Space adaptation syndrome (SAS), or space sickness, is a condition experienced by around half of space travelers during adaptation to microgravity.^[1] It is related to motion sickness, as the vestibular system adapts to weightlessness.^[2]

Space sickness is caused by changes in gravitational forces, which affect spatial orientation in humans.^[2] According to Science Daily, "Gravity plays a major role in our spatial orientation. Changes in gravitational forces, such as the transition to weightlessness during a space voyage, influence our spatial orientation and require adaptation by many of the physiological processes in which our balance system plays a part. As long as this adaptation is incomplete, this can be coupled to motion sickness (nausea), visual illusions and disorientation."^[2]

Space sickness was effectively unknown during the earliest spaceflights as these were undertaken in very cramped conditions; it seems to be aggravated by being able to freely move around and so is more common in larger spacecraft. Around 60% of all Space Shuttle crew members to date have experienced it on their first flight. The world's first case is suspected to be Russian cosmonaut Gherman Titov, in August, 1961 aboard Vostok 2, who reported dizziness and nausea. The first significant, well documented cases were on early Apollo flights. Both Frank Borman, (Apollo 8) and Rusty Schweickart, (Apollo 9) experienced identifiable and fairly severe symptoms, in the latter case causing the mission plan to be modified.

As with motion sickness, symptoms can vary from mild nausea and disorientation, to vomiting and intense discomfort; headaches and nausea are often reported in varying degrees. About half of sufferers experience mild symptoms; only around 10% suffer severely. The most extreme reaction yet recorded was that felt by Senator Jake Garn in 1985. After his flight NASA astronauts began using the informal "Garn scale" ^[3] to measure reactions to space sickness. In most cases, symptoms last from 2?4 days.

Modern motion-sickness medications can counter space sickness but are rarely used because it is considered better to allow space travelers to adapt naturally over the first day or two than to suffer the drowsiness and other side effects of medication. However, transdermal dimenhydrinate anti-nausea patches are typically used whenever space suits are worn because vomiting into a space suit could be fatal. Space suits are generally worn during launch and landing by NASA crew members and always for extra-vehicular activities (EVAs). EVAs are consequently not usually scheduled for the first days of a mission to allow the crew to adapt, and transdermal dimenhydrinate patches are typically used as an additional backup measure.

References

1. ↑ Tony Quine (2007): Addicted to space: An appreciation of Anousheh Ansari, Part II appeared in Spaceflight, a publication of the British Interplanetary Society (BIS), ISSN 0038-6340, Volume 49, Number 4, April 2007, page 144.
2. ↑ ^{a b c} "Why Do Astronauts Suffer From Space Sickness?" ScienceDaily (May 23, 2008)
3. ↑ http://www.jsc.nasa.gov/history/oral_histories/StevensonRE/RES_5-13-99.pdf, pg 35, Johnson Space Center Oral History Project, interview with Dr. Robert Stevenson:

   "Jake Garn was sick, was pretty sick. I don't know whether we should tell stories like that. But anyway, Jake Garn, he has made a mark in the Astronaut Corps because he represents the maximum level of space sickness that anyone can ever attain, and so the mark of being totally sick and totally incompetent is one Garn. Most guys will get maybe to a tenth Garn, if that high. And within the Astronaut Corps, he forever will be remembered by that."

See also

• Human adaptation to space
• Human spaceflight

de:Raumkrankheit fr:Mal de l'espace ja:???? pt:Síndrome de adaptação ao espaço pl:Choroba kosmiczna

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