RADIATION EXPOSURE PREDICTIONS FOR LONG-DURATION-STAY MARS MISSIONS

In this study, the ionizing radiation environment is estimated, using the Mission Radiation Calculation (MIRACAL) program, for several long- duration-stay Mars missions proposed for early in the 21(st) century. Both minimum energy and fast transfer missions are evaluated and their 30-day maximum, annual maximum, and total slab skin and blood-forming organ (BFO) doses are compared. When large flares were included while the astronauts were on the surface, the delivered dose did not signif icantly contribute to the total dose (less than 4 cSv BFO dose, or 8 p ercent of the guideline annual limit, for the most energetic event sim ulated) due to the substantial protection provided by the Martian atmo sphere. However, dose delivered by large flares during transit is depe ndent on vehicle shielding and distance from the Sun. All of the fast transfer missions studied had lower total and annual maximum doses tha n the corresponding minimum energy transfer missions (on average, 30 p ercent less for missions having no large flares and the shielding thic knesses evaluated in this study). For all the missions studied, having the astronauts spend one-third of their day during transit in a 10 g/ cm(2) storm shelter resulted in an approximate 10 percent reduction in the total mission dose.