Hyperloop One Becomes ‘Virgin Hyperloop One’ • Hacker News Board

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#251

Post by JumpCrisscross » Thu, Oct 12, 2017, 6:05 PM UTC

matt4077 wrote: post #243

thearn4 wrote: post #211

Earlier quoted context omitted.

Some colleagues of mine also did a short feasibility assessment of the original white paper, and came to some similar conclusions. The propulsion system also made some assumptions about compressor performance that seemed too optimistic compared to existing turbomachinery. That said, I have not followed closely enough to know if the hyperloop startups out there are following the original conception or if it has signif…

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? I'm willing to give this guy the benefit of the doubt considering his track record. It's also instructive to read the comments when the original Hyperloop idea was published. Even the people thinking Musk would fail were in the minority, becau…

> 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/

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#252

Post by kbenson » Thu, Oct 12, 2017, 6:07 PM UTC

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…

> I think it would be a good idea to make sure the California "high speed" rail program is never funded.

Never funded? It's already under construction[1]. Although it's likely pre-pre-pre-construction, as they grade items and fix obstacles for the actual railway construction, which I doubt will happen within a decade, if ever.

1: https://www.buildhsr.com/interactive_map/

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#253

Post by dnautics » Thu, Oct 12, 2017, 6:07 PM UTC

JumpCrisscross wrote: post #241

thearn4 wrote: post #211

Earlier quoted context omitted.

Some colleagues of mine also did a short feasibility assessment of the original white paper, and came to some similar conclusions. The propulsion system also made some assumptions about compressor performance that seemed too optimistic compared to existing turbomachinery. That said, I have not followed closely enough to know if the hyperloop startups out there are following the original conception or if it has signif…

> Some colleagues of mine also did a short feasibility assessment of the original white paper, and came to some similar conclusions Likewise. It sounds like above-surface (on Earth) is probably unfeasible given (a) security and (b) thermal concerns. For security, we just contemplated debris from the track (or a bullet from an errant rifle) puncturing the tube. Hyperloop One is testing an 3.3m diameter and 500m long t…

"a wall of air moving at the speed of sound"

What? Particles moving in through a hole against vacuum will usually be travelling at a distribution of speeds dependent on ambient temperature, usually a boltzmann distribution. It will not be a wall, but rather a gradient.

It's also not so much a maglev as an inductrack, which has only really become possible recently since it's come off-patent.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#254

Post by Robotbeat » Thu, Oct 12, 2017, 6:07 PM UTC

JumpCrisscross wrote: post #245

schiffern wrote: post #235

Earlier quoted context omitted.

> Wait, who said that they need to compress the air all the way to Earth pressure? No one. The Hyperloop alpha paper explicitly contradicts this assumption on page 18, where the flow diagram gives the compressor input at 99 Pa and the output at 2.1 kPa (a 21:1 pressure ratio). http://www.spacex.com/sites/spacex/files/hyperloop_alpha-201...

> The Hyperloop alpha paper explicitly contradicts this assumption on page 18, where the flow diagram gives the compressor input at 99 Pa and the output at 2.1 kPa (a 21:1 pressure ratio) One standard atmosphere (atm) is defined at over 100,000 Pa [1]. The 21:1 pressure ratio in Figure 11 on page 18 is for the "passenger plus vehicle capsule" [2]. I'm talking about the tube. Going from 99 to 2.1 isn't hard. Going fro…

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 keep leaks to an absolute minimum in spite of thermal expansion, etc.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#255

Post by imron » Thu, Oct 12, 2017, 6:12 PM UTC

zardo wrote: post #244

imron wrote: post #169

Earlier quoted context omitted.

To be fair, he also stands a lot to gain if Hyperloop becomes a reality.

How does that work? He had an idea and promoted it. No one's going to be paying him royalties for it.

He's also building one, so he has a vested interest in the technology being successful: https://techcrunch.com/2017/08/04/elon-musk-reportedly-plann...

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#256

Post by dmix » Thu, Oct 12, 2017, 6:12 PM UTC

TremendousJudge wrote: post #28

dmix wrote: post #15

Earlier quoted context omitted.

> Lots of marketing, very little engineering. It started as a technical whitepaper, not a marketing campaign, and multiple companies are building experimental models. I don't think this critique is accurate or fair. There have been far worse vapourware and hype-only concepts that haven't gotten close to hyperloop's tangible progress. No tech can be perfected from the planning stage either, it takes talent, money, and…

>it's not like there are some obvious alternatives are being neglected A high speed train like the ones they've had in Europe for a long time? You know, the ones that regularly reach 300 km/h? If that's not fast or flashy enough for you, what about Maglev? It actually exists, and the tracks are extremely expensive even though they don't even have to maintain low air pressure

> A high speed train like the ones they've had in Europe for a long time?

