Aerospace

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

Viewed by 316

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

Viewed by 274

Abstract

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

Viewed by 305

Abstract

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

Viewed by 208

Abstract

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

Viewed by 507

Abstract

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

Viewed by 268

Abstract

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

Viewed by 245

Abstract

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

Viewed by 242

Abstract

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

Viewed by 380

Abstract

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

Viewed by 624

Abstract

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

Viewed by 164

Abstract

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

Viewed by 201

Abstract

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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20 pages, 8622 KiB

Open AccessArticle

Life Prediction Modeling Based on FOA and Interface Shapes Simulation Applicability Analysis of TBCs

by Xiao Hu, Jing Tian, Yanting Ai, Yudong Yao, Tiannan Bao and Peng Guan

Aerospace 2025, 12(4), 348; https://doi.org/10.3390/aerospace12040348 - 16 Apr 2025

Viewed by 220

Abstract

Subjective selection of simulation interface shapes may introduce errors in the strength and fatigue analysis of thermal barrier coatings (TBCs). However, the applicability of different interface shapes for the TBCs simulation has rarely been investigated. Based on the TBCs thermal fatigue experiment, a [...] Read more.

Subjective selection of simulation interface shapes may introduce errors in the strength and fatigue analysis of thermal barrier coatings (TBCs). However, the applicability of different interface shapes for the TBCs simulation has rarely been investigated. Based on the TBCs thermal fatigue experiment, a finite element model is established and combined with the Fruit Fly Optimization Algorithm (FOA), a TBCs life prediction model is established. Then, five typical interface shapes, sawtooth, sinusoidal, semicircular, elliptical, and trapezoidal, are identified based on fine-scale photographs of the real interface morphology of the TBCs. Finally, the interface shape with the highest simulation applicability is identified through interface stress state analysis and life prediction error analysis, and verified through experiment. The results show that the stress maximum location of the sawtooth and trapezoidal interface shapes is inconsistent with the experimental onset of damage in TBCs, which proves that the applicability of the two shapes in the simulation of TBCs is not high. When applying equivalent strain for life prediction, the life prediction errors for the semicircular interface shape, elliptical interface shape, and sinusoidal interface shape are 72.84%, 61.74%, and 58.72%, respectively. The lowest life prediction error is obtained by using data from the sinusoidal interface shape. Therefore, the sinusoidal interface shape is the most applicable simplified shape for TBC simulation. Applying sinusoidal interface shape for additional TBCs life prediction with only 13.52% error, which verifies the accuracy of the methodology and conclusions of this study. These conclusions can inform accurate strength and fatigue simulation analysis of TBCs. Full article

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20 pages, 8475 KiB

Open AccessArticle

Confidence-Based Fusion of AC-LSTM and Kalman Filter for Accurate Space Target Trajectory Prediction

by Caiyun Wang, Jirui Zhang, Jianing Wang and Yida Wu

Aerospace 2025, 12(4), 347; https://doi.org/10.3390/aerospace12040347 - 16 Apr 2025

Viewed by 329

Abstract

The accurate prediction of space target trajectories is critical for aerospace defense and space situational awareness, yet it remains challenging due to complex nonlinear dynamics, measurement noise, and environmental uncertainties. This study proposes a confidence-based dual-model fusion framework that separately processes linear and [...] Read more.

The accurate prediction of space target trajectories is critical for aerospace defense and space situational awareness, yet it remains challenging due to complex nonlinear dynamics, measurement noise, and environmental uncertainties. This study proposes a confidence-based dual-model fusion framework that separately processes linear and nonlinear trajectory components to enhance prediction accuracy and robustness. The Attention-Based Convolutional Long Short-Term Memory (AC-LSTM) network is designed to capture nonlinear motion patterns by leveraging temporal attention mechanisms and convolutional layers while also estimating confidence levels via a signal-to-noise ratio (SNR)-based multitask learning approach. In parallel, the Kalman Filter (KF) efficiently models quasi-linear motion components, dynamically estimating its confidence through real-time residual monitoring. A confidence-weighted fusion mechanism adaptively integrates the predictions from both models, significantly improving overall prediction performance. Experimental results on simulated radar-based noisy trajectory data demonstrate that the proposed method outperforms conventional algorithms, offering superior precision and robustness. This approach holds great potential for applications in pace situational awareness, orbital object tracking, and space trajectory prediction. Full article

