Aerospace

22 pages, 7181 KiB

Open AccessArticle

Satellite Navigation of a Lunar Rover with Sensor Fusion for High-Accuracy Navigation

by Marco Sabatini, Giovanni B. Palmerini, Filippo Rodriguez, Riccardo Petix, Gabriele Lambiase and Pietro Pacchiarotti

Aerospace 2025, 12(7), 565; https://doi.org/10.3390/aerospace12070565 - 20 Jun 2025

Abstract

The Moon has become the focus of renewed interest for numerous space agencies and private companies worldwide. In the coming years, various scientific and commercial missions are planned, with a particular emphasis on exploring the South Pole. These missions include orbiters, landers, as [...] Read more.

The Moon has become the focus of renewed interest for numerous space agencies and private companies worldwide. In the coming years, various scientific and commercial missions are planned, with a particular emphasis on exploring the South Pole. These missions include orbiters, landers, as well as both static and mobile rovers. For all these operations, continuous and accurate position knowledge is essential. This paper evaluates the performance of a navigation system designed for a lunar rover using the future satellite navigation infrastructure. It highlights the critical role of integrating multiple information sources, including a Digital Elevation Model (DEM) of the lunar surface and a high-precision Inertial Measurement Unit (IMU). The results demonstrate that a comprehensive suite of instruments enables highly accurate and reliable navigation for a mobile rover. While standalone satellite navigation, due to the reduced number of available sources, offers navigation accuracy of the orders of tens of meters, the addition of the DEM lowers the error at 5 m level; the IMU further improve by roughly 40% the performance on horizontal positioning. Full article

(This article belongs to the Special Issue Advances in Lunar Exploration)

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13 pages, 3148 KiB

Open AccessArticle

Reconstruction and Separation Method of Ranging and Communication Phase in Beat-Note for Micro-Radian Phasemeter

by Tao Yu, Hongyu Long, Ke Xue, Mingzhong Pan, Zhi Wang and Yunqing Liu

Aerospace 2025, 12(7), 564; https://doi.org/10.3390/aerospace12070564 - 20 Jun 2025

Abstract

The primary measurement involves detecting tiny (picometer-level) pathlength fluctuations between satellites using heterodyne laser interferometry for space-based gravitational wave detection. The interference of two laser beams with a MHz-level frequency difference produces a MHz beat-note, in which the gravitational wave signal is encoded [...] Read more.

The primary measurement involves detecting tiny (picometer-level) pathlength fluctuations between satellites using heterodyne laser interferometry for space-based gravitational wave detection. The interference of two laser beams with a MHz-level frequency difference produces a MHz beat-note, in which the gravitational wave signal is encoded in the phase of the beat-note. The phasemeter then performs micro-radian accuracy phase measurement and communication information demodulation for this beat-note. To mitigate the impact of phase modulation, existing solutions mostly alleviate it by reducing the modulation depth and optimizing the structure of the pseudo-random noise (PRN) codes. Since the phase modulation is not effectively separated from the phase of the beat-note phase measurement, it has a potential impact on the phase extraction of the micro-radian accuracy of the beat-note. To solve this problem, this paper analyzes the influence mechanism of phase modulation on beat-note phase measurement and proposes a method to separate the modulated phase based on complex rotation. The beat-note is processed by complex conjugate rotation, which can effectively eliminate the PRN modulated phase. Simulation and analysis results demonstrate that this method can significantly enhance the purity of the measured phase in the beat-note while maintaining the ranging and communication functions. Targeting the application of the micro-radian phasemeter in space-based gravitational wave detection, this study presents the reconstruction and separation method of the ranging and communication phase in beat-note, which also provides a new direction for the final selection of modulation depth in the future. Full article

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

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26 pages, 17358 KiB

Open AccessArticle

Direct Numerical Simulation of Flow and Heat Transfer in a Compressor Blade Passage Across a Range of Reynolds Numbers

by Yang Liu, Chenchen Zhao, Lei Zhou, Duo Wang and Hongyi Xu

Aerospace 2025, 12(6), 563; https://doi.org/10.3390/aerospace12060563 - 19 Jun 2025

Abstract

This study employs Direct Numerical Simulation (DNS) to investigate the flow and heat transfer characteristics in a compressor blade passage at five Reynolds numbers (

R e = 1.091 \times 10^{5}

,

1.229 \times 10^{5}

,

1.367 \times 10^{5}

, [...] Read more.

