Loss of muscle power makes it extremely difficult, if not impossible, for astronauts to climb through emergency egress hatches or create unconventional exit spaces in the case of a crash upon landing.

Additionally, bone resorption and inadequate hydration in space can lead to the formation of kidney stones, and subsequent sudden incapacitation due to pain.

[7] If this were to occur during critical phases of flight, a capsule crash leading to worker injury and/or death could result.

[8][9] Orthostatic intolerance can lead to temporary loss of consciousness due to the lack of pressure and stroke volume.

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.

In such cases, and in contrast to space sickness, one's surroundings seem visually immobile (such as inside a car or airplane or a cabin below decks) while one's body feels itself to be in motion.

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.

For most (but not all) kinds of terrestrial motion sickness, that can be achieved by viewing one's surroundings from a window or (in the case of seasickness) going up on deck to observe the seas.

And within the Astronaut Corps, he forever will be remembered by that.Garn's purpose on the mission was in part to subject him to experiments on space motion sickness.

[20] Apart from that record, space motion sickness was effectively unknown during the earliest spaceflights (Mercury, Gemini series) probably because these missions were undertaken in spacecraft providing very cramped conditions and permitting very little room for head movements; space sickness seems to be aggravated by being able to freely move around, especially in regard to head movement, and so is more common in larger spacecraft.