Hyperloop UC

What is Hyperloop?

Get ready for the Sphinx of public transport! The idea of a car,
the convenience of a train and the speed of a plane! It doesn’t get better than this!

The Hyperloop is a new, futuristic mode of transportation conceptualized by entrepreneur
Elon Musk (CEO SpaceX & Tesla Motors). It is a high speed ground transportation system that
relies on pressurized pods, travelling inside a low-pressure environment.
It is both cheaper and greener. And it is no longer just conceptual. Construction of a
full scale prototype is already in progress.

Based on the "Hyperloop (Alpha)"white-paper , SpaceX is now organizing
the Hyperloop pod competition to design the best pods.

Read more

✕

About Hyperloop

Overcoming the Kantrowitz Limit

Whenever you have a capsule or pod moving at high speed through a tube containing air, there is a minimum tube to
pod area ratio below which you will choke the flow. What this means is that if
the walls of the tube and the capsule are too close together, the capsule will
behave like a syringe and eventually be forced to push the entire column of air
in the system. Not good.
Nature’s top speed law for a given tube to pod area ratio is known as the
Kantrowitz limit. This is highly problematic, as it forces you to either go slowly
or have a super huge diameter tube. Interestingly, there are usually two
solutions to the Kantrowitz limit – one where you go slowly and one where you
go really, really fast.
The latter solution sounds mighty appealing at first, until you realize that going
several thousand miles per hour means that you can’t tolerate even wide turns
without painful g loads. For a journey from San Francisco to LA, you will also
experience a rather intense speed up and slow down. And, when you get right
down to it, going through transonic buffet in a tube is just fundamentally a
dodgy prospect.
Both for trip comfort and safety, it would be best to travel at high subsonic
speeds for a 350 mile journey. For much longer journeys, such as LA to NY, it
would be worth exploring super high speeds and this is probably technically
feasible, but, as mentioned above, I believe the economics would probably
favor a supersonic plane.
The approach that I believe would overcome the Kantrowitz limit is to mount
an electric compressor fan on the nose of the pod that actively transfers high
pressure air from the front to the rear of the vessel. This is like having a pump
in the head of the syringe actively relieving pressure.
It would also simultaneously solve another problem, which is how to create a
low friction suspension system when traveling at over 700 mph. Wheels don’t
work very well at that sort of speed, but a cushion of air does. Air bearings,
which use the same basic principle as an air hockey table, have been
demonstrated to work at speeds of Mach 1.1 with very low friction. In this
case, however, it is the pod that is producing the air cushion, rather than the
tube, as it is important to make the tube as low cost and simple as possible.
That then begs the next question of whether a battery can store enough energy
to power a fan for the length of the journey with room to spare. Based on our
calculations, this is no problem, so long as the energy used to accelerate the
pod is not drawn from the battery pack.
This is where the external linear electric motor comes in, which is simply a
round induction motor (like the one in the Tesla Model S) rolled flat. This
would accelerate the pod to high subsonic velocity and provide a periodic
reboost roughly every 70 miles. The linear electric motor is needed for as little
as ~1% of the tube length, so is not particularly costly.

Making the Economics Work

The pods and linear motors are relatively minor expenses compared to the tube
itself – several hundred million dollars at most, compared with several billion
dollars for the tube. Even several billion is a low number when compared with
several tens of billion proposed for the track of the California rail project.
The key advantages of a tube vs. a railway track are that it can be built above
the ground on pylons and it can be built in prefabricated sections that are
dropped in place and joined with an orbital seam welder. By building it on
pylons, you can almost entirely avoid the need to buy land by following
alongside the mostly very straight California Interstate 5 highway, with only
minor deviations when the highway makes a sharp turn.
Even when the Hyperloop path deviates from the highway, it will cause minimal
disruption to farmland roughly comparable to a tree or telephone pole, which
farmers deal with all the time. A ground based high speed rail system by
comparison needs up to a 100 ft wide swath of dedicated land to build up
foundations for both directions, forcing people to travel for several miles just
to get to the other side of their property. It is also noisy, with nothing to
contain the sound, and needs unsightly protective fencing to prevent animals,
people or vehicles from getting on to the track. Risk of derailment is also not
to be taken lightly, as demonstrated by several recent fatal train accidents.
Earthquakes and Expansion Joints
A ground based high speed rail system is susceptible to Earthquakes and needs
frequent expansion joints to deal with thermal expansion/contraction and
subtle, large scale land movement.
By building a system on pylons, where the tube is not rigidly fixed at any point,
you can dramatically mitigate Earthquake risk and avoid the need for expansion
joints. Tucked away inside each pylon, you could place two adjustable lateral
(XY) dampers and one vertical (Z) damper.
These would absorb the small length changes between pylons due to thermal
changes, as well as long form subtle height changes. As land slowly settles to a
new position over time, the damper neutral position can be adjusted
accordingly. A telescoping tube, similar to the boxy ones used to access
airplanes at airports would be needed at the end stations to address the
cumulative length change of the tube.

Can it Really be Self-Powering?

For the full explanation, please see the technical section, but the short answer
is that by placing solar panels on top of the tube, the Hyperloop can generate
far in excess of the energy needed to operate. This takes into account storing
enough energy in battery packs to operate at night and for periods of extended
cloudy weather. The energy could also be stored in the form of compressed air
that then runs an electric fan in reverse to generate energy, as demonstrated
by LightSail.

Hyperloop UC

We, at HyperloopUC are among 30 teams moving
forward to the finals of the Hyperloop pod competition, from over 1200 initial
applicants. We are pumped up about it and are working day in and day out to
make this dream a reality. If you are interested in staying updated about our
progress, please sign up for our newsletter.

Your help will go a long way in making this endeavor successful.
Please consider supporting the HyperloopUC team, and being a part of the
effort to create the fifth mode of transportation.