Earlier quoted context omitted.
Expansion joints are available since decades.
Not ones that will hold a vacuum.
Did you try googling? Here's a whole bunch:
http://www.metraflex.com/metal-expansion-joints/
Hyperloop One Becomes ‘Virgin Hyperloop One’
51–60 of 517 posts
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#52I wonder if the tube could be continuously woven from carbon fiber and given an aerogel insulating wrap, then the interior coated with ceramic? This would perhaps mitigate heat expansion issues.
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#53All 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…
This point is clearly addressed in the paper: The ends of the tube can slide 300 meters next to the station, and the tube is not firmly attached to the pylons but can move to accommodate the expansion.
No. The paper gets this badly wrong. It looks only at the incremental thermal expansion between pylons, and neglects the fact that in a sealed tube the thermal expansion will be cumulative.
"These would absorb the small length changes between pylons due to thermal changes, as well as long form subtle height changes." [emphasis added]
The cumulative expansion is dealt with in a single sentence:
"A telescoping tube, similar to the boxy ones used to access airplanes at airports would be needed at the end stations to address the cumulative length change of the tube."
But that's not enough. The entire track near the ends is moving by this amount. That means that the ends of the track are advancing and retreating over multiple pylons (unless you can figure out a way to cantilever the track over 300 meters). This is a completely unsolved problem.
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#54All 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…
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.
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#55Earlier quoted context omitted.
I'm not saying it can't work and we shouldn't try our best. However from what I have seen so far I am quite disappointed as even known issues aren't addressed at all. As if the people involved are blindly going at it instead of working with people who know something about pressure vessels etc. Sure sometimes you need an outside perspective but not like this.
Care to elaborate?
Thunderf00t has a good video on the problems with it.
https://www.youtube.com/watch?v=RNFesa01llk
He has some other good videos (solar roadways) but tends to spend to much time bashing creationists.
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#56All 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…
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 propose what they think is a solution, but none of them actually work.
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#57I 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…
It's been said before elsewhere, but HN is the place to go to find out why your project will never succeed. I've seen many successful projects crapped all over here when they were in their infancy / pre-success days. "Stripe?! 3% fees! So dumb. We already have lots of payment gateways. It's not hard. You just have to {list of many tedious manual steps}..."
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#58All 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…
We could replace steel with a low coefficient metal matrix composite without sacrificing stiffness or long range strength. It would blow out the cost structure however ;) Have also heard anecdotally that condensation in the tube could be a real problem. Even at near vacuum, the rapid pressure differentials can cause buildups in front of and behind the speeding vessel.
> It would blow out the cost structure however
Sure, all of these problems are solvable if you are willing to expend arbitrary resources. But the whole point of this exercise is to provide an economically viable mode of transportation. (Isn't it?)
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#59All 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…
This is only if the tube sections all move together. This could be handled at the joint between each tube section, and then the joints would only have to move a fraction of that distance.
Re: Hyperloop One Becomes ‘Virgin Hyperloop One’
#60All 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…
Is there any material available with a negative expansion coefficient that can be used to offset this? I ask because that’s how you tend to work around thermal effects in electronics.
An electronic device contains many orders of magnitude less material than a hyperloop track. There are all kinds of materials that are economically viable when measured in micrograms. Hyperloop track material has to be bought by the kiloton.