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Well, Elon Musk said talking about hyperloop was like shooting his own foot. It was a premature idea. But the interesting part is some(more than some) people a

Well, Elon Musk said talking about hyperloop was like shooting his own foot. It was a premature idea. But the interesting part is some(more than some) people are actually trying trying to come up with a real world implementations of hyperloop and so far their verdict is 'it's doable' and they are working on it. And these people are engineers from reputed companies around the world. I don't particularly like the concept of fan boy either, but like you said, this man has impressive track records. And that's absolutely brilliant. The thing that intrigues me is in the new innovations he had in his rocket, and why NASA didn't have it before SpaceX.

sillysaurus3 12y ago
"Premature idea" is probably better phrased as "not feasible on technical grounds." Even tlb said it has huge problems. The steel expands in summer due to heat. Where does it go? Roads can expand using those interlocking teeth things, but hyperloop has to remain a closed system. Oh well. Everyone should dream once in awhile. EDIT: So... is this incorrect?
- iamcreasy 12y ago
  "Imagination is more important than knowledge." - Albert Einstein
  - iamcreasy 12y ago
    Despite down votes, I still strongly believe the idea outweighs the blame for not thoroughly answering all technical questions. And as others have already pointed out that the technical problem isn't as big as it sounds. Also Elon Musk has announced to build a 5 mile test hyperloop track in Texas yesterday.
- forkandwait 12y ago
  How about hedging your statement to "not CURRENTLY feasible using TODAY'S materials and structural concepts (trusses, etc)". Space flight and industrial production of fertilizer were both considered impossibilities when first proposed.
  - sillysaurus3 12y ago
    Sure, I'll reduce it to "Unless people make an advancement in structural materials similar to the invention of steel itself, which is to say 'fundamentally world-changing,' hyperloop is nothing more than an inspirational pipe dream, similar to world peace." (EDIT: This comment may actually get called out in the future once Hyperloop is fully deployed, as an example of some idiot's words. So it's probably more than a little dumb of me to have said this. In my defense, it's based on Hyperloop Alpha, as it's presented in the whitepaper. Their design could change radically before deployment.) If you're planning on building a closed loop out of steel, and there's nowhere for the steel to go when it expands in summer, the plan may need some rethinking. The best I can think of is some kind of inner lining, so that it has a segmented hull, like a caterpillar: https://www.google.com/search?q=caterpillar&tbm=isch https://www.google.com/search?q=caterpillar&tbm=isch But it would need to be very strong lining in order to prevent any leaks between the segments. And any kind of a leak would need to be detectable and would shut down the hyperloop until it's resolved. Between the wildly optimistic cost projections and the fundamental engineering difficulties, I'm much more inclined to call it a pipe dream than a perhaps-future-possibility.
    - vidarh 12y ago
      See my comment above - the expansion is specifically addressed. If you're going to criticize it, at least read the full whitepaper first. > But it would need to be very strong lining in order to prevent any leaks between the segments. The entire point of not requiring vacuum is to avoid having nearly as strict tolerances for leaks.
      - sillysaurus3 12y ago
        It's a "reduced-pressure tube." A leak is still a big deal, isn't it? Regardless, the core structural engineering is the focus of the criticism, not whether it might leak. Also, since Space X's whole point is to compete on cost savings, it was a little strange to hear cost projections that were so optimistic.
        12y ago
- vidarh 12y ago
  > The steel expands in summer due to heat. Where does it go? Roads can expand using those interlocking teeth things, but hyperloop has to remain a closed system. Feel free to disagree with whether or not the approach outlined is feasible, but this is specifically covered in the whitepaper. See page 5, section "Earthquakes and expansion joints" as well as page 28, section 4.2.3 "Pylons and tunnels".
  - sillysaurus3 12y ago
    To clarify, tlb's comment was in direct response to the Hyperloop Alpha whitepaper: https://news.ycombinator.com/item?id=6201728#up_6202327 https://news.ycombinator.com/item?id=6201728#up_6202327 He doesn't properly address thermal expansion of the entire system. A long straight steel tube from SF to LA will expand a total of 300 meters over a 40C temperature change. Where does it go?
    - vidarh 12y ago
      And my response is the same: See those sections.
      - sillysaurus3 12y ago
