The goal of the Space Radiation (SR) Element is to ensure that crewmembers can safely live and work in space without exceeding acceptable radiation health risks. Space radiation differs from radiation encountered on Earth.
The main sources of space radiation are galactic cosmic rays (GCRs), which consist of protons and electrons trapped in Earth’s magnetic field and solar particle events. GCRs permeate interplanetary space and include particles with high ionizing energy. At the cellular and tissue levels, these heavy ions cause damage that is largely different from the damage caused by terrestrial radiation, such as x-rays or gamma-rays, because of their significantly higher ionizing power and associated uncertainties in quantifying biological response. Shielding against GCRs is much more difficult than shielding against terrestrial radiation because a greater mass of shielding material is required and GCRs can penetrate shielding material. Health risks from space radiation may include an increased incidence of cancer; acute radiation sickness; degenerative tissue damage; diseases such as heart disease and cataracts; and early and late central nervous system (CNS) damage. Cancer risks pose the largest challenge for exploration. The uncertainties in cancer risk projection have large impacts on exploration mission designs, limiting NASA’s ability to adjust mitigation measures such as shielding and biological countermeasures. For the CNS and degenerative risks, there are uncertainties in the dose thresholds and latency. Research is needed to optimize radiation protection practices in shielding and operational procedures to prevent acute radiation sickness. The results of space radiation studies contribute to human exploration by providing a scientific basis to accurately project and mitigate health risks from space radiation. Research in radiobiology and physics guides and supports risk assessment and protection strategies. The results will provide tools for evaluating shielding recommendations for habitats and vehicles as well as requirements for storm shelters and early warning systems for solar particle events.