The Hyperloop: BUSTED

[wraper]

Junctions for thermal expansion compensation are completely possible. They need to hold only 1 bar of pressure, therefore could be made even from soft polymer.

[hayatepilot]

Since some revived this old thread I watched the video in the first post. I find it cringeworthy. Commercial airliners are made of aluminium composite material and they deal with similar pressures safely so why is that suddenly a problem for the hyperloop?

I'm not a mechanical engineer, yet I can think of many show-stopper problems and why this comparison with planes is not meaningful.

The airplane is just an example of a pressure vessel made as light as possible and yet it withstands similar pressure differences like the hyperloop is supposed to do. Actually an oil or gas pipeline is pretty much comparable to the build scale of a hyperloop tube (and oil and gas pipeline use much higher pressures). It is not like they are building something completely new. For once don't ignore the fact a lot of very smart people are working on building hyperloops allover the world and have working prototypes. Now it all comes down to whether it makes sense economically or not (which intrinsically means getting it safe to operate).

The problem with the pressure difference is not with the pod but with the tube!
It is very important whether the pressure differential is positive or negative. If you have a vacuum inside a tube the walls must be very thick to prevent buckling. And if the tube gets kinked enough then the whole tube collapses in on itself.
If the pressure is on the inside then the tube can withstand much higher pressure differentials.

[nctnico]

Still it is not undoable.
My point is that all these 'debunking', 'busted', etc videos about big projects are just scaremongering, FUD and fake news (as it is called nowadays). IMHO a video which goes into the technical challenges and possible solutions is much more interesting. I hate the 'can't do /can't be done' attitude because it stops progress. FFS people have walked on the moon so how hard can it be to run a pod through a vacuum tube? Try it at least!

[ebastler]

The problem with the pressure difference is not with the pod but with the tube!
It is very important whether the pressure differential is positive or negative. If you have a vacuum inside a tube the walls must be very thick to prevent buckling. And if the tube gets kinked enough then the whole tube collapses in on itself.
If the pressure is on the inside then the tube can withstand much higher pressure differentials.

OK, I'll offer submarines as an example then. Correct direction of the pressure differential there. Yes, they are built much sturdier than airplanes, and are rather short for a hyperloop tube... But they also withstand quite a bit more pressure than one atmoshpere.

[jonovid]

this 285 mph - 500km/h  japanese maglev train looks like a lot safer way to travel.
 
as for Hyper loop
until we see a full working prototype that elon musk himself must ride, addressing all safety concerns.
Hyperloop will remain a billionaires toy train set.

[HalFET]

Since some revived this old thread I watched the video in the first post. I find it cringeworthy. Commercial airliners are made of aluminium composite material and they deal with similar pressures safely so why is that suddenly a problem for the hyperloop?

I'm not a mechanical engineer, yet I can think of many show-stopper problems and why this comparison with planes is not meaningful.

The airplane is just an example of a pressure vessel made as light as possible and yet it withstands similar pressure differences like the hyperloop is supposed to do. Actually an oil or gas pipeline is pretty much comparable to the build scale of a hyperloop tube (and oil and gas pipeline use much higher pressures). It is not like they are building something completely new. For once don't ignore the fact a lot of very smart people are working on building hyperloops allover the world and have working prototypes. Now it all comes down to whether it makes sense economically or not (which intrinsically means getting it safe to operate).

The problem with the pressure difference is not with the pod but with the tube!
It is very important whether the pressure differential is positive or negative. If you have a vacuum inside a tube the walls must be very thick to prevent buckling. And if the tube gets kinked enough then the whole tube collapses in on itself.
If the pressure is on the inside then the tube can withstand much higher pressure differentials.

Heh, these assumptions are a bit of a fallacy in some ways. You could design around this to prevent catastrophic failure by taking for example a double walled tube with sections which fail in a controlled manner. (e.g. perforated inner tube with foam and reinforcement rings around it inside the tube that acts as the "pressure vessel") That way the failure would be a lot more gradual and a lot safer. Keep in mind folks, we're engineers and not nay-sayers, which isn't to say this is very ambitious, but to outright shoot it down based on simplistic assumptions seems a bit low. The math on this points at it being a lot more feasible than solar roadways for example... I've seen more questionable things than this succeed before.

[wraper]

The problem with the pressure difference is not with the pod but with the tube!
It is very important whether the pressure differential is positive or negative. If you have a vacuum inside a tube the walls must be very thick to prevent buckling. And if the tube gets kinked enough then the whole tube collapses in on itself.
If the pressure is on the inside then the tube can withstand much higher pressure differentials.

