Vactrain

A vactrain (or vacuum tube train) is a proposed design for very-high-speed rail transportation. It is a maglev (magnetic levitation) line using partly evacuated tubes or tunnels. Reduced air resistance could permit vactrains to travel at very high speeds with relatively little power—up to 6,400–8,000 km/h (4,000–5,000 mph). This is 5–6 times the speed of sound in Earth's atmosphere at sea level. Vactrains might use gravity to assist their acceleration. If these trains achieve the predicted speeds, the trip between New Delhi and New York would take less than 2 hours, surpassing aircraft as the world's fastest mode of public transportation.

However, without major advances in tunnelling and other technology, vactrains would be prohibitively expensive.

Several articles published in China around 2010 claim that researchers at Southwest Jiaotong University in China were developing a vactrain to reach speeds of 1,000 km/h (620 mph). However, closer examination shows that the many papers published at SWJTU never use the term vactrain, and instead refer to the ETT work of Oster, Zhang, and Wang.

Russian professor Boris Weinberg () offered a vactrain concept in 1914 in the book Motion without friction (airless electric way). He also built the world's first model of his proposed transport in Tomsk Polytechnic University in 1909.

In 1955 Polish SF writer Stanisław Lem in a novel "The Magellan Nebula" wrote about intercontinental vactrain called "organowiec" (organer?), which was moving in a transparent tube at a speed higher than 1,666 km/h.

Later, vactrain appears in the story "Mercenary" by Mack Reynolds published in April 1962, where he mentions Vacuum Tube Transport in passing.

During the 1970s a leading vactrain advocate, Robert M. Salter of RAND, published a series of elaborate engineering articles.

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