Aerospace

30 pages, 42623 KB

Open AccessArticle

Effect of Non-Periodic Leading-Edge Wear on Aerodynamic Performance and Stall-Precursor Coherence in Centrifugal Compressor

by Hong Xie, Zhibiao Cai, Bo Yang and Chunrong Wang

Aerospace 2026, 13(7), 630; https://doi.org/10.3390/aerospace13070630 (registering DOI) - 11 Jul 2026

Abstract

Non-periodic leading-edge wear near the impeller tip is investigated with respect to the aerodynamic performance, steady flow organization, and near-stall unsteady evolution of a centrifugal compressor. A full-annulus three-dimensional impeller–vaned-diffuser model is established for a baseline configuration (O-M) and a non-periodically worn configuration [...] Read more.

Non-periodic leading-edge wear near the impeller tip is investigated with respect to the aerodynamic performance, steady flow organization, and near-stall unsteady evolution of a centrifugal compressor. A full-annulus three-dimensional impeller–vaned-diffuser model is established for a baseline configuration (O-M) and a non-periodically worn configuration (W-M). The two configurations are compared in terms of performance characteristics, near-tip pressure coefficient, static pressure, entropy, relative Mach number, three-dimensional vortical structures, and pressure fluctuation signals. The W-M generally produces a lower total pressure ratio than the O-M, with a maximum reduction of approximately 0.7%. Nevertheless, the isentropic efficiency is slightly improved over the main operating range, with a peak increase of about 0.6%, and the near-stall flow rate shifts toward a lower value. Pressure coefficient distributions at 95% span show that leading-edge wear weakens both the pressure-side pressure peak and the suction-side suction peak of the worn blades, redistributing the near-tip loading from a highly leading-edge-concentrated form to a broader chordwise distribution. The steady flow fields indicate that wear does not eliminate local low-pressure or high-entropy regions; rather, it reorganizes their circumferential arrangement, converting originally synchronized low-pressure zones, high-entropy bands, and high-speed shear layers into a non-uniform pattern with alternating strong and weak passages. Near-stall unsteady results further reveal that pressure cells, high-entropy zones, and large-scale vortical structures in the O-M exhibit clear cross-passage propagation, whereas the corresponding disturbances in the W-M remain predominantly localized, dispersed, and asynchronous. These results demonstrate that, for the wear location and blade-to-blade distribution considered here, non-periodic leading-edge wear affects stability primarily by weakening the circumferentially coherent amplification of disturbances, rather than by simply reducing all local loss sources. Full article

(This article belongs to the Section Aeronautics)

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25 pages, 3871 KB

Open AccessArticle

A Method for Detection and Three-Dimensional Localization of Spacecraft Electrostatic Discharge Events

by Kai Tang, Haojie Zhang, Xiao Sun and Xuqiang Lang

Aerospace 2026, 13(7), 629; https://doi.org/10.3390/aerospace13070629 - 10 Jul 2026

Abstract

Spacecraft electrostatic discharge (ESD) can generate transient electric-field disturbances, pulse currents, and electromagnetic coupling that threaten onboard electronics and mission reliability. Localizing discharge sources in confined spacecraft spaces remains difficult because conventional time-difference-of-arrival, radio-frequency, acoustic, and optical methods often require strict synchronization, large [...] Read more.

Spacecraft electrostatic discharge (ESD) can generate transient electric-field disturbances, pulse currents, and electromagnetic coupling that threaten onboard electronics and mission reliability. Localizing discharge sources in confined spacecraft spaces remains difficult because conventional time-difference-of-arrival, radio-frequency, acoustic, and optical methods often require strict synchronization, large arrays, suitable propagation media, line-of-sight conditions, or explicit propagation models. This study develops a spacecraft-oriented, ground-validated electrostatic-induction sensor-array framework for three-dimensional localization of transient discharge events. Different from conventional received-signal-strength-based Apollonius localization, the proposed approach uses relative transient electrostatic-induction response features, including root-mean-square value, envelope energy, and integrated energy, and calibrates their feature ratios into distance-ratio constraints using a Power + offset mapping. These calibrated constraints are interpreted as Apollonius-sphere constraints, and the source coordinate is estimated by nonlinear residual minimization without relying on high-precision arrival-time picking. The method is evaluated on a controlled one-cubic-meter confined-space laboratory platform with known sensor geometry. Ten independent test positions show centimeter-level localization accuracy in the present calibration domain. The envelope-energy representation performs best, with a mean three-dimensional error of 7.01 cm, a median error of 6.94 cm, and a maximum error of 10.05 cm. These results demonstrate the feasibility of the sensing–calibration–inversion chain as a preliminary ground-based proof of concept. The reported accuracy should not be interpreted as direct on-orbit performance because the present experiment does not include vacuum, plasma, thermal gradients, spacecraft materials, metallic enclosures, or electronics integrated for spacecraft onboard operation; further environment-specific calibration and validation are required before practical spacecraft deployment. Full article

