Simulated Rarefied Entry of the Galileo Probe into the Atmosphere of Jupiter

摘要

Flowfield properties and aerodynamics are computed with a direct simulation Monte Carlo (DSMC) method in the rarefield flow regime during entry of the Galileo Probe into the atmosphere of Jupiter. The objective is to predict accurately the vehicle's drag coefficient that is needed to assess atmospheric properties from the onboard Atmosphere Structure Experiment 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 molecule limit to the near continuum transition regime (Re_infinity < 1000). Simulation results, when employing a simple radiative equilibrium surface model, indicate that C_D varies from 2.1 at the free molecule limit down to 1.6 at Re_infinity = 1,000. Results are compared to those from ballistic range experiments. Detailed material response of the carbon phenolic heat shield was then coupled directly into the DSMC code to account accurately for conductivity, heat capacity, and pyrolysis, and the simulations were repeated. The predicted pyrolysis mass efflux was 8-14 times higher than the incident freestream mass flux and had significant effects on the drag.