Ionizing radiation dose distributions on board habitable modules of the international space station

Future crewed missions beyond Low Earth Orbit (LEO) will involve significant radiation exposure, a hazard identified by NASA as the largest risk in long-term spaceflight requiring mitigation. The existing materials of spacecraft only attenuate a fraction of the harmful ionizing radiation particles. The first modules of the Lunar Orbital Gateway will be launched as soon as 2022 and, although similar in design to the International Space Station (ISS), will need increased radiation shielding for the protection of the crew. Locations must be identified for the placement of radiation shielding that provide the lowest mass alternative and the largest dose reduction for astronauts. Monte-Carlo simulations have been conducted using the particle transport software, GEANT4. The ISS has been used as a representative geometry for the Lunar Orbital Gateway and directional radiation exposure maps are presented for the main habitable modules.