FWIW, usual tunnel tubes must withstand much higher outside pressure than miserable 1 bar in case of hyperloop.
http://www.cowi.com/menu/service/bridgetunnelandmarinestructures/tunnels/documents/021-1700-020e-10b_tunnelengineering.pdf

Great Belt
The Great Belt tunnel is to date the world’s
deepest tunnel in soft soil conditions and under
the sea.
The challenge was to design the tunnel lining
for extraordinary conditions with regard to
outside pressure and chemical aggressivity and
also to design joints to be resistant to the ambient
water pressure (8 bar).

The TBM is required to operate in open or
closed mode in extremely variable geological
and hydrogeological conditions with water
pressures corresponding to 130 metres head of
water. As such, the TBM was designed to be
able to excavate short distances at up to 13 bar
pressure.

[wraper]

this 285 mph - 500km/h  japanese maglev train looks like a lot safer way to travel.\

Expensive as hell, and not nearly as fast.

[technix]

I've been on a MagLev train at 430kmh.

There is a single city with a 430km/h maglev... when did you visit Shanghai?

[orion242]

FWIW, usual tunnel tubes must withstand much higher outside pressure than miserable 1 bar in case of hyperloop.

All underground where expansion is less of an issue since temps remain constant and they are not steel.  Nothing stopping them from taking the hyperpoop underground.  Might take a few generations before we see a cross country underground tube network.

I also don't think TBMs can work in all soil types either.

[EEVblog]

Still it is not undoable.

Solar roads, uBeam and Energous are not "undoable" either.

My point is that all these 'debunking', 'busted', etc videos about big projects are just scaremongering, FUD and fake news (as it is called nowadays).

No, they are calling out obvious impractical bullshit.

so how hard can it be to run a pod through a vacuum tube? Try it at least!

You'll see...

[GeorgeOfTheJungle]

Anybody knows how much was the US deficit and debt in the sixties during the "space race" ? Isn't it now over eighteen million millions (108% of GDP)? Is it ok to increase both (deficit and debt) to spend in this, now? Is this experiment being private or publicly funded? And, do you even have a say on this matter?

[nctnico]

Still it is not undoable.

Solar roads, uBeam and Energous are not "undoable" either.

My point is that all these 'debunking', 'busted', etc videos about big projects are just scaremongering, FUD and fake news (as it is called nowadays).

No, they are calling out obvious impractical bullshit.

Perhaps but without doing some real research into the subject, the project itself and the people behind the project a debunking video quickly becomes unfounded FUD. A first simple check is to see if a project is done by multiple companies (in parallel) or just one and where the funding is coming from.

[nctnico]

Still it is not undoable.

Solar roads, uBeam and Energous are not "undoable" either.

My point is that all these 'debunking', 'busted', etc videos about big projects are just scaremongering, FUD and fake news (as it is called nowadays).

No, they are calling out obvious impractical bullshit.

Perhaps but without doing some real research into the subject, the project itself and the people behind the project a debunking video quickly becomes unfounded FUD. A first simple check is to see if a project is done by multiple companies (in parallel) or just one and where the funding is coming from.

[ogden]

No, they are calling out obvious impractical bullshit.

NASA and France space agency (CNES) both were skeptical about reusable rocket booster. Wording was not "impractical bullshit", but close. Yet SpaceX prove them wrong, in surprisingly short time BTW. All those who "debunked" rocket landing as obviously impractical bullshit, failed as well. So... you never know

With current knowledge and technology we most likely will not travel in vacuum tube, but maybe in 100 years our descendants or at least their postage - will.

[james_s]

I have not looked into the hyperloop in detail but it doesn't immediately jump out at me as bullshit, I see no over-unity claims, no magic required. Given unlimited resources I have little doubt it could be made a reality. Unlike aircraft, capsule weight is of relatively little importance, the thing could be incredibly stout and sturdy

Now whether or not it ever becomes feasible to actually build the thing I don't know but the safety aspect doesn't worry me too much. Somewhere between 100-150 people die every single day in car accidents just in the US, rapid transportation has inherent risks. Yes a hyperloop accident could be spectacular with a lot of deaths but so is an airliner crash and that doesn't stop us from flying. I suspect the barrier is going to be almost purely financial rather than engineering. Building an entire new infrastructure of this sort is incredibly expensive, it pretty much has to blast straight through to be practical.

[mtdoc]

Is it ok to increase both (deficit and debt) to spend in this, now?

Perhaps not, but better this than spend $700 Billion on the military .

I I suspect the barrier is going to be almost purely financial rather than engineering. Building an entire new infrastructure of this sort is incredibly expensive, it pretty much has to blast straight through to be practical.

Exactly! It  is the financial and political realities that will likely prevent long distance hyperloop transport in the USA, not the engineering.  While there are certainly engineering challenges, I’ve read enough back and forth between the “busted!” proponents and real Engineers with experience and expertise in the relevant areas to convincingly debunk the “debunkers” IMHO.