(This article belongs to the Special Issue Precise Orbit Determination of the Spacecraft)

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21 pages, 6883 KiB

Open AccessArticle

Temperature Field and Thermal Stress Analysis of a Composite Wing Electric Heating System with Delamination Damage

by Xuelan Hu, Ziyi Wang, Xiaoqing Sun, Hengyu Chu, Jiawei Yao and Yifan Niu

Aerospace 2025, 12(4), 346; https://doi.org/10.3390/aerospace12040346 - 15 Apr 2025

Viewed by 331

Abstract

Electrothermal anti-/de-icing systems are widely used in aircraft, and the structures of these systems generally consist of multiple layers laminated together. In service, laminated structures are prone to structural deformation and delamination, which can significantly affect heat conduction. Therefore, it is essential to [...] Read more.

Electrothermal anti-/de-icing systems are widely used in aircraft, and the structures of these systems generally consist of multiple layers laminated together. In service, laminated structures are prone to structural deformation and delamination, which can significantly affect heat conduction. Therefore, it is essential to study the temperature field of these electrically heated anti-icing structures during operation and analyse the impact of delamination damage on the temperature distribution. In this thesis, a dynamic multiphysical field study of an electric heating anti-icing structure is conducted using a thermal expansion layer-by-layer/3D solid element method. By studying the electric heating process of composite plates experiencing pre-positioned delamination, the thermal expansion layer-by-layer/3D solid element method considers the thermal convection boundary conditions as well as a constant heat source. In addition, to considering the influences of the geometric shape and delamination damage, we apply the thermal expansion layer-by-layer/3D solid element method to the electric heating anti-icing process of aerofoil structures using a coordinate transformation matrix. The calculations show that when delamination damage is located above the heating layer, the maximum temperature of the structure reaches 450 °C at 50 s, which severely affects the normal functioning of the structure. Additionally, the surface temperature of the anti-icing system decreases to the ambient temperature at the delamination. In contrast, delamination damage located below the heating layer has a minimal effect on the surface temperature distribution. Moreover, the damage caused by multiple types of damage is greater than that caused by a single type of damage. Full article

(This article belongs to the Section Aeronautics)

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21 pages, 10134 KiB

Open AccessArticle

Development of a Modular Test Rig for In-Flight Validation of a Multi-Hole Probe Onboard the e-Genius-Mod

by Eskil Jonas Nussbaumer, Sara Hijazi, Dominique Paul Bergmann, Hanno Streit and Andreas Strohmayer

Aerospace 2025, 12(4), 345; https://doi.org/10.3390/aerospace12040345 - 15 Apr 2025

Viewed by 220

Abstract

Scaled flight demonstrators have played an important part throughout the history of aviation. Ranging from aviation pioneers to renowned institutions like the National Aeronautics and Space Administration (NASA), many actors have relied on miniaturized models in both research and development. Despite the age [...] Read more.

Scaled flight demonstrators have played an important part throughout the history of aviation. Ranging from aviation pioneers to renowned institutions like the National Aeronautics and Space Administration (NASA), many actors have relied on miniaturized models in both research and development. Despite the age of the method, sub-scale models are still being used as a low-cost option for flight tests in realistic flight conditions. One utilization aspect that is becoming increasingly popular is as a flying test platform for the development and testing of new aviation technologies or capabilities. By conducting flight tests in real atmospheric conditions, it enables a low-cost link between analytical studies and full-scale testing, consequently closing the gap between Technology Readiness Levels (TRLs) 4 and 6, which is both time- and cost-efficient. For this paper, the utilization of the e-Genius-Mod, a modular scaled version of the all-electric e-Genius aircraft, as a versatile platform for testing new technologies is being investigated. As a case study, a multi-hole probe (MHP) is installed onto the aircraft through a custom-made wing adapter and connected to an independent data collection system. By using Computational Fluid Dynamics (CFD) simulations and wind-tunnel tests, the probe installation is validated, paving the way for upcoming flight tests. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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23 pages, 625 KiB

Open AccessReview

A Review of Detect and Avoid Standards for Unmanned Aircraft Systems

by Marcel Riedel

Aerospace 2025, 12(4), 344; https://doi.org/10.3390/aerospace12040344 - 15 Apr 2025

Viewed by 416

Abstract

When operating an unmanned aircraft system within the specific category beyond Air Risk Class a or within the certified category, a detect and avoid system is required in order to mitigate the risk of colliding with manned aircraft. To demonstrate compliance with the [...] Read more.

