The radiation and conduction coupled heat transfer processes in optical windows under aerodynamic
heating are studied in order to understand the thermal emission characteristics and the thermal protection properties. A
computational model for the coupled heat transfer in optical windows with Fresnel interfaces is established by FVM,
MCM and spectral band model. The heat transfer characteristics for a specific optical window with two SiO2 glass lay鄄
ers are numerically simulated. Results show that the glass layer under aerodynamic heating has net radiation emission
and the other layer has net radiation absorption. Radiative flux in the optical window is greater than conductive flux
except in the vicinity of the heated surface. The radiative flux in the wavelength between 2. 9 滋m and 4. 2 滋m is grea鄄
ter than in the wavelength between 0. 4 滋m and 2. 9 滋m where the radiative flux going into spacecraft interior through
the optical window has the lowest value in the visible spectrum and the highest value in the mid infrared spectrum. In
the case of the optical window total thickness unvaried, decrease in both the gas conductivity and the gas layer thick鄄
ness can effectively lower the steady state temperature of the optical window's unheated surface.