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Astronauts have been tackling the challenges of sleeping in space for years — and the lessons learned from their zero gravity slumbers will ensure that one day the first crewed missions to Mars will have enough rest before exploring the red planet.
Orbiting crews spend an average of six months living and working on the International Space Station for nearly 23 years, and they struggle with sleep issues just like people on Earth. Some of the challenges are similar to those of shift workers or people with abnormal schedules, but others are more unique to the space environment.
NASA
NASA astronaut Josh Cassada is bundled up in his crew quarters on the International Space Station on March 2.
For example, most people don’t have to worry about floating away from their beds due to zero gravity. Don’t worry — astronauts use special restraints to keep them from floating by the space station while sleeping.
Two of the biggest challenges for astronauts are their sleep environment and establishing a natural sleep cycle.
Astronauts have dark, quiet and private crew quarters on the space station that are conducive to good sleep — but that’s not always the case on other space missions, Dr. Erin Flynn-Evans, director of the Fatigue Countermeasures Laboratory at NASA’s Ames Research Center in Mountain View, California.
Like their historic Apollo predecessors, the Orion capsules that will be used in the future Artemis mission to the moon are small vehicles with limited space for the crew and sleeping bags for rest.
“I think of it like camping,” Flynn-Evans said. “If it’s for a couple days, probably no big deal. But the longer you’re around someone, the more disruptive it becomes.”
While the space station provides incredible views of Earth, an astronaut’s 16 sunrises a day can wreak havoc with the circadian rhythm, the body’s natural clock for sleep and waking up
On Earth, circadian rhythm disruptions occur for people who work overnight shifts or experience jet lag while traveling across time zones.
“Light is what resets our circadian rhythm and keeps us organized in the day-night cycle, but in space we have some challenges,” said Flynn-Evans.
The space station orbits Earth every 90 minutes, creating alternating cycles of darkness and light. Instead of forcing astronauts to adapt to this strange cycle, NASA experts have added lighting inside the space station that mimics what people experience on a normal day on Earth.
“We have to try to block the light from the windows at night,” he said, “and we really have to try to maximize the light through the windows or with interior lighting to make sure the crew gets the synchronizing stimulus so that they are able to stay awake and sleep at the right time.”
NASA
Former Japan Aerospace Exploration Agency astronaut Soichi Noguchi is inside a sleep station on the space station in April 2021.
Jet lag begins before astronauts arrive at the space station, and their sleep schedules are shifted in the days leading up to takeoff based on the time of day and time zone they’re launching into. Once they reach the space station, each astronaut is transferred to Greenwich Mean Time“a nice middle ground between all the participating countries,” Flynn-Evans said.
At the Fatigue Countermeasures Laboratory, Flynn-Evans and her colleagues developed tools to help astronauts overcome sleep challenges. Some of the techniques include managing when astronauts are exposed to blue light, the key wavelength synchronization for the circadian system, and when to reduce blue light to help them sleep.
Astronauts have regimented schedules, but the arrival of resupply missions or new crews sometimes disrupts those. Flynn-Evans and other researchers have developed strategies to shift sleep safely for astronauts, such as determining when to take a nap or staying up later to accommodate schedule changes.
The same tips that help astronauts sleep also apply on Earth, including following a regular schedule with waking up and going to bed at the same time whenever possible and limiting exposure to blue light before bed, which is emitted by LED TVs, smartphones, computers and tablets.
Although scientists have sleep data from years of spaceflight, the practice of simulation missions on Earth allow for more control.
“We do fake space missions all the time,” Flynn-Evans said. “We have what’s called an analog space environment at the Johnson Space Center called the Human Exploration Research Analog or HERA, and that’s basically a small habitat.”
Bill Stafford/NASA
CHAPEA personnel will live in a residence with individual quarters at NASA’s Johnson Space Center in Houston.
The habitat simulates the size of a lunar base or small spacecraft and can house a crew of four people for long periods of time. Flynn-Evans was involved in a study in which the crew spent 45 days in the shelter and were restricted to five hours of sleep on weeknights and eight hours on weekends. Participants were tested for alertness and performance.
Findings from the experiment showed that if crew members only got five hours of sleep one night, they needed more opportunities to catch up on sleep on subsequent nights to avoid the adverse effects of sleep deprivation. sleep The current requirement is that the crew get 8½ hours of sleep each night on missions to prevent long-term sleep loss, fatigue-induced errors and health complications, according to NASA.
In June, NASA will begin the first experiment with a new 3D-printed Martian habitat at the Johnson Space Center called the Crew Health and Performance Exploration Analog, or CHAPEA.
For a year, a four-person crew will live and work in a 1,700-square-foot (158-square-meter) space to simulate life on Mars. The focus for the first experiment is nutrition, but Flynn-Evans and her fellow researchers will also monitor how well the crew sleeps.
Habitats such as HERA and CHAPEA allow scientists to simulate surprises that might occur on a real mission to the moon or Mars, such as limited resources, failed equipment, communication issues and other stressors of small habitats.
An unexpected source of sleep data proves to be studying the Earth-bound scientists and engineers working on Mars missions such as the Perseverance rover.
A day on Mars lasts about 39 minutes longer than one on Earth, but it’s enough that members of Mars mission control have to adjust their schedules continue to remain on the schedule of Perseverance.
“If you’re moving 39 minutes a day, that means you’re going to sleep 39 minutes later every day,” says Flynn-Evans. “It doesn’t seem that bad for one night. But after five days, it’s like you’ve crossed six time zones. It’s really stressful on the body.”
There is still much that is unknown about being on “Mars time,” such as how the time change affects the metabolism of the human body.
Understanding how humans on Earth are adapting to life on Mars is one way to prepare for future missions to the red planet. Flynn-Evans and his team are working close to those planning the Artemis lunar mission to optimize the astronauts’ schedules and make sure there’s enough light and noise dampening inside Orion when they need to sleep.
The researchers also want to study how much caffeine astronauts need for alertness to ensure the crew doesn’t run out of coffee on a spacecraft with limited storage.
“Sleep is closely related to performance, alertness, interpersonal communication and relationships,” said Flynn-Evans, “so we want to make sure crews are set up for success and get the sleep they need. them.”