When operating an unmanned aircraft system within the specific category beyond Air Risk Class a or within the certified category, a detect and avoid system is required in order to mitigate the risk of colliding with manned aircraft. To demonstrate compliance with the regulatory requirements, several standards have been developed that propose a range of technologies and requirements for different operational environments. This paper represents an entry point for understanding the key aspects of this application area. Important concepts, like remain well clear, collision avoidance, and encounter modeling, are elucidated. Furthermore, available standards for detect and avoid systems for unmanned aircraft are presented. The introduced documents are analyzed and summarized with respect to their applicability, their scope, and their major characteristics. Further, a comparison between the standards is given where possible. Some documents describe the system and the corresponding requirements in their entirety, while others focus on equipment and component requirements. Nevertheless, the presented standards are sufficient to cover a wide range of detect and avoid applications. Essential aspects of these standards are listed in a condensed manner, enabling the reader to choose a suitable standard for a given operation. Full article

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

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22 pages, 24655 KiB

Open AccessArticle

Numerical Analyses of Aerodynamic and Aeroacoustic Interaction Characteristics of Rear-Mounted Propeller on Highspeed Helicopter

by Dazhi Sun, Xi Chen, Qijun Zhao and Weicheng Bao

Aerospace 2025, 12(4), 343; https://doi.org/10.3390/aerospace12040343 - 15 Apr 2025

Viewed by 369

Abstract

To study the interference effects of the fuselage/rear-mounted propeller on the aerodynamic and aeroacoustic characteristics at a forward speed of Ma = 0.323, a multi-component flowfield simulation and an aeroacoustic prediction method were employed. Firstly, hybrid grids were adopted in the embedded grid [...] Read more.

To study the interference effects of the fuselage/rear-mounted propeller on the aerodynamic and aeroacoustic characteristics at a forward speed of Ma = 0.323, a multi-component flowfield simulation and an aeroacoustic prediction method were employed. Firstly, hybrid grids were adopted in the embedded grid system, and a new boundary identification method was developed to address the overlap problem by adjusting the grid boundary based on entities. The simulations were based on the URANS and FW-H equations. The employed numerical analysis methods were validated through comparisons with experimental data. Then, the aerodynamic and aeroacoustic characteristics of the propeller were analyzed, and the interference of the fuselage with the propeller was discussed in detail. Key findings included the following. Under fuselage interference, the sound pressure level (SPL) of the propeller at those observers near the forward flight direction increased dramatically, by more than 10 dB, especially in the range of two to six times the fundamental frequency. A downward vertical velocity reduced the SPLs beneath the fuselage, while an upward one had the opposite effect. The flat/vertical tails’ deceleration effect caused a thrust surge in the propeller, with most magnitudes around 20%. At different forward speeds, the thrust surge and SPL changes were similar. Full article

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

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20 pages, 1009 KiB

Open AccessArticle

Permeation Investigation of Carbon Fibre Reinforced Polymer Material for LH2 Storage Thermally Shocked and Mechanically Cycled at Cryogenic Temperature

by Giacomo Dreossi and Andrej Bernard Horvat

Aerospace 2025, 12(4), 342; https://doi.org/10.3390/aerospace12040342 - 14 Apr 2025

Viewed by 279

Abstract

To achieve the sustainability goals set for the European aviation sector, hydrogen-powered solutions are currently being investigated. Storage solutions are of particular interest, with liquid hydrogen tanks posing numerous challenges with regard to the structural integrity of materials at cryogenic temperatures, as well [...] Read more.

To achieve the sustainability goals set for the European aviation sector, hydrogen-powered solutions are currently being investigated. Storage solutions are of particular interest, with liquid hydrogen tanks posing numerous challenges with regard to the structural integrity of materials at cryogenic temperatures, as well as safety issues because of the high flammability of hydrogen. In this context and in the scope of the Horizon 2020 Clean Aviation Joint Undertaking (CAJU) project H2ELIOS, the gas permeability behavior of prepreg tape carbon fibre reinforced polymer (CFRP) material was studied. Investigations were performed after thermal shock to 20 K (liquid hydrogen immersion) as well as after a uniaxial stress application at 77 K to identify the shift from Fickian behavior after diverse aging conditions. Helium gas permeation was tested at room temperature (RT), and its representativeness to hydrogen permeation in a range of temperatures was considered in the study. The material’s permeation behavior was compared to ideal Fickian diffusion as a means of identifying related permeation barrier function degradation. Finally, it was possible to identify Fickian, near-Fickian, and non-Fickian behaviors and correlate them with the material’s preconditioning. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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35 pages, 16311 KiB

