8 ms·

I dunno, after watching thunderf00t's video on hyperloops, I'm pretty convinced that there are fundamental engineering barriers that would have doomed the compa

by ythl 10y ago

I dunno, after watching thunderf00t's video on hyperloops, I'm pretty convinced that there are fundamental engineering barriers that would have doomed the company anyway. If not internal squabbles and lawsuits, the practical laws of nature would eventually have to be reckoned with (just like with Solar Freakin Roadways)

schiffern 10y ago
Thunderf00t's objections are mostly based on misunderstandings of fluid dynamics and the hyperloop design. It's almost impressive -- he's singlehandedly founded a whole raft of hyperloop engineering myths with one "controversial" video. There would be no sonic "shock wave" killing everyone in the tube in the event of a breach. Viscous drag on the tube walls would reduce the flow velocity to highway speed in only a couple km. The wave front spreads out, becoming a gradual pressure rise. The entire tube would be designed for rapid repressurization (under 60 seconds). The cars can easily stop in 15-20 seconds since the passengers are strapped in and possibly in seats facing backward to arrest braking forces. Expansion joints are easily accommodated at the end stations, and the slight leaks from the sliding interfaces are compensated by mechanical pumps (easy to maintain 1/1000th of an atmosphere, damn near impossible to maintain 1/1000000 of an atmosphere for true vac trains given the linear decrease in vacuum pumping mass flow at low pressures and the need for turbomolucular pumps and/or cryopumps at those pressures). There's a great need for pumping near the end stations anyway due to residual air entering around the pod in the airlock. They'll pump down the majority of the pressure of course, but due to the exponential drop in pumping speed over time it makes little sense to make passengers wait a long time and pump it down to the exact same pressure when they can cut it off early and just let the tube pumps make it up. Even on the space station (where air is very expensive) they only pump the airlock down part-way and vent the remaining residual atmosphere so the astronauts (whose time is also expensive) don't have to wait.
- dougmany 10y ago
  What convinced that it would not work was reading about the temperature pressure differences the on car motor was supposed to handle. It sounds like there needs to be a giant air compressor strapped to the car. Having been in a garage when an air compressor turns on (unpleasant), I really don't want to be in a tiny metal tube with a giant air compressor on all the time. It sounds several times worse then being in an airplane.
  - schiffern 10y ago
    The compressor in your garage is almost certainly a reciprocating compressor (oscillating motion = very loud), while the hyperloop uses an axial compressor (pure rotary motion = much quieter). The same sound absorbing layers and vibration isolation technology that's used on jet planes could also be used if needed.
Vexs 10y ago
Just out of curiosity, what are the issues it has?
- kennell 10y ago
  The video he is refering to: https://www.youtube.com/watch?v=RNFesa01llk https://www.youtube.com/watch?v=RNFesa01llk
  - thringsaround 10y ago
    I know it's a sensitive subject for HN, but I'll go ahead and encourage folks not to watch that video, at least without taking a look at some of the other popular videos on that channel (https://www.youtube.com/channel/UCmb8hO2ilV9vRa8cilis88A https://www.youtube.com/channel/UCmb8hO2ilV9vRa8cilis88A) and making an informed decision. To be clear, since technical expertise and regressive politics are not necessarily mutually exclusive, I'm not saying that you shouldn't watch it-- just that you might not want to.
    - jshevek 10y ago
      What could be more regressive than ignoring one side of an engineering debate because that speaker doesn't agree with your politics?
      - deleted 10y ago
        [deleted]
      - thringsaround 10y ago
        Snarky reply replaced: I'm sincerely curious if that's really all you're taking away from my comment, including the explicit disclaimer. My advice was to pay closer attention to the material, not to ignore it, so I'm perplexed as to how you managed to get the complete opposite message. This seems exceptionally straightforward to me, so I'll make it as un-political as I can: There are lifetimes of new content available for your consumption every single day. Maybe it's not all worthwhile. Maybe not 1% of it is. It doesn't matter-- you'll never get to see an infinitesimal fraction of it, even just the good, true, accurate stuff. So how do you decide what to pay attention to with your mortal lifespan? Just as a first pass, I like to use filters like "is this notably excellent" or "does this make me want to throw up at all, even just a little". Then if it's not excellent, or if the speaker doesn't agree with my politics, or especially both, I don't feel any remorse whatsoever about skipping it. This isn't about shutting myself off. I think it's very important to expose myself to perspectives that differ from my own, to broaden my own frame of reference. I also think that feces play a critically important role in my metabolism, but that doesn't mean I'm excited to open a box of donuts and discover a frosted turd. And I'll accept exactly 0 concern trolling around my publicly saying, just, hey... look in the box. If it's a turd in there, you don't still have to eat it.
valarauca1 10y ago
Maybe it's just me but I'm more tempted to trust engineers who's day-to-day job is engineering rather then a Youtuber who replaces vowels with letters. But strawman/direct attacks aside. In my experience when one engineer is disagreeing with a team of engineers, they're wrong or the team a fundamental misunderstanding of the problem they're working to solve.
- throw1291121 10y ago
  What about the guy who warned about the space shuttle's O-rings? And that is an example from a conservative environment. Now take startups that just want VC money with no intention of producing a product, a team of engineers that likes their salaries and you'll get a fake consensus very easily.
  - Bjartr 10y ago
    That was one engineer disagreeing with a team of managers.
- jshevek 10y ago
  > I'm more tempted to trust engineers who's day-to-day job is engineering rather then a Youtuber who ... Even if those engineers clearly have a financial incentive to make biased claims?
  - valarauca1 10y ago
    I mean if we toss around incentived claims then you can't trust literally anyone in a capitalist society. Since they can be incentived to lie to you, and you have to do due diligence to prove they aren't before trusting them. This defense is the home of conspiracy theorists and crazy people. If you are really concerned with this why are you posting on a forum literally owned by a SV Billionaire? Buts let's pretend you are rational. How does a master in chemistry grant you knowledge of mechanical, structural, and fluid engineering. If you say they're both Math/STEM fields, then why aren't chemistry professors, and comsologist certified electricians? It's related by the same logic.
jshevek 10y ago
Maybe I'm mis-remembering, but I don't recall Thunderf00t's video suggesting that the hyperloop was truly as absurd as, say, the idea of using solar roadways to melt snow off the road. I thought that his main message was that people are over-selling the feasibility of the hyperloop and playing down the incredible engineering challenges and dangers.

