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Hyperloop One Becomes ‘Virgin Hyperloop One’

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Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#281

Post by kbenson »

Analemma_ wrote: post #21
kumarski wrote: post #8

Something I wrote a while ago.... w/ back of the napkin calculations....... Why I wouldn’t invest a money into Hyperloop - Stabilizing a single fault line risk pylon is more than $250K. - How many million are needed for vacuum pumps to evacuate 100+ million cubic feet of of pipe to 100 Pa? - Hot air discharge needs to go somewhere. For every 1 bar pressure, you need ~200 to ~400 cubic meters of volume which is larger…

When Musk first said that an LA SF Hyperloop could be built for 1/8th the cost of the equivalent HSR, I chuckled and then waited for the punchline, which still hasn’t arrived. It’s a cool idea and I do want to see more prototypes and feasibility studies, but people need to get off the hype train (no pun intended) and be realistic about the cost.

Maybe you're looking in the wrong place for the punchline. Perhaps it will be delivered in the final bill for the HSR...

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#282

Post by mhermher »

k_sh wrote: post #260
mhermher wrote: post #216

Earlier quoted context omitted.

It's not redundant with amtrak. There's no way to get from LA to SD on passenger rail without transferring through busses.

The Coastal Starlight runs from Union Station in DTLA to Jack London Square in Oakland. From there, it's a quick walk to BART to get into San Francisco - no bus required. That being said, the trip takes 13 hours and some change, depending where in SF you're trying to go - which would be blown out of the water by HSR.

That must be new. That wasn't available as of like we years ago or so.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#283

Post by hwillis »

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…

That vacuum chamber has two sets of fifty foot tall doors. The hyperloop is an inch-thick welded steel tube. Pinholes are trivially detected by ultrasonic testers. There are no leaks. Even hydrogen and helium would take centuries to diffuse inside. The only problems are sealing the ends, which are a couple meters wide.

The hyperloop as written was very challenging, but the engineering aspects are not. The practical building (grinding the inside, transporting the tubes, etc.) are significant. The financing is insane. The theory is not even particularly hard, much less at the level of a space elevator.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#284

Post by neuronexmachina »

puranjay wrote: post #264
buckminster wrote: post #208

Earlier quoted context omitted.

Branson's business model is selling the right to use the Virgin brand to other companies. The article doesn't say he made an investment. It is rather more likely that they paid him.

So basically Trump with more class?

...and fewer bankruptcies.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#285

Post by JumpCrisscross »

schiffern wrote: post #278
the8472 wrote: post #272

Earlier quoted context omitted.

The force exerted by the atmosphere on an evacuated tube is the same as the force exerted on a standard-atmosphere filled submarine diving 10m beneath the surface. A 100kPa difference. And since they explicitly do not want a high vacuum - some residual air inside the tube is necessary for the hyperloop concept! - they don't have to deal with advanced tech like turbomolecular pumps. Simple displacement pumps will do.

Note that downthread, they've already moved the goalpost from "these pumps are technologically impossible" to "but they'll need a lot of them!" https://news.ycombinator.com/item?id=15459820

> Note that downthread they've already moved the goalpost from "these pumps are technologically impossible" to "but they'll need a lot of them!"

I never said vacuum pumps are "technologically impossible". My original comment references the Space Power Facility [1] and categorises the vacuum problem as an engineering problem. A hard one, but engineering nonetheless.

The comment you link to [2] replies to someone claiming the original white paper calls for a 22:1 atmosphere:tube pressure ratio. I pointed out that the figure they're referencing, Figure 11, discusses the capsule and not the tube.

I'm skeptical about the economics of de-pressurising the tube, but that's an engineering problem and I've always held it as such. The materials problem is the thermal expansion of the top of the tube relative to the bottom.

[1] https://en.m.wikipedia.org/wiki/Space_Power_Facility

[2] https://news.ycombinator.com/item?id=15459820

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#287

Post by dionidium »

Brakenshire wrote: post #188
jaredhansen wrote: post #185

Earlier quoted context omitted.

Of all the problems facing construction of "viable high speed rail" in the US (they already exist in many other places), I don't think Hyperloop competition is among ... the top 50. Practically anything could be "a clever political ploy", but where's the evidence for this? Any in the absence of such evidence, why speculate? Just as a thought experiment, could HN user daemin's comments be part of a clever ploy to inve…

We're just building a new major high speed line in the UK, and you'd be surprised how often you hear people say that it shouldn't be built because the technology will be superseded by the hyperloop, or autonomous cars, or whichever. It's one of the major talking points, even if it isn't one of the major blocks.

Yes, I think this is it. I don't buy into any "clever political ploy" theory, but this type of stuff does get into people's heads. The rise of Uber and Lyft are already being used in arguments against mass transit.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#288

Post by JumpCrisscross »

sbierwagen wrote: post #277
JumpCrisscross wrote: post #250

Earlier quoted context omitted.

> 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…

>Unless you're proposing we build and seal the Hyperloop tubes in space before bringing them down, the analogy isn't appropriate. I am not sure what your objection is here. Are you saying vacuum chambers can't be built on Earth? There are quite a few examples of large vacuum chambers, like the NASA Space Power Facility (23,400 m^3) or the Large Hadron Collider (9,000 m^3) https://scap.hq.nasa.gov/docs/Glenn_SpacePowe…

> I am not sure what your objection is here. Are you saying vacuum chambers can't be built on Earth?

No, I specifically linked to the Space Power Facility in my original comment! The "materials science" problem I call out is in the tube's lateral thermal expansion.

The best solution I've come up with for that is to take a regenerative rocket engine [1] and make it a tube. Pumping fluid in spirals along kilometers of a vacuum tube isn't easy, but it isn't as hard as trying to invent a material that won't deform when the top gets hotter than the bottom, or the east side gets hotter than the west.

[1] https://en.wikipedia.org/wiki/Regenerative_cooling_(rocket)

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#289

Post by kbenson »

Pxtl wrote: post #147
martinald wrote: post #77

Earlier quoted context omitted.

Is this not an attempt to just derail CAHSR, or HSR in general? Nearly every anti-HSR comment is now 'we should build hyperloop instead!'.

That's impressively cynical, but Musk obviously stands to gain a lot if people keep California using roads. California wants to go green and he sells the best technology for green road-based transportation.

I'm not sure it really affects his electronic car business one way or the other. Firstly, he isn't necessarily selling Tesla's to people for commuting between SF and LA, that's well outside his range, and as fast as the supercharging is, it loses out to regular gasoline refilling. Secondly, I'm not sure the amount of people potentially served by the hyperloop is more than a blip in the sales charts for even a regular car company (as deciding factors for car purchasing decisions, it seems relatively low to me).

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#290

Post by hwillis »

yahna wrote: post #269
JumpCrisscross wrote: post #251

Earlier quoted context omitted.

> Weren't there published papers by NASA scientists proving, without a doubt, that it's impossible to construct a booster rocket with the structural stability to return to earth? No. Going back to the 1960s, re-usable two-stage configurations were being drafted [1]. [1] http://papers.sae.org/640297/

But I thought this all came to our god king in a dream.

oh stop. People are excited about reusable rockets, a mainstay of science fiction since the beginning. Why do you have to be a wet blanket? "Elon Musk didn't think of reusing rockets, and he didn't personally build them, and he doesn't have a degree in rocketry!" You're fighting a Quixotic battle against a strawman.
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