Fatigue and sleep loss during spaceflight

Human spaceflight often requires astronaut crews to endure long periods without rest. Studies have shown that lack of sleep can cause fatigue that leads to errors while performing critical tasks. Also, individuals who are fatigued often cannot determine the degree of their impairment. Astronauts and ground crews frequently suffer from the effects of sleep deprivation and circadian rhythm disruption. Fatigue due to sleep loss, sleep shifting and work overload could cause performance errors that put space flight participants at risk of compromising mission objectives as well as the health and safety of those on board.

Chronic sleep loss can impact performance similarly to total sleep loss and recent studies have shown that cognitive impairment after 17 hours of wakefulness is similar to impairment from an elevated blood alcohol level.

It has been suggested that work overload and circadian desynchronization may cause performance impairment. Those who perform shift work suffer from increased fatigue because the timing of their sleep/wake schedule is out of synch with natural daylight (see Shift Work Syndrome). They are more prone to auto and industrial accidents as well as a decreased quality of work and productivity on the job

Ground crews at NASA are also affected by slam shifting (sleep shifting) while supporting critical International Space Station operations during overnight shifts.

During the Apollo program, it was discovered that adequate sleep in the small volumes available in the Command Module and Lunar Module was most easily achieved if (1) there was minimum disruption to the pre-flight circadian rhythm of the crew members; (2) all crew members in the spacecraft slept at the same time; (3) crew members were able to doff their suits before sleeping; (4) work schedules were organized - and revised as needed - to provide an undisturbed (radio quiet) 6-8 hour rest period during each 24-hour period; (5) in zero-gravity, loose restraints were provided to keep the crewmen from drifting; (6) on the lunar surface, a hammock or other form of bed was provided; (7) there was an adequate combination of cabin temperature and sleepwear for comfort; (8) the crew could dim instrument lights and either cover their eyes or exclude sunlight from the cabin; and (9) equipment such as pumps were adequately muffled.

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