This study employs Direct Numerical Simulation (DNS) to investigate the flow and heat transfer characteristics in a compressor blade passage at five Reynolds numbers (

R e = 1.091 \times 10^{5}

,

1.229 \times 10^{5}

,

1.367 \times 10^{5}

,

1.506 \times 10^{5}

, and

1.645 \times 10^{5}

). A recent method based on local inviscid velocity reconstruction is applied to define and calculate boundary layer parameters, whereas the Rortex vortex identification method is used to analyze turbulent vortical structures. Results indicate that

R e

significantly affects separation bubble size, transition location, and reattachment behavior, thereby altering wall heat transfer characteristics. On the pressure surface, separation and early transition are observed at higher

R e

, with the Nusselt number (

N u

) remaining high after transition. On the suction surfaces, separation occurs such that large-scale separation at low

R e

reduces

N u

, while reattachment combined with turbulent mixing at high

R e

significantly increases

N u

. Turbulent vortical structures enhance near-wall fluid mixing through induced ejection and sweep events, thereby promoting momentum and heat transport. As

R e

increases, the vortical structures become denser with reduced scales and the peaks in heat flux move closer to the wall, thus improving convective heat transfer efficiency. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications (2nd Edition))

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29 pages, 11218 KiB

Open AccessArticle

Transient Temperature Evaluation and Thermal Management Optimization Strategy for Aero-Engine Across the Entire Flight Envelope

by Weilong Gou, Shiyu Yang, Kehan Liu, Yuanfang Lin, Xingang Liang and Bo Shi

Aerospace 2025, 12(6), 562; https://doi.org/10.3390/aerospace12060562 - 19 Jun 2025

Abstract

With the enhancement of thermodynamic cycle parameters and heat dissipation constraints in aero-engines, effective thermal management has become a critical challenge to ensure safe and stable engine operation. This study developed a transient temperature evaluation model applicable to the entire flight envelope, considering [...] Read more.

With the enhancement of thermodynamic cycle parameters and heat dissipation constraints in aero-engines, effective thermal management has become a critical challenge to ensure safe and stable engine operation. This study developed a transient temperature evaluation model applicable to the entire flight envelope, considering fluid–solid coupling heat transfer on both the main flow path and fuel systems. Firstly, the impact of heat transfer on the acceleration and deceleration performance of a low-bypass-ratio turbofan engine was analyzed. The results indicate that, compared to the conventional adiabatic model, the improved model predicts metal components absorb 4.5% of the total combustor energy during cold-state acceleration, leading to a maximum reduction of 1.42 kN in net thrust and an increase in specific fuel consumption by 1.18 g/(kN·s). Subsequently, a systematic evaluation of engine thermal management performance throughout the complete flight mission was conducted, revealing the limitations of the existing thermal management design and proposing targeted optimization strategies, including employing Cooled Cooling Air technology to improve high-pressure turbine blade cooling efficiency, dynamically adjusting low-pressure turbine bleed air to minimize unnecessary losses, optimizing fuel heat sink utilization for enhanced cooling performance, and replacing mechanical pumps with motor pumps for precise fuel supply control. Full article

(This article belongs to the Special Issue Aircraft Thermal Management Technologies)

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24 pages, 5570 KiB

Open AccessArticle

Study on Propellant Management Device for Small-Scale Supersonic Flight Experiment Vehicle

by Ryoji Imai and Takuya Wada

Aerospace 2025, 12(6), 561; https://doi.org/10.3390/aerospace12060561 - 19 Jun 2025

Abstract

To commercialize supersonic and hypersonic passenger aircraft and reusable spaceplanes, we are developing a small-scale supersonic flight experiment vehicle as a flying testbed for technical demonstrations in high-speed flight environments. This experiment vehicle is equipped with a fuel tank and an oxidizer tank, [...] Read more.

