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31 pages, 11029 KiB

Open AccessArticle

Adapting e-Genius for Next-Level Efficient Electric Aerotow with High-Power Propulsion and Automatic Flight Control System

by Stefan Zistler, Dalong Shi, Walter Fichter and Andreas Strohmayer

Aerospace 2025, 12(5), 409; https://doi.org/10.3390/aerospace12050409 - 6 May 2025

Viewed by 150

Abstract

Aiming to reduce energy demand and carbon footprint, minimize noise impact, and enhance flight safety and efficiency during aerotow operations, this study integrates an electric propulsion system and an automatic flight control system (AFCS) into the electric research aircraft e-Genius. An advanced propulsion [...] Read more.

Aiming to reduce energy demand and carbon footprint, minimize noise impact, and enhance flight safety and efficiency during aerotow operations, this study integrates an electric propulsion system and an automatic flight control system (AFCS) into the electric research aircraft e-Genius. An advanced propulsion system is developed using high-performance batteries and available electric drive components, while the AFCS is designed following a systematic process of developing flight control algorithms. Flight tests are then conducted to evaluate the performance of individual components and the overall system. The test results demonstrate that the upgraded propulsion system provides sufficient power to launch sailplanes, even with the maximum takeoff mass, while significantly reducing energy demand when compared to contemporary fossil fueled towplanes. Additionally, the AFCS proves to be stable and robust, successfully following specified commanded states, executing path tracking, and performing aerotow operations. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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27 pages, 6906 KiB

Open AccessArticle

Error Covariance Analyses for Celestial Triangulation and Its Optimality: Improved Linear Optimal Sine Triangulation

by Abdurrahim Muratoglu, Halil Ersin Söken and Uwe Soergel

Aerospace 2025, 12(5), 385; https://doi.org/10.3390/aerospace12050385 - 29 Apr 2025

Viewed by 168

Abstract

This study presents an improved methodology for celestial triangulation optimization in spacecraft navigation, addressing limitations in existing approaches. While current methods like Linear Optimal Sine Triangulation (LOST) provide statistically optimal solutions for position estimation using multiple celestial body observations, their performance can be [...] Read more.

This study presents an improved methodology for celestial triangulation optimization in spacecraft navigation, addressing limitations in existing approaches. While current methods like Linear Optimal Sine Triangulation (LOST) provide statistically optimal solutions for position estimation using multiple celestial body observations, their performance can be compromised by suboptimal measurement pair selection. The proposed approach, called the Improved-LOST algorithm, introduces a systematic method for evaluating and selecting optimal measurement pairs based on a Cramér–Rao Lower-Bound (CRLB) analysis. Through theoretical analysis and numerical simulations on translunar trajectories, this study demonstrates that geometric configuration significantly influences position estimation accuracy, with error variances varying by orders of magnitude depending on observation geometry. The improved algorithm outperforms conventional implementations, particularly in scenarios with challenging geometric configurations. Simulation results along a translunar trajectory using various celestial body combinations show that the systematic selection of measurement pairs based on CRLB minimization leads to enhanced estimation accuracy compared to arbitrary pair selection. The findings provide valuable insights for autonomous navigation system design and mission planning, offering a quantitative framework for assessing and optimizing celestial triangulation performance in deep space missions. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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21 pages, 10134 KiB

Open AccessArticle

Development of a Modular Test Rig for In-Flight Validation of a Multi-Hole Probe Onboard the e-Genius-Mod

by Eskil Jonas Nussbaumer, Sara Hijazi, Dominique Paul Bergmann, Hanno Streit and Andreas Strohmayer

Aerospace 2025, 12(4), 345; https://doi.org/10.3390/aerospace12040345 - 15 Apr 2025

Viewed by 229

Abstract

Scaled flight demonstrators have played an important part throughout the history of aviation. Ranging from aviation pioneers to renowned institutions like the National Aeronautics and Space Administration (NASA), many actors have relied on miniaturized models in both research and development. Despite the age [...] Read more.

Scaled flight demonstrators have played an important part throughout the history of aviation. Ranging from aviation pioneers to renowned institutions like the National Aeronautics and Space Administration (NASA), many actors have relied on miniaturized models in both research and development. Despite the age of the method, sub-scale models are still being used as a low-cost option for flight tests in realistic flight conditions. One utilization aspect that is becoming increasingly popular is as a flying test platform for the development and testing of new aviation technologies or capabilities. By conducting flight tests in real atmospheric conditions, it enables a low-cost link between analytical studies and full-scale testing, consequently closing the gap between Technology Readiness Levels (TRLs) 4 and 6, which is both time- and cost-efficient. For this paper, the utilization of the e-Genius-Mod, a modular scaled version of the all-electric e-Genius aircraft, as a versatile platform for testing new technologies is being investigated. As a case study, a multi-hole probe (MHP) is installed onto the aircraft through a custom-made wing adapter and connected to an independent data collection system. By using Computational Fluid Dynamics (CFD) simulations and wind-tunnel tests, the probe installation is validated, paving the way for upcoming flight tests. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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20 pages, 1009 KiB

Open AccessArticle

Permeation Investigation of Carbon Fibre Reinforced Polymer Material for LH2 Storage Thermally Shocked and Mechanically Cycled at Cryogenic Temperature

by Giacomo Dreossi and Andrej Bernard Horvat

Aerospace 2025, 12(4), 342; https://doi.org/10.3390/aerospace12040342 - 14 Apr 2025

Viewed by 286

Abstract

To achieve the sustainability goals set for the European aviation sector, hydrogen-powered solutions are currently being investigated. Storage solutions are of particular interest, with liquid hydrogen tanks posing numerous challenges with regard to the structural integrity of materials at cryogenic temperatures, as well [...] Read more.

