Space adaptation syndrome

Space adaptation syndrome is a temporary cluster of nausea, dizziness, and disorientation that can occur as the nervous system adjusts to weightlessness.

Vestibular system: The inner-ear organs and neural pathways that sense head motion, orientation, and balance. Its gravity-sensitive signals change in weightlessness and contribute to disorientation.
Space motion sickness medication: Medication used to prevent or reduce nausea and related symptoms during spaceflight. Drugs can manage symptoms when adaptation alone is insufficient for a crew member’s duties.
Mal de debarquement syndrome: A persistent sensation of rocking or swaying that can follow exposure to passive motion, especially sea travel. It follows motion exposure, whereas space adaptation syndrome begins during entry into weightlessness.
Space Shuttle: NASA’s reusable crewed spacecraft system, operated from 1981 to 2011. Shuttle missions helped document symptoms during the transition into and out of weightlessness.
Sensory conflict theory: A theory that motion sickness arises when sensory signals about movement conflict with one another or with expectations. It explains why altered vestibular and visual cues can provoke nausea in orbit.
Scopolamine: A medication that blocks muscarinic acetylcholine receptors and can prevent motion sickness. It is among the medicines used to control spaceflight-related nausea.
Spaceflight-associated neuro-ocular syndrome: A set of visual and anatomical changes observed in some astronauts during long-duration spaceflight. It is another spaceflight health condition, but involves ocular changes rather than acute motion sickness.
International Space Station: A crewed research laboratory in low Earth orbit operated through international partnership. Long-duration station missions expose how initial symptoms differ from later adaptation.
Otolith organs: Inner-ear structures that detect linear acceleration and head tilt relative to gravity. Removing the usual gravity reference changes the signals these organs provide.
Promethazine: An antihistamine with antiemetic effects used to treat nausea and motion sickness. It has been used in spaceflight to relieve severe symptoms.

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