There's nothing physically impossible about the Hyperloop (basically a maglev in vacuum tube, nothing wrong with the tech, just not particularly economical). Maglevs have been deployed successfully in some parts of Asia, they are just dreadfully expensive and nimbys have fears about radiation but they are hardly new technology.

Note that the main point about the hyperloop was the vacuum tube, not the maglev part. And the vacuum tube doesn't actually work. It's not actually feasible to create a vacuum tube hundreds of km long. It's just about physically possible, but it's not really technologically feasible - not for a system that is supposed to be in constant operation all year long.

It's also important to remember that vacuum tube trains are an 1800s idea, which everyone started pretending is some revolutionary new transportation concept.

And besides that you don't have to have a really good vacuum, you just have to have a 'good enough' vacuum that you can attain high speed without losing the stabilizing effect of a bunch of air constrained by the walls of a tube. Bonus points of you can get the air to move at a speed a bit slower than your vehicle, more bonus points if you can use the air to propel your vehicle.

But: it's probably still a dumb idea, but one that is borderline.

I'm still waiting on the giant pneumatic tubes from Futurama.

The problem is that if any of that was a good idea, the question is why is the Hyperloop specifically a good idea, but regular old high speed rail is not? What factor are you changing that makes one good, and the other not good enough to get done right now?

(the answer of course is nothing: the Hyperloop would be stupidly expensive, and however fast it is wouldn't solve the logistics problem of loading and unloading it - so whatever quote you've seen for rail, just triple it if you tried to build a hyperloop).

Yes, there isn't anything in particular about Hyperloop that makes it stand out, but it is different in high speed rail in that it is underground and so more complex in almost all ways but one: right of way (and possibly aesthetics, which depending on the landscape can matter a lot).

Not a lawyer and might be wrong but as far as I know land rights go all the way to the core in the US, so going underground wouldn't help with right of way. I know, "HN is more than the US," but we seem to have the most trouble with trains.

I think you're referring to the 'all the way to heaven and all the way to hell' bit.

In principle that's true. But in practice mining rights and such have been split off from the right to the land and some reasonable depth underground. And any objection to an easement would be much harder to establish if it doesn't actually affect you. But for those parties that own the underground and mining rights for a given location there could well be a viable opposition to such a development. But that would then risk an eminent domain claim.

It's all pretty complex. But I would still assume that going underground is easier than going above ground where the parcels are small and the interests are immediate due to interference with existing activity.

Even if this is true, the costs of digging are much higher than the costs of above-ground construction + the legal costs of acquiring the land. A hundred kilometer tunnel would be one of the longest tunnels ever built, and the longest train/track tunnel by quite some margin. And it would need copious safety features and auxiliary tunnels leading to the surface, even before the whole vacuum part gets added in. So it won't even completely avoid the need for buying above ground lands.

> the costs of digging are much higher than the costs of above-ground construction

Yes, easily 3 to 10x.

> A hundred kilometer tunnel would be one of the longest tunnels ever built, and the longest train/track tunnel by quite some margin. And it would need copious safety features and auxiliary tunnels leading to the surface, even before the whole vacuum part gets added in. So it won't even completely avoid the need for buying above ground lands.

Indeed, so it's both a technical and economical non-starter. But it's not a 'dumb idea' in the sense that it is impossible. Merely impractical, too expensive and too complex and besides cheaper solutions exist (aircraft, for one, which scale much better with increasing distance than rail ever will).

One thing all of these 'dumb ideas' and the hyperloop, tidal energy and so on all have in common: they are great ways to get your grubby fingers on subsidies.

I understand your point much better now, yes. These are all different from things like cold fusion.

We used to discuss this back in university days! NA is extremely allergic to copy something that’s been done extremely well in the east (e.g., high speed rails) and instead tries to come up with some “cool better way” of doing things. After all, we are different, and copying something would be an extreme ego hit. This thought process applies to Hyperloop as well. I live in Canada, and it is really disappointing how we don’t have reliable rails between metro areas of large cities. Or even cross-border ones like Vancouver-Seattle corridor. Even sadder knowing it will never happen.

Canada has a massive infra problem. That is not strange when you consider that it has an enormous area to deal with a relatively low population and that most of that population lives along a relatively narrow strip of land, and long strips are very much sub-optimal compared to a circle (which is the ideal for infra).

So both from a density perspective and a topology perspective there are serious challenges to overcome. Which makes things like highway one even more impressive (especially when you take into account some of the territory it runs through, I think that its construction should rank right up there with the Panama Canal and the Chinese wall).

