How do astronauts sleep in space? Sleeping in space explained
Last Updated: October 13, 2023
In the weightless, noiseless expanse of outer space, the traditional boundaries of night and day dissolve, presenting a unique set of challenges for human physiology and behavior. Astronauts, orbiting our planet in high-tech spacecraft, must adapt to a realm where the sun rises and sets multiple times a day, disrupting the regular circadian rhythms we’re so inherently tied to on Earth.
One of the fundamental adaptations involves the act of sleep— an essential physiological process linked to a multitude of cognitive functions and overall health. But how do astronauts manage to achieve restful sleep amidst such extraordinary conditions, including weightlessness?
My article seeks to delve into the science of sleep in space, dissecting the innovative strategies, technologies, and research that enable humans to preserve this crucial aspect of health and wellbeing, even as they spin around the planet 16 times per day.
History of sleeping in space
The first human to sleep in space was Gherman Titov, a Russian cosmonaut and the second person to orbit the Earth in 1961. He slept for about one orbit and awoke to find his arms floating in space in front of him due to the lack of gravity. He remarked that sleeping in space was fine as long as you prepared yourself by arranging your appendages properly, but not everyone adjusts so quickly to sleep in space, and certainly not for extended periods.
The first American to spend an entire day in space and sleep in space was Gordon Cooper who participated in the 1963 34-hour Mercury-Atlas 9 mission, during which he orbited the Earth 22 times. Two years later, Cooper joined Pete Conrad on Gemini 5, an 8-day mission orbiting the Earth. Sleep was difficult for the two astronauts as they hurtled around the Earth in a “garbage can” as Cooper called it, a cabin the size of the front seat of a Volkswagen Beetle.
Our bodies are naturally attuned to the rhythm of the sun, called circadian rhythms, helping us fall asleep when it is dark and rise when it is the day. Disruptions to our circadian rhythm and sleep deprivation have negative effects on our physical and mental health including mood swings, weakened immune systems, increased blood pressure, poor balance, etc. Chronic sleep deprivation can lead to an increased risk of cardiovascular disease, diabetes, hypertension, and obesity.
Multiple sunrises in the course of a day interfere with our circadian rhythms. In addition, the light from the sun is much brighter in space as opposed to the sunlight here on Earth since the atmosphere filters some of it out. The discomfort of sleeping in a seat in a tiny capsule with others and hearing the sounds of the equipment of the capsule can be distracting, similar to trying to sleep on a plane.
Three astronauts sleeping in tethered sleeping bags onboard the ISS. Image Credit: NASA.
Sleeping on the International Space Station (ISS) or a space shuttle
With a goal of continuous human occupation of the ISS, humans need to be able to function and do their job for the entirety of their 6-month mission onboard the space station. NASA and other space agencies perform considerable research into how humans sleep in space to provide the best sleep experience possible for their astronauts during missions.
Today, human missions in space are either on the ISS or en route to it, though space shuttle missions outside of traveling to the ISS, such as repairing the Hubble Telescope, were common during their era. Since the end of the space shuttles, rockets have been the mode of transportation to the ISS.
What are the concerns with sleep in space? How do we address them?
On Earth, our bodies have adjusted to this 24-hour cycle relating to the rotation of the Earth which either faces us toward or away from the Sun. In space, it depends on where you are in space or where you are going, but the 24-hour day in terms of the Sun’s movement across the sky no longer exists. The ISS, at 17,110 mph, orbits the Earth about 15-16 times a day, meaning a sunrise about every 90 minutes.
This can make sleep difficult as sunlight may be streaming in and a space station or rocket is often noisy. Face masks and earplugs are often utilized to help block these outside stimuli and facilitate better sleep.
Space operations use Greenwich Mean Time (GMT or UTC) to keep a regular schedule as a compromise between mission control centers in Houston and Moscow. The astronauts keep to these hours, scheduling work, meals, and sleep accordingly.
