Aerospace

21 pages, 8417 KB

Open AccessArticle

Experimental Investigation on Melting Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry Under Stirring

by Zhaohao Xu, Minjie Wu and Yu Xu

Aerospace 2025, 12(10), 868; https://doi.org/10.3390/aerospace12100868 (registering DOI) - 26 Sep 2025

Abstract

As avionics advance, heat dissipation becomes more challenging. Microencapsulated phase change material slurry (MPCMS), with its latent heat transfer properties, offers a potential solution. However, the low thermal conductivity of microencapsulated phase change material (MPCM) limits heat transfer rates, and most studies focus [...] Read more.

As avionics advance, heat dissipation becomes more challenging. Microencapsulated phase change material slurry (MPCMS), with its latent heat transfer properties, offers a potential solution. However, the low thermal conductivity of microencapsulated phase change material (MPCM) limits heat transfer rates, and most studies focus on improving conductivity, with little attention given to convective enhancement. This study prepared MPCMS with an MPCM mass fraction (W_m) of 10% and 20%, investigating melting heat transfer under mechanical stirring at 0–800 RPM and heat fluxes of 8.5–17.0 kW/m². Stirring significantly alters MPCMS heat transfer behavior. As rotational speed increases, both wall-to-slurry and internal temperature differences decrease. Stirring extends the time at which the heating wall temperature (T_w) stays below a threshold. For example, at W_m = 10% MPCM and 8.50 kW/m², increasing speed from 0 to 800 RPM raises the holding time below 70 °C by 169.6%. The effect of MPCM mass fraction on heat transfer under stirring is complex: at 0 RPM, 0% > 10% > 20%; at 400 RPM, 10% > 0% > 20%; and at 800 RPM, 10% > 20% > 0%. This is because as W_m increases, the latent heat and volume expansion coefficients of MPCMS rise, promoting heat transfer, while viscosity and thermal conductivity decrease, hindering it. At 0 RPM, the net effect is negative even at W_m = 10%. Stirring enhances internal convection and significantly improves heat transfer. At 400 RPM, heat transfer is positive at W_m = 10% but still negative at W_m = 20%. At 800 RPM, both W_m levels show positive effects, with slightly better performance at W_m = 10%. In addition, at the same heat flux, higher speeds maintain T_w below a threshold longer. Overall, stirring improves MPCMS cooling performance, offering an effective means of convective enhancement for avionics thermal management. Full article

(This article belongs to the Special Issue Aerospace Vehicle Optimization: Design Innovations, Thermal Management, and Practical Applications)

19 pages, 1424 KB

Open AccessArticle

Osprey Optimization Algorithm-Optimized Kriging-RBF Method for Radial Deformation Reliability Analysis of Compressor Blade Angle Crack

by Qiong Zhang, Shuguang Zhang and Xuyan He

Aerospace 2025, 12(10), 867; https://doi.org/10.3390/aerospace12100867 - 26 Sep 2025

Abstract

Angle crack defects significantly affect compressor blade radial deformation characteristics, posing critical challenges for reliability assessment under operational uncertainties. This study proposes a novel osprey optimization algorithm (OOA)-optimized Kriging and radial basis function (RBF) method (OOA-KR) for the efficient reliability evaluation of blade [...] Read more.

Angle crack defects significantly affect compressor blade radial deformation characteristics, posing critical challenges for reliability assessment under operational uncertainties. This study proposes a novel osprey optimization algorithm (OOA)-optimized Kriging and radial basis function (RBF) method (OOA-KR) for the efficient reliability evaluation of blade radial clearance with angle crack defects. The approach integrates Kriging’s uncertainty quantification capabilities with RBF neural networks’ nonlinear mapping strengths through an adaptive weighting scheme optimized by OOA. Multiple uncertainty sources including crack geometry, operational temperature, and loading conditions are systematically considered. A comprehensive finite element model incorporating crack size variations and multi-physics coupling effects generates training data for surrogate model construction. Comparative studies demonstrate superior prediction accuracy with RMSE = 0.568 and R² = 0.8842, significantly outperforming conventional methods while maintaining computational efficiency. Reliability assessment achieves 97.6% precision through Monte Carlo simulation. Sensitivity analysis reveals rotational speed as the most influential factor (S = 0.42), followed by temperature and loading parameters. The proposed OOA-KR method provides an effective tool for blade design optimization and reliability-based maintenance strategies. Full article