        Sure, let's go over it together. Tlb is many things, but "rarely wrong" is probably near the top of the list. He certainly read those sections before making that comment, so there must be something here which made him as an engineering expert say that it doesn't properly address thermal expansion. I'll try to run an emulator of tlb's mind, but mine is far less sharp. The tube will be supported by pillars which constrain the tube in the vertical direction but allow longitudinal slip for thermal expansion as well as dampened lateral slip to reduce the risk posed by earthquakes. In addition, the pillar to tube connection nominal position will be adjustable vertically and laterally to ensure proper alignment despite possible ground settling. These minimally constrained pillars to tube joints will also allow a smoother ride. Specially designed slip joints at stations will be able to take any tube length variance due to thermal expansion. This is an ideal location for the thermal expansion joints as the speed is much lower nearby the stations. It thus allows the tube to be smooth and welded along the high speed gliding middle section. This seems like the key sentence: Specially designed slip joints at stations will be able to take any tube length variance due to thermal expansion. There are two stations, one in SF and one in LA: http://i.imgur.com/3TavjCY.png http://i.imgur.com/3TavjCY.png (For simplicity, let's assume it's just the main route.) That would mean each station needs to absorb 150 meters of thermal expansion. (Would anyone mind double-checking that tlb's calculation is correct?) So it looks like the tube is resting on these things: http://i.imgur.com/srQjmps.png http://i.imgur.com/srQjmps.png and the plan is for the tube to expand due to heat, and the expansion will be absorbed at the two stations at the end. Is that really feasible, especially given that different points along the route could have temperature differences? I drove along Highway 1 and saw how incredibly different the weather can get, and while that's south of where the route is planned, it's easy to imagine that part of the tube could be roasting in direct sunlight while the other is cooled by rain. Something like 90 degrees F at one part vs 70F at another part. That's a difference of 32.22C to 21.11C, or a total temperature difference of 11.11C. The route from SF to LA is about 350 miles. If a tube of that length expands 300 meters, then we can divide 300 meters by 350 miles to get the total expansion over a single mile. So a variation of 40C would give an expansion of 0.85 meters within a single mile. Since the variation in that scenario would be ~11C, multiplying the expansion by 11C/40C equals an expansion of 0.235 meters. So I suppose the question is: Is it feasible for those things the tube is resting on to absorb a quarter meter of expansion without that expansion being pushed all the way up to the station? It's the temperature differential along the route that seems to matter, not necessarily the difference from summer to winter. Judging by this screenshot: http://i.imgur.com/wgUJqWr.png http://i.imgur.com/wgUJqWr.png ... it seems like an expansion of 0.25 meters might be a big deal. But I don't know what I'm talking about. Is all of that about right so far? I'd also be curious whether the thermal expansion results in the tube becoming bigger in the circular direction, like a bigger "O", or if it expands parallel to the tube, like becoming a longer tube. Or even both. It seems like the plan addresses this with the first part of that paragraph: The tube will be supported by pillars which constrain the tube in the vertical direction but allow longitudinal slip for thermal expansion as well as dampened lateral slip to reduce the risk posed by earthquakes. In addition, the pillar to tube connection nominal position will be adjustable vertically and laterally to ensure proper alignment despite possible ground settling. But again, where precisely does 0.25m of steel go? I'm having trouble visualizing how the pillars could "allow for 0.25m of longitudinal slip over 1 mile." I realize that a temperature variation of about 10C over 1 mile is a little extreme, but we should examine how the system handles extreme situations.
- Crito 12y ago
  Just let it bow up and down when it expands, and call it a rollercoaster. ;)
- reneherse 12y ago
  Humans have been engineering expansion joints for various types of continuous structures for well over a hundred years, including sealed pipelines. The new design requirements and constraints posed by the Hyper Loop concept just increase the complexity of the problem. Certain engineers love this kind of challenge.
- dredmorbius 12y ago
  There was a 1970s proposal for an underground tunneled very-high-speed transport quite similar to the hyperloop. Partially-evacuated tubes, relatively small vehicles. Cost and other considerations torpedoed it. Look up R.M. Salter at RAND: "The Very High Speed Transit System" (August, 1972) "Trans-Planetary Subway Systems -- A Burgeoning Capability" (February, 1978) http://www.rand.org/pubs/papers/P4874.html http://www.rand.org/pubs/papers/P4874.html http://www.rand.org/content/dam/rand/pubs/papers/2008/P4874.pdf http://www.rand.org/content/dam/rand/pubs/papers/2008/P4874.... http://www.rand.org/pubs/papers/P6092.html http://www.rand.org/pubs/papers/P6092.html http://www.rand.org/content/dam/rand/pubs/papers/2009/P6092.pdf http://www.rand.org/content/dam/rand/pubs/papers/2009/P6092.... Similar / more: http://en.academic.ru/dic.nsf/enwiki/6107059 http://en.academic.ru/dic.nsf/enwiki/6107059
- catshirt 12y ago
  of course a profound technical concept will provoke questions regarding its technical feasibility. so what is your point? that it's impossible? that it shouldn't be attempted? that it's not a problem worth working through? "naysaying" doesn't mean "saying no". "naysaying" is the inability to see a little further into the future based on the knowledge we have today. > "The steel expands in summer due to heat. Where does it go?" a cliche example but- i'd love to be the anachronistic fly on the wall listening to all the "where will the hot metal go???" people talking to the Wright brothers.
mcdonji 12y ago
It seems to me Musk was attempting to get the people who should be pushing bold new ideas to do so. The Hyperloop idea might have been premature but it certainly engaged people in discussing radical new ideas rather than discussing minor tweaks to an existing concept. That general thought is imbued in the culture of the companies he is involved with.

