CAD Model of Astronaut Radiation Exposures During EVA: Nominal and Extreme Scenarios

Trapped protons and electrons in the low earth orbit (LEO) environment of the International Space Station (ISS) encountered during extra-vehicular activity (EVA) may contribute significantly to the cumulative exposure sustained by crew during extended stay missions. A recently developed CAD model of the U. S. Shuttle Space Suit is used to define the shielding properties inherent in the space suit. The model incorporates 28 separate components of the suit, with particular attention given to the helmet and backpack assemblies. Proton and electron energy spectra are taken from the NASA AP8 and AE8 environment models for solar maximum and minimum, and a simulated magnetic storm condition is derived from a 3-sigma projection of the nominal condition. Heavy-ion and electron transport codes developed at NASA-Langley are used in conjunction with the variety of space suit materials, including constituents containing metallic and non-metallic compounds as well as organic polymers. Human geometry is represented by the well-established Computerized Anatomical Male and Female (CAM and CAF) models. Dosimetric quantities are evaluated for several skin and blood-forming organ points, as well as for ocular lens and other sensitive organs. The final integrated doses are determined from integration of the angular distribution of exposures around the target points.