(This article belongs to the Special Issue State Monitoring and Health Management of Complex Equipment (3rd Edition))

28 pages, 14368 KB

Open AccessArticle

Containment Simulation and Test of the Whole Structure of an Air Turbine Starter

by Pengyu Zhu, Liqiang Chen, Haijun Xuan, Wenbin Jia, Wennan Chu and Zehui Fang

Aerospace 2025, 12(10), 866; https://doi.org/10.3390/aerospace12100866 - 26 Sep 2025

Abstract

The air turbine starter (ATS) of an aero-engine incorporates a high-speed, high-energy rotor. An uncontained failure of the ATS could lead to catastrophic consequences, making containment capability research critically important. This study proposes a comprehensive evaluation methodology for ATS containment. A full-scale finite [...] Read more.

The air turbine starter (ATS) of an aero-engine incorporates a high-speed, high-energy rotor. An uncontained failure of the ATS could lead to catastrophic consequences, making containment capability research critically important. This study proposes a comprehensive evaluation methodology for ATS containment. A full-scale finite element model of the whole structure of an ATS was established to analyze containment characteristics and structural deformation patterns. Furthermore, an experimental method for ATS containment testing was designed to investigate the containment process and critical structural damage. By integrating simulation and experimental results, the load transfer paths and structural dynamic response of the ATS were systematically analyzed. The results demonstrate that sudden high-energy loads primarily follow two distinct transfer paths, each causing completely different structural damage behaviors. After the turbine wheel is broken, the resulting unbalanced load causes turbine shaft oscillation, which, in turn, compresses the bearings and damages their inner and outer rings. This research provides valuable guidance for the structural design of air turbine starters. Full article

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

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24 pages, 1093 KB

Open AccessArticle

An Interval Analysis Method for Uncertain Multi-Objective Optimization of Solid Propellant Formulations

by Jiaren Ren, Ran Wei, Futing Bao and Xiao Hou

Aerospace 2025, 12(10), 865; https://doi.org/10.3390/aerospace12100865 - 25 Sep 2025

Abstract

To obtain propellant formulations with superior comprehensive and robustness performance, the study establishes a multi-objective optimization model that accounts for uncertainties. The model adopts a bi-layer structure. The inner layer computes performance bounds to construct uncertainty intervals, which are subsequently transformed into deterministic [...] Read more.

To obtain propellant formulations with superior comprehensive and robustness performance, the study establishes a multi-objective optimization model that accounts for uncertainties. The model adopts a bi-layer structure. The inner layer computes performance bounds to construct uncertainty intervals, which are subsequently transformed into deterministic performance via interval order relations. The outer layer optimizes component mass fractions using MOEA/D (Multi-objective Evolutionary Algorithm Based on Decomposition) to maximize the deterministic performance. The study leverages Large Language Models (LLMs) as pre-trained optimizers to automate the operator design of MOEA/D. Designers can identify formulations that satisfy the performance requirements and robustness criteria by adjusting uncertainty levels and MOEA/D weight coefficients. The results on ZDTs and UFs demonstrate that MOEA/D-LLM achieves approximately a 4.0% improvement in hypervolume values compared to MOEA/D. Additionally, the NEPE propellant optimization case shows that MOEA/D-LLM improves the computational speed by about 13.05% and enhances hypervolume values by around 2.7% compared to MOEA/D. The specific impulse increases by 1.11%, the generation of aluminum oxide and hydrogen chloride decreases by approximately 18.43% and 16.40%, respectively, and the impact sensitivity is reduced by about 1.67%. Full article

