 22 May 2025

Abstract

Current flight procedure design primarily relies on expert experience, lacking a systematic approach to comprehensively balance safety, route simplification, and environmental impact. To address this challenge, this paper proposes a reinforcement-learning-based method that leverages carefully crafted reward engineering to achieve an optimized flight [...] Read more.

Current flight procedure design primarily relies on expert experience, lacking a systematic approach to comprehensively balance safety, route simplification, and environmental impact. To address this challenge, this paper proposes a reinforcement-learning-based method that leverages carefully crafted reward engineering to achieve an optimized flight procedure design, effectively considering safety, route simplicity, and environmental friendliness. To further enhance performance by tackling the low sampling efficiency in the replay buffer, we introduce a multi-objective sampling strategy based on the Pareto frontier, integrated with the soft actor–critic (SAC) algorithm. Experimental results demonstrate that the proposed method generates executable flight procedures in the BlueSky open-source flight simulator, successfully balancing these three conflicting objectives, while achieving a 28.6% increase in convergence speed and a 4% improvement in comprehensive performance across safety, route simplification, and environmental impact compared to the baseline algorithm. This study offers an efficient and validated solution for the intelligent design of flight procedures. Full article

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20 pages, 5673 KiB

Open AccessArticle

Unsteady Numerical Investigation into the Impact of Isolator Motion on High-Mach-Number Inlet Restart via Throat Adjustment

by Hongyu Tang, Yuan Liu, Yongfei Cao, Liangjie Gao and Zhansen Qian

Aerospace 2025, 12(5), 450; https://doi.org/10.3390/aerospace12050450 - 21 May 2025

Abstract

This paper focuses on exploring the variable throat-assisted restart method for high-Mach-number inlets. A two-dimensional adjustable throat hypersonic inlet was designed, and unsteady numerical simulations were carried out on its restart process, which was triggered by unstart induced by excessive back pressure and [...] Read more.

This paper focuses on exploring the variable throat-assisted restart method for high-Mach-number inlets. A two-dimensional adjustable throat hypersonic inlet was designed, and unsteady numerical simulations were carried out on its restart process, which was triggered by unstart induced by excessive back pressure and assisted by throat adjustment. The Chimera grid technique was used for grid generation, and the simulations were performed on the ARI_CFD platform. Results show that during the throat adjustment restart process, different flow states emerged with an increase in adjustment height. Specifically, when the adjustment height was too low, an unstarted flow state existed; within a specific height range (with lower and upper critical heights of 1.190 and 1.196, respectively, in this study), a fully restarted flow state occurred; and when the height was too high, an off-design flow state induced by the separation region in the internal contraction section occurred. The geometric adjustment time and throat adjustment angle also had a significant impact on the restart process. Shorter adjustment times and larger adjustment angles expanded the adjustment interval for full restart, as the rotation of the isolator helps reduce the resistance of the separation bubble’s downstream movement on the compression surface, thereby facilitating the full restart of the inlet. Full article

(This article belongs to the Special Issue Innovation and Challenges in Hypersonic Propulsion)

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34 pages, 155018 KiB

Open AccessArticle

ACCORD: A Formal Model for the Digitalization and Automation of Drone Coordination Processes

by Enric Pastor, Miquel Macias, Yeray Martin, Albert Sanchez and Cristina Barrado

Aerospace 2025, 12(5), 449; https://doi.org/10.3390/aerospace12050449 - 20 May 2025

Abstract

This paper introduces ACCORD, a support platform designed to digitalize and automate the coordination processes required by the current drone regulatory framework. Drone operators must complete several coordination actions with both aeronautical and non-aeronautical entities. Traditional aeronautical coordination actions relate to the need [...] Read more.

This paper introduces ACCORD, a support platform designed to digitalize and automate the coordination processes required by the current drone regulatory framework. Drone operators must complete several coordination actions with both aeronautical and non-aeronautical entities. Traditional aeronautical coordination actions relate to the need to access protected airspace volumes around airports. Additional coordination should be established with smaller aeronautical infrastructures, like small aerodromes and heliports, which are not surrounded by any type of pre-defined airspace. Therefore, drone-specific protection volumes have been created. ACCORD enables a single entry point for all the necessary coordination processes for drone operators and infrastructure managers. The objective is to minimize the number of required actions, guarantee full traceability of the process, maximize access to the relevant information, automate the processes as much as possible, and maintain a high level of flexibility to support all coordination processes. After coordination is established, it moves from the strategic/planning phase to the actual execution phase. ACCORD also enables a communication mechanism between the drone operators and the aeronautical infrastructures to extend the coordination to the actual mission execution. ACCORD is currently being tested by some of the most relevant actors in the Catalan drone ecosystem. The current version of the system provides support for all types of aeronautical infrastructures (heliports, aerodromes, and airports) and management duality for situations in which the infrastructure manager and the aeronautical service provider coexist. Full article

