Why China’s wild plan to create supersonic trains will probably fail
Forget Hyperloop. Chinese billionaire Li Shufu, who happens to own car company Volvo, has just signed a deal with the Chinese Aerospace Science and Industry Corporation (CASIC) to build supersonic trains, taking Asia’s already uber-fast bullet trains to a whole new level. So what would it be like, to travel in a train moving beyond a sonic boom?
It might indeed be time for a train upgrade – the world’s fastest one, also in China, was built in 2002. It travels at 250 mph from Pudong international airport to the outskirts of Shanghai. China also has an intercity network with over 22,000 km of high-speed – but far from supersonic rail.
The speed of sound is 343 m/s, and Concorde’s jets were the first passenger transport to pass the barrier after its creation in the late 1960s. The Bloodhound car, which recently went into administration, was also created with the aim of reaching supersonic speeds. Will trains be next?
In March, researchers at Southwest Jiaotong University announced plans to test a small, indoor pod, that could potentially travel at speeds of up to 1,000km/h. It’s a small scale test and the engineers hope to hit speeds of to 400km/h by the end of this year.
It’s still a long way from 1,000km/h but if the research project were to hit the speeds it would be faster than jets such as the Boeing 747, and would be a first for any kind of land transport. But that’s still a very long way from real-world use.
What does one need to make a train surpass the speed of sound? Magnetic levitation and vacuum tubes – think Hyperloop – are key, says says Marcel Jufer, a professor at the Swiss Federal Institute of Technology in Lausanne (EPFL). Magnetism because wheels would not be able to reach supersonic speeds because of friction. Linear motors, which have been in use in Chinese high speed-trains, propel the trains forward, and electromagnetic rails use the forces of repulsion to guide the pods in the right direction.
The strange tale of the hovertrain, the British hyperloop of the 1970s
Shufu’s train is likely to “feature a transport system reducing air resistance, with a low vacuum environment and supersonic shape,” says Roger Goodall, a professor at Loughborough University who was involved in the original magnetic levitation projects in the UK, more than 70 years ago. “The proposed acceleration and deceleration levels are high. Humans can easily tolerate the 0.5g (G-force) suggested for Hyperloop, but it probably won’t be acceptable to the travelling public in general.”
Although magnetic levitation was developed in Britain in the 1940s, it has failed to catch on because of the cost. But it’s widely used in Asia because of larger infrastructure and a reduction in cost as a result.
Just like with Hyperloop, many things could go wrong for Shifu’s supersonic train. “If there’s some kind of accident, or sabotage, then the air will go out relatively quickly, and the pressure will drop under one thousandth of the atmospheric pressure, it could be very dangerous,” Jufer says.
Then there is the g-effect. “An airliner take-off acceleration is around 0.3g, and this is only for a small portion of the flight,” says Goodall. However, as passengers will be travelled in a sealed carriage, any potential leaks or gaps could have a detrimental effect on the human body, but we wouldn’t know until the first incident of this happening. Jufer says that if the pressure in the train drops to less than three per cent of atmospheric pressure, all the liquid in the body would be transformed into gas, causing death.
Would we even need a supersonic train, though? Again, just like with Hyperloop, it would be used primarily for travelling between cities that are a long way apart, but it could also offer a competitive advantage to the transport of goods between services, says Jufer. Companies could cut loading and unloading times significantly, increasing their scale of operations. CASIC chairman Gao Hongwei said the planned train could, if it’s ever built, travel from Beijing to Paris in three hours.
For it to take off, cost will be the main issue. Hugh Hunt, a lecturer in engineering at Cambridge, says that once it is demonstrated on a commercial level in one country, it will be everywhere. “It looks as if the cost of a supersonic train system will be the same, or cheaper than conventional long-distance trains,” he says. “As fossil fuels become unsustainable, then there may also be no choice.”
Updated November 10, 2018 11:25GMT: This article has been updated to reflect Concorde’s launch date