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Experimental Investigation of Hydrogen Peroxide and Nitrous Oxide in a 1-Newton Catalyst-Based Monopropellant Research Thruster
Penetrating Radar on Unmanned Aerial Vehicle for the Inspection of Civilian Infrastructure: System Design, Modeling, and Analysis
Lunar Robotic Construction with Raw Regolith
A Review of Advancements for Spacecraft On-Orbit Servicing, Assembly, and Manufacturing (OSAM) Technologies

Journal Description

Aerospace

Aerospace is a peer-reviewed, open access journal of aeronautics and astronautics, published monthly online by MDPI. The European Aerospace Science Network (EASN) and ECATS International Association are affiliated with Aerospace and their members receive a discount on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, Ei Compendex, and other databases.
Journal Rank: JCR - Q2 (Engineering, Aerospace) / CiteScore - Q2 (Aerospace Engineering)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 20.9 days after submission; acceptance to publication is undertaken in 2.5 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Companion journal: Astronomy.
Journal Cluster of Mechanical Manufacturing and Automation Control: Aerospace, Automation, Drones, Journal of Manufacturing and Materials Processing, Machines, Robotics and Technologies.

Impact Factor: 2.2 (2024); 5-Year Impact Factor: 2.4 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2226-4310

Latest Articles

55 pages, 6682 KB

Open AccessReview

Trajectory Optimization for Orbit Transfers: Principles, Advances, Case Studies, and Outlook

by Katherine Vasiloff, Israel Adesina, Zhenbo Wang, Kshitij Mall and Daniel A. DeLaurentis

Aerospace 2025, 12(12), 1087; https://doi.org/10.3390/aerospace12121087 (registering DOI) - 6 Dec 2025

This review presents an in-depth exploration of trajectory optimization techniques for various orbit transfer applications, focusing on principles, methodologies, and practical case studies. The emphasis is placed on indirect, direct, and data-driven trajectory optimization methods powered by numerical, deterministic, and gradient-based optimization algorithms, [...] Read more.

This review presents an in-depth exploration of trajectory optimization techniques for various orbit transfer applications, focusing on principles, methodologies, and practical case studies. The emphasis is placed on indirect, direct, and data-driven trajectory optimization methods powered by numerical, deterministic, and gradient-based optimization algorithms, and an overview on the basic fundamentals of each method is provided. Applications cover numerous orbit transfer problems, from geocentric and interplanetary transfers to other orbital maneuvers that are applicable to the orbit transfer problem, highlighting critical advancements of trajectory optimization techniques in enabling more efficient and feasible space missions. A minimum-fuel transfer from Earth to Mars is considered as a case study and solved using the indirect, direct, and data-driven methods, respectively, demonstrating an effective primer on the implementation of each method. Finally, we identify open challenges and issues, discuss potential opportunities, and make suggestions for future research directions. By synthesizing current methods and emerging trends, this review provides a comprehensive toolkit for addressing complex challenges in orbit transfers. Full article

(This article belongs to the Special Issue Spacecraft Orbit Transfers (2nd Edition))

18 pages, 5019 KB

Open AccessArticle

Multi-Step Prediction of Airborne Load Separation Trajectory and Attitude Based on RCF-Transformer

by Xin Zheng, Xutong Zhang, Xue Zhang and Jingjie Li

Aerospace 2025, 12(12), 1086; https://doi.org/10.3390/aerospace12121086 - 4 Dec 2025

Accurate and efficient data-driven prediction of embedded airborne load separation trajectories and attitudes can not only significantly improve the safety of the separation process but also substantially reduce reliance on costly aerodynamic simulations and wind tunnel testing. This paper proposes a real-time condition [...] Read more.

Accurate and efficient data-driven prediction of embedded airborne load separation trajectories and attitudes can not only significantly improve the safety of the separation process but also substantially reduce reliance on costly aerodynamic simulations and wind tunnel testing. This paper proposes a real-time condition fusion Transformer (RCF-Transformer) model for predicting the trajectory and attitude after load separation. Using wind-tunnel datasets of separation events obtained from Captive Trajectory Simulation (CTS), the model encodes historical sequence information while dynamically injecting real-time input conditions measured at the moment of separation into the decoder. Masked multi-head self-attention and cross-attention mechanisms are employed for collaborative learning, enabling multi-step, multi-output prediction of three-axis position and attitude. Experimental results show that, for a multi-step prediction horizon of up to

