Hybrid multilayer radiation shielding for lunar habitats: material integration, encapsulation strategy, and optimization against GCR and SPE

The establishment of a permanent human presence on the lunar surface requires a robust habitat radiation-shielding strategy to mitigate exposure to galactic cosmic rays (GCRs) and solar particle events (SPEs). In this study, we propose a shielding-material integration technique for a hybrid multilayer lunar habitat configuration. The concept is based on an encapsulation strategy consisting of square and honeycomb-shaped pockets stitched into a Kevlar-49 layer. The selected shielding materials are first sealed in protective bags, inserted into the pockets, encapsulated between two Kevlar layers, and then covered with lunar regolith. Radiation transport analysis was performed using the On-Line Tool for the Assessment of Radiation in Space (OLTARIS). First, the dose–depth profile of lunar regolith with thicknesses ranging from 0 to 40 cm, combined with a fixed 5 cm Kevlar layer, was evaluated. The results show that the radiation dose decreases initially but increases beyond a threshold thickness of approximately 25 cm of total shielding due to the buildup of secondary particles. To address this effect, three classes of shielding materials were investigated for multilayer optimization: phase change materials (PCMs), hydrogen-rich materials, and specialized functional materials. For each configuration, dose equivalent (DE) and effective dose equivalent (EDE) were calculated for galactic cosmic ray (GCR) spectra under both solar-maximum and solar-minimum conditions, as well as for all available solar particle event (SPE) models. The results suggest that the proposed hybrid multilayer configuration is capable of reducing EDE values below the NASA operational radiation exposure criteria for both GCR and SPE models. Among the material classes examined, hydrogen-rich materials showed the best overall performance and offered flexibility for multifunctional habitat applications in which radiation shielding must be balanced with structural and operational requirements. The proposed multilayer design effectively attenuates the secondary-particle flux observed in the regolith–Kevlar baseline configuration, thereby improving the habitat’s overall protective capability. Overall, this study supports the feasibility of integrating optimized hydrogen-rich materials with in situ regolith as a promising strategy for sustainable lunar habitation in a complex radiation environment.