by ythl 10y ago

schiffern 10y ago

Thunderf00t's objections are mostly based on misunderstandings of fluid dynamics and the hyperloop design. It's almost impressive -- he's singlehandedly founded a whole raft of hyperloop engineering myths with one "controversial" video. There would be no sonic "shock wave" killing everyone in the tube in the event of a breach. Viscous drag on the tube walls would reduce the flow velocity to highway speed in only a couple km. The wave front spreads out, becoming a gradual pressure rise. The entire tube would be designed for rapid repressurization (under 60 seconds). The cars can easily stop in 15-20 seconds since the passengers are strapped in and possibly in seats facing backward to arrest braking forces. Expansion joints are easily accommodated at the end stations, and the slight leaks from the sliding interfaces are compensated by mechanical pumps (easy to maintain 1/1000th of an atmosphere, damn near impossible to maintain 1/1000000 of an atmosphere for true vac trains given the linear decrease in vacuum pumping mass flow at low pressures and the need for turbomolucular pumps and/or cryopumps at those pressures). There's a great need for pumping near the end stations anyway due to residual air entering around the pod in the airlock. They'll pump down the majority of the pressure of course, but due to the exponential drop in pumping speed over time it makes little sense to make passengers wait a long time and pump it down to the exact same pressure when they can cut it off early and just let the tube pumps make it up. Even on the space station (where air is very expensive) they only pump the airlock down part-way and vent the remaining residual atmosphere so the astronauts (whose time is also expensive) don't have to wait.

dougmany 10y ago
What convinced that it would not work was reading about the temperature pressure differences the on car motor was supposed to handle. It sounds like there needs to be a giant air compressor strapped to the car. Having been in a garage when an air compressor turns on (unpleasant), I really don't want to be in a tiny metal tube with a giant air compressor on all the time. It sounds several times worse then being in an airplane.
- schiffern 10y ago
  The compressor in your garage is almost certainly a reciprocating compressor (oscillating motion = very loud), while the hyperloop uses an axial compressor (pure rotary motion = much quieter). The same sound absorbing layers and vibration isolation technology that's used on jet planes could also be used if needed.

