In early April 2021, I joined a research team to confirm the site of a station to place instruments for detecting space phenomena and monitor the state and changes in the space around the earth under the influence of solar activity. Some of these devices are sensitive to the effects of human activities and often need to be placed in sparsely populated and remote areas.
No, one of the alternative sites is the Nagqu region of Tibet. Located in northern Tibet, nagqu is located in the hinterland of the Qinghai-Tibet Plateau, and is the source of major rivers such as the Yangtze River, the Nu River, the Lhasa River, and the Yigong Zangbo River. The eastern part of Nagqu City is a plateau mountainous area with an altitude of between 3800 and 4500 meters, with an average altitude of about 4100 meters. This time, the station was about 4800 meters above sea level, and the expedition team measured it shortly after getting off the train, and it was almost 4400 meters.
When the expedition disembarked from the train in Nagqu, the altitude was more than 4400 meters (source: homemade)
As a native of the Central Plains, the author has developed symptoms such as headaches early. Many people on the expedition team need oxygen, but fortunately the hotel has oxygen release, and the pharmacy can also buy oxygen. An inflatable pillow that can inhale oxygen for 40 minutes sells for 50 yuan, and inflation costs only 5 yuan. So we joke that what is expensive is not oxygen, but the "qualification" to inhale oxygen.
What is "altitude sickness"?
Altitude sickness, also known as altitude sickness, mountain sickness, is strictly speaking, it is a type of altitude sickness. Rapid entry from low altitude areas to plateaus above 3000 meters above sea level, after exposure to low pressure and low oxygen environment, will produce various discomforts, which is altitude sickness, which is a common disease unique to plateau areas.
Common symptoms are headache, insomnia, loss of appetite, tiredness, difficulty breathing, etc.
Headache is the most common symptom, often with a jumping pain in the forehead and temporal region, worsening at night or in the morning when you wake up. Taking the author's experience this time as an example, I feel that my head has been faintly painful when I sleep at night, I can't sleep steadily, and I feel particularly mentally weak when I wake up in the morning.
The air pressure on the plateau is usually 1/2 of the plain, the oxygen content is relatively thin, and the lack of oxygen causes what we often call altitude sickness. For people with weaker bodies, there will be aggravation of underlying diseases, and even the above-mentioned dizziness, headaches, breathing difficulties, palpitations, fatigue, fatigue and so on. Usually mild patients after 3-5 days, a certain degree of oxygen inhalation, symptoms can gradually disappear and alleviate; but if it is a severe case of altitude sickness, there will be obvious altitude pulmonary edema and cerebral edema, which is very dangerous.
Altitude sickness "those things"
Why is it that the higher up the Earth, the less oxygen there is?
Although the air around us cannot be seen or touched, it is actually attracted by the gravity of the earth and has weight. It is only because we are accustomed to the air pressure on the surface of the earth that the human body can achieve a balance of internal and external pressure that we will not feel "squashed".
Since the air is concentrated around the earth by the gravitational pull of the earth, the closer to the ground, the stronger the gravitational force, the more gas is gathered, and the greater the pressure of the gas. When far from the ground, the gravitational force is weaker, the gas is not so dense, and the pressure is small.
In other words, air pressure is the gravitational force on vertical columns of air that extend upwards from where we stand, upwards to the upper boundary of the atmosphere. If the author climbs to the 4800-meter Nagqu station, the air column overhead is from 4800 meters up to thousands of kilometers, missing the bottom 4800 meters, the pressure of the air column on the bottom surface is far less than the pressure of the complete air column at the plain; correspondingly, the compressed air density in the less pressure is also smaller, and the air density at 4800 meters is also smaller than that of the plain.
Therefore, the higher the place, the lower the air pressure and density until it is "vacuum". The air density is lower, and the amount of oxygen in the air is also less. And because the oxygen element is heavier, in fact, the decline of higher altitude oxygen will be faster, and then only hydrogen is left in the air, or even low to no air. However, we humans rely on oxygen in the air.
Low air pressure and low oxygen content in high places (Image: https://www.meipian.cn/2cbosflq)
What are the ways to obtain oxygen for breathing in space?
The higher the air, the thinner it is, so when it comes to "space", is there no air? In October 2021, the Shenzhou 13 manned spacecraft carried the "space travel trio" into space smoothly. According to the mission, the three astronauts will stay in space for 6 months, and they will spend the Spring Festival in space. For such a long time, where does the oxygen they breathe come from?
Cosmic space can be more than 4800 meters low, the space around the earth, the lowest height is about 100,000 meters, there is almost no air here, air pressure is even one millionth of the ground.
Astronauts want to breathe here, it is not as simple as "supplementing oxygen".
The first method, of course, is to bring oxygen tanks directly from the ground. Just as our expedition team purchased oxygen bags and oxygen cylinders in Tibet. This method is the most straightforward, but also inefficient.
Portable oxygen cylinders commonly used when climbing (Image: Rehabmart.com)
The second method is a solid fuel oxygen generator. This method is mainly chemical reaction to produce oxygen, and similar equipment can be purchased in Tibet. Solid raw materials are conducive to storage, and more oxygen can be stored in smaller volumes. For example, a metal jar containing a mixture of powdered sodium chlorate and iron powder, when ignited, iron burns and produces the thermal energy required for a chemical reaction, which produces sodium chloride and oxygen. Commercial aircraft use a similar method to produce oxygen when the air pressure in the cabin drops.
The third method is to electrolyze water. This method is rarely used on the ground, but it is a very important means of providing oxygen on the space station.
On the ground, electrolysis of water consumes more energy and produces hydrogen, but the power supply on the space station is not a problem, huge solar panels can supply free electricity, and the hydrogen produced with it can also be emitted into space. Water as a raw material can be transported from Earth via supply ships to the space station, and water vapor in the cabin air can be recovered through condensers, and even filtered and recovered using astronauts' urine. According to reports, the oxygen generator of the International Space Station is an oxygen production equipment for electrolyzing water.
What the interior of the International Space Station looks like (Image source: Baidu Gallery)
Breathing in space, "only in and out" is not OK
Human beings breathe, consume oxygen, and exhale carbon dioxide. The space station is sealed, and after a long time, isn't the room full of carbon dioxide? Where is carbon dioxide going?
This brings us to the air system in the space station, which not only prepares and supplies oxygen, but also processes the carbon dioxide exhaled by the astronauts.
The carbon dioxide produced in the air that astronauts breathe has been treated by the air system, such as the use of zeolite molecular sieves to remove carbon dioxide from the air. In other words, the air system must not only be able to produce oxygen, but also remove carbon dioxide. There are other gases in the air, such as methane, acetone, methanol and carbon monoxide, which can be removed with the help of activated carbon filters on the space station. Therefore, the respiratory system used by astronauts should actually be called an air circulation and filtration system, not just the preparation of oxygen.
It is with the help of these air systems that astronauts can safely celebrate the New Year in space and successfully complete their missions. Let's look forward to their triumphant return!
The reproduced content represents the views of the author only
Does not represent the position of the Institute of Physics, Chinese Academy of Sciences
Source: China Science Expo
Edit: Lychee jelly