Jovian Entry Research Articles

Ablation of Galileo Probe heat-shield models in a ballistic range

Several 1/24-scale models of the Galileo Probe made of carbon-phenol ic materials were flown in a ballistic range to test their ablation characteristics. Mostly radiative or all-convectiv e heating environments were produced by using argon or air as the test gas, respectively, to simulate the Jovian entry heating environments. The experimental results were compared with the theoretical predictions made using the computer codes of radiating shock layer environment (RASLE) and charring materials ablation (CMA). The experimental data obtained in argon agreed approximately with the theoretical predictions. The data for air agreed approximately with the theory when turbulence and surface roughness effects were accounted for. The data imply that the Galileo Probe heat shield was adequately designed.

Nonequilibrium radiative heating of an ablating Jovian entry probe

On etudie l'influence d'un transfert radiatif en equilibre thermodynamique non local sur le phenomene d'ecoulement autour d'un corps entrant dans l'atmosphere de Jupiter

Flowfield calculations past an entry probe with ablated nose shape

The effects of ablated nose shapes on the flowfield solutions are studied, using a time-dependent finite-difference method developed by Kumar, et al. (1979). Solutions are obtained for the laminar flow of a radiating mixture of H-He in chemical equilibrium past a blunt axisymmetric body at zero angle of attack. The freestream conditions correspond to a point on a typical Jovian entry trajectory, and the initial probe shape is a 45-deg half-angle spherically blunted cone. It is found that as nose bluntness increases, the following occur: in the nose region, shock standoff distances and radiative heating rates increase substantially; surface pressure level increases, but convective heating rates decrease.

Effects of probe shape change on flow phenomena during Jovian entry

The effects of probe shape change on the flow phenomena around a Jovian entry body is investigated. The initial body shapes considered are: 45° sphere cone, 35° hyperboloid, and 45° ellipsoid. The radiating shock-layer flow is assumed to be axisymmetric, inviscid, and in chemical and local thermodynamic equilibrium. The radiative transfer is calculated with an existing nongray radiation model that accounts for molecular band, atomic line and continuum transitions. The results indicate that the shock-standoff distance, shock temperature and density, wall pressure distribution and radiative heating to the body are influenced significantly because of the probe shape change. The effect of shape change on radiative heating of the afterbody was considerably larger for the sphere cone and ellipsoid that for the hyperboloid. For the peak heating conditions, the net radiative heating to the body was found to be highest for the ellipsoid.

Low Temperature Simulation of Subliming Boundary-Layer Flow in Jupiter Atmosphere

A low-temperature approximate simulation for the sublimation of a graphite heat shield under Jovian entry conditions is studied. A set of algebraic equations is derived to approximate the governing equation and boundary conditions, based on order-of-magnitude analysis. Characteristic quantities such as the wall temperature and the subliming velocity are predicted. Similarity parameters that are needed to simulate the most dominant phenomena of the Jovian entry flow are also given. An approximate simulation of the sublimation of the graphite heat shield is performed with an air-dry-ice model. The simulation with the air-dry-ice model may be carried out experimentally at a lower temperature of 3000 to 6000 K instead of the entry temperature of 14,000 K. The rate of graphite sublimation predicted by the present algebraic approximation agrees to the order of magnitude with extrapolated data. The limitations of the simulation method and its utility are discussed.

Effects of reduction of the ionization potential on solutions of the Rankine-Hugoniot equations for Jovian entry

The influence predictions of three different reduction-of-the-ionization-potential models (Unsöld, Ecker-Weizel and Griem) on the calculated composition of hydrogen-helium shock layers for conditions that would be encountered during entry of the Jovian atmosphere is investigated. The comparisons indicate that the Ecker-Weizel model gives the largest Δ I and Griem's the smallest. The Δ I-model influence on the composition increases as the hydrogen mass fraction, entry velocity, and ambient density increase.