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Performance and Emissions Evaluation of a Turbofan Burner with Hydrogen Fuel
Optical Image Generation Through Digital Terrain Models for Autonomous Lunar Navigation

Journal Description

Aerospace

Aerospace is a peer-reviewed, open access journal of aeronautics and astronautics published monthly online by MDPI. The European Aerospace 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, Ei Compendex, and other databases.
Journal Rank: JCR - Q2 (Engineering, Aerospace) / CiteScore - Q2 (Aerospace Engineering)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 21.3 days after submission; acceptance to publication is undertaken in 2.6 days (median values for papers published in this journal in the second half of 2024).
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: 2.1 (2023); 5-Year Impact Factor: 2.4 (2023)

Imprint Information Journal Flyer Open Access ISSN: 2226-4310

Latest Articles

14 pages, 3040 KiB

Open AccessArticle

Numerical Study on Particle Accumulation and Its Impact on Rotorcraft Airfoil Performance on Mars

by Enrico Giacomini and Lars-Göran Westerberg

Aerospace 2025, 12(5), 368; https://doi.org/10.3390/aerospace12050368 - 23 Apr 2025

Unmanned aerial vehicles (UAVs) have emerged as practical and potentially advantageous tools for scientific investigation and reconnaissance of planetary surfaces, such as Mars. Their ability to traverse difficult terrain and provide high-resolution imagery has revolutionized the concept of exploration. However, operating drones in [...] Read more.

Unmanned aerial vehicles (UAVs) have emerged as practical and potentially advantageous tools for scientific investigation and reconnaissance of planetary surfaces, such as Mars. Their ability to traverse difficult terrain and provide high-resolution imagery has revolutionized the concept of exploration. However, operating drones in the Martian environment presents fundamental challenges due to the harsh conditions and the different atmosphere. Aerodynamic challenges include low chord-based Reynolds number flows and the presence of dust particles, which can accumulate on the airfoil surface. This paper investigates the accumulation of dust on cambered plates with 6% and 1% camber, suitable for the type of flow studied. The analysis is conducted for Reynolds numbers of around 20,000 as a result of dimension restrictions, assuming a wind speed ranging from 12 to 14 m/s. Computational simulations are performed using a 2D C-type mesh in ANSYS Fluent, employing the

γ

-Re SST turbulence model. Dust particle modeling is achieved through the Discrete Phase Model (DPM), with one-way coupling between phases. The accumulation of particles is monitored over a 6-month period with monthly intervals, and the airfoil is set at a 0

^{\circ}

angle of attack. A deposition model, developed using user-defined functions in Fluent, considers particle–airfoil interaction and forces acting on particles. Results indicate a decrease in airfoil performance for negative angles of attack due to geometric changes, particularly due to accumulation on the bottom side near the tip. The discussion includes potential model enhancements and future research directions arising from the assumptions made in this study. Full article

(This article belongs to the Special Issue Planetary Exploration)

25 pages, 2467 KiB

Open AccessArticle

Multibody Analysis of Lever-Spring Landing Gear with Elastomer Shock Absorbers: Modelling, Simulations and Drop Tests

by Fuyou Li, Jianxin Zhu, Xiangfu Zou, Zhongjian Pan and Jian Chen

Aerospace 2025, 12(5), 367; https://doi.org/10.3390/aerospace12050367 - 23 Apr 2025

This study investigates the ground reaction force of lever-spring landing gear (LSLG) equipped with compressible elastomer shock absorbers (ESA) during the landing process. First, a numerical dynamic model of the LSLG was developed in MATLAB/Simulink, revealing that runway roughness exerts a negligible influence [...] Read more.

This study investigates the ground reaction force of lever-spring landing gear (LSLG) equipped with compressible elastomer shock absorbers (ESA) during the landing process. First, a numerical dynamic model of the LSLG was developed in MATLAB/Simulink, revealing that runway roughness exerts a negligible influence on the ground reaction force during landing. The load characteristics established fundamental references for subsequent FEA-based structural design. Furthermore, an FEA model integrating the LSLG and the aircraft was developed with parameters calibrated for elastic units. The multibody dynamics simulation (MBDS) quantified the vertical ground reaction force and the structural stresses of LSLG, demonstrating two critical relationships: (1) the overload coefficient correlated with the sinking velocity yet exhibits no correlation with aircraft mass and (2) the peak of oscillating force attenuated faster with heavier landing weight at higher sinking velocities. A nonlinear multi-variables function was fitted to predict the maximum vertical ground reaction force. Subsequently, experimental validation via a landing gear drop test (LGDT) showed a maximum error of 8.39% between the results of the LGDT and the MBDS, confirming the accuracy of simulation and the fitting surface function for force prediction. The study further validates the feasibility and reliability of using the MBDS to model and study the LSLG with ESAs. Full article