Open AccessArticle

Efficient Adaptive Robust Aerodynamic Design Optimization Considering Uncertain Inflow Variations for a Diffusion Airfoil Across All Operating Incidences

by Zhengtao Guo, Lei Bao, Chaolong Li, Xianzhong Gao and Wuli Chu

Aerospace 2025, 12(4), 341; https://doi.org/10.3390/aerospace12040341 - 14 Apr 2025

Viewed by 198

Abstract

The random fluctuations in inlet flow represent a common uncertainty in aero-engine compressors, necessitating the control of its effects through blade optimization design. To account for the impact of inlet flow fluctuations on performance in blade design optimization, an efficient multi-objective adaptive robust [...] Read more.

The random fluctuations in inlet flow represent a common uncertainty in aero-engine compressors, necessitating the control of its effects through blade optimization design. To account for the impact of inlet flow fluctuations on performance in blade design optimization, an efficient multi-objective adaptive robust aerodynamic design optimization (ARADO) method is proposed. The optimization method employs a novel sparse polynomial chaos expansion (PCE) and the advanced noisy Gaussian process regression (NGPR) technique is used to establish an initial stochastic surrogate model (SSM) containing statistical moments of aerodynamic performance. By introducing advanced sparse signal processing concepts, the sparce PCE significantly enhances the efficiency of acquiring each training sample for SSM. During the optimization process, the initial SSM autonomously updates based on historical optimization data, without requiring high precision across the entire design space. Compared to traditional model-based aerodynamic robust optimizations, the proposed ARADO method exhibits a faster convergence speed and achieves a superior average level of the optimal solution set. It also better balances various optimization objectives, concentrating the space distribution of optimal solutions closer to the average level. Ultimately, the ARADO is applied to the aerodynamic robust design of a high-load compressor airfoil across all operating incidences. The optimization results enhance aerodynamic performance while reducing performance diversity, thus aligning more closely with practical engineering requirements. Through data analysis of the optimal solutions, robust design guidelines for blade aerodynamic shapes are obtained, along with insights into the flow mechanisms that enhance aerodynamic robustness. Full article

(This article belongs to the Section Aeronautics)

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33 pages, 4378 KiB

Open AccessArticle

Public Acceptance of a Proposed Sub-Regional, Hydrogen–Electric, Aviation Service: Empirical Evidence from HEART in the United Kingdom

by Patrick Langdon, Grigorios Fountas, Clare McTigue and Jorge Eslava-Bautista

Aerospace 2025, 12(4), 340; https://doi.org/10.3390/aerospace12040340 - 14 Apr 2025

Viewed by 342

Abstract

This paper addresses public acceptance of a proposed sub-regional, hydrogen–electric, aviation service reporting initial empirical evidence from the UK HEART project. The objective was to assess public acceptance of a wide range of service features, including hydrogen power, electric motors, and pilot assistance [...] Read more.

This paper addresses public acceptance of a proposed sub-regional, hydrogen–electric, aviation service reporting initial empirical evidence from the UK HEART project. The objective was to assess public acceptance of a wide range of service features, including hydrogen power, electric motors, and pilot assistance automation, in the context of an ongoing realisable commercial plan. Both qualitative and quantitative data collection instruments were leveraged, including focus groups and stakeholder interviews, as well as the questionnaire-based Scottish National survey, coupled with the advanced discrete-choice modelling of the data. The results from each method are presented, compared, and contrasted, focusing on the strength, reliability, and validity of the data to generate insights into public acceptance. The findings suggest that public concerns were tempered by an incomplete understanding of the technology but were interpretable in terms of key service elements. Respondents’ concerns and opinions centred around hydrogen as a fuel, single-pilot automation, safety and security, disability and inclusion, environmental impact, and the perceived usefulness of novel service features such as terminal design, automation, and sustainability. The latter findings were interpreted under a joint framework of technology acceptance theory and the diffusion of innovation. From this, we drew key insights, which were presented alongside a discussion of the results. Full article

