The Hyperloop: BUSTED | Hacker News Reader

The Hyperloop: BUSTED

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38 pointscjdrake21 comments

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?)

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?

Isn't that more like a pneumatic railway?

I skimmed the video because this is obviously very childish not really worth half an hour of my time.

That being said, I did not see him perform any kind of rigorous numerical or theoretical analysis of the problem, which would be the first thing an actual engineer would reach for. No finite element simulations, not even empirical napkin math: nothing. He didn't even analyze pi groups involved in the problem to prove similarity between his scale model and an actual functioning hyperloop. The end result is a for-your-entertainment-only youtube prop that has no bearing on the performance and reliability of the actual functioning model.

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...

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.

> 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.

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.

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)

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.

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...

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.

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.

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.

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.

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

Also, you look the other videos on the channel ? There is a few where claim that "feminism" is stupid.

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.

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.

Everything's impossible until it isn't.

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

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