To achieve the sustainability goals set for the European aviation sector, hydrogen-powered solutions are currently being investigated. Storage solutions are of particular interest, with liquid hydrogen tanks posing numerous challenges with regard to the structural integrity of materials at cryogenic temperatures, as well as safety issues because of the high flammability of hydrogen. In this context and in the scope of the Horizon 2020 Clean Aviation Joint Undertaking (CAJU) project H2ELIOS, the gas permeability behavior of prepreg tape carbon fibre reinforced polymer (CFRP) material was studied. Investigations were performed after thermal shock to 20 K (liquid hydrogen immersion) as well as after a uniaxial stress application at 77 K to identify the shift from Fickian behavior after diverse aging conditions. Helium gas permeation was tested at room temperature (RT), and its representativeness to hydrogen permeation in a range of temperatures was considered in the study. The material’s permeation behavior was compared to ideal Fickian diffusion as a means of identifying related permeation barrier function degradation. Finally, it was possible to identify Fickian, near-Fickian, and non-Fickian behaviors and correlate them with the material’s preconditioning. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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25 pages, 3850 KiB

Open AccessArticle

Fundamentals of Innovative Aircraft Heat Exchanger Integration for Hydrogen–Electric Propulsion

by Bernhard Gerl, Matthias Ronovsky-Bodisch, Niccoló Ferrari and Martin Berens

Aerospace 2025, 12(4), 320; https://doi.org/10.3390/aerospace12040320 - 9 Apr 2025

Cited by 1 | Viewed by 766

Abstract

The potential of utilizing the rejected heat of a fuel cell system to improve the aircraft propulsive efficiency is discussed for various flight conditions. The thermodynamic background of the process and the connection of power consumption in the fan of the ducted propulsor [...] Read more.

The potential of utilizing the rejected heat of a fuel cell system to improve the aircraft propulsive efficiency is discussed for various flight conditions. The thermodynamic background of the process and the connection of power consumption in the fan of the ducted propulsor and fuel cell heat are given, and a link between these two components is presented. A concept that goes beyond the known ram heat exchanger is discussed, which outlines the potential benefits of integrating a fan upstream of the heat exchanger. The influence of the fan pressure ratio, flight speed, and altitude, as well as the temperature level of the available fuel cell heat on the propulsive efficiency, is presented. A correlation between the fan pressure ratio, flight speed, and exchangeable fuel cell heat is established, providing a simplified computational approach for evaluating feasible operating conditions within this process. This paper identifies the challenges of heat exchanger integration at International Standard Atmosphere sea level conditions and its benefits for cruise flight conditions. The results show that for a flight Mach number of 0.8 and a fan pressure ratio of 1.5 at a cruising altitude of 11,000 m, the propulsion efficiency increases by approximately 8 percentage points compared to a ducted propulsor without heat utilization. Under sea-level conditions, the concept does not offer any performance advantages over a ducted propulsor. Instead, it exhibits either comparable or reduced propulsive efficiency. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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10 pages, 3124 KiB

Open AccessArticle

Surface-Tailoring and Morphology Control as Strategies for Sustainable Development in Transport Sector

by Luis Antonio Sanchez de Almeida Prado, Selim Coskun, Anne-Laure Cadène, Ramón Angel Antelo Reguengo, Jake Carter, Kyle Ito, Minok Park and Vassilia Zorba

Aerospace 2025, 12(4), 301; https://doi.org/10.3390/aerospace12040301 - 1 Apr 2025

Viewed by 401

Abstract

Surface wetting plays an important role in the corrosion protection processes of aerospace applications. Here, we demonstrate the use of ultrafast femtosecond (fs) laser processing techniques to tailor the wetting properties of aluminum (Al) substrates by creating diverse surface morphologies. Specifically, two distinct [...] Read more.