(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)

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42 pages, 13151 KiB

Open AccessArticle

End-to-End GNC Solution for Reusable Launch Vehicles

by Jacopo Guadagnini, Pietro Ghignoni, Fabio Spada, Gabriele De Zaiacomo and Afonso Botelho

Aerospace 2025, 12(4), 339; https://doi.org/10.3390/aerospace12040339 - 14 Apr 2025

Viewed by 317

Abstract

This paper presents an autonomous end-to-end guidance, navigation, and control (GNC) solution for a reusable launcher, addressing the challenges of precision pinpoint landing and reusability. The proposed GNC system integrates advanced onboard trajectory optimization and

H_{\infty}

control to ensure robust performance across [...] Read more.

This paper presents an autonomous end-to-end guidance, navigation, and control (GNC) solution for a reusable launcher, addressing the challenges of precision pinpoint landing and reusability. The proposed GNC system integrates advanced onboard trajectory optimization and

H_{\infty}

control to ensure robust performance across re-entry, aerodynamics, and landing phases. This work discusses the GNC design and definition and introduces the strategies adopted both for the guidance and the control design to handle rapidly varying dynamic environments and strict landing requirements. Particular attention is given to design choices in the guidance optimization problem and the control definition for each phase, which were made to enhance the harmonization of the guidance and control (G&C) system. The proposed GNC is integrated in a high-fidelity Functional Engineering Simulator (FES) and its robustness is assessed in a real-world scenario, considering a downrange landing mission of the RETALT1 (RETro propulsion Assisted Landing Technologies Two-Stage-To-Orbit vehicle) rocket. Full article

(This article belongs to the Special Issue Modeling, Simulation, and Control of Launch Vehicles)

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22 pages, 7152 KiB

Open AccessArticle

Finite Element Analysis of Structural Parameter Effects on Stiffness Nonlinearity Behavior in Aero-Engine Elastic Rings

by Yihang Shi, Jiaqi Li, Zhongyu Yang and Yinli Feng

Aerospace 2025, 12(4), 338; https://doi.org/10.3390/aerospace12040338 - 14 Apr 2025

Viewed by 323

Abstract

Elastic rings are extensively utilized in aero-engine rotor systems owing to their compact size and ease of assembly, where they play a critical role in vibration suppression during engine operation. The dynamic behavior of elastic rings is governed by their structural parameters, with [...] Read more.

Elastic rings are extensively utilized in aero-engine rotor systems owing to their compact size and ease of assembly, where they play a critical role in vibration suppression during engine operation. The dynamic behavior of elastic rings is governed by their structural parameters, with stiffness being a pivotal factor influencing the rotor system’s performance. This study employs finite element methods to investigate the effects of elastic ring structural parameters, particularly the geometric features of bosses and internal/external assembly clearances, on stiffness nonlinearity, with a focus on its mechanisms and contributing factors. The results reveal that stiffness nonlinearity emerges when the whirling radius exceeds a critical threshold. Specifically, increasing the boss width, reducing the boss height, or augmenting the number of bosses all attenuate stiffness nonlinearity under identical whirling radii. Furthermore, external clearances exhibit a stronger capability to suppress stiffness nonlinearity compared to internal clearances. Engineering insights suggest that maintaining a small clearance fit during assembly effectively mitigates stiffness nonlinearity, thereby enhancing the rotor’s dynamic performance. This study elucidates the stiffness nonlinearity behavior of elastic rings in practical applications and provides actionable guidance for their design and operational optimization in rotor systems. Full article

(This article belongs to the Special Issue Advances in Thermal Fluid, Dynamics and Control)

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21 pages, 3764 KiB

Open AccessArticle

Multi-Objective Optimization and Reliability Assessment of Multi-Layer Radiation Shielding for Deep Space Missions

by Shukai Guan, Guicui Fu, Bo Wan, Xiangfen Wang and Zhiqiang Chen

Aerospace 2025, 12(4), 337; https://doi.org/10.3390/aerospace12040337 - 14 Apr 2025

Viewed by 332

Abstract

This study proposes an advanced space radiation shielding design method that integrates multi-objective optimization with reliability evaluation to mitigate the impact of harsh space radiation environments on electronic systems. A genetic algorithm is employed to optimize multi-layer shielding configurations with respect to radiation [...] Read more.

