Bullet trains have circulated on rails for some decades now, starting in Japan on October 1st 1964 in time for the Tokyo Olympics. After that first bullet train, Shinkansen, we have seen hgh speed trains expanding in Europe and more recently in China. The first bullet train, still in operation today, had a commercial speed close to 300km/h and in these decades technology has evolved leading to increased speed up to the world record for rail transport clocking at 574 km/h set in France by a modified TGV.
In parallel, the Maglev technology -magnetic levitation- has shown its technical viability and the resulting possibility to increase the speed to over 400km/h. I took several times the Maglev connection between Shanghai Pudong airport and Shanghai reaching (for just one minute) 431 km/h.
Maglev can achieve these higher speed because there is no resistance from the wheel-rail coupling: the train levitates and does not touch the rail. This magic is achieved through a strong electromagnetic field that serves both as an invisible cushion to suspend the train over the (single big) rail and as a propulsion engine. The train has magnets on its chassis that are repulsed by the magnetic field generated by the magnets on the rail.
The problem with this system is the huge amount of power needed to generate a sufficiently strong magnetic field pushing the train and most crucial the way this power has to be delivered (in subsequent segments). As a reference, the Shanghai Maglev uses 8kW to float over the rail and 8MW to move at 400km/h. Notice that this does not mean that a Maglev consumes a lot more power than a normal high speed train. If you are interested in this comparison and power consumption aspects you may want to look at a nice study from Stanford University. From this study you see that a Maglev requires some 10% more power up to a speed of 280 km per hour, it is equivalent at a speed of 300 km/h and becomes more efficient above that speed.
In terms of operating cost a Maglev train should require fewer maintenance since it has fewer components that are subject to wear (no wheels, no rotating parts…). Overall it is clear the interest to move to this type of transportation, particularly so as new power line technologies, like UHVDC, can lower the cost of electrical power by tapping onto renewable generated far away from the point of usage. The evolution of higher temperature superconducting materials (to power magnets with low dispersion) is also contributing to the interest towards the Maglev. The big hurdle, of course, is the need to create a brand new infrastructure from scratch, since the existing ones based on rails cannot be used.
Just few days ago China has rolled out its first Maglev that is targeted to long distance travel, connecting Beijing and Shanghai in about 2 hours, faster than taking a place. The target commercial speed will be 600km/h (watch the clip).
As part of the post pandemic strategic plan China has put the focus on 7 infrastructures, one is for high speed trains and another one is for UHVDC (Ultra High Voltage Direct Current) and both fit nicely together.
The next 20 years are likely to see the same kind of revolution our great-grand parents saw two centuries ago with the shift from horse and carriages to trains, cars and planes. Over the next two decade cars will be re-invented, electric and autonomous, we will see drones carrying passengers and morphing with cars, and a new kind of trains: Maglev and Hyperloop.