To commercialize supersonic and hypersonic passenger aircraft and reusable spaceplanes, we are developing a small-scale supersonic flight experiment vehicle as a flying testbed for technical demonstrations in high-speed flight environments. This experiment vehicle is equipped with a fuel tank and an oxidizer tank, and the propellants inside the tanks slosh due to changes in acceleration during flight. In this situation, there is a risk of gas entrainment during liquid discharge, which could potentially cause an engine malfunction. To avoid such a situation, we considered installing a propellant management device (PMD) inside the tank to suppress the gas entrainment. In this study, a capillary type PMD with a screen channel structure, commonly used in satellites featuring no moving parts, was adopted due to its applicability to a wide acceleration range. The PMD was designed with a structure featuring cylindrical mesh screen nozzles installed at the top and bottom of a cylindrical tank. A one-dimensional flow analysis model was developed taking into account factors such as the pressure loss across the mesh screens and the flow loss within the mesh screen nozzles, which enabled the identification of conditions under which gas entrainment occurred. In this analytical model, separate formulations were developed using Hartwig’s and Ingmanson’s formulas for evaluating the flow losses through the mesh screens. Furthermore, by applying the flow analysis model, the specifications of the mesh screens as key parameters of the PMD, together with the nozzle diameter and nozzle length, were selected. Moreover, we fabricated prototype PMDs with each nozzle and conducted visualization tests using a transparent tank. The tests were conducted under static conditions, where a gravitational acceleration acted downward, and the effects of the cylindrical mesh screen length and discharge flow rate on the free surface height at which gas entrainment occurred were investigated. This experiment demonstrated the effectiveness of the propellant acquisition mechanism of the present PMD. The height of the free surface was also compared with the experimental and analytical results, and it was shown that the results obtained by using Ingmanson’s formula for pressure loss through the screen mesh were closer to the experimental results. These findings demonstrated the validity of the one-dimensional flow analysis model. Full article

(This article belongs to the Section Aeronautics)

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15 pages, 6013 KiB

Open AccessArticle

Urban Air Mobility Vertiport’s Capacity Simulation and Analysis

by Antoni Kopyt and Sebastian Dylicki

Aerospace 2025, 12(6), 560; https://doi.org/10.3390/aerospace12060560 - 19 Jun 2025

Abstract

This study shows a comprehensive simulation to assess and enhance the throughput capacity of unmanned air system vertiports, one of the most essential elements of urban air mobility ecosystems. The framework integrates dynamic grid-based spatial management, probabilistic mission duration algorithms, and EASA-compliant operational [...] Read more.

This study shows a comprehensive simulation to assess and enhance the throughput capacity of unmanned air system vertiports, one of the most essential elements of urban air mobility ecosystems. The framework integrates dynamic grid-based spatial management, probabilistic mission duration algorithms, and EASA-compliant operational protocols to address the infrastructural and logistical demands of high-density UAS operations. It was focused on two use cases—high-frequency food delivery utilizing small UASs and extended-range package logistics with larger UASs—and the model incorporates adaptive vertiport zoning strategies, segregating operations into dedicated sectors for battery charging, swapping, and cargo handling to enable parallel processing and mitigate congestion. The simulation evaluates critical variables such as vertiport dimensions, UAS fleet composition, and mission duration ranges while emphasizing scalability, safety, and compliance with evolving regulatory standards. By examining the interplay between infrastructure design, operational workflows, and resource allocation, the research provides a versatile tool for urban planners and policymakers to optimize vertiport layouts and traffic management protocols. Its modular architecture supports future extensions. This work underscores the necessity of adaptive, data-driven planning to harmonize vertiport functionality with the dynamic demands of urban air mobility, ensuring interoperability, safety, and long-term scalability. Full article

(This article belongs to the Special Issue Operational Requirements for Urban Air Traffic Management)

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35 pages, 6969 KiB

Open AccessArticle

Building Credible VTOL Flight Models for Handling Quality Certification by Simulation

by Lorenzo Favaro, Agata Rylko and Giuseppe Quaranta

Aerospace 2025, 12(6), 559; https://doi.org/10.3390/aerospace12060559 - 19 Jun 2025

Abstract

Certifying novel VTOL aircraft handling qualities (HQs) may be challenging, relying on costly and high-risk flight testing. This paper presents a methodology to establish the credibility of flight simulation models for certification by simulation, aiming to bridge the gap between the model input [...] Read more.