(This article belongs to the Section Aeronautics)

14 pages, 7735 KiB

Open AccessArticle

Numerical Investigation of a Supersonic Wind Tunnel Diffuser Optimization

by Riccardo Nicoletti, Francesco Margani, Luca Armani, Antonella Ingenito, Chihiro Fujio, Hideaki Ogawa, Seoeum Han and Bok Jik Lee

Aerospace 2025, 12(5), 366; https://doi.org/10.3390/aerospace12050366 - 23 Apr 2025

The objective of this study is to enhance the methodology for the design of a supersonic wind tunnel, improving the process with advanced computational techniques. The supersonic wind tunnel is intended to operate within a flight envelope of Mach 2.5 to 4 and [...] Read more.

The objective of this study is to enhance the methodology for the design of a supersonic wind tunnel, improving the process with advanced computational techniques. The supersonic wind tunnel is intended to operate within a flight envelope of Mach 2.5 to 4 and altitudes between 18 and 20 km; this study focuses on the operative condition of Mach 3.5. The research is based on computational fluid dynamics, enabling a deeper understanding of fluid flow phenomena that can deteriorate the operability of the wind tunnel. Additionally, a detailed mesh independence study has been conducted to ensure the reliability and robustness of the computational results. These new analyses allowed for a more comprehensive optimization in the state of the art of tunnel geometry and operational conditions, further enhancing the ability to sustain supersonic flow for extended durations. Particular attention was given to the second throat, which plays a crucial role in the overall performance of the facility, especially during the start-up process. Its design has been refined to improve efficiency by reducing the minimum starting pressure. Full article

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

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33 pages, 66394 KiB

Open AccessArticle

Application of Proper Orthogonal Decomposition in Spatiotemporal Characterization and Reduced-Order Modeling of Rotor–Stator Interaction Flow Field

by Yongkang Lin, Weijian Yang, Hu Wang, Fazhong Wang, Jie Hu and Jianyao Yao

Aerospace 2025, 12(5), 365; https://doi.org/10.3390/aerospace12050365 - 23 Apr 2025

The periodic unsteady flow induced by rotor–stator interaction (RSI) is the primary cause of blade forced vibration and fatigue failure. Therefore, analyzing the excitation characteristics of RSI flow fields under multi-parameter conditions is essential for vibration analysis and optimization in fluid–structure interaction. This [...] Read more.

The periodic unsteady flow induced by rotor–stator interaction (RSI) is the primary cause of blade forced vibration and fatigue failure. Therefore, analyzing the excitation characteristics of RSI flow fields under multi-parameter conditions is essential for vibration analysis and optimization in fluid–structure interaction. This study derives the Toeplitz structure of the correlation matrix in proper orthogonal decomposition (POD) for strictly periodic flow fields and reveals that the POD spatial modes appear in pairs with a 90° spatial phase difference, which originates from the cosine and sine form of the eigenvectors of the Toeplitz matrix. Taking a 1.5-stage compressor cascade as an example, the POD method is employed to effectively extract the main spatiotemporal characteristics of the RSI flow field, and the spatial symmetry and phase difference of the POD modes are further interpreted from a physical perspective. To address the high computational cost and resource demands arising from large-scale similar cases in multi-parameter excitation optimization and analysis, a reduced-order modeling (ROM) method based on time–space and parameter decoupling is proposed using multi-parameter POD. Spatial bases are extracted through the first-level POD, and a second-level POD is applied to the first-level coefficients to obtain temporal bases and coefficients that are solely parameter-dependent. A radial basis function (RBF) interpolation is used to establish the mapping between parameters and the second-level coefficients, enabling efficient multi-parameter ROM construction. The resulting ROM achieves a relative prediction error of less than 1.4% under typical operating conditions and less than 2.9% near the choke boundary, improving computational efficiency by four orders of magnitude while maintaining accuracy, thereby providing an effective approach for aerodynamic excitation acquisition. Full article

(This article belongs to the Section Aeronautics)

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17 pages, 3592 KiB

Open AccessArticle

Cost Effectiveness of Reusable Launch Vehicles Depending on the Payload Capacity

by Si-Yoon Kang, Min-Seon Jo, Jeong-Yeol Choi and Soo Seok Yang

Aerospace 2025, 12(5), 364; https://doi.org/10.3390/aerospace12050364 - 22 Apr 2025

Recently, in the space market, there has been a rapid reduction in the launch price. The major reason for this is that a few commercial companies began to enter the space market about ten years ago, which has changed the space market from [...] Read more.

