Geant4-based radiation hazard assessment for human exploration missions

Human exploration missions in the Solar System will spend most of the time in deep space, without the shielding from the Earth’s magnetic field and hence, directly exposed to Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE). Both GCR and SPE fluences have been used to calculate the dose deposited on a water slab phantom using MULASSIS, a program based on the Geant4 Monte Carlo particle transport code. Doses from several extreme SPE events and from a GCR model are calculated for different shielding materials and thicknesses using a planar slab geometry and compared to current dose limits for space operations. Cross-comparison of MULASSIS with HZETRN (a deterministic code) has also been performed for SPE and GCR environments showing an overall reasonable agreement between both codes.