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Hyperloop One Becomes ‘Virgin Hyperloop One’

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Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#301

Post by JumpCrisscross »

hwillis wrote: post #292
JumpCrisscross wrote: post #271

Earlier quoted context omitted.

> ala Thunderf00t Just watched one of his videos on this--interesting and thank you for the pointer. Agree with you on his overstating the deadliness of pressure pulses. 30 kg of TNT is a lot of energy, certainly enough to knock your infrastructure out of commission for a couple days. The "everyone dies if the tube is punctured" argument is hyperbolic, though. The materials science problem is the thermal expansion. A…

> It's the transverse expansion. If these are above ground, the top will heat up relative to the bottom. That's a nasty problem to solve while maintaining the structural integrity to keep a giant vacuum with speeding capsules in place. Right... you can probably solve that with a bucket of white paint. Worst case you cover it with an aluminum shield- aluminum does not absorb infrared radiation and will reflect 99.9% o…

> you can probably solve that with a bucket of white paint. Worst case you cover it with an aluminum shield- aluminum does not absorb infrared radiation and will reflect 99.9% of ambient heat

It's, unfortunately, harder than this. It's a similar problem to the ones we dealt with regarding rockets, standing fueled, on a pad. Both methods you propose were tried. The solution is to (a) paint it and (b) launch before the gradient becomes too big.

The stresses on the Hyperloop tube, when a capsule is rushing through it while it's containing a near vacuum, are comparable to those on a rocket nearing max Q [1]. The difference is with a rocket we take great care to maintain symmetry. With the Hyperloop, that isn't an option. That persistent asymmetry is what makes it a difficult materials problem, particularly if we're using any known metals (even wonderful light and thermally-conductive aluminium).

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

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#302

Post by aswanson »

KGIII wrote: post #194
aswanson wrote: post #74

Earlier quoted context omitted.

I remember that thread. Hilarious.

One of my favorites is on Slashdot. If you go there and search for 'VMware' then you can find it. When VMware was first announced and demoed, the commenters at Slashdot declared things like it was fake, it was stupid, it was a waste, it would never work, or that dual booting was a better solution. They largely concluded that virtual machines weren't a thing and happily congratulated themselves for their brilliant ins…

Reminds me, Im just as guilty. Check out my insights on Amazon introducing the Kindle: https://news.ycombinator.com/item?id=81804

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#303

Post by hwillis »

KekDemaga wrote: post #133
inetknght wrote: post #75

Earlier quoted context omitted.

sealed telescoping tube between pylons then?

That sounds really expensive.

At this pressure you can use regular o-rings, which already come in standard sizes up to a dozen meters across. They're very affordable. I still doubt they'll be necessary.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#304

Post by dnautics »

mseebach wrote: post #236
pstuart wrote: post #205

Earlier quoted context omitted.

On land gifted to them by the government.

Given the key function railroads had in opening up the west, I think you'll struggle to argue that that was even close to a bad deal. Indeed, that, if anything, is exactly the kind of investments that a government should be making.

nongovernment investments tend to be more sustainable, because they are driven by observed demand, instead of cronyism or politics. This was one of the few railways to survive the great railway crash, it's still operated today:

https://en.wikipedia.org/wiki/Great_Northern_Railway_(U.S.)

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#305

Post by JumpCrisscross »

Robotbeat wrote: post #296

The biggest problem people have with Hyperloop is because it certainly seems like Elon Musk just waltzed into the high speed rail debate and Dunning-Krugered some crazy scheme that doesn't look anything at all like conventional approaches to the problem and thus doesn't jive with any common sense we might have built up around different transport methods. But that's kind of what Elon Musk does: he Dunning-Krugers hims…

> Elon Musk just waltzed into the high speed rail debate and Dunning-Krugered some crazy scheme

I think it's incredibly important to segregate Musk's work, i.e. SpaceX and Tesla, from his proposals, e.g. the Hyperloop, modular infrastructure and other things.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#306

Post by wbl »

JumpCrisscross wrote: post #250
hwillis wrote: post #231

Earlier quoted context omitted.

> The Hyperloop’s thermal issues are a hard enough problem that they alone put this in the domain of materials science. That’s the same category of problems separating us from a space elevator. What? What are you even talking about?? That's a completely ridiculous statement. The pressure inside and outside the lunar landing module was 1,000,000,000,000,000x. 100 kPa to 10^-10 Pa. It makes zero sense to apply this kin…

> The pressure inside and outside the lunar landing module was 1,000,000,000,000,000x. 100 kPa to 10^-10 Pa We didn't pump air into the lunar module from the Moon. We carried it from Earth pre-pressurized. Unless you're proposing we build and seal the Hyperloop tubes in space before bringing them down, the analogy isn't appropriate. Also, consider a soda can. It's stronger when pressurized from the inside. Modern nuc…

An evacuated tube on earth needs to sustain 1 atm.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#307

Post by schiffern »

JumpCrisscross wrote: post #266
Robotbeat wrote: post #254

Earlier quoted context omitted.

But that's no challenge at all. You're just describing a usual vacuum pump. And just a single-stage roughing pump (Harbor Freight, anyone?) can get down to less than 1 Pascal, so 100Pa is a piece of cake. That's only needed for slight leaks in the tube, not for the pod itself. Keep in mind that the absolute pressure difference is far less for Hyperloop than for a typical natural gas pipeline, and yet the latter can k…

> You're just describing a usual vacuum pump Scaling is hard. The largest vacuum chamber we've built is a fraction of the size of the proposed Hyperloop. It was a very, very hard problem [1]. It's expensive, sucks up loads and loads of power and needs lots of thermal management, structural reinforcement and vacuum-off maintenance. > Keep in mind that the absolute pressure difference is far less for Hyperloop than for…

>The largest vacuum chamber we've built is a fraction of the size of the proposed Hyperloop. It was a very, very hard problem [1].

Do we really have to say that a long extruded tube that only has to maintain low vacuum is a lot simpler than the SPS?

SPS: big thing made up of many custom one-off parts that runs at 1/380,000,000ths of an atmosphere and can blast test articles with intense simulated sunlight.

Hyperloop tunnel: big thing made up of many identical parts that runs at 1/1,000ths of an atmosphere.

>It's expensive, sucks up loads and loads of power

I think they know that, don't you? There's no line-by-line breakdown, but the paper allocates $260 million for the station+pumps and 21 MW for electricity consumption (pumping, accelerating pods, and charging pod batteries).

>needs lots of thermal management

I agree that you need it, but what specific problem do you see?

>Pipes are pressurized from the inside. See my comment from elsewhere in the thread on why vacuums are different [2].

You said a soda can is stronger when pressurized from the inside. That's true, but the obvious solution is to make it thicker than a soda can. :) The paper calls for 0.8-1.0 inch thick steel, which my math says is more than adequate.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#308

Post by gaius »

Brakenshire wrote: post #249
mseebach wrote: post #223

Earlier quoted context omitted.

Meh. The imminency of "Major New Technology Just Around The Corner" has always been a favourite argument for the anti-progress crowd. EDIT to add: Before Hyperloop, it was Maglev. And frankly, a significantly better argument against HS2 is that it's an impossibly expensive boondoggle.

> a significantly better argument against HS2 is that it's an impossibly expensive boondoggle. Nah, it connects most of England's largest cities, and will be 2/3rds of the network which will connect all of the cities of the North of England into something approaching a single labour market. Liverpool, Leeds, Sheffield, Manchester, Birmingham will be all be within 30-50 minutes of each other, with London within an hou…

It would have been politically a LOT easier of they'd built a Birmingham-Newcastle leg first

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#310

Post by JumpCrisscross »

DiThi wrote: post #297
JumpCrisscross wrote: post #271

Earlier quoted context omitted.

> ala Thunderf00t Just watched one of his videos on this--interesting and thank you for the pointer. Agree with you on his overstating the deadliness of pressure pulses. 30 kg of TNT is a lot of energy, certainly enough to knock your infrastructure out of commission for a couple days. The "everyone dies if the tube is punctured" argument is hyperbolic, though. The materials science problem is the thermal expansion. A…

> If these are above ground, the top will heat up relative to the bottom. The heat will quickly conduct to the other side. It's one of the main reasons for choosing steel. Add white paint to that (or solar panels) and you'll have reduced heat absorption to a minimum.

> The heat will quickly conduct to the other side

I take it you haven't had the pleasure of watching carefully machined cylinders buckle in the Arizona sun :). White-painted aluminum and shaded, mind you.

Those were structures on the order of meters. These problems become nasty with scale.

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