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

22 pages, 457 KB

Open AccessArticle

Analytical Error Bounds for Lunar-Surface Relative Positioning Under Non-Identical Line-of-Sight Geometry

by Rion Sobukawa and Takuji Ebinuma

Aerospace 2026, 13(7), 628; https://doi.org/10.3390/aerospace13070628 - 10 Jul 2026

Abstract

Lunar navigation systems are being developed to support sustained surface operations, but their early deployment phase may involve limited satellite visibility and degraded accuracy in orbit and clock determination compared with terrestrial global navigation satellite systems (GNSS). Relative positioning with a lunar-surface reference [...] Read more.

Lunar navigation systems are being developed to support sustained surface operations, but their early deployment phase may involve limited satellite visibility and degraded accuracy in orbit and clock determination compared with terrestrial global navigation satellite systems (GNSS). Relative positioning with a lunar-surface reference station can mitigate common error sources through differenced measurements. In conventional GNSS, this mitigation often relies on the assumption that the line-of-sight (LOS) vectors from the reference and user receivers to the same satellite are nearly identical. Because lunar navigation satellite ranges can be considerably shorter than GNSS ranges, this approximation may be insufficient for kilometer-level surface baselines. This paper analytically quantifies three error mechanisms resulting from non-identical LOS geometries: the deterministic bias of the identical-LOS-vector approximation, the residual projection of broadcast ephemeris errors into single-differenced measurements, and the satellite-position-evaluation-time error caused by receiver clock initialization. For each mechanism, a simple closed-form bound is derived as a function of the baseline length and satellite range and is verified against time-series evaluations for representative lunar orbits. For a 10 km baseline in a low lunar orbit, the approximation alone can bias positioning by several tens of meters, whereas single differencing suppresses broadcast ephemeris errors to the meter level, and the clock-initialization effect can reach the meter level or larger. These results indicate that in lunar-surface relative positioning, the single-differenced range should be evaluated from the exact receiver-dependent geometry rather than from a common LOS vector. Additionally, the derived bounds provide a practical basis for budgeting broadcast ephemeris and receiver clock synchronization requirements. Full article

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

20 pages, 7606 KB

Open AccessArticle

A Comparative Study on Harmonic Cancellation in Dual-Generator Power Systems of More-Electric Aircraft

by Zhen Huang, Chao Wang, Yuan Gao, Hengliang Zhang, Zhan Li and Pat Wheeler

Aerospace 2026, 13(7), 627; https://doi.org/10.3390/aerospace13070627 - 10 Jul 2026

Abstract

Switching harmonics generated by power electronic converters have become a critical power quality issue in more-electric aircraft (MEA) dual-generator power systems, and accurate harmonic prediction is essential for effective harmonic cancellation. However, conventional analytical models often suffer from limited prediction accuracy, while data-driven [...] Read more.

Switching harmonics generated by power electronic converters have become a critical power quality issue in more-electric aircraft (MEA) dual-generator power systems, and accurate harmonic prediction is essential for effective harmonic cancellation. However, conventional analytical models often suffer from limited prediction accuracy, while data-driven methods are constrained by the scarcity of labeled data under certain operating conditions. This paper presents a method for harmonic prediction and cancellation in the dual-generator power systems of more-electric aircraft. To address the accumulation of switching harmonics on the DC bus, a comparative study is conducted among simplified analytical models, feedforward neural networks, and transfer learning-based models. A harmonic modeling framework and phase shift optimization strategy are established for harmonic cancellation. To overcome data limitations on the high-pressure shaft, transfer learning is employed to transfer knowledge learned from the low-pressure side to the high-pressure side. Results show that data-driven methods outperform traditional models, while transfer learning-based models further improve prediction accuracy and generalization under limited data conditions. Full article

19 pages, 9054 KB

Open AccessArticle

Graph Attention Network-Enhanced Multi-Agent Proximal Policy Optimization for Cooperative Guidance in Attack–Defense Confrontation

by Yuanli Cai and Junchao Zhao

Aerospace 2026, 13(7), 626; https://doi.org/10.3390/aerospace13070626 - 10 Jul 2026

Abstract

A graph attention network-enhanced multi-agent proximal policy optimization (GAT-MAPPO) framework is proposed for cooperative guidance in adversarial engagement scenarios. A dynamic heterogeneous interaction graph is formulated over interceptors and targets at every decision epoch. Through a multi-head graph attention encoder, relational features capturing [...] Read more.

