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 sea level and standard conditions. 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.