Recently, in the space market, there has been a rapid reduction in the launch price. The major reason for this is that a few commercial companies began to enter the space market about ten years ago, which has changed the space market from monopolization to competition and accelerated the adoption of commercial efficiency in technology and management. Also, SpaceX made a breakthrough by successfully recovering the first stage of its launch vehicle in 2016, thereby opening the door to reusable launch vehicles. They have declared their intention to significantly reduce satellite launch costs in the future by utilizing the potential of reusable launch vehicles. In this study, we calculate the total launch cost required to place a single satellite into Low Earth Orbit (LEO) and compare the launch costs for three different payload capacity scenarios, investigating how payload capacity affects the cost-effectiveness of reusable launch vehicles. The launch cost is broken down into development costs, production costs, reuse costs, operational costs, fixed costs, and insurance costs, with cost estimation equations utilized based on cost calculation models such as TRANSCOST. Full article

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

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25 pages, 10082 KiB

Open AccessArticle

Preliminary Design of a Tandem-Wing Unmanned Aerial System

by Alejandro Sanchez-Carmona, Daniel del Río Velilla, Antonio Fernández López and Cristina Cuerno-Rejado

Aerospace 2025, 12(5), 363; https://doi.org/10.3390/aerospace12050363 - 22 Apr 2025

The drone industry is continuously growing. The regulatory framework that allows these aircraft to operate safely is gradually evolving, enabling missions with growing associated risks, although it is not progressing at the same speed as the industry itself. To provide certainty to regulators, [...] Read more.

The drone industry is continuously growing. The regulatory framework that allows these aircraft to operate safely is gradually evolving, enabling missions with growing associated risks, although it is not progressing at the same speed as the industry itself. To provide certainty to regulators, it is necessary to employ design methodologies that are recognized in the aerospace industry. Therefore, in this work, we addressed the design and manufacturing of a lightweight unconventional-configuration unmanned aircraft by adapting widely known conceptual design methodologies from manned aviation from authors such as Torenbeek and Roskam. Manufacturing was carried out by combining new techniques for the use of composite materials with additive manufacturing. A wide variability in the results was identified across the different models used. However, taking the most restrictive estimates into account, the results show that the structural weight estimates of the wing, made using classical manned aviation methods, align with the final weight obtained, assuming the wing can withstand the aerodynamic and inertial loads applied within a certain safety margin. Full article

(This article belongs to the Section Aeronautics)

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16 pages, 3004 KiB

Open AccessArticle

Experimental and Numerical Study of a UAV Propeller Printed in Clear Resin

by Mingtai Chen, Jacob Wimsatt, Tianming Liu and Tiegang Fang

Aerospace 2025, 12(5), 362; https://doi.org/10.3390/aerospace12050362 - 22 Apr 2025

This paper presents an experimental and numerical investigation of a 254 mm resin-printed propeller operating at rotational speeds between 3000 and 9000 RPM. Propeller thrust and torque were measured using a six-degree-of-freedom load cell, while acoustic data were captured with a microphone positioned [...] Read more.

This paper presents an experimental and numerical investigation of a 254 mm resin-printed propeller operating at rotational speeds between 3000 and 9000 RPM. Propeller thrust and torque were measured using a six-degree-of-freedom load cell, while acoustic data were captured with a microphone positioned three times the propeller diameter from the center. To complement the experimental analysis, computational simulations were conducted using ANSYS Fluent with the detached eddy simulation (DES) model, the Ffowcs-Williams and Hawkings (FW-H) model, and a transient flow solver. The figure of merit (FM) results show that the resin propeller slightly outperforms two commercial counterparts with a marginal difference between the wood and resin propellers. Additionally, the resin propeller demonstrates better noise performance, exhibiting the lowest primary tonal noise, broadband noise, and overall sound pressure level (OASPL), with minimal differences between the two commercial counterparts. ANSYS Fluent simulations predict thrust and torque within a 10% error margin, showing particularly accurate results for primary tonal noise. A new trade-off index is proposed to assess the balance between propeller performance and aeroacoustics, revealing distinct trends compared to traditional metrics. Furthermore, aerodynamic phenomena such as flow separation on the leading edge near the tip, flow separation behind the middle trailing edge, and vortex interactions at the root are identified as key contributors to tonal and broadband noise. These findings provide valuable insights into propeller design and aeroacoustic optimization. Full article

(This article belongs to the Section Aeronautics)

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17 pages, 4957 KiB

Open AccessArticle

A Novel Analytical Approach for Spacecraft Fly-Around Formation Design with a Low-Thrust Maneuver

by Xun Wang, Min Hu, Chaojun Xin and Shirui Zheng

Aerospace 2025, 12(5), 361; https://doi.org/10.3390/aerospace12050361 - 22 Apr 2025

This paper investigates the fly-around formation between the servicer spacecraft and the target spacecraft. Inspired by the spacecraft orbital motion under the Earth’s gravity, an intuitive, analytical guidance law for spatial fly-around formation design with the low-thrust maneuver is proposed. Beginning with the [...] Read more.