You’re absolutely correct. Highway was built around 1941 though, NA was still building itself up during that time. In an ideal world, we would be building up new cities, new rail lines, new infrastructure and etc., but I guess the momentum is lost. Now we’re stuck in “upgrade and spend a lot more for a km of subway line”. Maybe we’ll figure our way out of it eventually!

I suspect that eventually immigration will solve it but it will take a very long time.

As it is it did not look sustainable to me while I was living there.

Anything that can be called "a vacuum" is very very hard to achieve in a large volume.

Yes. That's why any kind of vacuum solution is likely a non-starter both from a technical and an economical perspective. And the 'obvious' solutions (multiple smaller evacuated chamber that connect as trains pass through) have a whole raft of safety and complexity issues and are going to increase the costs massively.

> It's not actually feasible to create a vacuum tube hundreds of km long

Why not? It's just a series of smaller sections that must each individually achieve near vacuum.

I think the main problem is that the failure of a small section is a catastrophic failure of the whole system.

I don't see why you can't compartmentalize it exactly like how I described. A leak in one of the ISS's modules wouldn't take down the whole ISS.

And then what? The train just stops in the middle of nowhere for however many days until the one chamber is fixed?

It returns obviously. Making repair or replacement of damaged sections economical is one of the engineering challenges. This by itself suggests compartmentalizing along the same lines I suggested.

It would probably be ideal if you could factory make each section and ship it on a standard truck, but with the growth of additive manufacturing, other possibilities also open up, like 3D printing the large metal container onsite.

I think you'd have to print it onsite, otherwise you have no gain in the loop being underground as you'd have to dig basically the entire ground up to swap sections.

Having a vacuum chamber large enough for a train to not only fit in but actually move through at high speed before getting to the next section still requires a few hundred meters per section if not more. That in itself is insanely difficult. Connecting multiple such sections while maintaining the vacuum is more difficult still. And still, you'll need thousands of pumping stations all around the middle of nowhere, that typically need constant maintenance.

For reference, the largest existing vacuum chamber is some 30mx35m (100 feet x 120 feet). Each one of the sections you would need here would have to be many times longer than the biggest vacuum chamber ever built to make any sort of sense.

The LHC achieves a hard vacuum over 27 km, and also features superconductors along its length, so clearly it's doable. I'm not trying to trivialize the engineering challenges here, but I've seen that people have tendency to immediately jump from "it's hard" to "it's impossible or infeasible", even though no one's even made an attempt. Some clever engineering could await discovery that makes it all simpler.

Sometimes this sort of skepticism is warranted because our understanding is sufficient (like our understanding of material science needed for a space elevator), but sometimes this is less clear, and I think hyperloop concepts fall into the latter category.

Is it large enough for a train?

The LHC tube is 27km long but ~6cm in diameter. It is true that they are pumping down a more impressive vacuum volume though, but not in the tube, but around each of the many, many superconducting magnets. That's about 9000m³ (compared to the ~150m³ of the actual tube).

Still, the LHC is hardly maintaining that vacuum continuously all year round. And it is one of the most sophisticated engineering and scientific projects attempted in history. Hardly a good idea for a train project.

It was the most sophisticated engineering not because of the long vacuum, but because of the tolerances, the semi-novelty of the superconducting coils at the time, the sensitivity of the equipment needed, and the extreme data collection capabilities needed to capture and store as much information as possible on picosecond timescales. None of these factors are necessarily applicable to a hyperloop.

Even so, once you've built one LHC, subsequent ones would be substantially cheaper because the primary difficulty is building the scientific and engineering knowledge needed while you're building it. Similar factors apply to programming: the first version of your program took awhile to build, but if you suddenly lost all of the code, rebuilding it would take a fraction of the time because you don't have to build your understanding of the domain the second time around.

Maybe all of these factors combined still wouldn't be enough to make hyperloop economical, but that conclusion is not obvious.

Nobody said they're impossible but believing that they would make sense economically even after they switched to maglev was the dumb part.

Physically impossible? Maybe, but the vacuum tube part was actually insane.

It would have been insanely difficult to maintain a useful enough vacuum over huge distances that the hyperloop was supposed to run.

A single failure in such a system could have catastrophic consequences across a huge range.

edit: beaten by @tsimionescu by a minute.

We didn't miss the part where

> Musk admitted Hyperloop was about getting legislators to cancel plans for high-speed rail in California. He had no plans to build it

https://twitter.com/alexdemling/status/1557221632837505025

https://time.com/6203815/elon-musk-flaws-billionaire-visions...

<Insert a quote about a fool and the departure of their money here>