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The coking phenomenon within low- density ablative material exposed to aerodynamic heating is studied. The char density of the tested material is measured by slicing the material thinly, and by weighing each of the sliced test pieces. Measured density profiles of the tested materials are compared with the calculated results obtained by a thermal response code. The surface and internal state of both pre- and post- materials are observed by using Scanning Electron Microscope (SEM) and X-ray Computed Tomography (CT). The results show that the measured density profiles is inversely increased to the heated surface. The density increase is likely due to the deposition of a solid carbon in the char region during aerodynamic heating., 資料番号: AA0063742010, レポート番号: JAXA-SP-07-016

A trajectory-based heating analysis of the Galileo probe entry flowfield is attempted to reproduce the heatshield recession data obtained during the entry flight. In the present calculation, the mass conservation equations for the freestream gas (hydrogen-helium gas mixture) and the ablation product gas are solved with an assumption of thermochemical equilibrium. The ablation process is assumed to be quasi-steady and is coupled with the flowfield calculation. The radiative energy transfer calculation is tightly coupled with the flowfield calculation, where the absorption coefficients of the gas mixture are given by the multiband radiation model having 4,781 wavelength points for wavelength range from 750 to 15,000 A. The injection-induced turbulence model proposed by Park is employed to account for the enhanced turbulence effect due to the ablation product gas. It is shown that the final recession profile of the flight data at the frustum region can be closely reproduced if the injection-induced turbulence model is employed, although that at the stagnation region is overestimated. The cause of the enhanced radiative heating that occurs at the frustum region is given in connection with the enhanced turbulence effect in the shock layer., 資料番号: AA0048469010, レポート番号: JAXA-SP-04-012