Certifying novel VTOL aircraft handling qualities (HQs) may be challenging, relying on costly and high-risk flight testing. This paper presents a methodology to establish the credibility of flight simulation models for certification by simulation, aiming to bridge the gap between the model input uncertainty and certification confidence. The core objective is to assess if a model, despite its inherent uncertainties, can reliably predict the handling quality compliance for specific flight tasks. This is achieved by quantifying the impact of input parameter uncertainties on predicted handling qualities and, crucially, by evaluating the envelope of the resulting uncertain aircraft transfer functions—scaled by a confidence ratio—against established maximum unnoticeable added dynamics boundaries. Applied to a lift + cruise VTOL model performing a deceleration-to-hover manoeuvre, the study demonstrates that while longitudinal control dynamics largely remained within MUAD limits, indicating the model’s credibility for those aspects, vertical axis dynamics coupled with longitudinal inputs for some uncertain configurations exceeded these limits, correlating with observed flight test performance variability. Readers will find a structured, quantitative approach to model validation for HQ certification by simulation, leveraging MUAD to determine if a nominal model is sufficiently representative for certification, thereby supporting safer and more efficient VTOL development. Full article

(This article belongs to the Section Aeronautics)

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22 pages, 3653 KiB

Open AccessArticle

Nonlinear Model and Ballistic Impact of Body Aerodynamics for Canard Dual-Spin Aircraft

by Xinxin Zhao, Jinguang Shi, Huajie Ren and Zhongyuan Wang

Aerospace 2025, 12(6), 558; https://doi.org/10.3390/aerospace12060558 - 18 Jun 2025

Abstract

Targeting the nonlinear issues of the canard dual-spin aircraft, which relies on the high-speed rotation of the afterbody for flight stability and achieves trajectory correction by adjusting the roll angle of the low-speed rotating forebody to alter aerodynamics, the establishment of an accurate [...] Read more.

Targeting the nonlinear issues of the canard dual-spin aircraft, which relies on the high-speed rotation of the afterbody for flight stability and achieves trajectory correction by adjusting the roll angle of the low-speed rotating forebody to alter aerodynamics, the establishment of an accurate aerodynamic model is crucial for in-depth studies of its ballistic characteristics and design. For this, by taking the effects of canard–body interference, fore/aft body reversal, and other factors into account, an accurate model of the body aerodynamics applicable to large angles of attack is presented. This model theoretically elucidates the intricate relationship between the body aerodynamics and both the flight state and the aerodynamic parameters of the original aircraft. Subsequently, numerical simulations are conducted to analyze the body nonlinear aerodynamic characteristics and their impact on ballistics. The results reveal that all aerodynamic forces and moments acting on the aircraft body, particularly the Magnus force and moment, exhibit strong nonlinearities due to the coupling between the forebody roll angle and the amplitude and phase of the complex angle of attack. Moreover, the established model accurately captures the body aerodynamics and the influence of various disturbance factors, which can significantly alter the controlled angular motions and corrected ballistic calculations. Full article

(This article belongs to the Section Aeronautics)

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26 pages, 8994 KiB

Open AccessArticle

Output Feedback Fuzzy Gain Scheduling for MIMO Systems Applied to Flexible Aircraft Control

by Guilherme C. Barbosa and Flávio J. Silvestre

Aerospace 2025, 12(6), 557; https://doi.org/10.3390/aerospace12060557 - 18 Jun 2025

Abstract

Previous works by our group evidenced stability problems associated with flight control law design for flexible aircraft regarding gain scheduling. This paper proposes an output feedback fuzzy-based gain scheduling approach to adequate closed-loop response in a broader range of the flight envelope. This [...] Read more.

Previous works by our group evidenced stability problems associated with flight control law design for flexible aircraft regarding gain scheduling. This paper proposes an output feedback fuzzy-based gain scheduling approach to adequate closed-loop response in a broader range of the flight envelope. This method applies a variation of the controller gains based on the membership function design for all the varying parameters, such as dynamic pressure. It aims for performance improvement while enforcing global stability gain scheduling. The technique was demonstrated for the flexible ITA X-HALE aircraft nonlinear model and compared to the classical interpolation-based gain scheduling technique. The results revealed that fuzzy-based gain scheduling can effectively handle high-order systems while ensuring global system stability, leading to an overall improvement in performance. Full article

(This article belongs to the Special Issue Aerodynamics, Flight Dynamics and Control of Advanced Air Mobility Vehicles)

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35 pages, 6410 KiB

Open AccessArticle

Conceptual Design of a Low-Cost Class-III Turbofan-Based UCAV Loyal Wingman

by Savvas Roussos, Eleftherios Karatzas, Vassilios Kostopoulos and Vaios Lappas

Aerospace 2025, 12(6), 556; https://doi.org/10.3390/aerospace12060556 - 18 Jun 2025

Abstract

The rapid evolution of military technology has led to an increased interest in Unmanned Combat Aerial Vehicles (UCAVs). This research focuses on the conceptual design of a low-cost, turbofan-powered UCAV, specifically a Class-III aircraft as defined by NATO classification (STANAG 4670), with a [...] Read more.

