Radiation Shielding

For terrestrial exposure the three pillars of radiation protection are time, distance, and shielding: limit your time of exposure to the radioactive source or environment, increase your distance from a source or environment, and add material shielding between yourself and the source or environment. For space applications, the primary defense is shielding. Time enters into the calculations in the sense that, where feasible, one may choose to minimize time in lightly shielded areas compared to time spent in more heavily shielded accessible areas. For example, in situations such as Extra Vehicular Activity (EVA) or surface excursions you may consider returning to successively more shielded regions as the radiation background gets or is reliably forecast to become more intense (from space suit to transport vehicle to habitat to storm shelter within habitat, for example).