Aerodynamics of hypersonic waverider in rarefied regime – APHYRA

This project is part of a current defence context. Indeed, it aims to contribute to the design of hypersonic planes, considered in the long term, to ensure different missions. The trajectory of this type of vehicle travels through different phases in the presence of different flow regimes and whose mission’s success will depend on the control of the vehicle trajectory. Part of the trajectory which takes place at very high altitude corresponds to the rarefied regime for which the real gas effects, and rarefaction effects can degrade the performance of the vehicle if they are not taken correctly into account in the design of the glider. A great number of numerical works are published and presents the study of the performance of hypersonic gliders for the entire trajectory. Nevertheless, in the rarefied regime, for altitudes between 100 and 60 km altitude, the physical models used are merely approximations which some authors have demonstrated to be inefficient, in terms of performance. To our knowledge, there is no experimental study of the influence of these effects on the aerodynamic performance of hypersonic gliders. This proposal deals with the experimental study of the effects of rarefaction occurring during the high-altitude flight of a hypersonic glider-type vehicle. The main objective is to determine experimentally if the effects of rarefactions significantly or not modify the aerodynamics of hypersonic gliders when they are flying at high altitude, in a rarefied atmosphere. This study will be carried out with the rarefied hypersonic wind tunnel MARHy from the FAST experimental platform belonging in the ICARE laboratory. This facility can experimentally cover the Reynolds / Mach flight conditions of glider trajectories for altitudes between 100 and 60 km. This project aims to determine experimentally for models of hypersonic gliders and delta wings: 1- aerodynamic coefficients (CL, CD); 2- wall conditions (pressure, temperature, flow) 3- characterization of the flow around models (density, pressure).

These measurements will be performed for several flow conditions in terms of Mach numbers (4, 6.8, 18, 20) and working pressure (altitude, Reynolds).
These different measurement campaigns will cover a wide range of flow conditions, presenting a double interest:
• the aerodynamic study of hypersonic gliders in a wide variety of situations, thus allowing a better understanding of the physics of rarefied flows with a large Mach numbers around complex geometries. The influence of rarefaction effects, unfavourable according to numerical simulations, can thus be demonstrated and quantified experimentally;
• the building of empirical correlations to improve the prediction of lift and drag coefficients of hypersonic gliders, and delta wings, as a result of this project.

The set of experimental results will constitute an experimental database that will be used to build physical models in the transition regime in order to validate and / or improve the slip conditions used in laminar CFD simulations by comparing the results. The knowledge acquired can be transposable for civil applications such as the design of hypersonic vehicles for space exploration or the refined prediction of the location and date of the fallout of space debris. Finally, this project will not only help to maintain but also strengthen national skills and expertise in the field of rare-water hypersonic flows.