Do you really think the special interests that are making HSR so difficult and expensive would say, "Oh, do whatever you like with your tube."?

These are extremely important issues that advocates seem to be glossing over. Putting the guideway on pylons doesn't magically eliminate land issues, you will still have to deal with visual impacts, along with any number of anticipated and unanticipated problems.

Musk should do what the Germans did with the TR0x series of maglev vehicles, build a 10-20 mile test section someplace and demonstrate that is analysis is sound.

(perhaps more in the future--why wouldn't California design with this goal [350 km/h] in mind?)

There are a variety of reasons, but one important reason I have to deal with is that the speed of shear waves through soil is only on the order of a couple of hundred miles per hour. When a train exceeds the shear wave speed, ground-borne vibration waves "build up" in a manner similar to the shock wave created in air when a plane exceeds the speed of sound, causing a ground-borne vibration equivalent of a "sonic boom" that can cause problems for wayside structures. I believe the French have started to experience this with some of their higher-speed TGV experiments and we don't have a good way to handle this yet.

Perhaps a stupid question, but the shock wave forms because the trains is moving continuously over the ground? So if you put the entire thing on stilts, there would be one wave formed at t0, x0 when the train reaches pylon 0 and the next wave would be at t1, x1 etc. So the interference pattern for the waves would look vastly different. ( This holds of course only for point like trains... )

A test segment would go a long way to determining if/how much of a problem this might be in a hyperloop system.

Putting the railway or tubes on pylons would give you an opportunity to dampen or otherwise transform those vibrations wouldn't they?

Maybe, maybe not. Guideway supports (pylons) are typically founded into the bedrock which does reduce vibration somewhat, but the vertical motion of the pylon moving against the soil will still generate shear waves.

This is why a demonstration project would be useful.

Passive resilient systems could help with higher frequency vibration (above say 100 Hz or so, depending on the forces and weights involved), but for lower frequency vibration (especially below 20 Hz), the resilient elements would have to be so compliant that even a gentle breeze would create very high vibrations in the guideway itself, which would be incompatible with the speeds of the cars inside.

You could make the pylons so massive that the forces from the vehicles couldn't move it, but again you're talking about higher construction and material costs, as well as visual impacts.

edit: though, mind you, the whole capsule also has mechanical suspension

Musk has already given more than enough for the world and done more than enough. Somebody should do it, but we should not expect him to do it.

True innovators carry all of humanity on their backs, and give massively to all of humanity, present and future.

The fact that they get some monetary compensation doesn't entitle you to not be grateful and to not recognize their heroism.

It does not entitle you to imply, as you have, that they deserve the same level of praise as any person who is paid for any work whatsoever.

You are, by implication, equating Elon Musk to the teenager flipping burgers, or any other menial laboror.

That is moral treason.

Without innovators, we would all be dying in pestilence-ridden Stone Age villages. In my opinion, those who claim that innovators do not deserve the highest of possible praise _deserve_ that fate.

Musk would have a hard time innovating if he had to build his own house, grow his own food, knit his own clothes, etc. etc...

We all rely on each other to provide our basic standards of living.

Without our basic needs being satisfied, we don't have a platform from which to focus on innovation.

Yes, innovation is great, but don't act like they are the entire backbone of humanity.

If you were to calculate the sum of gains and losses between Elon Musk and humanity, it would balance out that Elon Musk is overwhelmingly the creditor, and humanity is overwhelmingly the debtor.

As with the great-grandparent of this comment, your comment is a massive moral equivocation.

Specifically, an affordable Tesla car could benefit the entire world, whereas the Hyperloop would (at least initially) only benefit people living in LA and SF.

They both have the potential to be hugely beneficial to the entire world. Although in Tesla's case it's more of a certainty... fortunately we can have both :-)

The short answer is, "yes." I've ridden on it. The slightly longer answer (as another commenter has pointed out) is that it depends on the weight of the train versus the weight of the hyperloop. I see no fundamental reason to assume that the hyperloop is lighter than the train. It could be so, but then, we could make smaller and lighter trains, too (light rail).

Plus you don't get the same natural banking off the walls he talks about, which is relevant at these speeds. While rail could bank, you better be going at the right speed when doing so, too slow and you just fall laterally off the tracks.

This is a problem even when you are at grade. The solution is known: tilt-trains. The track is banked such that the train will not fall over if it has to stop on the curve. The passenger cabin then tilts with respect to the wheels so that it always feels like the floor is "down" regardless of the speed that the train goes around the curve. The radius of curve sets the maximum speed the train can travel around it.

Did you actually read the PDF?

It doesn't carry its motor with it. That's a pretty big reason. Nor does it need the heavy-duty (and heavy!) trucks of a standard rail car.

The motor that it carries with it is about 146 horsepower. That's less than a Kawasaki Ninja street bike.

The General Electric E60 locomotives currently in use on Amtrak crank out 6,250 hp (4,660 kW) and weigh 423,000 lb (192,000 kilograms).

The weight of the tube doesn't really enter into it.

...now I'm contributing to this thread -- shoot!

My bet is that it's not significantly different to compare a light rail (subway-like) system to a hyperloop in terms of weight.

Then you get to add the rails and ties (or concrete sleepers), plus the vastly more heavy rolling stock.

The reason I said that the weight of the tube doesn't enter into it is because the tube isn't moving. The only thing that matters in terms of energy use is the rolling stock.

? You don't need to use ballast & tie track on elevated structure, in fact it's rare to do so on modern rail structures.

[1] https://en.wikipedia.org/wiki/TGV

Edit: I had the wrong numbers before, thanks to Shiffern for the correction.

So yes, you could make the rail lighter, but in order to match the proposed passenger throughput, it would have to go 700mph. Good luck with that.

As a matter of fact, only the frequency and the capacity matter. Speed matters to passengers but not to the amount of people you can move.

The hyperloop as proposed actually has fairly low throughput; conventional rail systems, particularly of inter-metro variety where high throughput is most important, best it easily. 28 passengers per capsule at a capsule every 30 seconds makes 3360 pph during rush hours. RER line A averages 30000 passengers per hour over the entire year, with rush hour capacity being much higher.

Why is speed relevant?

(People/Car)*(Car/Hour) = (People/Hour) = Throughput

At a constant frequency and higher speeds, you will simply have less trains on the track at the same time.

A bigger factor in practical capacity is loading and offloading people and switching near termini.

It's interesting to think about, but also there are probably much higher costs associated with a completely untested system like this than estimated. I wouldn't be surprised if this system, if it actually worked at all, ended up being more expensive than a HSR proposal through California that actually made sense.

Also, drag is a huge killer of efficiency and hence overall economics. Even at 500kph the drag on a train at sea level is enormous. At 1000kph it's 4 times bigger again, and you've got the sound barrier to worry about. Trying to do the same with multiple small capacity trains is astronomically worse. So, better to have reduced drag... and by now you've basically got the hyperloop.

Even when done properly, HSR has most of the limitations stated by Musk. And while it is possible that special interest groups would make the construction of Hyperloop more difficult than it is, I don't think that's an argument against giving it a try.

Edit: apparently, the weight of the train/car/etc matters more.

Out of curiosity (I'm not at all familiar with HSR)—does the Hyperloop plan increase the distance between columns or the cost to build the columns (due to materials or any other factors)?