A sample schedule might include:
- 6 a.m. wake-up call
- 90 minutes for breakfast and getting ready for the day
- 7:30 a.m. conference calls with each country’s control center
- Morning of science experiments, maintenance, and chores
- An hour for lunch
- The crew returns to work, along with exercise
- At about 5:30 p.m. final planning conference call with each control center
- 8 p.m. dinner
- 9:30 p.m. bedtime
NASA schedules astronauts for 8-8.5 hours of sleep, but crews tend to average around 6 hours due to sleep disruptions, such as needing to use the bathroom, wanting to stay up late, being excited or stressed, etc.
Many astronauts report they only need 6 hours of sleep to feel fully rested. Based on research, this might be because the body tires slower in weightless environments since the muscles don’t need to work as hard as they do on Earth with gravity.
In addition to the disruption of our circadian rhythms, the microgravity of space is unnatural for our bodies and causes a number of complications in interacting with people and objects. Without gravity, there is no up or down so you don’t need to lie down on a mattress and pillow to sleep. You can sleep in any position you want, anywhere you want.
However, objects float when weightless. Air currents from life support systems push around anything not tethered so astronauts need to be secured so they don’t float away and hit the walls, potentially hurting themselves or damaging equipment.
Astronaut Luca Parmitano sleeping onboard the ISS. Image Credit: ESA.
Where do astronauts sleep in space?
Astronauts use a tethered sleeping bag to sleep in space. On the space shuttle/ rocket, astronauts tether themselves in their sleeping bag to a seat or to any wall including the ceiling or floor. However, the only personal space is the hygiene station (the bathroom).
Former Astronaut Mike Massimino described his space shuttle missions as similar to a camping trip with buddies. Ground operations even play songs picked by astronaut family members as wake-up calls.
On the ISS, personal sleeping areas were specifically designed so that each astronaut has a space where they sleep in private. Each one is about as big as a phone booth and padded to reduce noise and sunlight. Sleeping areas are equipped with a sleeping bag tethered to the wall with bungee cords to keep astronauts secured and they sleep standing up typically. Pillows and mattresses are not needed as there is no gravity contrary to on Earth where we want soft cushions to relax our heads, bodies, and backs.
However, many astronauts fashion pillows out of bags of clothes, etc. attached to their heads to add a little extra cushion, simulating sleeping on Earth for comfort. NASA has also created pillow-like attachments for astronauts who want them. There is also equipment to help astronauts work or relax such as a laptop, an mp3 player with headphones, a light, and a place for personal belongings. Astronauts wear whatever they prefer for sleeping whether their “pajamas” are longjohns, workout shorts and a t-shirt, or sweatpants and a sweatshirt.
Astronauts do not have to sleep in the sleeping areas if they do not want, though. The ISS is rather large, about 109 m/ 357 feet wide by 73 m/ 240 feet long, so astronauts are welcome to attach their sleeping bags to the walls of the space station.
A big concern for sleeping in space is good air ventilation. Microgravity affects everything, even air. The carbon dioxide that astronauts expel in their breath could form a bubble around astronauts’ heads while sleeping if there is no ventilation. So they sleep near an air vent to keep oxygen easily accessible and prevent hypoxia (when your brain cells die without oxygen).
In addition to “normal” disruptions to sleep, adjusting to the new outside stimuli, the unnatural feeling of floating, aches and pains, ventilation and temperature control, as well as 16 sunrises a day can be difficult, especially for the first few days. Insomnia and sleep deprivation are common concerns for astronauts. Most adjust after a bit, but sleeping pills are the second most common drug astronauts take, after painkillers, to help combat chronic sleep deprivation.
NASA also promotes relaxation techniques and sleep hygiene education to aid astronauts in sleeping more effectively.
Where do astronauts sleep in space?
NASA scientists and flight surgeons have been working on strategies to combat the adverse effects of circadian rhythm disruption on the International Space Station (ISS) crew.
One of the key tools used to combat these disruptions is the creation of strict sleep and wake schedules. NASA personnel follow these schedules in the days leading up to launches or international travel and continue to adhere to them during spaceflight. By aligning with human circadian rhythms and taking individual sleep habits into account, these schedules aim to optimize performance, alertness, and sleep quality.
