How long can an astronaut live in space

  In the Oscar-winning film “Gravity”, astronauts wore spacesuits, struggled and floated in the outer space, finally overcame numerous difficulties and returned to Earth. Can human beings really survive in space only by relying on spacesuits? If so, how long can you live at most?
  How long can human beings live in space without wearing a space suit?
  As we all know, there is no oxygen for living things to breathe in the universe, which is the direct reason why living things cannot survive in space. Once the human body is exposed to the cosmic space, it will instantly lose its external source of oxygen, and can only rely on the oxygen stored in the blood in the body to stay awake. However, the oxygen content in the blood can only ensure that a person is awake for about 15 seconds after the loss of oxygen. After that, the hypoxic blood will be transported to the brain, and the person will gradually lose consciousness. However, this does not mean that the astronauts have been “sentenced to death.” If the astronauts are pulled back to the oxygen-filled space within 1 to 2 minutes after being unconscious, they may be rescued.
  When we fall into the water, our instinct will make us hold our breath to prevent water from entering our lungs, which threatens our lives; what if we do this when exposed to space? It sounds incredible, but it will cause us to die sooner.
  When we breathe in on the earth, air enters the lungs, exerting a constant pressure on the lung wall equivalent to the atmospheric pressure of the earth, and there are very little fluctuations in the process of breathing. The universe is in a vacuum state. There is no atmosphere, and there is no atmospheric pressure. When we are exposed to it, there is no atmospheric pressure to balance the air pressure in the body, and the lungs will gradually expand. At this time, if you hold your breath to prevent the rapidly expanding air from leaving the body, it will cause The lungs swell quickly and rupture quickly. So once exposed to space, the first thing to do is to maintain normal breathing.
  The human body lacks atmospheric pressure, in addition to the expansion of the air in the lungs, body fluids will also boil!
  The fluids in our bodies are collectively referred to as body fluids. Liquids all have a boiling point. When the liquid reaches a certain temperature, the vapor pressure of the liquid will be equal to the pressure of the surrounding air, and this temperature is the boiling point of the liquid. Similarly, body fluids also have a boiling point. In space where there is no external air pressure, the boiling point of body fluids (saliva, tears, sweat, etc.) will be greatly reduced, and then immediately begin to boil and evaporate! But our blood does not boil, because the circulatory system in the blood can maintain blood pressure stability and prevent blood boiling, but the nitrogen molecules dissolved in the blood will vaporize, swell the blood circulation tissues, and make our body swell to twice the original size. Serious damage to some organs and tissues.

  Fortunately, our skin is elastic enough to hold steam, and when the surrounding atmosphere returns to normal atmospheric pressure, our swollen body will also return to normal.
  In addition to the deadly threat caused by the lack of atmosphere, astronauts exposed to space will also be exposed to unshielded cosmic radiation and solar wind. They will be sunburned or even threaten their lives. They will cause damage to human tissues, DNA mutations, and increase cancer and cataracts. The probability of occurrence, leading to infertility. In addition, the fast-flying micrometeoroids and space debris can shoot through the human body like bullets.
  Movies and literary works about space tell us that space is very cold. After the human body loses the protection of the spacesuit, it will be frozen immediately, but this is not the case. There is no doubt about the low temperature in space. However, if the human body is to be frozen, the heat in the body first needs to leave the human body. The only way for the heat to leave the human body is radiation transmission. The radiation conduction and convection need a medium to transfer heat. It is precisely these mediums that are missing in the space of objects. Considering that the speed of heat radiation transfer in space will be very low, the human body will not be frozen immediately after being exposed in the extreme cold space, but will be slowly frozen within 12-20 hours.
  How long can human beings live in space in space suits?
  Astronauts wear two different types of space suits when traveling in space.
  One is a pressure suit, which is worn when the spacecraft lifts off and returns to the earth’s atmosphere. In the event of a decompression emergency and any accident that may occur during lift-off and landing, the space suit can protect the astronauts; in addition, Astronauts also need to carry oxygen tanks or other cushions to protect against space radiation.
  Another type of space suit is an extravehicular space suit. As the name suggests, this space suit is worn by astronauts during extravehicular activities to protect them from all the threats mentioned above. The extravehicular space suit can be divided into two main parts: pressure suit and life support system.
  The pressure suit consists of four parts: upper torso, lower torso, cooling suit and helmet. From the inside out, astronauts must first wear a cooling suit before going on a random space walk. This cooling suit is made of mesh spandex material, covered with 100-meter-long microtubes, and water at 4.4℃~10℃ lasts. Flow through these microtubes to help dissipate heat; the outside of the cooling suit is a hard upper torso, which is composed of multiple layers of lightweight glass fiber, and the innermost layer is a urethane-coated inflatable nylon substrate, which plays a role in regulating body pressure. , The inflatable nylon backing is a polyester suppression layer and a tear-resistant nylon layer; the next 5 layers are polyester film layers, which play the role of maintaining body temperature; and then there are several waterproof and fireproof layers; The outermost layer is a white coating made of 3 different materials to help reflect sunlight.
  The life support system is installed on the trunk part of the space suit, including oxygen tanks, carbon dioxide filters, batteries, pressure regulators, radios and other communication equipment, water tanks, pumps, cooling systems, circulating oxygen fans, etc. All electronic and mechanical components in the life support system are controlled by a display control module installed on the upper torso.
  The space helmet is made of sturdy plastic, similar to a space suit, it helps to provide a pressurized space. Gold-plated goggles and sun visors protect astronauts from direct sunlight, while the helmet’s ventilation system can deliver oxygen to the life support system.
  The combination of pressure suit and life support system can act as a “single-man spacecraft”, allowing astronauts to carry out extraterrestrial surveys or necessary extravehicular maintenance work for the International Space Station. The upper and lower torso parts of the pressure suit can protect astronauts from cosmic radiation and micrometeoroids, provide atmospheric pressure, and help maintain body temperature.
  As the extravehicular activities need to last for several hours, astronauts need to eat food and drink water before performing extravehicular activities. To be cautious, they also need to fill the bag with drinks and attach a fruit stick to the space suit. Astronauts can choose a 0.6-liter or 0.9-liter beverage bag according to their needs. A straw with a valve device is extended from the beverage bag and placed next to the mouth in the helmet. When the astronaut drinks water, the straw valve It will open automatically. The fruit stick is wrapped in edible rice paper and placed in a sleeve near the neck. The upper end extends to the mouth. Whenever the astronaut takes a bite of the fruit stick, the remaining fruit stick will be pulled closer to the mouth.
  The two oxygen tanks in the life support system backpack can support astronauts for 6.5-8 hours of extravehicular activities. The specific time varies from person to person and depends on the individual’s body metabolism rate, because each person’s oxygen consumption and the amount of carbon dioxide produced all different. At the same time, the pressure of the extravehicular spacesuit is equivalent to 1/3 of the earth’s atmospheric pressure, and under this pressure, the air cannot contain enough oxygen. Therefore, for the pure oxygen in the oxygen tank, the carbon dioxide filter system is also essential. It can filter the gas exhaled by the human body and help the unabsorbed oxygen recirculate. An emergency oxygen bag attached to the base of the life support system can provide approximately 30 minutes of additional oxygen supply time.
  Therefore, the longest survival time of an astronaut wearing a spacesuit in the perilous space depends on the amount of oxygen contained in the spacesuit. The current space suit can only provide 6.5 to 8 hours of space exploration time. If the astronaut wants to continue flying, he needs to return to the spacecraft to replace the oxygen tank. To date, the longest spacewalk record was set by astronauts Jim Worth and Susan Helms, who spent 8 hours and 56 minutes repairing the International Space Station.