Surface wetting plays an important role in the corrosion protection processes of aerospace applications. Here, we demonstrate the use of ultrafast femtosecond (fs) laser processing techniques to tailor the wetting properties of aluminum (Al) substrates by creating diverse surface morphologies. Specifically, two distinct laser scanning methods—dot-hatching and cross-hatching—were employed to fabricate microstructures on the substrates. By varying the incident laser parameters, we confirmed that the resulting surface morphologies exhibit different wetting behaviors, spanning from hydrophilicity to hydrophobicity. Furthermore, time-resolved spreading tests validate that dynamic wetting behaviors can also be modified. This fs laser processing approach provides a straightforward, one-step fabrication method for effectively modifying the wetting properties of Al alloys. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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33 pages, 371 KiB

Open AccessArticle

Preliminary Aircraft Design for Hybrid Electric Propulsion Architectures: A Focus on Critical Loss of Thrust

by Jonas Mangold and Andreas Strohmayer

Aerospace 2025, 12(4), 275; https://doi.org/10.3390/aerospace12040275 - 25 Mar 2025

Viewed by 441

Abstract

Hybrid electric propulsion architectures offer a promising solution for reducing fuel consumption and emissions in aviation. However, the introduction of dual-energy carriers adds complexity to preliminary aircraft design, particularly in terms of power distribution, failure analysis, and compliance with operational regulations. Key challenges [...] Read more.

Hybrid electric propulsion architectures offer a promising solution for reducing fuel consumption and emissions in aviation. However, the introduction of dual-energy carriers adds complexity to preliminary aircraft design, particularly in terms of power distribution, failure analysis, and compliance with operational regulations. Key challenges include defining failure cases, which requires refining conventional constraint analysis for hybrid electric aircraft and integrating failure scenarios into mission analysis to meet certification specifications and regulatory requirements. This study presents a unified methodology that combines an analytical constraint analysis with a higher-fidelity numerical design loop implemented in the SUAVE framework to address these challenges. Key innovations include the introduction of new parameters—such as the supplied shaft power ratio—and the ability to assess failure scenarios through the definition of the critical loss of thrust, thereby extending the analysis beyond conventional one-engine-inoperative cases. The methodology also integrates an energy management strategy that dynamically allocates power between the primary and secondary energy carriers, thereby capturing the interaction between energy (mission analysis) and power (constraint analysis) requirements. The results from both the constraint and mission analyses, including en-route alternate aerodrome scenarios, demonstrate that employing batteries as the secondary energy carrier can reduce the oversizing of primary power sources. However, their effective utilization is highly sensitive and may necessitate adjustments in energy sizing. These findings underscore the importance of incorporating dual-energy carrier considerations early in the design process and highlight the impact of critical loss of thrust conditions on hybrid electric aircraft configurations, ultimately benefiting researchers and engineers. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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17 pages, 13833 KiB

Open AccessArticle

Functionalization of Adhesive Bonding to Control On-Demand Disassembly of Composite Aeronautical Structures

by Lorraine Aparecida Silva, Christine Espinosa, Rémy Chieragatti, Eric Paroissien, Frédéric Lachaud and Lucas Filipe Martins da Silva

Aerospace 2025, 12(4), 269; https://doi.org/10.3390/aerospace12040269 - 22 Mar 2025

Viewed by 412

Abstract

In the context of enhancing the sustainability of aerospace vehicles, the structures must be designed to anticipate the possibility of disassembly. Mandatory certification in aeronautics and the robustness of satellites require structures to maintain their integrity to ensure safety during their life, which [...] Read more.

In the context of enhancing the sustainability of aerospace vehicles, the structures must be designed to anticipate the possibility of disassembly. Mandatory certification in aeronautics and the robustness of satellites require structures to maintain their integrity to ensure safety during their life, which can come into conflict with the need for disassembling or demising. This is particularly the case for composite structures assembled though adhesive bonding. In this paper, a controlled disassembly device of the substrates of a component for keeping their integrity and surface states after debonding is proposed. The addition of thermally expandable particles (TEPs) and a metallic grid is investigated in various proportions, substrates, and adhesives. It is shown that the introduction of the disassembling system into a 100 µm adhesive bonding does not significantly affect the strength of the joint during life. Disassembly only happens when and if desired at a load level above the natural mode I and mode II ruptures of the assembly. The proposed solution helps to make functionalization of the bonded joint a good way to address sustainability regarding the preservation of resources, transforming the adhesive joint into a structural functional material. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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12 pages, 2976 KiB

Open AccessArticle

Overview of the Clean Sky 2 Technology Evaluator Project Methodology

by Alf Junior, Alexandra Leipold and Marc C. Gelhausen

Aerospace 2025, 12(4), 268; https://doi.org/10.3390/aerospace12040268 - 21 Mar 2025

Viewed by 420

Abstract

Clean Sky 2 (CS2) was established to reduce the environmental impact of air transport by the introduction of new advanced aeronautical technologies, to improve mobility and to demonstrate reduction potentials for CO₂, NO_x, and noise emissions of from 20% [...] Read more.

