Space adaptation syndrome

Space adaptation syndrome (SAS), or space sickness, is a condition experienced by around half of astronauts and cosmonauts during adaptation to microgravity. It is related to motion sickness, as the vestibular system adapts to weightlessness.

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 astronauts currently experience it on their first flight; the first case is now suspected to be Gherman Titov, in August, 1961 onboard Vostok 2, who reported dizziness and nausea. However, the first significant cases were in early Apollo flights; Frank Borman on Apollo 8 and Rusty Schweickart on Apollo 9. Both experienced identifiable and reasonably 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, astronauts began using the "Garn scale" 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 — it is thought that having astronauts adapt over the first day or two is preferable to a medicated (and drowsy) state during a mission. However, transdermal dramamine anti-nausea patches are typically worn during launch and landing by NASA astronauts.

Mission-critical activities (especially EVA, during which vomiting could be fatal) are generally not scheduled for the first days of a mission, to allow crews to adapt to zero-g. Due to the danger posed by possible vomiting in an extravehicular suit, transdermal dramamine patches are also typically used during EVAs, as an additional backup measure.