6 ms·

> Can you imagine traveling that way? Plenty of people can imagine it because they travel that way every day. Trains all over Asia and Europe reach those spee

> Can you imagine traveling that way? Plenty of people can imagine it because they travel that way every day. Trains all over Asia and Europe reach those speeds and faster.

yorwba 9y ago
Maybe I have been taking the wrong trains (in Germany), but 200 mph (321 km/h) seems plenty fast to me. That's higher than the maximum speed of most of Deutsche Bahn's high-speed trains: https://en.wikipedia.org/wiki/Intercity-Express https://en.wikipedia.org/wiki/Intercity-Express Even those that can go faster than 300 km/h tend to do so only on very short legs, because they need long straight stretches to stay on track and have to accelerate/decelerate at the ends as well.
- adrianN 9y ago
  Hyperloops would also have those constraints on track layout.
  - stevep98 9y ago
    I think this is another reason why musk is getting into tunneling. Reducing the cost of tunnels lets you place the hyperloop track in a more optimal location.
    - convolvatron 9y ago
      would you still use a steel containment pipe? poured cement seems like it would be cheaper, but every example I've seen develops cracks and starts letting in water.
- _Codemonkeyism 9y ago
  Real high speed in Germany does not make sense, too many stops due to political reasons ("Wolfsburg" comes to mind and "Kassel"). That's the reason new ICE trains are slower than their predecessors. Other countries have far fewer stops on high speed routes and can therefor have faster trains (e.g. Japan and France).
- xU1ppskunDmy6oz 9y ago
  Distances in China are enormous compared to those within Germany. Japan is in the convenient situation of being rather long and slim so that its railway network is almost 1D rather than 2D. So their settings are quite different. Note how the ICE 3 operates at 320km/h and the ICE 4 only goes up to 230km/h. I would assume they’re optimising for efficiency now.
- qntty 9y ago
  https://en.wikipedia.org/wiki/Siemens_Velaro https://en.wikipedia.org/wiki/Siemens_Velaro
alacombe 9y ago
Not in a 10ft wide, hundreds of miles long tunnel; this is making a big difference.
- Robotbeat 9y ago
  There are ~5ft diameter natural gas pipelines operating at high pressure (>1000psi) that are thousands of miles long: https://en.wikipedia.org/wiki/Yamal-Europe_pipeline https://en.wikipedia.org/wiki/Yamal-Europe_pipeline You could fit a hyperloop pod in one of those, just seat single-file. Larger diameter is optimal since you can get by with a lower pressure, but we're in the ballpark here already.
  - stevep98 9y ago
    In a gas pipeline, the high pressures help to stiffen the structure. In a hyperloop, you have very low pressure inside the pipe which changes the pipe design completely. https://youtu.be/T9bpUfWy8Wg?t=161 https://youtu.be/T9bpUfWy8Wg?t=161
    - Robotbeat 9y ago
      Certainly and good point, but vacuum is just -15psi while these gas pipelines are 1200psi, almost a factor of 100 greater. Simply the required thickness of metal for 1200psi may provide sufficient stiffness to withstand vacuum. In fact, let's do the math. For a typical carbon steel tensile strength of 370MPa, internal pressure of 1200psi with a factor of safety of 2, and a radius of 2.5ft, you'd need 3.4cm thick walls: 2.5ft/(370MPa/(2 * 1200psi)) in cm https://www.google.com/search?q=2.5ft/(370MPa/(2*1200psi) https://www.google.com/search?q=2.5ft/(370MPa/(2*1200psi)) According to this design guide for carbon steels, and using 30psi pressure differential for vacuum (i.e. a factor of safety of 2), we get: http://lss.fnal.gov/archive/test-tm/1000/fermilab-tm-1378.pdf http://lss.fnal.gov/archive/test-tm/1000/fermilab-tm-1378.pd... 1.2cm thick walls, which is much thinner than the gas pipeline. 5ft * ((1-.28^2) * 30psi/(2 * 30 * 10^6psi))^(1/3) in cm https://www.google.com/search?q=5ft*((1-.28^2)*30psi/(2*30*10^6psi))^(1/3) https://www.google.com/search?q=5ft*((1-.28^2)*30psi/(2*30*1... So those gas pipelines should already be plenty thick enough for vacuum service. My point stands.