This study proposes an advanced space radiation shielding design method that integrates multi-objective optimization with reliability evaluation to mitigate the impact of harsh space radiation environments on electronic systems. A genetic algorithm is employed to optimize multi-layer shielding configurations with respect to radiation dose reduction, mass efficiency, and structural thickness. To ensure practical applicability, a reliability evaluation framework incorporating uncertainty factors is developed, where shielding designs are considered acceptable when the risk confidence level (CL) remains below 5%. A case study simulating long-duration deep space missions demonstrates that the optimized five-layer shielding configuration reduces the radiation-induced failure rate by approximately 57%, enhancing the long-term reliability of core electronic components to 0.94 over a five-year mission. These findings validate the effectiveness of the proposed approach in supporting the development of reliable, lightweight radiation shielding for future space missions. Full article

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

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20 pages, 5172 KiB

Open AccessArticle

A Flight Slot Optimization Model for Beijing-Tianjin-Hebei Airport Cluster Considering Capacity Fluctuation Factor

by Jie Ren, Shiru Qu, Lili Wang, Changjie Liu, Lijing Ma and Zhiyuan Sun

Aerospace 2025, 12(4), 336; https://doi.org/10.3390/aerospace12040336 - 14 Apr 2025

Viewed by 290

Abstract

The rapid expansion of China’s civil aviation sector, particularly within the Beijing-Tianjin-Hebei airport cluster, has led to significant airspace congestion and operational inefficiencies. This study develops a dynamic flight slot allocation model that integrates both airport and airspace capacity constraints, accounting for real-time [...] Read more.

The rapid expansion of China’s civil aviation sector, particularly within the Beijing-Tianjin-Hebei airport cluster, has led to significant airspace congestion and operational inefficiencies. This study develops a dynamic flight slot allocation model that integrates both airport and airspace capacity constraints, accounting for real-time fluctuations in resource availability. The model aims to optimize slot distribution, minimize delays, and enhance operational efficiency by adapting to variations in airport and waypoint capacities, offering a more flexible solution compared with traditional static approaches. A case study based on real-world data from the Beijing-Tianjin-Hebei region demonstrates the model’s effectiveness. Computational experiments show that incorporating capacity fluctuations significantly reduces the need for slot adjustments, particularly at secondary airports with volatile demand. The results indicate a marked improvement in operational efficiency, including reduced adjustment times and fewer affected flights. This research underscores the value of adaptive data-driven strategies in managing complex air traffic systems and provides valuable insights for policymakers and aviation authorities. Future research could extend this work by incorporating additional dynamic factors, such as weather conditions and emerging technologies, to further enhance the sustainability and efficiency of air traffic management. Full article

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

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18 pages, 11147 KiB

Open AccessArticle

Numerical Study of Wind Tunnel Wall Effects on Icing Cloud Distribution and Water Collection in Aero-Engine Nacelles

by Cong Li, Ningli Chen, Xian Yi and Qingren Lai

Aerospace 2025, 12(4), 335; https://doi.org/10.3390/aerospace12040335 - 13 Apr 2025

Viewed by 397

Abstract

Icing wind tunnel tests play a critical role in evaluating ice accretion on aero-engine nacelles. However, the effects of the wind tunnel wall (WTW) on the dynamics of the icing cloud remain insufficiently quantified. This study employs an experimentally validated Eulerian–Eulerian multiphase approach [...] Read more.

Icing wind tunnel tests play a critical role in evaluating ice accretion on aero-engine nacelles. However, the effects of the wind tunnel wall (WTW) on the dynamics of the icing cloud remain insufficiently quantified. This study employs an experimentally validated Eulerian–Eulerian multiphase approach to quantify WTW-induced alterations in Liquid Water Content (LWC) distribution inside the nacelle and droplet collection efficiency (β) on its surfaces. The results show that the WTW-induced flow deflection redirects droplets toward the outer nacelle surface, leading to an increase in the maximum droplet collection efficiency (β_max) and the total collected water mass on the nacelle under baseline conditions (Mach Number = 0.206) and causing a banded regime of the deviation in LWC. Parametric analysis further shows that higher inflow velocities and Median Volumetric Diameters (MVDs) enhanced the WTW’s effect on the change in LWC inside the nacelle and increased the maximum droplet collection efficiency on the nacelle’s surface. However, the increase in the intake flow rates exhibits a counteracting trend for the effect of the WTW for both the deviation in LWC and the maximum droplet collection efficiency and the total collected water mass. The findings highlight the necessity of accounting for WTW effects in icing wind tunnel testing protocols to improve flight condition extrapolation accuracy. Full article

