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.
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.
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/m2 (1500kg * 9.8 m/s2) 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.
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.
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.
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
scientistGPT and🤣
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/m2 (1500kg * 9.8 m/s2) 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