SIMULATED RAREFIED ENTRY OF THE GALILEO PROBE INTO THE JOVIAN ATMOSPHERE

Flowfield properties and aerodynamics are computed with a direct simul ation Monte Carlo method in the rarefied flow regime during entry of t he Galileo Probe into the atmosphere of Jupiter. The objective is to p redict accurately the vehicle's drag coefficient, which is needed to a ssess atmospheric properties from the onboard atmospheric structure ex periment, where highly sensitive accelerometers will measure the drag effects to within 10(-5) m/s(2) during the initial entry phase at high altitudes. The corresponding flow rarefaction extends from the free-m olecule limit to the near-continuum transition regime (Re-infinity < 1 000). Simulation results, employing a simple radiative equilibrium sur face model, indicate that C-D varies from 2.1 at the free-molecule lim it down to 1.6 at Re-infinity = 1000. Results compared very well to th ose from ballistic-range experiments. Detailed material response of th e carbon-phenolic heat shield was then coupled directly into the DSMC code to account accurately for conductivity, heat capacity, and pyroly sis, and the simulations were repeated. The predicted pyrolysis mass e fflux was 8-14 times higher than the incident freestream mass flux and had significant effects on the drag.