Review of Nuclear Cross Section Models in HZETRN2020

NASA is ushering in a new age of space exploration with the Artemis missions, which include the recent, uncrewed flight of the Orion spacecraft around the moon and subsequent prospective lunar and Mars missions where crew members will face numerous spaceflight hazards. Among the many spaceflight hazards is the space radiation environment, which comprises a mixture of mostly protons, helium nuclei, and heavier ions that originate from solar activity and galactic supernovae. High energy galactic cosmic rays that arise from supernovae are deeply penetrating to spacecraft and crew members, and, therefore, represent a difficult shielding challenge. Health risks associated with radiation exposure include carcinogenesis, acute and late central nervous system effects, and circulatory diseases of the heart and vasculature. NASA has developed an efficient deterministic radiation transport code, known as HZETRN2020, to describe the propagation of particles from the ambient space radiation environment—and any secondary particles produced from their successive nuclear collisions—through shielding materials and human tissue. The particle fluxes obtained from this code are then used to evaluate the space radiation exposure to crew members and measures of risk that are needed for mission planning. Fluxes depend on the accuracy of both the radiation transport algorithms and nuclear physics models. This technical report reviews the deterministic radiation transport algorithms and nuclear cross section models that are currently employed in HZETRN2020 and is the first step toward assessing the gaps in NASA’s nuclear physics codes.