Abstract:
As the lunar exploration capsule reentries with the second cosmic speed, serious chemical reactions and ionization occur in the surrounding atmosphere, and the communication blackout traditionally happened in continuum flows extends widely to the rarefied regime. Based on our own developed DSMC computation platform based on weighting factor scheme for trace species, the rarefied air ionization of lunar exploration type capsule is investigated, including the first reentry, first jump-out as well as second reentry processes in rarefied flow regimes, with an open configuration and simulation flying conditions. The communication blackout starting altitudes are predicted due to the electron number density, and the results behave excellent agreement with the flight observations, with errors smaller than 2 km. The results also reveal that, different from the associative ionization for slender body such as RAM-C Ⅱ, the main ionization source of the reentry for large blunt body like the lunar exploration type capsule is the direct ionization due to the collision between N, O and neutral molecules or atoms.