Vactrain A vactrain (or vacuum tube train ) is a proposed, as-yet-unbuilt design for future high-speed railroad transportation. It is a maglev line run through evacuated (air-less) or partly evacuated tubes or tunnels. The lack of air resistance could permit vactrains to use little power and to move at extremely high speeds, up to 4000–5000 mph (6400–8000 km/h, 2 km/s), or 5–6 times the speed of sound ( Mach 1) at standard conditions. [ 1 ] Though the technology is currently being investigated for development of regional networks, advocates have suggested establishing vactrains for transcontinental routes to form a global network. Vactrain tunnels could permit very rapid intercontinental travel. Vactrains could use gravity to assist their acceleration. If such trains went as fast as predicted, the trip between Beijing and New York would take less than 2 hours, surpassing aircraft as the world's fastest mode of public transportation. Travel through evacuated tubes allows supersonic speed without the penalty of sonic boom found with supersonic aircraft. The trains could operate faster than Mach 1 without noise. However, without major advances in tunnelling and other technology, vactrains would be prohibitively expensive. Alternatives such as elevated concrete tubes with partial vacuums have been proposed to reduce costs. Researchers at Southwest Jiaotong University in China are developing (as of 2010) a vactrain to reach speeds of 1,000 km/h (620 mph). They say the technology can be put into operation in 10 years. [ 2 ] [ 3 ] [ 4 ] Contents The modern