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A system design tool allowing to simulate the complete operation of a hybrid rocket engine is developed in this paper. The algorithm of the application is made in such a way that allows the simulation of an element, an ensemble of elements or all the elements constituting a hybrid space propulsion system. The objective is to simulate and predict the behavior of the engine at different conditions / configurations during the first pre-design phases. As the tool will be exclusively used during these phases, a balance between the duration of the simulation and its precision must be reached. Given these constraints, a maximum error of 30% between the experimental and the numerical results is considered adequate to validate the solution. The main parts of our HYCAT engine-characterized by a catalytic injection of oxidizer-are modeled and included in this tool: the mass flow rate regulator and the catalyst (feed and injection subsystems) through 0-D models; the combustion chamber with a 1.5-D model; and the nozzle through a 1-D model. An iterative method is employed to attain the pressure convergence in the combustion chamber between these three main parts of the engine whose corresponding system of equations is solved by a Newton-Raphson technique. Seven experiments performed on HYCAT are used to validate the results of the conceived tool. From all the performed simulations, only two of them present relative differences with the experiment above the defined threshold. The largest errors are produced for the fuel regression rate, the consumed mass of fuel, and the mixing ratio variables. The best agreements with the experiments are found for the simulations with the largest oxidizer mass fluxes (G ox >230 kg/m 2 /s) and where the mixing ratio is closer to the stoichiometric value, defining thus, the range of applicability of the system design tool.

International audience; A new Gas-Surface Interaction (GSI) model, based on the mass/energy balance at the fuel surface, is implemented in the ONERA Computational Fluid Dynamics (CFD) software CEDRE. The modelling aims at improving, by means of numerical simulations, the knowledge about aero-thermochemical phenomena in hybrid rocket engines. The two-equation turbulence model k-! Shear Stress Transport (SST) is used with wall blowing correction to represent properly the turbulent boundary layer structure which rules the convective transfer and depends on the fuel mass injection. The objective of the study is to validate spatially and temporally the GSI model for H2O2/HDPE HYCAT hybrid rocket engine using a catalytic injector. The validation process is based on the fuel regression rate comparison between numerical CFD results and experimental data from a reference case chosen in the testing campaign of the HYCAT hybrid rocket engine. Particularly, the temporal validation method considers the instantaneous fuel regression rate obtained by a ballistic reconstruction technique from measured instantaneous chamber pressure and oxidizer mass flow rate during the firing test.

International audience; CNES, the French Space Agency, has been leading for nearly six years intensive research on alternative green propellants for spacecrafts thrusters. More precisely, research has been focused on premixed monopropellant formulations based on state-of-the-art energetic materials and green chemistry approaches. The goal of this program is to provide an innovative propulsion system to replace standard hydrazine technology, demonstrating total breaking performance, low toxicity and high versatility. Hydrazine, mostly used in its anhydrous form as catalyzed monopropellant, is indeed an old and undoubtedly flight-proven product, but suffers from relatively poor propelling performance and from a high toxicity (both acute and suspected CMR). This paper describes the origins of the project and the main requirements we have imposed on ourselves. It also gives an overview of both the organization and the roadmap of the development plan, then concluding on the achievements and breakthroughs obtained to date.

International audience; Satellite attitude and orbit control manoeuvers are mostly realized by chemical thrusters, using catalytic decomposition of hydrazine. However, hydrazine is known for its carcinogenic and toxic effects and its use is thus threatened by the European chemical regulation REACh. A new monopropellant is therefore under development by CNES (the French Space Agency), and 3 prototypes are still in competition. The final choice of the best formulation will be based on real thruster tests. These new propellants are based on energetic ionic liquids, and the expected flame temperature is about 3000 K. To develop an optimized thruster demonstrator, numerical simulations, combining heat transfer and radiation in complex materials and diphasic behavior are necessary. Energetic ionic liquids have a very complex way of decomposing which explains why it is impossible to use current phase change models implemented in ONERA’s multiphysics code CEDRE. A new macroscopic combustion model is being developed and implemented in CEDRE following the phenomenology of solid homogeneous propellants. Simultaneously an experiment is prepared to observe the combustion of an isolated droplet, in order to measure its regression. This experiment is a proof of concept for the final experimental CNES’s setup GIMLI. This experiment will be validated on ethanol combustion and tested with the new family of green monopropellant.