A graph attention network-enhanced multi-agent proximal policy optimization (GAT-MAPPO) framework is proposed for cooperative guidance in adversarial engagement scenarios. A dynamic heterogeneous interaction graph is formulated over interceptors and targets at every decision epoch. Through a multi-head graph attention encoder, relational features capturing both inter-interceptor cooperation and target threat dynamics are adaptively aggregated. These graph-enriched observations are processed by a Centralized-Training, Decentralized-Execution (CTDE) MAPPO architecture, guided by a hierarchical reward function that mandates miss distance minimization, simultaneity of arrival consensus, multi-directional encirclement, and smooth control effort. Furthermore, the integration of a three-stage curriculum learning strategy allows for robust cooperative policy derivation across transitions from rectilinear to highly adaptive evasion patterns, eliminating the need for explicit rule engineering. Extensive Monte Carlo simulations confirm GAT-MAPPO’s superior performance: achieving

> 95 %

interception success rate in 4-vs.-4 scenarios and reducing mean simultaneity error by

41.4 %

compared to the MAPPO baseline. Comprehensive ablation and sensitivity studies validate the critical roles played by graph attention encoding, reward hierarchy design, and progressive curriculum staging. Full article

(This article belongs to the Special Issue New Perspective on Flight Guidance, Control and Dynamics)

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26 pages, 3458 KB

Open AccessArticle

Evaluation and Selection of Multiple k-ω Turbulence Models for Micro Electric Ducted Fans Through Experimental Validation

by Shenglun Zhang, Chuanping Tang, Hamza Blala, Youchen Wang, Zhuo Zhou and Meng Zhang

Aerospace 2026, 13(7), 625; https://doi.org/10.3390/aerospace13070625 - 9 Jul 2026

Abstract

Electric ducted fans (EDFs) have emerged as promising propulsion systems due to their compact design, high thrust density, and enhanced operational safety. Accurate prediction of aerodynamic thrust is essential for EDF design and performance evaluation; however, existing numerical studies have not yet provided [...] Read more.

Electric ducted fans (EDFs) have emerged as promising propulsion systems due to their compact design, high thrust density, and enhanced operational safety. Accurate prediction of aerodynamic thrust is essential for EDF design and performance evaluation; however, existing numerical studies have not yet provided a systematic comparison of the thrust-prediction capability of different k-ω-based turbulence models in micro-EDF applications. In this study, a dedicated thrust-measurement platform was developed for a 120 mm EDF, and experimental thrust data were obtained under three representative hover operating conditions. Based on these measurements, six turbulence models, including SST, SKω, BSL, GEKO, EARSM, and SST-γ(alg.), were evaluated using three-dimensional CFD simulations. The numerical model was assessed through thrust validation, centerline velocity comparison, power-consistency analysis, grid independence verification, and qualitative flow-field interpretation. A two-factor full-factorial analysis was further conducted to quantify the effects of rotational speed and turbulence model on prediction accuracy and computational cost. The results show that the turbulence model has a stronger influence on the normalized thrust-prediction error than the rotational speed factor over the investigated operating range. The SST-γ(alg.) model achieves the highest thrust-prediction accuracy, with an average relative deviation of 0.47%, but requires the highest computational cost. In comparison, the SST model provides a favorable balance between accuracy and efficiency, with an average relative deviation of 1.79% and an average computation time of 184.33 min, approximately 33% lower than that of the SST-γ(alg.) model. The centerline velocity and power-consistency results further support the comparative model assessment. Overall, this study provides an experimentally validated comparative reference for turbulence model selection in simulations of similar 120 mm EDF under hover conditions. Considering both prediction accuracy and computational efficiency, the SST model can serve as a practical turbulence model choice for engineering parameter optimization of similar micro-EDF configurations.

k - ω

Full article

23 pages, 7161 KB

Open AccessArticle

Design and Validation of a Compact Focusing Mechanism for Space Optical Cameras with MTF-Based Defocus Analysis

by Dou Zhang, Xiangxin Guo, Rongjia Zhang, Shengbo Zhang, Bao Zhao, Huanhuan Wu, Qifeng Li, Zhecheng Li, Long Ye, Ting Zhang and Xiaohan Liu

Aerospace 2026, 13(7), 624; https://doi.org/10.3390/aerospace13070624 - 9 Jul 2026

Abstract

A compact encoder-based focusing mechanism is proposed to compensate for axial focal-plane displacement in a space optical camera. The mechanism converts the rotation of a stepper motor into linear motion of the CCD focal plane assembly through a worm gear pair, a gear [...] Read more.

