Remember when Elon Musk used hyperloop and boring company to build nothing in the US as a way to shut down public transportation efforts?
this post was submitted on 24 Feb 2024
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It was kind of genius TBH, since the benefit of that strategy helps Tesla in a roundabout way. He's such an awful human.
Some people are skeptical this technology can ever work, but it appears CASIC's Phase 1 testing in a 2km tunnel has given them the confidence to proceed to Phase 2 testing in a 60km long tunnel.
Chinese railway engineering leads the world so I have a hunch that if any nation can pull this off, then it's China. However, lots of questions remain. A back-of-the-envelope calculation says that to achieve those speeds in the 2km test tunnel deceleration would have been about 3G. That's the same as a rocket at lift-off and not many people's idea of comfort.
The concept and technology isn't the issue. It's just not economically or technically feasible at scale.
Well... testing is how you figure out how to make it feasible, though.
Its literally just not worth it, all while being stunningly dangerous. When a zero pressure vacuum ruptures, it violently contracts, generally crushing itself.
This will require a zero pressure vessel as wide as a train, that is hundreds or thousands of miles long to be viable. One hole in the thousand mile line will shut the whole system down while it's repaired and then depressurized. This strands any other trains in the tunnel until this is done, so your "superspeed" tunnel is really super slow. Even if they have some kind of "safety valvue at set intervals that means the whole line doesnt go down on pressure gain, you still cant use the rest of the line.
So for this to work, you need multiple redundant tunnels, all of which can be taken down by one person with a gun at any point along a long, long track.
So you can spend just endless billions, literally hundreds of billions, making these redundant train tunnels that still aren't redundant, or you can spin up 10x-100x as much HSR that goes 300km and actually interlink the country with truly redundant and fast transportation.
what about the crushing? will it be imminent? like there is a small failure somewhere in the tunnel and all passengers are crushed within a second? no way im ever going on that.
I'm more concerned about becoming a meat noodle from getting sucked through a goofball sized hole when there is a leak in the train hull.
cool, didnt even think about that. i asked a ~~scientist~~ GPT and
...the remains of the human would likely follow a trajectory similar to the initial ejection path. The trail could potentially extend for kilometers ..... However, the trail would not be uniform. It would likely start more concentrated and become increasingly dispersed over distance ...
🤣
And that's the say nothing of what happens when the pod loses pressure. Y'all remember the Titanic submersible that imploded last year... That would only be one possible outcome, could be a slow contained leak so you just all suffocate to death.
How much extra force does a vacuum tunnel have to withstand to avoid collapse, compared to a regular tunnel?
Dirt weighs ~1.5 tons per cubic meter. So one meter of soil depth is 15,000 N/m^2^ (1500kg * 9.8 m/s^2^) so 15 kpa/m (which is 2 PSI per yard of depth).
Vacuum can't provide more force than atmospheric pressure. Atmospheric pressure is 100kPa or 15 PSI. Adding vacuum load adds the equivalent crushing force as digging a tunnel 6.5-7m deeper (7.5 yards). I don't know why this is totally insurmountable. Take a thick walled concrete tube, coat the outside with some sort rubber, bury the tube and pump out the air.
Yes you need to seal between sections, and keep sections aligned. I'm not a civil engineer or whatever but it doesn't seem crazy hard. It just seems like... not important. It seems a lot more expensive, and less beneficial than just making a good surface transit network. Who cares if it would let me get from Vancouver to Seattle in... half an hour? If it's already taking me an hour to get to the station and find parking, and get through ticketing/security/ customs.
It's only 2 hours from Surrey to Everett in a car (ignoring customs). Maybe we should just like have a bus?
Okay, lets say making it a "subway" works, and ignore the issues with digging out a tunnel for repairs/etc.
The issue is now tunneling hundreds/thousands of miles over a varied terrain. That would be hilariously more expensive than building standard high speed rail, likely 100x or more, which at 300km/would do the 226km Vancouver to Seattle trip in 45min. In contrast, at the max 1000km/h of this theoretical bullet train, people are making the trip in 15 min instead 45min. Is that small difference worth the wild expense?
Is having 1 route be 15min instead 45 better than 10 or 100 new "vancouver to seattle" routes that take 45min?Assuming its even just 10x as expensive, you could put a HSR train down the entire West coast for the same cost of that single 150mil ultra high speed run.
Ain't exactly a good trade.
This is greatly exadurated. Some materials work as you say but there are plenty of obtions that a small leak will not collapse anything. generally we don't even assume a perfect vacuum.
The technology problems can be solved. However I don't see how anyone can afiord to build it.
