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Comment by LordHumungous | Hacker News Reader

Of course the hyperloop is a joke. Elon Musk has zero experience or training in transportation infrastructure, but we are supposed to have faith in some idea he farted out in a white paper, why? Because he has skillfully cultivated his image as a "genius", and we bought it? The hyperloop was nothing more than a (savvy) PR move to cement his image as a "visionary". That it actually got funded only goes to show what gullible shmucks some venture capitalists are.

Edit: I worked on the LHC for several years. The challenges of maintaining a closed vacuum pipe that spanned a mere 17 miles were vast and expensive. Musk proposes doing it on an exponentially larger scale without addressing the challenges and pitfalls involved. Until he does so, I cannot take him seriously.

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"The challenges of maintaining a closed vacuum pipe that spanned a mere 17 miles were vast and expensive."

The vacuum level required for a particle accelerator (10^-11 torr or something like that) and the one posited for the Hyperloop (0.75 torr) are so far apart that they have virtually nothing in common.

That is actually a valid point, Musk only proposes a partial vacuum which is a lot different from a pure vacuum. However, I think that is still a lot to ask for heavily used transit infrastructure.

It almost sounds like you have no credibility on the matter along with a highly critical opinion of Musk.

Well this is the internet. We're all just assholes with opinions, aren't we?

Assholes on the internet. Now that's an image i won't be forgetting soon.

Reminds me of the following quote:

Assholes ARE like opinions - Everyone has one.

Just the opposite - agreeing with TuringMachine boosted his credibility for me.

Heaven forbid someone updates their beliefs

The LHC has lower pressure than Hyperloop is supposed to have (1E-7 pascal, reading http://www.lhc-closer.es/taking_a_closer_look_at_lhc/0.high_... versus 100 pascal, reading https://en.m.wikipedia.org/wiki/Hyperloop#Theory_and_operati...)

Still quite challenging, but not in the same league, even considering that hyperloop requires way longer tunnels.

The forces aren't much different, even if the allowable leakage is higher and the pumping easier.

Elon Musk had zero experience building cars, yet he made Tesla happen. Perhaps a high intellect and a good general purpose engineering training can accomplish more than you think.

You, on the other hand, are overwhelmed by the challenge of maintaining vacuum in a tube that spans a mere 17 miles. At the very least, you should restrain yourself from using language like "...some idea he farted out...".

I don't think he was alone in this, if he says it was hard, I'd assume it was hard for a whole team of world class physicists and engineers.

Given that the Hyperloop is failing spectacularly, "a high intellect and a good general purpose engineering training" seem empirically to not accomplish quite as much as you think they do -- although, in fairness to high intellect and good general purpose engineering training, there was never any real reason to think that they'd be able to accomplish magic.

1) Elon Musk is not building any Hyperloop, so I don't see how its supposed failure reflects on him.

2) Which Hyperloop is failing? There are at least three groups, and as far as I know, they haven't even got close to testing the system, let alone know if it's a failure or not.

I'm skeptical of the whole concept, but declaring failure at this stage is no less silly than assuming it'll definitively work.

> You, on the other hand, are overwhelmed by the challenge of maintaining vacuum in a tube that spans a mere 17 miles.

You say 'overwhelmed' but I'll just point out it is built and working, and at almost-perfect vacuum.

Yes... it clearly is a manageable issue. The opening comment writer was the one who was overwhelmed, and no surprise given his lack of understanding demonstrated in his answer elsewhere. I just hate it when people with such a lack of knowledge make rude, hateful remarks.

Hmm, that person "worked on the LHC for several years" so they might know a couple of things about long evacuated tubes. Unless I'm not following the thread very well. Shrug.

be careful, tesla is not successful as a car company yet, and its not in good shape to become one either.

one day it might be, and more generally i do hope that we see more progress in the electric car world... but for now tesla only turns a profit as a car company coupled with government incentives. even then, outside of the US (and inside actually) their market share is tiny or zero with very little growth. saying that it doesn't even exist is a very good approximation to reality... if you ignore tech focused news articles and the like at least.

i wouldn't call that a success just yet... as much as we may admire the mission.

>but for now tesla only turns a profit as a car company coupled with government incentives.

Subsidies and protective tariffs are the norm in the auto market.

It would put any car company that didn't get them at a significant disadvantage.

year over year grown >50% seems a lot for a car company.

