Why is this a wonderful way to sleep?

Sleep is common in our daily life, but space sleep is unusual.

Sleep in space is unusual because the environmental conditions there are very different from those on the ground. When the spacecraft flies around the earth, it is in weightlessness, which is the main reason why space sleep is different from ground sleep. In addition, there are different circadian rhythms and noise interference, and so on.

Whenever you are absent from bed, you will often hear such a joke: hang you on the wall to sleep tonight. During the space flight, this way of sleeping is no joke. In weightlessness, you can sleep anywhere (floating in the air, leaning against the wall, tied to the bed). However, many people are not used to floating sleep. An American Apollo astronaut once said, "When you find nothing under your body during your sleep, you will feel like you have fallen into an abyss." At the same time, for the sake of safety, it is best to sleep in a sleeping bag and fix the sleeping bag on the bed or wall to avoid floating around when the spacecraft has speed changes and vibration shocks, causing collision accidents. Considering people's sleeping habits on the ground, the United States has set up multi-level beds on the space shuttle. Each bed is 1.8m in length and 0.75m in width. It has a fireproof sleeping bag and is connected with the bed through ropes and hooks. When you sleep, get into your sleeping bag, zip it up, tie your waist with a belt, and you can sleep. However, many people are not used to sleeping in bunk beds. A European astronaut said that when he slept in the lower berth, he felt like sleeping under the bed. Some people like to sleep in the space between two decks. In fact, if you hang your sleeping bag on the wall, you can still have a good sleep. If you put the sleeping bag against the wall, you can straighten your back when you sleep, and you will feel like sleeping in a bed, but the vertical bed takes up 23% more space than the horizontal bed. The European Space Agency has designed a new sleeping bag, which is a double-layer inflatable sleeping bag. After inflation, the sleeping bag tightens, exerting a certain pressure on the human body. This can not only improve the blood circulation in the chest, but also eliminate the feeling of free fall.

We know that in a self-sufficient agricultural society, the universal law of life is "work at sunrise and rest at sunset". In the industrialized modern society, there is a "night god" who sleeps during the day and moves at night. The manned spacecraft flying in low-earth orbit generally orbits the earth in about 90 minutes, which means that a day and night cycle is only 90 minutes, 45 minutes in the day, 45 minutes in the night, and 24 hours 16 alternate day and night. This change in circadian rhythm makes it impossible for astronauts to "work at sunrise and rest at sunset", nor to work at night and sleep during the day. In order to maintain the rhythm of life formed on the earth, astronauts still arrange their work and rest according to the 24-hour cycle during space flight. Generally, they work 8 hours, eat 2 hours, exercise 1.5 ~ 2.5 hours, exercise 3.5 ~ 4.5 hours and sleep 8 hours. In order not to let the fast rhythm of day and night affect sleep, wear an eye mask when sleeping. A more advanced method is to simulate the circadian rhythm of the ground with the change of light brightness to ensure that astronauts can sleep well.

However, the noise generated by various instruments and equipment will still affect the sleep of astronauts. Therefore, when sleeping in space, you should also wear a sound insulation cap. Further measures are to isolate the bedroom from other parts and use sound insulation materials to reduce the noise intensity.

In order to let the astronauts sleep well, the radio contact with them on the ground was also stopped so as not to disturb them. On a multi-person spaceship, it is generally taken by turns to ensure everyone's sleep.

Nevertheless, there are still many accidental factors that affect the sleep of astronauts. For example, in March 1982, when the American space shuttle Columbia was flying, lomas instructed him not to sleep well for most of the time because of static interference in the cockpit. The "crack" of static electricity also affected the sleep of other astronauts, making everyone very tired, and the ground command center had to reschedule their schedules. Some astronauts will not sleep well because of excitement when they first enter space, and some will lose sleep because of overwork and other reasons, which requires the help of drugs.

Space medical experts have done a lot of research on space sleep. As early as the 1970s, the United States conducted a measurement experiment on astronauts' sleep in the "Sky Lab", and learned that space sleep is divided into six stages like the ground, but the deep sleep stage (the third stage) is longer and the number of waking up is reduced. I may wake up 5-6 times in the middle of each sleep, constantly turn over and change my posture, but I rarely dream. According to the characteristics of the space flight environment, scientists have taken many reliable measures to ensure the astronauts' sleep and are constantly improving. However, there are still many problems that need further in-depth study on the extraordinary problem of space sleep.

Experts from the Institute of Space Medicine and Biology of the former Soviet Union have studied many astronauts' space dreams. Their research shows that astronauts' space dreams are completely earth dreams. Klimuk, a former Soviet astronaut who flew into the sky several times, saw his wife and son picking mushrooms in the forest in his space dream, and even smelled boletus and Proteus. Astronauts Jani Bekov and savigny Herch dreamed of their hometown in the suburbs of Moscow, the Star City Astronaut Training Center and their relatives and friends. Another former Soviet astronaut dreamed of heavy rain, which woke him up and made him insomnia.

As for the color of space dreams, many astronauts answered with great certainty that it is completely black and white. Leonov, the first astronaut who walked in space, loved painting. He flew in space twice, and his dreams were not colorful.

Valentina Tereshkova, the world's first female astronaut, flew in space for 7 1 hour from June to 20th, 1963/kloc-0, but never dreamed of space.

Some astronauts have never dreamed of space, but they have encountered space illusions. Lebedev, an astronaut of the former Soviet Union, had just fallen asleep after flying in space for 2 1 1 days, and suddenly his eyes flashed, sometimes like a cross, sometimes like a ball. At this time, if you imagine a person's image, then this person will appear clearly and abnormally in front of you. To this end, he later made an experiment specially. When the flash appeared in front of him again, he recalled familiar places and friends, and everything became very realistic and close. This state can be maintained for 5 ~ 10 minutes.

At present, scientists do not have a clear understanding of the space dream as well as the earth dream, and the research is still going on.

Learning point

The sleeping position of astronauts.

In weightlessness, you can sleep in any position (lying flat, upright, upside down, curled up). However, if you completely relax your sleep, your body will naturally bend slightly into an arch. Most astronauts think that it is much more comfortable to sleep with a slight bend than to sleep completely straight. However, in order to prevent back diseases, it is better to sleep straight.

In a weightless environment, all the weight disappears, the head and body will feel separated, and the arms will float freely. A former Soviet astronaut once put his arms outside his sleeping bag to sleep. When he woke up, he found two hands floating towards him in the dim light, and he was scared into a cold sweat. So you'd better put your arms in your sleeping bag when you sleep. In order to avoid accidentally touching the switch when sleeping in the narrow cockpit of early spacecraft, hands must be tied to the chest when sleeping.