Hypersonic Meteoroid Entry Physics

The capability to reproduce atmospheric re-entry phenomena in ground-based facilities is crucial to study the re-entry of space missions and of any objects de-orbiting or entering the Earth's atmosphere. During re-entry, these objects are exposed to intense mechanical and thermal stresses due to interactions with the high temperature plasma that forms in front of them. Complex physical and chemical phenomena occur at hypersonic conditions. The characterization of plasma–meteoroid interactions requires the ability to understand the thermochemical state of the plasma flow field, both in the free stream and in the boundary layer surrounding the meteoroid, as well as the determination of the evolution of the meteoroid under the effect of the plasma. The latter requires monitoring the temporal evolution of the shape and surface temperature of the material during melting and ablation processes and the ability to characterize the evolution of the structure and composition of the material. Several complementary ground-based facilities worldwide can be used for that purpose. A few of them are presented in this chapter. They include the SCIROCCO and GHIBLI facilities of CIRA in Italy, the HEAT facility at SITAEL (Italy), and the CP50 Plasma Torch facility at CentraleSup'elec (CNRS,France). These ground-based facilities operate under a wide variety of conditions, with test times ranging from less than 1 s (HEAT) to continuous (SCIROCCO, GHIBLI, CP50), specific enthalpies up to 30 MJ/kg, heat fluxes up to 30 MW/m2. The following sections present these various facilities and illustrate their measurement capabilities. Illustrative results from experiments on various materials, including meteorites, are presented.