Today, the fastest mode of transport is the airplane. Because of high energy consumption and noise of supersonic flight, however, the speed of conventional air transport is limited by the speed of sound in air. Around Mach 1.0, airflow over a vehicle’s surface is a mixture of subsonic and supersonic flow, and the vehicle encounters the power peak called the sound barrier. Beyond the transonic region, it requires high power to drive Mach waves, or shock waves, the cause of sonic booms.

The central concept of a new idea in high-speed transport is that operation of a vehicle in a hydrogen atmosphere would both increase sonic speed and dramatically decrease drag relative to air because of the low density of hydrogen. A hydrogen atmosphere requires that the vehicle operate in a hydrogen-filled tube or pipeline. Tube hydrogen pressure is slightly above outside air pressure, and the tube serves primarily as a phase separator.

The supersonic tube vehicle (STV), a cross between a train and an airplane, runs on a guideway within the tube, is propelled by contra-rotating propfans, and levitates on hydrogen aerostatic gas bearings. Vehicle power is provided by onboard hydrogen-oxygen fuelcells. Hydrogen fuel is breathed from the tube and liquid oxygen is carried onboard. Breathing fuel from the tube solves the problem of hydrogen storage for long-range fuelcell vehicles.

Compared to airplanes, the STV is both very fast and very energy efficient. Its maximum cruise speed is calculated as 3500 km/h – Mach 2.8 with respect to air outside the tube – compared to 910 km/h or Mach 0.85 for the Boeing 747. The Concorde supersonic transport airplane had a cruise speed of Mach 2.2. Energy consumption per passenger of the STV at 3000 km/h is 32% of that of the 747 at 870 km/h.