The rapid evolution of military technology has led to an increased interest in Unmanned Combat Aerial Vehicles (UCAVs). This research focuses on the conceptual design of a low-cost, turbofan-powered UCAV, specifically a Class-III aircraft as defined by NATO classification (STANAG 4670), with a target take-off weight of approximately one tonne. The study adopts a “from scratch” design approach, recognizing the limitations of existing data and the potential for scaling errors. This approach involves a meticulous design process that includes the development of precise requirements, weight estimations, and iterative optimization of the aircraft layout to ensure aerodynamic efficiency and operational functionality. A key element of this conceptual design is its focus on a low-cost profile, achieved through the adoption of a simplified structural layout, and the integration of off-the-shelf components where possible. The design process involves an iterative approach, beginning with fundamental requirements and progressing through the detailed development of individual components and their integration into a cohesive aircraft. The study details the selection of an existing and operational engine due to its power output. The design and analysis of the wing, fuselage, and V-tail configuration are presented, incorporating considerations for aerodynamic efficiency, stability, weight estimation, and internal component layout. The study concludes by outlining recommendations for future work, including high-fidelity CFD simulations, structural analysis, and the integration of advanced electronic systems and AI capabilities essential for the Loyal Wingman concept. Full article

(This article belongs to the Special Issue UAV System Modelling Design and Simulation)

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39 pages, 3674 KiB

Open AccessArticle

Enhancing Model Generalizability in Aircraft Carbon Brake Wear Prediction: A Comparative Study and Transfer Learning Approach

by Patsy Jammal, Olivia Pinon Fischer, Dimitri N. Mavris and Gregory Wagner

Aerospace 2025, 12(6), 555; https://doi.org/10.3390/aerospace12060555 - 18 Jun 2025

Abstract

Predictive maintenance in commercial aviation demands highly reliable and robust models, particularly for critical components like carbon brakes. This paper addresses two primary concerns in modeling carbon brake wear for distinct aircraft variants: (1) the choice between developing specialized models for individual aircraft [...] Read more.

Predictive maintenance in commercial aviation demands highly reliable and robust models, particularly for critical components like carbon brakes. This paper addresses two primary concerns in modeling carbon brake wear for distinct aircraft variants: (1) the choice between developing specialized models for individual aircraft types versus a unified, general model, and (2) the potential of transfer learning (TL) to boost model performance across diverse domains (e.g., aircraft types). We evaluate the trade-offs between predictive performance and computational efficiency by comparing specialized models tailored to specific aircraft types with a generalized model designed to predict continuous wear values across multiple aircraft types. Additionally, we explore the efficacy of TL in leveraging existing domain knowledge to enhance predictions in new, related contexts. Our findings demonstrate that a well-tuned generalized model supported by TL offers a viable approach to reducing model complexity and computational demands while maintaining robust and reliable predictive performance. The implications of this research extend beyond aviation, suggesting broader applications in component predictive maintenance where data-driven insights are crucial for operational efficiency and safety. Full article

(This article belongs to the Section Aeronautics)

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33 pages, 1265 KiB

Open AccessArticle

Sizing of Fuel Distribution and Thermopropulsion Systems for Liquid-Hydrogen-Powered Aircraft Using an MBSE Approach

by Abdoulaye Sarr, Joël Jézégou and Pierre de Saqui-Sannes

Aerospace 2025, 12(6), 554; https://doi.org/10.3390/aerospace12060554 - 17 Jun 2025

Abstract

Hydrogen-powered aircraft constitute a transformative innovation in aviation, motivated by the imperative for sustainable and environmentally friendly transportation solutions. This paper aims to concentrate on the design of hydrogen powertrains employing a system approach to propose representative design models for distribution and propulsion [...] Read more.