A compact encoder-based focusing mechanism is proposed to compensate for axial focal-plane displacement in a space optical camera. The mechanism converts the rotation of a stepper motor into linear motion of the CCD focal plane assembly through a worm gear pair, a gear pair, and a cylindrical cam pair, while an encoder provides position feedback for closed-loop control. A displacement-count transmission model was developed and verified through MTF simulation, positioning tests, autofocusing experiments, finite element analysis, and vibration tests. The mechanism achieved a single-step control resolution of 1.38 μm and an encoder-based displacement measurement accuracy of 0.486 μm. The positioning test showed a maximum absolute error of 7 μm within a ±2 mm travel range, satisfying the ±7.5 μm requirement. Optical simulation indicated that axial defocus broadened the PSF and reduced the MTF near the 50 lp/mm Nyquist frequency. Autofocusing experiments using a resolution target showed that the normalized stripe contrast recovered to its maximum near the best-focus position, supporting the practical image-quality recovery trend predicted by the MTF simulation. The measured first natural frequency was 174.64 Hz, and the random vibration amplification ratios were below 3 in all tested directions. The results demonstrate that the proposed mechanism can provide accurate and mechanically robust compensation of focal-plane displacement. Full article

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

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32 pages, 2656 KB

Open AccessArticle

Solid Oxide Fuel Cell Performance and Sizing Model for Novel Aircraft Propulsion Conceptual Design

by Christopher Warsch, Arturo Carboné, Philipp Maas, Florian Winter, Meriem Fikry, Arne Seitz and Mirko Hornung

Aerospace 2026, 13(7), 623; https://doi.org/10.3390/aerospace13070623 - 9 Jul 2026

Abstract

Novel aircraft propulsion concepts based on electrochemical conversion technologies, such as solid oxide fuel cells (SOFCs), are being investigated to enable climate-neutral air transport. It is crucial to identify SOFC architectures that are relevant and capable of fulfilling the specific requirements for aerospace [...] Read more.

Novel aircraft propulsion concepts based on electrochemical conversion technologies, such as solid oxide fuel cells (SOFCs), are being investigated to enable climate-neutral air transport. It is crucial to identify SOFC architectures that are relevant and capable of fulfilling the specific requirements for aerospace applications, i.e., optimization for mass and volume. For a mature design and performance synthesis of propulsion system concepts, including highly integrated SOFCs, more sophisticated component models are necessary for a clean and unified integration of SOFC technology. The models should include both electrochemical performance and sizing, as well as system integration, already at the early stages of system design and analysis. This work presents a MATLAB-based 0D approach within the Bauhaus Luftfahrt Aircraft Propulsion System Simulation (APSS) framework to model the steady-state operational characteristics of an SOFC stack and determine its preliminary size. The results serve as a basis to assess integration aspects and challenges for various SOFC architectures, such as planar or microtubular arrangements. For simulated fuel cell stacks, validation studies are performed to ensure realistic dimensioning, as well as selected analyses showing the sensitivity of the model and resulting stack size to relevant operating parameters, such as temperature or required power. The studies presented within this work are an important step towards enabling the design and subsequent evaluation of overall fuel cell-driven propulsion system concepts. Full article

(This article belongs to the Section Aeronautics)

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20 pages, 6943 KB

Open AccessArticle

Design of a Passive Sun-Pointing Mechanism for CubeSat Solar Panels

by Jaeheon Cheong, Youngho Eun and Sang-Young Park

Aerospace 2026, 13(7), 622; https://doi.org/10.3390/aerospace13070622 - 9 Jul 2026

Abstract

CubeSats operating under nadir-pointing or mission-priority attitude conditions often experience unfavorable solar incidence on their solar panels, limiting available onboard power. This study proposes a thermally driven passive sun-pointing mechanism for CubeSat solar panels and evaluates its prototype-level feasibility. The mechanism uses a [...] Read more.

CubeSats operating under nadir-pointing or mission-priority attitude conditions often experience unfavorable solar incidence on their solar panels, limiting available onboard power. This study proposes a thermally driven passive sun-pointing mechanism for CubeSat solar panels and evaluates its prototype-level feasibility. The mechanism uses a photothermal panel, heat pipe, heat cartridge, shape memory alloy (SMA) spring, and universal joint to convert external thermal input into panel tilting motion without direct electrical actuation. A prototype was evaluated through SMA spring actuation tests, single-module pointing experiments, four-direction pointing tests, orbital thermal analysis, and expected annual energy-generation analysis. The experiments showed thermally induced contraction and recovery tendency of the two-way SMA spring and demonstrated that selective thermal input can generate directional tilting and return motion in a four-direction prototype. Orbital thermal analysis indicated that heat can be transferred to the actuation region while maintaining directional thermal separation. The energy-generation analysis suggested that limited-angle pointing can improve annual energy generation compared with a fixed flat panel. These results support the prototype-level feasibility of the proposed mechanism, although further multi-axis measurement, long-term cycling, and thermal-vacuum validation are required. Full article

(This article belongs to the Special Issue Advanced Spacecraft/Satellite Technologies (2nd Edition))

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21 pages, 2516 KB

Open AccessArticle

Multi-Criteria Decision Framework for Performance Evaluation of Liquid Hydrogen Rocket Fuel Systems with Different Oxidizers

by Nadir Yilmaz, Hakan Ayhan Dağıstanlı, Alpaslan Atmanli and Michael Arowolo

Aerospace 2026, 13(7), 621; https://doi.org/10.3390/aerospace13070621 - 9 Jul 2026

Abstract

The use of liquid hydrogen (LH₂) in rocket propulsion systems is among the most critical technologies enabling highly efficient space exploration. Fuel-oxidizer combinations directly impact mission performance, safety, and sustainability. In the literature, determining which oxidizer to use to obtain an [...] Read more.