T = 5

, the proposed model achieves an overall prediction accuracy of 95.28%. Furthermore, error-structure analyses based on Theil’s inequality coefficient decomposition, confidence intervals, and F-tests of residual variances demonstrate that the residuals are dominated by nonsystematic, high-frequency fluctuations and that the performance gains over the strongest baseline are statistically significant. These results indicate that the proposed method is highly stable and robust, providing an efficient and scalable data-driven solution for safety monitoring and decision support during the initial separation of airborne loads. Full article

(This article belongs to the Special Issue Advanced AI and Robotic Technologies for Spacecraft Modelling, Optimization, and Decision-Making)

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14 pages, 942 KB

Open AccessArticle

Conceptual Design of a Hybrid-Electric Aircraft Based on a Dornier 328 Demonstrator

by Annika Nora Staats, Florian Troeltsch and Andreas Bardenhagen

Aerospace 2025, 12(12), 1085; https://doi.org/10.3390/aerospace12121085 - 4 Dec 2025

Air travel contributed 3.5% to global warming in 2020, with a rising tendency. Only one third of the climate impact is caused by CO

_{2}

. Other exhaust gases that cause harm to the climate are nitrogen oxides, soot, and water vapor, creating [...] Read more.

Air travel contributed 3.5% to global warming in 2020, with a rising tendency. Only one third of the climate impact is caused by CO

_{2}

. Other exhaust gases that cause harm to the climate are nitrogen oxides, soot, and water vapor, creating contrails with a negative impact on earth’s albedo. Hence, it is important to reduce any type of emission. As the effects of global climate change become an unneglectable threat to society, calls for quick changes become prominent. Recognizing the need for disruptive changes in air transport, the LuFo-project 328eHY-TECH was initiated to investigate the potential of regional hybrid-electric aircraft. This article focuses on conceptual aircraft design. An aircraft resembling the D328eco is modeled as a baseline aircraft, on which the sizing of the hybrid-electric propulsion systems is performed. As aircraft are mostly operated on a typical mission, which is shorter than the design mission, a distance of 400 nm is found to be a feasible range for this regional aircraft. In a conducted range study, the potential of state-of-the-art battery properties is being investigated and found to be insufficient. Subsequently conducted trade-off studies show that a 104 kW horsepower electric motor and a battery of 1.8 kWh/kg are needed to save 5% block fuel on a mission with 40 passengers of 95 kg over a distance of 400 nm. It is concluded that changing solely the propulsion system will not yield feasible aircraft designs in the near and midterm future. Full article

(This article belongs to the Section Aeronautics)

21 pages, 840 KB

Open AccessArticle

Impact of Solar Irradiance on Low-Earth-Orbit Satellite Orbital Decay During Geomagnetic Storm

by Haiquan Yu, Lue Chen and Bo Chen

Aerospace 2025, 12(12), 1084; https://doi.org/10.3390/aerospace12121084 - 4 Dec 2025

In recent years, with the rapid expansion of low-Earth-orbit (LEO) satellite constellations, the orbital decay of LEO satellites caused by atmospheric heating from solar irradiance and geomagnetic activity has become increasingly prominent. Accurately understanding the orbital decay behavior of LEO satellites during geomagnetic [...] Read more.

In recent years, with the rapid expansion of low-Earth-orbit (LEO) satellite constellations, the orbital decay of LEO satellites caused by atmospheric heating from solar irradiance and geomagnetic activity has become increasingly prominent. Accurately understanding the orbital decay behavior of LEO satellites during geomagnetic storms is essential for managing orbital lifetime, orbit determination, orbit control, and collision risk assessment. This study investigates the combined effects of solar radiation intensity and geomagnetic storm intensity on LEO satellite orbital decay by analyzing 130 representative intense geomagnetic storms from 1965 to 2025. The results demonstrate that during geomagnetic storms, both solar irradiance and geomagnetic activity jointly influence orbital decay: solar irradiance primarily determines the total decay magnitude, while geomagnetic activity mainly affects short-term decay rates through transient disturbances. Furthermore, solar radiation intensity shows a stronger correlation with orbital decay than storm intensity. Therefore, effective orbit maintenance strategies for LEO satellites should emphasize the influence of solar radiation intensity in addition to geomagnetic storm intensity. Our findings provide valuable references for developing operational orbit maintenance protocols for LEO satellites during space weather events. Full article

(This article belongs to the Special Issue Dynamics and Control of Space On-Orbit Operations)

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20 pages, 8312 KB

Open AccessArticle

Pre-Tensioned Flexible Skins for Large-Folding-Ratio UAV Wings: Theory and Tests

by Guang Yang, Lunjiang Zhao, Yuqi Li, Hong Xiao and Hongwei Guo

Aerospace 2025, 12(12), 1083; https://doi.org/10.3390/aerospace12121083 - 4 Dec 2025

This paper proposes a hybrid rigid–flexible wing design that enables large-area folding and reconfiguration. Based on elasticity theory and fabric constitutive equations, a surface-outward mechanical model incorporating mesoscale weave structures was developed for plain-woven wing membranes. To address the degradation of the model [...] Read more.

