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International audience; A cooperation on the aerodynamic optimization of helicopter rotors has been formed by JAXA, ONERA and DLR. This work represents the conclusions drawn from the first phase: optimization of a hovering rotor. The HART-II blade is first investigated with low-fidelity tools and compared against state-of-the art CFD simulations. Following up on this, the HART-II blade chord distribution and twist are optimized with the low-fidelity tools as well as CFD. Due to observed differences in the outcome of the CFD simulations for the low-fidelity optimized blades by the partners, a deeper investigation of the effects of the turbulence modelling approach, elasticity and grid topology is undertaken. The outcome is that the chosen flight condition is close to thrust of the maximum Figure of Merit and the vortex triggered separation on the outboard sections of the blade has to be modelled correctly. In this study, the blade grids had the most noticeable effect on the results, followed by the turbulence model and elasticity. With respect to the optimization, care must be taken when optimizing with lowfidelity methods, whereas CFD optimized blades were found to lead to more robust designs even though they have only been optimized for a single point. Reason is the more accurate modelling of the stall phenomenon with respect to geometrical changes.; Une coopération sur l'optimisation aérodynamique des rotors d'hélicoptères a été formée entre le JAXA, l'ONERA et le DLR. Ce travail présente les conclusions obtenues lors de la première phase: l'optimisation d'un rotor en vol stationnaire. La pale HART-II est d'abord étudiée avec des outils basse fidélité, et comparée aux simulations CFD les plus récentes. Suite à cela, les distributions de corde et de vrillage de la pale HART-II sont optimisées avec des outils numériques basse fidélité ainsi que par CFD. En raison des différences observées dans les résultats de simulations CFD pour les pales optimisées à basse fidélité par les partenaires, une étude plus approfondie des effets de la modélisation de la turbulence, de l'élasticité de la pale, et de la topologie des maillages est entreprise. Le résultat est que la condition de vol choisie est proche de la poussée de la figure de mérite maximale et que la séparation déclenchée par les tourbillons sur les sections extérieures de la pale doit être modélisée correctement.Dans cette étude, les maillages des pales ont eu l'effet le plus notable sur les résultats, suivis par le modèle de turbulence et l'élasticité. En ce qui concerne l'optimisation, il faut être prudent lors de l'optimisation avec des méthodes de basse fidélité, alors que les pales optimisées par CFD se sont avérées conduire à des conceptions plus robustes, même si elles n'ont été optimisées que pour un seul point. La raison en est la modélisation plus précise du phénomène de décrochage par rapport aux modifications géométriques.

The Mass Spectrum Analyzer (MSA) will perform in-situ observations of ions and magnetic fields around Phobos as part of the Martian Moons eXploration (MMX) mission to investigate the origin of the Martian moons and physical processes in the Martian environment. MSA consists of an ion energy mass spectrometer and two magnetometers which will measure velocity distribution functions and mass/charge distributions of low-energy ions and magnetic field vectors, respectively. For the MMX scientific objectives, MSA will observe solar wind ions, those scattered at the Phobos surface, water-related ions generated in the predicted Martian gas torus, secondary ions sputtered from Phobos, and escaping ions from the Martian atmosphere, while monitoring the surrounding magnetic field. MSA will be developed from previous instruments for space plasma missions such as Kaguya, Arase, and BepiColombo/Mio to contribute to the MMX scientific objectives.

International audience

International audience; Lunar seismology has always suffered from the limited number of seismic stations and limited coverage of the seismic network. Additional seismic data are necessary to probe the lunar interior in depth. Instead of a costly new deployment of seismometers, the aim of this study is to investigate the possibility of using the Apollo 17 Lunar Surface Gravimeter (LSG) as a lunar seismometer. The LSG was designed to detect gravitational waves (associated to change in the curvature of spacetime) and tidal ground motion on the Moon, but the data were not investigated for seismic use partially because of a malfunction of the instrument. We first evaluated the influence of the malfunction through comparison with other Apollo seismic data and found that the effect of the malfunction is small, and the LSG detected seismic signals in a manner that was consistent with those of the other Apollo seismometers. Then we carried out source location with the additional station of the LSG. We relocated previously located deep moonquake nests to evaluate the influence of the LSG data, which are generally noisier than other Apollo seismic data. Then we located deep moonquake nests that were previously unlocatable. Forty deep moonquake nests were examined, and we located five new nests. One newly located nest, A284, was most likely to be located on the farside. This series of analyses indicates that the LSG functioned as a lunar seismometer, and that its data are useful for improving seismic analyses with the previous seismic data set of the Moon.

International audience; We have developed an inertia-driven micro actua-tor for the harsh environment of space. Different from the conventional PZT-driven or other actuators, the newly developed electrostatic mechanism is free from material property change due to temperature. A mass suspended in the actuation system is designed to collide with the internal wall to produce thrust by an impact-type inchworm mechanism.