Aerospace

22 pages, 2211 KB

Open AccessArticle

Fire Control Radar Fault Prediction with Real-Flight Data

by Minyoung Kim, Ikgyu Lee, Seon-Ho Jeong, Dawn An and Byoungserb Shim

Aerospace 2025, 12(10), 945; https://doi.org/10.3390/aerospace12100945 - 21 Oct 2025

Viewed by 410

Unexpected failures of avionics equipment critically affect flight safety, operational availability, and maintenance costs. To address these issues, Condition-Based Maintenance Plus (CBM+) has emerged as a strategy to optimize maintenance timing based on equipment condition rather than fixed schedules. However, while aviation research [...] Read more.

Unexpected failures of avionics equipment critically affect flight safety, operational availability, and maintenance costs. To address these issues, Condition-Based Maintenance Plus (CBM+) has emerged as a strategy to optimize maintenance timing based on equipment condition rather than fixed schedules. However, while aviation research has largely focused on engines and structures, studies on avionics systems remain limited, often relying on simulations. This study proposes a novel data-driven approach to predict avionics equipment failures using actual aircraft operational data. Maneuver-related sequences were analyzed to investigate correlations between flight patterns and equipment faults, and a two-stage framework was developed. In the feature extraction stage, a CNN-LSTM encoder compresses 10 s maneuver sequences into compact yet informative representations. In the fault prediction stage, AI models classify failures of the Fire Control Radar based on these features. Experiments with real flight data validated the effectiveness of the method, showing that the CNN-LSTM encoder preserved essential maneuver information, while the combination of Standard Scaling and Multi-Layer Perceptron achieved the best performance, with a maximum Fault Recall of 98%. These findings demonstrate the feasibility of practical CBM+ implementation for avionics equipment using only flight data, providing a promising solution to improve maintenance efficiency and aviation safety. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

23 pages, 6319 KB

Open AccessArticle

Coordinated Trajectory Planning of Discrete-Serpentine Heterogeneous Multi-Arm Space Robot for Capturing Tumbling Targets Using Manipulability Optimization

by Zhonghua Hu, Chuntao Li, Qun Sun, Jianqing Peng and Wenshuo Li

Aerospace 2025, 12(10), 944; https://doi.org/10.3390/aerospace12100944 - 21 Oct 2025

Viewed by 269

Abstract

The discrete-serpentine heterogeneous multi-arm space robot (DSHMASR) has more advantages than single discrete space robots or single serpentine space robots in complex tasks of on-orbit servicing. However, the mechanical structure complexity of the DSHMASR poses challenges for modeling and motion planning. In this [...] Read more.

The discrete-serpentine heterogeneous multi-arm space robot (DSHMASR) has more advantages than single discrete space robots or single serpentine space robots in complex tasks of on-orbit servicing. However, the mechanical structure complexity of the DSHMASR poses challenges for modeling and motion planning. In this paper, a coupled kinematic model and a coordinated trajectory planning method for the DSHMASR were proposed to address these issues. Firstly, an uncontrolled satellite and the DSHMASR were modeled based on the momentum conservation law. The generalized Jacobian matrix J_g of the space robotic system was derived. Secondly, the manipulation capability of the DSHMASR was analyzed based on the null-space of J_g. Furthermore, the cooperative capturing-monitoring trajectory planning method for DSHMASR was presented through the manipulability optimization. The expected trajectory of each arm’s tip can be obtained by pose deviations and velocity deviations between the tip and the target point. Additionally, the optimized joint velocities of each arm were calculated by combining differential kinematics and manipulability optimization. Therefore, the manipulability of DSHMASR in the direction of the capture operation was enhanced simultaneously as it approached the target satellite. Finally, the proposed algorithm was demonstrated by establishing the Adams–Simulink co-simulation model. Comparisons with traditional approaches further confirm the outperformance of the proposed method in terms of manipulation capability. Full article

(This article belongs to the Special Issue Space Robotics and Embodied Intelligence: Advancing Autonomous Exploration)

► Show Figures

Figure 1

21 pages, 2653 KB

Open AccessArticle

Path Planning and Optimization of Space Robots on Satellite Surfaces Based on an Improved A* Algorithm and B-Spline Curves

by Xingchen Liu, Wenya Zhou, Changhao Zhai, Silin Ge and Zhengyou Xie

Aerospace 2025, 12(10), 943; https://doi.org/10.3390/aerospace12100943 - 21 Oct 2025

Viewed by 384

Abstract

Space robots are vital for in-orbit maintenance of large satellites, but dense payloads and complex surface structures pose challenges for safe crawling operations. This study proposes an improved trajectory planning framework for three-dimensional satellite surfaces. In the path search stage, the traditional A* [...] Read more.

Space robots are vital for in-orbit maintenance of large satellites, but dense payloads and complex surface structures pose challenges for safe crawling operations. This study proposes an improved trajectory planning framework for three-dimensional satellite surfaces. In the path search stage, the traditional A* algorithm is enhanced with traction cost, reflecting surface adhesion, and proximity cost, ensuring collision avoidance. The resulting comprehensive cost function integrates path length, safety, and feasibility, producing paths more consistent with real mobility constraints. In the smoothing stage, cubic B-spline curves refine the discrete path, with real-time collision detection embedded in the optimization of control points to prevent trajectory penetration. Simulations show that the method achieves millisecond-level planning, with path length reduced by 6.82% and trajectory smoothness significantly improved, eliminating the phenomenon of sharp turns with folded corners. The approach ensures continuous, stable, and collision-free movement of space robots, highlighting its potential for reliable in-orbit operations. Full article

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

► Show Figures

Figure 1

32 pages, 12377 KB

Open AccessArticle

Joint Estimation of Attitude and Optical Properties of Uncontrolled Space Objects from Light Curves Considering Atmospheric Effects

by Jorge Rubio, Adrián de Andrés, Carlos Paulete, Ángel Gallego and Diego Escobar

Aerospace 2025, 12(10), 942; https://doi.org/10.3390/aerospace12100942 - 19 Oct 2025

Viewed by 345

Abstract

The unprecedented increase in the number of objects orbiting the Earth necessitates a comprehensive characterisation of these objects to improve the effectiveness of Space Surveillance and Tracking (SST) operations. In particular, accurate knowledge of the attitude and physical properties of space objects has [...] Read more.

The unprecedented increase in the number of objects orbiting the Earth necessitates a comprehensive characterisation of these objects to improve the effectiveness of Space Surveillance and Tracking (SST) operations. In particular, accurate knowledge of the attitude and physical properties of space objects has become critical for space debris mitigation measures, since these parameters directly influence major perturbation forces like atmospheric drag and solar radiation pressure. Characterising a space object beyond its orbital position improves the accuracy of SST activities such as collision risk assessment, atmospheric re-entry prediction, and the design of Active Debris Removal (ADR) and In-Orbit Servicing (IOS) missions. This study presents a novel approach for the simultaneous estimation of the attitude and optical reflective properties of uncontrolled space objects with known shape using light curves. The proposed method also accounts for atmospheric effects, particularly the Aerosol Optical Depth (AOD), a highly variable parameter that is difficult to determine through on-site measurements. The methodology integrates different estimation, optimisation, and data analysis techniques to achieve an accurate, robust, and computationally efficient solution. The performance of the method is demonstrated through the analysis of a simulated scenario representative of realistic operational conditions. Full article

(This article belongs to the Special Issue Advances in Space Surveillance and Tracking)

► Show Figures

Figure 1

14 pages, 6132 KB

Open AccessArticle

Correlating the Impact Severity of Spherical and Non-Spherical Projectiles at Hypervelocity

by Patrick Domingo and Igor Telichev

Aerospace 2025, 12(10), 941; https://doi.org/10.3390/aerospace12100941 - 19 Oct 2025

Viewed by 281

Abstract

The design of spacecraft protection against orbital debris (OD) is generally based on experiments and models involving spherical projectiles. However, observations of collision fragments from ground-based satellite impact experiments have shown that orbital debris is non-spherical in shape. To accommodate non-spherical projectiles in [...] Read more.

The design of spacecraft protection against orbital debris (OD) is generally based on experiments and models involving spherical projectiles. However, observations of collision fragments from ground-based satellite impact experiments have shown that orbital debris is non-spherical in shape. To accommodate non-spherical projectiles in spacecraft protection measures, a relationship between spherical projectiles and their threat-equivalent non-spherical counterparts was established. Cylindrical projectiles featuring adjustable Length-to-Diameter (L/D) ratios were employed to simulate the projectile shape effect on the bumper performance under hypervelocity impact. The L/D ratio spanned a range from L/D = 1/3, representing a “flake” shape, through L/D = 1 for a “nugget” configuration and extended up to L/D = 5/3, representing a “straight rod” configuration. The numerical analysis utilized the smoothed-particle hydrodynamics technique, demonstrating that projectile geometry significantly influenced the threat posed by projectile fragments to the objects behind the bumper. The established projectile threat relationship can be applied to assess the ability of the existing OD bumpers to withstand non-spherical projectiles by representing them with an equivalent sphere. Utilizing this approach can contribute to decreasing uncertainty and enhancing the protection of spacecraft when encountering irregularly shaped OD particles. Full article

(This article belongs to the Special Issue Development of Novel Orbital Debris Protection Systems)

► Show Figures

Figure 1

18 pages, 7695 KB

Open AccessArticle

Effect of Axial Offset, Index Angle, and RPM Differential on the Aerodynamics of Co-Axial Co-Rotating Propellers

by Su Won Jeon and Sang Wook Lee

Aerospace 2025, 12(10), 940; https://doi.org/10.3390/aerospace12100940 - 18 Oct 2025

Viewed by 356

Abstract

Coaxial co-rotating (CCR) propeller systems provide structural simplicity, compactness, and high disk loading, making them attractive for an Electric Distributed Propulsion System (EDPS). However, aerodynamic interactions between the upper and lower propellers can lead to efficiency losses, and the effects of key design [...] Read more.

Coaxial co-rotating (CCR) propeller systems provide structural simplicity, compactness, and high disk loading, making them attractive for an Electric Distributed Propulsion System (EDPS). However, aerodynamic interactions between the upper and lower propellers can lead to efficiency losses, and the effects of key design parameters on overall performance remain insufficiently understood. This study employs Reynolds Averaged Navier–Stokes (RANS)-based Computational Fluid Dynamics (CFD) simulations to examine the effects of axial offset distance, index angle, and differential rotational speeds on the aerodynamic performance of an 18-inch two-blade coaxial co-rotating propeller. Maximum thrust is typically obtained at an index angle of around 60°, while the maximum Figure of Merit (FoM) is achieved at 90°. Increasing the offset distance from 0.05R to 0.20R improves the FoM by approximately 17.3% and reduces its sensitivity to index angle. When different rotating speeds are applied, assigning the higher rpm to the lower propeller increases thrust by 9.4% and the FoM by roughly 9.2%. These results offer practical guidelines for enhancing aerodynamic performance of a CCR propeller in unmanned aerial vehicle and urban air mobility platforms. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

20 pages, 2364 KB

Open AccessArticle

Convex Optimization for Spacecraft Attitude Alignment of Laser Link Acquisition Under Uncertainties

by Mengyi Guo, Peng Huang and Hongwei Yang

Aerospace 2025, 12(10), 939; https://doi.org/10.3390/aerospace12100939 - 17 Oct 2025

Viewed by 351

Abstract

This paper addresses the critical multiple-uncertainty challenge in laser link acquisition for space gravitational wave detection missions—a key bottleneck where spacecraft attitude alignment for laser link establishment is perturbed by inherent random disturbances in such missions, while also needing to balance ultra-high attitude [...] Read more.

This paper addresses the critical multiple-uncertainty challenge in laser link acquisition for space gravitational wave detection missions—a key bottleneck where spacecraft attitude alignment for laser link establishment is perturbed by inherent random disturbances in such missions, while also needing to balance ultra-high attitude precision, fuel efficiency, and compliance with engineering constraints. To tackle this, a convex optimization-based attitude control strategy integrating covariance control and free terminal time optimization is proposed. Specifically, a stochastic attitude dynamics model is first established to explicitly incorporate the aforementioned random disturbances. Subsequently, an objective function is designed to simultaneously minimize terminal state error and fuel consumption, with three key constraints (covariance constraints, pointing constraints, and torque saturation constraints) integrated into the convex optimization framework. Furthermore, to resolve non-convex terms in chance constraints, this study employs a hierarchical convexification method that combines Schur’s complementary theorem, second-order cone relaxation, and Taylor expansion techniques. This approach ensures lossless relaxation, renders the optimization problem computationally tractable without sacrificing solution accuracy, and overcomes the shortcomings of traditional convexification methods in handling chance constraints. Finally, numerical simulations demonstrate that the proposed method adheres to engineering constraints while maintaining spacecraft attitude errors below 1 μrad under environmental uncertainties. This study provides a convex optimization solution for laser link acquisition in space gravitational wave detection missions considering uncertainty conditions, and its framework can be extended to the optimal design of other stochastically uncertain systems. Full article

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

► Show Figures

Figure 1

20 pages, 6790 KB

Open AccessArticle

Finite-Time Attitude Control of Underactuated Spacecraft with a Hierarchical Sliding Mode Control Approach

by Jianli Wei, Wenhao Lyu, Bo Zhang and Hanqiao Huang

Aerospace 2025, 12(10), 938; https://doi.org/10.3390/aerospace12100938 - 17 Oct 2025

Viewed by 308

Abstract

In this paper, a finite-time three-axis stabilization controller for an underactuated rigid spacecraft is proposed based on well-designed hierarchical terminal sliding mode surfaces to handle the insufficiency of control effort and disturbances. Firstly, the attitude kinematic of an underactuated rigid spacecraft is parameterized [...] Read more.

In this paper, a finite-time three-axis stabilization controller for an underactuated rigid spacecraft is proposed based on well-designed hierarchical terminal sliding mode surfaces to handle the insufficiency of control effort and disturbances. Firstly, the attitude kinematic of an underactuated rigid spacecraft is parameterized by the w-z representation and the dynamic model with only two orthogonal torque inputs are presented. Secondly, based on the terminal sliding mode theory, a three-hierarchized sliding surface is established. A finite-time stable control law is derived by the Filippov equivalence theorem and the principle of sliding mode control. The finite-time stability is proved by the Lyapunov theory. Finally, the high performance of the proposed control approach is verified through numerical simulations and comparisons with state-of-the-art studies. Full article

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

► Show Figures

Figure 1

29 pages, 8801 KB

Open AccessArticle

Aerodynamic Performance Enhancement of Ram Air Turbine Blades with Different Tip Configurations

by Haoyu Li, Wei Zhong, Chunyu Ren, Jian Wang and Yilei Liu

Aerospace 2025, 12(10), 937; https://doi.org/10.3390/aerospace12100937 - 17 Oct 2025

Viewed by 367

Abstract

A ram air turbine serves as a critical emergency power system for aircraft. To mitigate aerodynamic losses from tip vortices, this study proposes three blade tip enhancement configurations: a tip plate, tip contraction, and winglet. Numerical results indicate that the tip plate slightly [...] Read more.

A ram air turbine serves as a critical emergency power system for aircraft. To mitigate aerodynamic losses from tip vortices, this study proposes three blade tip enhancement configurations: a tip plate, tip contraction, and winglet. Numerical results indicate that the tip plate slightly improves the power at low tip speed ratios (TSRs); however, at medium and high TSRs—typical of turbine operation—power gains turn negative, and thrust loads increase significantly, failing to balance the gain and load. In contrast, the tip contraction—applied to the outer 5% span—enhances the power output at medium to high TSRs, with a maximum power increase of 2.05%, and consistently reduces thrust loads across all TSRs. Its highest power–thrust net gain coefficient reaches 3.85%, indicating strong potential for optimizing power efficiency and load mitigation. The winglet achieves the greatest power enhancement, increasing the power across all TSRs, with a maximum power increase of 7.59%. However, its thrust load also increases accordingly, resulting in a power–thrust net gain coefficient lower than the tip contraction. Further optimization of the winglet parameters using an orthogonal experimental design revealed that the optimized winglet increased the power output by 8.69% compared to the baseline configuration, thereby increasing the maximum power–thrust net benefit coefficient from 1.72% before optimization to 3.95%. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

15 pages, 6164 KB

Open AccessArticle

Quaternary Correlation Prediction Compensation for Heading Commands in Virtual Autopilot

by Yutong Zhou and Shan Fu

Aerospace 2025, 12(10), 936; https://doi.org/10.3390/aerospace12100936 - 17 Oct 2025

Viewed by 293

Abstract

Virtual commands serve as the essential framework for establishing interaction between the virtual pilot and the MCP in autopilot scenarios. Conventional proportional-integral-derivative (PID) controllers are insufficient to ensure accurate flight trajectories due to system hysteresis. To overcome this limitation, a quaternary correlation prediction [...] Read more.

Virtual commands serve as the essential framework for establishing interaction between the virtual pilot and the MCP in autopilot scenarios. Conventional proportional-integral-derivative (PID) controllers are insufficient to ensure accurate flight trajectories due to system hysteresis. To overcome this limitation, a quaternary correlation prediction compensation PID (QCPC-PID) approach is introduced for computing virtual heading commands in autopilot tasks. The method integrates multi-feature statistics, entropy-based predictive compensation, and quaternary correlations. First, flight trajectory error statistics are dynamically calculated using signed error distances to assess deviation levels. Second, a predictive structure based on information entropy is applied to enhance PID compensation. Third, quaternary correlation dependence is established to generate virtual heading commands. The findings confirm the effectiveness of the method in improving flight convergence. The incorporation of predictive structures and quaternary correlations is critical for achieving predictive compensation during PID tuning, thereby reducing flight trajectory deviations. The quaternary correlation prediction compensation method ensures superior performance of PID control in modeling heading adjustment behavior under autopilot conditions. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

20 pages, 3633 KB

Open AccessArticle

A FMBD-DEM Coupled Modeling for Semi-Active Controlled Lunar Lander

by Hanyu Lin, Bo Lei and Weixing Yao

Aerospace 2025, 12(10), 935; https://doi.org/10.3390/aerospace12100935 - 16 Oct 2025

Viewed by 325

Abstract

This study examines the landing performance of a four-legged lunar lander equipped with magnetorheological dampers when landing on discrete lunar soil. To capture the complex interaction between the lander and the soil, a coupled dynamic model is developed that integrates flexible multibody dynamics [...] Read more.

This study examines the landing performance of a four-legged lunar lander equipped with magnetorheological dampers when landing on discrete lunar soil. To capture the complex interaction between the lander and the soil, a coupled dynamic model is developed that integrates flexible multibody dynamics (FMBD), granular material modeling, and a semi-active fuzzy control strategy. The flexible structures of the lander are described using the floating frame of reference, while the lunar soil behavior is simulated using the discrete element method (DEM). A fuzzy controller is designed to achieve the adaptive MR damping force under varying landing conditions. The FMBD and DEM modules are coupled through a serial staggered approach to ensure stable and accurate data exchange between the two systems. The proposed model is validated through a lander impact experiment, demonstrating good agreement with experimental results. Based on the validated model, the influence of discrete lunar regolith properties on MR damping performance is analyzed. The results show that the MR-based landing leg system can effectively absorb impact energy and adapt well to the uneven, granular lunar surface. Full article

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

► Show Figures

Figure 1

28 pages, 8901 KB

Open AccessArticle

Aerodynamic Performance of a Natural Laminar Flow Swept-Back Wing for Low-Speed UAVs Under Take Off/Landing Flight Conditions and Atmospheric Turbulence

by Nikolaos K. Lampropoulos, Ioannis E. Sarris, Spyridon Antoniou, Odysseas Ziogas, Pericles Panagiotou and Kyros Yakinthos

Aerospace 2025, 12(10), 934; https://doi.org/10.3390/aerospace12100934 - 16 Oct 2025

Viewed by 318

Abstract

The topic of the present study is the aerodynamic performance of a Natural Laminar Flow (NLF) wing for UAVs at low speed. The basis is a thoroughly tested NLF airfoil in the wind tunnel of NASA which is well-customized for light aircrafts. The [...] Read more.

The topic of the present study is the aerodynamic performance of a Natural Laminar Flow (NLF) wing for UAVs at low speed. The basis is a thoroughly tested NLF airfoil in the wind tunnel of NASA which is well-customized for light aircrafts. The aim of this work is the numerical verification that a typical wing design (tapered with moderate aspect ratio and wash-out), being constructed out of aerodynamically highly efficient NLF airfoils during cruise, can deliver high aerodynamic loading under minimal freestream turbulence as well as realistic atmospheric conditions of intermediate turbulence. Thus, high mission flexibility is achieved, e.g., short take off/landing capabilities on the deck of ship where moderate air turbulence is prevalent. Special attention is paid to the effect of the Wing Tip Vortex (WTV) under minimal inflow turbulence regimes. The flight conditions are take off or landing at moderate Reynolds number, i.e., one to two millions. The numerical simulation is based on an open source CFD code and parallel processing on a High Performance Computing (HPC) platform. The aim is the identification of both mean flow and turbulent structures around the wing and subsequently the formation of the wing tip vortex. Due to the purely three-dimensional character of the flow, the turbulence is resolved with advanced modeling, i.e., the Improved Delayed Detached Eddy Simulation (IDDES) which is well-customized to switch modes between Delayed Detached Eddy Simulation (DDES) and Wall-Modeled Large Eddy Simulation (WMLES), thus increasing the accuracy in the shear layer regions, the tip vortex and the wake, while at the same time keeping the computational cost at reasonable levels. IDDES also has the capability to resolve the transition of the boundary layer from laminar to turbulent, at least with engineering accuracy; thus, it serves as a high-fidelity turbulence model in this work. The study comprises an initial benchmarking of the code against wind tunnel measurements of the airfoil and verifies the adequacy of mesh density that is used for the simulation around the wing. Subsequently, the wing is positioned at near-stall conditions so that the aerodynamic loading, the kinematics of the flow and the turbulence regime in the wing vicinity, the wake and far downstream can be estimated. In terms of the kinematics of the WTV, a thorough examination is attempted which comprises its inception, i.e., the detachment of the boundary layer on the cut-off wing tip, the roll-up of the shear layer to form the wake and the motion of the wake downstream. Moreover, the effect of inflow turbulence of moderate intensity is investigated that verifies the bibliography with regard to the performance degradation of static airfoils in a turbulent atmospheric regime. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

21 pages, 3803 KB

Open AccessArticle

Optimization of a Walker Constellation Using an RBF Surrogate Model for Space Target Awareness

by You Fu, Zhaojing Xu, Youchen Fan, Liu Yi, Zhao Ma, Yuhai Li and Shengliang Fang

Aerospace 2025, 12(10), 933; https://doi.org/10.3390/aerospace12100933 - 16 Oct 2025

Viewed by 343

Abstract

Designing Low Earth Orbit (LEO) constellations for the continuous, collaborative observation of space objects in MEO/GEO is a complex optimization task, frequently limited by prohibitive computational costs. This study introduces an efficient surrogate-based framework to overcome this challenge. Our approach integrates Optimized Latin [...] Read more.

Designing Low Earth Orbit (LEO) constellations for the continuous, collaborative observation of space objects in MEO/GEO is a complex optimization task, frequently limited by prohibitive computational costs. This study introduces an efficient surrogate-based framework to overcome this challenge. Our approach integrates Optimized Latin Hypercube Sampling (OLHS) with a Radial Basis Function (RBF) model to minimize the required number of satellites. In a comprehensive case study targeting 18 diverse space objects—including communication satellites in GEO (e.g., EUTELSAT, ANIK) and navigation satellites in MEO/IGSO from GPS, Galileo, and BeiDou constellations—the method proved highly effective and scalable. It successfully designed a 208-satellite Walker constellation that provides 100% continuous coverage over a 36-h period. Furthermore, the design ensures that each target is simultaneously observed by at least three satellites at all times. A key finding is the method’s remarkable efficiency and scalability: the optimal solution for this larger problem was found using only 46 high-fidelity function evaluations, maintaining a computational time that was 5–8 times faster than traditional global optimization algorithms. This research demonstrates that surrogate-assisted optimization can drastically lower the computational barrier in constellation design, offering a powerful tool for building cost-effective and robust Space Situational Awareness (SSA) systems. Full article

(This article belongs to the Special Issue Advances in Space Surveillance and Tracking)

► Show Figures

Figure 1

26 pages, 2425 KB

Open AccessArticle

The Operational Safety Evaluation of UAVs Based on Improved Support Vector Machines

by Yulin Zhou and Shuguang Liu

Aerospace 2025, 12(10), 932; https://doi.org/10.3390/aerospace12100932 - 16 Oct 2025

Viewed by 290

Abstract

In response to the challenge of dynamic adaptability in operational safety assessment for UAVs operating in complex operational environments, this study proposes a novel operational safety assessment method based on an Improved Support Vector Machine. An operational safety assessment index system encompassing four [...] Read more.

In response to the challenge of dynamic adaptability in operational safety assessment for UAVs operating in complex operational environments, this study proposes a novel operational safety assessment method based on an Improved Support Vector Machine. An operational safety assessment index system encompassing four dimensions—operator, UAV platform, flight environment, flight mission—is constructed to provide a comprehensive foundation for evaluation. The method introduces a dynamic weighted information entropy mechanism based on a sliding window, overcoming the static features and delayed response of traditional SVM methods. Additionally, it integrates Gaussian and polynomial kernel functions to significantly enhance the generalization capability and classification accuracy of the SVM model in complex operational environments. Experimental results show that the proposed model demonstrates superior performance on test samples, effectively improving the accuracy of operational safety assessment for the Reconnaissance–Strike UAV in complex operational environments, and offering a novel methodology for UAV safety assessment. Full article

(This article belongs to the Special Issue Airworthiness, Safety and Reliability of Aircraft)

► Show Figures

Figure 1

29 pages, 6643 KB

Open AccessArticle

Experimental and Machine Learning-Based Investigation on Forced Convection Heat Transfer Characteristics of Al₂O₃–Water Nanofluid in a Rotating Hypergravity Condition

by Zufen Luo, Gen Li, Jianxun Xie, Xiaojie Zhang, Yunbo Wang and Xiande Fang

Aerospace 2025, 12(10), 931; https://doi.org/10.3390/aerospace12100931 - 15 Oct 2025

Viewed by 321

Abstract

This study experimentally investigates single-phase forced convection heat transfer and flow characteristics of Al₂O₃-water nanofluids under rotating hypergravity conditions ranging from 1 g to 5.1 g. While nanofluids offer enhanced thermal properties for advanced cooling applications in aerospace and [...] Read more.

This study experimentally investigates single-phase forced convection heat transfer and flow characteristics of Al₂O₃-water nanofluids under rotating hypergravity conditions ranging from 1 g to 5.1 g. While nanofluids offer enhanced thermal properties for advanced cooling applications in aerospace and rotating machinery, their performance under hypergravity remains poorly understood. Experiments employed a custom centrifugal test rig with a horizontal test section (D = 2 mm, L = 200 mm) operating at constant heat flux. Alumina nanoparticles (20–30 nm) were dispersed in deionized water at mass fractions of 0.02–0.5 wt%, with stability validated through transmittance measurements over 72 h. Heat transfer coefficients (HTC), Nusselt numbers (Nu), friction factors (f), and pressure drops were measured across Reynolds numbers from 500 to 30,000. Results demonstrate that hypergravity significantly enhances heat transfer, with HTC increasing by up to 40% at 5.1 g compared to 1 g, most pronounced at the transition from 1 g to 1.41 g. This enhancement is attributed to intensified buoyancy-driven secondary flows quantified by increased Grashof numbers and modified particle distribution. Friction factors increased moderately (15–25%) due to Coriolis effects and enhanced viscous dissipation. Optimal performance occurred at 0.5 wt% concentration, effectively balancing thermal enhancement against pumping penalties. Random forest (RF) and eXtreme gradient boosting (XGBoost) achieved R² = 0.9486 and 0.9625 in predicting HTC, respectively, outperforming traditional correlations (Gnielinski: R² = 0.9124). These findings provide crucial design guidelines for thermal management systems in hypergravity environments, particularly for aerospace propulsion and centrifugal heat exchangers, where gravitational variations significantly impact cooling performance. Full article

(This article belongs to the Special Issue Advanced Thermal Management in Aerospace Systems)

► Show Figures

Figure 1

35 pages, 2172 KB

Open AccessArticle

Aircraft Noise Assessment Using Noise Points: Conception and Verification

by Jason Blinstrub and Rainer Schmid

Aerospace 2025, 12(10), 930; https://doi.org/10.3390/aerospace12100930 - 15 Oct 2025

Viewed by 288

Abstract

The increase in global air traffic volumes has significant economic and ecological impacts. A key factor in this context is the development of the noise situation around airports. However, assessing the development of the noise situation at multiple airports simultaneously and in detail [...] Read more.

The increase in global air traffic volumes has significant economic and ecological impacts. A key factor in this context is the development of the noise situation around airports. However, assessing the development of the noise situation at multiple airports simultaneously and in detail requires comprehensive calculations. Therefore, there is a strong need for a simple method to evaluate how the growth of air traffic affects the noise impact around airports, especially under considerations of different what-if scenarios. This can be achieved by assigning a noise-equivalent value to each aircraft that represents its noise impact. These noise points indicate how many movements of a reference aircraft would be required to produce approximately the same noise impact as one movement of the aircraft under consideration. The concept allows for an easy and quick assessment of aircraft noise by summing such noise points, because, as shown in this study, the noise point sum can directly be related to a change in noise levels and contour area. This article presents a promising method for determining noise points and applies it to aircraft groups from a recently proposed database of the German aircraft noise calculation method AzB. The noise point concept is verified at various airports, demonstrating its effectiveness in representing noise situations and developments. The differences of analyzed contour areas obtained via noise calculations and via the noise point concept remain below 3.6% over a generic 30-year forecast. Full article

(This article belongs to the Special Issue Aircraft Noise Mitigation—Concepts, Assessment, and Implementation)

► Show Figures

Figure 1

21 pages, 4389 KB

Open AccessArticle

Integrated Hardware and Algorithmic Decoupling of Light-Noise-Attenuation Coupled Errors: A Path to 50 Pa Precision in Micro-Pressure PSP Measurements

by Kun Cao, Qiang Liu, Chunhua Wei, Yunmao Bai and Lei Liang

Aerospace 2025, 12(10), 929; https://doi.org/10.3390/aerospace12100929 - 15 Oct 2025

Viewed by 231

Abstract

In low-speed flow (Ma < 0.3), pressure-sensitive paint (PSP) technology encounters a significant bottleneck in micro-pressure measurements due to the coupled interference of light source instability, camera noise, and paint photodegradation. This study introduces a hardware–algorithm collaborative decoupling framework to address the light [...] Read more.

In low-speed flow (Ma < 0.3), pressure-sensitive paint (PSP) technology encounters a significant bottleneck in micro-pressure measurements due to the coupled interference of light source instability, camera noise, and paint photodegradation. This study introduces a hardware–algorithm collaborative decoupling framework to address the light noise–degradation coupling issue. The framework integrates real-time light source fluctuation monitoring using a photomultiplier tube (PMT), a combined histogram–wavelet denoising algorithm, and a dynamic photodegradation compensation model. A high-precision static calibration system with a pressure control error of 3.4 Pa was constructed to validate the proposed framework. The experimental results indicate that light source fluctuations contribute an error of 42.61 Pa, accounting for 33% of the total error. After collaborative optimization, the PSP measurement error was reduced to below 50 Pa, representing a 50% improvement compared to previous results (100 Pa). This study provides reliable technical support for micro-pressure measurement applications, such as low-speed wind tunnel testing of aerospace vehicles and microfluidic diagnostics. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

25 pages, 5853 KB

Open AccessArticle

GPS-Based Relative Navigation for Laser Crosslink Alignment in the VISION CubeSat Mission

by Yeji Kim, Pureum Kim, Han-Gyeol Ryu, Youngho Eun and Sang-Young Park

Aerospace 2025, 12(10), 928; https://doi.org/10.3390/aerospace12100928 - 15 Oct 2025

Viewed by 419

Abstract

As the demand for high-speed space-borne data transmission grows, CubeSat-based Free-Space Optical Communication (FSOC) offers a viable solution for achieving a Gbps-speed optical intersatellite link on low-cost platforms. The Very-High-Speed Intersatellite Optical Link System Using an Infrared Optical Terminal and Nanosatellite (VISION) mission [...] Read more.

As the demand for high-speed space-borne data transmission grows, CubeSat-based Free-Space Optical Communication (FSOC) offers a viable solution for achieving a Gbps-speed optical intersatellite link on low-cost platforms. The Very-High-Speed Intersatellite Optical Link System Using an Infrared Optical Terminal and Nanosatellite (VISION) mission aims to establish these high-speed laser crosslinks, which require a precise pointing and relative positioning system at relative distances up to 1000 km. A real-time relative navigation system was developed based on dual-frequency GPS pseudorange and carrier-phase measurements, incorporating an adaptive Kalman filter which uses innovation-based covariance matching to dynamically adjust process noise covariance. Hardware-integrated testing with GPS signal generators and onboard receivers validated its performance under realistic conditions, consistently achieving sub-meter positioning accuracy across baselines up to 1000 km. An integrated orbit–attitude simulation further evaluated the feasibility of the Pointing, Acquisition, and Tracking (PAT) system by combining real-time relative navigation outputs with an attitude control system. Simulation results showed that the PAT system maintained a total pointing error of 274.3 μrad, sufficient to sustain stable high-speed optical links. This study demonstrates that the VISION relative navigation and pointing systems, integrated within the PAT framework, enable precise real-time optical intersatellite communication using CubeSats. Full article

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

► Show Figures

Figure 1

21 pages, 5782 KB

Open AccessArticle

Sand Ingestion Behavior of Helicopter Engines During Hover in Ground Effect

by Qiang Li, Linghua Dong, Changxin Song and Weidong Yang

Aerospace 2025, 12(10), 927; https://doi.org/10.3390/aerospace12100927 - 15 Oct 2025

Viewed by 350

Abstract

Sand ingestion exerts significant effects on the performance of helicopter engines, and it is imperative to investigate this phenomenon. In this study, the mechanisms of engine sand ingestion during helicopter hover in ground effect are analyzed. Firstly, a coupled computational model is established [...] Read more.

Sand ingestion exerts significant effects on the performance of helicopter engines, and it is imperative to investigate this phenomenon. In this study, the mechanisms of engine sand ingestion during helicopter hover in ground effect are analyzed. Firstly, a coupled computational model is established based on computational fluid dynamics (CFD) and the discrete element method (DEM). The aerodynamic calculation accuracy of this model is validated by comparing the pressure coefficient and tip vortex with wind tunnel test results. Subsequently, based on this method, a systematic simulation is carried out to investigate the flow field dynamics and sand cloud distribution for the helicopter at different ground-effect heights (GEHs, h). Simulation results indicate that helicopter engines can potentially directly ingest sand particles from the ground at low GEHs. When h > 2R (where R is the rotor radius), the height of sand clouds is insufficient for helicopter engines to ingest sand. Finally, guided by the simulation conclusions, a rotor test bench is designed to conduct research on sand ingestion by helicopter engines. It aims to further study how GEH and engine intake flowrate (Q) affect sand ingestion amount and distribution across the inlet cross-section. Experimental results demonstrate that the sand ingestion amount exhibits a nonlinear decreasing trend with the increasing GEH and a positive correlation with Q. At h = 0.5R, the engine directly ingests sand particles from the ground sand field, leading to a significant increase in sand ingestion. The increase reaches 11 times that at other GEHs. For the right-handed rotor in this study, the sand ingestion of the right engine is significantly higher than that of the left engine. Furthermore, for the cross-sectional position of the engine inlet in this study, over 60% of sand particles are ingested through the upper region. The research can provide scientific guidance for the design of particle separators and is of great significance for helicopter engine sand prevention. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (4th Edition))

► Show Figures

Figure 1

20 pages, 4870 KB

Open AccessArticle

Nose Landing Gear Shimmy Analysis with Variable System Stiffness Under Time-Varying Load

by Yiyao Jiang, Jiyong Sun, Sheng Zhong and Bingyan Jiang

Aerospace 2025, 12(10), 926; https://doi.org/10.3390/aerospace12100926 - 14 Oct 2025

Viewed by 282

Abstract

Vertical load fluctuations alter nose landing gear (NLG) system stiffness and complicate shimmy dynamics. Based on the full-scale NLG static stiffness test data, the relationship between shock absorber stroke and system stiffness was fitted, and a nonlinear shimmy model considering time-varying loads was [...] Read more.

Vertical load fluctuations alter nose landing gear (NLG) system stiffness and complicate shimmy dynamics. Based on the full-scale NLG static stiffness test data, the relationship between shock absorber stroke and system stiffness was fitted, and a nonlinear shimmy model considering time-varying loads was established. The numerical solution was achieved using the established Simscape model. The research results show that, under constant load conditions, considering the nonlinear growth characteristic of NLG system stiffness with shock absorber stroke, the lateral shimmy amplitude of the NLG is significantly reduced, while the rotational shimmy amplitude increases slightly; among these, lateral stiffness plays a dominant role in influencing shimmy stability. In addition, time-varying loads aggravate shimmy through two paths: first, the fluctuation of load amplitude directly changes the force state; second, vertical movement causes changes in the shock absorber stroke, which in turn leads to dynamic adjustment of system stiffness. This is of great help in guiding the stiffness design of the NLG system and accurately evaluating shimmy stability. Full article

(This article belongs to the Special Issue Advances in Landing Systems Engineering)

► Show Figures

Figure 1

21 pages, 1922 KB

Open AccessArticle

Real-Time Detection of LEO Satellite Orbit Maneuvers Based on Geometric Distance Difference

by Aoran Peng, Bobin Cui, Guanwen Huang, Le Wang, Haonan She, Dandan Song and Shi Du

Aerospace 2025, 12(10), 925; https://doi.org/10.3390/aerospace12100925 - 14 Oct 2025

Viewed by 444

Abstract

Low Earth orbit (LEO) satellites, characterized by low altitudes, high velocities, and strong ground signal reception, have become an essential and dynamic component of modern global navigation satellite systems (GNSS). However, orbit decay induced by atmospheric drag poses persistent challenges to maintaining stable [...] Read more.

Low Earth orbit (LEO) satellites, characterized by low altitudes, high velocities, and strong ground signal reception, have become an essential and dynamic component of modern global navigation satellite systems (GNSS). However, orbit decay induced by atmospheric drag poses persistent challenges to maintaining stable trajectories. Frequent orbit maneuvers, though necessary to sustain nominal orbits, introduce significant difficulties for precise orbit determination (POD) and navigation augmentation, especially under complex operational conditions. Unlike most existing methods that rely on Two-Line Element (TLE) data—often affected by noise and limited accuracy—this study directly utilizes onboard GNSS observations in combination with real-time precise ephemerides. A novel time-series indicator is proposed, defined as the geometric root-mean-square (RMS) distance between reduced-dynamic and kinematic orbit solutions, which is highly responsive to orbit disturbances. To further enhance robustness, a sliding window-based adaptive thresholding mechanism is developed to dynamically adjust detection thresholds, maintaining sensitivity to maneuvers while suppressing false alarms. The proposed method was validated using eight representative maneuver events from the GRACE-FO satellites (May 2018–June 2022), successfully detecting seven of them. One extremely short-duration maneuver was missed due to the limited number of usable GNSS observations after quality-control filtering. To examine altitude-related applicability, two Sentinel-3A maneuvers were also analyzed, both successfully detected, confirming the method’s effectiveness at higher LEO altitudes. Since the thrust magnitudes and durations of the Sentinel-3A maneuvers are not publicly available, these cases primarily serve to verify applicability rather than to quantify sensitivity. Experimental results show that for GRACE-FO maneuvers, the proposed method achieves near-real-time responsiveness under long-duration, high-thrust conditions, with an average detection delay below 90 s. For Sentinel-3A, detections occurred approximately 7 s earlier than the reported maneuver epochs, a discrepancy attributed to the 30 s observation sampling interval rather than methodological bias. Comparative analysis with representative existing methods, presented in the discussion section, further demonstrates the advantages of the proposed approach in terms of sensitivity, timeliness, and adaptability. Overall, this study presents a practical, efficient, and scalable solution for real-time maneuver detection in LEO satellite missions, contributing to improved GNSS augmentation, space situational awareness, and autonomous orbit control. Full article

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

► Show Figures

Figure 1

28 pages, 7870 KB

Open AccessArticle

Effect of Different Configurations on Operating Characteristics of Rear Variable Area Bypass Injector for Adaptive Cycle Engine

by Weitao Liu, Wangzhi Zou, Baotong Wang, Weihan Kong, Jun Lai, Lei Jin and Xinqian Zheng

Aerospace 2025, 12(10), 924; https://doi.org/10.3390/aerospace12100924 - 14 Oct 2025

Viewed by 302

Abstract

The adaptive cycle engine (ACE) can modulate thermal cycle characteristics by adjusting variable geometry components, enabling rational distribution of bypass flow rates. As a key component of the ACE, the rear variable area bypass injector (RVABI) significantly influences the engine bypass ratio and [...] Read more.

The adaptive cycle engine (ACE) can modulate thermal cycle characteristics by adjusting variable geometry components, enabling rational distribution of bypass flow rates. As a key component of the ACE, the rear variable area bypass injector (RVABI) significantly influences the engine bypass ratio and consequently alters engine performance. RVABIs are typically categorized into three configurations based on their design: Translation Type, Rotary Type, and Hole Type. Previous studies have not fully elucidated the overall operating characteristics, internal flow mechanisms, and applicable scenarios of these different RVABI configurations. To address this problem, this paper first introduces and validates a three-dimensional (3D) simulation methodology for RVABIs. Subsequently, criteria for reasonably evaluating the operating characteristics of different RVABI configurations are defined. Following this, the differences in operating characteristics and internal flow mechanisms among the three RVABI configurations are systematically compared. Finally, the application scenarios for each configuration are identified. This work provides valuable insights to guide the configuration selection and parameter design of RVABIs in practical engineering applications. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

22 pages, 2523 KB

Open AccessArticle

Network Modeling and Risk Assessment of Multi-Stakeholder-Coupled Unsafe Events in the Airspace System

by Yiming Dai, Honghai Zhang, Zongbei Shi and Yike Li

Aerospace 2025, 12(10), 923; https://doi.org/10.3390/aerospace12100923 - 13 Oct 2025

Viewed by 319

Abstract

Unsafe events in civil aviation increasingly arise from multi-stakeholder interactions, motivating system-level methods to quantify event risk and coupling. This study analyzes 1551 airspace unsafe-operation reports and models each report as a node with four attributes; edges capture co-occurrence based on cosine similarity, [...] Read more.

