Space elevator, from science fiction to reality

In the past two days, China's Shenzhou 12 manned spacecraft was launched and successfully docked with the Tianhe core cabin. Three astronauts successfully entered the space station independently developed by China, achieving another milestone in China's space development. Take this opportunity to talk about another space creation relative to the space station-the space elevator.

Space elevator is a very high elevator connecting the ground and the universe, which is often seen in science fiction films or novels. This idea was first put forward by the famous Russian space scientist Konstantin, who is called the father of human space navigation. Tsiolkovsky. When he visited the Eiffel Tower in France 126 years ago, that is 1895, he came up with the idea of a cosmic elevator. Constantine is definitely a man of god. This man has never been to school, all his knowledge is taught by himself, and he has lived in a cabin in the suburbs of Russia for most of his life. Results The first cosmic velocity was calculated in this cabin, and the initial rocket model was designed.

Constantine was particularly interested in the universe and advocated space colonization. He has a famous saying: "The earth is the cradle of human beings, but human beings can't live in the cradle all the time." Constantine firmly believes that man will eventually become a god-like existence, able to control heaven, earth, time and even everything. He firmly believes that this is the inevitable result.

When Constantine put forward the idea of a cosmic elevator, the rocket had not yet come out, so he stayed at this stage of thinking. Until 1960, 65 years later, a Russian engineer-Yuri? A Qiu Tanov, on the other hand, concretized Constantine's theory of cosmic elevator and put forward possible concrete plans. According to common sense, the elevator we usually build feels like it should be built from the earth, but Yuri? A Qiu Tanov said it should be built from space. At a distance of 36,000 kilometers from the ground, there is a circular orbit-the geostationary orbit. The satellite running in this orbit is stationary relative to the earth's surface, which means that the satellite and the earth rotate at the same speed. After the satellite is launched into the geostationary orbit, a rope is extended from the satellite, and a heavy object is hung on the rope and hoisted to the earth. Theoretically, as long as the rope is long enough, it will definitely fall to the ground. After hanging to the ground, fix this end on the ground, so that the earth and the satellite are connected by ropes.

However, there is a problem. When the weight hangs down, the center of gravity of the satellite and the whole weight will move down, thus leaving the geostationary orbit. In order to keep the satellite in the geostationary orbit all the time, it is necessary to extend a rope from the satellite in the opposite direction to the earth. The length of the rope is the same as that of the rope hanging on the ground, which is also 36,000 kilometers. But the length of this 72,000-kilometer rope is far from enough, because this rope is vertically balanced on the ground, and it will fall when you pull it. So in order not to let it fall, the rope extending from the satellite to the universe should be extended by 28,000 kilometers, that is to say, the rope from the earth to the satellite is 36,000 kilometers long, and the rope extending from the satellite to the universe is 64,000 kilometers long, with a total length of * * * 100000 kilometers.

Put this rope away and climb it with the elevator, and the construction of the cosmic elevator is completed. After the space elevator is completed, it can theoretically carry 100 tons of goods. This kind of space elevator is relatively simple in theory, so many countries have begun to try it. As a result, 30 years later, no country has made any progress. Until 199 1, one country made a breakthrough, and that was Japan.

Why are there no breakthroughs in other countries except Japan? This brings the core problem of building a space elevator-the material of the rope. Ordinary steel can't do it. The density of steel is too high, which leads to its own weight. When it grows to a certain extent, it will break by itself due to its own weight. Just like people, if they grow too tall, their legs will be too much. But trees can. The length of trees is 100 meters. So in theory, we need to find a metal that is lighter than wood but heavier than steel. From 1960 to 1990, we have been looking for such a material for thirty years, but all in vain. Until 199 1, a physicist named iijima masao at NEC laboratory in Tsukuba, Japan, discovered carbon nanotube in carbon fiber. This kind of nano carbon fiber tube is naturally generated, but it does not conform to the laws of nature, so it is called "supernatural matter", which means that nature should not exist, but it just appears. There are many associations, which may be left here by aliens or the remains of previous high civilization.

The characteristics of this material-ultra-light, ultra-hard, elastic, can be made of carbon fiber into carbon filaments with fine hair, one can lift a car, and the strength of several bundles can reach more than twice the strength required for space elevators. However, this material can't be mass-produced at present, and it belongs to molecular structure. Theoretically, it is necessary to connect one molecule with another. With current technology, the length of100000 kilometers is far away. Japan seems to feel that this matter is becoming more and more promising now, and they may have made a very big breakthrough in this technology. In particular, the famous Japanese construction company Dalin Group has announced on its homepage that it will realize the construction of space elevators in 2050. Dalin Group is a construction company with a history of 130 years. It is especially good at building tall towers, such as Sky Tower and Roppongi New Town.

On the other hand, why is it so difficult to build a space elevator? How much benefit will it have after doing it? In fact, the only purpose of realizing the space elevator is to look forward to the rocket. Now the only way for people or things on earth to leave the earth is to carry rockets. But the rocket has many problems. The first is that the launch cost is too high. Today's rockets are much cheaper than before, but a launch costs hundreds of millions of dollars. Why is it so expensive? Because rockets are disposable, they can't be used after use. Of course, now the rockets launched by Musk's Space Exploration Technology Company can be recycled. Although the cost has dropped a lot, it will cost hundreds of millions. So 1 100 million dollars is expensive? The $300 million Boeing 787 is more expensive than the rocket. But airplanes can be used tens of thousands of times, and rockets can only be used once.

The second problem with rockets is that they are unsafe. Even now, the failure rate of rocket launch is still quite high. Although the success rate of China rocket launch has been high in recent years, there will still be several failures before. So if rockets are used to carry people, no one wants to take the risk. The Shenzhou-12 manned spacecraft launched by China in the past two days is equipped with a long March 2F remote-controlled launch vehicle with mature technology, but even if it is mature, I will be inexplicably nervous when watching the live broadcast.

The third problem is that rockets are not environmentally friendly. It has been said before that rockets are disposable. After being lifted into the sky, they are thrown into space, forming space junk. These wastes revolve around the earth at high speed, and there is no guarantee that when they will hit satellites or other spacecraft, these wastes will also collide with each other. So now space junk has become a big topic.

The other is that rockets are too inefficient. Rockets need to consume 2000 tons of fuel to send 30 tons of materials to the universe, which is the least efficient means of transportation. To sum up, the rocket is such an unreasonable means of transportation, with high cost, insecurity, environmental damage and low efficiency. So people want to find a solution that can replace rockets, and the space elevator is a very good choice.

The first advantage of the space elevator is its special safety. People will go up and down along the rope without great danger, so there will be a higher chance of sending people into the universe. The second is low cost. Space elevators do not consume chemical fuel, but are driven by electricity. But electricity is transmitted from the earth to the elevator, and it can't be transmitted by wire, only wirelessly. This wireless transmission is also a topic that Dalin Group said to solve. They want to realize the long-distance transmission of100000 kilometers before building the space elevator. The technical difficulty of this long-distance transmission is not low, not to mention100000 km. If the long-distance transmission of 20,000 kilometers can be realized, wireless transmission can be carried out anywhere in the world. On the other hand, if you send electricity to the elevator remotely, it will climb this rope by itself. At first, electricity was used. With the passage of time, when the speed is faster and faster, its kinetic energy is continuously transformed into potential energy. When it exceeds the stationary orbit (36,000 kilometers), it can be thrown out by centrifugal force, so there is almost no electricity in the second half. When I come back, I need electricity for the first half. When you run, it becomes a free fall. Finally, slow down. So the power consumption is not as much as expected.

So how fast can this elevator go? At present, the speed of Dalin Group is expected to reach 200 kilometers per hour, but even at a speed of 200 kilometers per hour, it will take 500 hours, or 20 days, to run from the ground to the finish line of 654.38 million kilometers. According to the calculation of Dalin Group, after the completion of the space elevator, the cost of space travel can be reduced to several hundred dollars, which means it can be cheaper than our general travel. So no matter how you look at it, the space elevator should be the direction of efforts.

Having said that, how much does it cost to build a space elevator? According to the calculation of Japan Space Elevator Association, it is estimated that building a space elevator will cost 654.38+000 billion US dollars, which does not seem particularly expensive. Once built, it will return to its original cost in a few years. Bill Gates can build ten sets at this price, and it costs ten times to build a full track of a maglev train in Japan, so this price is cost-effective.

The person in charge of Dalin Group said in an interview that they will start building this project in 2030. So before 2030, three problems should be solved: (1) manufacturing 654.38+10,000 kilometers of carbon fiber pipes; (2) Testing the strength of 6,543,800 km long carbon fiber pipe; (3) Long-distance wireless transmission of 654.38+ 10,000 kilometers is realized. If wireless power transmission can really be realized before 2030, then our life will be much simpler and more convenient. There are no wires at home, mobile phones don't need to be recharged, and new energy vehicles don't have to worry about battery life.

Why did Dalin Group do such a thing so actively? The reason is that they think the space elevator is very commercial. If it really costs hundreds of dollars, they can travel to the universe. I think most people in the world want to go once. And if any city has such a building, it will definitely become a landmark building of this city and a landscape.

Another great significance of the space elevator is that it is a very important infrastructure as a space immigrant. In the future, it is impossible for human beings to develop the universe by rockets, emigrate to Mars, build cosmic cities, robotech and so on. Because they need to transport a lot of building materials, which can only be realized by the space elevator. In addition, if the space elevator can be realized on the earth, it will be easily transplanted to Mars and the moon, and it will be easier to build it on this low-gravity planet because the requirements for materials will be much lower. If there are space elevators on these planets, we will reach them more easily. At least we don't have to think about landing. We can fly directly to one end of the elevator and dock with it. It is very convenient for people to take the elevator to the surface of the planet.

Another thing worth looking forward to is the convenience of bringing the matter in the universe back to the earth. Now it is necessary to use spacecraft to bring the substances in the universe back to Earth, such as the Apollo spacecraft in the United States and the Chang 'e-5 probe in China, but the carrying capacity is very small. But if there is a space elevator, you can take it back in pieces. In fact, there are a lot of resources in the space around the earth, all on meteorites. There used to be a lot of resources on our earth, but due to gravity, these things gradually sank into the core. At present, there are light things on the surface, and there are few heavy metals. But meteorites are different. What's on them is what, and it won't sink. At present, some asteroids that pass through our earth are all platinum and diamonds. As long as one is intercepted in the universe and transported down from the elevator, it will be developed.

But who will return the things in the universe to the earth? In 20 15, the United States passed a bill-the commercial space development competition law, which stipulated that the resources developed by individuals or legal persons in the universe should be owned by individuals or legal persons. This law is based on the lotus principle in international law. Lotus principle-1926, a French ship bound for Turkey collided with a Turkish ship in a port near Turkey, knocked the latter over and boarded the no one lives. After the French ship landed, the Turkish police boarded the ship and arrested the French. So the international court of justice encountered a difficult problem, whether these French crew members can accept local trials and whether Turkish law is applicable. Finally, the international court of justice gave the arbitration result, which can be applied. This was later called the Lotus Rule, because French ships were called Lotus. In fact, the lotus principle is just one sentence. If there is nothing prohibited by international law, every country can exercise its jurisdiction according to the scope that it can control. The world treaty stipulates that celestial bodies cannot be occupied, and no country can claim to own a planet. But the resources on the planet do not belong to celestial bodies, so the resources can be owned by individuals or legal persons.

So the space elevator is such a very dreamy thing.