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Hyperloop One Becomes ‘Virgin Hyperloop One’

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Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#331

Post by schiffern »

JumpCrisscross wrote: post #285
schiffern wrote: post #278

Earlier quoted context omitted.

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 claim…

>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 happen to be that someone. :) You were talking about state-of-the-art axial compressors (the GEnx-2B67), so I assumed you were talking about the axial compressor on the front of the pod. Mea culpa. But then you drew an analogy to the pressures in the SPS ("To get a sense of the engineering differences between 6:1 and 1,000:1..."), as if the Hyperloop people were trying to make a 1000:1 axial compressor. As I pointed out in my reply,[1] rotary vane compressors can easily maintain those pressures.

>The materials problem is the thermal expansion of the top of the tube relative to the bottom.

If that were really a problem, no pipelines of any kind could be built. Again thermal expansion joints are the solution, since with the abandonment of air-ski levitation the pod walls no longer have a requirement to be ultra-smooth. Tiny leakage on these joints is fine, since it will be made up for by the pumps located along the track.

[1] https://news.ycombinator.com/item?id=15460061

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#332

Post by JumpCrisscross »

sbierwagen wrote: post #330
JumpCrisscross wrote: post #324

Earlier quoted context omitted.

> Regenerative cooling in rocketry is running propellant through channels in the nozzle, then either dumping it overboard, using it to power a gas generator, or burning it in the rocket "Regenerative cooling" is a rocket term. It came to mind because I used to be an aerospace engineer. There's no requirement in the definition of regenerative cooling for the coolant to be dumped. > Presumably active cooling of a hyper…

> "Regenerative cooling" is a rocket term. It came to mind because I used to be an aerospace engineer. There's no requirement in the definition of regenerative cooling for the coolant to be dumped. ? Regenerative cooling in rocketry uses propellant. Propellant is always dumped overboard, because it's propellant. Please show me a rocket that uses closed loop cooling of the rocket nozzle. > Filtering and then compressi…

> Please show me a rocket that uses closed loop cooling of the rocket nozzle

The most famous one is the under-development SABRE [1], which includes a closed-loop helium cycle. For cryogenic rockets, closed-loop cooling of the nozzle has been explored [2] to avoid hydrogen embrittlement and oxidation of the nozzle channels, as well as to simplify plumbing.

In any case, we've devolved into arguing semantics.

> My turn to be pedantic about definitions: this sure sounds like closed loop cooling to me!

I was figuring on dumping the air once done versus worrying about a reservoir. That said, I haven't done any math on the benefits of saving the return piping (and reservoir cost and maintenance) versus using something traditional.

> maintaining the air dryers and replacing the filters sounds like it wouldn't be any cheaper than conventional phase-change cooling, and having to build custom vacuum/compressor pumps for the hyperloop project is going to be more expensive than buying COTS vacuum pumps

Fair enough. As you observe, it's a problem I haven't seen a suitable solution to (apart from burying, which trades the thermal problem for, in my view, the better water management problem and the scarier land-use problem.)

[1] https://en.wikipedia.org/wiki/SABRE_(rocket_engine)

[2] https://www.google.com/patents/US3516254?dq=closed+loop+rock...

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#333

Post by nihonde »

Animats wrote: post #295

Maglev in a tube is a proven technology at full train scale. Here's the Chuo Maglev from the inside.[1] 500KPH in tunnels. They're not pumping down the tunnels, just plowing through on sheer power and money. The Chuo Maglev makes the Hyperloop One look like a toy project. Watch the video. They have a production-quality train, with tourists and whiny kids riding it, going 500km/h. They've hit 603km/h in tests, but don…

Amen. If you want a fast train in 2017, hire the people who have been winning in that department since 1964.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#334

Post by [deleted] »

JumpCrisscross wrote: post #305
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.

[deleted]

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#335

Post by Frondo »

microcolonel wrote: post #207
daemin wrote: post #165

Just as a thought experiment, could the promotion of these "hyperloop" projects be a clever political ploy to misdirect/divert attention and prevent a viable high speed rail network from being built? Elon's main business is electric cars and (one of) Branson's is airlines. So a reasonable competitor to both is fast and cheap(er) public transport along a major travel corridor in the USA. This means that by promoting t…

I think it would be a good idea to make sure the California "high speed" rail program is never funded. It is a terrible idea. As it stands, it would be as slow as conventional rail, redundant with AmTrak, and the most expensive rail line ever built. It would be absolutely devastating for the government's relationship with at least tens of thousands of land owners, hundreds of thousands of home owners, who would see d…

It's a great idea and I can't wait to see more high speed rail built all across the country.

We've already criss-crossed uncountable acres of historic, sentimental (what?? really??) land with roads, both local the state/federal highway system. HSR would be so much better use of land than roads, for moving a lot of people quickly and comfortably. Not at all redundant with Amtrak.

Happily, the California project is funded and is already underway, and I think there's one or two others being talked about/planned.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#336

Post by dclowd9901 »

LeoPanthera wrote: post #34
lisper wrote: post #17

Earlier quoted context omitted.

Not ones that will hold a vacuum.

Not with that attitude.

Your comment may seem flippant, but honestly it seems like people are more eager to be right than aspirational these days.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#337

Post by schiffern »

JumpCrisscross wrote: post #316
schiffern wrote: post #307

Earlier quoted context omitted.

> 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…

> I think they know that, don't you? Who's they? Hyperloop One? No--they've just punted the "hard" stuff to the end. (Kind of like the Wright Brothers designing the seats of their plane before getting it flying. Oh look! [1]) Elon Musk? Yes--I do. That's why he's waiting. > what specific problem do you see? The top heats up and the bottom doesn't. > The paper calls for 0.8-1.0 inch thick steel, which my math says is…

>No--they've just punted the "hard" stuff to the end.

Citation needed. The link provided gives no support.

I would be interested in seeing your calculations on the thermal side. An ANSYS multiphysics simulation (the software SpaceX uses) would show the problem, no?

SpaceX has already built and used a mile-long, 11' diameter vacuum tube in Southern California, which would seem to put this matter to rest (the proof is in the pudding, after all).

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#338

Post by ac29 »

mhermher wrote: post #282
k_sh wrote: post #260

Earlier quoted context omitted.

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.

That rail route has ran continuously since 1971: https://en.wikipedia.org/wiki/Coast_Starlight. The transbay tube connecting Oakland to San Francisco via BART opened in 1974.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#339

Post by jychang »

dnautics wrote: post #304
mseebach wrote: post #236

Earlier quoted context omitted.

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.)

> This was one of the few railways to survive the great railway crash

The government well made its money back before the great railway crash.

Let's say the Internet suffers a crash in a few decades. Few would argue that any previous investment into the Internet was not worth it.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#340

Post by Frondo »

nradov wrote: post #226
valas wrote: post #219

Earlier quoted context omitted.

"it would be as slow as conventional rail" - citation? Even Reason Foundation (which is as biased as it gets - it's funded by Koch brothers and ideological critic of almost any government investment) claim SF to LA times will be 3:30 to 4:40, which is faster than any train today.

That's barely faster than driving, once you account for the time spent moving between your origin/destination and the train station as well as transferring luggage.

3 and a half hours is way faster than driving. And for the comfort of being on a train? Worth it!
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