Astronauts are exposed to a unique environment during space travel. A few examples include radiation, isolation, confinement and a lack of gravity. This affects their physiology in many ways, including cardiovascular and musculoskeletal deconditioning, vision changes and immune dysfunction.

Over the past 60 years of human space exploration, astronauts have had a range of different backgrounds and experiences. Space travelers have come from different parts of the world, including North America, Europe and Asia. They have a variety of occupations and education levels and are of different ages, sexes and genders. Crews have been selected in alignment with different mission profiles, with some missions focusing on science, assembly or operations.

With the advent of commercial programs and civilian astronauts, the definition of space travelers—that is, “astronauts”—needs to be revisited. Scientists also need to research the adaptations that civilians may experience from space travel, as compared with traditionally trained astronauts.

Space travelers experience various adaptations, including changes in spatial orientation, head-eye and hand-eye coordination, and balance and locomotion challenges in space. These can all be grouped under the term “space motion sickness.” Space travelers’ weight-bearing bones lose an average of 1% to1.5% of mineral density per month during spaceflight. In addition, fluid shifts to the head, leading to increased pressure around the eyes and vision problems.

NASA scientists and other researchers have developed various methods to minimize these effects, including prescribed exercise, medicines and non-invasive measurement techniques (looking at their blood, urine, saliva, etc.). However, there needs to be more research with the awareness that spaceflight missions of various lengths and at different locations in space (for example, low-Earth orbit versus the moon) can lead to different kinds of physiological adaptations. Moreover, there are differences in how women and men adapt to space, which requires further research as we aim to send the first woman to the moon through the Artemis program.

We are just beginning to understand and learn about adaptations in civilian astronauts. A collaborative, multi- and inter-disciplinary space biomedical project has shown how civilians and their biological systems adapt to the spaceflight environment as part of the Inspiration 4 mission. Research topics include studies on cognition (how we think and learn), mitochondria, analysis of individual immune cells, effects of radiation, chromosome adaptations and spacecraft environment.

These research findings have been released in coordination with the summer 2024 launch of the second civilian astronaut mission, Polaris Dawn. They are a follow-up to general spaceflight adaptations studies released in 2020.

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