Background: Long-duration space missions introduce complex physiological, psychological, and operational challenges due to microgravity, radiation, isolation, and confined environments. Ensuring astronaut health and mission success requires adaptive, evidence-based, and internationally harmonised selection protocols.
Objective: This narrative synthesis evaluates current astronaut selection criteria for long-duration missions, critically examining physiological, psychological, and technical domains, identifying limitations of existing frameworks, and highlighting emerging technologies and international considerations.
Methods: Peer-reviewed literature, agency standards, and technical guidance from NASA, ESA, JAXA, Roscosmos, and commercial entities were reviewed. Key physiological stressors, behavioural competencies, and skill requirements were linked to exclusion and competency criteria, with a focus on actionable recommendations, comparative analysis, and emerging AI- and digital twin–enabled assessment tools.
Results: Critical selection domains include musculoskeletal and cardiovascular resilience, vestibular and immune system integrity, cognitive and emotional stability, leadership and teamwork capabilities, and advanced academic and operational competence. Comparative analysis reveals variability across agencies, highlighting gaps in mission-specific thresholds, duration-based criteria, and integration of emerging countermeasures. AI-assisted monitoring and digital twin simulations offer transformative potential for continuous risk assessment and personalised adaptation.
Conclusion: Developing space programs should implement evidence-informed, adaptive selection frameworks that integrate physical, psychological, and technical competencies, harmonised international standards, and emerging technologies. Prospective evaluation, continuous monitoring, and tiered, mission-specific criteria are essential to optimise safety, performance, and operational success on long-duration missions.