Subject:Density and temperature effects on plasma-fluid couplings for EHD high atmosphere propulsion

Context 

Electric propulsion in vaccum is now the mainstream propulsion for satellites. At high atmosphere, (between 15 to 30km) Electro-Hydro-Dynamic propulsion using ionic wind is relevant, but yet poorly developed. Along the last years, various developments [Masuyama & Barrett 2013] have emphasized the interest of this propulsion without moving solid part, silent, and electric, which can be used by drones or stratospheric balloons, as a co-propulsive  secondary system for trajectory control [Monrolin et al., 2017, Xu et al. 2018, Plouraboué, 2018]. One distinct advantage of this propulsion is that it is easy to control electrically, it display a very short time response, and does not need moving solid  parts (as opposed to blades in turbo-fans). On the one hand, it necessitates an emiter source, producing charges which is typically an thin cylindrical wire connected to a DC high-tension generator and, on the other hand, a collecting electrode. Various kind of sources have been

Various studies in the literature have shown that a simple high-voltage wire producing a corona discharge is the most efficient source [Moreau et al., 2006, 2013, 2022] (compared to other plasma sources such as DBDs [Forte et al., 2007]) for producing ionic wind, even if the propulsive force remains very modest compared to conventional propulsion devices.

However, previous studies [Chapman 1970, Pereira et al. 2014, Bondar & Bastien 2000], as well as recent [Grosse et al. 2024, Trovato et al. 2025, Dias et al. 2025] and ongoing studies have also shown that, when the external flow is significant, the effects of plasma-fluid coupling become substantial. The maturity of modeling in this field has also progressed considerably in recent years [Monrolin et al., 2018ab, Monrolin & Plouraboué, 2021, Coseru et al., 2021, Picella et al. 2024, Dias et al. 2025], making it possible to consider reliable quantitative predictions of the distribution of ionic forces and wind in complex electrode systems. Ongoing work at IMFT shows that, closer to the charges ejection velocity (between 100 and 200 m/s), the energy efficiency of ion wind propulsion can become larger to that of thermal propulsion. These recent research results were obtained by the project team within the framework of previous national (ANR-ASTRID, CNES-DGA) and international (EIC Pathfinder IPROP) projects.

Scientific challenges

 Under these conditions, recent developments concerning plasma/fluid interactions have demonstrated that two-way coupling is possible between plasma and fluid, unlike what occurs at low speeds, where coupling is essentially unidirectional from plasma to fluid (one-way coupling) [Picella et al. 2024, Dias et al. 2025]. In this context, the influence of density effects on plasma generation has never been studied and is of major interest for increasing the strength of plasma/fluid coupling. Indeed, charge production is strongly (exponentially) dependent on density effects and can significantly change the nature and strength of the interactions. These effects are also obviously highly altitude-dependent, since air density depends exponentially with height. The aim of this study is to investigate the effects of density on ion wind generation (for example, through thermal density control). We will consider both the effects of density naturally experienced by the altitude in question, but also those induced by heating of the emitter.

How the proposal fits with COMETES aim?

This topic contributes to the objectives of the COMETES project by developing knowledge in the field of fluid-plasma coupling for electric propulsion in the upper atmosphere. These couplings are indeed poorly understood, but present interesting potential for close-range Earth observation. Furthermore, from a knowledge perspective, an original aspect of the proposed topic lies in developing, adapting, and applying the expertise and numerical methods mastered within the fluid mechanics community (adaptive meshes, radiative asymptotic approaches, finite elements, parallelization) to plasma problems. It also allows work towards sustainable propulsion (100% electric, with zero CO2 emissions) that could be used by high-altitude drones powered by photovoltaic panels, which is also the thematic focus of an ongoing European project, IPROP.

Among the COMETES themes, this project is relevant to the following areas: 1. Space Systems, 8. Systems Engineering, and 9. Space and Development. It follows on from past and ongoing work (ANR-ASTRID projects and the European IPROP project) in which the proposing laboratory is and has been involved. The project benefits from the expertise acquired in recent years at IMFT, which is one of the few teams in the world capable of calculating multiphysics fluid/plasma couplings with corona discharge, radiative effects, and strong fluid flows. The originality of the project also lies in its consideration of density effects, which have never been taken into account before.

Projected timeline?

First year: analysis of altitude effects with flow, Second year: consideration of thermal coupling effects with plasma in the absence of flow, third year: consideration of thermal coupling effects with plasma and forced flow.

Expected results ?

Designing innovative, clean propulsion systems that are more efficient than thermal engines at high altitudes for balloon or drone orientation control systems.

Bibliographie : 

H Bondar & F Bastien, J. of Physics D : Applied Physics, 19(9) :1657–1663, 2000.

S. Chapman, J.  Geophys. Research,  75, (12) :2165–2169, 1970. 

S. Coseru, et. al.,  J. Applied. Phys D.,  129, 103304, 2021.

J. M. Dias Coelho Marques,  et. al.,  J. of Physics D : Applied Physics,  58 435202, (2025).

M. Forte, et. al., Exp Fluids, 43, 6, 0723-4864, 2007.

S. Grosse et. al., J. Electrostatic, 130:103950, 2024.

K. N.,  Kiousis, et. al., Plasma Science and Technology,  16, No. 4, pp. 363–369, 2014.

K. Masuyama & S. R. H. Barrett, Proceedings of the Royal Society A,  50, No. 6, pp. 1480–1486, 2013.

N. Monrolin, et. al., AIAA, 55, 12, 4296-4305, 2017.

N. Monrolin, et. al., Phys. Plasmas, 25, 063503, 2018a.

N. Monrolin, et. al., Phys. Rev. Fluid., 3, 063701, 2018b. 

N. Monrolin & F. Plouraboué, J. Comp. Phys., 443, 110517,  2021.

E. Moreau, et. al., J. Electrostatic, 0304-3886, 64, 3-4, 2006.

E. Moreau , et. al.,  J. Electrostatic, 93, 85–96, 2018.69, 2022. 

E. Moreau, et. al.,  Journal of Physics D: Applied Physics, 46,  47, 2013.

R. Pereira, et. al.,  J. Phys. D. Appl. Phys., 116(10), 2014. 

F. Picella, et. al.,  AIAA J, 62:7, 2562-2573, 2024.

Plouraboué, F.,  Nature, 563,  (2018).

S. Trovato, et. al., J. of Physics D : Applied Physics, 58(1):015201, 2025.

Xu, H. et al. Nature, 563, 532–535 (2018).

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For more Information about the topics and the co-financial partner (found by the lab!); contact Directeur de thèse - franck.plouraboue@toulouse-inp.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!