Vexs 10y ago

Just out of curiosity, what are the issues it has?

kennell 10y ago
The video he is refering to: https://www.youtube.com/watch?v=RNFesa01llk https://www.youtube.com/watch?v=RNFesa01llk
- thringsaround 10y ago
  I know it's a sensitive subject for HN, but I'll go ahead and encourage folks not to watch that video, at least without taking a look at some of the other popular videos on that channel (https://www.youtube.com/channel/UCmb8hO2ilV9vRa8cilis88A https://www.youtube.com/channel/UCmb8hO2ilV9vRa8cilis88A) and making an informed decision. To be clear, since technical expertise and regressive politics are not necessarily mutually exclusive, I'm not saying that you shouldn't watch it-- just that you might not want to.
  - jshevek 10y ago
    What could be more regressive than ignoring one side of an engineering debate because that speaker doesn't agree with your politics?
    - deleted 10y ago
      [deleted]
    - thringsaround 10y ago
      Snarky reply replaced: I'm sincerely curious if that's really all you're taking away from my comment, including the explicit disclaimer. My advice was to pay closer attention to the material, not to ignore it, so I'm perplexed as to how you managed to get the complete opposite message. This seems exceptionally straightforward to me, so I'll make it as un-political as I can: There are lifetimes of new content available for your consumption every single day. Maybe it's not all worthwhile. Maybe not 1% of it is. It doesn't matter-- you'll never get to see an infinitesimal fraction of it, even just the good, true, accurate stuff. So how do you decide what to pay attention to with your mortal lifespan? Just as a first pass, I like to use filters like "is this notably excellent" or "does this make me want to throw up at all, even just a little". Then if it's not excellent, or if the speaker doesn't agree with my politics, or especially both, I don't feel any remorse whatsoever about skipping it. This isn't about shutting myself off. I think it's very important to expose myself to perspectives that differ from my own, to broaden my own frame of reference. I also think that feces play a critically important role in my metabolism, but that doesn't mean I'm excited to open a box of donuts and discover a frosted turd. And I'll accept exactly 0 concern trolling around my publicly saying, just, hey... look in the box. If it's a turd in there, you don't still have to eat it.

valarauca1 10y ago

Maybe it's just me but I'm more tempted to trust engineers who's day-to-day job is engineering rather then a Youtuber who replaces vowels with letters. But strawman/direct attacks aside. In my experience when one engineer is disagreeing with a team of engineers, they're wrong or the team a fundamental misunderstanding of the problem they're working to solve.

throw1291121 10y ago
What about the guy who warned about the space shuttle's O-rings? And that is an example from a conservative environment. Now take startups that just want VC money with no intention of producing a product, a team of engineers that likes their salaries and you'll get a fake consensus very easily.
- Bjartr 10y ago
  That was one engineer disagreeing with a team of managers.
jshevek 10y ago
> I'm more tempted to trust engineers who's day-to-day job is engineering rather then a Youtuber who ... Even if those engineers clearly have a financial incentive to make biased claims?
- valarauca1 10y ago
  I mean if we toss around incentived claims then you can't trust literally anyone in a capitalist society. Since they can be incentived to lie to you, and you have to do due diligence to prove they aren't before trusting them. This defense is the home of conspiracy theorists and crazy people. If you are really concerned with this why are you posting on a forum literally owned by a SV Billionaire? Buts let's pretend you are rational. How does a master in chemistry grant you knowledge of mechanical, structural, and fluid engineering. If you say they're both Math/STEM fields, then why aren't chemistry professors, and comsologist certified electricians? It's related by the same logic.

jshevek 10y ago

Maybe I'm mis-remembering, but I don't recall Thunderf00t's video suggesting that the hyperloop was truly as absurd as, say, the idea of using solar roadways to melt snow off the road. I thought that his main message was that people are over-selling the feasibility of the hyperloop and playing down the incredible engineering challenges and dangers.