[EEVblog]

A first simple check is to see if a project is done by multiple companies (in parallel) or just one and where the funding is coming from.

Another first simple step is to stop and think why no one has done this old idea before:

Has there been some radical breakthrough in maglev technology? No.
Has there been some radical breakthrough in ridiculously large scale vacuum tunnel technology suitable for human carriage over hundreds of km? No.
Has there been some other radical breakthrough in the transport market space? No.
Has there been some other breakthrough in cost reduction in anything to do with this? No.

Has there been some huge hype from the most influential tech person on the planet? Yes.
Does this hype attract bandwagon chasing money? Yes.

[technix]

I would still prefer the hourly high speed trains that runs at 20% below its maximum test speed. A lot safer and likely a lot cheaper. Yes I am talking about the China Railway High-speed trains "Rejuvenation" that runs between Shanghai and Peking.

[HalFET]

Still it is not undoable.

Solar roads, uBeam and Energous are not "undoable" either.

My point is that all these 'debunking', 'busted', etc videos about big projects are just scaremongering, FUD and fake news (as it is called nowadays).

No, they are calling out obvious impractical bullshit.

so how hard can it be to run a pod through a vacuum tube? Try it at least!

You'll see...

I'm mostly curious about energy efficiency, what'd take less energy:

• Vacuum pumps running 24/7 to keep an inherently leaky system at low air pressures.
• Doubling the speed of high speed maglev-based "rail".

I would expect there's a point where they meet, and I'm not so sure the current speeds are there already. Especially over long distances it would most likely be more energy efficient to run the second option.

[Tepe]

NASA and France space agency (CNES) both were skeptical about reusable rocket booster. Wording was not "impractical bullshit", but close. Yet SpaceX prove them wrong, in surprisingly short time BTW.

That skepticism is not without merit. Think of the Tsiolkovsky rocket equation. You have to lift the fuel you are going to need for the landing, so presumably it basically boils down to saving more on not having to build a new booster versus the price of the extra fuel needed.

[ogden]

Another first simple step is to stop and think why no one has done this old idea before:
Has there been some radical breakthrough in maglev technology? No.

Maglev and linear motor technology itself shall be considered as breakthrough in this context. Then it did not exist - maybe that's why no one has done it.

Has there been some huge hype from the most influential tech person on the planet? Yes.
Does this hype attract bandwagon chasing money? Yes.

Has there been people who tend to use popular hype "buzzwords" to their advantage? Yes.
Does such approach attract more people to their audience? Yes

[ogden]

Think of the Tsiolkovsky rocket equation. You have to lift the fuel you are going to need for the landing

Yes. Think of it. When landing comes, payload and 2nd stage is already lifted and fuel which were used to lift all that is already gone - meaning not that much fuel is needed to decelerate remaining mass for safe reentry speed. After all they are doing it now, so nothing much to discuss here.

[HalFET]

NASA and France space agency (CNES) both were skeptical about reusable rocket booster. Wording was not "impractical bullshit", but close. Yet SpaceX prove them wrong, in surprisingly short time BTW.

That skepticism is not without merit. Think of the Tsiolkovsky rocket equation. You have to lift the fuel you are going to need for the landing, so presumably it basically boils down to saving more on not having to build a new booster versus the price of the extra fuel needed.

Half of what at least ESA does is purely politically motivated. Each country contributes a certain amount of money, and based on that staff hiring and project assignments are done. Project calls are written with said assignments in mind, and it's really just a political game. So take anything a European space agency says with a serious grain of salt, the feasibility analysis is often based in politics and not physics.

[amspire]

According to the CEO, Hyperloop have already "proven" the technology works.



Not much left to do, I guess. 

Or did he mean that they have proven that if you drive an object down a tube, it does go down the tube? How many million did that cost?

I listen to a bit of some of the hype. Lots of talk about building Hyperloop in tunnels and underwater - that is going to make rescue easy. The ideas are all based on some sort of super computerised network that means you capture a driverless vehicle to the station and when you get out, your seat in a hyperloop is waiting - no time wasted. The thing is they will need the same security as airports. Perhaps more since the concept is just so vulnerable.

You fire a tiny charge that pierces the skin of a passenger carriage at the 900 Km mark of a 1000Km pipe and they have to immediately flood the whole tube with air. They then have to rescue the thousands of people in the tube which could mean some have to drive 900Km at a slow speed back to the starting point. The Hyperloop is down probably for the day.

They are now only talking of a 2/3 cost saving over high speed trains, and so by the time it is implemented, the reality could be 3 times the cost of high speed trains. They know what trains cost. The Hyperloop costs are fictional at this stage.