Titan Atmospheric Composition By Hypervelocity Shock-layer Analysis
Planning is currently underway to send a probe into the atmosphere of Titan (a moon of Saturn) as part of the Cassini Mission. This paper presents an investigation of the feasibility of determining the mole fractions of the major species in Titan's atmosphere (N2, CH4, and argon, if present) using a radiometer to measure the CN(violet) radiation emitted in the probe's shock layer during the high-velocity portion of the entry. Radiative heating rates spectra are calculated at the probe stagnation point for altitudes near peak heating where the shocklayer gases are in chemical and thermal nonequilibrium. The analysis indicates that the sensitivity of the CN(violet) radiation to the atmospheric composition enables the mole fractions of N2, CH4, and argon to be determined to about ±0.015, ±0.003, and ±0.01, respectively. These values are much less than the current uncertainties. The maximum nonequilibrium radiative heating rate is predicted to be about half of the maximum convective heating rate. (Prior equilibrium calculations had shown that the radiative heating rate was negligible.) Thus, the beryllium heat shield currently planned may be underdesigned, because it has been developed for convective heating only. © American Institute of Aeronautics and Astronautics, Inc., 1991, All rights reserved.
H. F. Nelson et al., "Titan Atmospheric Composition By Hypervelocity Shock-layer Analysis," Journal of Thermophysics and Heat Transfer, vol. 5, no. 2, pp. 157 - 165, American Institute of Aeronautics and Astronautics, Jan 1991.
The definitive version is available at https://doi.org/10.2514/3.243
Mechanical and Aerospace Engineering
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01 Jan 1991