Astronaut nuclear safety: A concept for managing crew risks when using space nuclear power systems

Space nuclear power systems can provide transformational, enabling capabilities for human space exploration missions to the Moon, Mars, and beyond. Radioisotope power systems can provide heat for lunar night survival and electricity for long-duration operations of distributed landers and rovers to support crewed activities. Fission reactors can power crewed surface bases or provide interplanetary propulsion with speeds that minimize travel time. However, widespread use of space nuclear power systems in direct support of astronaut operations calls for a concerted and holistic focus on the impacts on crew safety. Safety risks and management approaches may vary across a mission lifecycle, such as during launch, transport, or surface operations. There is no holistic approach that captures the nexus of crew safety and nuclear technologies. Existing nuclear and space safety practices are often handled separately by NASA and space nuclear technology developers, and detailed methods and standards are limited. Other space agencies, the private sector, and commercial regulators are developing space nuclear systems for the first time, yet lack cross-cutting analytical approaches. This paper addresses this gap by evaluating how nuclear systems impact crew safety, encapsulating wide-ranging concerns into the new concept of “astronaut nuclear safety.” The paper contributes a concept to understand and manage these broad concerns, derived from an application of the Lifecycle Mission Safety Framework. It identifies five archetype scenarios of astronauts interacting with space nuclear systems and characterizes four areas of crew risk: radiation dose during nominal operations, radiation exposure during off-nominal operations, non-nuclear hazards such as extreme thermal temperatures, and crew safety from overall system reliability.