This study discusses the physiological limitations of the human and his susceptibility to error when subjected to extended and accelerated spacecraft rolling. The context for discussion is provided by the Gemini VIII spaceflight emergency of uncontrolled and accelerated rolling which caused the premature abort of the mission. Data from this flight imply that astronaut performance was impaired due to vestibulo-ocular disturbance. Five deleterious effects are attributed to spacecraft roll acceleration: disorientation, dizziness, impaired vision, nausea, and panic. Recommendations for astronaut selection and conditioning as well as spacecraft design are proposed to minimize these effects of accelerated rolling