International audience; Independent access to space is a key component of the European Space Policy. The competition is increasing in this area both for the full launching systems and the key subsystems. Cost effectiveness becomes the main driving factor. This paper describes the advancements performed in HYPROGEO, a 3-years cooperative R&D project funded by the European Commission’s Horizon 2020 program. HYPROGEO is a consortium of 14 European partners managed by Airbus Defence and Space Toulouse, bringing together complementary profiles from large space industry, SMEs till research institutes.

International audience; The EU H2020 HYPROGEO Project, coordinated by Airbus Defence and Space (Toulouse), called for the design and manufacture of two sets of catalytic injectors for a novel, isochoric hybrid rocket motor. The hybrid motor forms the basis of a propulsion system for future GEO/apogee-kick applications. The motor burns its fuel axially rather than radially and relies on a constant, vortical flow of hot oxygen for ignition and sustained combustion. The hot oxygen is provided by the rapid decomposition of hydrogen peroxide. Two aqueous concentrations were used: 87.5% for an intermediate motor, and 98% for the final breadboard design. Critical to success is the catalyst, referred to as PX1. This comprises a ceramic substrate and an active (catalytic) surface. On contact with hydrogen peroxide, oxygen and steam are liberated exothermically. The efficacy of PX1, used in combination with 98% concentration peroxide, was demonstrated in 2016.

International audience; Oxidizer injection plays a major role in the behaviour of hybrid rocket engines, especially regarding combustion efficiency and stability. This study aims to compare two firing tests with associated numerical simulations based on gaseous oxidizer axial or swirl injection through a catalyzer. The oxidizer and fuel couple used was H2O2 (87.5 %)/HDPE. Numerical 3D MILES (Monotone Integrated Large Eddy Simulation) simulations of both configurations were performed and analyzed regarding on one side the combustion efficiency influenced by propellants mixing, and on the other side the pressure oscillations provoked by the formation of large scale vortices in the aft-combustion chamber.

International audience; Hybrid propulsion technology suffers from low propulsive performances generally due to low combustion efficiency in regards to the other chemical propulsion systems. When hydrogen peroxide is used as oxidizer, one of the most promising ways to increase this efficiency combines a catalyst and a swirl injector in order to have an oxidizing gaseous stream and an improved mixing between the two propellants. A complementary solution to directly increase the propulsive performance consists of using hydrogen peroxide at higher concentration than the spatial grade (87.5%) which improves the theoretical specific impulse up to 12s for 98% H2 O2. This paper presents the development of a catalyst compatible with very high concentrated hydrogen peroxide (98%) and the firing tests performed with this catalyst coupled to a hybrid engine in order to highlight the increase in combustion efficiency.

