Study of the Effects of Density, Thickness and Heat Load on Heat Shielding Performance of Phenolic Carbon Ablators Using a One-Dimensional Ablation Analysis Code

Abstract

The effects of density, thickness and heat load upon the heat shield performance of the lightweight phenolic carbon ablators named LATS (Lightweight Ablator series for Transfer vehicle Systems) were examined quantitatively for both arc-heated test and re-entry heating conditions using a one-dimensional ablation analysis code. Thermal conductivity values of the ablator were tuned based on the arc-heated test results by matching the calculated temperatures to the measured data. Main findings are: (1) For both heating conditions, the heat shielding performance of the ablator has the same tendencies with respect to parameters of the ablator density, thickness and heat load.(2) The dependency of the back surface temperature upon the ablator density is small especially for a large ablator thickness. (3) The surface recession decreases with the increase of the density. However, the mass loss increases almost linearly with the increase of the density. (4) The ablator necessary thickness, with which the maximum back surface temperature equals to the pre-determined allowable temperature value, is nearly constant as the density changes. The ablator necessary mass increases almost linearly, with the increase of the density. (5) In considering the mechanism of nearly equal necessary thickness of the ablator, it is very important that the thermal diffusivity does not vary much with different densities of the LATS ablator. (6) From the point of the reduction of the ablator weight, the selection of a lower density ablator is more advantageous than that of a higher density ablator.

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

“…Mathematical model of ablation, input data for the ablation analysis and the analysis conditions for the parametric study are shown in the following sections. 10,11) A one-dimensional computer code for charring ablation and thermal response analysis was used to calculate the heat resistant performance of the LATS ablators. The code was developed for simulation of one-dimensional transient thermal behavior of charring materials, and was successfully applied to the LATS ablators under the heating environments of arc-heated test.…”

“…[10][11][12][13][14][15][16] The in-depth governing equations for onedimensional charring ablator response are energy, mass continuity, and decomposition equations, and are expressed by…”

“…In the previous research 11) , q was assumed to be from 1 to 3MW/m 2 with tq of 60s. In such a low heating level, the surface temperature is well below 3000K and the surface ablation is mainly in the diffusion controlled oxidation region.…”

“…9,10) Ablation analysis with respect to the arc-heated tests was also carried out using a onedimensional analysis code and the measured and calculation results agreed well. 10,11) Investigations concerning the effects of heat load and ablator density upon the necessary thickness tne and necessary mass mne of the LATS ablator were carried out using a one-dimensional ablation analysis code. 11) It was found that the necessary thickness tne is nearly constant as the ablator density changes, and the necessary mass mne increases almost linearly with the increase of the density.…”

“…10,11) Investigations concerning the effects of heat load and ablator density upon the necessary thickness tne and necessary mass mne of the LATS ablator were carried out using a one-dimensional ablation analysis code. 11) It was found that the necessary thickness tne is nearly constant as the ablator density changes, and the necessary mass mne increases almost linearly with the increase of the density. In the study, the ablator back surface was assumed to be attached to an insulation material, and the heating level was from 1 to 3 MW/m 2 , which means that the surface ablation is mainly in the diffusion controlled oxidation region and not in the sublimation region (See 3.1.4.).…”