I don't see what the US political inability to build infrastructure has to do with my comment. Plenty of countries are still building highspeed trains and iterating on that model... and plenty of non-US countries are looking into hyperloop, the first ones to adopt it will likely be outside of the US, as that's where most innovation is these days. And regardless there's always plenty of room for new ideas.

Unless you think these billionaires should be backing American transportation mega-projects instead? There's plenty of roadblocks there outside of access to capital, where a highspeed train will likely cost 2-3x the initial projections, even if a private company does it. Not to mention the US is a car-heavy market. It seems like a risky project for any non-government entity to take on as it will be packed full of political risk and direct involvement either way...

The US rarely builds major projects anymore except in the defense industry. And almost every major defense project of comparable size ends up being billions over budget or cancelled.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#257

Post by schiffern » Thu, Oct 12, 2017, 6:13 PM UTC

JumpCrisscross wrote: post #241

thearn4 wrote: post #211

Earlier quoted context omitted.

Some colleagues of mine also did a short feasibility assessment of the original white paper, and came to some similar conclusions. The propulsion system also made some assumptions about compressor performance that seemed too optimistic compared to existing turbomachinery. That said, I have not followed closely enough to know if the hyperloop startups out there are following the original conception or if it has signif…

> Some colleagues of mine also did a short feasibility assessment of the original white paper, and came to some similar conclusions Likewise. It sounds like above-surface (on Earth) is probably unfeasible given (a) security and (b) thermal concerns. For security, we just contemplated debris from the track (or a bullet from an errant rifle) puncturing the tube. Hyperloop One is testing an 3.3m diameter and 500m long t…

sigh another "deadly wall of air" theory ala Thunderf00t? Hasn't this been debunked already?

"A little bit of physics is a dangerous thing."

* A bullet or piece of debris would likely leave a hole much smaller than the diameter of the tube. A breach 1/10th the diameter of the tube will admit 1/100ths as much the air.

* Even if there was a whole-tube breach, the "wall of air" will rapidly slow down and smear out into a gradual pressure rise due to friction with the tube walls. Pipes are not lossless! Within 5 km friction will have the air moving at highway speeds. So if you're so close that you can be killed by the air blast, you're so close that the pod can't brake before hitting the whole-tube breach (bad). In other words, "deadly pressure waves" don't increase your odds of dying beyond that of a regular "derailment" event.

* In the event of a breach (whole-tube or otherwise), sensors in the track will signal all the pods to stop and the tunnel to undergo emergency re-pressurization. So any "wave" won't get far.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#258

Post by manigandham » Thu, Oct 12, 2017, 6:14 PM UTC

noonespecial wrote: post #215

manigandham wrote: post #161

Earlier quoted context omitted.

Sure, it's a combination of political/social/economic factors but "futuristic" doesn't seem to have much impact right now (if it ever really did). NASA's trip to the moon was funded by war motives and we've since had the decline of both the space station and the shuttle programs. It's great to see SpaceX doing new things but there's definitely profits in reducing launch costs (again driven by war and business motives…

Yes airlines are the first thing that spring to mind when I think of wifi, food, and convenience during travel. Call me an optimist but it's high time for something new to shake things up. I don't care if it's a magic tube train or just some really nice selfdriving busses.

You're obviously talking about transit for the mainstream in which case it's not perfect but airlines provide the best combination of speed, comfort, and service today. Let's not forget that you're actually flying in the air in an incredible machine.

We already have plenty of cheap bus drivers though so I don't see what self-driving buses will do...

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#259

Post by sigmar » Thu, Oct 12, 2017, 6:14 PM UTC

manigandham wrote: post #152

sigmar wrote: post #142

Earlier quoted context omitted.

>so putting them in a low-pressure tunnel is not a major revolution. >evacuated train tunnel with air or magnetic tracks does not require new science. The hard part is evolving the tech to be reliable and cheap so that people will use it and pay for it - but that doesn't seem to be within economic reach, and that's before factoring in construction and upkeep. You seem to be suggesting that a) we could have done this…

Yes it's possible to build, but no it's not cheap enough to make money on = not worth building. We can build lots of fantastic things today but they would cost trillions so clearly are not a good idea. You also missed the ending about construction + maintenance, those will be the real costs and aren't likely to become radically cheaper.

To the generations that traveled the world on boats, constructing flying machines that move faster (and required more tech/maintenance) also probably seemed like an unknown of whether it would be prohibitively expensive or not. I'm grateful that they didn't wait long to explore the possibility, which is what Virgin is doing here.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#260

Post by k_sh » Thu, Oct 12, 2017, 6:16 PM UTC

mhermher wrote: post #216

microcolonel wrote: post #207

Earlier quoted context omitted.

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 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.