This paper will briefly sort out the evolution history of vacuum pipeline transportation and get a glimpse of past lives, a super high-speed rail.
The origin of vacuum technology is recorded in Torricelli Experimental History 1643: When a sealed long tube is filled with mercury and placed in a mercury tank, it can be found that the pressure difference between atmospheric pressure and vacuum can jack up a 760mm mercury column. The first case of the application of vacuum technology is the experiment of Madeborg Hemisphere in 1654: two hemispheres are combined into a sphere with a diameter of 1 19 cm, and the internal gas is pumped away by a vacuum pump, and then eight horses on each side cannot be separated.
Halbukuen, magdeburg
It can be said that these two famous experiments both use the principle that there is a huge pressure difference between the atmosphere and vacuum [1], which is also a proof that this pressure difference can produce mechanical force. Later generations were also inspired by shipping.
1799, a British mechanical engineer and inventor named George Mayhurst applied for a patent for a fan pump powered by compressed air. The next year, he applied for a patent for the "wind-driven" engine that uses compressed air to drive the car. At the same time, he proposed a service plan for pneumatic vehicles, and suggested setting up a pumping station on the driving route to continuously replenish its power, which can be understood as similar to the relationship between electric vehicles and charging piles.
Atmospheric railway
Atmospheric railway
Based on the previous ideas, Medhurst put forward the idea of vacuum postal route in 18 10, and thought that this method of transporting letters and goods in the pipeline by using the air pressure difference was faster and more efficient than door-to-door transportation by the postman. Furthermore, he began to imagine the possibility of transporting trains by larger pipelines.
18 12, he published the article "Theoretical Calculation of Atmospheric Railway" for the first time, which demonstrated the feasibility, effect and advantages of erecting a pipeline with a diameter of several meters above the railway track to quickly transport goods and passengers through air pressure difference. In addition, he also conceived another form of atmospheric railway, that is, laying a long pipe under the rail. There is a device connected to the train in the pipeline, which moves under the action of pressure difference, thus driving the train to move. The power source of the train is not the front, but the pipeline under the car body.
Shortly before his death, in September of 1827, he published the book "New Inland Transportation System", which highly praised pneumatic propulsion and thought that this method could reach the speed of 96 kilometers per hour even without horses or other animals.
Atmospheric railway uses air pressure to make the car body move along the track, rather than using the front as power.
However, due to one reason or another, the atmospheric railway was not successfully implemented, and the idea was gradually put on hold. It was not until 20 18 that an 89-year-old American engineer, Max Schleger, made it a reality: he set up a track in his vineyard, and there was a PVC pipe with a diameter of 30 cm between the tracks, and a pump was connected outside the pipe to pump out the air in the pipe or inject the air into the pipe.
Max schrieger's atmospheric railway
Under the action of air pressure difference, the "thrust car" in the pipeline will drive the train connected with it to run through magnets. The running results of this model, which is only one-sixth the size of the standard railway system, show that it can easily overcome the steep slope that traditional trains can't overcome, with less running noise, no overhead transmission lines, and the pump can also be driven by renewable energy.
Marx Schliger used the model of atmospheric railway to demonstrate that the train model will be driven by air pressure when blowing inward at one end of the pipeline.
In more than a century after Medhurst's death, the theoretical research of vacuum pipeline transportation has been deepened and improved gradually. Moreover, this mode of transportation also shines brightly in the emerging science fiction literature. The ideas in those works seem to be ahead, but in fact they lag behind the theoretical research of scientists on the time line, and they all have their own theoretical prototypes.
From 65438 to 0888, jules verne's son, Michel Verne, was inspired by the Atmospheric Railway and published an ultra-short story "The Express Train of the Future". In the novel, a steel pipeline laid on the bottom of the Atlantic Ocean is envisaged, with a length of more than 4,800 kilometers, a diameter of about 1.5 meters and a weight of over 1.3 million tons, connecting Europe and North America. The pipeline is wrapped by three layers of iron mesh, and the outer surface is coated with resin to prevent seawater activity.
Driven by the strong airflow, the speed of the train in the pipeline is as high as per hour 1800 km. From Boston, it can reach Liverpool in two hours and forty minutes. The advantages of this system are obvious: the inner surface of the pipeline is finely polished, which can suppress the tension of passengers; According to different seasons, the air flow can adjust and balance the temperature in the pipeline; Aside from the problems of gravity and loss, the construction and operation cost of the system is low, so the fare is incredibly low.
Written by artist A.J. Johnson for Future Express.
However, the atmospheric railway needs to overcome air resistance and wheel-rail friction, and the theoretical upper limit of speed is low. In addition, even if the vehicle can reach a high speed, the aerodynamic noise and vibration will become very large at that time, and the energy consumption will also increase greatly. So with the development of science, theoretical research is gradually developing in the direction of getting rid of friction and air resistance.
1904, Robert H Goddard, the father of modern rocket technology, put forward the idea of vacuum vactrain, which is the first vacuum pipeline transportation system in the modern sense. At that time, he was a freshman at Worcester Institute of Technology. He imagined the train sliding in a vacuum pipe. In order to accelerate and decelerate the train by non-magnetic means and prevent friction, it is necessary to apply fluid pressure between relatively movable parts (such as wheels and tracks). The method is to spray high-pressure and high-temperature liquid with a nozzle, and immediately turn it into high-pressure steam after spraying, thus suspending the car body on the track.
In essence, the train can be regarded as running on a high-pressure liquid film. 1906, Goddard perfected this idea in his short story "High Speed Round Trip". Three years later, Scientific American published a summary of this work with the title "The Limits of Rapid Traffic".
Schematic diagram in Goddard's vacuum train patent
Goddard's vision can be said to be the transition from atmospheric railway to super high-speed rail. Compared with atmospheric railway, the pipeline of vacuum train is in a vacuum state, and the train no longer uses pressure difference to provide power. For the first time, it is considered to reduce the air resistance and prevent the train from rubbing against the track. Compared with super high-speed rail, the form of vactrain is very close to it, but as far as the means of suspending and moving trains are concerned, most super high-speed rail schemes adopt magnetic levitation technology, and vactrain uses high-pressure gas.
1955, Polish science fiction master Stanislaw Lem published Magellan Cloud. This novel is set in the capitalist utopia of the 32nd century. Humans have colonized the entire solar system and are trying to travel between stars. In the novel, Lyme describes an intercontinental vacuum train named "Organowiec", which can travel at a speed of over 1 0,666 kilometers per hour in a transparent vacuum pipeline. This is obviously influenced by vactrain.
Cover of mercenaries
1962, American science fiction writer Mike Reynolds published his short story "mercenary", which even put vacuum pipeline transportation in a crucial position.
In the novel, peace has been achieved. In order to prevent the possibility of world destruction, the government stipulates that only weapons designed before the 20th century can be used in battles, and all battles will be televised to entertain the public. Major companies use mercenaries to solve business disputes. In the transportation industry, Continental Hovercraft Company is in a monopoly position. The newly emerging vacuum pipeline transportation company can greatly reduce transportation costs and bring better services to consumers, thus breaking the monopoly, but first, it will fight the former.
Of course, not only weapons, but also the means of transportation in the novel are ideas that existed before the 20th century. The concept of hovercraft can be traced back to 17 16. The Swedish scientist Emmanuel Sviden Berg mentioned the word "suspension" when studying the surface effect of vehicles. By the beginning of19th century, some people realized that pumping compressed air into the bottom of the ship could reduce the navigation resistance and improve the speed. The concept of vacuum pipeline transportation can be traced back to Medhurst's idea of vacuum postal line in 18 10. Therefore, whether in novels or in real history, vacuum pipeline transportation is indeed newer than hovercraft.
If the previous research was mainly limited to theoretical calculation, in the 1970s, Robert M. Salter, a fan of vacuum pipeline transportation, began to consider practical problems. At that time, he envisioned a vacuum pipeline system "Planetran" located in a solid rock layer hundreds of meters underground. The system runs through major cities in the northeastern United States and has set up nine stations in eight States.
At that time, the Shinkansen in Japan had been in operation for nearly 10 years, and the research on maglev trains was in full swing all over the world, but the technology was not mature after all. Therefore, instead of applying magnetic levitation technology to his own ideas, he proposed to use steel tires. The train is accelerated by electromagnetic force, and the deceleration is realized by squeezing the thin air in front to accelerate the train in the adjacent pipeline. It can be regarded as a fusion version of atmospheric railway and vacuum train.
The most commendable thing about this system is its amazing energy-saving ability. As a "high energy-saving system", when the train slows down, it will return most of the energy to the system for use when the vehicles in the adjacent pipeline accelerate. In addition, the air resistance accounts for more than 70% of the total resistance during the operation of ordinary trains, but the air resistance in the vacuum tube cavity will be greatly reduced, and the energy consumption will naturally be reduced, so that the energy cost consumed by each passenger is less than 1 US dollar, the average speed of the whole journey can reach 4,800 kilometers per hour, and it takes only 2 1 minute to travel from the east coast to the west coast of the United States.
Salter believes that this system will help to reduce the damage to the atmosphere caused by aircraft and ground vehicles, and it has great environmental and economic benefits. Therefore, he called Planetran the "logical next step" in the United States. However, its construction cost is expected to be as high as 1 trillion dollars, so the plan has not been adopted by the government.
With the breakthrough of magnetic levitation technology, the advocates of vacuum pipeline train also realize that this may be one of the key factors for its success. 199 1 year 1 1 month, Gerard K O 'Neill filed a patent application and put forward the idea of "magnetic flight": the train in the pipeline runs on a single track instead of the traditional double track. Permanent magnets are installed on the track, and the train with variable magnets is suspended on the track under the action of electromagnetic force. He calculated that if air is pumped out of the pipe, the speed of the train can reach 4000 kilometers per hour.
2 1 century, the technology of obtaining vacuum has matured, and high-speed maglev trains have been put into use in China, Shanghai and Yamanashi. It seems that everything is ready for the super high-speed rail. In 20 13, feeling that the high-speed railway project in northern California was progressing slowly, Tesla and elon musk, the founder of Space Exploration Technology Company, published a 57-page white paper and put forward the idea of building a 560-kilometer hyperloop between Los Angeles and San Francisco.
In this system, the transport cabin runs in the vacuum pipeline at the speed of 1220 km/h, and the energy of the suspension cabin comes from solar energy or other renewable energy sources. Interestingly, Musk envisioned a pneumatic suspension method similar to that proposed by Goddard. It can be seen that the super high-speed rail is almost completely born out of the theoretical conception of previous scientists.
Since then, many companies and scientific research institutions have successively entered the R&D camp of super high-speed rail, including China Aerospace Science and Technology, State Key Laboratory of Traction Power of Southwest Jiaotong University, Beijing Jiaotong University, Xijing College and other domestic institutions. But they all use magnetic levitation. At the top speed that everyone is most concerned about, there are also institutions that give data of 6,500 kilometers. As for whether it can be realized, it is still unknown.
It is true that the super high-speed rail seems to be very close to the current scientific and technological level of mankind, but in fact there are still many key problems to be studied and solved-
It is precisely because of the above and more problems that have not been mentioned that the super high-speed rail is still in the model test stage, far from reaching the point of manned test. Fortunately, it is completely feasible in theory, and there are more scientists all over the world tackling key problems than before. There is still hope that it will become a reality.
It is worth mentioning that in the process of studying the vacuum pipeline train, scientists have also imagined the possibility of accelerating the aircraft in this way. Because if the traditional rocket increases its load, it must be made bigger and fortified with more chemical propellants. Vacuum pipeline transportation is not only fast, but also energy-saving. If it is used to accelerate the plane, the size of the plane can be smaller or the load can be increased.
200 1 James Powell, one of the inventors of superconducting magnetic levitation (the basic technology of modern magnetic levitation trains) in 1960s and a researcher at Brookhaven National Laboratory in the United States, put forward an ambitious star train (StarTram) plan, namely the magnetic levitation space launch system.
As the name implies, the system needs to put the maglev spacecraft into a curved vacuum tube that extends into the sky. The pipeline length of the first generation system is 130 km, and the outlet height is 3~7 km. The best places are the Andes in Chile or the White Sands Missile Range in southern New Mexico. After the spacecraft accelerates, it can rush out of the pipeline and escape from the earth's atmosphere at the speed of 14300~3 1500 km/h, which is very close to the speed of the second universe.
Star trains run every 1 hour, and each launch can carry more than 70 tons of goods. Judging from the launch cost per kilogram, the system only needs 20~50 dollars. You know, even space exploration technology companies can only say that it has dropped from the original 4600~20000 dollars to 1400 dollars. From the perspective of construction cost, the first generation system needs 20-40 billion US dollars, which is far lower than the US$ 654.38+09.6 billion spent by the space shuttle in the 30-year cycle, and even lower than the US$ 643 billion military expenditure in 2065.438+08.
The research team plans that the first generation of interstellar trains will mainly transport goods such as satellites and will be completed in the 1920s. The pipeline length of the second generation system is 1 1,000 ~11,500 km, and the outlet height is 22 km. It transports 1 million space tourists every year, and each ticket costs only $5,000. It is planned to be completed in the 1930s.
Of course, in addition to the existing problems of super high-speed rail, star trains have also added many engineering problems, such as the erection of pipelines and the suspension control of aircraft in pipelines. However, as soon as the Star Train was put forward, it was verified by Sandia National Laboratory in terms of feasibility. At present, there are also related theoretical studies and model tests. If the interstellar train can be realized, it may bring mankind into a brand-new space age.
[1] Absolute vacuum cannot be obtained by human technical means. The vacuum defined by academic circles is a relative state, which can be called vacuum when it is lower than atmospheric pressure, covering a wide range from atmospheric pressure (about 105Pa) to nothingness absolute vacuum (0Pa).
[2] Measurement of gas rarefaction.
This article was first published in the second issue of Science Fiction World in 2020. The original title is "From Underground to Space-Evolution History of Vacuum Pipeline Transportation".