The use of liquid hydrogen (LH₂) in rocket propulsion systems is among the most critical technologies enabling highly efficient space exploration. Fuel-oxidizer combinations directly impact mission performance, safety, and sustainability. In the literature, determining which oxidizer to use to obtain an efficient combination in experimental studies is a valuable area of research. However, evaluating different alternatives according to various criteria in experimental studies is expensive, time-consuming, and quite dangerous. This study aims to provide decision-makers with analytical support through a novel multi-criteria decision-making methodology. In this context, the simple weight calculation (SIWEC) method is integrated to determine the weights of the criteria, and the mulTi-noRmalization mUlti-distance aSsessmenT (TRUST) method is integrated to evaluate the oxidizers. The results show that the most important criterion is combustion, followed by environmental sustainability, applicability, cost, and operational safety. The foremost oxidizer, according to the analyses, parametric sensitivity analysis scenarios, and comparative analyses, is overwhelmingly LH₂-liquid oxygen (LOX). In all analyses, fluorine (F₂) ranked second, followed by the FLOX mixture in third place, and ozone (O₃) in last place. In addition, sensitivity analyses based on α and β parameter variations and comparative analyses were conducted to evaluate the robustness and stability of the proposed decision-making framework. Full article

(This article belongs to the Special Issue Heat and Mass Transfer in Rocket Propulsion)

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17 pages, 845 KB

Open AccessArticle

Demand Forecasting and Inventory Optimization of Aviation Rotable Parts: A Markov Queuing Approach

by Guannan Chen, Yue Teng, Yangyang Zhang and Zhenxing Gao

Aerospace 2026, 13(7), 620; https://doi.org/10.3390/aerospace13070620 - 8 Jul 2026

Abstract

High-value aviation rotable parts require accurate demand forecasting because each failure simultaneously creates a replacement demand, a repair workload, and a potential aircraft on-ground (AOG) risk. This study develops a continuous-time Markov chain (CTMC) queuing framework for forecasting demand and optimizing target stock [...] Read more.

High-value aviation rotable parts require accurate demand forecasting because each failure simultaneously creates a replacement demand, a repair workload, and a potential aircraft on-ground (AOG) risk. This study develops a continuous-time Markov chain (CTMC) queuing framework for forecasting demand and optimizing target stock levels under realistic maintenance, repair, and overhaul (MRO) capacity constraints. Historical service-engineering records from B737 mechanical engine control (MEC) units are first benchmarked and filtered to retain inherent random failures during the useful-life phase. A Kolmogorov-Smirnov goodness-of-fit test is then used to verify the exponential time-between-failure assumption required by the Markov model. Based on this validated failure-pattern classification, the study derives steady-state probability models for both an ideal

M / M / \infty

repair system and a finite-capacity

M / M / c

repair system. The main contribution is not the isolated use of Weibull or exponential reliability models, Markov chains, or inventory optimization, which are established methods, but their auditable integration into an airline rotable-parts workflow that links failure-pattern screening, finite repair capacity, service-level constraints, and engineering validation. The empirical results show that repair bottlenecks shift probability mass toward higher numbers of failed units, create a fat-tailed backlog distribution, and double the required target stock from 6 to 12 MEC units under a 95% service-level requirement. Sensitivity experiments further show that repair turnaround time, fleet size, and MRO channel capacity jointly determine the inventory-capacity cost trade-off. The proposed framework provides an interpretable decision tool for airlines to align spare-part procurement with actual repair-system performance. Full article

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

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30 pages, 1850 KB

Open AccessArticle

On the Structure of the Optimal Guidance Policy of the Soft Landing Problem

by Leonardo Mazzini

Aerospace 2026, 13(7), 619; https://doi.org/10.3390/aerospace13070619 - 7 Jul 2026

Abstract

We revise the Soft Landing Problem deriving the Optimal Guidance Policy and the Value Function of the minimum time problem in its Controllable Set. Using this Guidance Policy the lander can be guided not only along the nominal trajectory or in its neighborhood [...] Read more.