This paper investigates the fly-around formation between the servicer spacecraft and the target spacecraft. Inspired by the spacecraft orbital motion under the Earth’s gravity, an intuitive, analytical guidance law for spatial fly-around formation design with the low-thrust maneuver is proposed. Beginning with the relative translational dynamics based on relative position and velocity, the control input of the guidance law is designed to contain two parts. The first part is the feed-forward term, which makes the relative dynamics a second-order integration model. The second part is the artificial gravity term, which has similar expressions to the Earth’s gravity, and includes the artificial gravitational coefficient and the vector of the artificial gravity center. The above two parameters can be designed to determine the size, shape, and period of the fly-around trajectory. Specifically, three kinds of fly-around trajectories are discussed in detail. The first two are the spatial ellipses with the target spacecraft locating at the focus and the center of the ellipses, respectively. The third is the spatial circle. The proposed method can be easily extended to the design of planar fly-around formation, which is very systematic and comprehensive, and the fuel consumption of the control input is specifically discussed. Numerical simulations are conducted to demonstrate the efficiency of the proposed method. Full article

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22 pages, 3669 KiB

Open AccessArticle

Fuel-Optimal In-Track Satellite Formation Trajectory with J₂ Perturbation Using Pontryagin Neural Networks

by Morgan Choi and Seonho Lee

Aerospace 2025, 12(4), 360; https://doi.org/10.3390/aerospace12040360 - 21 Apr 2025

Satellite formation flying faces significant challenges in maintaining its desired configurations due to various orbital perturbations, particularly in low-Earth-orbit environments. This paper presents a novel approach to generating fuel-optimal reference trajectories for in-track satellite formations by incorporating both the Earth’s oblateness ( [...] Read more.

Satellite formation flying faces significant challenges in maintaining its desired configurations due to various orbital perturbations, particularly in low-Earth-orbit environments. This paper presents a novel approach to generating fuel-optimal reference trajectories for in-track satellite formations by incorporating both the Earth’s oblateness (

J_{2}

perturbation) and the inherent nonlinearity of the two-body problem. The resulting indirect optimal control problem is solved using Pontryagin Neural Networks (PoNNs). The proposed method transforms the conventional two-point boundary value problem into a mathematical programming problem, enabling the efficient computation of optimal trajectories. The effectiveness of our approach is validated through extensive numerical simulations at different inclinations of the chief satellite (0–90°) and cross-track separation distances (1–400 km), demonstrating significant reductions in annual fuel consumption compared to conventional approaches. The feasibility of these optimal trajectories is verified through closed-loop simulations using a PD controller, confirming their practical applicability in realistic mission scenarios. This research contributes to enhancing the long-term sustainability of satellite formation flying missions by optimizing fuel efficiency while maintaining precise formations. Full article

(This article belongs to the Special Issue Spacecraft Trajectory Design)

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33 pages, 11917 KiB

Open AccessArticle

Multi-Fidelity Surrogate-Assisted Aerodynamic Optimization of Aircraft Wings

by Eleftherios Nikolaou, Spyridon Kilimtzidis and Vassilis Kostopoulos

Aerospace 2025, 12(4), 359; https://doi.org/10.3390/aerospace12040359 - 20 Apr 2025

This paper presents a multi-fidelity optimization procedure for aircraft wing design, implemented in the early stages of the aircraft design process. Since wing shape is a key factor that influences aerodynamic performance, having an accurate estimate of its efficiency at the conceptual design [...] Read more.

This paper presents a multi-fidelity optimization procedure for aircraft wing design, implemented in the early stages of the aircraft design process. Since wing shape is a key factor that influences aerodynamic performance, having an accurate estimate of its efficiency at the conceptual design phase is highly beneficial for aircraft designers. This study introduces a comprehensive optimization framework for designing the wing of a Class I fixed-wing mini-UAV with electric propulsion, focusing on maximizing aerodynamic efficiency and operational performance. Utilizing Class-Shape Transformation (CST) in combination with Surrogate-Based Optimization (SBO) techniques, the research first optimizes the airfoil shape to identify the most suitable airfoil for the UAV wing. Subsequently, SBO techniques are applied to generate wing geometries with varying characteristics, including aspect ratio (

