GALCIT Colloquium

About 100 tonnes of small meteoroids enter the terrestrial atmosphere every day. From one meter diameter to micron-size grains, these objects largely disintegrate during their entry, contributing significantly to the input of cosmic material to Earth. Yet, their atmospheric entry is not well understood. Experimental studies on meteoroid material degradation in high-enthalpy facilities are scarce and, when the material is recovered after testing, it rarely provides sufficient quantitative data for the validation of simulation tools. First, we investigate the thermo-chemical degradation mechanism of a meteorite in a high-enthalpy ground facility able to reproduce stagnation point conditions representative of atmospheric entries. The methodology involves measurement techniques and computational models previously developed for the characterization of thermal protection materials used as spacecraft heat shield. Here, alkali basalt (employed as meteorite analogue) and ordinary chondrite samples are exposed to a cold-wall stagnation point heat flux of 1.2 MW/m2. The simulation results highlight the importance of iron oxidation to the material degradation. Second, we develop a Lagrangian reactor assuming that detailed chemistry processes can be decoupled from steady flows, governed by the Maxwell transfer equations accounting for a coarse-grain mechanism. The code developed is applied to simulations of meteors at high altitude using the Direct Simulation Monte Carlo method. The Lagrangian reactor allows us to introduce additional processes such as recombination reactions, not considered in the base line simulation, providing a map of free electrons in the trail up to a distance of 2 km from the meteoroid. These simulations tools will be used to interpret radio observation of meteors.