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

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12 pages, 2759 KB

Open AccessArticle

Numerical Study on Heat Transfer Characteristics of High-Temperature Alumina Droplet Impacting Carbon–Phenolic Ablative Material

by Gen Zhu, Xu Zhou, Weizhi Wu, Fugang Li and Yupeng Hu

Aerospace 2025, 12(10), 864; https://doi.org/10.3390/aerospace12100864 - 25 Sep 2025

Abstract

This study investigates the heat transfer characteristics of high-temperature alumina droplets impacting carbon–phenolic ablative materials in solid rocket motors using the Volume of Fluid (VOF) method. Simulations under varied droplet diameters, impact velocities, wall temperatures, and accelerations were carried out, and the simulation [...] Read more.

This study investigates the heat transfer characteristics of high-temperature alumina droplets impacting carbon–phenolic ablative materials in solid rocket motors using the Volume of Fluid (VOF) method. Simulations under varied droplet diameters, impact velocities, wall temperatures, and accelerations were carried out, and the simulation method was validated against experimental data. Results show that heat flux drops rapidly from 20 MW/m² to below 5 MW/m² after the non-dimensional time

t^{*}

= 0.5, due to solidified layer formation at the droplet bottom, which shifts heat transfer from convection to conduction and increases thermal resistance. The solidified layer is thicker at the sides and thinner in the center, caused by weaker heat transfer in the thinner side regions. Acceleration is found to have a negligible influence on impact dynamics within wall temperatures of 25 °C to 1000 °C, as potential energy conversion during spreading is insignificant compared to kinetic energy. Thus, droplet–wall heat transfer dominates the process. These findings provide critical thermal boundaries for ablation modeling and improve design guidance for SRMs. Full article

(This article belongs to the Special Issue Flow and Heat Transfer in Solid Rocket Motors)

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18 pages, 2325 KB

Open AccessArticle

Sampling-Based Adaptive Techniques for Reducing Non-Gaussian Position Errors in GNSS/INS Systems

by Yong Hun Kim, Joo Han Lee, Kyeong Wook Seo, Min Ho Lee and Jin Woo Song

Aerospace 2025, 12(10), 863; https://doi.org/10.3390/aerospace12100863 - 24 Sep 2025

Abstract

In this paper, we propose a novel method to reduce non-Gaussian errors in measurements using sampling-based distribution estimation. Although non-Gaussian errors are often treated as statistical deviations, they can frequently arise in practical unmanned aerial systems that depend on global navigation satellite systems [...] Read more.

In this paper, we propose a novel method to reduce non-Gaussian errors in measurements using sampling-based distribution estimation. Although non-Gaussian errors are often treated as statistical deviations, they can frequently arise in practical unmanned aerial systems that depend on global navigation satellite systems (GNSS), where position measurements are degraded by multipath effects. However, nonlinear or robust filters have shown limited effectiveness in correcting such errors, particularly when they appear as persistent biases in measurements over time. In such cases, adaptive techniques have often demonstrated greater effectiveness. The proposed method estimates the distribution of observed measurements using a sampling-based approach and derives a reformed measurement from this distribution. By incorporating this reformed measurement into the filter update, the proposed approach achieves lower error levels than traditional adaptive filters. To validate the effectiveness of the method, Kalman filter simulations are conducted for drone GNSS/INS navigation. The results show that the proposed method outperforms conventional non-Gaussian filters in handling measurement bias caused by non-Gaussian errors. Furthermore, it achieves nearly twice the estimation accuracy compared to adaptive approaches. These findings confirm the robustness of the proposed technique in scenarios where measurement accuracy temporarily deteriorates before recovering. Full article

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

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24 pages, 2107 KB

Open AccessArticle

An Experimental Study on Pitot Probe Icing Protection with an Electro-Thermal/Superhydrophobic Hybrid Strategy

by Haiyang Hu, Faisal Al-Masri and Hui Hu

Aerospace 2025, 12(10), 862; https://doi.org/10.3390/aerospace12100862 - 24 Sep 2025

Abstract

A series of experiments were carried out to evaluate different anti-/de-icing approaches for a Pitot probe. Using the Iowa State University Icing Research Tunnel (ISU-IRT), this study compared the performance of a traditional electrically heated system with that of a hybrid concept combining [...] Read more.

