• A concept for a fifth mode of transport after
planes, trains, cars and boats.
• Cheaper, faster, less environmental footprint.
• Inflection point of about 1500 km after which air
travel becomes faster and cheaper.
Founder of PayPal, SpaceX, Tesla, SolarCity.
"When a distinguished but elderly scientist states that something is
possible, he is almost certainly right. When he states that something is
impossible, he is very probably wrong".
-Clarke’s First Law
• Low pressure tube with capsules that move back and forth
throughout the length of the tube.
• Accelerated via a linear magnetic accelerator.
• Supported on a cushion of air.
• Proposed route from Los Angeles to San Fransisco (approx. 560 km).
• To be covered in just 35 minutes, with capsules leaving end stations
every 2 minutes.
The Concorde Part
• Streamlined shape reduces drag.
• Low pressure in the tube (100 Pa) reduces drag further.
Problem of Choked Air Flow
• Kantrowitz limit gives the top speed for a given tube to pod area
ratio, above which flow will be choked.
• Build up of air in front of capsule and subsequent increase in
• Fan and compressor in the front compresses this air and routes it
to the rear via a bypass tunnel.
• This air expands in the nozzle at the back, also providing additional
The Rail Gun Part
• Magnetic linear accelerators present at various
locations – rotor on the capsule, stator fixed to the
• Route divided into sections with speeds of 300 mph,
555 mph, 760 mph.
• Maximum linear acceleration of 1g achieved while
accelerating from 300 to 760 mph.
• Smaller turning radius implies a lower speed, such
that centripetal acceleration is not more than 0.5g.
The Air Hockey Table Part
• Part of the compressed air is rerouted to air bearings.
• Known as external pressure (EP) bearing and effective
when capsule is stationary or moving at very high
• Each ski is integrated into a mechanical suspension.
• 28 such air bearing skis.
• Additional lift is provided aerodynamically – front edge is
higher than the rear edge (at an angle of 0.05º).
• Viscous interactions generate pressure differential to
Immune to weather
Resistant to earthquakes
Not disruptive to those along the route
• In some parts, total acceleration experienced by the
passenger will be more than 1g, taking the resultant of
linear and centripetal acceleration.
• Commercial aircrafts accelerate at approximately 0.25g,
roller coasters at (4-6)g.
• Uneven shear stress markings were seen on the outside
of the capsule body during simulation.
• Suggestion: Air bearings on top of the pod to improve
stability and help the pod stay balanced.