Clean Sky 2 (CS2) was established to reduce the environmental impact of air transport by the introduction of new advanced aeronautical technologies, to improve mobility and to demonstrate reduction potentials for CO₂, NO_x, and noise emissions of from 20% to 30% as compared to state-of-the-art aircraft in 2014. A wide range of new technologies has been integrated into vehicle performance models for a set of concept aircraft, and the Clean Sky 2 Technology Evaluator (TE) has performed assessments with three major pillars: Vehicle- or mission-level reference aircraft, reflecting 2014 technologies, are compared with new Clean Sky 2 concept aircraft with a focus on CO₂ and NO_x emission and noise reduction potentials. At the airport level, environmental impact assessments for different traffic and fleet mixes are carried out, namely, noise on the ground and population impacted by certain noise levels and emissions (CO₂ and NO_x). At the level of the global air transport system (ATS), those new concept aircraft are embedded in fleet projections until 2050 and compared to a projection without new Clean Sky 2 aircraft to understand the emission reduction potentials of future global fleets and the long-term aviation footprint. This paper gives a conceptual overview of the work carried out in Clean Sky 2. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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25 pages, 16804 KiB

Open AccessArticle

Development and Demonstration of a Novel Test Bench for the Experimental Validation of Fuselage Stiffened Panel Simulations

by Panagiotis D. Kordas, Konstantinos T. Fotopoulos and George N. Lampeas

Aerospace 2025, 12(3), 263; https://doi.org/10.3390/aerospace12030263 - 20 Mar 2025

Viewed by 306

Abstract

The subject of the present work is the development and implementation of a novel testing facility to carry out an experimental campaign on an advanced fuselage panel manufactured from both thermoplastic and metallic materials, as well as the validation of its numerical simulation. [...] Read more.

The subject of the present work is the development and implementation of a novel testing facility to carry out an experimental campaign on an advanced fuselage panel manufactured from both thermoplastic and metallic materials, as well as the validation of its numerical simulation. The experimental arrangement was specifically designed, assembled, and instrumented to have multi-axial loading capabilities. The investigated load cases comprised uniaxial in-plane compression, lateral distributed pressure, and their combination. The introduction of pressure was enabled by inflatable airbags, and compression was applied up to the onset of local skin buckling. Calibration of the load introduction and inspection equipment was performed in multiple steps to acquire accurate and representative measurements. Data were recorded by external sensors mounted on a hydraulic actuator and an optical Digital Image Correlation (DIC) system. A numerical simulation of the fuselage panel and the test rig was developed, and a validation study was conducted. In the Finite Element (FE) model, several of the experimental configuration’s supporting elements and their connections to the specimen were integrated as constraints and boundary conditions. Data procured from the tests were correlated to the simulation’s predictions, presenting low errors in most displacement/strain distributions. The results show that the proposed test rig concept is suitable for stiffened panel level testing and could be used for future studies on similar aeronautical components. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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29 pages, 836 KiB

Open AccessArticle

Preliminary Design of Regional Aircraft—Integration of a Fuel Cell-Electric Energy Network in SUAVE

by Jakob Schlittenhardt, Yannik Freund, Jonas Mangold, Richard Hanke-Rauschenbach and Andreas Strohmayer

Aerospace 2025, 12(3), 249; https://doi.org/10.3390/aerospace12030249 - 17 Mar 2025

Viewed by 484

Abstract

To enable climate-neutral aviation, improving the energy efficiency of aircraft is essential. The research project Synergies of Highly Integrated Transport Aircraft investigates cross-disciplinary synergies in aircraft and propulsion technologies to achieve energy savings. This study examines a fuel cell electric powered configuration with [...] Read more.

To enable climate-neutral aviation, improving the energy efficiency of aircraft is essential. The research project Synergies of Highly Integrated Transport Aircraft investigates cross-disciplinary synergies in aircraft and propulsion technologies to achieve energy savings. This study examines a fuel cell electric powered configuration with distributed electric propulsion. For this, a reverse-engineered ATR 72-500 serves as a reference model for calibrating the methods and ensuring accurate performance modeling. A baseline configuration featuring a state-of-the-art turboprop engine with the same entry-into-service is also introduced for a meaningful performance comparison. The analysis uses an enhanced version of the Stanford University Aerospace Vehicle Environment (SUAVE), a Python-based aircraft design environment that allows for novel energy network architectures. This paper details the preliminary aircraft design process, including calibration, presents the resulting aircraft configurations, and examines the integration of a fuel cell-electric energy network. The results provide a foundation for higher fidelity studies and performance comparisons, offering insights into the trade-offs associated with hydrogen-based propulsion systems. All fundamental equations and methodologies are explicitly presented, ensuring transparency, clarity, and reproducibility. This comprehensive disclosure allows the broader scientific community to utilize and refine these findings, facilitating further progress in hydrogen-powered aviation technologies. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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22 pages, 1615 KiB

Open AccessArticle

Certification Gap Analysis for Normal-Category and Large Hydrogen-Powered Airplanes

by Joël Jézégou, Alvaro Mauricio Almeida-Marino, Gregory O’Sullivan, Beatriz Jiménez Carrasco, Robert André and Yves Gourinat

Aerospace 2025, 12(3), 239; https://doi.org/10.3390/aerospace12030239 - 14 Mar 2025

Viewed by 917

Abstract

The transition to hydrogen as an aviation fuel, as outlined in current decarbonization roadmaps, is expected to result in the entry into service of hydrogen-powered aircraft in 2035. To achieve this evolution, certification regulations are key enablers. Due to the disruptive nature of [...] Read more.

