Human and Psychological Factors in Long-Duration Spaceflight

Introduction to Spaceflight Adaptation and Human Factors

Physical adaptation impacts of spaceflight include the onset of symptoms in between 40% and 50% of crewmembers during the initial days of microgravity exposure. Space adaptation sickness is a condition expressed through symptoms such as headache, disorientation, and nausea. While these symptoms can be alleviated through pharmacological interventions and exercise, others present significant obstacles to maintaining astronaut health during longer-duration missions. Spaceflight performance and psychological aspects are particularly important in the deployment of interventions for overall mission operations (Whitmire, Leveton, Shea, & Schmidt, 2005).

Although many definitions exist for the "Human Factors" discipline, astronautic explanations focus on the interfaces between technology and humans. An illustration of human factors issues includes the determination of various forms of alarms in aircraft cockpits, where the goal is to distinguish emergencies from routine alerts. Research demonstrates that female voices are more readily noticed and salient to pilots compared to simple tones. Human factors engineers and psychologists apply principles related to how humans operate — including hand-eye coordination (psychomotor), cognitive ability, memory, and information processing capabilities — to promote the development of intelligent machine and tool designs in environments where humans are expected to work (The Institute of Medicine, 2014).

Behavioral Health Risks and Contributing Factors

Identifying predictors and other factors contributing to behavioral risks, psychiatric disorders, and conditions within each mission stage increases the efficacy of treatment and prevention for such conditions. Most of these factors continue to play essential roles in establishing the occurrence of psychiatric disorders or behavioral conditions (Whitmire, Leveton, Shea, & Schmidt, 2005). Key elements of consideration include circadian rhythm and sleep disruption, negative emotions, personality, and physiological changes occurring through adaptation to microgravity conditions. Additional elements include monotony, daily personal irritants, lack of autonomy, fatigue, the physical conditions of space life, workload, organizational and cultural factors, interpersonal and family issues, and environmental factors. Positive or salutary aspects of spaceflight also contribute to behavioral health outcomes.

A number of factors develop both salutary and detrimental aspects — teamwork being one example. Another consideration involves the giving and receiving of social support, coupled with leadership responsibilities placed on individuals. Existing approaches to the prevention of psychiatric disorders and behavioral conditions begin with selection and post-flight continuity. Astronaut selection systems aim to identify individuals whose diagnoses are incompatible with the demands of spaceflight, as well as those believed to have favorable psychological profiles for the role (The Institute of Medicine, 2014). Countermeasures comprise alternative forms of defense and prevention against behavioral conditions and psychiatric disorders across pre-flight, in-flight, and post-flight phases. For instance, psychological support services should be made available to crewmembers and their families at all stages of a mission.

Exercise, Physiological Countermeasures, and Habitability

A number of exercise regimes are prescribed as more effective than others in attaining fitness goals during spaceflight. Some regimes focus on a single area of fitness while neglecting others. For instance, high-contact-force treadmills make running an effective approach for bone maintenance, musculature conditioning, and cardiovascular conditioning. This differs distinctly from vigorous cycling, which increases bone mineral reabsorption into the bloodstream (The Institute of Medicine, 2014). Increasing the ground reaction forces applied to the foot has a greater influence on bone density than simply increasing running or walking time, with those forces transmitted through the legs. Resistance training devices together with space station exercise programs offer promise for addressing these issues. Various body-loading equipment can impart gravity-like forces into the human body while stimulating physiological responses, yielding benefits for cardiovascular, skeletal, and muscular fitness. A key challenge in implementing these scientific advances is the inadequate resources available to make such equipment comfortable and practical for regular use.

Achieving the necessary engineering and technological advances requires increased physiological and biomedical awareness of stressors linked to the operating environment. A broad range of physiological conditions arise from spaceflight, including space adaptation sickness, fluid shifts, cardiovascular de-conditioning, and bone demineralization. The development of biomedical and physiological countermeasures represents efforts to overcome these critical stressors, promoting the sustainability of human presence in spaceflight for longer periods and enabling participation in lengthy and complex missions (Whitmire, Leveton, Shea, & Schmidt, 2005).

Operational habitability involves developing strategies that address the integration, support, and design of environmental, mission, machine, and human elements. These strategies promote optimal performance, psychological and physical health, and safety during long-duration spaceflight. Habitability encompasses mission qualities that enable living and working within safer and more productive environments. Habitability specialists provide support in areas such as command structure, architecture, communications, acoustics, dining, clothing, group interaction, and crew interface and display design (Wickman, 2006).