(This article belongs to the Special Issue Recent Advances in Icing Studies and Energy-Efficient De-Icing/Anti-Icing Technologies)

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14 pages, 2871 KiB

Open AccessArticle

Generating Large-Scale Datasets for Spacecraft Pose Estimation via a High-Resolution Synthetic Image Renderer

by Warunyu Hematulin, Patcharin Kamsing, Thaweerath Phisannupawong, Thanayuth Panyalert, Shariff Manuthasna, Peerapong Torteeka and Pisit Boonsrimuang

Aerospace 2025, 12(4), 334; https://doi.org/10.3390/aerospace12040334 - 12 Apr 2025

Viewed by 1217

Abstract

The trend toward conducting vision-based spacecraft pose estimation using deep neural networks, which necessitates accurately labeled datasets for training, is addressed in this paper. A method for generating an image regression-labeled dataset for spacecraft pose estimation through simulations involving Unreal Engine 5 is [...] Read more.

The trend toward conducting vision-based spacecraft pose estimation using deep neural networks, which necessitates accurately labeled datasets for training, is addressed in this paper. A method for generating an image regression-labeled dataset for spacecraft pose estimation through simulations involving Unreal Engine 5 is proposed herein. This work provides detailed algorithms for pose sampling and image generation, making it easy to reproduce the employed dataset. The dataset consists of images obtained under harsh lighting conditions and high-resolution backgrounds, featuring spacecraft models including Dragon, Soyuz, Tianzhou, and the ascent vehicle of Chang’E-6. The dataset comprises 40,000 high-resolution images, which are evenly distributed, with 10,000 images for each spacecraft model in scenes with both the Earth and the Moon. Each image is labeled with multivariate pose vectors that represent the relative position and attitude of the corresponding spacecraft with respect to the camera. This work emphasizes the critical role of realistic simulations in creating cost-effective synthetic datasets for training neural network-based pose estimators and publicly available for further study. Full article

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

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21 pages, 10168 KiB

Open AccessArticle

Theoretical and Numerical Study on a Scale Model Test of Planetary Cratering Impact

by He Lv, Qiguang He and Xiaowei Chen

Aerospace 2025, 12(4), 333; https://doi.org/10.3390/aerospace12040333 - 12 Apr 2025

Viewed by 266

Abstract

Our investigation delves into the scaling law governing planetary cratering impacts. We meticulously analyze the interplay between dimensionless parameters driving crater growth and the morphological transition of craters and construct the scaling analysis between the scale model tests and the prototype tests by [...] Read more.

Our investigation delves into the scaling law governing planetary cratering impacts. We meticulously analyze the interplay between dimensionless parameters driving crater growth and the morphological transition of craters and construct the scaling analysis between the scale model tests and the prototype tests by numerical simulation. With practical engineering applications in mind, we design scale model tests based on the experimental setups of geotechnical centrifuges, ensuring the robust validity of test designs. This meticulous approach is integral to achieving fidelity between simulations and experimental scenarios. Validation of our scale model tests is conducted through a numerical modeling framework, coupling the finite element-smoothed particle hydrodynamics adaptive method (FE-SPH). This validation procedure serves to bolster the reliability and credibility of our methodology, facilitating an accurate depiction of the cratering mechanism. Of particular interest is the investigation into the depth-to-diameter ratio of impact craters, wherein we explore its intricate relationship with projectile diameter and gravity. Through rigorous analysis, we delineate the transition diameter at which terrestrial impact craters manifest a transition from simple to complex morphologies, thereby shedding light on the underlying dynamics of crater formation. Moreover, our study meticulously scrutinizes the relationship of crater formation time between the scaling model tests and the prototype tests. Our research underscores the consistency of the crater depth–diameter ratio in the scale model tests and the prototype tests and affirms applicability in replicating prototype tests by scale model tests. Notably, our findings reveal compelling correlations between the depth-to-diameter ratio of impact craters and gravity, as well as projectile diameter, providing valuable insights into the governing dynamics of impact crater formation. These insights not only advance our fundamental understanding of planetary cratering processes but also hold implications for practical applications in planetary science and engineering. Full article

