Why do astronauts suffer from space sickness?

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

Instrument to make detailed measurements of sun activity
For five years, Stanford research physicist Phil Scherrer and his team have raised a sophisticated space telescope with the attention a parent gives to a child, preparing it for the day when it flies away on a satellite to study the weather on the sun—and maybe save an astronaut from dying of radiation sickness.
Laser can spot illness before symptoms appear
It may not rank among the top 10 causes of death, but decompression sickness can be fatal. Instead of waiting for symptoms to appear, a University of Houston professor is developing a laser-based system that can diagnose the sickness in a matter of seconds.
New method helps safeguard astronauts by forecasting space radiation hazards with up to one hour advance warnings
One of the greatest threats to human space exploration is the sudden, unpredictable occurrence of radiation outbursts from the Sun. Researchers have long sought a method for predicting when the hazardous particles from extreme solar events, such as flares, coronal mass ejections and radio bursts, would reach humans or technology in space.
Mars mission Risk 29: Scientists research ways to reduce radiation-induced brain damage
Among the gravest risks of a manned flight to Mars ranks the possibility that massive amounts of solar and cosmic radiation will decimate the brains of astronauts, leaving them in a vegetative state, if they survive at all.
Odd list of body parts: which parts are most sensitive to solar flares?
Picture this: An astronaut, on the Moon, hunched down over a rock, hammer in hand, prospecting. Suddenly, over his shoulder, there's a flash of light on the sun.
Solar activity can be surprisingly good for astronauts
Last month, the sun went haywire. Almost every day for two weeks in early September, solar flares issued from a giant sunspot named "active region 798/808." X-rays ionized Earth’s upper atmosphere. Solar protons peppered the Moon. It was not a good time to be in space. Or was it?
Greg Olsen To Perform Research On ISS For European Space Agency
Space Adventures announced Tuesday a science agreement with the European Space Agency, for a research program to be performed with Greg Olsen, Ph.D. who will visit the International Space Station next month.
US game designer blasts into space with DNA cargo
(AP) -- An American computer game designer reached space Sunday, fulfilling a long-deferred childhood dream that began with the flight of his astronaut father.

Why do astronauts suffer from space sickness?

Related stories:

News discussion: