Aerothermodynamic Design & Characterization for a Typical Lunar Sample Return Module

Indian Space Research Organization is gearing up for the next step in lunar exploration - a sample return mission. Targeted to bring a finite mass of the lunar regolith, this complex mission will feature a stack of spacecrafts, including the Lunar Sample Return Module. The said module will house the necessary retrieval and stowage mechanism for lunar soil sample, and adequate thermal protection and control systems to survive Earth’s reentry. This paper describes the evolution of aerodynamic design of said sample return module, considering the severe hypersonic nature of the flow during reentry. RANS based CFD computations are carried out to ascertain aerodynamic characteristics of the reentry module in terms of drag, pitching moment and hypersonic L/D. Further, the paper also highlights the configuration studies, where the external shape of the return module is varied to understand the effect of different geometry shapes on the reentry aerodynamic characteristics. Both forward and aft geometry shape variation is considered. The configuration studies bring out a possibly better alternative to a conventional sample return module, called hereafter as module “X” and “C” respectively. As hypersonic reentry poses severe aerothermodynamic heating, convective heat flux studies have been carried out for the both “C” and “X” reentry configuration. Remarkably, configuration “X” has a much lower heat flux as well, compared to configuration “C”. The added benefit of lower reentry convective heat flux and desirable aerodynamic characteristics make configuration “X” much attractive as compared to configuration “C”. CFD simulation methodology, grid and solver settings are described in detail in the paper, and are highlighted to explain the advantages of configuration “X”. Design exercises are complimented with appropriate validation studies for convective heat flux, which bring good confidence into the results and understanding obtained.