Why do astronauts suffer from space sickness?

May 21, 2008

Centrifuging astronauts for a lengthy period provided researcher Suzanne Nooij with better insight into how space sickness develops, the nausea and disorientation experienced by many astronauts. Nooij defended her PhD theses on this subject at Delft University of Technology (TU Delft, The Netherlands) on Tuesday 20 May.

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.

This ‘space sickness’ or Space Adaptation Syndrome (SAS), is experienced by about half of all astronauts during the first few days of their space voyage. Wubbo Ockels, the first Dutchman in space in 1986, also suffered from these symptoms. In his capacity as TU Delft professor, Ockels was PhD supervisor for Suzanne Nooij’s research.

Interestingly, SAS symptoms can even be experienced after lengthy exposure to high gravitational forces in a human centrifuge, as is used for instance for testing and training fighter pilots. To experience this, people have to spend longer than an hour in a centrifuge and be subjected to gravitational forces of three times higher than that on Earth. The rotation is in itself not unpleasant, but after leaving the centrifuge about half of the test subjects experience the same symptoms as caused by space sickness.

It also turns out that astronauts who suffer from space sickness during space flights also experience these symptoms following lengthy rotation on Earth. This means that these symptoms are not caused by weightlessness as such, but more generally by adaptation to a different gravitational force.

Suzanne Nooij has studied these effects closely using the human centrifuge at the Centre for Man and Aviation in Soesterberg. Her results confirm the theory that both types of nausea (space sickness and after rotation) are caused by the same mechanism and also provide better insight into why the symptoms arise.

Logically, Nooij focused her research on the organ of balance. This is located in the inner ear and comprises semi-circular canals, which are sensitive to rotation, and otoliths, which are sensitive to linear acceleration. It has previously been suggested that a difference between the functioning of the left and right otolith contributes to susceptibility to sickness among astronauts. If this is the case, this should also apply after lengthy rotation.

Nooij tested this otolith asymmetry hypothesis. The otolith and semi-circular canals functions on both sides were measured of fifteen test subjects known to be susceptible to space sickness. Those who suffered from space sickness following rotation proved to have high otolith asymmetry and more sensitive otolith and canal systems. These people could not be classified as sensitive or non-sensitive on the basis of this asymmetry alone, but could on the basis of a combination of various otolith and canal features. This demonstrates that the entire organ of balance is involved in space sickness and that it probably entails complex interactions between the various parts of the organ of balance.

Source: Delft University of Technology

Explore further: Book shows how space station research offers "benefits for humanity"

Related Stories

Working out in artificial gravity

July 2, 2015

Astronauts on the International Space Station (ISS) have a number of exercise options, including a mechanical bicycle bolted to the floor, a weightlifting machine strapped to the wall, and a strap-down treadmill. They spend ...

Weightless US teachers eye giant science leap

November 17, 2011

"Excited," "nervous," "terrified" -- just three emotions described by a group of US teachers about to take a dizzying "weightless" flight all for the cause of science, naturally.

Recommended for you

Dense star clusters shown to be binary black hole factories

July 29, 2015

The coalescence of two black holes—a very violent and exotic event—is one of the most sought-after observations of modern astronomy. But, as these mergers emit no light of any kind, finding such elusive events has been ...

Image: Hubble sees a dying star's final moments

July 31, 2015

A dying star's final moments are captured in this image from the NASA/ESA Hubble Space Telescope. The death throes of this star may only last mere moments on a cosmological timescale, but this star's demise is still quite ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

earls
not rated yet May 21, 2008
Because they go into Space.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.