Unsafe events in civil aviation increasingly arise from multi-stakeholder interactions, motivating system-level methods to quantify event risk and coupling. This study analyzes 1551 airspace unsafe-operation reports and models each report as a node with four attributes; edges capture co-occurrence based on cosine similarity, and risk is scored via an entropy-weight TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) scheme. Risk scores range 0–0.858, with 7% of nodes above 0.8 forming a high-risk tail; entropy weights emphasize recovery time and hazard level. Community detection yields three modules aligned with Controller, Resource, and User stakeholders; key nodes occur predominantly in Controller and Resource groups, with Controller nodes showing the highest betweenness. Coupling analysis using an N–K perspective and edge-based inter-stakeholder strength further highlights controller-centric links. The proposed framework objectively ranks node risk, reveals cross-stakeholder coupling patterns, and isolates structurally influential events, providing evidence to prioritize monitoring and mitigation in airspace safety management. Full article

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

► Show Figures

Figure 1

23 pages, 2839 KB

Open AccessArticle

Risk Prediction of Shipborne Aircraft Landing Based on Deep Learning

by Hao Nian, Xiuquan Deng, Zhipeng Bai and Xingjie Wu

Aerospace 2025, 12(10), 922; https://doi.org/10.3390/aerospace12100922 - 13 Oct 2025

Viewed by 255

Abstract

Shipborne fighters play a critical role in far-sea operations. However, their landing process on aircraft carrier decks involves significant risks, where accidents can lead to substantial losses. Timely and accurate risk prediction is, therefore, essential for improving flight training efficiency and enhancing the [...] Read more.

Shipborne fighters play a critical role in far-sea operations. However, their landing process on aircraft carrier decks involves significant risks, where accidents can lead to substantial losses. Timely and accurate risk prediction is, therefore, essential for improving flight training efficiency and enhancing the combat capability of naval aviation forces. Machine-learning algorithms have been explored for predicting landing risks in land-based aircraft. However, owing to the challenges in acquiring relevant data, the application of such methods to shipborne aircraft remains limited. To address this gap, the present study proposes a deep learning-based method for predicting landing risks of shipborne aircraft. A dataset was constructed using simulated ship movements recorded during the sliding phase along with relevant flight parameters. Model training and prediction were conducted using up to ten different input combinations with artificial neural networks, long short-term memory, and transformer neural networks. Experimental results demonstrate that all three models can effectively predict landing parameters, with the lowest average test error reaching 3.5620. The study offers a comprehensive comparison of traditional machine learning and deep learning methods, providing practical insights into input variable selection and model performance evaluation. Although deep learning models, particularly the Transformer, achieved the highest accuracy, in practical applications, the support of hardware performance still needs to be fully considered. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

65 pages, 10545 KB

Open AccessArticle

Stability of a Single-Channel Rolling Aerospace Vehicle with Semi-Automatic Command to Line of Sight

by Teodor-Viorel Chelaru, Cristian Emil Constantinescu, Valentin Pană and Costin Ene

Aerospace 2025, 12(10), 921; https://doi.org/10.3390/aerospace12100921 - 13 Oct 2025

Viewed by 367

Abstract

This paper presents a stability analysis of single-channel, slow-rolling, Semi-Automatic Command to Line of Sight (SACLOS) missiles using a comparison of the Routh–Hurwitz and the Frank–Wall stability criteria and a nonlinear analysis. Beginning with a six-degree-of-freedom (6-DOF) model in the Resal frame, a [...] Read more.

This paper presents a stability analysis of single-channel, slow-rolling, Semi-Automatic Command to Line of Sight (SACLOS) missiles using a comparison of the Routh–Hurwitz and the Frank–Wall stability criteria and a nonlinear analysis. Beginning with a six-degree-of-freedom (6-DOF) model in the Resal frame, a linearized model for the commanded motion is developed. This linearized model, which features complex coefficients due to the coupling of longitudinal channels in rolling missiles, is used to define the structural scheme of the commanded object and its flight quality parameters. The guidance kinematic relations, guidance device equations, and actuator relations, incorporating a switching function specific to slow-rolling, single-channel missiles, are also defined and linearized within the Resal frame to construct a comprehensive structural diagram of the SACLOS missile. From this, the characteristic polynomial with complex coefficients is derived and analyzed by comparing the Routh–Hurwitz and the Frank–Wall stability criteria. This analysis determines a stability domain for the guidance gain and establishes a minimum limit for the guidance time. The stability domain defined through the linear model is then validated using a nonlinear model in the body frame. Full article

► Show Figures

Figure 1

20 pages, 49845 KB

Open AccessArticle

DDF-YOLO: A Small Target Detection Model Using Multi-Scale Dynamic Feature Fusion for UAV Aerial Photography

by Ziang Ma, Chao Wang, Chuanzhi Chen, Jinbao Chen and Guang Zheng

Aerospace 2025, 12(10), 920; https://doi.org/10.3390/aerospace12100920 - 13 Oct 2025

Viewed by 702

Abstract

Unmanned aerial vehicle (UAV)-based object detection shows promising potential in intelligent transportation and disaster response. However, detecting small targets remains challenging due to inherent limitations (long-distance and low-resolution imaging) and environmental interference (complex backgrounds and occlusions). To address these issues, this paper proposes [...] Read more.

Unmanned aerial vehicle (UAV)-based object detection shows promising potential in intelligent transportation and disaster response. However, detecting small targets remains challenging due to inherent limitations (long-distance and low-resolution imaging) and environmental interference (complex backgrounds and occlusions). To address these issues, this paper proposes an enhanced small target detection model, DDF-YOLO, which achieves higher detection performance. First, a dynamic feature extraction module (C2f-DCNv4) employs deformable convolutions to effectively capture features from irregularly shaped objects. In addition, a dynamic upsampling module (DySample) optimizes multi-scale feature fusion by combining shallow spatial details with deep semantic features, preserving critical low-level information while enhancing generalization across scales. Finally, to balance rapid convergence with precise localization, an adaptive Focaler-ECIoU loss function dynamically adjusts training weights based on sample quality during bounding box regression. Extensive experiments on VisDrone2019 and UAVDT benchmarks demonstrate DDF-YOLO’s superiority. Compared to YOLOv8n, our model achieves gains of 8.6% and 4.8% in mAP50, along with improvements of 5.0% and 3.3% in mAP50-95, respectively. Furthermore, it exhibits superior efficiency, requiring only 7.3 GFLOPs and attaining an inference speed of 179 FPS. These results validate the model’s robustness for UAV-based detection, particularly in small-object scenarios. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

16 pages, 3293 KB

Open AccessArticle

Numerical Investigation of Pyrolytic Coking and Its Effects on Heat Transfer of RP-3

by Xizhuo Hu, Peng Zhang, Jianqin Zhu, Zeyuan Cheng and Shuang Sun

Aerospace 2025, 12(10), 919; https://doi.org/10.3390/aerospace12100919 - 12 Oct 2025

Viewed by 323

Abstract

Hydrocarbon fuels are extensively employed as coolants in the regenerative cooling systems of scramjet engines. However, the pyrolytic coking of hydrocarbon fuels at high temperatures introduces complex adverse effects on the flow and cooling processes. In this study, a numerical model was developed [...] Read more.