A crucial aspect of this strategy is educating the crew about factors that affect sleep quality and quantity, promoting what’s known as “sleep hygiene.” This includes the timing of exercise, minimizing exposure to light from digital devices in the evenings, and making dietary choices that contribute to better sleep.
Another tool in NASA’s sleep optimization toolkit is Sleep Cognitive Behavioral Therapy (CBT). This approach helps crew members manage random, unwanted thoughts that can interfere with the transition to sleep.
If you are interested in the scientific research that has been made about sleep quality in space, be sure to check out this whitepaper from Seithikurippu R. Pandi-Perumal and Alain A. Gonfalone: “Sleep in space as a new medical frontier: the challenge of preserving normal sleep in the abnormal environment of space missions” published in 2016. And more recently, “Sleep issues in aviation and space” by Erin E. Flynn-Evans, Amanda Lamp, and Cassie J. Hilditch.
In the below video, former NASA astronaut Mike Massimino explains his experience and what it was like to sleep in space onboard the International Space Station.
Sleeping in space during long-term space exploration missions i.e. to Mars
As we continually expand our human space exploration goals, human life onboard spacecraft continues to be researched. A trip to Mars will likely take 6 months. The physical, mental, and emotional health of the astronauts is of utmost concern during these trips. When launching, we also have to consider necessary resources (i.e. food for the astronauts, and life support systems) and mass and as more thrust will be needed to launch a heavier object.
NASA and other space agencies have been researching hibernation in other animals in contrast with induced therapeutic hibernation in humans to understand how we could hibernate for multi-month journeys and how it would affect our bodies. Current research suggests that this may be the best option for these longer space missions as it would reduce needed nutrients including food and life support system (and therefore mass) while also limiting psychological and social stress.
The moon is only 382,500 km away and with current propulsion systems, such as the SLS, the journey to the moon only takes between 2.5 and four days, making hibernation unnecessary. The trip to and back from the moon will most likely be similar to space shuttle missions. On the moon, sleeping would be between the ISS and Earth as the moon has 1/6th the gravity of Earth.
Sleep is a vital part of a healthy lifestyle and disrupted sleep can result in lower cognitive function, slower response times, reduced immunity, moodiness, and even an increased chance of certain diseases. Sleep is critical for anyone, but astronauts face a special environment, very different than our normal one here on Earth.
Therefore, NASA and other space agencies are constantly researching to ensure the best sleep for their astronauts today and in the future.
Frequently Asked Questions
Yes, astronauts do dream while they are in space, just as they do on Earth. Sleep in space is somewhat different due to the microgravity environment, but the sleep cycles, including REMs (the stages of sleep that involve dreaming) remain the same.
Some astronauts have reported that they were indeed snoring in space however this condition happen less freqntuently in space that it does on earth. Snoring is typically caused by the vibration of tissues in the throat when airflow becomes constricted during sleep.
On a positive note, the absence of gravity could also mean that the tongue and soft tissues of the throat are less likely to sag backwards and obstruct the airway.
Astronauts have said sleeping in space can be challenging indeed because of various factors such as ambient light, the noisy environment that is the ISS, the fact that there are no up or down and the fact that they don’t really get to feel like they “lie”down.
Astronauts usually wake up as a result of an alarm set on their wristwatches or computers. The wake-up time is planned and synchronized with the team on Earth (they use the Coordinated Universal Time (UTC), which is the time standard used in aviation). Sometimes, they may also be awoken by Mission Control, which sends a wake-up call to the ISS.
Sarah Hoffschwelle is a freelance writer who covers a combination of topics including astronomy, general science and STEM, self-development, art, and societal commentary. In the past, Sarah worked in educational nonprofits providing free-choice learning experiences for audiences ages 2-99. As a lifelong space nerd, she loves sharing the universe with others through her words. She currently writes on Medium at https://medium.com/@sarah-marie and authors self-help and children’s books.
The requirements to become an astronaut are extremely rigorous. Does their salary match the difficulty of their profession?