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In order to estimate the exposure to a crew in space, there are three essential steps to be performed: first, the ambient radiation environment at the vehicle must be characterized; second, the mass distribution properties of the vehicle, including the crewmembers themselves must be developed, and third a model of the interactions of space radiations with matter must be employed in order to characterize the radiation field at the dose point of interest. The Space Radiation Analysis Group (SRAG) at the NASA, Johnson Space Center carries the primary responsibility for the operational radiation protection support function associated with manned space flight. In order to provide support during the various planning, execution, and analysis/recording phase activities associated with a given mission, tools have been developed to allow rapid, repeatable calculations of exposure on orbit.

Major improvements have been completed in the approach to analyses and simulation of spacecraft radiation shielding and exposure. A Computer-Aided Design (CAD)-based system has been developed for determining the amount of shielding provided by a spacecraft and simulating transmission of an incident radiation environment to any point within or external to the vehicle. Shielding analysis is performed using a customized ray-tracing subroutine contained within a standard engineering modeling software package. This improved shielding analysis technique has been used in several vehicle design programs such as a Mars transfer habitat, pressurized lunar rover, and the redesigned international Space Station. Results of analysis performed for the Space Station astronaut exposure assessment are provided to demonstrate the applicability and versatility of the system.