5 ms·

TGV runs very well, except for the weekly labor dispute that's completely orthogonal to the fact that it's not running in a vacuum. How you people believe the

TGV runs very well, except for the weekly labor dispute that's completely orthogonal to the fact that it's not running in a vacuum. How you people believe the risk of explosive decompression will solve whatever problems a minority of high speed train systems have is beyond me.

j-pb 6y ago
1 bar is acutally not that bad. Hyoerloop pods are smaller, so less lives are at risk. And most importantly of all. It's not gonna be explosive, unless you rip the thing open with a bomb and you're right next to it. Even if you rip the tube in half, the air is going to take some time to fill it up. A few miles from the hole there will be a much more harmless pressure gradient already. Sure it might shake your capsule, but you're not gonna get shredded.
- jankotek 6y ago
  Pressure wave moves at speed of sound. Lightweigh capsule gets destroyed just by derailing at 500mph. Any bad event will put down ALL trains on track. And rescuing people trapped in 100 miles long steel pipe... Hyperloop is a nightmare!
  - j-pb 6y ago
    See my above reply. Speed of sound doesn't mean much if there is a constantly softening gradient. https://en.m.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equation#Poiseuille's_equation_for_an_ideal_isothermal_gas https://en.m.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equ... Edit: To give a good analogy: Electricity also travels at the speed of light through a cable, however due to resistance you will get different current reading depending on where you measure.
- tjpnz 6y ago
  >And most importantly of all. It's not gonna be explosive, unless you rip the thing open with a bomb and you're right next to it. And that's precisely what makes it unworkable with regards to safety. Burying the tubes is an option but by that point you would be looking at rail instead.
  - j-pb 6y ago
    Ok so somebody attacks it, with explosives. And manages to time them well enough that they go off right next to a cart, or inside one. They will get 1 passenger car. Which is what? 8 People? The tube will slowly fill with air, everybody else evacuates safely at a slower speed. I'm willing to bet on those odds. Compared to the number of car accidents, it'a a no brainer.
- himinlomax 6y ago
  > 1 bar is acutally not that bad. That does not mean anything. The weight of a 1 cm² column of air is 1 kg. So 1 ton for 1 m². Let's say a square profile hyperloop tunnel 1 m high decompressing will be the equivalent of dropping one tonne for each meter. The shock will propagate at the speed of sound.
  - j-pb 6y ago
    You neglect the friction that even laminar flow would experience while flowing into the tube. If you make small fins at the top of the tube you can even exagerate the effect and introduce turbulence, which further reduces flow rate. There is a reason why pipelines need pumping stations every couple miles, to keep the fluid at speed. Sure the wave might propagate at the speed of sound but that doesn't matter much if its pressure gradient is slow enough. https://en.m.wikipedia.org/wiki/Hagen–Poiseuille_equation#Poiseuille's_equation_for_an_ideal_isothermal_gas https://en.m.wikipedia.org/wiki/Hagen–Poiseuille_equation#Po... Edit: To give a good analogy: Electricity also travels at the speed of light through a cable, however due to resistance you will get different current reading depending on where you measure. Edit2: I reread your argument, and there is also a flaw in your energy calculation. The energy per time is not proportional to the length of the tunnel, but proportional to the size of the inlet. Your calculation would be if you remove the entire top of the tunnel at once, over it's entire length.
    - himinlomax 6y ago
      Turbulence in a near vacuum? I'm more than rusty on my statistical mechanics, but what you describe will only matter long after most of the potential energy has done its damage.
      - j-pb 6y ago
        Don't look at the wavefront of the first 100m, the pod there is gone anyways in case of a bomb. Turbulence on the phase of what comes after the near vacuum. The plug essentially plugs itself from resticted airflow. If you want to be extra safe you could even add small tesla valve style fins around the border of the tube, to increase turbulence.

j-pb 6y ago

1 bar is acutally not that bad. Hyoerloop pods are smaller, so less lives are at risk. And most importantly of all. It's not gonna be explosive, unless you rip the thing open with a bomb and you're right next to it. Even if you rip the tube in half, the air is going to take some time to fill it up. A few miles from the hole there will be a much more harmless pressure gradient already. Sure it might shake your capsule, but you're not gonna get shredded.

jankotek 6y ago
Pressure wave moves at speed of sound. Lightweigh capsule gets destroyed just by derailing at 500mph. Any bad event will put down ALL trains on track. And rescuing people trapped in 100 miles long steel pipe... Hyperloop is a nightmare!
- j-pb 6y ago
  See my above reply. Speed of sound doesn't mean much if there is a constantly softening gradient. https://en.m.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equation#Poiseuille's_equation_for_an_ideal_isothermal_gas https://en.m.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equ... Edit: To give a good analogy: Electricity also travels at the speed of light through a cable, however due to resistance you will get different current reading depending on where you measure.
tjpnz 6y ago
>And most importantly of all. It's not gonna be explosive, unless you rip the thing open with a bomb and you're right next to it. And that's precisely what makes it unworkable with regards to safety. Burying the tubes is an option but by that point you would be looking at rail instead.
- j-pb 6y ago
  Ok so somebody attacks it, with explosives. And manages to time them well enough that they go off right next to a cart, or inside one. They will get 1 passenger car. Which is what? 8 People? The tube will slowly fill with air, everybody else evacuates safely at a slower speed. I'm willing to bet on those odds. Compared to the number of car accidents, it'a a no brainer.
himinlomax 6y ago
> 1 bar is acutally not that bad. That does not mean anything. The weight of a 1 cm² column of air is 1 kg. So 1 ton for 1 m². Let's say a square profile hyperloop tunnel 1 m high decompressing will be the equivalent of dropping one tonne for each meter. The shock will propagate at the speed of sound.
- j-pb 6y ago
  You neglect the friction that even laminar flow would experience while flowing into the tube. If you make small fins at the top of the tube you can even exagerate the effect and introduce turbulence, which further reduces flow rate. There is a reason why pipelines need pumping stations every couple miles, to keep the fluid at speed. Sure the wave might propagate at the speed of sound but that doesn't matter much if its pressure gradient is slow enough. https://en.m.wikipedia.org/wiki/Hagen–Poiseuille_equation#Poiseuille's_equation_for_an_ideal_isothermal_gas https://en.m.wikipedia.org/wiki/Hagen–Poiseuille_equation#Po... Edit: To give a good analogy: Electricity also travels at the speed of light through a cable, however due to resistance you will get different current reading depending on where you measure. Edit2: I reread your argument, and there is also a flaw in your energy calculation. The energy per time is not proportional to the length of the tunnel, but proportional to the size of the inlet. Your calculation would be if you remove the entire top of the tunnel at once, over it's entire length.
  - himinlomax 6y ago
    Turbulence in a near vacuum? I'm more than rusty on my statistical mechanics, but what you describe will only matter long after most of the potential energy has done its damage.
    - j-pb 6y ago
      Don't look at the wavefront of the first 100m, the pod there is gone anyways in case of a bomb. Turbulence on the phase of what comes after the near vacuum. The plug essentially plugs itself from resticted airflow. If you want to be extra safe you could even add small tesla valve style fins around the border of the tube, to increase turbulence.