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Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly...
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Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition)

A special issue of Aerospace (ISSN 2226-4310). This special issue belongs to the section "Astronautics & Space Science".

Deadline for manuscript submissions: closed (31 March 2026) | Viewed by 10716

Special Issue Editors

Dr. Filippo Maggi

E-Mail Website
Guest Editor
Dipartimento di Scienze e Tecnologie Aerospaziali, Politecnico di Milano, 20133 Milano, Italy
Interests: hybrid rocket propulsion; propellants; space propulsion; metal fuels
Special Issues, Collections and Topics in MDPI journals
Dr. Paravan Christian

E-Mail Website
Guest Editor
Dipartimento di Scienze e Tecnologie Aerospaziali, Politecnico di Milano, 20133 Milano, Italy
Interests: hybrid rocket propulsion; metal combustion; nano-sized materials; green propellants
Special Issues, Collections and Topics in MDPI journals
Dr. Stefania Carlotti

E-Mail Website
Guest Editor
Dipartimento di Scienze e Tecnologie Aerospaziali, Politecnico di Milano, 20133 Milano, Italy
Interests: hybrid rocket propulsion; green propellants; space propulsion

Special Issue Information

Dear Colleagues,

The pursuit of increased sustainability permeates research in many different fields, including space industry and propulsion. While many propulsion systems still rely on performing solutions that offer a strong heritage but feature high toxicity, space agencies have accelerated the development of new green propellants and technologies. Green propellants aim to combine performance with safer, more eco-friendly, and more sustainable life cycles.

Following the first Special Issue on this topic, edited by Prof. Filippo Maggi and Prof. Christian Paravan, “Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition)” aims to collect contributions on the latest advancements and future challenges in this rapidly evolving field.

We invite submissions in the field of thermochemical propulsion covering experimental, numerical, and theoretical research on green propellants for launchers and in-space operations. Potential topics include, but are not limited to, the following:

  • Development of non-toxic solid, liquid, and hybrid propellants, including the use of eco-friendly materials, advanced composites, and 3D-printed materials.
  • Studies exploring the design, development, and optimization of green thermochemical propulsion, including AI-assisted investigations.
  • Life cycle assessments of green propulsion technologies on environment and humans, from manufacturing to disposal.
  • Status advancement/final conclusions of projects concerning green propulsion topics.
  • Literature surveys, trade-off analyses, and evaluation studies on green propulsion solutions.

Dr. Filippo Maggi
Dr. Paravan Christian
Dr. Stefania Carlotti
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 250 words) can be sent to the Editorial Office for assessment.

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 propulsion
  • solid propulsion
  • liquid propulsion
  • hybrid propulsion
  • propellant
  • pollution
  • environmental impact
  • space industry
  • clean technologies

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Related Special Issue

Published Papers (7 papers)