The transition to hydrogen as an aviation fuel, as outlined in current decarbonization roadmaps, is expected to result in the entry into service of hydrogen-powered aircraft in 2035. To achieve this evolution, certification regulations are key enablers. Due to the disruptive nature of hydrogen aircraft technologies and their associated hazards, it is essential to assess the maturity of the existing regulatory framework for certification to ensure its availability when manufacturers apply for aircraft certification. This paper presents the work conducted under the Clean Aviation CONCERTO project to advance certification readiness by comprehensively identifying gaps in the current European regulations. Generic methodologies were developed for regulatory gap and risk analyses and applied to a hydrogen turbine aircraft with non-propulsive fuel cells as the APU. The gap analysis, conducted on certification specifications for large and normal-category airplanes as well as engines, confirmed the overall adequacy of many existing requirements. However, important gaps exist to appropriately address hydrogen hazards particularly concerning fire and explosion, hydrogen storage and fuel systems, crashworthiness, and occupant survivability. The paper concludes by identifying critical areas for certification and highlighting the need for complementary hydrogen phenomenology data, which are key to guiding future research and regulatory efforts for certification readiness maturation. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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19 pages, 33574 KiB

Open AccessArticle

Mechanical and Thermal Contributions to the Damage Suffered by an Aeronautical Structure Subjected to an Intense and Sudden Electrical Discharge

by Bryan Better, Aboulghit El Malki Alaoui, Christine Espinosa, Michel Arrigoni, Nathan Menetrier, Chabouh Yazidjian, Serge Guetta, Frédéric Lachaud, Christian Jochum, Michel Boustie and Didier Zagouri

Aerospace 2025, 12(3), 235; https://doi.org/10.3390/aerospace12030235 - 14 Mar 2025

Viewed by 372

Abstract

Lightweight aeronautical structures and power generation structures such as wind turbines are fitted with protected external layers designed and certified to withstand severe climatic events such as lightning strikes. During these events, high currents flow through the structural protection but are likely to [...] Read more.

Lightweight aeronautical structures and power generation structures such as wind turbines are fitted with protected external layers designed and certified to withstand severe climatic events such as lightning strikes. During these events, high currents flow through the structural protection but are likely to induce effects deeper in the supporting composite material and could even reach or perforate pressurized tanks. In situ measurements are hard to achieve during current delivery due to the severe electromagnetic conditions, and the lightning strike phenomenon on these structures is not yet fully investigated. To gain a better understanding of the physics involved, similarities in direct damage between lightning-struck samples and those subjected to pulsed lasers and an electron gun are analyzed. These analyses show the inability of a pure mechanical contribution to fully reproduce the shape of the delamination distribution of lightning strikes. Conversely, the similarities in effect and damage with the thermomechanical contribution of electron beam deposition are highlighted, particularly the increase in core delamination due to the paint and the apparent similarities in delamination distribution. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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11 pages, 1651 KiB

Open AccessArticle

Modelling of the Power Demand of Peripheral Aggregates of an Airborne Fuel Cell-Based Power System

by Nejat Mahdavi

Aerospace 2025, 12(3), 234; https://doi.org/10.3390/aerospace12030234 - 13 Mar 2025

Viewed by 503

Abstract

Because of the higher energy density of hydrogen as a clean energy source, the use of proton exchange membrane fuel cells (PEMFCs) for aviation applications has become an important research topic in recent years. Unlike batteries, fuel cells require a lot of peripheral [...] Read more.

Because of the higher energy density of hydrogen as a clean energy source, the use of proton exchange membrane fuel cells (PEMFCs) for aviation applications has become an important research topic in recent years. Unlike batteries, fuel cells require a lot of peripheral aggregates to operate properly. The peripheral aggregates of a fuel cell, which constitute the so-called balance of plant (BoP), consume a certain part of the power generated by the fuel cell stack, which reduces the overall efficiency of the fuel cell system. One of the greatest challenges in the design of a fuel cell system is the sizing of the fuel cell stack and the determination of the internal power consumption of the BoP. This paper models the power demand of the BoP of a fuel cell system based on an automotive fuel cell power system. Furthermore, the effect of flight altitude on the power demand of the BoP is investigated. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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25 pages, 4969 KiB

Open AccessArticle

A Design Guide to Tapered Conformable Pressure Tanks for Liquid Hydrogen Storage

by Joren Malfroy, Johan Steelant and Dirk Vandepitte

Aerospace 2025, 12(3), 190; https://doi.org/10.3390/aerospace12030190 - 27 Feb 2025

Cited by 1 | Viewed by 799

Abstract

Liquid hydrogen has the potential to significantly reduce in-flight carbon emissions in the aviation industry. Among the most promising aircraft configurations for future hydrogen-powered aviation are the blended wing body and the pure flying wing configurations. However, their tapered and flattened airframe designs [...] Read more.

