Apollo-Shaped Capsule Boundary Layer Transition at High-Enthalpy in T5

Abstract

An investigation of the boundary layer transition on a 7-inch Apollo-shaped capsule heatshield at high enthalpy was performed in the T5 Hypervelocity Shock Tunnel at GAL-CIT. Three series of tests on 2 models for a total 57 shots were performed in air at angles-of-attack of 20-deg and 28-deg for stagnation enthalpies between 7 and 20 MJ/kg and stagnation pressures between 20 and 60 MPa. The free-stream Reynolds number based on model diameter was between 0.3 and 0.9 million. A trip insert with 25 0.05-inch square "pizza box" roughness elements located at 0.345-inch below the heat shield geometric cen- ter was used to promote transition on the leeside of the model. Trip heights of 0.007, 0.010 and 0.015 inch were used. Tests were performed with and without trips to evaluate the turbulent heating augmentation. For the highest Reynolds number condition, natural transition occurred on the leeside at both angle of attacks. The most aggressive trips appear to have generated a fully turbulent ows over the leeside of for the high enthalpy conditions at 17 MJ/kg.