In the current global space race, dominated by both private companies (SpaceX, Blue Origin) and national programs (China, Russia, India), Europe must strengthen its propulsion strategy to maintain independent access to space. Reducing launch costs and enabling reusability are key priorities, making low-cost cryogenic engines essential. Among liquid propellants, methane stands out as the most promising candidate for future European launchers due to its handling advantages, higher density, easier storage compared to hydrogen, and its suitability for reusable engines such as Prometheus.

However, methane combustion in cryogenic rocket engines presents challenges, particularly the formation of soot, which can affect several components: clogging the gas generator (GG), altering combustion chamber (CC) performance through increased radiative heat transfer, and obstructing regenerative circuits (RC) via coking, thus limiting reusability.

To address these issues, CNES and ONERA are conducting joint research through both experimental tests on the ONERA MASCOTTE cryogenic test bench and advanced numerical simulations. Experimental campaigns with LOx/methane have confirmed soot formation and generated validation databases. Very recent campaigns (2023–2024) focused on low mixture ratios, employing advanced diagnostic tools such as Laser-Induced Incandescence (LII), Laser-Induced Fluorescence (LIF), soot morphology studies, and gas composition analyses.

On the computational side, ONERA uses its multiphysics simulation code CEDRE for RANS studies and aims to advance toward high-fidelity Large Eddy Simulation (LES). The doctoral research project is focused on developing LES models for bi-transcritical LOx/CH4 injection conditions at high pressure and fuel-rich regimes, representative of gas generator operation. Key challenges include accurately modeling the transition of cryogenic propellants to supercritical states and predicting soot formation.

The PhD will build on existing international and ONERA work on soot modeling, adapting it to rocket combustion systems, where soot studies are still at an early stage. After validating models on high-pressure elementary flames, the student will simulate MASCOTTE test cases. This involves defining suitable chemical kinetics, reducing detailed mechanisms, and potentially applying AI-based reduction methods.

Ultimately, these simulations will provide innovative insights into soot formation in rocket engines, support the development of specifications ensuring proper turbopump operation with methane, and contribute both scientifically and industrially. The thesis offers strong opportunities for publications, conference participation, and collaboration with the aerospace community, paving the way for the candidate’s future career.

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For more Information about the topics and the co-financial partner (found by the lab!); contact Directeur de thèse - nicolas.bertier@onera.fr

Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online  before March 13th, 2026 Midnight Paris time!