A series of experiments were carried out to evaluate different anti-/de-icing approaches for a Pitot probe. Using the Iowa State University Icing Research Tunnel (ISU-IRT), this study compared the performance of a traditional electrically heated system with that of a hybrid concept combining reduced-power electrical heating and a superhydrophobic surface (SHS) coating. The effectiveness and energy efficiency of both methods were assessed. High-speed imaging was employed to capture the transient ice accretion and removal phenomena on the probe model under a representative glaze icing condition, while infrared thermography provided surface temperature distributions to characterize the unsteady heat transfer behavior during the protection process. Results indicated that, due to the placement of the internal resistive heating elements, ice deposits on the total pressure tube were easier to shed than those on the supporting structure. Relative to the conventional approach of maintaining a fully heated probe, the hybrid technique achieved comparable anti-/de-icing performance with substantially reduced power requirements—showing up to ~50% savings during anti-icing operation and approximately 30% lower energy use with 24% faster removal during de-icing. These findings suggest that the hybrid strategy is a promising alternative for improving Pitot probe icing protection. Full article

(This article belongs to the Special Issue Deicing and Anti-Icing of Aircraft (Volume IV))

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25 pages, 5823 KB

Open AccessArticle

Study on Flow Field Characteristics of High-Speed Double-Row Ball Bearings with Under-Race Lubrication

by Xiaozhou Hu and Jian Lin

Aerospace 2025, 12(10), 861; https://doi.org/10.3390/aerospace12100861 - 24 Sep 2025

Abstract

As a core component of aero-engines, double-row ball bearings’ lubrication performance directly impacts the operational stability of the aircraft engine. However, existing under-race lubrication designs primarily rely on empirical knowledge, with insufficient understanding of the complex oil–air two-phase flow mechanisms, leading to bottlenecks [...] Read more.

As a core component of aero-engines, double-row ball bearings’ lubrication performance directly impacts the operational stability of the aircraft engine. However, existing under-race lubrication designs primarily rely on empirical knowledge, with insufficient understanding of the complex oil–air two-phase flow mechanisms, leading to bottlenecks in optimizing lubrication efficiency. Therefore, based on the computational fluid dynamics (CFD) method, a two-phase flow model for double-row ball bearings was established to systematically analyze the influence patterns of key parameters—including rotational speed, oil supply rate, number of under-race holes, diameter of under-race holes, and oil properties (viscosity, density)—on the distribution of the oil–air two-phase flow. The findings reveal that (1) the oil in the circumferential direction of the bearing cavity exhibits periodic distribution characteristics correlated with the number of under-race holes; (2) the self-rotation effect of balls hinders the migration of oil toward the outer raceway region, resulting in a significant reduction in the oil volume fraction within the bearing cavity; (3) compared with the single-sided oil supply configuration, the double-sided oil supply structure demonstrates superior lubrication performance. These research results provide theoretical support and reference data for the optimal design of under-race lubrication systems for double-row ball bearings. Full article

(This article belongs to the Section Aeronautics)

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24 pages, 2863 KB

Open AccessArticle

Multi-Point Design of Optimal Propellers for Remotely Piloted Aircraft Systems

by Alejandro Sanchez-Carmona, Kamil Sznajdrowicz-Rebisz, Alejandro Dominguez-Tuya, Carlos Balsalobre-Alvarez, Fernando Gandia-Aguera and Cristina Cuerno-Rejado

Aerospace 2025, 12(10), 860; https://doi.org/10.3390/aerospace12100860 - 24 Sep 2025

Abstract

This paper proposes a solution for the design of high-performance propellers optimized for various flight conditions. Considering both propulsion and electric motor efficiencies, a new design optimization methodology is proposed. The optimization of the electric propulsive system is directly achieved by simultaneously analyzing [...] Read more.

