Radiation-shielding requirements on long-duration space missions

An analysis of radiation shielding requirements on long duration space missions is presented. The report finds the principal radiation hazards to be galactic cosmic radiation (cosmic rays) and radiation from solar flares. Galactic cosmic radiation is a continuous source of radiation delivering a dose equivalent to the blood-forming organs varying from 20 REM/year to 50 REM/year over the 11-year solar cycle. Solar flares are randomly distributed events that are occasionally associated with lethal particle fluxes. The following recommendations are made: investigate alternative shielding materials that may be more effective against radiation hazards discussed here; a solar-flare storm shelter with a minimum of 7.5 cm aluminum shielding (or shielding of equivalent effect) is required at all times for space flights outside the magnetosphere. Spacecraft designed to transport people outside the magnetosphere for long durations during solar minimum must provide at least 7.5 cm aluminum shielding of all living spaces. Acceptable dose limits for the full-scale exploration and industrialization of space must be studied.