What if it got cheaper though?
materials in large quantites will never be cheap.
I got an acceleration of 1.5G for the test, did you forget a factor of 2 or something? Still certainly not an enjoyable experience for passengers, but I assume it would accelerate over a much longer distance if a full track was built.
I think I'd probably be fine with 1.5Gs as long as the jerk and snap were low.
Adding in Earth's gravity it's about 1.8G total, applied at a weird angle, which might be too much for some people.
Did you also factor in that the train needs to come to a full stop in that 2km as well?
Yes, I calculated the acceleration required to accelerate to 387MPH (173m/s) in 1km.
v^2 = 2ax
(173m/s)^2 = 2a(1000m)
a = 14.96m/s^2 = 1.53g
Hyperloop? You mean a vacuum tube train. Hyperloop is Elon Musk’s name for it when he claimed to have invented it over a hundred years after it was proposed.
It's OK to use the name and laugh at his claim to have invented it
I feel like I'm going fucking mental.
I was certain for about a year the idea was pneumatic tubes like in a bank but for trains. Which I though maybe, but probably too much friction.
Then it turned into a bog standard vacuum tunnel that was all over youtube and the Internet before Musk. But everyone acts like that was the original idea.
Pneumatic tubes use a constantly generated vacuum and air pressure to move objects. It would take forever to pump out a tunnel for a single train.
No you have two loops of constantly moving air. The train then goes in and out of that tube at stations.
It's a fucking shit idea and trains are great. But I remember that and seem to be the only one. No one ever mentions that idea
Honestly not sure how that would work, but I guess it doesn't exactly matter. Never heard of it though, maybe you could dig up some article from back then.
To be fair, Socrates envisioned the TV and Jules Verne hypothesized space travel, yet you don't see people giving them credit for inventing those things
The vactrain proper was invented by Robert H. Goddard as a freshman at Worcester Polytechnic Institute in the United States in 1904. Goddard subsequently refined the idea in a 1906 short story called "The High-Speed Bet" which was summarized and published in a Scientific American editorial in 1909 called "The Limit of Rapid Transit". Esther, his wife, was granted a US patent for the vactrain in 1950, five years after his death.
After everything I've seen with tofu-dreg construction like that bridge collapsing this last week, I think I'll pass on riding a nearly supersonic Chinese train.
I think china's level of jank is a pretty broad spectrum. It might be safe, but yeah, fuck that. If that thing fails you'll be able to see that shit from space lol.
At 1000 km/hr, it'd run out of track in less than four minutes, hope it can stop in time ... Anyway not convinced there's much point in this. China should be building more suburban rail networks to fill the gaps, instead of pouring so much concrete into crazy-wide highways and toll-roads (look on satellite image, you'll see).
sometimes proving stuff with science is still worthwhile though, right?
Except the concept is already "proven" in that regard. What the issues are with it, are the same as with everything techy that needs to make it in the world - scaling it up.
It's impossible to hold a vacuum in a tube that's hundreds of kilometers long. It is impossible to build a vacuum tube that doesn't suffer because of thermal expansion. It is impossible to build that long of a tube and it not have a single dent in it across the entire way. Even if you somehow ignore physics, people don't need a train like this. There is flights. Travelling at reasonable speed has been proven for hundreds of years.
To explain it in a tldr way, I can grab a straw, put a wet tissue inside it, blow on it and in relative speeds it would go incredibly fast. Yet nobody would go for trying that with a train, since scaling it is impossible.
Science isn't just theory. Actually building stuff teaches us a lot of things, and there isn't really any other way to advance fields like materials science without hands on experiments
For reference, if atmospheric pressure at sea level is about 1 bar, "low vacuum" is between 0.3 and 0.001 bar.
Huh. Insane they actually build that. It's basically impossible to ever make it economical though. Just go slower, build more trains and lower prices. Way more benefit to society.
The US should be having a rail-measuring contest with China, not a hype®loop-measuring one.
Yeah China is doing real well in that department.
I mean if we lived in a post-scarcity utopia and build these hyperloops under ground it might be a worthwhile investment. If we had more advanced tech for tunnel digging robots and maybe 3D printing the walls out of the material we take out etc. But if you include the energy for just maintaining the vacuum against small leaks it's probably not better than airplanes. Maybe with some kind of genetically engineered bio-crete that automatically seals small cracks. But even when we'd advanced to that level of tech and automation to make it viable, it would still have to compete with a fleet of ultra cheap vertical take of electric aircraft.
It still takes the technology further, and we learn something from it that may or may not be useful in future.
Norway has enough money to build one from Kirkenes to Kristiansand. But they never will.