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Friends who have seen the movie "The Wandering Earth 2" will definitely be shocked by the scene of the space elevator in the play, some people think that this is science fiction, which is simply impossible to achieve in reality.
In fact, we humans have really been researching, so is it possible to achieve this artifact that can allow us to land in space in the future? What is the progress so far?
Space elevator
Space elevator, the name sounds very bullish.
In the future, whoever wants to go to space can ride on it, the speed is comparable to high-speed rail, and it can reach an altitude of 36,000 kilometers above the ground in less than a week.
What is the concept of this height? To know that the tallest building in human beings at present, the Burj Khalifa in Dubai is only 828 meters high, and 36,000 kilometers is equivalent to 40,000 Burj Khalifa stacked together.
Not only that, just one Burj Khalifa has cost $1.5 billion, and then so many together, the cost is simply astronomical, even if the powerful United States, there is no surplus food at home.
In fact, the idea of a space elevator dates back to 1895, when the Russian scientist Tsiolkovsky, known as the father of spaceflight, was inspired by the newly built Eiffel Tower in France.
Since these iron pimples can be made to a height of 324 meters, if you build a little higher, break the sky and build until the geosynchronous orbit.
Wouldn't it be nice to set up an elevator in the tower so that we could travel freely and cheaply to and from space?
Everyone, in 1895, when we were still in the Guangxu period of the Qing Dynasty, even cars were rare things, and then someone proposed to build an elevator to go to space, isn't this a fool's dream?
But Tsiolkovsky doesn't think so, and he thinks that humanity will definitely be able to achieve it in the future. But how exactly is this achieved? Skie did not give a detailed plan.
After years of research, later scientists found that there are two options for really building the space elevator.
Or like the Eiffel Tower, the bottom is made very wide, but no matter how wide it is, it cannot support the pressure from 36,000 kilometers, even if the entire earth is used, it will not help, so this plan is decisively abandoned.
But it's okay, there is another scheme, since it will not work from Earth, is it feasible to hang a rope directly from space, and then install an elevator on this rope that can be lifted?
But the question is, where does this rope fit?
It is important to know that the earth is rotating all the time, and a rotation will undoubtedly produce an inward centrifugal force, and the farther away from the equator, the greater the centrifugal force.
But if the rope is tied at an altitude of 36,000 kilometers above the ground at the equator, the centrifugal force and gravity cancel each other out, and the rope is in an absolutely stationary state, which is also known as geostationary synchronous orbit.
That is, we can first launch a geostationary satellite, and then extend a rope from the satellite to hang to the ground and fix it on the ground to form the orbit of the space elevator.
Space elevator difficulty
However, what material is used for the elevator rope has become the biggest problem.
To withstand the pull of the 36,000 km rope itself, the general material must not work, it must have sufficient strength and toughness, and it also needs materials that are not easy to age.
It was not until 1991 that the problem took a turn. At that time, scientists discovered a very strong material, that is, carbon nanotubes, which gave hope to mankind.
The structure of carbon nanotubes is a molecule with carbon atoms arranged to form like a straw, the diameter is less than a hair, but the strength is 100 times higher than that of the same volume of steel, and the weight is only 1/6 to 1/7 of the latter. And the flexibility is very good, it can be made into fibers.
Theoretically, a nanotube cable 1 meter wide and as thin as paper could support a weight of 13 tons. The material used to make a space elevator is the most suitable, and the strength is sufficient.
But this material is difficult to manufacture, in 1991, although Japanese scientist Iijima Sumio developed carbon nanotubes, it is only a few millimeters long and has a large number of structural defects.
As the saying goes, thousands of sails pass by the side of the sinking boat, and ten thousand wood springs in front of the sick tree. Japan can't do it, but we in China can.
In 2013, the Tsinghua University team produced carbon nanotubes with a perfect structure up to half a meter in an innovative preparation process, yes, you read that right, just half a meter.
But this is already the world's longest carbon nanotube, and it took the laboratory a lot of effort and a lot of money to come up.
The good news is that the team is currently developing carbon nanotubes with a length of more than kilometers. The cable length of the space elevator needs to be at least tens of thousands of kilometers, and the gap is still extremely huge.
In February 2012, the famous Japanese construction company Obayashi-gumi, which is particularly good at building towers, announced that it would invest 10 billion US dollars to build a space elevator, saying that it would be completed around 2050.
However, it is still stuck on carbon nanotube materials, and it is estimated that the project will be delayed with a high probability or may be far away.
But even if the material problem is solved, how to ensure that the elevator box has sufficient power support? And when it is halfway up, the power system fails, and it will not become a high-altitude survival thriller scene.
So where does this motivation come from? One way is to rely on the sun.
This is the famous Dyson sphere idea, which simply means that it collects the sun's energy and consists of a directional transmission panel composed of an artificial celestial body, which can then provide a steady stream of energy for the space elevator.
Another estimate is to rely on controlled nuclear fusion, and the power problem is enough, but either way, it is difficult for now.
Optimistically, perhaps according to the current pace of human scientific and technological development, maybe the imagination of the space elevator in 2050 can be realized.
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If it is so difficult to build a space elevator, why spend so much effort to get it?
Because our dream is the sea of stars, cough, cough, far away, the key is the reduction of the cost of heaven.
According to Bloomberg, the current international commercial satellite launch has a transportation cost of about $25,000 to $40,000 per kilogram of load. If calculated at 60 kilograms per adult, it would cost at least $150,000.
According to the Japanese construction company Obayashi Group, if the space elevator is completed, the transportation cost per kilogram load is about 200 US dollars.
That is to say, the same 60 kilograms of adults only need to spend 12,000 US dollars (that is, 70,000 yuan) to go to space this time, and the cost is more than ten times lower.
Not only can people be transported, but so can the transportation of materials on the space station, which may be an important turning point in the history of human space exploration.
I think that if the world's first space dream, the Ming Dynasty's ten thousand households, is still there, he will burst into tears with excitement when he sees this scene.
Some people may say that I am bragging, but after looking at so many space solutions that come and go, whether it is SpaceX's Falcon rocket or China's Long March rocket, the cost or space elevator is the most cost-effective.
So although the space elevator is still a great idea, I still hope that scientists can overcome various difficulties and turn it into reality as soon as possible.
After all, the earth is the cradle of mankind, but human beings cannot live in the cradle all the time.