Since the successful launch of Shenzhou XII and the three Chinese astronauts began a three-month space garrison mission, people have paid special attention to the space life of astronauts: how to eat, drink and sleep in the sky?
Even if you eat a meal, the astronaut's operation will be dazzling: eating in a float, eating upside down, eating lying down...
For example, on July 5, a Weibo post published by China News Weekly was on a hot search, with the topic of "variable drinking water after the urine of astronauts is purified."
Sounds a bit heavy on taste... But in fact, the more you know, the more you will sigh: we know nothing about the hard life of astronauts!
Cherish water resources, starting with astronauts
We always call for the conservation of water resources, and on the spaceship, we can most truly appreciate what it means to "if you don't save water, the last drop of water on the spacecraft will be the tears of the astronauts..."
Drinking water in space is a very difficult thing. This "not easy" is divided into two aspects: drinking water and water sources.
What is not easy to drink water?
Under the influence of microgravity in the universe, if you want to drink water, you must have "two shots".
In space, it is difficult to drink water with a normal cup, usually with a straw attached to a sealed bag, squeezing the water into the mouth. And the water does not go down automatically, so be careful not to choke into your nose when you swallow it.
The right way to drink water
Wrong way to drink water
As for the water source problem, imagine that we know that more people with car belts will be more expensive, and the same is true for rocket delivery, the road to the space station is very far, and it is not a "flat road", it is flying upwards, so it is very fuel-intensive.
The fuel used for the rocket is not 7 yuan of more than 7 liters of No. 92 gasoline, and some people have calculated that the freight costs about $10,000 to transport 1 kilogram of something to the space station. So the astronaut drank a glass of water, and the freight sent over was about $3,000.
Everyone drinks 2 kilograms of water per day, plus the water used daily, the cost is too large, so you need to find a way to save - "make water" in the air.
The space station collects water in more than one way, such as condensation in the cabin, collecting the steam exhaled by astronauts and other evaporated water vapors.
Urine and other sewage will be treated by a super-strong filtration technology - reverse osmosis.
Reverse Osmosis Dafa: Turning Waste into Treasure!
We usually drink water and eat is actually not the same, eating is to absorb the chemical energy and then drain, and there is no energy in the water that we can absorb, a large part of it will not undergo chemical changes in our body, but help us metabolize. (Chemical energy: A very hidden energy that cannot be used directly to do work, and is only released when a chemical change occurs, becoming heat energy or other forms of energy.) ）
Therefore, as long as most of the water drunk is treated and purified, it can still be reused after removing metabolic waste
At this time, we have to use the "reverse osmosis method", when it comes to reverse osmosis, we must start from the "semi-permeable membrane".
Semi-permeable membrane is a film that can only allow small molecules and ions to go back and forth, which is simply understood to mean that substances larger than the pore size of the semi-permeable membrane will be blocked out, such as protein molecules.
In fact, semi-permeable membranes can be seen everywhere, such as cell membranes, bladder membranes, parchment, egg shell membranes, radish peels, casings, etc. are all semi-permeable membranes.
It is said that the semi-permeable film is found in the "kitchen".
The French physicist of the year, Noehler, wanted to find a way to make wine:
He sealed a bottle with the pig's bladder membrane and then immersed the bottle in water to see how the wine tasted.
As a result, he found that the bladder membrane had expanded outwards, and water seeped into the wine bottle, breaking the bladder membrane.
We can also do an experiment: the middle of a cup is separated by a semi-permeable membrane, the left and right volumes are equal, the left side is put in water, and the right side is put in the same amount of high-concentration brine or sugar water, ensuring that the height of both sides is the same (the pressure is the same).
After a while you will find that the liquid level of the water on the left will be higher, and this height difference will continue because there is a pressure difference between the clear water and the salt water on the left and right sides, and this pressure difference is called "osmotic pressure".
Due to the high concentration on the right and the relatively few water molecules, the freely diffusing water molecules have passed more and returned less, while the salt and sugar molecules cannot pass through the semi-permeable membrane.
Therefore, when injecting intravenously, 0.9% normal saline should be used as a drug carrier, so that the injection is "isotonic".
If the proportion is not correct, such as the concentration of salt is too low, red blood cells will be like the bladder membrane mentioned earlier, because of inhalation of too much water and burst. The number of red blood cells that rupture is large, and hemolysis occurs, which can be life-threatening. If the salt concentration is too high, it will let the water in the cells flow outside, causing water loss.
This is why seawater cannot be drunk directly:
In the past shipwrecks, some people floated on the surface of the sea waiting for rescue, there was no water to drink for several days, some people were indeed dying of thirst, and some people drank seawater, but died faster.
Because the salt concentration of seawater is high, usually 3.5%, much higher than 0.9% of normal saline (this ratio is the same as the osmotic pressure in our body), so the seawater drunk will not only not be absorbed by cells, but will make the water in the cells in the body penetrate out.
Now we know that water is "sucked away" by high concentrations, automatically expanding freely toward areas of low concentrations, tending to equal concentrations on both sides.
Then, if the pore size of the semi-permeable membrane is appropriate, only the water molecules can pass, and the virus, macromolecules, and hydrated ions cannot pass.
If, in turn, we do not let the water in the low concentration area be sucked away, but instead pressurize the side with the high concentration, squeeze the high concentration part of the water out of the semi-permeable membrane, so that its concentration is higher, this process is called "reverse osmosis".
A simple understanding of the reverse osmosis filtration method is to use a membrane with a very small pore size, put sewage on one side and pressurize it, so that pure water flows to the other side to achieve the purpose of water filtration.
In this way, astronauts filter out impurities in their urine, and then drink...
Although it sounds a little difficult to accept, in fact, our domestic water is also filtered out of sewage, and the water that astronauts drink may be better than the quality of our daily drinking water.
This article is an excerpt from "Today, Are You More Knowledgeable?"
The author Zhang Yuzhi is a "national science scribble hand" praised by CCTV and People's Daily, he is determined to tell science in the way of telling passages, this book is his personal original interesting popular science book, involving physics, chemistry, biology, medicine, psychology, new technology and other disciplines, specializing in those "when you grow up" but do not know the problem. If you want to know how many incredible things there are in the world you live in, don't miss this book!