Assessment of thermochemical nonequilibrium and slip effects for orbital re-entry experiment

Results are provided from a viscous shock layer (VSL) analysis of the re-entry flowfield around the forebody of the Japanese Orbital Re-entry Experiment (OREX) vehicle. This vehicle is a 50-deg spherically blunted cone with a nose radius of 1.35 m and a base diameter of 3.4 m. Calculations are performed for the OREX trajectory from a 105 to 48.4 km altitude range. A seven-species chemical model for air is found adequate for the flowfield analysis. However, for altitudes greater than 84 km, the low-density effects (such as thermal nonequilibrium and slip) must be implemented to accurately predict flight-inferred heat transfer rate data. At altitudes lower than 84 km, a finite surface recombination probability employed in place of a noncatalytic surface enhances the agreement between the calculations and flight data. VSL results are also compared with the direct simulation Monte Carlo predictions at high altitudes (>80 km) and the electron number density data for three altitudes in the OREX trajectory. Overall, the agreement between the flight data and calculated results is quite good.