Entry motion sickness (EMS) is a prevalent condition experienced by astronauts returning from missions in microgravity. Following extended durations in microgravity, an astronaut’s central processing of vestibular signals is no longer conditioned to expect gravity cues, resulting in "sensory conflict" when exposed to Earth gravity. This conflict results in motion sickness symptoms such as vertigo, difficulty concentrating, and nausea, which are then likely exacerbated by the sea-state motion during water landings as astronauts await recovery. Motion sickness poses an operational hazard for astronauts should an off-nominal situation arise requiring quick action or emergency egress. Pharmaceuticals such as scopolamine are effective in mitigating motion sickness symptoms, but between side effects such as drowsiness and concerns about stability and shelf-life for long-duration missions, they are an imperfect solution. This study aims to evaluate the efficacy of postural control and anticipatory visual cues as countermeasures for motion sickness during wave-like motion following gravity transitions.Ground-based analogs were used to simulate the gravity transition and wave-like motion experienced by astronauts during water landings. Two countermeasures were assessed during wave-like motion to determine their ability to mitigate motion sickness symptoms. For both countermeasures, subjects wore a Virtual Reality (VR) headset. The postural control countermeasure entailed having the subjects’ heads and torsos unrestrained and instructing them to try to keep their heads aligned with upright during the hour of motion, to encourage engagement of orientation control circuitry thought to be relevant for motion sickness. During the postural control countermeasure, the VR headset did not display any cues of present or future motion, but rather it had a white fixation point that remained static regardless of motion. The anticipatory visual cue countermeasure showed subjects veridical cues of self-motion as well as cues of motion in the near future, aimed to help reduce sensory conflict by providing a means for expecting upcoming sensory cues. Preliminary results suggest that active postural control reduces ocular motion sickness symptoms in subjects (p = 0.041), and that anticipatory cueing is effective at improving toleration of the motion (p = 0.033).
Countermeasures for Astronaut Entry Motion Sickness During Water Landings
2024-03-02
2806350 byte
Conference paper
Electronic Resource
English
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