This paper proposes a hybrid rigid–flexible wing design that enables large-area folding and reconfiguration. Based on elasticity theory and fabric constitutive equations, a surface-outward mechanical model incorporating mesoscale weave structures was developed for plain-woven wing membranes. To address the degradation of the model under low-prestress conditions, a more accurate second-order nonlinear model for the out-of-plane mechanics of wing membranes was further developed. This paper developed a dual-axis tensile fixture and, through conducting load-bearing performance experiments on wing membrane elements, verified that the improved theoretical model possesses a certain degree of predictive accuracy. A dual-axis tensile fixture was designed, and load-bearing tests on membrane elements were conducted to verify that the improved theoretical model provides reasonable predictive accuracy. To investigate how pre-tensioning regulates membrane stiffness, the variation in out-of-plane stiffness under symmetric and asymmetric prestress conditions was analysed. A prestressing strategy prioritising the principal-modulus direction is proposed, providing theoretical guidance for prestress application in wing membranes. Based on these findings, a prototype rigid–flexible composite wing with a “membrane-scaffold” structure was fabricated and tested. Full article

(This article belongs to the Section Aeronautics)

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26 pages, 1045 KB

Open AccessArticle

Enhanced Evaluation Model on Emergency Response Effectiveness at Civil Airports: A Theoretical and Empirical Study

by Hao Sun, Pei Zhu, Jiahe Miao, Lin Wang, Tao Wang, Lizhi Fang, Hongxia Dou and Wenfei Yu

Aerospace 2025, 12(12), 1082; https://doi.org/10.3390/aerospace12121082 - 4 Dec 2025

The Civil Aviation Administration of China mandates comprehensive evaluations of emergency response effectiveness. However, existing studies predominantly focus on evaluating response capabilities rather than actual effectiveness. This leads to evaluation results deviating from reality. Other studies evaluating response effectiveness are mostly limited by [...] Read more.

The Civil Aviation Administration of China mandates comprehensive evaluations of emergency response effectiveness. However, existing studies predominantly focus on evaluating response capabilities rather than actual effectiveness. This leads to evaluation results deviating from reality. Other studies evaluating response effectiveness are mostly limited by incomplete indicator systems and flawed algorithms. To address the questions, this study takes runway unsafe events as the study subject, focuses on evaluating response effectiveness, examines common evaluation methodologies, identifies critical gaps in indicator systems, and discusses traditional algorithmic vulnerabilities. Utilizing the Delphi method and fuzzy Analytic Hierarchy Process, this study establishes a four-tier indicator system encompassing evaluation objectives, phases, processes, and elements and proposes an optimized model incorporating scoring criteria, indicator weights, and correction coefficients designed to mitigate inherent algorithmic vulnerabilities prevalent in traditional methodologies. Finally, two simulation verifications based on real incidents demonstrate that the model of emergency response effectiveness at civil airports has a notable improvement in evaluation accuracy. Full article

(This article belongs to the Special Issue Next-Generation Airport Operations and Management)

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22 pages, 2078 KB

Open AccessArticle

A Multi-Modal Fusion Algorithm for Space Target Recognition Based on Spatial Attention and Multi-Scale Temporal Network

by Xiaoyu Cong, Yubing Han, Cheng Chen and Shichen Shan

Aerospace 2025, 12(12), 1081; https://doi.org/10.3390/aerospace12121081 - 4 Dec 2025

When fusing inverse synthetic aperture radar (ISAR) images and high-resolution range profile (HRRP), the significant heterogeneity existing between the feature spaces of the two is not adequately considered, resulting in a low accuracy rate of space target recognition. A multi-modal fusion algorithm based [...] Read more.

When fusing inverse synthetic aperture radar (ISAR) images and high-resolution range profile (HRRP), the significant heterogeneity existing between the feature spaces of the two is not adequately considered, resulting in a low accuracy rate of space target recognition. A multi-modal fusion algorithm based on spatial attention and multi-scale temporal network is proposed in this paper. We carefully consider the data characteristics of HRRP and ISAR and design feature extraction networks, respectively. For HRRP, the local invariant features are extracted using dynamic convolution (DyConv), and the convolution depth is reduced. An improved multi-scale temporal convolution network is designed based on the temporal characteristics of HRRP to extract temporal features for target recognition. For ISAR images, an omnidirectional attention feature extraction module is designed to extract the deep semantic features of the images, and a noise reduction module with a spatial attention mechanism is designed before extracting the image features to reduce the background noise in the fused image. The superiority of the designed ISAR recognition network and HRRP recognition network for space target was verified through comparative and ablation experiments. The recognition rate for the target of the proposed algorithm is 98.41%. Full article