If I build 2 cars last year and sell 3 this year then I bet you'd be really impressed huh?

In terms of their mission statement which is convince people that electric cars can be 'cool', practical and inexpensive he has succeeded much more than you are giving him and the people at Tesla credit for.

Cool maybe, practical and inexpensive I'm not so sure about.

fair enough, but its a different metric of success. :)

also he started a successful, innovative new rocket company

If I take your first paragraph and replace Hyperloop with Space X, it sounds like something one could have said back when that started. Yet here we are.

I'm no expert either, but that sounds rather hollow..

SpaceX's success is largely due to not having to perform all the hard R&D of rocketry up-front. They got that done for them, for free, by major governments in the 50s and 60s. So now SpaceX can simply build off that, making evolutionary rather than revolutionary changes to the technology and turning it into a profitable business.

But Hyperloop is unexplored territory. There isn't billions/trillions of fundamental R&D already done and given away for free by somebody else. I suspect that's going to have an impact.

Hyperloop can leverage trillion in highly relevant fundamental R&D also. For example aircraft already operate at low enough external pressure to quickly kill the passengers ex: concord was under 1/20th ATM. Yet, loss of cabin pressure is a very rare situation. There is a lot of proven technology to maintain low vacuum cheaply, as a first step to achieving high vacuum. Massively improved battery technology enables reasonably high energy density's which are very much necessary. etc.

Now, sure there is a lot of new tech that would be needed. But, less than you might think.

Would you be able to tell us about some of the problems the LHC faced? Hyperloop aside, this is an interesting subject.

The tolerances on each part must be very tight. If there is a single flaw in one part, the whole vacuum fails. The challenges become exponentially greater as you scale up the diameter of the pipe, since the force on the pipe is proportional to the square of the radius. The LHC had a 50mm diameter pipe, the hyperloop proposes an 8+ foot diameter. You do the math.

The Hyperloop will operate at about 15 psi pressure differential maximum (i.e., one atmosphere).

The Alaska Pipeline is certified to operate at 1,180 psi.

It's not a problem, and minor leaks are not a problem, either. A leak that would stop a particle accelerator dead in its tracks will just make a hyperloop operate at slightly lower efficiency. Plus you can always just run the pump (any practical design will doubtless have the pumps running continously to make up for leakage, just as many ships and buildings have continuously-running bilge and sump pumps).

My personal opinion is not that it can't be done, but that it's financially impractical given then huge maintenance costs compared to conventional high speed rail system.

When you said that you worked on the LHC for several years - what was your role, and how were you involved with the vacuum system? Because your answers show a serious lack of understanding.

First, part tolerances are not a particularly important issue with engineering of high vacuum systems (sealing is effected by compression of gaskets, usually soft stainless steel gaskets for UHV systems).

Secondly, the difficulties in maintaining a large UHV system is usually related to "outgassing", from multiple surfaces and/or material imperfections, and are rarely due to "a single flaw in one part".

Thirdly, you are using the word "exponentially" wrong, even in the context of your flawed claim which is addressed below.

Finally: "the force on the pipe" is not, in a meaningful sense, proportional to the square of the radius. The forces in the pipe wall are proportional directly to the radius (formula is stress=pressure*radius/thickness), if it was otherwise pipe thickness would grow as the square of diameter and large pressurised pipes would be physically impossible.

Happy to do the math for you when you need it, best to leave it to the experts.

Just FYI - hoop stress as you've quoted it assumes a thin walled cylinder. I haven't worked on the LHC so don't know the dimensions; however, this assumption is really only valid for D/t > 20 or so before solutions diverge at which point the interaction becomes more complex than R/t.

Regarding your first point: from my experience (working on physics experiments that depend on vacuum <10^-11 torr), the construction of the knife edge that seals against the gasket is fairly important - any chips or imperfections and the part is garbage. Also do people really use stainless for gaskets? I've always used (and seen other people use) copper, stainless sounds like a huge pain to torque down on.

I doubt UHV experience is relevant here though - at 100 torr you can probably get away with simple o-ring seals. And outgassing doesn't matter: even isopropanol has a vapor pressure of only 40 torr.

Edit: The hyperloop design is at ~1 torr, not 100. Still, I'd imagine outgassing is not a huge issue.

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