| Description |
xi, 94 leaves : illustrations ; 29 cm |
| Summary |
"The effect of ablation heat shields on the radiative heat transfer to vehicles entering hydrogen atmospheres at thermo-dynamic conditions similar to those expected in Jovian atmospheres is investigated. The shock layer is assumed to consist of two plane parallel layers, one consisting of pure hydrogen species, and the other consisting of carbon species only. Each layer is assumed to be in local thermodynamic equilibrium at its respective temperature. The thermodynamic conditions in the hydrogen layer are arrived at by solving the Rankine-Hugoniot Equations across the shock. The temperature of carbon layer is taken as (3000, 5000, and 7000°K) to cover the range of possible surface temperatures. Two entry velocities (115,000 and 190,000 fps) and four ambient densities (10⁻⁶ through 10⁻⁹ gm/cm³) are considered. Four ratios of carbon layer thickness to total shock layer thickness (0.0, 0.05, 0.10, and 0.15) are considered, and the total shock layer thickness is allowed to vary from 0.1 to 10 cm. Both line (including carbon bands) and continuum processes are considered. The results show that: 1) The carbon layer reduces the flux reaching the surface from hydrogen layer in most cases, but not always. The reduction increases as the density and velocity increase. The ablation layer increases the flux when the hydrogen layer is optically thin and the ablation layer is optically thick. 2) Atomic carbon is the most effective absorber in the carbon layer. Molecular carbon bands also become important as the ambient density and temperature decrease. 3) The atomic and ionic carbon lines are unimportant in reducing or increasing the flux from the hydrogen layer. This is because the half-widths of these lines are small and the population of ionic carbon is not large at the temperature considered in the study. An error was detected in the computer program for the calculation of the position of the hydrogen edges. Two cases with correct positions of the hydrogen edges were run on the computer and the corrected results are shown in Appendix E. The numerical value of continuum flux changed considerably, but the trends of the results appear to be similiar to those discussed in the body of the thesis. Further results were not computed due to the expense of the computer runs"--Abstract, leaves ii-iii. |
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