(This article belongs to the Special Issue Advances in Air Traffic and Airspace Control and Management (2nd Edition))

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17 pages, 2913 KiB

Open AccessArticle

On-Orbit Functional Verification of Combustion Science Experimental System in China Space Station

by Pingping Zhao, Xiaowu Zhang, Yu Fang, Hailong Wu, Xiaofang Yang and Huilong Zheng

Aerospace 2025, 12(5), 448; https://doi.org/10.3390/aerospace12050448 - 20 May 2025

Abstract

We demonstrated the development, implementation, and functional verification of the combustion science payload deployed on the China Space Station. The Combustion Science Experiment System (CSES) integrated seven subsystems and modular plugins to address the major challenges facing microgravity combustion research, including the lack [...] Read more.

We demonstrated the development, implementation, and functional verification of the combustion science payload deployed on the China Space Station. The Combustion Science Experiment System (CSES) integrated seven subsystems and modular plugins to address the major challenges facing microgravity combustion research, including the lack of long-duration experimental platforms, spatial constraints, and safety risks. Through on-orbit testing, the core functions of the CSES under microgravity conditions were validated, including gas supply, ignition, combustion diagnostic, exhaust purification, and emission. The system achieved autonomous experiment execution by ground-injected commands. Data from on-orbit methane combustion experiments demonstrated that the CSES was capable of stably supplying oxygen and fuel gas at a preset flow rate, real-time combustion diagnosis, and provided high-resolution flame image. Effectively exhaust gas purification and emission control of the CSES have also been tested and verified. It provides a safe, reliable, and stable microgravity environment of long-duration research for the combustion science and the development of spacecraft fire safety technology. Full article

(This article belongs to the Section Astronautics & Space Science)

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30 pages, 4946 KiB

Open AccessArticle

Frequency Assignment for Aviation Navigation Stations Based on an Improved Multi-Objective Genetic Local Search Algorithm

by Boyang Hao, Yajun Xu, Ke Gong, Tianlu Gao, Yiling Gui, Minghui Liu and Qiang Zhang

Aerospace 2025, 12(5), 447; https://doi.org/10.3390/aerospace12050447 - 20 May 2025

Abstract

With the rapid development of both commercial and general aviation, the frequency assignment problem for aviation navigation stations has become increasingly important. This paper presents a general algorithm for frequency assignment at individual aviation navigation stations. Subsequently, a frequency assignment model for multiple [...] Read more.

With the rapid development of both commercial and general aviation, the frequency assignment problem for aviation navigation stations has become increasingly important. This paper presents a general algorithm for frequency assignment at individual aviation navigation stations. Subsequently, a frequency assignment model for multiple civil aviation navigation stations is established to address large-scale frequency allocation challenges. To overcome the limitations of traditional multi-objective genetic algorithms, such as slow convergence speed and susceptibility to local optima, this study proposes several improved algorithms, including the multi-objective genetic algorithm with randomly assigned weights, the multi-objective genetic local search algorithm, and an improved multi-objective genetic local search algorithm, while optimizing key algorithm parameters. The problem involves multiple objectives, including minimizing interference in frequency assignment and reducing the total number of assigned frequencies. Experimental results demonstrate that the proposed improved multi-objective genetic algorithms—especially IMOGLSA-II—effectively address the frequency assignment problem for aviation navigation stations, achieving notable improvements in solution quality, convergence speed, and stability compared with other multi-objective genetic algorithms. In particular, although the time complexity of the proposed algorithm is slightly higher due to the incorporation of local search mechanisms, it exhibits clear advantages in reducing parameter sensitivity, simplifying algorithm structure, and enhancing engineering applicability. These characteristics make the proposed method not only well-suited to the static and constrained nature of aviation frequency assignment, but also more practical and effective than other mainstream multi-objective optimization algorithms in similar engineering scenarios. Furthermore, the proposed method offers a reliable approach that can be extended to other static frequency assignment problems and broader classes of multi-objective optimization tasks. Full article

(This article belongs to the Section Air Traffic and Transportation)

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