We revise the Soft Landing Problem deriving the Optimal Guidance Policy and the Value Function of the minimum time problem in its Controllable Set. Using this Guidance Policy the lander can be guided not only along the nominal trajectory or in its neighborhood but in all conditions that can have a possible successful landing, thus providing a safer approach to changes in planning, failures or other unknown conditions. In addition to the classic solutions of this problem we have fully described a new class of broken extremals which occur when the lander is falling with an high vertical speed and can be used in case of failures or unplanned conditions. Full article

(This article belongs to the Special Issue Optimal Control in Astrodynamics)

19 pages, 9580 KB

Open AccessArticle

A Low-Complexity Real-Time Video Streaming Encryption Algorithm for Resource-Constrained LEO Satellites

by Wenyu Xu, Xiaoyuan Yang and Nanhao Liang

Aerospace 2026, 13(7), 618; https://doi.org/10.3390/aerospace13070618 - 7 Jul 2026

Abstract

Low Earth orbit (LEO) satellites are increasingly required to process and securely stream video data for remote sensing, surveillance, and onboard perception applications. However, the strict constraints of onboard computing capability, power budget, and thermal dissipation make conventional encryption schemes difficult to apply [...] Read more.

Low Earth orbit (LEO) satellites are increasingly required to process and securely stream video data for remote sensing, surveillance, and onboard perception applications. However, the strict constraints of onboard computing capability, power budget, and thermal dissipation make conventional encryption schemes difficult to apply to real-time video streaming tasks. To address this challenge, this paper proposes a low-complexity real-time video encryption algorithm for resource-constrained LEO satellites. The proposed method integrates selective encryption with a lightweight permutation–diffusion mechanism to reduce computational overhead while maintaining effective protection of continuous video streams. To enhance security, a chaotic pseudo-random sequence generator is employed to improve encryption randomness, and a dynamic key scheduling strategy is introduced to increase temporal key variability and strengthen resistance to statistical and differential attacks across successive frames. The algorithm is further designed for efficient deployment on embedded onboard platforms with limited hardware resources. Experimental results show that the proposed method achieves favorable performance in encryption speed, computational complexity, information entropy, adjacent pixel correlation, and differential attack resistance. Compared with conventional full-encryption methods, the proposed algorithm offers a more balanced trade-off between security and real-time efficiency, demonstrating its potential for secure video streaming in resource-constrained LEO satellite systems. Full article

(This article belongs to the Special Issue AI-Enabled Space Communications)

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18 pages, 5971 KB

Open AccessArticle

Experimental Investigation of VASIMR Performance Utilizing Low Magnetic Fields and Light Propellants

by Yihang Wen, Hao Chen, Xinfeng Sun, Wenjing Li, Yongxin Chen, Hai Geng and Jing Li

Aerospace 2026, 13(7), 617; https://doi.org/10.3390/aerospace13070617 - 7 Jul 2026

Abstract

As a hundred-kilowatt-class advanced electric propulsion technology, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) holds immense potential for deep space exploration. During the ion cyclotron resonance heating (ICRH) process of VASIMR, the resonance of high-mass, low-charge-state ions demands exceptionally strong background magnetic fields; [...] Read more.

As a hundred-kilowatt-class advanced electric propulsion technology, the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) holds immense potential for deep space exploration. During the ion cyclotron resonance heating (ICRH) process of VASIMR, the resonance of high-mass, low-charge-state ions demands exceptionally strong background magnetic fields; its reliance on strong magnetic fields imposes stringent thermal control requirements on superconducting magnets, significantly driving up the volume and mass penalties of the system. To address this challenge, this study explores a low-magnetic-field VASIMR architecture utilizing a light gas, Neon (Ne), as the propellant. We systematically investigate the thrust performance and the evolution of ion energy under the multivariable coupling of pre-ionization power, ICRH power, and the magnetic field topology within the resonance zone. The results demonstrate the technical and engineering feasibility of the low-magnetic-field and light-propellant propulsion scheme. Specifically, the thrust gains corresponding to the pre-ionization and ICRH power are approximately 2.2 mN/100 W and 10.3 mN/500 W, respectively. Furthermore, optimizing the magnetic field topology significantly enhances the ion energy absorption efficiency in the resonance zone, yielding a thrust improvement of 25.3 mN. This study achieves a significant reduction in the background magnetic field strength compared to conventional VASIMR, elucidating the multi-regime control mechanisms of the low-field VASIMR. These findings lay a robust theoretical and experimental basis for future lightweight designs and performance leaps. Full article

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

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29 pages, 12451 KB

Open AccessArticle

Flight Dynamics of a Hover-Capable Air-Launched Unmanned Aerial Vehicle

by Reuben-Wayne Stewart, Jack Dooher and Moble Benedict

Aerospace 2026, 13(7), 616; https://doi.org/10.3390/aerospace13070616 - 7 Jul 2026

Abstract

This paper discusses the development of a fully nonlinear flight dynamics model of a hover-capable Air-Launched Uncrewed Aerial System (ALUAS) in order to (1) understand the dynamics, controllability, and airloads during complicated maneuvers and (2) gain insights from simulation to inform the design [...] Read more.