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

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9 pages, 223 KB

Open AccessEditorial

Perspectives and Trends in Flight Dynamics and Simulation

by Karim Abu Salem

Aerospace 2025, 12(12), 1080; https://doi.org/10.3390/aerospace12121080 - 4 Dec 2025

In today’s aeronautical sciences, flight mechanics, flight dynamics, and simulation form a fundamental disciplinary and methodological core that enables us to interpret, anticipate, and drive innovation in the field [...] Full article

(This article belongs to the Special Issue Flight Dynamics, Control & Simulation (2nd Edition))

29 pages, 1476 KB

Open AccessArticle

A Spatio-Temporally Cooperative Guidance Law for Highly Maneuverable Target

by Jia Liu, Yang Guo, Shaobo Wang, Shiyuan Zhang, Jimao Sang and Chengyi Zhang

Aerospace 2025, 12(12), 1079; https://doi.org/10.3390/aerospace12121079 - 4 Dec 2025

Conventional guidance laws often exhibit difficulty in approaching highly maneuverable targets and suffer from poor robustness. To address these limitations, this paper proposes a spatio-temporally consistent cooperative guidance method based on the fully actuated system (FAS) approach. First, a cooperative guidance model incorporating [...] Read more.

Conventional guidance laws often exhibit difficulty in approaching highly maneuverable targets and suffer from poor robustness. To address these limitations, this paper proposes a spatio-temporally consistent cooperative guidance method based on the fully actuated system (FAS) approach. First, a cooperative guidance model incorporating the approaching-time and approaching-angle constraints is established based on kinematic and dynamic equations, subsequently transformed into an FAS formulation. Second, leveraging the backstepping design, a sliding-mode-like guidance law and an event-triggered control barrier function optimization method are designed within the FAS framework. Specifically, cooperative guidance laws are developed for the line-of-sight (LOS) radial and normal directions, respectively, tailored for approaching a highly maneuverable target. The consistent convergence properties of the proposed method are rigorously proven theoretically. Finally, the effectiveness of the proposed guidance scheme is validated through comprehensive numerical simulations. Full article

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18 pages, 2962 KB

Open AccessArticle

Benefits from Thin-Ply Composite Materials in Aircraft Wing Structures

by Lennart Lobitz, Christian Bülow, Sebastian Heimbs and Peter Horst

Aerospace 2025, 12(12), 1078; https://doi.org/10.3390/aerospace12121078 - 3 Dec 2025

Previous research shows that thin-ply composite materials offer superior static and fatigue characteristics to standard laminates used in aviation. Therefore, they are expected to be capable of significantly contributing to a mass reduction needed to improve the energy-efficiency of future aircraft. However, so [...] Read more.

Previous research shows that thin-ply composite materials offer superior static and fatigue characteristics to standard laminates used in aviation. Therefore, they are expected to be capable of significantly contributing to a mass reduction needed to improve the energy-efficiency of future aircraft. However, so far, thin-ply composites have only been employed in special applications. Quantitative full-scale assessments of the benefits on the level of global aircraft structures are missing. This study employs a parametric, finite element-based tool chain with a fully-stressed design methodology to investigate potential benefits from the use of thin plies, which may result from increased strength, an extended design freedom and stability considerations, in a generic wing structure of a conceptual medium-range aircraft in order to reduce this research gap. The methodology is validated using an academic test case. Naturally, mass reductions from strength enhancements are limited by buckling constraints in thin-walled structures. However, for the wing examined in this study, an increase in strength of 10 still yields up to a 7.9 reduction in global wing mass, while an increase of 20 results in mass savings of up to 13.4. The use of thin-ply composites may allow for reducing minimum wall thickness constraints. Associated mass savings of up to 3.1 found in this study on global wing level when alleviating the requirement from 2.4

m

m

to 1.2

m

m

are, however, restricted to rib mass and may better be achieved by different means such as topology optimisation. In contrast, mass penalties from the application of a simplified manufacturing constraint are reduced significantly from beyond 10 on global wing level for plies with a thickness of 0.175

m

m

to approximately 1.5 with a ply thickness of 0.05

m

m

. Full article

(This article belongs to the Special Issue Composite Materials and Aircraft Structural Design)

31 pages, 2446 KB

Open AccessArticle

An Approach for Spacecraft Operational Task Scheduling Considering Constrained Space–Ground TT&C Resources and Task Splitting

by Jianqiang Tang, Yueyi Hou, Shan Wu, Zhaokai Si, Jin Xu and Chao Qi

Aerospace 2025, 12(12), 1077; https://doi.org/10.3390/aerospace12121077 - 3 Dec 2025

This paper proposes a scheduling approach for multi-type spacecraft operational tasks that can be interleaved, considering constrained space–ground telemetry, tracking, and command (TT&C) resources, as well as task splitting. A mixed-integer linear programming model is formulated to maximize the total task completion reward [...] Read more.

