Simulated manual spacecraft control under the influence of different gravity conditions during a parabolic flight

Abstract

BACKGROUND: Microgravity can affect cognitive performance, spatial orientation, and the precision of previously trained motor responses which are based on force vectors and vestibular signals in normal gravity. It is still controversial, whether reported performance decrements are due to microgravity or unspecific stress factors associated with space flight. Experimental evidence on the influence of microgravity on complex operational tasks comprising motor and cognitive demands is especially scarce. Therefore, we investigated the influence of varying gravity levels during parabolic flights on performance in the manual control of a spacecraft, a safety-relevant operational task. METHODS: During parabolic flights, 27 trained participants (8 women and 19 men, 18-61 years old, 9 previously exposed to a parabolic flight) performed 15 manual control tasks of varying difficulty based on the docking simulation 6df. Within this simulation, a spacecraft had to be aligned continuously with a rotating space station in fixed distance by controlling six degrees of freedom with manual levers. Each task encompassed 80 seconds centered around either the incoming or outgoing hypergravity segment of a parabola and thus included to equal parts a 0g, 1g, and 1.8g phase. We compared manual control accuracy between phases of microgravity, hypergravity, and normogravity during the parabolic flight by using a linear mixed effects model. Additionally, we assessed the effects of task difficulty and previous experience with parabolic flights on performance. RESULTS: Manual control performance was significantly impaired during microgravity phases, whereas performance did not differ between normal gravity and hypergravity. Performance differed according to task difficulty, but there was no interaction of gravity phase and difficulty. Prior experience with parabolic flights did not affect manual control performance. DISCUSSION: The decrease of manual control performance in microgravity, but not during hypergravity, suggests a higher relevance of impaired spatial orientation due to confounding vestibular signals compared to the mere change in force vectors. Even during easy tasks, participants were not able to compensate for the effects of microgravity. The results were independent of prior parabolic flight experience, indicating that novelty or increased stress are unlikely sources of impairment.