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International audience; In this work, a novel approach to increase the performance of a Hybrid Rocket Engine (HRE) by approximating any idealized fuel port geometry by steps inside the fuel grain is proposed. This work serves as a first investigation into the effect of single steps inside the fuel grains of a typical HRE. In numerical simulations, it is shown that forward- and backward-facing steps have the potential to increase the average regression rate as they promote the turbulence and heat transfer inside the turbulent boundary layer. Both types of steps are more effective at lower oxidizer mass fluxes. Finally, as a first estimation, a set of best practices for the distribution of steps along a profile could be derived.

Unlike classical pyrotechnical solutions such as black powders, laser ignition is a non-intrusive, scalable method making it an interesting ignition technique for solid propellants in academia. When studies focus on the solid propellant gas flow, the shape of the burning surface becomes crucial. It is usually necessary to have a burning surface as flat as possible. The laser ignition delay of solid propellants follows a power law function of the laser heat flux. Because this law is not linear, ignition time varies strongly even for small laser irradiance variations. More precisely, the lower the laser irradiance, the more difficult it is to obtain a plane ignition. In this paper we present a calculation method to estimate the shape of the burning surface for a solid propellant sample based on the laser irradiance spatial distribution. For this purpose, a one-dimensional surface heating model is implemented together with a solid-propellant ignition model. This allows to calculate a local ignition delay as a function of the incident heat flux. The Gaussian spatial heat flux distribution has been discretised over the beam radius, and an ignition time calculation is performed for each spatial discretisation point. Considering that the solid propellant is a good thermal insulator, the ignition delay is independently calculated for each radius. Finally, the temporal evolution of the burning surface is determined, taking into account the flame propagation over the propellant surface. These results show the evolution of the surface with different laser parameters (i.e. beam size and power). This allows us to define, based on the laser irradiance distribution, a radius limit for which planar ignition can be assumed. An experimental setup is presented to measure the shape of the burning surface as a function of heat flux distribution for low laser irradiance. The calculation method is demonstrated with physical properties representative of a classical AP/HTPB research propellant composition. The approach is very promising to optimize ignition conditions for future experiments that require planar ignition.

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; The trend towards smaller satellites and mega-constellations has enormously changed the space sector and its utilisation in the last decades, allowing new players to enter the market and introducing stringent requirements to enable a variety of novel applications. Alongside, also the launcher market is undergoing a transformation epoch: the development, manufacturing, and integration of launcher systems is being shifted from the hands of governmental institutions to commercial industry. Moreover, nations like Unites States, China, India, and New Zealand are increasing the competition and pressure on Europe, urging the goal to ensure European autonomy in accessing and using space in a safe and secure environment. Europe does not only need innovations, but primarily a new generation of engineers, capable of understanding the full complexity of launcher development and trained to create and realise the necessary innovations. In this context, ASCenSIon is a multidisciplinary training programme involving 15 Early Stage Researchers (ESRs) from anywhere in the world, focused on several specific areas of cutting-edge space access research, particularly on launcher systems that are (partially) reusable and capable of injecting multiple payloads into multiple orbits. The network aims to identify and advance critical technologies to prove a feasibility of these concepts, and to advance the State of the Art in the field. ASCenSIon, whose acronym stands for “Advancing Space Access Capabilities –Reusability and Multiple Satellite Injection”, is a consortium of 11 beneficiaries and 17 partners across Europe, eager to contribute to the establishment of an ecologically and economically sustainable space access for Europe, oriented towards user needs. Unlike other single-aspect research projects, the core objective of ASCenSIon is not only to train 15 PhD students to become excellent specialists in their respective field, but also to provide them a thorough understanding of the complexity, multidisciplinary, and internationality of launcher development, in order to become leaders in the European effort of utilising space. This will be achieved through secondments, events, and lessons from experts, but mostly through strong interconnections among the ESRs, who will work on Individual Research Projects with a multi-disciplinal and multi-sectoral approach. This paper aims to provide an overview of ASCenSIon programme. Its values and core objectives will be introduced, together with the innovative aspects and content structure. An overview of the research methodology and recruitment strategy will be given, with a particular focus on the contributions and synergies of all participating organisations, core of such a novel training approach.