This paper proposes a scheduling approach for multi-type spacecraft operational tasks that can be interleaved, considering constrained space–ground telemetry, tracking, and command (TT&C) resources, as well as task splitting. A mixed-integer linear programming model is formulated to maximize the total task completion reward under service time-window constraints for splittable and unsplittable routine tasks, continuous tracking requirements, coupling relationships between routine and continuous tracking tasks, temporal logic dependencies, visibility constraints, and non-overlapping scheduling conditions. To improve solution efficiency and scheduling performance, a heuristic algorithm that combines priority rules with partial backtracking is developed. Task priorities are determined based on completion rewards, due times, execution durations, and temporal relationships, and scheduling is refined to avoid conflicts with predefined constraints. A partial backtracking mechanism guided by task release times enables effective adjustment when TT&C requirements cannot be satisfied. Comparative experiments with CPLEX and four heuristic algorithms validate the effectiveness of the proposed method. Full article

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

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27 pages, 5009 KB

Open AccessArticle

From Potential Routes to Climate Impact: Assessing the Fleet Transition to Hydrogen-Powered Aircraft

by Gabriele Sirtori and Lorenzo Trainelli

Aerospace 2025, 12(12), 1075; https://doi.org/10.3390/aerospace12121075 - 1 Dec 2025

The paper presents a methodology aiming to assess the impact of operations of a short- and medium-range fleet transitioning from jet fuel to hydrogen propulsion, considering the constraint arising from the distribution of hydrogen refueling infrastructures across airports, leveraging on the different performance [...] Read more.

The paper presents a methodology aiming to assess the impact of operations of a short- and medium-range fleet transitioning from jet fuel to hydrogen propulsion, considering the constraint arising from the distribution of hydrogen refueling infrastructures across airports, leveraging on the different performance of the two sub-fleets to obtain the least climate-impacting transition. Hydrogen tankering will enable flights to airports that have no hydrogen refueling capabilities, as long as the destination is within half of the operational range of the selected aircraft, at the cost of a slight increase in fuel burn. The proposed methodology aims to assess said increase, while minimizing the expenditure for hydrogen, and the coverage of a reference network, achievable when considering aircraft performance and assumptions on the availability and cost of hydrogen at various airports. The results of such analysis can be used to determine whether a reduction in the design range of a given aircraft is acceptable. Such a reduction would mitigate the impact that the hydrogen tank has on the sizing of the aircraft and its performance. Depending on the considered scenario, a network potential coverage spanning from 81% to 96% can be achieved. Starting from this result, it is possible to assess the transition of a short-haul airliner fleet from jet fuel to hydrogen propulsion, considering the constraint arising from the distribution of hydrogen refueling infrastructures across airports and the different performances (energetic, environmental and economic) of the two sub-fleets. The aircraft assignment to each route is performed with the objective of minimizing either the energy, the carbon intensity or the fuel cost of the overall network, obtaining different route assignment distributions. The results show that the aviation-induced temperature change can be reduced by up to 57% compared to an all-jet-fuel fleet. Full article

(This article belongs to the Special Issue Multidisciplinary Design Optimization for Climate-Neutral Transport Aviation)

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19 pages, 2192 KB

Open AccessArticle

Path Optimization Algorithm for Airborne TSN Using Augmented Lagrangian and Bayesian Reliability Modelling

by Zhiming Zheng, Jizhou Lai, Jianfeng Miao, Chun Cheng, Chen Chen and Bo Gao

Aerospace 2025, 12(12), 1074; https://doi.org/10.3390/aerospace12121074 - 30 Nov 2025

With the rapid development of the civil aviation industry, the reliability and real-time performance of airborne data transmission are becoming increasingly important. The traditional airborne network cannot meet the future flight requirements of the aircraft. To ensure the reliable and real-time transmission of [...] Read more.