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Research

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29 pages, 3415 KB  
Article
Neural Network-Based Optimization of Hybrid Rocket Design for Modular Multistage Launch Vehicle
by Paolo Maria Zolla, Alessandro Zavoli, Mario Tindaro Migliorino and Daniele Bianchi
Aerospace 2026, 13(4), 374; https://doi.org/10.3390/aerospace13040374 - 16 Apr 2026
Abstract
In this paper, an integrated optimization is carried out to find the optimal hybrid rocket engine design for a modular multistage launch vehicle targeting a 500 km polar circular orbit. A single hybrid rocket engine unit is reused across the whole launch vehicle, [...] Read more.
In this paper, an integrated optimization is carried out to find the optimal hybrid rocket engine design for a modular multistage launch vehicle targeting a 500 km polar circular orbit. A single hybrid rocket engine unit is reused across the whole launch vehicle, with each stage constituted by a cluster of a specified number of units. Only the nozzle exit diameter of the units is allowed to change across each stage. This clustering approach is aimed at reducing the costs of the launch vehicle and at simplifying the optimization procedure. After a brief mission analysis based on Tsiolkovsky’s equation, a three-stage configuration is chosen for the launch vehicle, employing 16, 4, and 1 engine units for, respectively, the first, second, and third stage. A neural network-based surrogate model is employed to approximate the complex hybrid rocket internal ballistics, with the aim to reduce the computational cost of the optimization process. The surrogate model is trained to map a reduced number of design parameters to the performance and mass budget of a single engine unit using data from a 0-D hybrid rocket engine model. The accuracy of the trained network in predicting crucial features is then assessed. Finally, the trained network is integrated into a multidisciplinary optimization process. The aim is to identify the optimal rocket engine design and launch vehicle ascent trajectory that maximize the payload capacity to the target orbit. Full article
(This article belongs to the Special Issue Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition))
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22 pages, 2174 KB  
Article
Simulation of bi-Propellant Reaction Control Thrusters Based on Nitrous Oxide and Hydrocarbons
by Stefan Fechter, Tobias Ecker and Tim Horchler
Aerospace 2026, 13(2), 131; https://doi.org/10.3390/aerospace13020131 - 30 Jan 2026
Viewed by 422
Abstract
To replace highly toxic hydrazin-driven reaction control systems, a number of non-toxic alternatives are under development. These are usually referred to as “green propellants”. One candidate is the bi-propellant combination of nitrous oxide and hydrocarbons that combine good storability with a comparatively high [...] Read more.
To replace highly toxic hydrazin-driven reaction control systems, a number of non-toxic alternatives are under development. These are usually referred to as “green propellants”. One candidate is the bi-propellant combination of nitrous oxide and hydrocarbons that combine good storability with a comparatively high specific impulse (ISP) at a medium to low system complexity level compared to existing hydrazine thrusters. This propellant combination was chosen because of experimentally available results with C2H4-N2O thrusters as validation data. One advantage of this fuel/oxidizer combination is that both gases are self-pressurant and that they can be used as monopropellants at a lower specific impulse ISP with reduced model complexity. This helps the design of the propulsion system on satellites. A detailed numerical simulation of a representative thruster based on the fuel combination ethylene and nitrous oxide is presented. The numerical model is set up with a suitable kinetic reaction mechanism for the simulation of the reactive mixture in the combustion chamber. It is validated against experimental data available in the literature. Full article
(This article belongs to the Special Issue Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition))
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13 pages, 3970 KB  
Article
Evaluation of Marine Plastic Combustion Characteristics and Its Application as Solid Fuel for Hybrid Rockets
by Moe Ohno, Yoshito Takahashi, Kenichi Takahashi and Toshifumi Sakata
Aerospace 2026, 13(1), 7; https://doi.org/10.3390/aerospace13010007 - 22 Dec 2025
Viewed by 399
Abstract
Growing demand for small satellite launches has increased the need for low-cost and environmentally sustainable propulsion systems. Hybrid rockets have garnered attention as a promising alternative, but most solid fuels are petroleum-derived, contributing to resource depletion and greenhouse gas emissions. This study evaluated [...] Read more.
Growing demand for small satellite launches has increased the need for low-cost and environmentally sustainable propulsion systems. Hybrid rockets have garnered attention as a promising alternative, but most solid fuels are petroleum-derived, contributing to resource depletion and greenhouse gas emissions. This study evaluated the potential of polyethylene recovered from marine plastic waste (Marine Plastics) as a solid fuel for hybrid rockets. For thermal and elemental analyses, commercial high-density polyethylene pellets (Standard HDPEs) were used as a reference, while commercial HDPE cylindrical material (Combustion-grade HDPE) was used for combustion tests. Differential scanning calorimetry and thermogravimetric analyses revealed that Marine Plastics exhibited a melting point of approximately 403 K, comparable to Standard HDPE, with slightly lower thermal stability. Elemental analysis indicated the absence of oxygen atoms, suggesting minimal UV-induced degradation. Combustion tests demonstrated that both Marine Plastics and Combustion-grade HDPE achieved about 60% of the theoretical characteristic velocity, with Marine Plastics exhibiting a slightly higher regression rate. Furthermore, Marine Plastics contained a small amount of sodium chloride, suggesting the potential formation of hydrogen chloride during combustion. These results experimentally confirm that Marine Plastics possess thermal and combustion properties comparable to commercial HDPE, indicating their potential as an alternative solid fuel for hybrid rockets. Full article
(This article belongs to the Special Issue Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition))
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26 pages, 4941 KB  
Article
Experimental Investigation of Hydrogen Peroxide and Nitrous Oxide in a 1-Newton Catalyst-Based Monopropellant Research Thruster
by Florian Merz, Till Hörger, Johan Steelant, Felix Lauck and Christoph Kirchberger
Aerospace 2025, 12(9), 835; https://doi.org/10.3390/aerospace12090835 - 17 Sep 2025
Cited by 3 | Viewed by 2373
Abstract
As part of the GreenRAIM activity of the European Space Agency (ESA), an extensive test campaign involving various monopropellants was undertaken. In this work, design and test results of an additively manufactured 1-Newton monopropellant thruster are shown. The detailed design of the thruster [...] Read more.
As part of the GreenRAIM activity of the European Space Agency (ESA), an extensive test campaign involving various monopropellants was undertaken. In this work, design and test results of an additively manufactured 1-Newton monopropellant thruster are shown. The detailed design of the thruster and the experimental setup are presented. The first part of the test campaign was conducted with 98 wt.% hydrogen peroxide as the propellant and a commercially available Pt/Al2O3 catalyst. The second part was carried out with the same thruster but using nitrous oxide as the propellant and an iridium-based catalyst. The test data acquired was used to validate a comprehensive, generic model for monopropellant thrusters within the simulation software EcosimPro/ESPSS v3.7, which was developed within the activity. Full article
(This article belongs to the Special Issue Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition))
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14 pages, 2013 KB  
Article
Lab-Scale Thermal Decomposition of Hydrogen Peroxide as Green Propellant over Low-Cost Catalysts Based on Copper Deposited on Different Supports
by Imane Remissa, Ahmed E. S. Nosseir, Amit Tiwari, Ahmed Bachar, Assia Mabrouk and Rachid Amrousse
Aerospace 2025, 12(5), 440; https://doi.org/10.3390/aerospace12050440 - 15 May 2025
Viewed by 2408
Abstract
The thermal decomposition of hydrogen peroxide (H2O2) as a promising green propellant was performed over free-noble metallic-based catalysts deposited on abundant supports. A 30% (w/w) H2O2 liquid was decomposed over 1 wt.% [...] Read more.
The thermal decomposition of hydrogen peroxide (H2O2) as a promising green propellant was performed over free-noble metallic-based catalysts deposited on abundant supports. A 30% (w/w) H2O2 liquid was decomposed over 1 wt.% of copper-based catalysts deposited on three different supports: γ-alumina, graphite and monocrystal clay. In this research work, the catalytic performance of the thermal decomposition of H2O2 was carried out by measuring the differential pressure (ΔP) versus time at initial constant temperatures and, for the first time, by the DTA-TG technique and by the DIP-MS technique at atmospheric pressure. The obtained preliminary results showed that copper deposited on alumina and on graphite are promising catalysts for the decomposition of the H2O2 liquid propellant. Moreover, the natural clay can be valorized on the thermal decomposition of H2O2 due to its high resistivity and high surface area. The N2-physisorption technique and scanning electron microscopy technique were used to characterize the effect of the texture properties on the decomposition and to understand the morphological characteristics of the catalyst. Full article
(This article belongs to the Special Issue Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition))
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18 pages, 8128 KB  
Article
Investigation of Performance Stability of a Nytrox Hybrid Rocket Propulsion System
by Shih-Sin Wei, Jui-Cheng Hsu, Hsi-Yu Tso and Jong-Shinn Wu
Aerospace 2025, 12(5), 372; https://doi.org/10.3390/aerospace12050372 - 25 Apr 2025
Viewed by 2415
Abstract
Nitrous oxide is a highly suitable oxidizer for hybrid rockets due to its self-pressurizing properties, moderate cost, and high accessibility. However, its vapor pressure and density are highly dependent on ambient temperature, requiring careful consideration of temperature variations in real applications. To mitigate [...] Read more.
Nitrous oxide is a highly suitable oxidizer for hybrid rockets due to its self-pressurizing properties, moderate cost, and high accessibility. However, its vapor pressure and density are highly dependent on ambient temperature, requiring careful consideration of temperature variations in real applications. To mitigate this issue, an oxidizer called Nytrox was produced by adding a small fraction of oxygen to bulk nitrous oxide. This modification enables the hybrid rocket propulsion system to maintain a nearly constant average thrust and total impulse across a wide range of ambient temperatures. A series of 7 s hot-fire tests of a small Nytrox/polypropylene hybrid rocket engine operating at ~60 barA of running tank pressure demonstrated a consistent average thrust of 45.3 ± 0.7 kgf and a total impulse of 307.6 ± 3.9 kgf·s within a N2O temperature range of 5.9–22.6 °C, compared to highly varying values of the N2O/polypropylene one within a N2O temperature range of 10.8–29.8 °C. Furthermore, the specific impulse of the Nytrox hybrid rocket engine increases mildly with decreasing temperature because of the increasing amount of added oxygen that benefits the combustion for generating the thrust. Full article
(This article belongs to the Special Issue Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition))
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Review