Liquid hydrogen has the potential to significantly reduce in-flight carbon emissions in the aviation industry. Among the most promising aircraft configurations for future hydrogen-powered aviation are the blended wing body and the pure flying wing configurations. However, their tapered and flattened airframe designs pose a challenge in accommodating liquid hydrogen storage tanks. This paper presents a design guide to tapered conformable pressure tanks for liquid hydrogen storage. The proposed tank configurations feature a multi-bubble layout and are subject to low internal differential pressure. The objective is to provide tank designers with simple geometric rules and practical guidelines to simplify the design process of tapered multi-bubble pressure tanks. Various tank configurations are discussed, starting with a simple tapered two-bubble tank and advancing to more complex tapered configurations with a multi-segment and multi-bubble layout. A comprehensive design methodology is established, providing tank designers with a step-by-step design procedure and highlighting the practical guidelines in each step of the design process. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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20 pages, 9978 KiB

Open AccessArticle

Test Results for a Novel 20 kW Two-Phase Pumped Cooling System for Aerospace Applications

by Henk Jan van Gerner, Tim Luten, Sigurd Scholten, Georg Mühlthaler and Marcus-Benedict Buntz

Aerospace 2025, 12(3), 188; https://doi.org/10.3390/aerospace12030188 - 26 Feb 2025

Viewed by 773

Abstract

In the EU-funded BRAVA project, technologies for a fuel cell-based power generation system for aviation are being developed. In this paper, the test results for a demonstrator of a novel two-phase pumped cooling system with 20 kW cooling capacity are presented. This system [...] Read more.

In the EU-funded BRAVA project, technologies for a fuel cell-based power generation system for aviation are being developed. In this paper, the test results for a demonstrator of a novel two-phase pumped cooling system with 20 kW cooling capacity are presented. This system uses the evaporation of a liquid to remove waste heat from the heat sources. Several concepts have been tested with this demonstrator, including the ‘no accumulator’ concept, which offers a large mass reduction compared to conventional cooling systems. Additionally, the system can be rotated, and the influence of the orientation has been tested. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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18 pages, 1052 KiB

Open AccessArticle

Deployment of a Testbed for Validation of TSN Networks in Avionics

by Laura Castro-Lara, Pablo Vera-Soto, Sergio Fortes, Vicente Escaño, Rafael Ortiz and Raquel Barco

Aerospace 2025, 12(3), 186; https://doi.org/10.3390/aerospace12030186 - 26 Feb 2025

Viewed by 686

Abstract

Time-Sensitive Networking (TSN) in avionics is being considered as a standard capable of providing more real-time and safety-critical capabilities than AFDX, the current standard in avionics communications. A TSN profile is therefore being developed for the aerospace domain by IEEE. Hence, this research [...] Read more.

Time-Sensitive Networking (TSN) in avionics is being considered as a standard capable of providing more real-time and safety-critical capabilities than AFDX, the current standard in avionics communications. A TSN profile is therefore being developed for the aerospace domain by IEEE. Hence, this research outlines the deployment of a testbed aimed at validating TSN in avionics to ensure that this technology meets the stringent timing and latency requirements of avionics applications. To this end, a daisy chain or ring topology has been set up for the validation of the testbed, as this topology provides redundancy of paths without the need to add additional devices. This work presents latency and jitter measurements under different priority configurations and different channel saturation conditions, showing no packet loss and demonstrating the reliability of TSN for time-critical applications. A comparison with Avionics Full Duplex Ethernet (AFDX) simulations was also made, highlighting the weaknesses of AFDX. By providing a comprehensive platform for testing and validation, the testbed will contribute to the advancement of TSN technology in aerospace applications, ultimately improving the safety and efficiency of aircraft operations. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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22 pages, 4466 KiB

Open AccessArticle

Results from the ATS-Level Assessment of the Clean Sky 2 Technology Evaluator

by Marc C. Gelhausen, Alf Junior, Alexandra Leipold, Peter Berster, Holger Pabst, Christos Lois and Fabian Baier

Aerospace 2025, 12(3), 185; https://doi.org/10.3390/aerospace12030185 - 26 Feb 2025

Cited by 1 | Viewed by 504

Abstract

In this paper, we present the main results from the Second ATS-Level Assessment of the Clean Sky 2 Technology Evaluator. We first present the models employed and then move to the passenger and fleet forecast results up to 2050. Based upon these traffic [...] Read more.

In this paper, we present the main results from the Second ATS-Level Assessment of the Clean Sky 2 Technology Evaluator. We first present the models employed and then move to the passenger and fleet forecast results up to 2050. Based upon these traffic forecasts, we show the environmental effect of Clean Sky 2 technology in terms of CO₂ emissions. The main benefit of the forecast method employed is its high resolution in terms of each flight route between airports being modelled. Consequently, we can consider effects such as airport capacity constraints which will have a substantial impact on future passenger volume and fleet development. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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27 pages, 6275 KiB

Open AccessArticle

Integrating Sustainability in Aircraft Component Design: Towards a Transition from Eco-Driven to Sustainability-Driven Design

by Angelos Filippatos, Dionysios Markatos, Athina Theochari and Spiros Pantelakis

Aerospace 2025, 12(2), 140; https://doi.org/10.3390/aerospace12020140 - 13 Feb 2025

Viewed by 850

Abstract

Eco-design is an innovative design methodology that focuses on minimizing the environmental footprint of industries, including aviation, right from the conceptual and development stages. However, rising industrial demand calls for a more comprehensive strategy wherein, beyond environmental considerations, competitiveness becomes a critical factor, [...] Read more.

