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Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of...
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Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future

A special issue of Aerospace (ISSN 2226-4310).

Deadline for manuscript submissions: 28 February 2025 | Viewed by 11134

Special Issue Editors

Dr. Giacomo Silvagni

E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Bologna, 47121 Forli, Italy
Interests: internal combustion engines; low tempearture combustions; sustainable aeronautical and space propulsion systems; rapid control prototyping; sustainable mobility; hydrogen based-solutions for aeronautics; sustainable hydrogen-based energy plants
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Vittorio Ravaglioli

E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Bologna, 47121 Forli, Italy
Interests: internal combustion engines; combustion control; testing; hybrid systems; hydrogen combustion
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Green hydrogen, produced through renewable energy sources, offers a promising alternative to traditional fossil fuels for propulsion systems in the aerospace mobility sector. Thanks to the chemical composition of the fuel itself, hydrogen holds the key to achieving the ambitious environmental targets of moving toward zero-carbon air mobility and mitigating the impact of aviation on climate change. By embracing green hydrogen technologies, aerospace industry stakeholders can pave the way for a cleaner and sustainable future for air travel and space exploration. From fuel cell technologies to optimized conventional propulsion systems, the integration of green hydrogen in aerospace not only promises enhanced efficiency and performance but also contributes to global efforts in sustainability and environmental stewardship. This Special Issue aims to explore the transformative potential of green hydrogen as a sustainable fuel for both aviation and the space transportation sector. The scope of the Special Issue encompasses a wide range of topics, including the production and distribution of green hydrogen, innovation in hydrogen storage technologies, advances in hydrogen fuel cell technology for propulsion and power generation, the management of high-power-to-weight-ratio renewable-fueled propulsion systems, the optimization and design of hydrogen propulsion systems, the environmental impact assessment of hydrogen technology, policy and regulatory aspects, and case studies on its applications in aerospace mobility.

The scope of the Special Issue will include, but is not limited to, the following topics:

  • An overview of green hydrogen technologies for aerospace mobility, encompassing both aviation and space segment.
  • Advances in hydrogen fuel cell technology and materials for aerospace applications.
  • The optimization and design of green hydrogen propulsion systems for aerospace applications.
  • Comparisons of experimental data and case studies on the use of green hydrogen propulsion systems.
  • The management of high power-to-weight ratio renewable-fueled propulsion systems.
  • The integration of green hydrogen propulsion systems with aircraft and subsystems.
  • The environmental impact assessment of green hydrogen propulsion in the atmosphere and in commercial space missions, including emission reduction and planetary protection.
  • The production, storage, and distribution of green hydrogen for air and space applications.
  • The policy, regulatory, and economic aspects of green hydrogen adoption in the aerospace industry.
  • Case studies and demonstrations of green hydrogen applications in aerospace mobility, including both the aviation and commercial space markets. 

We welcome original research articles and review articles that address any of the above topics or related areas. We look forward to receiving high-quality submissions that contribute to the advancement of the field of green hydrogen technologies and sustainable aerospace mobility.

Dr. Giacomo Silvagni
Dr. Vittorio Ravaglioli
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Aerospace is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • green hydrogen
  • aerospace mobility
  • sustainable fuel
  • aviation
  • space
  • hydrogen fuel cell
  • propulsion systems
  • environmental impact
  • production and distribution
  • policy and regulation

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Published Papers (9 papers)

