On Board Optical Emission Spectra Collection in Plasmatron X Facility for Hycube Missions

Time-resolved optical emission spectroscopy measurements were performed at the Plasmatron X facility under 110-455 W/cm$^2$ heat flux conditions through a sapphire window embedded in TPS material planned for use on a hypersonic flight vehicle known as HyCUBE. These measurements were conducted in synthetic air at 70 mbar and coupled with two-color pyrometer surface temperature measurements, as well as thermocouple-based internal temperature measurements. For samples fabricated of AETB with RCG-coating, our results demonstrate (1) negligible contamination of the observation window by potential ablation products; (2) survivability of the test articles for the anticipated HyCUBE descent trajectories, (3) capability of simultaneous inference of the rotational and vibrational temperatures at the millisecond timescale using a miniature low-resolution spectrometer. Gas (translational) temperatures and vibrational temperatures in the ranges of 8,000 - 11,000 K and 7,400 - 9,000 K were obtained, respectively. In general, we present the benefits of the HyCUBE concept for in-situ spectroscopic diagnostics in hypersonic flight vehicles.