Gamma and infrared novel methodologies in Aerospace re-entry: γ-rays crystal efficiency by GEANT4 for TPS material recession assessment and simultaneous dual color infrared temperature determination

Abstract

The re-entry of a vehicle into Earth's atmosphere either from near-Earth orbit or from interplanetary trajectories is the most critical phases of a space mission for materials, since space capsules and spacecraft surfaces are brought to relatively high temperatures (>2000 °C) and are subject to the high thermal fluxes. The most complex requirements of the on-ground CIRA hypersonic Plasma Wind Tunnel (PWT) test campaigns are to measure and monitor the high heat fluxes, the correlated surface Recession Rate and Surface Temperatures affecting the behavior of Thermal Protection System (TPS) materials which makes up the surface and sub-surface components of the spacecraft's outer layer.For these tests, the recession rate will be obtained by Surface Layer Implantation (SLI), monitored by the gamma ray emission from 7Be implanted into the test material, and the surface temperature by Dual Color free emissivity Infrared Thermography (DCIT). So the first purpose of the paper, in the recession rate determination, is to present the γ-ray detection efficiency of a LaBr3(Ce) crystal by GEANT4 simulation using the radioactive ions, to be implanted by means of the CIRCE accelerator, and the use of γ-rays to monitor their removal during the ablation process. At the same time, for temperature determination, is to evaluate the possibility of carrying out free emissivity temperature measurements in unsteady conditions.On the basis of the results, possible validation tests are outlined, through the use of the intense radioactive 7Be beam available at the 3MV Pelletron tandem accelerator of the CIRCE Laboratory and the GHIBLI-PWT facility at CIRA, to present the combined novel, contactless and non-intrusive diagnostics for the simultaneous recession rate and temperature determinations.