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Research

31 pages, 1665 KiB  
Article
Retrofitted Hydrogen-Electric Propulsion Aircraft: Performance Simulation of Critical Operating Conditions
by Wim Lammen, Pieter-Jan Dewitte and Elise Scheers
Aerospace 2025, 12(2), 95; https://doi.org/10.3390/aerospace12020095 - 27 Jan 2025
Viewed by 312
Abstract
Retrofitting regional turboprop aircraft with hydrogen (H2)-electric powertrains, using fuel cell systems (FCSs), has gained interest in the last decade. This type of powertrain eliminates CO2, NOx, and fine particle emissions during flight, as FCSs only emit water. In [...] Read more.
Retrofitting regional turboprop aircraft with hydrogen (H2)-electric powertrains, using fuel cell systems (FCSs), has gained interest in the last decade. This type of powertrain eliminates CO2, NOx, and fine particle emissions during flight, as FCSs only emit water. In this context, the “Hydrogen Aircraft Powertrain and Storage Systems” (HAPSS) project targets the development of a H2-electric propulsion system for retrofitting Dash 8-300 series aircraft. The purpose of the study described in this paper is to analyze the performance of the retrofitted H2-electric aircraft during critical operating conditions. Takeoff, as well as climb, cruise and go-around performances are addressed. The NLR in-house tool MASS (Mission, Aircraft and Systems Simulation) was used for the performance analyses. The results show that the retrofitted H2-electric aircraft has a slightly increased takeoff distance compared to the Dash 8-300 and it requires a maximum rated shaft power of 1.9 MW per propeller. A total rated FCS output power of 3.1 MW is sufficient to satisfy the takeoff requirements, at the cost of lower cruise altitude and reduced cruise speed as compared to the Dash 8-300. Furthermore, a higher-rated FCS is required to achieve the climb performance required for the typical climb profile of the Dash 8-300. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
23 pages, 2610 KiB  
Article
Conceptual Design and Aerostructural Trade-Offs in Hydrogen- Powered Strut-Braced Wing Aircraft: Insights into Dry and Wet Ultra-High Aspect Ratio Wings
by Nicolas F. M. Wahler, Yiyuan Ma and Ali Elham
Aerospace 2025, 12(2), 77; https://doi.org/10.3390/aerospace12020077 - 23 Jan 2025
Viewed by 478
Abstract
Stringent sustainability goals are set for the next generation of aircraft. A promising novel airframe concept is the ultra-high aspect ratio Strut-Braced Wing (SBW) aircraft. Hydrogen-based concepts are active contenders for sustainable propulsion. The study compares a medium-range Liquid Hydrogen (LH2) to a [...] Read more.
Stringent sustainability goals are set for the next generation of aircraft. A promising novel airframe concept is the ultra-high aspect ratio Strut-Braced Wing (SBW) aircraft. Hydrogen-based concepts are active contenders for sustainable propulsion. The study compares a medium-range Liquid Hydrogen (LH2) to a kerosene-based SBW aircraft designed with the same top-level requirements. For both concepts, overall design, operating costs, and emissions are evaluated using the tool SUAVE. Furthermore, aerostructural optimizations are performed for the wing mass of SBW aircraft with and without wing-based fuel tanks. Results show that the main difference in the design point definition results from a higher zero-lift drag due to an extended fuselage housing the LH2 tanks, with a small reduction in the required wing loading. Structural mass increases of the LH2 aircraft due to additional tanks and fuselage structure are mostly offset by fuel mass savings. While the fuel mass accounts for nearly 25% of the kerosene design’s Maximum Take-Off Mass (MTOM), this reduces to 10% for the LH2 design. The LH2 aircraft has 16% higher operating costs with emission levels reduced to 57–82% of the kerosene aircraft, depending on the LH2 production method. For static loads, the absence of fuel acting as bending moment relief in the wing results in an increase in wing structural mass. However, the inclusion of roll rate requirements causes large wing mass increases for both concepts, significantly outweighing dry wing penalties. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
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20 pages, 2844 KiB  
Article
Rheology and Stability of Hydrocarbon-Based Gelled Fuels for Airbreathing Applications
by Simone Dell’Acqua, Francesco Morando, Stefania Carlotti and Filippo Maggi
Aerospace 2025, 12(1), 49; https://doi.org/10.3390/aerospace12010049 - 13 Jan 2025
Viewed by 553
Abstract
Gelled fuels are rheologically complex, non-Newtonian fluids. They combine the benefits of both liquid and solid states, reducing risks of leakage, spilling, and sloshing during storage while maintaining the ability to be sprayed inside a combustion chamber. Additionally, suspending energetic particles, such as [...] Read more.
Gelled fuels are rheologically complex, non-Newtonian fluids. They combine the benefits of both liquid and solid states, reducing risks of leakage, spilling, and sloshing during storage while maintaining the ability to be sprayed inside a combustion chamber. Additionally, suspending energetic particles, such as metal powders of aluminum and boron, can significantly enhance their energy density compared to conventional liquid fuels. In this study, several kerosene-based and ethanol-based formulations were experimentally investigated, using both organic and inorganic gelling agents. The compositions were optimized in terms of the gellant amount and manufacturing process. Some of the most promising gellants for kerosene include fatty acids, such as Thixcin® R or THIXATROL® ST, and metallic soaps, such as aluminum stearate and zinc stearate. The effects of various co-solvents were assessed, including ketones (methyl isoamyl ketone, methyl ethyl ketone, and acetone) and alcohols (ethanol and octadecanol). Sugar polymers like hydroxypropyl cellulose were tested as gelling agents for ethanol. A preliminary rheological analysis was conducted to characterize their behavior at rest and under shear stress. Finally, a novel approach was introduced to study the stability of the gels under vibration, which was derived from a realistic mission profile of a ramjet. Finally, the ideal gravimetric specific impulse was evaluated through ideal thermochemical computations. The results showed that promising formulations can be found in both kerosene-based and ethanol-based gels. Such compositions are of interest in practical airbreathing applications as they have demonstrated excellent stability under vibration, ideal combustion properties, and pronounced shear-thinning behavior. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
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18 pages, 7396 KiB  
Article
Design and Performance Optimization of a Radial Turbine Using Hydrogen Combustion Products
by Pengfei Su, Weifeng He, Abdalazeem Adam, Omer Musa, Wang Chen and Zeyu Lou
Aerospace 2024, 11(12), 1051; https://doi.org/10.3390/aerospace11121051 - 23 Dec 2024
Viewed by 857
Abstract
The combustion of hydrogen increases the water content of the combustion products, affecting the aerodynamic performance of turbines using hydrogen as a fuel. This study aims to design a radial turbine using the differential evolution (DE) algorithm to improve its characteristics and optimize [...] Read more.
The combustion of hydrogen increases the water content of the combustion products, affecting the aerodynamic performance of turbines using hydrogen as a fuel. This study aims to design a radial turbine using the differential evolution (DE) algorithm to improve its characteristics and optimize its aerodynamic performance through an orthogonal experiment and analysis of means (ANOM). The effects of varying water content in combustion products, ranging from 12% to 22%, on the performance of the radial turbine are also investigated. After optimization, the total–static efficiency of the radial turbine increased to 89.12%, which was 1.59% higher than the preliminary design. The study found that flow loss in the impeller primarily occurred at the leading edge, trailing edge, and the inlet of the suction surface tip and outlet. With a 10% increase in water content, the enthalpy dropped, Mach number increased, and turbine power increased by 4.64%, 1.71%, and 2.41%, respectively. However, the total static efficiency and mass flow rate decreased by 0.71% and 2.13%, respectively. These findings indicate that higher water content in hydrogen combustion products enhances the turbine’s output power while reducing the combustion products’ mass flow rate. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
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11 pages, 3469 KiB  
Article
Resolving Visible Emission Lines in Hydrogen Diffusion Flames
by Muyi Pan, Xuanqi Liu, Yufeng Lai, Yuchen Zhang and Yang Zhang
Aerospace 2024, 11(12), 983; https://doi.org/10.3390/aerospace11120983 - 28 Nov 2024
Viewed by 582
Abstract
The hydrogen diffusion flame is commonly described as difficult to see in the visible range. However, even in controlled laboratory conditions with careful imaging, the flame appears reddish. Previous research has reported a variety of colours generated from hydrogen flames. Some researchers believe [...] Read more.
