An analytical tool has been developed which enables the impact of ionizational nonequilibrium effects on outer planet entry heating to be estimated. The analysis combines recent shock-tube experiments, flowfield calculations, and planetary entry trajectory analysis. The thickness of the nonequilibrium layer and its variation around the entry body have been correlated by a reaction flow parameter over a wide range of entry conditions. The influence of nonequilibrium effects on heating during entry into Saturn and Jupiter model atmospheres has been studied and the effect of vehicle size and ballistic coefficient determined. An ionizational nonequilibrium layer of significant thickness was found to exist during portions of entry into Saturn and Jupiter warm atmospheres. However, the nonequilibrium layer was found to be thin during the peak heating portions of the trajectory and resulted in reductions in total probe heating of less than 15%.

Ionizational Nonequilibrium Heating During Outer Planetary Entries

Transport properties in a Jupiter-like atmosphere (89 mol % hydrogen and 11 mol % helium) are obtained by using the method of the kinetic theory of gases. The transport collision integrals are calculated by fitting various two-body semiempirical interaction potentials for which the collision integrals are tabulated to ab initio quantum mechanical calculations of the two-body interactions. The collision integrals are used to calculate the binary diffusion coefficients, viscosity, and 'total' thermal conductivity of the pure gases and the gas mixtures at 1-atm pressure from 1000 K to 25,000 K.

Transport properties in the Jovian atmosphere

Entry trajectories, decelerations, and heating and heat shielding requirements of probes entering the atmospheres of Uranus and Neptune at velocities up to 26.5 km/s were studied. Much of the Galileo Jupiter probe technology was applicable to these outer-planet probes; therefore, the same configuration was used. Steep (ballistic) entry flight-path angles were needed to facilitate communication from the probes to the spacecraft during atmospheric descent. The Galileo probe's 400 g maximum deceleration structural design was used to define the maximum entry angles for the Uranus and Neptune probes. The carbon phenolic heat shield material used on the Galileo and the successful Pioneer-Venus probes was selected. Turbulent boundary-layer convection dominated the heating of the Uranus and Neptune probes; radiative heating was negligible by comparison. The peak heating rates were found to be about 6 kW/cm, or approximately 25% of the Galileo probe's expected maximum value. The forebody heat shield mass fractions for these outer-planet probes were found to vary from about 0.08 to 0.16 for entry velocities from 22 to 26.5 km/s. By comparison, the Pioneer-Venus probes' heat shield mass fractions ranged from 0.10 to 0.13, and the Galileo probe's forebody value is 0.43.

Uranus and Neptune atmospheric-entry probe study

Correlation of hypersonic stagnation point heat transfer at low Reynolds numbers

The influence of precursor heating on viscous chemical nonequilibrium radiating flow around a Jovian entry body is investigated. Results obtained for a 45-degree hyperboloid blunt body entering Jupiter's nominal atmosphere at zero angle of attack indicate that the nonequilibrium radiative heating rate is significantly higher than the corresponding equilibrium heating. The precursor heating, in general, increases the radiative and convective heating to the body, and this increase is slightly higher for the nonequilibrium conditions.

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Effects of precursor heating on chemical and radiative nonequilibrium viscous flow around a jovian entry body

Computer program calculates thermodynamic properties from basic spectroscopic data. Program capacity is a mixture of 100 different species composed of ten different elements. The output is a complete thermodynamic and chemical description of the gas.

/pdf/a-program-for-computing-shock-tube-gas-dynamic-properties-1kaiuwwiap.pdf

W. A. Menard

Papers

A program for computing shock-tube gas dynamic properties