Increased Re-Entry Vehicle Thermal Protection Requirements Due to Surface Roughness

A survey is presented of recent experimental data, correlations, and prediction methods for the effects of surface roughness on re-entry vehicle aerodynamic heating, as related to thermal-protection requirements. Regions of concern are the nosetip and frustum; in each case, the primary source of surface roughness is the ablative response of non-homogenous heat-protection materials. Numerical examples are given to illustrate the quantitative effects of surface roughness on thermal-protection requirements for typical re-entry vehicles. Several correlations are used to demonstrate the wide variation in predictions that can result. The paper closes with an assessment of critical technology needs in this field.