Eco-design is an innovative design methodology that focuses on minimizing the environmental footprint of industries, including aviation, right from the conceptual and development stages. However, rising industrial demand calls for a more comprehensive strategy wherein, beyond environmental considerations, competitiveness becomes a critical factor, supported by additional pillars of sustainability such as economic viability, circularity, and social impact. By incorporating sustainability as a primary design driver at the initial design stages, this study suggests a shift from eco-driven to sustainability-driven design approaches for aircraft components. This expanded strategy considers performance and safety goals, environmental impact, costs, social factors, and circular economy considerations. To provide the most sustainable design that balances all objectives, these aspects are rigorously quantified and optimized during the design process. To efficiently prioritize different variables, methods such as multi-criteria decision-making (MCDM) are employed, and a sustainability index is developed in this framework to assess the overall sustainability of each design alternative. The most sustainable design configurations are then identified through an optimization process. A typical aircraft component, namely a hat-stiffened panel, is selected to demonstrate the proposed approach. The study highlights how effectively sustainability considerations can be integrated from the early stages of the design process by exploring diverse material combinations and geometric configurations. The findings indicate that the type of fuel used, and the importance given to the sustainability pillars—which are ultimately determined by the particular requirements and goals of the user—have a significant impact on the sustainability outcome. When equal prioritization is given across the diverse dimensions of sustainability, the most sustainable option appears to be the full thermoplastic component when kerosene is used. Conversely, when hydrogen is considered, the full aluminum component emerges as the most sustainable choice. This trend also holds when environmental impact is prioritized over the other aspects of sustainability. However, when costs are prioritized, the full thermoplastic component is the most sustainable option, whether hydrogen or kerosene is used as the fuel in the use phase. This innovative approach enhances the overall sustainability of aircraft components, emphasizing the importance and benefits of incorporating a broader range of sustainability factors at the conceptual and initial design phases. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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24 pages, 3280 KiB

Open AccessArticle

Comparative Analysis on Modelling Approaches for the Simulation of Fatigue Disbonding with Cohesive Zone Models

by Johan Birnie, Maria Pia Falaschetti and Enrico Troiani

Aerospace 2025, 12(2), 139; https://doi.org/10.3390/aerospace12020139 - 13 Feb 2025

Cited by 1 | Viewed by 752

Abstract

Adhesively bonded joints are essential in the aeronautical industry, offering benefits such as weight reduction and enhanced sustainability. However, certifying these joints is challenging due to unreliable methods for assessing their strength and the development of predictive models for fatigue-driven disbonding remains an [...] Read more.

Adhesively bonded joints are essential in the aeronautical industry, offering benefits such as weight reduction and enhanced sustainability. However, certifying these joints is challenging due to unreliable methods for assessing their strength and the development of predictive models for fatigue-driven disbonding remains an ongoing effort. This manuscript presents the implementation and validation of a cohesive zone model for studying high-cycle fatigue disbonding under Mode I and Mixed-Mode loading. The model was integrated into the commercial finite element analysis software Abaqus using user-defined material subroutine (UMAT). Two modelling approaches were investigated: one replacing the adhesive with a cohesive layer, and the other incorporating a cohesive layer at the adhesive’s mid-plane while modelling its entire thickness, using both 2D and 3D techniques. Validation was conducted against experimental data from the literature that examined the influence of adhesive thickness on fatigue behaviour in DCB and CLS tests. The findings of this study confirm that the model accurately predicts fatigue disbonding across all cases examined. Additionally, the analysis reveals that modelling adhesive thickness plays a critical role in the simulation’s outcomes. Variations in adhesive thickness can significantly alter the crack growth behaviour, highlighting the importance of carefully considering this parameter in future assessments and applications. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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24 pages, 2318 KiB

Open AccessArticle

A Comparative Analysis of Multi-Criteria Decision-Making Methods and Normalization Techniques in Holistic Sustainability Assessment for Engineering Applications

by Sonia Malefaki, Dionysios Markatos, Angelos Filippatos and Spiros Pantelakis

Aerospace 2025, 12(2), 100; https://doi.org/10.3390/aerospace12020100 - 29 Jan 2025

Cited by 1 | Viewed by 1783

Abstract

The sustainability evaluation of engineering processes and structures is a multifaceted challenge requiring the integration of diverse and often conflicting criteria. To address this challenge, Multi-Criteria Decision-Making (MCDM) methods have emerged as effective tools. However, the selection of the most suitable MCDM approach [...] Read more.