With the rapid development of the civil aviation industry, the reliability and real-time performance of airborne data transmission are becoming increasingly important. The traditional airborne network cannot meet the future flight requirements of the aircraft. To ensure the reliable and real-time transmission of data, the time-sensitive network introduces the Frame Replication and Elimination for Reliability (FRER) mechanism. The standard FRER mechanism defines the methods of frame replication and elimination of redundant frames. However, the description of how the replicated frames are transmitted is not in-depth. The frame replication and elimination function at the source and destination nodes will also reduce the reliability and real-time performance of the network. In order to realize the application of the time-sensitive network in the airborne network, this article independently builds an airborne time-sensitive network test simulation platform. It carries out in-depth research on improving the reliability of the network. It puts forward a path-finding algorithm based on a time-sensitive network with the FRER mechanism in response to the problem of low reliability of the selected data transmission paths in the airborne network. The algorithm integrates the constraints of transmission link delay and packet loss rate. It performs link reliability calculation before selecting redundant paths to obtain non-overlapping data transmission paths. The experimental results show that, compared with the dynamic link redundancy selection algorithm, the path delay is reduced by 21.51%. Compared with the multilevel P-cycle cascading algorithm, the path delay is reduced by 19.70%. At a 120 Mbps data transmission rate, the packet loss rate is reduced by 18.67% compared with the dynamic link redundancy selection algorithm. It is also reduced by 24.00% compared with the multilevel P-cycle cascading algorithm. These results show that the proposed method improves the reliability of data transmission in the airborne network. Full article

(This article belongs to the Section Aeronautics)

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29 pages, 4213 KB

Open AccessArticle

Extended Necessary Conditions for Multi-Arc Aerospace Trajectory Optimization

by Mauro Pontani

Aerospace 2025, 12(12), 1073; https://doi.org/10.3390/aerospace12121073 - 30 Nov 2025

A variety of aerospace trajectory optimization problems are subject to either discontinuities or constraints at intermediate times, which define multiple arcs with distinctive governing equations. This work addresses multi-arc optimal control problems, with special interest regarding aerospace trajectories, and specifically focuses on the [...] Read more.

A variety of aerospace trajectory optimization problems are subject to either discontinuities or constraints at intermediate times, which define multiple arcs with distinctive governing equations. This work addresses multi-arc optimal control problems, with special interest regarding aerospace trajectories, and specifically focuses on the multipoint corner conditions that belong to the complete set of necessary conditions for an extremal, in the context of a general formulation. This includes intermediate times and states in the objective functional, together with unknown time-independent parameters. This study shows that 16 cases can occur for the multipoint corner conditions and groups them into three classes. Explicit, closed-form solutions of the multipoint corner relations are identified in each class, if certain conditions are met. In an indirect solution approach, these explicit expressions can be employed sequentially, thus reducing the number of unknowns of multi-arc problems to the same number of single-arc optimal control problems. This is extremely useful in the presence of a large number of arcs. Two challenging aerospace trajectory optimization problems are analyzed as illustrative examples, i.e., (i) the minimum-fuel ascent path of a multistage launch vehicle and (ii) minimum-time low-thrust orbit transfers with eclipse constraints on the available thrust. Full article

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

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23 pages, 3344 KB

Open AccessArticle

Simulation and Design of a CubeSat-Compatible X-Ray Photovoltaic Payload Using Timepix3 Sensors

by Ashraf Farahat, Juan Carlos Martinez Oliveros and Stuart D. Bale

Aerospace 2025, 12(12), 1072; https://doi.org/10.3390/aerospace12121072 - 30 Nov 2025

This study investigates the use of Si and CdTe-based Timepix3 detectors for photovoltaic energy conversion using solar X-rays and other high-energy electromagnetic radiation in space. As space missions increasingly rely on miniaturized platforms like CubeSats, power generation in compact and radiation-prone environments remains [...] Read more.

This study investigates the use of Si and CdTe-based Timepix3 detectors for photovoltaic energy conversion using solar X-rays and other high-energy electromagnetic radiation in space. As space missions increasingly rely on miniaturized platforms like CubeSats, power generation in compact and radiation-prone environments remains a critical challenge. Conventional solar panels are limited by size and spectral sensitivity, prompting the need for alternative energy harvesting solutions—particularly in the high-energy X-ray domain. A novel CubeSat-compatible payload design incorporates a UV-visible filter to isolate incoming X-rays, which are then absorbed by semiconductor detectors to generate electric current through ionization. Laboratory calibration was performed using Fe-55, Ba-133, and Am-241 sources to compare spectral response and clustering behaviour. CdTe consistently outperformed Si in detection efficiency, spectral resolution, and cluster density due to its higher atomic number and material density. Equalization techniques further improved pixel threshold uniformity, enhancing spectroscopic reliability. In addition to experimental validation, simulations were conducted to quantify the expected energy conversion performance under orbital conditions. Under quiet-Sun conditions at 500 km LEO, CdTe absorbed up to 1.59 µW/cm² compared to 0.69 µW/cm² for Si, with spectral power density peaking between 10 and 20 keV. The photon absorption efficiency curves confirmed CdTe’s superior stopping power across the 1–100 keV range. Under solar flare conditions, absorbed power increased dramatically, up to 159 µW/cm² for X-class and 15.9 µW/cm² for C-class flares with CdTe sensors. A time-based energy model showed that a 10 min X-class flare could yield nearly 1 mJ/cm² of harvested energy. These results validate the concept of a compact photovoltaic payload capable of converting high-energy solar radiation into electrical power, with dual-use potential for both energy harvesting and radiation monitoring aboard small satellite platforms. Full article

