Medical Concerns with Space Radiation and Radiobiological Effects

An overview is provided of the radiation health challenges associated with extended human missions into deep space with the understanding that this is a complex endeavor presently under active research and development. Hence, this chapter necessarily reflects present limitations and the need for research to make such exploration missions possible. The space radiation environment is introduced followed by a brief discussion of the radiobiology. The remainder of the chapter is focused on human health concerns from radiation exposure during extended deep space missions. Although the challenges are many, the greatest radiation-related concern from a mission perspective would be an exceptionally large solar-energetic-particle (SEP) event. Such an event, should it occur during extravehicular activity (EVA), or while in a spaceship insufficiently shielded, could potentially result in acute radiation sickness. Fortunately, radiation from SEP events can be shielded and therefore should be manageable through a combination of shielding design and early warning systems. In contrast, the ever-present chronic exposure to galactic cosmic radiation (GCR) is difficult to shield and will likely have to be accepted at some level. Although GCR produces a much lower dose rate than a large SEP event, there are significant uncertainties concerning the effects from the high-charge, high-energy (HZE) component of GCR. It has been estimated that GCR radiation may induce a significant lifetime cancer risk. It is less clear whether health effects such as cardiovascular or central nervous system problems will result from protracted GCR exposure. It is hoped that these and many other uncertainties will be reduced through research and development prior to sending humans to Mars.