Stagnation-point radiation for Apollo 4

Abstract

The radiative heating rate at the stagnation point of the Apollo 4 vehicle is calculated using an up-to-date set of radiation parameters and is compared with the flight data. The radiation parameter set includes the recently characterized atomic lines of N and O and the molecular bands of N-2, CO, and H-2 in the vacuum ultraviolet wavelength range not accounted for in previous studies. The study finds that the inclusion of the new atomic lines leads to a substantial increase in the radiation intensity at the boundary-layer edge, but that the absorption in the boundary layer by the new molelcular bands offsets the increase. A good agreement is found between the calculated and the flight-measured radiation intensities. The calculated radiative heat flux values agree approximately with the values used in numerically reconstructing the response of the ablative heatshield material.