This paper discusses the development of a fully nonlinear flight dynamics model of a hover-capable Air-Launched Uncrewed Aerial System (ALUAS) in order to (1) understand the dynamics, controllability, and airloads during complicated maneuvers and (2) gain insights from simulation to inform the design and operation of future ALUASs. Prior studies conducted wind tunnel tests on full-scale models to measure the airloads on the propeller, isolated fuselage, and full aircraft. The flight dynamics model, once corrected with the test data, was used to simulate maneuvers including hover-to-cruise transition, cruise-to-hover transition, ground launch, air launch from a moving helicopter, and air launch with asymmetric wing unfolding. These simulations demonstrate the capability of the vehicle to perform complicated maneuvers to meet various mission objectives in challenging environments. Full article

(This article belongs to the Special Issue Flight Dynamics, Control & Simulation (3rd Edition))

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19 pages, 1210 KB

Open AccessArticle

Research on Flight Stability Assessment and Real-Time Early Warning System Based on Energy Management

by Shan Ma, Wenxin Guo, Ganchao Zhao, Xiaolin Sun and Yang Yu

Aerospace 2026, 13(7), 615; https://doi.org/10.3390/aerospace13070615 - 6 Jul 2026

Abstract

Aviation accidents during the final approach phase of transport aircraft account for nearly half of all accidents in the flight stage, with unstable approaches being a notable contributing factor. In related accident analysis research, traditional single-parameter threshold monitoring methods have shown difficulty in [...] Read more.

Aviation accidents during the final approach phase of transport aircraft account for nearly half of all accidents in the flight stage, with unstable approaches being a notable contributing factor. In related accident analysis research, traditional single-parameter threshold monitoring methods have shown difficulty in capturing the complex coupling relationship between kinetic energy and potential energy. This weakness results in insufficient adaptability under variable meteorological disturbances and poor risk identification. To address this limitation, this study establishes an evaluation framework based on the concepts of “energy altitude” and “balance energy, shifting the analytical focus of aircraft state variations to energy evolution. A hybrid dynamic safety boundary function is further constructed by integrating flight mechanics principles with civil aviation regulatory constraints. This boundary integrates a height attenuation mechanism, enhancing adaptability to environmental disturbances. The study adopts QAR flight data of Boeing aircraft collected at an international airport from 2015 to 2020 as the database for machine learning modeling, and selects two additional independent flight datasets under calm-air and wind-shear conditions respectively for model verification. The research results indicate that this framework provides a robust theoretical foundation for the early identification of unstable approaches and provides actionable insights for optimizing energy control strategies, thus improving flight safety under complex operational conditions. Nevertheless, the verification only relies on two groups of typical flight cases under limited meteorological conditions, which restricts the generalizability of the research conclusions. Follow-up work will expand multi-type and multi-meteorological flight samples to carry out quantitative performance evaluation and further optimize the model’s practicality under diverse operational environments. Full article

(This article belongs to the Section Aeronautics)

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36 pages, 3209 KB

Open AccessArticle

Comparative Exergo-Economic, Exergo-Environmental, and Lifecycle Cost Analysis of High-Bypass Turbofan Engine Configurations

by Abdulrahman S. Almutairi, Hamad H. Almutairi, Abdulrahman H. Alenezi and Hamad M. Alhajeri

Aerospace 2026, 13(7), 614; https://doi.org/10.3390/aerospace13070614 - 6 Jul 2026

Abstract

Turbofan engine performance is critically sensitive to operating conditions, yet comprehensive frameworks that simultaneously assess exergo-economic, exergo-environmental, and lifecycle cost performance across realistic flight envelopes remain limited, particularly for Gulf-region climates. In this study, we present a comprehensive analysis of the exergo-economic, exergo-environmental, [...] Read more.

