Long-duration spaceflight poses many challenging technical and non-technical problems that must be addressed. Past experience with long space missions has shown that the medical and psychological issues in the human factors realm that may arise are serious enough to require high-level consideration in the overall systems development process. <p> An essential aspect of the total systems development process for long-duration space missions entails the conception of a variety of countermeasures to combat the degradative effects of microgravity, isolation and confinement. These effects should be considered within a larger mission/systems framework. Additional factors within a broad systems perspective include the notion that context is an important attribute of the overall system state and may directly affect the astronauts' psychological health and the physical ability to perform required tasks. <p> A review of the literature in the psychosocial and medical realms is presented as these concerns impact the human factor within the macro-system goal of successful long-duration spaceflight mission completion. / Master of Science