Acute radiation risk assessment and mitigation strategies in near future exploration spaceflights

As more exploration spaceflights are planned to travel beyond the protective Earth magnetosphere to deep space destinations, acute health risks due to possible high radiation doses during severe Solar Particle Events (SPEs) are of greater concern to mission planners and management teams. It is expected that some degree of Acute Radiation Syndromes (ARS) symptoms may be observed, but the specific list of health risks that are relevant to exploration missions has been ambiguous and debatable in the past. This mini-review gives a brief summary of the features of radiation exposure if astronauts encounter severe SPEs beyond Low Earth Orbit (LEO), the evidence of ARS radiobiological studies at exposure levels close to recommended limits, and the shortcomings of previous dose projection approaches for ARS risk assessment. Some ARS biomathematical models, particularly those pertinent to the dose ranges that severe SPEs beyond LEO could generate, are reviewed and evaluated, focusing on their capability to predict the incidence of performance incapacitation and time-phased health effects with subsequent medical care recommendations. Using onboard active dosimeter input for estimating organ doses and likely clinical outcomes for SPEs in real time, a new strategy for ARS assessment and mitigation is described to cope with the potential threats of severe SPEs for planned deep space missions.