The hydrogen diffusion flame is commonly described as difficult to see in the visible range. However, even in controlled laboratory conditions with careful imaging, the flame appears reddish. Previous research has reported a variety of colours generated from hydrogen flames. Some researchers believe that the visible colour is due to sodium in airborne dust. Other studies suggest the flame colour is caused by the vibration–rotation band of water vapour. In addition, H−α emits radiance in the visible range; therefore, the visible colour of the hydrogen flame could be contributed from the H−α emission. Nevertheless, a definitive conclusion to explain the visible reddish colour of the hydrogen flame is lacking. This paper reports precisely instrumented spectroscopic imaging tests, calibration, and data processing in order to resolve the spectral lines in the red colour zone (580–700 nm). This study used a spectrograph and a DSLR camera to capture the spectrum of hydrogen diffusion flames under different co-flow conditions. The values of emission lines in this range were compared with the databases provided by HITRAN molecular spectroscopy and the National Institute of Standards and Technology (NIST). The results of this study show that H−α emission is highly likely to appear in a hydrogen diffusion flame, which contradicts the previous hypothesis. This work may provide new insight into hydrogen-based combustion. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
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26 pages, 5286 KiB  
Article
0-D Dynamic Performance Simulation of Hydrogen-Fueled Turboshaft Engine
by Mattia Magnani, Giacomo Silvagni, Vittorio Ravaglioli and Fabrizio Ponti
Aerospace 2024, 11(10), 816; https://doi.org/10.3390/aerospace11100816 - 6 Oct 2024
Viewed by 1095
Abstract
In the last few decades, the problem of pollution resulting from human activities has pushed research toward zero or net-zero carbon solutions for transportation. The main objective of this paper is to perform a preliminary performance assessment of the use of hydrogen in [...] Read more.
In the last few decades, the problem of pollution resulting from human activities has pushed research toward zero or net-zero carbon solutions for transportation. The main objective of this paper is to perform a preliminary performance assessment of the use of hydrogen in conventional turbine engines for aeronautical applications. A 0-D dynamic model of the Allison 250 C-18 turboshaft engine was designed and validated using conventional aviation fuel (kerosene Jet A-1). A dedicated, experimental campaign covering the whole engine operating range was conducted to obtain the thermodynamic data for the main engine components: the compressor, lateral ducts, combustion chamber, high- and low-pressure turbines, and exhaust nozzle. A theoretical chemical combustion model based on the NASA-CEA database was used to account for the energy conversion process in the combustor and to obtain quantitative feedback from the model in terms of fuel consumption. Once the engine and the turbomachinery of the engine were characterized, the work focused on designing a 0-D dynamic engine model based on the engine’s characteristics and the experimental data using the MATLAB/Simulink environment, which is capable of replicating the real engine behavior. Then, the 0-D dynamic model was validated by the acquired data and used to predict the engine’s performance with a different throttle profile (close to realistic request profiles during flight). Finally, the 0-D dynamic engine model was used to predict the performance of the engine using hydrogen as the input of the theoretical combustion model. The outputs of simulations running conventional kerosene Jet A-1 and hydrogen using different throttle profiles were compared, showing up to a 64% reduction in fuel mass flow rate and a 3% increase in thermal efficiency using hydrogen in flight-like conditions. The results confirm the potential of hydrogen as a suitable alternative fuel for small turbine engines and aircraft. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
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31 pages, 25814 KiB  
Article
Experimental Pressure Gain Analysis of Pulsed Detonation Engine
by Alina Bogoi, Tudor Cuciuc, Andrei Vlad Cojocea, Mihnea Gall, Ionuț Porumbel and Constantin Eusebiu Hrițcu
Aerospace 2024, 11(6), 465; https://doi.org/10.3390/aerospace11060465 - 11 Jun 2024
Cited by 3 | Viewed by 1409
Abstract
A pulsed detonation chamber (PDC) equipped with Hartmann–Sprenger resonators has been designed and tested for both Hydrogen/air and Hydrogen/Oxygen mixtures. A full-factorial experimental campaign employing four factors with four levels each has been carried out for both mixtures. Instantaneous static pressure has been [...] Read more.
A pulsed detonation chamber (PDC) equipped with Hartmann–Sprenger resonators has been designed and tested for both Hydrogen/air and Hydrogen/Oxygen mixtures. A full-factorial experimental campaign employing four factors with four levels each has been carried out for both mixtures. Instantaneous static pressure has been measured at two locations on the exhaust pipe of the PDC, and the signal has been processed to extract the average and maximum cycle pressures and the operating frequency of the spark plug. The PDC has been shown to be able to reach sustained detonation cycles over a length below 200 mm, measured from the spark plug to the first pressure sensor. The optimal regimes for both air and Oxygen operation have been determined, and the influence of the four factors on the responses is discussed. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
