Study of the Effects of Heat Load, Ablator Density and Backup Structure upon the Thermal Protection Performance of Heat Shield Systems Consisting of Phenolic Carbon Ablators

The effects of heat load, ablator density, and backup structure, etc. upon the heat shield performance of the lightweight phenolic carbon ablators named LATS were investigated using a one-dimensional ablation analysis code. The ablator density was assumed to be from about 260 to 1000 kg/m3. Heat flux time histories of a rectangular pattern were assumed, where cases of constant heating duration time and constant accumulated heat load (up to 600 MJ/m2) were considered. The heating level was assumed to be from 1 to 10 MW/m2, which means that the ablator surface is in the region of diffusion control oxidation/sublimation. The materials of the backup wall are assumed to be aluminum, stainless steel and high density CFRP. Main findings are: (1) For a low heat flux q with the same heating duration time tq, the necessary thickness, with which the maximum back surface temperature equals to the pre-determined allowable temperature, is nearly constant as the density ρv changes. On the other hand, the necessary thickness increases largely when q is larger and ρv is smaller. The ablator necessary mass increases with the increase of ρv and q for the same tq. (2) When a backup wall is attached, the necessary thickness decreases and the necessary mass including the wall mass increases. (3) For a constant accumulated heat load, necessary thickness and mass decrease for a higher heat flux q especially when ρv is high. (4) A lower density ablator with a CFRP backup wall gives the lightest mass of the heat shield system for most of the parameter range among the three wall materials. (5) For a high heat flux, selection of a lower density ablator gives a larger necessary thickness.30th International Symposium on Space Technology and Science (ISTS), July 4th-July 10th, 2015, Kobe-Hyogo, Japa