Nonintrusive instrument for thermal protection system to measure recession and swelling

Quantifying the thermal response of a heat shield is a key step in the design of a spacecraft to ensure its survivability during atmospheric entry. Recession and swelling of the thermal protection material have a drastic effect on both the heat transfer within the vehicle and aerothermodynamic transients. Postflight analysis of reentry can be achieved after recovery on Earth, but it is more difficult for entries on other bodies of the solar system. A dedicated instrumentation is necessary to understand the evolution of the thermal protection material thickness during flight. This paper investigates the current limitations of the available measurement techniques. A low-mass passive solution is proposed to measure with high accuracy the phenomena of recession and swelling. The QubeSat for Aerothermodynamic Research and Measurements on Ablation (QARMAN) CubeSat mission provides a flight opportunity to develop a dedicated payload to quantify the recession and swelling of an ablative heat shield made of P50 cork from AmorimTM. In addition, this payload allows us to study the radiation of a reentry plasma in the presence of ablation products through the same optical path. The performance of the measurement technique and the integration of the instrument are discussed for the QARMAN platform, demonstrating its applicability to a space mission