Until the radiation hazards to astronauts can be controlled or otherwise mitigated by physical shielding, a 1998 National Research Council report states, long-duration space travel should be postponed (SSB and NRC, 1998a). Even if an effective physical radiation shield is developed, it in no way diminishes the need for clinical study, including monitoring of crewmembers’ exposures, long-term medical follow-up, and the development of preventive medical treatments to make astronauts more resistant to deep space-induced radiation damage. The anticipated cumulative time-dependent effects that both bone mineral density loss and radiation are anticipated to exert, furthermore, emphasize the need to develop alternative propulsion systems to decrease space travel time and the effects of microgravity and radiation from deep space.
Long-duration space travel can also be expected to pose risks of psychological and social stresses because of isolation, confinement, and living in cramped quarters for long periods of time. Without significant engineering improvements to the design of the spacecraft environment so that it is more bio compatible, there will likely be high noise levels, less than optimal light, and diminished privacy. In the view of some experts, these and other psychological stresses could turn out to be the most worrisome risk of all to astronaut health (SSB and NRC, 1998a, 2000). Habitability—or, more correctly, biocompatibility—thus must be an important initial consideration in spacecraft design.
Astronaut health requires a continuum of preventive, therapeutic, and rehabilitative care on the ground, during space travel, and upon the return from space travel. The continuum includes normal health maintenance and care for the physiological adaptations that humans experience as a result of the extreme environment of space (see Chapter 2). Furthermore, it must address a large variety of the minor and major medical problems, including psychiatric and behavioral health problems, and surgical problems that can develop among members of a group of individuals over extended periods of time in normal and extreme terrestrial environments (astronauts in training and between missions) and during extended periods in space beyond Earth orbit, which is the particular focus of this report (see Chapters 3, 4, and 5).
Although the preventive and rehabilitative aspects of health care are of utmost importance to maintaining a healthy, active astronaut corps, this chapter focuses on principles of health care during future long-duration space travel and habitation, for example, during exploration-class missions to Mars or colonization of Earth’s moon. Other components of the continuum of astronaut health care before, during, and after space travel are