This paper proposes a solution for the design of high-performance propellers optimized for various flight conditions. Considering both propulsion and electric motor efficiencies, a new design optimization methodology is proposed. The optimization of the electric propulsive system is directly achieved by simultaneously analyzing the aerodynamic performance of the propeller and the motor. This study is focused on small, low-speed Remotely Piloted Aircraft Systems, addressing the design of fixed pitch propellers that operate efficiently over the entire speed range. The aerodynamic methodology uses combined blade element and momentum theory, which is adequate for a preliminary design phase with low computational time. For the aerodynamic coefficients of the airfoils used in these applications, at low Reynolds numbers, a new database was developed that incorporates airfoil experimental data and analytical methods to cover a wide range of angles of attack, beyond stall. For the modelling of the motor behavior, an idealization of the circuit was carried out, which considers its basic electric parameters. The results show significant improvements with respect to the information available for a current commercial propeller. Full article

(This article belongs to the Section Aeronautics)

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20 pages, 4583 KB

Open AccessArticle

A Novel Propeller Blade Design Method to Enhance Propulsive Efficiency for High-Thrust Electric UAVs

by Wenlong Shao, Chaobin Hu, Xiaomiao Chen and Xiangguo Kong

Aerospace 2025, 12(10), 859; https://doi.org/10.3390/aerospace12100859 - 24 Sep 2025

Abstract

Propellers are essential aerodynamic components widely used in aerospace engineering, marine vessels, and aerial platforms. With the growing demand for high-thrust electric unmanned aerial vehicles, greater emphasis is being placed on improving propeller aerodynamic performance and efficiency to enhance flight endurance and payload [...] Read more.

Propellers are essential aerodynamic components widely used in aerospace engineering, marine vessels, and aerial platforms. With the growing demand for high-thrust electric unmanned aerial vehicles, greater emphasis is being placed on improving propeller aerodynamic performance and efficiency to enhance flight endurance and payload capacity. Traditional design methods, mostly based on blade element theory, simplify the blade into two-dimensional planar elements, making it difficult to accurately capture the three-dimensional streamline characteristics during rotation. This mismatch between geometric design and actual flow limits further improvements in propulsion efficiency. This paper proposes a two-dimensional airfoil body-fitted design method to address this limitation. This method is based on blade element theory and vortex theory to obtain the chord length and pitch angle distribution under specific operating conditions. Based on these distributions, each blade element is bent to fit a virtual cylindrical surface at the corresponding position. This ensures that all points on the two-dimensional airfoil are equidistant from the hub center. The proposed design method is validated through numerical simulations. The results show that the propeller designed with the body-fitted method improves efficiency by 4.2% compared with the one designed using blade element theory. This work provides a new technical approach for propeller design and has practical value for improving propeller efficiency. Full article

(This article belongs to the Section Aeronautics)

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21 pages, 6887 KB

Open AccessArticle

Power Contingency/Margin Methodology and Operational Envelope Analysis for PlanarSats

by Mehmet Şevket Uludağ and Alim Rüstem Aslan

Aerospace 2025, 12(10), 858; https://doi.org/10.3390/aerospace12100858 - 24 Sep 2025

Abstract

This paper presents a power-centric systems-engineering approach for PlanarSats and for atto-, and femto-class spacecraft where surface-limited power dominates design. We review agency practices (The National Aeronautics and Space Administration (NASA), European Space Agency (ESA), Japan Aerospace Exploration Agency (JAXA)) and the American [...] Read more.

