| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2005: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 2003: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
In 1995, the Galileo probe vehicle launched by NASA entered into the Jovian atmosphere at a velocity of 49 km/s. The probe vehicle was thermally protected by ablative heatshield. According to the actual flight data, the amount of heatshield recession at the stagnation point was found to be halved and that at the frustum region was doubled than those given by the preflight prediction.
In this study, the strongly radiating flowfield over the Galileo probe vehicle is numerically obtained using the newly developed computer code, in which we assume the thermochemical equilibrium flowfield and also the steady ablation of the heatshield. For the first time, we have successfully reproduced the amount of heatshield recession at the frustum region. We have also identified the cause of enhanced radiative heating occurred at the frustum region. It is however indicated that the amount of heatshield recession at the stagnation region is still overestimated. This is probably caused by nonequilibrium effect in the shock layer that is not accounted for in this study. Although the nonequilibrium effect itself reduces the amount of radiative heating at the stagnation region, a more accurate prediction method is certainly needed to reduce the weight of heatshield and maximize payload in the design of future probe vehicles.
As a preliminary step, we have optimized the multiband radiation model for the mixture of hydrogen and helium. At higher temperatures, the radiative property of atomic hydrogen is critically influenced by the number density of electron. Therefore, the newly developed multiband model accounts not only for the translational temperature of the gas but also for the number density of electron, simultaneously. The accuracy of the model is critically assessed. The developed radiation model will be employed in the computer simulation of nonequilibrium ionization of hydrogen observed in various shock tube experiments.
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