Hydrocarbon fuels are extensively employed as coolants in the regenerative cooling systems of scramjet engines. However, the pyrolytic coking of hydrocarbon fuels at high temperatures introduces complex adverse effects on the flow and cooling processes. In this study, a numerical model was developed to investigate the coupling processes of fluid flow, heat transfer, pyrolysis and pyrolytic coking in the heated tube, under both a constant outer wall heat flux of 1.8 MW/m² and a constant outer wall temperature of 1150 K. The multi-step pyrolytic reaction mechanism and the kinetic coking model were applied to simulate the pyrolytic coking processes of RP-3. The results reveal that the amounts of catalytic coking and lateral growth exhibit significant differences in magnitude, as well as in their spatial and temporal variations. Under a constant outer wall heat flux, coking evidently increases the outer wall temperature and thermal resistance, leading to a narrowed flow passage and a reduction in the residence time and RP-3 conversion rate. Under a constant outer wall temperature, coking decreases the heat absorption flux, resulting in a lower fluid temperature, which primarily affects the efficiency of the endothermic pyrolytic reaction. The results obtained in this research can provide practical insights for the development of regenerative cooling technology. Full article

(This article belongs to the Section Aeronautics)

► Show Figures

Figure 1

25 pages, 20024 KB

Open AccessArticle

Divergence Evaluation Criteria for Lunar Departure Trajectories Under Bi-Circular Restricted Four-Body Problem

by Kohei Takeda and Toshinori Kuwahara

Aerospace 2025, 12(10), 918; https://doi.org/10.3390/aerospace12100918 - 12 Oct 2025

Viewed by 276

Abstract

This study focuses on the nonlinear departure dynamics of spacecraft from the Near Rectilinear Halo Orbit (NRHO) to the outer regions of Selenocentric Space. By carefully selecting the combination of orbital parameters and the order of the evaluation process, it becomes possible to [...] Read more.

This study focuses on the nonlinear departure dynamics of spacecraft from the Near Rectilinear Halo Orbit (NRHO) to the outer regions of Selenocentric Space. By carefully selecting the combination of orbital parameters and the order of the evaluation process, it becomes possible to precisely identify the divergence moment and to reliably classify the subsequent dynamical space. An empirical divergence detection algorithm is proposed by integrating multiple parameters derived from multi-body dynamical models, including gravitational potentials and related quantities. In an applied analysis using this method, it is found that the majority of perturbed trajectories diverge into the outer Earth–Moon Vicinity, while transfers into the inner Earth–Moon Vicinity are relatively limited. Furthermore, transfers to Heliocentric Space are found to be dependent not on the magnitude of the initial perturbation but on the geometric configuration of the Sun, Earth, and Moon during the transfer phase. The investigation of the Sun’s initial phase reveals a rotationally symmetric structure in the perturbation distribution within the Sun–Earth–Moon system, as well as localized conditions under which the destination space varies significantly depending on the initial state. Identifying the divergence moment allows for comparative evaluation of the spacecraft’s nonlinear dynamical state, providing valuable insights for the development of safe and efficient transfer strategies from selenocentric orbits, including those originating from the NRHO. Full article

► Show Figures

Figure 1

34 pages, 2661 KB

Open AccessArticle

Electric Aircraft Airport Electric Utility Sizing Study Based on Multi-Layer Optimization Models

by Yu Wang, Xisheng Li, Jiannan Chi, Cong Zhang and Jiahui Liu

Aerospace 2025, 12(10), 917; https://doi.org/10.3390/aerospace12100917 - 11 Oct 2025

Viewed by 464

Abstract

As the potential of e-aircraft in short-range routes becomes more prominent, the question of how to rationally plan airport electric infrastructure and efficiently produce it has become a key issue in the aviation industry’s efforts to move towards electrification. In this paper, we [...] Read more.

As the potential of e-aircraft in short-range routes becomes more prominent, the question of how to rationally plan airport electric infrastructure and efficiently produce it has become a key issue in the aviation industry’s efforts to move towards electrification. In this paper, we propose and construct a three-layer optimization model for determining the size of airport electric infrastructure, which is solved collaboratively at the three levels of strategic, tactical, and operational layers, in order to construct an optimization algorithm to minimize the construction and operation costs of electric infrastructure, and at the same time to ensure that flights are not delayed by the influence of electric power supply. Specifically, Stage-1 considers infrastructure sizes; Stage-2 assigns a binary charge–swap decision per turnaround under no-delay policy; Stage-3 schedules power under time-of-use tariffs and outputs a feasible day plan and daily cost. In order to verify the effectiveness of this paper’s algorithm, this paper conducts case studies and algorithm validation on actual flight data. The results show that the proposed model can significantly reduce the overall airport operating costs while ensuring normal flight operations. Full article

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

► Show Figures

Figure 1

19 pages, 6415 KB

Open AccessArticle

Combustion and Heat-Transfer Characteristics of a Micro Swirl Combustor-Powered Thermoelectric Generator: A Numerical Study

by Kenan Huang, Jiahao Zhang, Guoneng Li, Yiyuan Zhu, Chao Ye and Ke Li

Aerospace 2025, 12(10), 916; https://doi.org/10.3390/aerospace12100916 - 11 Oct 2025

Viewed by 387

Abstract

Micro-combustion-powered thermoelectric generators (μ-CPTEGs) combine the high energy density of hydrocarbons with solid-state conversion, offering compact and refuelable power for long-endurance electronics. Such characteristics make μ-CPTEGs particularly promising for aerospace systems, where conventional batteries face serious limitations. Their achievable performance [...] Read more.

Micro-combustion-powered thermoelectric generators (μ-CPTEGs) combine the high energy density of hydrocarbons with solid-state conversion, offering compact and refuelable power for long-endurance electronics. Such characteristics make μ-CPTEGs particularly promising for aerospace systems, where conventional batteries face serious limitations. Their achievable performance hinges on how a swirl-stabilized flame transfers heat into the hot ends of thermoelectric modules. This study uses a conjugate CFD framework coupled with a lumped parameter model to examine how input power and equivalence ratio shape the flame/flow structure, temperature fields, and hot-end heating in a swirl combustor-powered TEG. Three-dimensional numerical simulations were performed for the swirl combustor-powered TEG, varying the input power from 1269 to 1854 W and the equivalence ratio from φ = 0.6 to 1.1. Results indicate that the combustor exit forms a robust “annular jet with central recirculation” structure that organizes a V-shaped region of high modeled heat release responsible for flame stabilization and preheating. At φ = 1.0, increasing Q_in from 1269 to 1854 W strengthens the V-shaped hot band and warms the wall-attached recirculation. Heating penetrates deeper into the finned cavity, and the central-plane peak temperature rises from 2281 to 2339 K (≈2.5%). Consistent with these field changes, the lower TEM pair near the outlet heats more strongly than the upper module (517 K to 629 K vs. 451 K to 543 K); the inter-row gap widens from 66 K to 86 K, and the incremental temperature gains taper at the highest power, while the axial organization of the field remains essentially unchanged. At fixed Q_in = 1854 W, raising φ from 0.6 to 1.0 compacts and retracts the reaction band toward the exit and weakens axial penetration; the main-zone temperature increases up to φ = 0.9 and then declines for richer mixtures (peak 2482 K at φ = 0.9 to 2289 K at φ = 1.1), cooling the fin section due to reduced transport, thereby identifying φ = 0.9 as the operating point that best balances axial penetration against dilution/convective-cooling losses and maximizes the TEM hot-end temperature at the fixed power. Full article

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

► Show Figures

Figure 1

Journal Menu

Journal Browser

Aerospace, Volume 12, Issue 10 (October 2025) – 90 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI