Panorama of the "Red Track" maglev test line. Photo courtesy of Jiangxi University of Science and Technology

On August 9, an air rail train with a red head and white body, the "Red Rail", smoothly drove out of Yongfeng Station in Xingguo County, Jiangxi Province. It is suspended under the blue track, all the way north to the static library. This seemingly "mirror" inverted train line is the world's first rare earth permanent magnet maglev rail transit engineering test line.
So far, all suspended guided transportation systems in the world use rubber wheels for carrying and guiding, while the "red rail" is completely suspended and guided by rare earth permanent magnet materials. This is the biggest difference between the "red rail" and the existing maglev transportation system, which also enriches the pedigree of the guided transportation system worldwide.
The market prospect is huge
Speaking of maglev trains, everyone is not unfamiliar. As early as 2003, my country's first and the world's first commercial high-speed maglev train was running on the Shanghai Pudong Airport Line. Due to the complete overcoming of mechanical frictional resistance, the maglev train runs smoothly at high speed and is known as the ideal super express train in the 21st century. China, Japan, Germany, Britain, South Korea, the United States and other countries have attached great importance to the development of maglev transportation systems in different periods.
Maglev trains rely on the repulsion or attraction mechanism of magnetic poles to overcome gravity and produce a levitation effect. The magnetic levitation train using electro-magnetic magnets to produce the levitation effect will disappear once the power is turned off; the magnetic strength of the magnet changes with the size of the excitation current, and the energy consumption is relatively large. In addition, electromagnetic levitation (such as Shanghai levitation transportation, Japan's superconducting levitation train scheme) is unstable levitation, which requires complex control technology to achieve suspension, which will increase the difficulty of technology and operation and maintenance.
The permanent magnet suspension is to use non-electrically excited permanent magnets (magnets that can maintain their magnetism for a long time) to produce a suspension effect, that is, the permanent magnets repel the tracks (by electromagnetic tracks or magnetically conductive materials) and keep them suspended in the centerline of the slot. Electromagnetic guidance and suspension allow for zero mechanical friction operation. Therefore, finding permanent magnets with stable magnetic properties, high enough density, and strong enough magnetic force to meet the needs of train levitation has always been an alternative solution that the scientific and technological community has been striving for.
The emergence of rare earth permanent magnet maglev trains has solved this problem.
The current research results show that with the help of rare earth element alloy materials, permanent magnets with small size, high magnetic density and sufficient levitation force can be fabricated. This is difficult to do with natural magnetite materials. The permanent magnet used in the "Red Rail" permanent magnet maglev transportation system is NdFeB alloy, which has the characteristics of strong magnetism, stable magnetism and reasonable distribution of magnetic energy, and the natural reserves of rare earth elements neodymium and boron are high, so the cost is low. It is a rare earth permanent magnet alloy material suitable for maglev traffic system.
Jiangxi has unique advantages in manufacturing permanent magnets with rare earth materials. Ganzhou in Jiangxi Province, known as the "Kingdom of Rare Earths", is one of the three major rare earth production bases in my country, with an annual output of 70% of the world's medium and heavy rare earths. The application of rare earth permanent magnet maglev trains has allowed more people to see the future development of the rare earth industry. If it can achieve large-scale development in transportation, it is very meaningful for the application mode and market promotion of my country's rare earth industry.
Rare earth permanent magnet maglev trains are especially suitable for small and medium-sized passenger and cargo transportation. At the same time, it is also a powerful supplement to the trunk transportation network, which can solve the "last mile" transportation and the access problem of the trunk transportation system, and realize the application in airports, scenic spots, parks and other scenarios. Preliminary estimates show that the demand for similar access transportation systems in my country is about 1 million kilometers. The rare earth permanent magnet maglev train has significant energy-saving effect, low noise, and is environmentally friendly. It can also be customized according to actual application needs, and has strong adaptability to transportation needs.
In addition, compared with subway, intercity railway and other suspended systems, its cost advantage is obvious. The cost of rare earth permanent magnet maglev trains is only about 1/2 of light rail, and the construction cost per kilometer is less than 100 million yuan, which is 1/3 of the cost of today's medium and high-speed maglev transportation system. After large-scale application, the cost will be further reduced. Its future application potential and technological industrialization scale should not be underestimated.
There are four major points of view in technology
The "red track" rare earth permanent magnet maglev transportation system developed by Jiangxi University of Science and Technology has four technical highlights.
First, the levitation force required for the maglev train to carry passengers is huge. It is a challenge in the field of materials to manufacture permanent magnets that are small in size, high in magnetic energy density, have sufficient levitation force, and are economical. In the "red track", this technical problem has been well resolved.
The second is the previous suspended traffic system, where trains and tracks are supported and guided by wheels. The "red track" has no wheels, and adopts an original train running system, which overcomes the problems of lack of hard constraints and uncontrollable suspension force of permanent magnets, and realizes the smooth and coordinated control of suspension guidance during the running of the train.
Third, the train adopts lightweight materials, structure and lightweight design, which can maximize the transportation efficiency under the given energy consumption.
Fourth, the trains use a large number of emerging information technologies, such as artificial intelligence, 5G, intelligent control, machine learning, multi-objective intelligent planning, etc., which can provide passengers with rich in-transit information services while realizing unmanned driving.
For the public, the biggest concern is the safety of rare earth permanent magnet maglev trains. In fact, this has been fully considered in the early design.
For example, a closed box beam is used to wrap the running system, the car is suspended under the running system, and the train will never derail. Once the train fails, passengers can escape from the train as soon as possible through elastic pipes similar to the rescue of high-rise buildings. Intelligent control and operation scheduling are realized through communication between vehicles, which fundamentally avoids the occurrence of rear-end collisions. If a fire breaks out in one car, it will not affect the whole car, because the car body is made of flame retardant material, which has a strong fireproof function.
As a brand-new medium- and low-volume-oriented transportation system, "Red Rail" has passed technical verification and engineering verification, and already has the conditions for large-scale promotion and industrialization. Next, it is necessary to step up the construction and operation of the demonstration line, and at the same time, further strengthen the construction of the standard system, and fully tap the potential of the "red track" which can be customized according to needs, has a wide range of applications, strong adaptability to needs, and good technical and economic benefits through large-scale applications. It has become a model of an efficient, green, economical and intelligent new transportation system "originated from China and universal to the world".
(Original title "Where is the Mystery of the First Rare Earth Maglev Train "Hanging and Speeding", author Jia Limin, chief professor of the State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, interviewed by China Science News reporter Wen Caifei)