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17 pages, 2460 KB  
Review
A Case Study on Current Developments and Future Direction of Hypergolic Propellant Systems
by Nadir Yilmaz, Michael Arowolo and Alpaslan Atmanli
Aerospace 2025, 12(12), 1099; https://doi.org/10.3390/aerospace12121099 - 10 Dec 2025
Viewed by 1788
Abstract
Hypergolic propellants are easy to start and restart, stay liquid at normal temperatures, and avoid storage issues, making them ideal for spacecraft propulsion systems. However, conventional hypergolic propellants are toxic, prompting the need to find safer alternatives and/or reduce their toxicity. The growing [...] Read more.
Hypergolic propellants are easy to start and restart, stay liquid at normal temperatures, and avoid storage issues, making them ideal for spacecraft propulsion systems. However, conventional hypergolic propellants are toxic, prompting the need to find safer alternatives and/or reduce their toxicity. The growing demand for propulsion in advancing space technology has driven research into high-performance, sustainable, and environmentally safe hypergolic propellant types. At this point, research into new hypergolic fuels that can replace traditional rocket propellant designs is highly significant. In this study, the current status of hypergolic fuels is discussed, and new technological developments and future projections are examined. Several approaches have been studied in an effort to create a high-performance hypergolic propellant system. These include modifications such as changing the structure of propulsion systems, altering propellant constituents, and adding additives. All these conditions were found to bear a profound effect on the specific impulse, density impulse, heat energy, and ignition delay of the propellants. Full article
(This article belongs to the Special Issue Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions (2nd Edition))
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