Low-Risk High-Reward Transition to Low Pressure Tunnel Transit

Typical low-pressure tunnel transit concepts are based on the low-pressure tunnels as separate transit corridors with the disadvantage of the time and cost associated with passengers transferring to and from transit outside the tunnel infrastructure.  A new multimodal ground-effect flight technology (GEFT) identifies a path for seamless connectivity between commuter and intercity rail and highway corridors.  This paper considers and evaluates approaches to open-entry tunnel transit with engineering of tailwinds to increase speed and energy efficiency.  Digital prototypes were evaluated using computational fluid dynamics with results identifying that as velocity is increased in tunnels, pressure can be designed to decrease at a magnitude equal to the change in air’s dynamic pressure.  When considering both tailwind and decreased pressures, the competitive advantage of open-entry lower-pressure tunnel transit extends to distances up to at least 1000 miles.  To a first approximation, closed tunnel transit systems are able to achieve lower pressures and advantages at distances over about 2000 miles; however, when considering the opportunity for continuous improvement in the evolutionary path, the emergence of closed systems having advantages at any distance is not certain.