The sustainability evaluation of engineering processes and structures is a multifaceted challenge requiring the integration of diverse and often conflicting criteria. To address this challenge, Multi-Criteria Decision-Making (MCDM) methods have emerged as effective tools. However, the selection of the most suitable MCDM approach for problems involving multiple criteria is critical to ensuring robust, reliable, and actionable outcomes. Equally significant is the choice of a proper normalization technique, which plays a pivotal role in determining the robustness and reliability of the results. This study investigates the impact of common MCDM tools on the decision-making process concerning diverse aspects of sustainability. It also examines how different normalization methods influence the final outcomes. Sustainability in this context is understood as a trade-off among five key dimensions: performance, environmental impact, economic impact, social impact, and circularity. The outcome of the MCDM process is represented by an aggregated metric, referred to as the Sustainability Index (SI). This index offers a comprehensive and robust framework for evaluating sustainability and facilitating decision-making when conflicting criteria are present. To assess the effects of implementing different MCDM and normalization choices on the sustainability assessment, a dataset from the aviation sector is employed. Specifically, a typical aircraft component is analyzed as a case study for holistic sustainability assessment, utilizing data that represent the various dimensions of sustainability mentioned above, for this component. Additionally, the study investigates the influence of initial data variations and weight variations within the MCDM process on the results. The results indicate that, overall, the different MCDM and normalization methods lead to similar outcomes when applied to the design alternatives. However, a deeper dive into the results reveals that the weighted sum method, when paired with min-max normalization, appears to be more appropriate, based on the use case involved for the present investigation, due to its robustness regarding small variations in the initial data and its sensitivity to large ones. This research underscores the critical importance of selecting appropriate MCDM tools and normalization methods to enhance transparency, robustness, reliability, and consistency of sustainability assessments within a holistic framework. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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23 pages, 11530 KiB

Open AccessArticle

Winglet Design for Aerodynamic and Performance Optimization of UAVs via Surrogate Modeling

by Eleftherios Nikolaou, Spyridon Kilimtzidis and Vassilis Kostopoulos

Aerospace 2025, 12(1), 36; https://doi.org/10.3390/aerospace12010036 - 9 Jan 2025

Cited by 2 | Viewed by 2507

Abstract

The aerodynamic performance of an aircraft can be significantly enhanced by incorporating wingtip devices, such as winglets, which primarily reduce lift-induced drag caused by wingtip vortices. This study introduces a comprehensive optimization framework for designing winglets on a Class I fixed-wing mini-UAV, aiming [...] Read more.

The aerodynamic performance of an aircraft can be significantly enhanced by incorporating wingtip devices, such as winglets, which primarily reduce lift-induced drag caused by wingtip vortices. This study introduces a comprehensive optimization framework for designing winglets on a Class I fixed-wing mini-UAV, aiming to maximize aerodynamic efficiency and operational performance. Using surrogate-based optimization (SBO) techniques, this research developed winglet geometries with varying geometric parameters such as length, cant angle, and sweep angle with their performance being evaluated through high-fidelity Computational Fluid Dynamics (CFD) simulations. These simulations utilized Reynolds-Averaged Navier–Stokes (RANS) equations coupled with the Spalart–Allmaras turbulence model to capture the intricate flow dynamics around the UAV in different flight phases. The integration of SBO techniques allowed for an efficient exploration of the design space while reducing computational costs associated with iterative high-fidelity simulations. In particular, the proposed SBO framework optimized the UAV’s aerodynamic characteristics, including lift-to-drag ratio and drag reduction, followed by a stability and control analyses to ensure balanced performance for the optimal configurations. Dynamic stability evaluations revealed improved flight characteristics, maintaining control across operational envelopes. The results demonstrated a significant improvement in aerodynamic coefficients, range, endurance, and reduction in battery consumption throughout the entire UAV operational envelope, underscoring the potential of innovative winglet designs to enhance UAV performance across diverse mission profiles. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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Review

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19 pages, 684 KiB

Open AccessReview

Advances in Composite Materials for Space Applications: A Comprehensive Literature Review

by Konstantinos Tserpes and Ioannis Sioutis

Aerospace 2025, 12(3), 215; https://doi.org/10.3390/aerospace12030215 - 7 Mar 2025

Cited by 2 | Viewed by 2178

Abstract

Space structures are perhaps the most complicated man-made structures due to their extremely harsh and complex operational environments. For these structures, materials serve as crucial technology drivers. Composite materials are increasingly used in space structures due to their specific mechanical properties, customizability, and [...] Read more.

Space structures are perhaps the most complicated man-made structures due to their extremely harsh and complex operational environments. For these structures, materials serve as crucial technology drivers. Composite materials are increasingly used in space structures due to their specific mechanical properties, customizability, and ability to easily acquire multifunctional and smart characteristics. This review critically examines the state of the art in composite materials application and the computational models used to design and analyze composite space structures. Full article

(This article belongs to the Special Issue 14th EASN International Conference on Innovation in Aviation & Space towards Sustainability Today & Tomorrow)

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