Hydrogen-powered aircraft constitute a transformative innovation in aviation, motivated by the imperative for sustainable and environmentally friendly transportation solutions. This paper aims to concentrate on the design of hydrogen powertrains employing a system approach to propose representative design models for distribution and propulsion systems. Initially, the requirements for powertrain design are formalized, and a use-case-driven analysis is conducted to determine the functional and physical architectures. Subsequently, for each component pertinent to preliminary design, an analytical model is proposed for multidisciplinary analysis and optimization for powertrain sizing. A double-wall pipe model, incorporating foam and vacuum multi-layer insulation, was developed. The internal and outer pipes sizing were performed in accordance with standards for hydrogen piping design. Valves sizing is also considered in the present study, following current standards and using data available in the literature. Furthermore, models for booster pumps to compensate pressure drop and high-pressure pumps to elevate pressure at the combustion chamber entrance are proposed. Heat exchanger and evaporator models are also included and connected to a burning hydrogen engine in the sizing process. An optimal liner pipe diameter was identified, which minimizes distribution systems weight. We also expect a reduction in engine length and weight while maintaining equivalent thrust. Full article

(This article belongs to the Section Aeronautics)

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25 pages, 2540 KiB

Open AccessArticle

Two-Stage Uncertain UAV Combat Mission Assignment Problem Based on Uncertainty Theory

by Haitao Zhong, Rennong Yang, Aoyu Zheng, Mingfa Zheng and Yu Mei

Aerospace 2025, 12(6), 553; https://doi.org/10.3390/aerospace12060553 - 17 Jun 2025

Abstract

Based on uncertainty theory, this paper studies the problem of unmanned aerial vehicle (UAV) combat mission assignment under an uncertain environment. First, considering both the target value, which is the combat mission benefit gained from attacking the target, and the unit fuel consumption [...] Read more.

Based on uncertainty theory, this paper studies the problem of unmanned aerial vehicle (UAV) combat mission assignment under an uncertain environment. First, considering both the target value, which is the combat mission benefit gained from attacking the target, and the unit fuel consumption of UAV as uncertain variables, an uncertain UAV combat mission assignment model is established. And according to decisions under the realization of uncertain variables, the first stage generates an initial mission allocation scheme corresponding to the realization of target value, while the second stage dynamically adjusts the scheme according to the realization of unit fuel consumption; a two-stage uncertain UAV combat mission assignment (TUCMA) model is obtained. Then, because of the difficulty of obtaining analytical solutions due to uncertainty and the complexity of solving the second stage, the TUCMA model is transformed into an expected value-effective deterministic model of the two-stage uncertain UAV combat mission assignment (ETUCMA). A modified particle swarm optimization (PSO) algorithm is designed to solve the ETUCMA model to get the expected value-effective solution of the TUCMA model. Finally, experimental simulations of multiple UAV combat task allocation scenarios demonstrate that the proposed modified PSO algorithm yields an optimal decision with maximum combat mission benefits under a maximum iteration limit, which are significantly greater benefits than those for the mission assignment achieved by the original PSO algorithm. The proposed modified PSO exhibits superior performance compared with the ant colony optimization algorithm, enabling the acquisition of an optimal allocation scheme with greater benefits. This verifies the effectiveness and superiority of the proposed model and algorithm in maximizing combat mission benefits. Full article

(This article belongs to the Section Aeronautics)

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24 pages, 6794 KiB

Open AccessArticle

A Multi-Scale Airspace Sectorization Framework Based on QTM and HDQN

by Qingping Liu, Xuesheng Zhao, Xinglong Wang, Mengmeng Qin and Wenbin Sun

Aerospace 2025, 12(6), 552; https://doi.org/10.3390/aerospace12060552 - 17 Jun 2025

Abstract

Airspace sectorization is an effective approach to balance increasing air traffic demand and limited airspace resources. It directly impacts the efficiency and safety of airspace operations. Traditional airspace sectorization methods are often based on fixed spatial scales, failing to fully consider the complexity [...] Read more.

Airspace sectorization is an effective approach to balance increasing air traffic demand and limited airspace resources. It directly impacts the efficiency and safety of airspace operations. Traditional airspace sectorization methods are often based on fixed spatial scales, failing to fully consider the complexity and interrelationships of airspace partitioning across different spatial scales. This makes it challenging to balance large-scale airspace management with local dynamic demands. To address this issue, a multi-scale airspace sectorization framework is proposed, which integrates a multi-resolution grid system and a hierarchical deep reinforcement learning algorithm. First, an airspace grid model is constructed using Quaternary Triangular Mesh (QTM), along with an efficient workload calculation model based on grid encoding. Then, a sector optimization model is developed using hierarchical deep Q-network (HDQN), where the top-level and bottom-level policies coordinate to perform global airspace control area partitioning and local sectorization. The use of multi-resolution grids enhances the interaction efficiency between the reinforcement learning model and the environment. Prior knowledge is also incorporated to enhance training efficiency and effectiveness. Experimental results demonstrate that the proposed framework outperforms traditional models in both computational efficiency and workload balancing performance. Full article

