Solar proton dose exposures using low-Z and high-Z materials

Solar particle events (SPEs) represent serious concerns to humans and onboard systems in space. Historically, passive bulk shielding, usually aluminum, has been used to minimize space radiation exposures and subsequent physical and biological effects. In this paper, a review of the major SPEs that have occurred in the last 50 years is presented. Prior to 1976, historical SPE particle spectra were obtained from pre-GOES (geostationary orbiting environmental satellite) spacecraft such as the IMP (interplanetary monitoring platform) -34 and -41 spacecraft. For the time period 1976 to current, the GOES SEM (space environment monitor) SPE particle data were used for several of the larger SPEs in this parametric shielding study. SPE particle spectra were calculated for LEO (low Earth orbit) and for the lunar and Mars environments. Using these particle spectra as input source terms and selected high-energy particle transport codes, both deterministic and Monte Carlo, the results of a parametric shielding study using both low-Z and high-Z materials are discussed. Multiple radiation transport codes were used to inter-compare the results for validation and to present benchmark results for the space community.