Turbofan engine performance is critically sensitive to operating conditions, yet comprehensive frameworks that simultaneously assess exergo-economic, exergo-environmental, and lifecycle cost performance across realistic flight envelopes remain limited, particularly for Gulf-region climates. In this study, we present a comprehensive analysis of the exergo-economic, exergo-environmental, and lifecycle costings of five different configurations of two-spool and triple-spool turbofan engines. The analysis was carried out for a wide range of four operating conditions, namely ambient temperature, flight altitude, Mach number, and % relative humidity, with emphasis on the climate conditions likely to be found in the Gulf region. The computational models developed were validated against published data to confirm their reliability. It was found that fuel consumption was the most significant contributor to total lifecycle ownership cost, between 60 and 75% of hourly operating cost over a 20-year service period. Ambient temperature, Mach number, and Cruise altitude represented the most significant drivers of long-term economic performance, with % relative humidity having little effect. Exergo-economic analysis showed that the major cost mechanisms changed dramatically with operating conditions. Exergy destruction and component inefficiencies determined the costs at Takeoff, with capital investment being the dominant factor when cruising. Increase in both or either ambient temperature and altitude was shown to reduce cost rates but simultaneously reduced thermo-economic efficiency via higher specific exergy costs. However, increase in Mach number enhances both exergy output and cost-effectiveness, confirming that specific exergy cost is a more reliable indicator of true system performance than cost rate alone. The two-spool configurations show superior specific CO₂ emissions, with Case 3 recording the lowest emissions at Takeoff and Case 2 at Cruise. For exergy-based environmental indicators, Case 3 performs best at both Takeoff and Cruise, achieving the lowest environmental destruction coefficient and index, as well as the highest environmental benign index among all five configurations. These findings provide actionable guidance for engine selection, operational optimization, and sustainable propulsion system design. Full article

(This article belongs to the Section Aeronautics)

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27 pages, 8047 KB

Open AccessArticle

Aero-Propulsive-Elastic Coupled Modeling of Distributed Electric Propulsion Systems with Slipstream Interactions

by Jun Wei, Wei Gao, Bei Lu and Qifu Li

Aerospace 2026, 13(7), 613; https://doi.org/10.3390/aerospace13070613 - 4 Jul 2026

Abstract

The distributed electric propulsion (DEP) system offers significant potential for enhancing aerodynamic efficiency, reducing emissions, and enabling innovative aerodynamic configurations. However, the strong coupling between propeller slipstream effects and wing structural dynamics presents new challenges for aeroelastic analysis. To address this issue, this [...] Read more.

The distributed electric propulsion (DEP) system offers significant potential for enhancing aerodynamic efficiency, reducing emissions, and enabling innovative aerodynamic configurations. However, the strong coupling between propeller slipstream effects and wing structural dynamics presents new challenges for aeroelastic analysis. To address this issue, this paper proposes an aeroelastic modeling approach tailored for DEP systems that systematically accounts for the effects induced by propeller slipstreams. Specifically, the induced velocity generated by the propeller slipstreams is computed using a slipstream tube model and incorporated into the unsteady aerodynamic modeling via the unsteady vortex lattice method. Under appropriate assumptions, a state-space formulation of the unsteady aerodynamic forces is derived, while the wing structural dynamics are represented using the finite element method. After establishing the subsystem models, a complete aeroelastic model of the DEP system is assembled based on the input–output relationships among the subsystems. Nonlinear simulations are conducted using this integrated model. The results demonstrate the potential of distributed propellers for suppressing wing vibrations and alleviating structural loads. Full article

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

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26 pages, 20159 KB

Open AccessArticle

A Two-Dimensional Sequential Packing Method for Lunar Regolith Particles Based on Random Polygons

by Chunguang Zhang, Feng Sun, Ye Li, Haining Zhao, Fangchao Xu, Junyue Tang, Shengyuan Jiang, Chuan Zhao and Ran Zhou

Aerospace 2026, 13(7), 612; https://doi.org/10.3390/aerospace13070612 - 4 Jul 2026

Abstract

To accurately characterize the effects of polydisperse particle sizes, multimineral composition, and angular morphology on the packing structure of lunar regolith, a two-dimensional sequential packing method based on random convex octagons is proposed. The method establishes a particle parameter system using data from [...] Read more.

To accurately characterize the effects of polydisperse particle sizes, multimineral composition, and angular morphology on the packing structure of lunar regolith, a two-dimensional sequential packing method based on random convex octagons is proposed. The method establishes a particle parameter system using data from Chang’e-5 samples and generates polygonal particle models with controllable angular features through radial perturbation. On this basis, a sequential packing algorithm based on available arc analysis is developed. Non-overlapping particle insertion is achieved via geometric envelope constraints, and progressive filling is realized through effective arc sampling. Meanwhile, a packing control coefficient is introduced to enable continuous regulation of packing density. Results show that the proposed method can generate highly dense particle assemblies, with a maximum packing density of 0.8757 and an average coordination number of approximately 3.18, capturing the structural characteristics of “high compactness–low coordination number” in polydisperse angular particle systems. The algorithm exhibits a computational complexity of O(N^1.628), demonstrating high efficiency. Furthermore, contact area and contact strength are quantitatively characterized through contact contour extraction and an equivalent bow-shaped model. Radial distribution function and contact statistics indicate that the generated structures possess good randomness and physical consistency. The proposed method provides a high-fidelity mesoscopic structure generation approach for discrete element modeling (DEM) of lunar regolith and establishes a reliable foundation for analyzing the mechanical behavior of granular systems. Full article

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

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