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Études expérimentales et numériques de la transition laminaire-turbulente en régime hypersonique sur la géométrie BOLT
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EFESTO 1 & 2: european achievements and expected advancements in inflatable heat shields for mars and earth re-entry applications
No full textInternational audienceAbstract: The utilization of Inflatable Heat Shields (IHS) has emerged as a transformative solution for re-entry applications on both Earth and Mars. IHS holds great potential for facilitating the safe re-entry of various space systems elements, such as launcher stages, ISS cargo payloads, and reusable satellites, in Earth scenarios. Additionally, IHS’s inherent scalability aligns well with the anticipated surge in missions for large-scale robotic and human exploration on Mars in the coming decades, enabling precision landing andhigh-mass delivery. Within the European Union, the EFESTO and EFESTO-2 projects have played a pivotal role in advancing the fieldof Inflatable Heat Shields. The EFESTO project, conducted from 2019 to 2022, focused on ground-based technology development and successfully facilitated the growth of know- how in Europe pertaining to IHS. The consortium achieved an increase in the Technology Readiness Level (TRL) of key IHS technologies from 3 to 4 through the implementation of a comprehensive range of activities. These included mission and system-level conceptual design, the design, manufacturing, and testing of Flexible Thermal Protection Systems (F-TPS), as well as the design, realization, and testing of a subscale Inflatable Structure (IS) demonstrator. Building upon the achievements of EFESTO, the recently initiated EFESTO-2 project, which started in November 2022, aims to ensure continued development in line with the progress made by EFESTO. EFESTO-2 expands the scope of investigation through refined modelling, analysis, and extended ground testing. Key additions in EFESTO-2 include the realization and testing of very small-scale models replicating the deformed shape in wind tunnels, an extension of static and dynamic structural tests for the sub-scale Inflatable Structure demonstrator developed in EFESTO, numerical- based coupling between F-TPS and IS subsystems using Fluid-Structure Interaction analysis techniques, and the development of a GN&C system up to TRL 4-5 for IHS-based re-entry systems to enable precision landing with guided and controlled flight capabilities. This paper provides an overview of the significant achievements attained during the EFESTO project and the on- going progress in the EFESTO-2 project. The EFESTO and EFESTO-2 projects have received funding from the European Union under the Horizon 2020 and Horizon Europe research and innovation programs, respectively (grant agreement No.821801 and 101081104)
Problèmes de configuration de flottes hétérogènes pour la planification de tâches
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Separation and Transition on a CCF: Experimental Campaigns
No full textSeveral experimental campaigns have been conducted across a number of Mach-6 facilities on the hypersonic flow around a cone-cylinder-flare (CCF) geometry with a 5° half-angle cone and a 12° half-angle flare. These experiments were conducted as part of the NATO STO Research Task Group AVT-346, which is focused on pre-dicting hypersonic boundary-layer transition on complex geometries. Two conventional wind tunnels (AFRL M6LT and ONERA R2Ch) and one quiet tunnel (Purdue BAM6QT) were used to test the same CCF geometry and to study the instabilities in both the boundary layer in the attached parts of the flow and the shear layer above the axisymmetric separation bubble near the cylinder-flare junction. Two nosetip radii (one nominally sharp and one blunt with a 5 mm radius) were tested. For the sharp nosetip case, there was a great deal of agreement between the measurements of both second-mode and shear-layer instabilities across the two conven-tional facilities. However, the measured spectra for the blunt nosetip case showed more significant differences between the two tunnels, potentially due to an alternate dominant instability mechanism coupled with the varia-tions in the freestream noise spectra. The quiet facility resulted in a flow that remained laminar to much higher freestream unit Reynolds numbers, as well as in instability measurements that had more distinct spectral peaks for the sharp tip case and broadband rises for the blunt one. The instability mechanisms at play in the sharp quiet case were found to be the same as those in the conventional facilities
A 150-Year Record of Past Radiation Belt Electron Enhancement Events: Development and Application to Space Weather Forecasting
No full textInternational audienceAs part of the Horizon Europe FARBES (Forecast of Actionable Radiation Belt Scenarios) project, we have developed a method to automatically identify past radiation belt electron enhancement events using a ground-based geomagnetic index [Bernoux et al., 2025, accepted for publication in AGU ESS]. This method has enabled the production and publication of a list of over 150 years of past radiation belt electron enhancement events. By cross-referencing with catalogues of interplanetary events (SIRs, ICMEs), we have been able to assign a possible interplanetary cause to each post-1995 radiation belt event. In this presentation, we will first present the methodology used to derive the list of events and discuss how it can become a valuable asset to the community for both space weather and space climate studies. In particular, we will demonstrate its application to the analysis of extreme events and also highlight its potential for forecasting purposes, using a simple but effective analogue ensemble-based methodology that allows us to provide forecasts of the Kp index as physically credible scenarios. By using this historical context, we can provide more robust forecasting capabilities, ultimately improving the resilience of critical infrastructure to space weather impacts
Projet FED SILENT : vers une soufflerie hypersonique silencieuse européenne
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La prédiction temporelle action-effet n'affecte pas la perception de l'intensité sonore, mais influence le sentiment d'agentivité.
No full textInternational audienceMotor theories propose that predicting sensory consequences of one's own actions reduces perception and neural processing of these action-effects, a phenomenon known as sensory attenuation, considered an implicit measure of agency. However, recent findings question the link between action-effect prediction and sensory attenuation. This study directly examined the link between temporal action-effect prediction and auditory sensory attenuation, alongside assessing self-reported agency. Participants experienced self-initiated auditory effects with varying latencies and compared their loudness to a reference tone, whose intensities were modulated to measure auditory discrimination. Results showed no change in perceived loudness across delays, while agency ratings decreased with longer delays. A second experiment controlled for hazard rate effects, confirming initial findings. Our results contrast previous behavioral findings from the tactile modality and conclusions drawn from auditory electroencephalography. We suggest reconsidering auditory sensory attenuation as a necessary consequence of action-effect prediction and as an implicit measure of agency
Contribution à l'aérodynamique et l'aéroacoustique appliquée aux hélicoptères, open-rotors et hélices
No full textStabilité thermochimique de phases céramiques réfractaires cubiques à base d’hafnie en présence de tungstène
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Retinal axial motion analysis and implications for real-time correction in human retinal imaging
No full textHigh-resolution ophthalmic imaging devices including spectral-domain and full-field optical coherence tomography (SDOCT and FFOCT) are adversely affected by the presence of continuous involuntary retinal axial motion. Here, we thoroughly quantify and characterize retinal axial motion with both high temporal resolution (200,000 A-scans/s) and high axial resolution (4.5 µm), recorded over a typical data acquisition duration of 3 s with an SDOCT device over 14 subjects. We demonstrate that although breath-holding can help decrease large-and-slow drifts, it increases small-and-fast fluctuations, which is not ideal when motion compensation is desired. Finally, by simulating the action of an axial motion stabilization control loop, we show that a loop rate of 1.2 kHz is ideal to achieve 100% robust clinical in-vivo retinal imaging