(This article belongs to the Special Issue Small Satellite Missions (2nd Edition))

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27 pages, 5514 KB

Open AccessArticle

Multi-Channel Structural–Semantic Fusion for Forecasting Air Traffic Control Incidents: Implications for Proactive Air Traffic Safety Management

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

Aerospace 2025, 12(12), 1071; https://doi.org/10.3390/aerospace12121071 - 30 Nov 2025

Effective safety management in air traffic is essential for operational reliability and risk reduction. We propose a multi-channel fusion framework to predict intervals between consecutive air traffic incidents by combining structural, semantic, and temporal information. Inter-incident time series are transformed into complex networks [...] Read more.

Effective safety management in air traffic is essential for operational reliability and risk reduction. We propose a multi-channel fusion framework to predict intervals between consecutive air traffic incidents by combining structural, semantic, and temporal information. Inter-incident time series are transformed into complex networks via visibility graphs to learn node embeddings capturing structural recurrence. Semantic features are derived through latent Dirichlet allocation (LDA) and bidirectional encoder representations from Transformers (BERT) embeddings to reveal latent risk-related topics, and an adaptive spectral filter enhances temporal features. These are processed through three modules: a gravity-inspired visibility graph model (GVG), a semantic-aware LSTM (Sem-LSTM), and a spectral-enhanced temporal convolutional network (Spec-TCN). An attention mechanism fuses all modules to predict incident intervals. Using 1298 real-world incidents from China’s Central and Southern Region for validation, the model achieves a mean absolute error of 1.42 h and sMAPE of 17.5%. SHAP analysis indicates that structural similarity and incident topics jointly drive prediction. By integrating interval predictions with topic cues, we construct a safety management framework enabling proactive decision-making. This framework delivers a practical bridge from interval predictions to proactive air traffic control (ATC) decisions. Full article

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

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15 pages, 7025 KB

Open AccessArticle

An Impact Strain Monitoring and Simulating Method for Large-Size Composite Skin Panel with Optical Fiber Sensors

by Jianfei Feng, Hao Dong, Kang Cao and Yongjie Zhang

Aerospace 2025, 12(12), 1070; https://doi.org/10.3390/aerospace12121070 - 30 Nov 2025

Structural Health Monitoring (SHM) is now essential for certifying many composite primary structures as it resolves strain redistribution at the moment of impact. Traditional detection methods, including resistive strain gauges, face challenges due to susceptibility to electromagnetic noise, as well as increased mass [...] Read more.

Structural Health Monitoring (SHM) is now essential for certifying many composite primary structures as it resolves strain redistribution at the moment of impact. Traditional detection methods, including resistive strain gauges, face challenges due to susceptibility to electromagnetic noise, as well as increased mass and wiring complexity proportional to the number of channels. This study proposes an impact strain monitoring and simulating method using optical fiber sensors for composite skin panels. Repeated low-velocity impact tests were conducted on large-size composite skin panels using various impact forces and locations. The 95% confidence interval for unit load strain in the simulation results differs from the experiment by 18%. This method effectively facilitates the monitoring of global impact strain on large-size composite skin panels. Full article

(This article belongs to the Section Aeronautics)

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23 pages, 1309 KB

Open AccessArticle

Preliminary Proof of the Feasibility of a Novel Mission Concept and Spacecraft Trajectory for Exploring Uranus with Small Satellites

by Dylan Barnes and Paula do Vale Pereira

Aerospace 2025, 12(12), 1069; https://doi.org/10.3390/aerospace12121069 - 30 Nov 2025

Following recommendations from the 2023–2032 Planetary Science and Astrobiology Decadal Survey, we propose a novel Uranus exploration mission that is centered on using constellations of small spacecraft to observe the Uranus system. Using the method of patched conics and system-level design, we present [...] Read more.

