
The Hyperloop: BUSTED - cjdrake
https://www.youtube.com/watch?v=RNFesa01llk
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iMerNibor
Issues I can see here as an outsider:

Comparing a giant vacuum chamber with a tube. The pressure on the tube will be
spread better since the tube itself is so small. No need for huge thick
concrete walls

Expansion: 6000 vacuum seals doesnt sound too bad... Just do regular checks on
them

Pipe failures:

You could have airlocks every so often to seperate pipe segments when not in
use Double (or even tripple) walled tubes, detect failures and shut down
segments and conduct regular tests on segments Use strong enough walls to
resist vandalism damage ("What happens if someone shoots a hole into it?") -
Thick enough steel walls should probably do it, everything else is just a risk
to be accepted (see terrorists on planes or any other thing ever) Not like you
have to run the thing on a full vacuum either, partial atmosphere would help
immensely too and will minimize the issues

"When it fails and you somehow survive the crash you will be stuck inside a
tube with a diminishing air supply"

Again, there could be o2 tanks or filters in place to purify the air in case
of an accident. Its not like it is impossible. It wasnt explicitly mentioned
but he makes it sound like it is impossible to solve and there's nothing one
can do except letting everyone inside the capsule suffocate to death and
having them stuck in the tube for eternity

I can very much agree this is way too early to say ANYTHING and media
shouldn't be hyping it as a ready made product, but please - its not like
there won't be engineers to figure all this stuff out before, there'll be
countless security tests and measures in place before taking it live.

It's not like they're trying to steal money off of people like the solar
roadway guys either (unless I missed something?)

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Fej
Thunderf00t with another brilliant debunk.

These problems could be solved by having the Hyperloop operate at 1 ATM - but
then what advantage does it have? Could the action of pulling the air in front
of the tube to the back create a lower pressure in front and higher at the
back, thus helping to propel the craft?

I vaguely remember reading something like this. Would that make it viable?

~~~
witty_username
Isn't that more like a pneumatic railway?

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weinzierl
All the problems the video talks about[1] boil down to the low pressure
environment in the tube.

The video seems to assume that in the Hyperloop tube there is a "space like"
vacuum while in reality the Hyperloop is planned to have a pressure of 100 Pa
in the tube.

> To speed things further, air would be pumped from hyperloop tubes down to
> 100 pascals, or one-thousandth of the air pressure at sea level, reducing
> wind resistance. The remaining air would be compressed and fed through skis
> that run the length of the undercarriage to levitate the train. [2]

The tube will have to withstand a pressure of about 1000 Pa which is about 100
kg/m*m. Doesn't sound so wild. Obviously the pressure will not be constant
along the tube and it's not clear where the 100 Pa apply. In front of the
capsule, behind the capsule, far from the capsule? Maybe for most of the tube
the pressure will be much higher?

[1] I could only watch it without sound and closed captions. Maybe I missed
something? Also it's funny how Youtube sometimes transcribes Hyperloop as
hyperbole:-)

[2] [http://www.pbs.org/wgbh/nova/next/tech/hyperloop-and-high-
sp...](http://www.pbs.org/wgbh/nova/next/tech/hyperloop-and-high-speed-trains)

~~~
mrob
For all practical purposes 100Pa is space like vacuum. The forces on the
vacuum chamber are still immense, the consequences of failure still
catastrophic, and breathing still impossible. The only difference is that the
turbomolecular pump based engine is not theoretically impossible.

~~~
weinzierl
> For all practical purposes 100Pa is space like vacuum.

Pressure in outer space is more like 1E-11 Pa, at the Kármán line 100km above
sea level we still have only 1 Pa.

> The forces on the vacuum chamber are still immense,

100 kg/m*m isn't immense in my book.

> The only difference is that the turbomolecular pump based engine is not
> theoretically impossible.

No one is talking turbomolecular pump here, these are used below 10mPa. For
100 Pa an ordinary displacement pump will do.

~~~
jessaustin
_100 kg /m m isn't immense in my book._

Yeah, ISTM most floors in commercial buildings that serve crowds could
probably handle that. (Not to say that such floors are airtight, but the basic
engineering of supporting an average American man on every square yard of a
particular surface is quite feasible.) It would be even easier for a self-
reinforcing structure like a tube.

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ohstopitu
I was under the impression that not all parts of the hyperloop would be near 0
ATM. only the parts when the capsule was moving would be ~0 ATM. (so each
section of the hyperloop would be at 0 ATM for an extremely short period of
time per journey)

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sitharus
That what my impression was as well, it's not supposed to be a vacuum tube,
it's a low pressure tube and the vehicles create a lower pressure zone in
front.

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pontifier
Normally I like this guy, but this doesn't seem correct on many counts. I've
seen flexible vacuum gaskets for vibration isolation that would easily allow
for thermal expansion. I'm fairly sure the volume of air rushing into a break
will go down as the pressure locally reaches 1 atmosphere so the "wall of
pressure" wouldn't really act the way he describes because of drag on the
walls. ETC...

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decayy
Does hyperloop require innovation ? Yes it does. If we just stopped innovating
because the problems were tough, we would be stuck in the stone ages.

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jamesrom
The biggest problem this guy has is easily solved by having a valve on each
section of pipe. As soon as a failure is detected, open all valves and let the
pressure equalise evenly across the entire pipe, instead of waiting for a wall
of air to hit you.

~~~
dogma1138
the problem then is that you have 2 shockwave fronts hurdling towards the
train, what you would probably want is some emergency seals that could break
as close to the train as possible to prevent a huge column of air hitting the
train. Basically you would want the pressure wave moving away from the train
into the tunnel rather than the train being caught up in it's way, other
measures could be bulkheads that close off a portion of the track that the
train is in during an emergency repressurization the only problem then is that
you are unlikely to be able to stop the train fast enough for this to work.
Your worse case scenario is a breach somewhere in front of the train because
then you have tons of air hurdling towards the train at potentially supersonic
speed + the train itself at 600mph that can't be pleasant.

~~~
jamesrom
The valves would limit intake to prevent causing a shockwave, and be spaced
close enough to neutralize any shockwaves caused by catastrophic failure.

You could even open the valves intelligently, limit the valves as a function
of the distance of the failure point. So the valves closest to the failure
open the fastest to put air ahead of the shockwave, and the valves further
away open slower to give further away carriages more time to break.

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fncndhdhc
Cringey youtube personality breaks some stuff on camera and claims to know
more than teams of certified engineers.

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blowski
Ad hominem attacks don't say much. I could say 'wacky billionaire claims to
revolutionise rail industry in his spare time' but it says nothing about the
viability of Hyperloop.

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fdsaaf
It'll be amusing to watch this video on my first hyperloop trip. There's a
long history of people saying that innovative things can't be done.

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DaiPlusPlus
He's not saying it can't be done - but that it has serious economic and safety
hazards that have not yet been addressed.

