China’s state-backed CRRC tests a porous barrier that vents compressed air, slicing tunnel pressure peaks
China’s railway researchers claim to have slashed the low-frequency shock waves that erupt when a about 370 mph (600 km/h) magnetic-levitation train bursts out of a tunnel.
The breakthrough centers on a 328-foot (100-meter) sound-absorbing “buffer” installed at the tunnel mouth.
Laboratory and field tests indicate the new structure suppresses pressure fluctuations by as much as 96%, promising a quieter, safer ride and fewer complaints from people, wildlife, and infrastructure operators living near future maglev corridors.
When any high-speed train enters a confined space, the air in front of it is squeezed like a piston. That wall of compressed air coalesces at the exit, releasing a thump sometimes likened to miniature thunder, hence the nickname “tunnel boom.”
The problem worsens as speed rises: at 373 mph (600 km/h), a boom can develop in tunnels just 1.2 miles (2 kms) long, compared with 3.7 miles (6 kms) for a 217 mph (350 km/h) conventional bullet train.
According to the Guardian report, Chinese engineers shaped the new buffer from a lightweight, porous material and added a matching porous coating along the first stretch of tunnel wall. The combination lets trapped air bleed away before the train reaches the portal, like the baffles in a firearm silencer.
Early trials suggest the design cuts peak pressure to almost background levels without adding major construction complexity or cost. The solution targets a critical bottleneck for next-generation maglevs.
Conventional high-speed rail tops near 217 mph (350 km/h) because steel wheels and rails suffer rising wear and tear. By levitating a few millimeters above the guideway, magnetic-levitation vehicles avoid that friction and can run much faster, but only if aerodynamic side effects such as tunnel boom can be controlled.
China’s revived maglev push
The new buffer will be fitted to China Railway Rolling Stock Corporation’s latest prototype, introduced in 2021 and designed for sustained service at 373 mph (600 km/h).
China’s only existing maglev, the 2004 Shanghai airport shuttle built with German Transrapid technology, reaches 286 mph (460 km/h) but covers just 19 miles. National planners shelved further maglev expansion for years in favor of a record-breaking 29,825-mile (48,000-kilometer) conventional high-speed network.
Momentum has shifted again. Industry officials say the 373 mph (600 km/h) model’s smooth, wheel-free ride and “quiet hum of electromagnets” could lure travelers off domestic flights, particularly along the heavily traveled Beijing–Shanghai corridor.
A train covering the route in roughly 2.5 hours, about the same as flying gate-to-gate, would undercut airfare by half, reduce door-to-door carbon dioxide emissions sevenfold, and free up crowded airport slots.
The Guardian notes that no route has yet been officially approved, but provincial governments are lobbying Beijing to host a pilot line.
A mixed global picture
China is not alone in chasing maglev’s promise. Japan’s Chuo Shinkansen aims to zip from Tokyo to Osaka at 314 mph (505 km/h), trimming today’s 2.5-hour trip to about 67 minutes, though construction delays have thrown its 2027 debut into doubt. South Korea already operates two shorter maglev services.
The United States, by contrast, just saw its lone federal-backed project derailed. Transportation Secretary Sean Duffy canceled grants for a planned East Coast maglev this week, citing nearly a decade of poor planning, significant community opposition, tremendous cost overruns, and nothing to show.
For now, China’s pressure-relief buffer stands out as a tangible step toward commercially viable super-fast rail. If large-scale trials confirm the 96 percent shock-wave reduction, the fix could remove one of the last major technical hurdles between experimental prototypes and a new era of cross-country travel that is faster than today’s steel-wheel trains yet cleaner than short-haul aviation.
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