(This article belongs to the Special Issue Lunar, Planetary, and Small-Body Exploration)

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24 pages, 8419 KiB

Open AccessArticle

Design of Lattice-Based Energy-Absorbing Structure for Enhancing the Crashworthiness of Advanced Air Mobility

by Jaryong Cho, Eun Suk Lee, Jeong Ho Kim, Chang-Yull Lee and Jin Yeon Cho

Aerospace 2025, 12(4), 332; https://doi.org/10.3390/aerospace12040332 - 12 Apr 2025

Viewed by 371

Abstract

The development of advanced air mobility—an eco-friendly, next-generation transportation system—is underway and garners significant attention. Due to the novel propulsion concept of eVTOL (electric Vertical Take-Off and Landing) and its operation in low altitude, urban environment, regulations for commercialization have not yet been [...] Read more.

The development of advanced air mobility—an eco-friendly, next-generation transportation system—is underway and garners significant attention. Due to the novel propulsion concept of eVTOL (electric Vertical Take-Off and Landing) and its operation in low altitude, urban environment, regulations for commercialization have not yet been established. Consequently, related research on passenger safety in emergency landings is ongoing, and this study focuses on enhancing the crashworthiness of advanced air mobility. To ensure the crashworthiness of advanced air mobility, civil airworthiness standards were referenced to determine the appropriate test conditions, and a design criterion for developing an energy-absorbing structure was derived. In this study, lattice structures are considered for designing an energy-absorbing structure that satisfies the design criterion, and finite element analysis is conducted to predict the performance of lattice structures. Based on the predicted data, surrogate models are constructed using the Kriging method according to the type of lattice structure. To verify the data obtained from numerical models, representative structures are manufactured using EBM (Electron Beam Melting) technology, and compressive tests are conducted to obtain the force–displacement curves. The test data are compared with the numerical data, and it is confirmed that the test data show good agreement with the numerical data. After this confirmation, the constructed surrogate models are utilized to select a lattice-based energy-absorbing structure that satisfies the crashworthiness-related design criterion. Finally, a crash simulation of a vertical drop test is carried out using the selected lattice structure, and results indicate that the resulting acceleration due to the collision is below the human tolerance limit, thereby verifying the crashworthiness of the energy-absorbing structure. Full article

(This article belongs to the Section Aeronautics)

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21 pages, 31004 KiB

Open AccessArticle

Online Estimation Method and Verification of Sampling Mass for Lunar Drilling in the Chang’E-6 Mission

by Gao Zhang, Lei Guo, Weiwei Zhang, Shengyuan Jiang, Xiangjin Deng, Nai Zhang and Zongquan Deng

Aerospace 2025, 12(4), 331; https://doi.org/10.3390/aerospace12040331 - 11 Apr 2025

Viewed by 287

Abstract

The Chang’E-6 lunar mission successfully collected the lunar back surface and subsurface lunar regolith by excavating and drilling and returned the lunar regolith samples to the earth. Drilling–sampling system exhibits highly nonlinear characteristics due to the stratified structure of lunar regolith and unknown [...] Read more.

The Chang’E-6 lunar mission successfully collected the lunar back surface and subsurface lunar regolith by excavating and drilling and returned the lunar regolith samples to the earth. Drilling–sampling system exhibits highly nonlinear characteristics due to the stratified structure of lunar regolith and unknown physical property parameters, making it prone to abnormal operating conditions and sampling disturbances. Furthermore, constrained by extraterrestrial environmental limitations, the system can only obtain health parameters, operational protocol parameters, and drilling status parameters while lacking direct measurement data on sampling mass. The development of online estimation methods for sampling mass under nonlinear and under-sensing characteristics poses significant technical challenges. Based on the mechanism of machine–regolith interaction and the experimental data of ground drilling and sampling, this paper constructs a sampling status identification model and a fuzzy pre-judgment model of sampling mass based on the downhole WOB based on the response characteristic parameters of the drilling–sampling stage. According to the telemetry data of Chang’E-6 lunar surface drilling–coring operation, the drilling–sampling mass is predicted to be 292.4 g, and the error between the predicted result and the actual sampling mass of 320 g is within 10%. This estimation method provides a new idea for the prediction of the fidelity sampling efficiency of extraterrestrial objects. Full article

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

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