sillysaurus3 12y ago

"Premature idea" is probably better phrased as "not feasible on technical grounds." Even tlb said it has huge problems. The steel expands in summer due to heat. Where does it go? Roads can expand using those interlocking teeth things, but hyperloop has to remain a closed system. Oh well. Everyone should dream once in awhile. EDIT: So... is this incorrect?

iamcreasy 12y ago
"Imagination is more important than knowledge." - Albert Einstein
- iamcreasy 12y ago
  Despite down votes, I still strongly believe the idea outweighs the blame for not thoroughly answering all technical questions. And as others have already pointed out that the technical problem isn't as big as it sounds. Also Elon Musk has announced to build a 5 mile test hyperloop track in Texas yesterday.
forkandwait 12y ago
How about hedging your statement to "not CURRENTLY feasible using TODAY'S materials and structural concepts (trusses, etc)". Space flight and industrial production of fertilizer were both considered impossibilities when first proposed.
- sillysaurus3 12y ago
  Sure, I'll reduce it to "Unless people make an advancement in structural materials similar to the invention of steel itself, which is to say 'fundamentally world-changing,' hyperloop is nothing more than an inspirational pipe dream, similar to world peace." (EDIT: This comment may actually get called out in the future once Hyperloop is fully deployed, as an example of some idiot's words. So it's probably more than a little dumb of me to have said this. In my defense, it's based on Hyperloop Alpha, as it's presented in the whitepaper. Their design could change radically before deployment.) If you're planning on building a closed loop out of steel, and there's nowhere for the steel to go when it expands in summer, the plan may need some rethinking. The best I can think of is some kind of inner lining, so that it has a segmented hull, like a caterpillar: https://www.google.com/search?q=caterpillar&tbm=isch https://www.google.com/search?q=caterpillar&tbm=isch But it would need to be very strong lining in order to prevent any leaks between the segments. And any kind of a leak would need to be detectable and would shut down the hyperloop until it's resolved. Between the wildly optimistic cost projections and the fundamental engineering difficulties, I'm much more inclined to call it a pipe dream than a perhaps-future-possibility.
  - vidarh 12y ago
    See my comment above - the expansion is specifically addressed. If you're going to criticize it, at least read the full whitepaper first. > But it would need to be very strong lining in order to prevent any leaks between the segments. The entire point of not requiring vacuum is to avoid having nearly as strict tolerances for leaks.
    - sillysaurus3 12y ago
      It's a "reduced-pressure tube." A leak is still a big deal, isn't it? Regardless, the core structural engineering is the focus of the criticism, not whether it might leak. Also, since Space X's whole point is to compete on cost savings, it was a little strange to hear cost projections that were so optimistic.
      - 12y ago
vidarh 12y ago
> The steel expands in summer due to heat. Where does it go? Roads can expand using those interlocking teeth things, but hyperloop has to remain a closed system. Feel free to disagree with whether or not the approach outlined is feasible, but this is specifically covered in the whitepaper. See page 5, section "Earthquakes and expansion joints" as well as page 28, section 4.2.3 "Pylons and tunnels".
- sillysaurus3 12y ago
  To clarify, tlb's comment was in direct response to the Hyperloop Alpha whitepaper: https://news.ycombinator.com/item?id=6201728#up_6202327 https://news.ycombinator.com/item?id=6201728#up_6202327 He doesn't properly address thermal expansion of the entire system. A long straight steel tube from SF to LA will expand a total of 300 meters over a 40C temperature change. Where does it go?
  - vidarh 12y ago
    And my response is the same: See those sections.
    - sillysaurus3 12y ago
      Sure, let's go over it together. Tlb is many things, but "rarely wrong" is probably near the top of the list. He certainly read those sections before making that comment, so there must be something here which made him as an engineering expert say that it doesn't properly address thermal expansion. I'll try to run an emulator of tlb's mind, but mine is far less sharp. The tube will be supported by pillars which constrain the tube in the vertical direction but allow longitudinal slip for thermal expansion as well as dampened lateral slip to reduce the risk posed by earthquakes. In addition, the pillar to tube connection nominal position will be adjustable vertically and laterally to ensure proper alignment despite possible ground settling. These minimally constrained pillars to tube joints will also allow a smoother ride. Specially designed slip joints at stations will be able to take any tube length variance due to thermal expansion. This is an ideal location for the thermal expansion joints as the speed is much lower nearby the stations. It thus allows the tube to be smooth and welded along the high speed gliding middle section. This seems like the key sentence: Specially designed slip joints at stations will be able to take any tube length