An aero-thermo-chemical model is developed to simulate the flowfield, including ionization, around atmospheric re-entry configurations, and its interactions with radio-frequency communication signals (e.g. GPS). The model is successfully validated against literature in-flight measurements of the electron number density, and then applied to the re-entry of recently proposed concepts of slender configurations. The advantages of using sharp and slender geometries for re-entry applications, with respect to radio communication problems, are analyzed and discussed. In addition, an experimental test-bed in an arc-jet plasma wind-tunnel has been setup to reproduce on ground the plasmaradiofrequency interaction. The capability to duplicate on-ground the ionization levels encountered during re-entry has been successfully demonstrated. A numerical model of an Argon plasma jet in chemical and thermal non-equilibrium has also been developed, for numerical rebuilding of the experiments. Both electron number densities and electron temperatures have been successfully correlated, demonstrating the ability of arc-jet facilities, integrated with proper numerical tools, to correctly deal with problems of communication attenuation/black-out.

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The effects of flow on the acoustic behavior of metamaterials can be very significant and possibly destructive. To avoid these detrimental effects, it would be a good idea to have a “magic layer” that allows acoustics to pass through while suppressing the sound-flow interactions. A possible realization of this layer based on Kevlar fabric is tested in this paper. It is shown that, in the presence of Kevlar, flow-sound interactions that can lead to acoustic amplification and whistling phenomena are avoided. Thus, Kevlar will permit liner designs including large slits. However, it adds large acoustic losses, which limits interesting resonance effects in applications.

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