A R

), taper ratio (

λ

), quarter-chord sweep angle (

Λ_{0.25}

), and tip twist angle (

ε

). These geometries are then evaluated using both low- and high-fidelity aerodynamic simulations. The integration of SBO techniques enables an efficient exploration of the design space while minimizing the computational costs associated with iterative simulations. Specifically, the proposed SBO framework enhances the wing’s aerodynamic characteristics by optimizing the lift-to-drag ratio and reducing drag. Full article

(This article belongs to the Section Aeronautics)

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19 pages, 8368 KiB

Open AccessArticle

A Novel Ultrasonic Sampling Penetrator for Lunar Water Ice in the Lunar Permanent Shadow Exploration Mission

by Yinchao Wang, Zihao Yin, Chenxu Ding, Fei Liu, Weiwei Zhang, Lin Zu, Zhaozeng Gao, Guanghong Tao and Suyang Yu

Aerospace 2025, 12(4), 358; https://doi.org/10.3390/aerospace12040358 - 19 Apr 2025

This paper presents an ultrasonic sampling penetrator with a staggered-impact mode, which has been developed for the extraction of lunar water ice. A comparison of this penetrator with existing drilling and sampling equipment reveals its effectiveness in minimizing disturbance to the in situ [...] Read more.

This paper presents an ultrasonic sampling penetrator with a staggered-impact mode, which has been developed for the extraction of lunar water ice. A comparison of this penetrator with existing drilling and sampling equipment reveals its effectiveness in minimizing disturbance to the in situ state of lunar water ice. This is due to the interleaved impact penetration sampling method, which preserves the original stratigraphic information of lunar water ice. The ultrasonic sampling penetrator utilizes a single piezoelectric stack to generate the staggered-impact motion required for the sampler. Finite element simulation methods are employed for the structural design, with modal analysis and modal degeneracy carried out. The combined utilization of harmonic response analysis and transient analysis is instrumental in attaining the staggered-impact motion. The design parameters were then used to fabricate a prototype and construct a test platform, and the design’s correctness was verified by the experimental results. In future sampling of lunar water ice at the International Lunar Research Station, the utilization of the ultrasonic sampling penetrator is recommended. Full article

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17 pages, 6580 KiB

Open AccessArticle

ISSA-Based Evaluation Method of Actual Navigation Performance of Rotorcraft Logistics Unmanned Aerial Vehicles

by Fei Liu, Liang Zhao, Maolin Wang and Meiliwen Wu

Aerospace 2025, 12(4), 357; https://doi.org/10.3390/aerospace12040357 - 17 Apr 2025

In response to the demand for the evaluation of the actual navigation performance (ANP) of rotorcraft logistics uncrewed aerial vehicle (UAV) navigation systems in urban scenarios, this paper proposes a method for evaluating the ANP of rotorcraft logistics UAVs based on the Improved [...] Read more.

In response to the demand for the evaluation of the actual navigation performance (ANP) of rotorcraft logistics uncrewed aerial vehicle (UAV) navigation systems in urban scenarios, this paper proposes a method for evaluating the ANP of rotorcraft logistics UAVs based on the Improved Sparrow Search Algorithm (ISSA). Taking ANP as the optimization objective, an optimization model for the ANP of rotorcraft logistics UAVs is constructed. Based on the probability of the UAV’s actual position falling within the error circle, an initial population strategy based on probabilistic decision-making is designed, and an adaptive dynamic step size strategy and dynamic compression search strategy are proposed to improve the traditional Sparrow Search Algorithm (SSA), enhancing the algorithm’s ability of optimization and to escape local extremum. The contribution of this paper mainly includes constructing the ANP optimization model and designing the ISSA method. Experimental results show that the proposed method can effectively estimate ANP, achieve onboard performance monitoring and warning, and ensure the required navigation performance (RNP) and flight safety of UAVs. Full article

(This article belongs to the Special Issue Recent Progress in Dynamics, Control, and Guidance of Green Aviation and Advanced Air Mobility)

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25 pages, 2639 KiB

Open AccessArticle

Advances in Aircraft Skin Defect Detection Using Computer Vision: A Survey and Comparison of YOLOv9 and RT-DETR Performance

by Nutchanon Suvittawat, Christian Kurniawan, Jetanat Datephanyawat, Jordan Tay, Zhihao Liu, De Wen Soh and Nuno Antunes Ribeiro

Aerospace 2025, 12(4), 356; https://doi.org/10.3390/aerospace12040356 - 17 Apr 2025

Aircraft skin surface defect detection is critical for aviation safety but is currently mostly reliant on manual or visual inspections. Recent advancements in computer vision offer opportunities for automation. This paper reviews the current state of computer vision algorithms and their application in [...] Read more.

