IEEE Electrification - December 2021 - 56

domestic flights where travel by
rail is an option. Such policies
could accelerate the push for new
hyperloop projects as a promising
alternative to rail. In this article, a
technical path for affordable hyperloop
development and implementation
is presented.
The long-forgotten idea of
vactrains was already patented
decades ago (Goddard 1950). Following
the closure of the Swissmetro
vactrain project in 2009, the key
idea of a low-pressure tube was
rebranded as the hyperloop in an
open source design paper in 2013
(Musk 2013). In its core principle,
passenger or freight capsules are
propelled inside an airless vacuum
tube at nearly the speed of sound.
Hyperloop is still at the early stage
of development, as no fully operational systems exist,
and many engineering challenges are left open. In Figure
1, a conceptual HTS is depicted, including magnetic
lift and drag for suspension, air losses, and forward
thrust. Here, the capsules generate their own propulsion,
driven by linear motors and powered by batteries
on board. As a result of recent marketing hypes about
the technology, not enough explanation of its functionality
has been provided, which is the goal of this article.
Technical Drivers of Hyperloop Development
The key benefits that are promoting the development and
implementation of hyperloop are as follows. By removing
the air from the tube, the advantage is dramatically reducing
the air losses and the associated drag, thus enabling
ultra-efficient transportation means. The feasible cruising
The optimal routes
that are relevant for
implementation are
found in trafficintense
intercity
regions, which would
generate sufficient
throughput to pay
back its
infrastructure
investment.
speeds are rivaling the fastest airplanes,
with an energy consumption
per passenger (PAX) per kilometer [or
revenue passenger-kilometer (RPK)]
that are very close or inferior to those
of trains and comparable to those of
electric cars. For longer routes, the
energy consumption per RPK can be
reduced further. This is because a
larger share of the tube will be utilized
for the cruising speed.
In many ways, hyperloop can be
seen as a symbiosis between the
aviation and rail industries. It is a
subsonic train that experiences highaltitude
atmospheric pressure levels
and must cope with safety certification
standards similar to or stricter
than those of airplanes. The impacts
of hyperloop on humans are a significant
reduction in delay and travel
times, and that transits can happen much closer to the
big city centers. Benefits will be further explained in the
following sections.
Recreating the Outer Atmosphere
The main advantage of the hyperloop concept is the
opportunity to achieve a high-altitude low-pressure environment
at the surface of Earth. In reality, airplanes have
to consume a lot of energy to reach the 10-km altitude,
where the pressure level is 75% lower. Approximately
27 kWh of potential energy is needed to lift every ton of
mass from sea level to 10 km above the ground. In addition,
one would also have to displace a distance where
drag forces must be met as well. These energy needs
come on top of the kinetic energy needed for an airplane
to accelerate to 900 km/h, which constitutes about 9 kWh
Thrust
Motion
Air Loss
Magnetic Drag
Figure 1. A conceptual illustration of the HTS configured with magnetic levitation (maglev) and electric propulsion. A free-body diagram of arrows
indicating the different forces acting on the capsule is depicted.
56
IEEE Electrification Magazine / DECEMBER 2021
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IEEE Electrification - December 2021

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