But the thing is that electrified rail networks doesn't address the quadratically increasing losses from drag at high speeds. There's a reason you don't see railroads operating at airline speeds: drag at sea level is a killer. In fact, at high enough speeds, the energy of air travel is actually LOWER than that of a sea level train.\
Altitude gives you a lot of efficiency. The idea of the vacuum train is to bring that efficiency down to sea level. And I think it's a good idea, but a real engineering challenge. In principle, you can keep a vacuum pretty easily. Vacuum tubes remain sealed and evacuated for decades without energy consumption, for instance.
It's just at the interfaces you have to worry about leakage, and there it's a matter of careful sealing. It's possible to get really good at it. The International Space Station is full of interfaces (and thermal cycling every 90 minutes) and would quickly run out of air if we didn't know how to maintain a vacuum well at interfaces.
Yes. Apparently when jet turbines came along they were discounted as ever being useful for commercial/passenger airplanes because they were so incredibly inefficient. I mean, really incredibly inefficient.
What they didn't take into account is that the turbines allow you to fly at much, much higher altitudes. The reduced drag there more than makes up for the lower efficiency. And gets you a smoother ride and higher speeds as well.
Modern turbofan engines are much more efficient, but that's basically because they really are turbo-props with enclosed propellers, though we call them "high bypass turbofans".
And of course if jets have to drop to a lower altitude, for example because their cabin has become depressurised, range is drastically reduced.
Keeping a vacuum over a length of hundreds of km is pretty hard, and in fact, has never been done.
High vacuum like the LHC would be hard, but that’s vast overkill. Even the equivalent of just 100,000 feet would be enough for super sonic trains.
Commercial aircraft fly at ~30,000 feet which is ~30% atm vs ~1% atm at 100,000 feet. That’s edge of space territory, but sill a long way from LHC style vacuums.
https://www.avs.org/AVS/files/c7/c7edaedb-95b2-438f-adfb-36d...
PS: In terms of force it makes little difference as you go to ever lower fractions, but it’s much harder to maintain and pump down the pressure as you keep going lower.
Really, nobody is going to build a system where this is a significant issue past the design stage. So, IMO it’s a consideration but a non issue.
The LHC however deals with high vacuume becase they need particles to travel hundreds of miles without encountering any atmospheric particles. That would let trains reach orbital velocity without issue, but would be horrifically expensive.
Basicly 100% to 1% vacuume is considered rough/coarse and it cheap. 1% to 1 micron is the middle ground which is increasingly difficult but still not that bad. Under 1 micron aka High vacuume is expensive and mostly the realm of science experiments.
https://www.hydraulicspneumatics.com/200/TechZone/Vacuum/Art...
If want to go 1000km in 3-4 hrs then you are the kind of problem hyperloop might solve.
https://en.m.wikipedia.org/wiki/Beijing–Shanghai_high-speed_...
No. There is no way that a similarly capable system will be remotely close in price to conventional rail. Musk's estimates were wildly optimistic at best, and the system he proposed would have a small fraction of the capacity of HSR, for example.
The advantage of a vacuum train (let's not pretend it is Musk's invention) is top speed. In some scenarios, this may be worthwhile, but it's natural comparison would be short haul flights, not passenger rail.
In practice it is so much more complicated. You have different soils, some that are water permeable - in Boston (I think) they solved that by literally freezing the ground. Does that sound cheap?
Then you have issues going under buildings (which you always are - otherwise why bother tunnelling?). All tunnelling disturbs the ground. When they built the Jubilee line extension under the houses of parliament they had to monitor how far Big Ben started leaning, and do something call "compensation grouting" to tip it back upright (basically you drill horizontal holes under it and pump concrete under it).
Tunnelling is just expensive. That's why it only happens where the alternative - building on land is very expensive.
The problem isn't keeping the vacuum, it's making the whole thing safe and relatively cheap at the same time.
It seems like it's almost impossible to do that above ground with thermal expansion issues and very easy terrorism. But doing it in a tunnel solves some problems. The evacuation is still a big problem.
https://www.youtube.com/watch?v=0N17tEW_WEU
(note that the hyperloop will be a significantly higher vacuum. There would actually be little point in depressurizing a pipe to the level shown in the video. I hear this was done on mythbusters as well)
I think you'll agree after seeing the video: attempts to let people get out of that ... there's just no point. They'll be folded into an accordion before you can say cappuccino. Literally. Failures will propagate along such a pipe at close to the speed of sound. You wouldn't get through the first "c" of cappuccino.
You should restate the problem: the problem is the same as with trailer vs car crashes: pulling the various flattened and crushed together pieces of different people apart in a way that you'd be reasonably certain the right liter of goop recovered goes into the right casket, ideally with as little pieces of the pipe in there with them as possible.
An extra issue is that every way you might recover also fails given the forces involved. Let's say you let air in ? Well that's going to form a wall of air that'll hit with a speed, force and acceleration that is guaranteed to kill every passenger, just from the acceleration. More likely that too will fold them into an accordion.
This problem is like attempting to keep a plane intact during a crash. It can't be done, and even if you should succeed, there's no point: everyone inside will be dead from the acceleration.
Which is extremely expensive because it has to withstand huge forces trying to crush it like a an empty coke can..
Hyperloop is neighter "cheap" or "easy" to create. Its approx. 10 times as expensive to operate than "Mad-Lev" trains and 100000x as deadly if something goes wrong.
Malfunction in electric train means that it has to stop.
Malfunction in Hyperloop means all passangers are dead.
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Watch Thunderf00t rant about hyperloop and read his sources. This project is nothing more than a scam to fetch investors money.
I'm unaware of Musk asking for any particular investment in a Hyperloop project. Most Hyperloop projects are independent parties working on the idea on their own volition. Please correct me if I'm wrong.
That is until Elon can proof he can manufacture the Tube much cheaper than layering the Mag-Lev track.
Is this across the board? I'd imagine the cost estimates would differ depending on where the line would be located - on raised platforms, below ground, or at ground level e.g. a highway divider lane? Or is Hyperloop impractical for pretty much all of the use cases?
IIRC his field is chemistry, yet he explained the batteries vs fuel problem in a wilfully ignorant way.