Aircraft skin surface defect detection is critical for aviation safety but is currently mostly reliant on manual or visual inspections. Recent advancements in computer vision offer opportunities for automation. This paper reviews the current state of computer vision algorithms and their application in aircraft defect detection, synthesizing insights from academic research (21 publications) and industry projects (18 initiatives). Beyond a detailed review, we experimentally evaluate the accuracy and feasibility of existing low-cost, easily deployable hardware (drone) and software solutions (computer vision algorithms). Specifically, real-world data were collected from an abandoned aircraft with visible defects using a drone to capture video footage, which was then processed with state-of-the-art computer vision models—YOLOv9 and RT-DETR. Both models achieved mAP50 scores of 0.70–0.75, with YOLOv9 demonstrating slightly better accuracy and inference speed, while RT-DETR exhibited faster training convergence. Additionally, a comparison between YOLOv5 and YOLOv9 revealed a 10% improvement in mAP50, highlighting the rapid advancements in computer vision in recent years. Lastly, we identify and discuss various alternative hardware solutions for data collection—in addition to drones, these include robotic platforms, climbing robots, and smart hangars—and discuss key challenges for their deployment, such as regulatory constraints, human–robot integration, and weather resilience. The fundamental contribution of this paper is to underscore the potential of computer vision for aircraft skin defect detection while emphasizing that further research is still required to address existing limitations. Full article

(This article belongs to the Section Aeronautics)

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24 pages, 11050 KiB

Open AccessArticle

Deep Reinforcement Learning Based Energy Management Strategy for Vertical Take-Off and Landing Aircraft with Turbo-Electric Hybrid Propulsion System

by Feifan Yu, Wang Tang, Jiajie Chen, Jiqiang Wang, Xiaokang Sun and Xinmin Chen

Aerospace 2025, 12(4), 355; https://doi.org/10.3390/aerospace12040355 - 17 Apr 2025

Due to the limitations of pure electric power endurance, turbo-electric hybrid power systems, which offer a high power-to-weight ratio, present a reliable solution for medium- and large-sized vertical take-off and landing (VTOL) aircraft. Traditional energy management strategies often fail to minimize fuel consumption [...] Read more.

Due to the limitations of pure electric power endurance, turbo-electric hybrid power systems, which offer a high power-to-weight ratio, present a reliable solution for medium- and large-sized vertical take-off and landing (VTOL) aircraft. Traditional energy management strategies often fail to minimize fuel consumption across the entire flight profile while meeting power demands under varying flight conditions. To address this issue, this paper proposes a deep reinforcement learning (DRL)-based energy management strategy (EMS) specifically designed for turbo-electric hybrid propulsion systems. Firstly, the proposed strategy employs a Prior Knowledge-Guided Deep Reinforcement Learning (PKGDRL) method, which integrates domain-specific knowledge into the Deep Deterministic Policy Gradient (DDPG) algorithm to improve learning efficiency and enhance fuel economy. Then, by narrowing the exploration space, the PKGDRL method accelerates convergence and achieves superior fuel and energy efficiency. Simulation results show that PKGDRL has a strong generalization capability in all operating conditions, with a fuel economy difference of only 1.6% from the offline benchmark of the optimization algorithm, and in addition, the PKG module enables the DRL method to achieve a huge improvement in terms of fuel economy and convergence rate. In particular, the prospect theory (PT) in the PKG module improves fuel economy by 0.81%. Future research will explore the application of PKGDRL in the direction of real-time total power prediction and adaptive energy management under complex operating conditions to enhance the generalization capability of EMS. Full article

(This article belongs to the Section Aeronautics)

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20 pages, 9770 KiB

Open AccessArticle

Damage Evaluation of Typical Aircraft Panel Structure Subjected to High-Speed Fragments

by Yitao Wang, Teng Zhang, Hanzhe Zhang, Liying Ma, Yuting He and Antai Ren

Aerospace 2025, 12(4), 354; https://doi.org/10.3390/aerospace12040354 - 17 Apr 2025

This study explores the damage behavior of typical titanium alloy aircraft panel structures under high-speed fragment impacts via ballistic experiments and FEM-SPH simulations. Using a ballistic gun and two-stage light gas gun, tests were conducted with spherical, rhombic, and rod-shaped fragments at 1100–2100 [...] Read more.

