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

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#61

Post by lisper » Thu, Oct 12, 2017, 2:53 PM UTC

ErikVandeWater wrote: post #31

lisper wrote: post #10

All of the Hyperloop development efforts are ignoring the elephant in the room: thermal expansion. If you do the math, the ends of a viable hyperloop track will have to move hundreds of meters [1]. No one has yet advanced even a viable idea for how to deal with that, let alone an actual design. Until that happens, the Hyperloop is vaporware. [1] It's a trivial calculation. The thermal expansion coefficient of steel i…

Just to clarify - is the thermal expansion issue both in terms of the length of the hyperloop and the inside diameter of the tube, or just the length? Relevant discussion of thermal expansion with high speed tracks: http://boards.straightdope.com/sdmb/showthread.php?t=471152

It's a combination of things: the length, the fact that it has to hold a vacuum, and the fact that it can't make tight curves. If any one of these things weren't true the problem would be easy. But they are all true, and that makes it really, really hard. (Oh, and it has to have a smooth inside surface, and it has to be manufacturable at a reasonable cost.)

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#62

Post by eutropia » Thu, Oct 12, 2017, 2:53 PM UTC

ginko wrote: post #9

Faaak wrote: post #6

Earlier quoted context omitted.

The CERN LHC tube is a 27km circle of vacuum and near-zero temperature, and they don't seem to have a problem with that (granted, they had some but it's solved now). Frankly, yes, there may be issues, but I'm confident that the Human race will be able to overcome those.

The LHC's vacuum pipes are 6.3 cm in diameter..

Yeah, LHC's is the largest in the world at just 15,000 cubic metres -- equivalent to about 1 km of hyperloop tunnel (assuming 14ft diameter mentioned in the Boring Company's FAQ)

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#63

Post by logicallee » Thu, Oct 12, 2017, 2:54 PM UTC

sschueller wrote: post #3

When are we going to address the elephants in the room? Just the tube alone: - largest pressure vessel in the world. How do you keep it at near vacuum? - Thermal expansion over such a large distance, especially if the top of the tube is warmer than the bottom. - Safety, how does an evacuation look like if the tubes are sealed?. There are many more. Some how I feel like this is a "pipe" dream. Lots of marketing, very…

Out of curiosity, have you ever built anything big? I say this because the tone of your comment is dismissive, however it seems quite low-effort. I can translate your criticisms into criticisms of building subways in 1863:

  - if you build a subway it will be the biggest underground railway ever built.
  - Rocks.  They could fall in front of a subway car and cause a huge accident.
  - safety.  what if all the lights and power go out?  Also how would anyone breathe down there.

And my criticisms seem stronger, not weaker, than yours. Today all cities with robust subway systems benefit hugely from them and all of these issues have been resolved.

The criticism you've offered seems equally low-effort, so this is why I'm curious if you've ever helped design and build any large-scale project.

I don't like gratuitous negativity on HN and it's against the rules here.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#64

Post by lisper » Thu, Oct 12, 2017, 2:55 PM UTC

Robotbeat wrote: post #51

lisper wrote: post #17

Earlier quoted context omitted.

Not ones that will hold a vacuum.

Did you try googling? Here's a whole bunch: http://www.metraflex.com/metal-expansion-joints/

Let me be more precise: not ones that 1) will hold a vacuum and 2) are available in the 3+ meter diameter that the hyperloop requires and 3) provides the smooth inside surface that the hyperloop requires and 4) are economically viable.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#65

Post by arketyp » Thu, Oct 12, 2017, 2:55 PM UTC

I feel that name has got to be a double entendre.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#66

Post by nkoren » Thu, Oct 12, 2017, 2:56 PM UTC

lisper wrote: post #54

Gustomaximus wrote: post #48

Earlier quoted context omitted.

I dont know if this an elephant in the room. I'm guessing engineers have thought about this and just not discussed it publicly. They have some pretty smart guys. Also to nitpick, from "the ends of a viable hyperloop track will have to move hundreds of meters" - this doesn't have to be true. There can be absorption points along the track. Overlaps. Or maybe they tunnel the entire way where its cooler. Or wrap the tunn…

> There can be absorption points along the track Sure, but these have to hold a vacuum. No one has figured out a way to do that.

I am assured by those in a position to know that thermal expansion joints which hold a near-vacuum are an entirely solved and essentially trivial problem.

I do have some concerns about whether they're a trivial problem within this context. An engineering solution which works in small numbers for PhDs in a lab isn't necessarily scalable to mass low-cost manufacturing, deployed in the field and irregularly serviced by workers of uncertain provenance. But evidently there is a way to do this, at least.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#67

Post by Avshalom » Thu, Oct 12, 2017, 2:56 PM UTC

Gustomaximus wrote: post #44

batrat wrote: post #16

I see so many negative comments about this, but in my opinion everything has to start somewhere. It doesn't matter how crazy and impossible it looks, it will be done eventually (and we have plenty of examples). Maybe we will not teleport in 2 seconds across the globe or this project will die, who knows if we don't try. A little bit of optimism doesn't hurt. Just saying. And for Virgin, it's not my money, if they want…

So much this. Especially when people chime in with some minor detail means it will fail because clearly 'must not have thought of it' if they didnt mention in some 400 word press release. Its like Elon going into trucking and people saying the range isn't sufficient. The guy is pretty darn smart. I'm confident he understands trucking range and has some solutions, and simply isn't discussing it for secrecy and/or succ…

Yeah but in this case every solution appears to be turning it into a normal train so we aren't even getting anything novel out of it anymore.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#68

Post by Chathamization » Thu, Oct 12, 2017, 2:56 PM UTC

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.

> When Musk first said that an LASF 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.

Yeah, and that proposal was for something with much lower throughput, that didn't have stops along the way, and didn't even reach the same areas (they saved money by stopping outside both cities, which the rail line wouldn't do). It also assumed that the tubes could just be placed along the highway meridians (a lot of the money it was supposed to save was from this).

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#69

Post by platz » Thu, Oct 12, 2017, 2:56 PM UTC

uptownfunk wrote: post #19

Lots of comments about how this is not feasible, but wasn't spaceX's vision of a reusable rockets similarly not feasible at the outset and they've since been making some quite considerable progress towards this.

HN certainly did _not_ take a "not feasable" stance on spaceX's vision of a reusable rockets.

Re: Hyperloop One Becomes ‘Virgin Hyperloop One’

#70

Post by pasta » Thu, Oct 12, 2017, 2:57 PM UTC

lisper wrote: post #56

pasta wrote: post #33

Earlier quoted context omitted.

Yeah, Elon Musk never thought about that because he was busy landing rockets. Come on.. why do you think he did not think about that? By the way, curves in the track can eliminate this when they can slide a little. And I can imagine there are more and better solutions.

> why do you think he did not think about that? Because this issue has been brought up many, many times since the Hyperloop paper was first published and no one has yet proposed a viable solution. > curves in the track can eliminate this when they can slide a little But you can't curve the track. The track has to be very nearly straight or the G forces become intolerable. This is the thing: lots of people glibly prop…

Elon has proposed a solution as others also already comented.

And why would large diameters not work?