Following recommendations from the 2023–2032 Planetary Science and Astrobiology Decadal Survey, we propose a novel Uranus exploration mission that is centered on using constellations of small spacecraft to observe the Uranus system. Using the method of patched conics and system-level design, we present a Pre-Phase A mission concept to launch a 4500 kg spacecraft on a Jupiter–Uranus gravity assist transfer trajectory with a transfer time of six years, having the spacecraft arrive at Uranus in 2039 after launching in 2033. To maintain the quality of data collection while minimizing mass, we propose that the spacecraft will be composed of a carrier spacecraft with a 3848 kg wet mass, which would be used primarily for communications and orbital transfers, and a constellation of CubeSats with a combined wet mass of 640 kg, which would house the instrumentation. In this paper, we discuss the feasibility of the proposed mission concept and we demonstrate that a CubeSat constellation mission to Uranus can be not only viable but also a fuel and cruise time optimization opportunity, delivering 16 exploration spacecraft to Uranus in six years. Full article

(This article belongs to the Special Issue Spacecraft Trajectory Design)

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29 pages, 3005 KB

Open AccessArticle

ISWO-LADRC: Improved Spider Wasp Optimization Algorithm-Based Rotational Speed Control for Micro-Aero-Engine

by Huigui Long, Kui Chen, Zhuojie Nong and Haozhong Huang

Aerospace 2025, 12(12), 1068; https://doi.org/10.3390/aerospace12121068 - 30 Nov 2025

Rotational speed is a key performance parameter of aero-engines. As an indispensable parameter in control systems, rotational speed has received widespread attention. However, research on rotational speed control methods for micro-turbojet engines used in unmanned aerial vehicles is relatively limited. Therefore, this paper [...] Read more.

Rotational speed is a key performance parameter of aero-engines. As an indispensable parameter in control systems, rotational speed has received widespread attention. However, research on rotational speed control methods for micro-turbojet engines used in unmanned aerial vehicles is relatively limited. Therefore, this paper proposes a rotational speed controller for micro-turbojet engines based on the Improved Spider Wasp Optimization (ISWO) algorithm, which adopts Linear Active Disturbance Rejection Control (LADRC) technology. Data from the actual operation of the micro-turbojet engine were collected, and the engine rotational speed models under three operating conditions were obtained through system identification. The proposed controller was applied to these rotational speed models, along with the classic Proportional–Integral–Derivative (PID) controller, the LADRC controller, and the LADRC controller based on the original Spider Wasp Optimization (SWO) algorithm. Simulation experiments and comparisons of the controllers were conducted based on performance indicators. The simulation results show that under the three operating conditions, the ISWO-LADRC controller outperforms the other three controllers in indicators such as rise time, overshoot, and settling time, all of which are smaller. Thus, ISWO-LADRC exhibits better comprehensive control performance. Full article

(This article belongs to the Section Aeronautics)

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45 pages, 15707 KB

Open AccessArticle

Lightweight, High-Efficiency, High-Dynamic-Response and Low-Ripple DC-DC Converters Based on Interleaved Magnetic Integrated Switched-Coupled Inductor for Electric Propulsion Aircraft

by Rui Guo, Hongkai Gao, Li Chen, Yiyi Zhang and Lei Wang

Aerospace 2025, 12(12), 1067; https://doi.org/10.3390/aerospace12121067 - 30 Nov 2025

With the development of distributed electric propulsion aircraft, researching airborne high-efficiency, high-power-density, high-gain, high-dynamic and low-ripple, low-stress DC-DC that meets aviation standards is an urgent and profoundly challenging task (Research Background). We propose a new topology to implement related applications. The new topology [...] Read more.

With the development of distributed electric propulsion aircraft, researching airborne high-efficiency, high-power-density, high-gain, high-dynamic and low-ripple, low-stress DC-DC that meets aviation standards is an urgent and profoundly challenging task (Research Background). We propose a new topology to implement related applications. The new topology consists of an interleaved switched-inductor unit for a high-gain, low-ripple, and high-dynamic response, and a switched-capacitor unit for secondary boosting and low voltage stress. This study first analyzes in depth the operating principle and electrical characteristics of the proposed topology in different modes, showing that the proposed topology can achieve an extremely high voltage gain while maintaining low voltage stress. Moreover, the proposed topology employs interleaved inverse coupled inductors to eliminate right-half-plane zero (RHPZ). We establish a universal design guideline for coupled inductors by deriving the equivalent inductance equations, and we implement an ultra-lightweight switched-coupled inductor using planar thin-film integrated magnetic technology. We conduct small-signal modeling to verify the loop characteristics and stability of the proposed converter. Finally, the correctness of the theoretical analysis and the advantages of the proposed converter were verified through a 5000 W experimental prototype and comprehensive comparative experiments. Full article

(This article belongs to the Special Issue Advanced Aircraft Technology (2nd Edition))

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