This study explores the damage behavior of typical titanium alloy aircraft panel structures under high-speed fragment impacts via ballistic experiments and FEM-SPH simulations. Using a ballistic gun and two-stage light gas gun, tests were conducted with spherical, rhombic, and rod-shaped fragments at 1100–2100 m/s to analyze damage morphology. The FEM-SPH method effectively modeled dynamic impacts, capturing primary penetration and debris cloud-induced secondary damage. Residual strength under tension was evaluated via multiple restart analysis, linking impact dynamics to post-damage mechanics. Experimental results revealed fragment-dependent damage modes: spherical fragments caused circular shear holes with conical/jet-like debris clouds; rhombic fragments induced irregular tearing and triangular perforations due to unstable flight; rod-shaped fragments produced elongated breaches with extensive plastic deformation in stringers. Numerical simulations accurately reproduced debris cloud diffusion and secondary effects like spallation. Residual strength analysis showed tensile capacity was governed by breach geometry and location: rhombic breaches (34.6 kN) had lower strength than circular/square ones (38.1–38.3 kN) due to tip stress concentration, while stringer-located damage increased ultimate load by 8–12% via structural redundancy. In conclusion, high-speed fragment impacts dominate shear/tensile tearing, with morphology dependent on fragment characteristics and impact conditions. Debris cloud-induced secondary damage must be considered in structural assessments. The FEM-SPH method is effective for complex damage simulation, while breach geometry and damage location are critical for residual strength. Stringer involvement enhances load-bearing capacity, highlighting component-level design importance for aircraft survivability. The study results and methodologies presented herein can serve as references for aircraft structural damage analysis, residual strength evaluation of battle-damaged structures, and survivability design. Full article

(This article belongs to the Special Issue Structural Dynamics Modelling, Aeroelastic Analysis and Experimental Verification Methods for Aircraft Systems)

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14 pages, 11276 KiB

Open AccessArticle

The Dynamic Response of Aluminum Alloy Plates Subjected to Multiple-Fragment Impacts Under Pre-Tensile Loading: A Numerical Study

by Yitao Wang, Teng Zhang, Hanzhe Zhang, Yuting He, Liying Ma and Antai Ren

Aerospace 2025, 12(4), 353; https://doi.org/10.3390/aerospace12040353 - 17 Apr 2025

This study presents an innovative numerical investigation into the synergistic effects of pre-tensile loading and multi-fragment hypervelocity impacts on thin-walled 7075-T6 aluminum alloy structures, addressing a critical gap in aircraft survivability design under realistic combat conditions. Utilizing an advanced finite element framework with [...] Read more.

This study presents an innovative numerical investigation into the synergistic effects of pre-tensile loading and multi-fragment hypervelocity impacts on thin-walled 7075-T6 aluminum alloy structures, addressing a critical gap in aircraft survivability design under realistic combat conditions. Utilizing an advanced finite element framework with stress dynamic relaxation preloading, the established model was rigorously validated against experimental gas-gun impact data, achieving less than 11% deviation in residual velocity. Distinct from prior single-impact studies, our work pioneers a systematic multi-parameter analysis encompassing multiple pre-stress levels, circumferential/linear fragment distributions, velocity gradients, and geometries. The findings of this parametric study establish a linkage between dynamic penetration mechanics and operational airframe stresses, offering guidelines for damage-tolerant design optimization in aircraft structures. Full article

(This article belongs to the Special Issue Structural Dynamics Modelling, Aeroelastic Analysis and Experimental Verification Methods for Aircraft Systems)

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25 pages, 1565 KiB

Open AccessArticle

Space Trajectory Planning with a General Reinforcement-Learning Algorithm

by Andrea Forestieri and Lorenzo Casalino

Aerospace 2025, 12(4), 352; https://doi.org/10.3390/aerospace12040352 - 16 Apr 2025

Space trajectory planning is a complex combinatorial problem that requires selecting discrete sequences of celestial bodies while simultaneously optimizing continuous transfer parameters. Traditional optimization methods struggle with the increasing computational complexity as the number of possible targets grows. This paper presents a novel [...] Read more.

Space trajectory planning is a complex combinatorial problem that requires selecting discrete sequences of celestial bodies while simultaneously optimizing continuous transfer parameters. Traditional optimization methods struggle with the increasing computational complexity as the number of possible targets grows. This paper presents a novel reinforcement-learning algorithm, inspired by AlphaZero, designed to handle hybrid discrete–continuous action spaces without relying on discretization. The proposed framework integrates Monte Carlo Tree Search with a neural network to efficiently explore and optimize space trajectories. While developed for space trajectory planning, the algorithm is broadly applicable to any problem involving hybrid action spaces. Applied to the Global Trajectory Optimization Competition XI problem, the method achieves competitive performance, surpassing state-of-the-art results despite limited computational resources. These results highlight the potential of reinforcement learning for autonomous space mission planning, offering a scalable and cost-effective alternative to traditional trajectory optimization techniques. Notably, all experiments were conducted on a single workstation, demonstrating the feasibility of reinforcement learning for practical mission planning. Moreover, the self-play approach used in training suggests that even stronger solutions could be achieved with increased computational resources. Full article