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21 pages, 7552 KiB  
Article
Studies Concerning Electrical Repowering of a Training Airplane Using Hydrogen Fuel Cells
by Jenica-Ileana Corcau, Liviu Dinca, Grigore Cican, Adriana Ionescu, Mihai Negru, Radu Bogateanu and Andra-Adelina Cucu
Aerospace 2024, 11(3), 218; https://doi.org/10.3390/aerospace11030218 - 11 Mar 2024
Cited by 2 | Viewed by 2150
Abstract
The increase in greenhouse gas emissions, as well as the risk of fossil fuel depletion, has prompted a transition to electric transportation. The European Union aims to substantially reduce pollutant emissions by 2035 through the use of renewable energies. In aviation, this transition [...] Read more.
The increase in greenhouse gas emissions, as well as the risk of fossil fuel depletion, has prompted a transition to electric transportation. The European Union aims to substantially reduce pollutant emissions by 2035 through the use of renewable energies. In aviation, this transition is particularly challenging, mainly due to the weight of onboard equipment. Traditional electric motors with radial magnetic flux have been replaced by axial magnetic flux motors with reduced weight and volume, high efficiency, power, and torque. These motors were initially developed for electric vehicles with in-wheel motors but have been adapted for aviation without modifications. Worldwide, there are already companies developing propulsion systems for various aircraft categories using such electric motors. One category of aircraft that could benefit from this electric motor development is traditionally constructed training aircraft with significant remaining flight resource. Electric repowering would allow their continued use for pilot training, preparing them for future electrically powered aircraft. This article presents a study on the feasibility of repowering a classic training aircraft with an electric propulsion system. The possibilities of using either a battery or a hybrid source composed of a battery and a fuel cell as an energy source are explored. The goal is to utilize components already in production to eliminate the research phase for specific aircraft components. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
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25 pages, 8491 KiB  
Article
Design of a Hydrogen Aircraft for Zero Persistent Contrails
by David I. Barton, Cesare A. Hall and Matthew K. Oldfield
Aerospace 2023, 10(8), 688; https://doi.org/10.3390/aerospace10080688 - 31 Jul 2023
Cited by 8 | Viewed by 2788
Abstract
Contrails are responsible for a significant proportion of aviation’s climate impact. This paper uses data from the European Centre for Medium-Range Weather Forecasts to identify the altitudes and latitudes where formed contrails will not persist. This reveals that long-lived contrails may be prevented [...] Read more.
Contrails are responsible for a significant proportion of aviation’s climate impact. This paper uses data from the European Centre for Medium-Range Weather Forecasts to identify the altitudes and latitudes where formed contrails will not persist. This reveals that long-lived contrails may be prevented by flying lower in equatorial regions and higher in non-equatorial regions. Subsequently, it is found that the lighter fuel and reduced seating capacity of hydrogen-powered aircraft lead to a reduced aircraft weight, which increases the optimal operating altitude by about 2 km. In non-equatorial regions, this would lift the aircraft’s cruise point into the region where long-lived contrails do not persist, unlocking hydrogen-powered, low-contrails operation. The baseline aircraft considered is an A320 retrofitted with in-fuselage hydrogen tanks. The impacts of the higher-altitude cruise on fuel burn and the benefits unlocked by optimizing the wing geometry for this altitude are estimated using a drag model based on theory proposed by Cavcar, Lock, and Mason, and verified against existing aircraft. The weight penalty associated with optimizing wing geometry for this altitude is estimated using Torenbeek’s correlation. It is found that thinner wings with higher aspect ratios are particularly suited to this high-altitude operation and are enabled by the relaxation of the requirement to store fuel in the wings. An example aircraft design for the non-equatorial region is provided, which cruises at a 14 km altitude at Mach 0.75 with a less than 1% average probability of generating long-lived contrails when operating at latitudes more than 35° from the equator. Compared to the A320, this concept design is estimated to have a 20% greater cruise lift–drag ratio, due to the 33% thinner wings with a 50% larger aspect ratio, enabling just 5% more energy use per passenger-km, despite fitting 40% fewer seats. Full article
(This article belongs to the Special Issue Revolutionizing Aerospace Mobility: Green Hydrogen As the Sustainable Fuel of the Future)
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