Le dimensionnement préliminaire d’un propulseur hybride passe par une phase d’essais à échelle réduite afin de caractériser entre autre la loi de régression du couple oxydant/combustible envisagé pour remplir les besoins de la mission en terme de performances, durée de fonctionnement, etc. Afin de limiter le recours à ces campagnes expérimentales onéreuses et génératrices de délais pour les industriels, il est nécessaire de développer des outils numériques fiables permettant de prévoir rapidement, sous différentes conditions de fonctionnement et géométries de chambre de combustion, la loi de régression d’un couple oxydant/combustible. L’objectif de cette thèse est de proposer une modélisation monodimensionnelle du mécanisme de régression des combustibles liquéfiables. Cette classe de combustibles offre des vitesses de régression trois à cinq fois plus élevées que celles rencontrées avec les combustibles généralement utilisés en propulsion hybride (PBHT par exemple). Ce modèle se base alors sur le transport de la phase gazeuse et du film liquide se développant sur le combustible solide, la vitesse de régression dépendant des transferts de masse et d’énergie entre ces trois phases. Afin de valider cette approche et l’architecture du code Hydres conçu pour la résolution de ce modèle et la prévision des performances propulsives d’un moteur hybride, des campagnes expérimentales ont été réalisées sur les bancs d’essais Hycarre et Hycom. Ces essais ont également permis de développer une technique de mesure permettant l’obtention de la vitesse de régression instantanée du combustible, conduisant à la restitution de la loi de régression instantanée du couple oxydant/combustible. The preliminary design of a hybrid rocket engine requires lab-scale tests to characterize the regression law of the oxidizer/fuel pair intended to fulfil the mission needs in terms of performances, etc. To limit these costly and potentialy delaying experimental campaigns, it is necessary to develop reliable numerical tools to quickly predict the regression law of the oxidiser/fuel pair under different operating conditions and with different combustion chamber geometries. The objective of the thesis is to develop a one-dimensional model of the regression mechanism of liquefying fuels. These particular fuels offer regression rates three to five times higher than those found with classic polymers used in hybrid propulsion (eg. HTPB). The model is based on the transport of the gaseous flow and the liquid film which is developing along the solid fuel grain. The regression rate depends on mass and energy transfers between these three phases. To validate this approach and the Hydres numerical tool, specifically designed to solve this model and forecast the performances of a hybrid engine, experimental tests were performed with the Hycarre and Hycom facilities. These tests also allowed for the development of a technique to measure the instantaneous regression rate of the solid fuel, providing directly the instantaneous regression law of the oxidizer/fuel pair.

In the framework of the European H2020 HYPROGEO program, an innovative hybrid engine combustion chamber compatible with satellite requirements (constant thrust over a very long burning duration) has to be developed. To design such an engine, a first test rig, similar to the considered innovative combustion chamber, was designed and tested. The test campaign, performed under various operating conditions, enabled to demonstrate the catalytic ignitability of this new hybrid engine and the sustainment of a stable combustion. Additionally, the main influencing parameters on the fuel regression rate law have been identified.

Cette étude fait partie d'un projet commun CNES-ONERA dédié à la recherche sur les ergols verts pour la propulsion spatiale. La plupart des systèmes de contrôle d’attitude et d’orbite utilisent la décomposition catalytique de l’hydrazine, ce qui entraîne des problèmes de lits catalytiques et des contraintes de manipulation de l’hydrazine. Le CNES a proposé une nouvelle famille de monergol vert à base de liquides ioniques énergétiques. Ces HPGM (High Performance Green Monopropellant) proposent un système propulsif plus performant et moins toxique. L’objectif final du projet est d’initier thermiquement la décomposition liquide ionique énergétique afin d’éliminer les catalyseurs. L’objectif de la thèse est de caractériser l’allumage et la combustion de ces produits innovants. Ce travail présente dans un premier temps une approche expérimentale pour observer la décomposition de HPGM à l’aide de deux montages expérimentaux. Un montage de goutte isolée a permis la détection d’une pression seuil d’allumage pour les monergols d’étude, mais également une première approximation de la vitesse de régression. La réalisation d’un second montage en gouttière a étendu la gamme de pression pour cette mesure, tout en réduisant l’incertitude. Finalement, un modèle numérique a été proposé pour représenter la vitesse de régression des monergols d’étude et leur combustion en spray. This study is part of a joint CNES-ONERA project dedicated to research on green propellants for space propulsion. Most attitude and orbit control systems use the catalytic decomposition of hydrazine, which results in catalyst issue and hydrazine handling constraints. CNES has proposed a new family of green monergol based on energetic ionic liquids. These HPGMs (High Performance Green Monopropellant) offer a propulsion system more efficient and less toxic. The final objective of the project is to initiate thermally the ionic energy liquid decomposition in order to eliminate the catalysts. The aim of the thesis is to characterize the ignition and combustion of these innovative monopropellants. This work presents an experimental approach to observe the decomposition of HPGM using two experimental setups. An isolated droplet setup permits to detect of an ignition threshold pressure, but also a first approximation of the regression rate. A second gutter experimental setup extended the pressure range for this measurement, while reducing uncertainty. Finally, a numerical model has been proposed to represent the regression rate of these monopropellants and their combustion in spray.