Aeroheating measurements on a reentry capsule model in free-piston shock tunnel HIEST

Aeroheating of an Apollo CM model was measured in the free-piston shock tunnel HIEST. The primary purpose of the measurement was to obtain benchmark data for numerical codes validation under high-enthalpy high-Reynolds number conditions. The model was made of SUS-304 stainless steel and had a diameter of 250mm. The windward surface of the model was equipped with 84 miniature co-axial Chromel-Constantan thermocouples that were manufactured in-house at JAXA. Twelve thermocouples and two Piezo-resistive pressure transducers were also mounted aft on the model and were used to determine the establishment of flow around the model. In this test campaign, heat flux data were measured for angles of attack 0o and 30o. Stagnation enthalpy and stagnation pressure were varied from H0=4MJ/kg to 21MJ/kg, and from P0=14MPa to 58MPa, respectively. Aeroheating characteristics were observed with a fully laminar boundary layer and with a transition boundary layer. Measured heat flux was normalized by the product of the Stanton number and the square-root of the Reynolds number for correlation with other wind tunnel results and flight results. The normalized heat flux value did not change remarkably when stagnation enthalpy was changed from H0=4MJ/kg to 12MJ/kg, implying that the boundary layer flow was usually laminar. However, shots under high enthalpy and high Reynolds number conditions (H0 over 18MJ/kg and P0 approximately 50MPa) showed that the measured heat flux was approximately 40% higher than that obtained in other conditions.