This paper presents a power-centric systems-engineering approach for PlanarSats and for atto-, and femto-class spacecraft where surface-limited power dominates design. We review agency practices (The National Aeronautics and Space Administration (NASA), European Space Agency (ESA), Japan Aerospace Exploration Agency (JAXA)) and the American Institute of Aeronautics and Astronautics (AIAA) framework, then extend them with refined low-power subcategories and a log-linear method for selecting phase- and class-appropriate power contingencies. The method is applied to historical and conceptual PlanarSats to show how contingencies translate into required array area, allowable incidence angles, and duty cycle, linking power sizing to geometry and operations. We define the operational power envelope as the range of satellite orientations and conditions under which generated power meets or exceeds mission requirements. Consistent with agency guidance, sizing is performed to the maximum expected value (MEV) (CBE plus contingency); when bounding or stress analyses are needed, we report the maximum possible value (MPV) (Maximum Possible Value) by applying justified system-level margins to the MEV. Results indicate that disciplined, phase-aware contingency selection materially reduces power-related risk and supports reliable, scalable PlanarSat missions under severe physical constraints. Full article

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

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27 pages, 1244 KB

Open AccessArticle

Effects of Unplanned Incoming Flights on Airport Relief Processes After a Major Natural Disaster

by Luka Van de Sype, Matthieu Vert, Alexei Sharpanskykh and Seyed Sahand Mohammadi Ziabari

Aerospace 2025, 12(10), 857; https://doi.org/10.3390/aerospace12100857 - 24 Sep 2025

Abstract

The severity of natural disasters is increasing every year, having an impact on many people’s lives. During the response phase of disasters, airports are important hubs where relief aid arrives while people need to be evacuated to safety. However, the airport often forms [...] Read more.

The severity of natural disasters is increasing every year, having an impact on many people’s lives. During the response phase of disasters, airports are important hubs where relief aid arrives while people need to be evacuated to safety. However, the airport often forms a bottleneck in these relief operations because of the sudden need for increased capacity. Limited research is carried out on the operational side of airport disaster management. Experts identify the main problems as first the asymmetry of information between the airport and the incoming flights, and second the lack of resources. The goal of this research is to gain understanding of the effects of incomplete knowledge of incoming flights with different resource allocation strategies on the performance of the cargo handling operations in an airport after a natural disaster event. An agent-based model is created, where realistic offloading strategies with different degrees of information uncertainty are implemented. Model calibration and verification are performed with experts in the field. The model performance is measured by the average turnaround time, which can be split into offloading time, boarding time and the cumulative waiting times. The results show that the effects of one unplanned aircraft are negligible. However, the waiting times and other inefficiencies rapidly increase with the more unplanned aircraft arriving. Full article

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

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22 pages, 2630 KB

Open AccessArticle

Research on Congestion Situation Relief in Terminal Area Based on Flight Path Adjustment

by Yuren Ji, Fuping Yu, Di Shen and Yating Peng

Aerospace 2025, 12(10), 856; https://doi.org/10.3390/aerospace12100856 - 23 Sep 2025

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Abstract

With the continuous growth of air transportation demand, air traffic congestion in the Terminal Area has become increasingly serious. In order to assist controllers in efficiently alleviating the traffic congestion situation in the Terminal Area, this paper takes aircraft trajectory adjustment and flow [...] Read more.

With the continuous growth of air transportation demand, air traffic congestion in the Terminal Area has become increasingly serious. In order to assist controllers in efficiently alleviating the traffic congestion situation in the Terminal Area, this paper takes aircraft trajectory adjustment and flow control from the perspective of the Terminal Area as a starting point and proposes a congestion relief strategy based on a complex network and multi-objective optimization theory. First, a Terminal Area traffic network model is established with the approach point, departure point, waypoint, and navigation station as nodes and the flight path as edges. Next, a multi-objective optimization model that takes into account both congestion relief and reduced operating costs is constructed. Finally, an improved ant colony optimization is proposed to solve this optimization model and provide a unified approach to path planning for multiple aircraft. Finally, simulation experiments were conducted based on the airspace structure and operation of the Beijing Terminal Area. At the same time, ablation experiments were designed to compare the method in this paper with other ant colony optimizations. The experimental results show that the path planning results of the improved ant colony optimization can better alleviate the traffic congestion situation in the Terminal Area, converge faster, and reduce the risk of falling into a local optimum. Full article

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

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Aerospace, Volume 12, Issue 10 (October 2025) – 13 articles

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