(This article belongs to the Special Issue AI, Machine Learning and Automation for Air Traffic Control (ATC))

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17 pages, 1804 KiB

Open AccessArticle

Semantic Topic Modeling of Aviation Safety Reports: A Comparative Analysis Using BERTopic and PLSA

by Aziida Nanyonga, Keith Joiner, Ugur Turhan and Graham Wild

Aerospace 2025, 12(6), 551; https://doi.org/10.3390/aerospace12060551 - 16 Jun 2025

Abstract

Aviation safety analysis increasingly relies on extracting actionable insights from narrative incident reports to support risk identification and improve operational safety. Topic modeling techniques such as Probabilistic Latent Semantic Analysis (pLSA) and BERTopic offer automated methods to uncover latent themes in unstructured safety [...] Read more.

Aviation safety analysis increasingly relies on extracting actionable insights from narrative incident reports to support risk identification and improve operational safety. Topic modeling techniques such as Probabilistic Latent Semantic Analysis (pLSA) and BERTopic offer automated methods to uncover latent themes in unstructured safety narratives. This study evaluates the effectiveness of each model in generating coherent, interpretable, and semantically meaningful topics for aviation safety practitioners and researchers. We assess model performance using both quantitative metrics (topic coherence scores) and qualitative evaluations of topic relevance. The findings show that while pLSA provides a solid probabilistic framework, BERTopic leveraging transformer-based embeddings and HDBSCAN clustering produces more nuanced, context-aware topic groupings, albeit with increased computational demands and tuning complexity. These results highlight the respective strengths and trade-offs of traditional versus modern topic modeling approaches in aviation safety analysis. This work advances the application of natural language processing (NLP) in aviation by demonstrating how topic modeling can support risk assessment, inform policy, and enhance safety outcomes. Full article

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

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78 pages, 31327 KiB

Open AccessReview

An Overview of CubeSat Missions and Applications

by Konstantinos-Panagiotis Bouzoukis, Georgios Moraitis, Vassilis Kostopoulos and Vaios Lappas

Aerospace 2025, 12(6), 550; https://doi.org/10.3390/aerospace12060550 - 16 Jun 2025

Abstract

The proliferation of CubeSats in Earth orbit has accelerated dramatically in recent years, with projections indicating continued growth in the coming decades. This review examines the evolution of CubeSat applications, from basic technology demonstrations to complex mission capabilities, including Earth observation, telecommunications, astronomical [...] Read more.

The proliferation of CubeSats in Earth orbit has accelerated dramatically in recent years, with projections indicating continued growth in the coming decades. This review examines the evolution of CubeSat applications, from basic technology demonstrations to complex mission capabilities, including Earth observation, telecommunications, astronomical research, biological experimentation, and deep-space exploration. A notable shift has occurred over the past fifteen years, with CubeSats transitioning from standalone platforms to integrated nodes within larger constellations, particularly for Earth observation and telecommunications applications. We analyze the key enabling factors behind the CubeSat revolution, including decreased launch costs, miniaturized electronics, standardized components, and institutional support frameworks. Through the examination of significant past, current, and planned missions, this paper provides a comprehensive overview of CubeSat capabilities across diverse application domains. The review highlights how these miniaturized satellite platforms are democratizing access to space while enabling innovative scientific and commercial applications previously restricted to larger spacecraft. Full article

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

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18 pages, 6509 KiB

Open AccessArticle

Operation of Vacuum Arc Thruster Arrays with Multiple Isolated Current Sources

by Benjamin Kanda and Minkwan Kim

Aerospace 2025, 12(6), 549; https://doi.org/10.3390/aerospace12060549 - 16 Jun 2025

Abstract

Vacuum arc thrusters (VATs) have recently gained significant interest as a micro-propulsion system due to their scalability, low cost, storability, and small form factor. While VATs offer an attractive propulsion solution for CubeSats, conventional propellant feed systems used in VATs require intricate mechanical [...] Read more.