variance due to thermal expansion. There are two stations, one in SF and one in LA: http://i.imgur.com/3TavjCY.png http://i.imgur.com/3TavjCY.png (For simplicity, let's assume it's just the main route.) That would mean each station needs to absorb 150 meters of thermal expansion. (Would anyone mind double-checking that tlb's calculation is correct?) So it looks like the tube is resting on these things: http://i.imgur.com/srQjmps.png http://i.imgur.com/srQjmps.png and the plan is for the tube to expand due to heat, and the expansion will be absorbed at the two stations at the end. Is that really feasible, especially given that different points along the route could have temperature differences? I drove along Highway 1 and saw how incredibly different the weather can get, and while that's south of where the route is planned, it's easy to imagine that part of the tube could be roasting in direct sunlight while the other is cooled by rain. Something like 90 degrees F at one part vs 70F at another part. That's a difference of 32.22C to 21.11C, or a total temperature difference of 11.11C. The route from SF to LA is about 350 miles. If a tube of that length expands 300 meters, then we can divide 300 meters by 350 miles to get the total expansion over a single mile. So a variation of 40C would give an expansion of 0.85 meters within a single mile. Since the variation in that scenario would be ~11C, multiplying the expansion by 11C/40C equals an expansion of 0.235 meters. So I suppose the question is: Is it feasible for those things the tube is resting on to absorb a quarter meter of expansion without that expansion being pushed all the way up to the station? It's the temperature differential along the route that seems to matter, not necessarily the difference from summer to winter. Judging by this screenshot: http://i.imgur.com/wgUJqWr.png http://i.imgur.com/wgUJqWr.png ... it seems like an expansion of 0.25 meters might be a big deal. But I don't know what I'm talking about. Is all of that about right so far? I'd also be curious whether the thermal expansion results in the tube becoming bigger in the circular direction, like a bigger "O", or if it expands parallel to the tube, like becoming a longer tube. Or even both. It seems like the plan addresses this with the first part of that paragraph: The tube will be supported by pillars which constrain the tube in the vertical direction but allow longitudinal slip for thermal expansion as well as dampened lateral slip to reduce the risk posed by earthquakes. In addition, the pillar to tube connection nominal position will be adjustable vertically and laterally to ensure proper alignment despite possible ground settling. But again, where precisely does 0.25m of steel go? I'm having trouble visualizing how the pillars could "allow for 0.25m of longitudinal slip over 1 mile." I realize that a temperature variation of about 10C over 1 mile is a little extreme, but we should examine how the system handles extreme situations.
Crito 12y ago
Just let it bow up and down when it expands, and call it a rollercoaster. ;)
reneherse 12y ago
Humans have been engineering expansion joints for various types of continuous structures for well over a hundred years, including sealed pipelines. The new design requirements and constraints posed by the Hyper Loop concept just increase the complexity of the problem. Certain engineers love this kind of challenge.
dredmorbius 12y ago
There was a 1970s proposal for an underground tunneled very-high-speed transport quite similar to the hyperloop. Partially-evacuated tubes, relatively small vehicles. Cost and other considerations torpedoed it. Look up R.M. Salter at RAND: "The Very High Speed Transit System" (August, 1972) "Trans-Planetary Subway Systems -- A Burgeoning Capability" (February, 1978) http://www.rand.org/pubs/papers/P4874.html http://www.rand.org/pubs/papers/P4874.html http://www.rand.org/content/dam/rand/pubs/papers/2008/P4874.pdf http://www.rand.org/content/dam/rand/pubs/papers/2008/P4874.... http://www.rand.org/pubs/papers/P6092.html http://www.rand.org/pubs/papers/P6092.html http://www.rand.org/content/dam/rand/pubs/papers/2009/P6092.pdf http://www.rand.org/content/dam/rand/pubs/papers/2009/P6092.... Similar / more: http://en.academic.ru/dic.nsf/enwiki/6107059 http://en.academic.ru/dic.nsf/enwiki/6107059
catshirt 12y ago
of course a profound technical concept will provoke questions regarding its technical feasibility. so what is your point? that it's impossible? that it shouldn't be attempted? that it's not a problem worth working through? "naysaying" doesn't mean "saying no". "naysaying" is the inability to see a little further into the future based on the knowledge we have today. > "The steel expands in summer due to heat. Where does it go?" a cliche example but- i'd love to be the anachronistic fly on the wall listening to all the "where will the hot metal go???" people talking to the Wright brothers.

mcdonji 12y ago

It seems to me Musk was attempting to get the people who should be pushing bold new ideas to do so. The Hyperloop idea might have been premature but it certainly engaged people in discussing radical new ideas rather than discussing minor tweaks to an existing concept. That general thought is imbued in the culture of the companies he is involved with.