What is a vactrain?

Vactrains may be the next big thing in the evolution of high-speed transportation. In this episode, Marshall explains how vactrain systems will work, how close they are to becoming reality and the potential they have to impact global transportation.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brain stop from house Stuff Works dot com
where smart Happens. Hi, I'm Marshall Brain with today's question,
what is a VAC train and when will they appear
in reality? In the middle of the eighteen hundreds, the

(00:22):
United States built the Transcontinental Railroad to get people and
products across the country. By today's standards, it was a
slow way to go, about eight days to get from
Omaha to San Francisco. At the time, however, the Transcontinental
Railroad was a technological marvel. The same trip in a
covered wagon took six months if things went well. When

(00:45):
they didn't go well, it often meant death. Compared to
a dangerous six months journey, eight days in a train
seemed like late speed. In the middle of the nineteen hundreds,
trains were replaced by jet airplanes. Now a person could
fly from New York to Los Angeles in six hours
at fifty miles per hour. At the time, this too

(01:07):
seemed like a technological marvel. But here we are fifty
years later and nothing has really changed. The obvious question
is what's next. One possibility is supersonic travel. Supersonic passenger
airplanes currently cannot fly overland in the United states because
of sonic booms, but new technologies could soon give us

(01:28):
supersonic planes that don't have sonic booms, opening up this possibility. However,
supersonic planes aren't really the answer. First, they'll be limited
in their speed to a thousand or fifteen hundred miles
per hour. While that's much faster than today's jets, it's
not revolutionary. The second problem, though, is the cost per passenger.

(01:50):
As the speed of the plane increases, so does the
amount of fuel required to overcome air resistance. When the
supersonic Concord jet was flying, it took six times more
fuel per passenger than a seven forty seven to get
through the air. Thus, the Concorde was too expensive for
most people to afford. The ultimate solution is likely to

(02:11):
be a vac train, also known as evacuated tube transport
or e t T. In a vactrain system, a magnetically
levitated train moves through a vacuum sealed tube. The vacuum
means no air resistance, and the magnetic levitation means no
resistance from wheels or tires. Removing these two sources of

(02:32):
drag creates two huge benefits. First, it means that the
train can go incredibly fast, with a top speed of
five thousand miles per hour second. It means that the
amount of energy required to move the train is very small.
There are new energy costs to maintain the vacuum and
to cool empower the magnets, but these energy costs are

(02:54):
minimal compared to a jet. The bottom line is that
a VAC train between New York and Los Angeles would
allow how people to commute from one city to the
other if they wanted to. The travel time would be
less than an hour, and the price of a ticket
would be very low. The only real constraints on a
VACT train system are first the need to construct the tube,

(03:14):
and second the need to keep the track straight. At
five thousand miles per hour, only the gentlest of turns
are possible, or passengers would feel the g forces. A
right turn, for example, might cover several big states. On land,
a vactrain system could be put underground in tunnels, or
it could go and steal or concrete tubes above the

(03:35):
ground to cross an ocean. The tube might be anchored
with cables on the ocean floor, with the tunnels floating
mid ocean. The idea of a VAC train system that
crosses the United States is exciting, but the global picture
is even more interesting. With a vactrain system circling the planet,
it's easy to imagine travel from the US to China

(03:57):
taking only two hours. New work to London might take
only an hour or so. The system could carry both
passengers and cargo, so shipping times and costs could be
reduced drastically. A VACT train system circling the globe might
sound far fetched today in the same way that transcontinental
jets would have sounded far fetched in nineteen hundred. Keep

(04:18):
in mind that the Right Brothers didn't fly until nineteen
o three. But there is already research underway in China
to bring an early version of a VACT train to market.
This first system would only have a partial vacuum, but
would allow trains to travel up to six hundred miles
per hour. China already has hundreds of miles of high
speed rail traveling at two hundred miles an hour, and

(04:40):
a VACT train would lower travel times significantly. With China
working on the problem, we can expect the United States
in Europe to follow, and VACT train systems could be
a reality in just ten to twenty years. For more
on this and thousands of other topics, is that how
stuff works dot Com and don't forget to check out
the brain stuff block on the house stuff works dot

(05:01):
com home page. You can also follow brain stuff on
Facebook or Twitter at brain stuff H. S w M.