Vacuum arc thrusters (VATs) have recently gained significant interest as a micro-propulsion system due to their scalability, low cost, storability, and small form factor. While VATs offer an attractive propulsion solution for CubeSats, conventional propellant feed systems used in VATs require intricate mechanical moving parts, increasing overall system complexity and mission risk. A promising alternative is the use of VAT arrays, where multiple thin-layer VATs are arranged in a regularly spaced grid, thus enhancing reliability, increasing total impulse without a mechanical propellant feed system, and enabling integrated attitude control via off-axis thruster placement. However, VAT arrays require a larger power processing unit (PPU) and additional control system, posing challenges within CubeSat volume constraints. To address this, this study proposes a novel PPU design that enables the simultaneous operation of multiple VATs while minimising system mass and volume. Experimental results demonstrate the successful operation of VAT pairs using the proposed PPU concept, validating its feasibility as an efficient propulsion solution for CubeSats. Full article

(This article belongs to the Special Issue Space Propulsion: Advances and Challenges (3rd Volume))

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17 pages, 911 KiB

Open AccessArticle

FMEA Risk Assessment Method for Aircraft Power Supply System Based on Probabilistic Language-TOPSIS

by Zicheng Xiao, Zhibo Shi and Jie Bai

Aerospace 2025, 12(6), 548; https://doi.org/10.3390/aerospace12060548 - 16 Jun 2025

Abstract

The failure mode and effect analysis (FMEA) method, which estimates the risk levels of systems or components solely based on the multiplication of simple risk rating indices, faces several limitations. These include the risk of inaccurate risk level judgment and the potential for [...] Read more.

The failure mode and effect analysis (FMEA) method, which estimates the risk levels of systems or components solely based on the multiplication of simple risk rating indices, faces several limitations. These include the risk of inaccurate risk level judgment and the potential for misjudgments due to human factors, both of which pose significant threats to the safe operation of aircraft. Therefore, a Probabilistic Language based on a cumulative prospect theory (Probabilistic Language, PL) risk assessment strategy was proposed, combining the technique for order preference with similarity to an ideal solution (TOPSIS). The probabilistic language term value and probability value were fused in the method through the cumulative prospect theory, and a new PL measure function was introduced. The comprehensive weights of evaluation strategies were determined by calculating the relevant weights of various indicators through the subjective expert weight and objective entropy weight synthesis. So, a weighted decision matrix was constructed to determine the ranking order close to the ideal scheme. Finally, the risk level of each failure mode was ranked according to its close degree to the ideal situation. Through case validation, the consistency of risk ranking was improved by 23.95% compared to the traditional FMEA method. The rationality of weight allocation was increased by 18.2%. Robustness was also enhanced to some extent. Compared with the traditional FMEA method, the proposed method has better rationality, application, and effectiveness. It can provide technical support for formulating a new generation of airworthiness documents for the risk level assessment of civil aircraft and its subsystem components. Full article

(This article belongs to the Section Aeronautics)

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29 pages, 7775 KiB

Open AccessArticle

Uncertainty Modeling of Fouling Thickness and Morphology on Compressor Blade

by Limin Gao, Panpan Tu, Guang Yang and Song Yang

Aerospace 2025, 12(6), 547; https://doi.org/10.3390/aerospace12060547 - 16 Jun 2025

Abstract

To describe the fouling characteristics of compressor blades, fouling is categorized into dense and loose layers to characterize thickness and rough structures. An uncertainty model for dense fouling layer thickness distribution is constructed using the numerical integration and the Karhunen–Loève (KL) expansion method, [...] Read more.

To describe the fouling characteristics of compressor blades, fouling is categorized into dense and loose layers to characterize thickness and rough structures. An uncertainty model for dense fouling layer thickness distribution is constructed using the numerical integration and the Karhunen–Loève (KL) expansion method, while the Fouling Longuet-Higgins (FLH) model is proposed to address the uncertainty of loose fouling layer roughness. The FLH model effectively simulates the morphology characteristics of actual blade fouling and elucidates how parameters influence fouling roughness, morphology, and randomness. Based on the uncertainty modeling method, models for dense fouling layer thickness and loose fouling layer morphology are constructed, followed by numerical calculations and aerodynamic performance uncertainty quantification. Results indicate a 75.8% probability of aerodynamic performance degradation due to a dense fouling layer and a 97.2% probability related to the morphology uncertainty of a loose fouling layer when the roughness is 50 μm. This underscores that a mere focus on roughness is inadequate for characterizing blade fouling, and a comprehensive evaluation must also incorporate the implications of rough structures on aerodynamic performance. Full article

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

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