(This article belongs to the Special Issue Spacecraft Trajectory Design)

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30 pages, 8617 KiB

Open AccessReview

Progress and Development of Solid-Fuel Scramjet Technologies

by Wenfeng Yu, Yun Hu, Shenghai Zhao and Rongqiao Wang

Aerospace 2025, 12(4), 351; https://doi.org/10.3390/aerospace12040351 - 16 Apr 2025

The solid-fuel scramjet has become a potential power device for hypersonic missiles in the future and has important military application prospects due to its advantages in gas flow regulation, flame stability, and blended combustion efficiency. This paper summarizes the research progress of three [...] Read more.

The solid-fuel scramjet has become a potential power device for hypersonic missiles in the future and has important military application prospects due to its advantages in gas flow regulation, flame stability, and blended combustion efficiency. This paper summarizes the research progress of three types of solid-fuel scramjet, including a large number of landmark numerical and experimental results. At the same time, the research progress of supersonic steady combustion and combustion enhancement technology, thermal protection technology, and the improvement of solid-fuel and combustion performance are reviewed. On this basis, the key technologies of the solid solid-fueled scramjet are summarized, and several internal scientific problems are summarized, such as the combustion organization strategy of the wide velocity domain solid rocket scramjet, efficient combustion chamber loading and thermal bulking technology, combustion instability, etc. Finally, some suggestions for the future development of the solid-fuel scramjet are put forward. Full article

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

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21 pages, 2562 KiB

Open AccessArticle

A New Aerodynamic Domain Model (ADM) for Enhancing the Reliability of Spin Flight Vehicle Simulations

by Shenghui Lv and Zhong Su

Aerospace 2025, 12(4), 350; https://doi.org/10.3390/aerospace12040350 - 16 Apr 2025

A spin flight vehicle is characterized by its inherent active or passive spinning motion, resulting in complex movements that pose challenges for accurately calculating aerodynamic forces. This often leads to significant discrepancies between simulation results and actual performance. To address the low reliability [...] Read more.

A spin flight vehicle is characterized by its inherent active or passive spinning motion, resulting in complex movements that pose challenges for accurately calculating aerodynamic forces. This often leads to significant discrepancies between simulation results and actual performance. To address the low reliability of simulations for single-wing spin flight vehicles caused by difficulties in aerodynamic force estimation, this paper introduces the concept of an aerodynamic domain model. Based on the configuration of a specific single-wing spin flight vehicle, the model applies rigid body dynamics and uses blade element-momentum theory for aerodynamic calculations. By considering both relative and absolute error characteristics between actual and computed aerodynamic values, the aerodynamic domain model is established with explicit methods for determining error factor function bounds. The theoretical and practical value of the model is demonstrated through a simulation example, showing its ability to represent the range of true aerodynamic forces and moments experienced by the vehicle. This approach reduces the dependence on highly accurate aerodynamic calculations while maintaining engineering feasibility, enabling effective flight risk assessments within a specified range. Full article

(This article belongs to the Section Aeronautics)

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23 pages, 24870 KiB

Open AccessArticle

A Strategy for Predicting Transonic Compressor Performance at Low Reynolds Number

by Dalin Shi, Tianyu Pan, Xingyu Zhu and Zhiping Li

Aerospace 2025, 12(4), 349; https://doi.org/10.3390/aerospace12040349 - 16 Apr 2025

A low Reynolds number (Re) environment leads to severe deterioration in compressor performance, and it is necessary and challenging to accurately predict performance at a low Re during the design phase of a compressor. This study first reveals the mechanism of typical flow [...] Read more.

A low Reynolds number (Re) environment leads to severe deterioration in compressor performance, and it is necessary and challenging to accurately predict performance at a low Re during the design phase of a compressor. This study first reveals the mechanism of typical flow characteristics in transonic compressor at a low Re via simulations. When comparing the cases with different Re, the equivalent blade profile variation due to the growth of the boundary-layer thickness is found to be the main reason for changing the flow field. On the basis of boundary-layer theory, a prediction model of the equivalent profile is developed for the viscous effect on the boundary layer, and a multiline strategy is applied to calculate the blade-load radial redistribution. The equivalent blade prediction error at different Re is up to 7.8% compared to the CFD results. Ultimately, this strategy improves the radial spatial resolution compared to the original method and is able to predict the compressor performance at a low Re with pressure ratio and efficiency errors of 0.23% and 1.8%, respectively. Full article

(This article belongs to the Section Aeronautics)

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