> Can you imagine traveling that way? Plenty of people can imagine it because they travel that way every day. Trains all over Asia and Europe reach those speeds and faster.

yorwba 9y ago

Maybe I have been taking the wrong trains (in Germany), but 200 mph (321 km/h) seems plenty fast to me. That's higher than the maximum speed of most of Deutsche Bahn's high-speed trains: https://en.wikipedia.org/wiki/Intercity-Express https://en.wikipedia.org/wiki/Intercity-Express Even those that can go faster than 300 km/h tend to do so only on very short legs, because they need long straight stretches to stay on track and have to accelerate/decelerate at the ends as well.

adrianN 9y ago
Hyperloops would also have those constraints on track layout.
- stevep98 9y ago
  I think this is another reason why musk is getting into tunneling. Reducing the cost of tunnels lets you place the hyperloop track in a more optimal location.
  - convolvatron 9y ago
    would you still use a steel containment pipe? poured cement seems like it would be cheaper, but every example I've seen develops cracks and starts letting in water.
_Codemonkeyism 9y ago
Real high speed in Germany does not make sense, too many stops due to political reasons ("Wolfsburg" comes to mind and "Kassel"). That's the reason new ICE trains are slower than their predecessors. Other countries have far fewer stops on high speed routes and can therefor have faster trains (e.g. Japan and France).
xU1ppskunDmy6oz 9y ago
Distances in China are enormous compared to those within Germany. Japan is in the convenient situation of being rather long and slim so that its railway network is almost 1D rather than 2D. So their settings are quite different. Note how the ICE 3 operates at 320km/h and the ICE 4 only goes up to 230km/h. I would assume they’re optimising for efficiency now.
qntty 9y ago
https://en.wikipedia.org/wiki/Siemens_Velaro https://en.wikipedia.org/wiki/Siemens_Velaro

alacombe 9y ago

Not in a 10ft wide, hundreds of miles long tunnel; this is making a big difference.

Robotbeat 9y ago
There are ~5ft diameter natural gas pipelines operating at high pressure (>1000psi) that are thousands of miles long: https://en.wikipedia.org/wiki/Yamal-Europe_pipeline https://en.wikipedia.org/wiki/Yamal-Europe_pipeline You could fit a hyperloop pod in one of those, just seat single-file. Larger diameter is optimal since you can get by with a lower pressure, but we're in the ballpark here already.
- stevep98 9y ago
  In a gas pipeline, the high pressures help to stiffen the structure. In a hyperloop, you have very low pressure inside the pipe which changes the pipe design completely. https://youtu.be/T9bpUfWy8Wg?t=161 https://youtu.be/T9bpUfWy8Wg?t=161
  - Robotbeat 9y ago
    Certainly and good point, but vacuum is just -15psi while these gas pipelines are 1200psi, almost a factor of 100 greater. Simply the required thickness of metal for 1200psi may provide sufficient stiffness to withstand vacuum. In fact, let's do the math. For a typical carbon steel tensile strength of 370MPa, internal pressure of 1200psi with a factor of safety of 2, and a radius of 2.5ft, you'd need 3.4cm thick walls: 2.5ft/(370MPa/(2 * 1200psi)) in cm https://www.google.com/search?q=2.5ft/(370MPa/(2*1200psi) https://www.google.com/search?q=2.5ft/(370MPa/(2*1200psi)) According to this design guide for carbon steels, and using 30psi pressure differential for vacuum (i.e. a factor of safety of 2), we get: http://lss.fnal.gov/archive/test-tm/1000/fermilab-tm-1378.pdf http://lss.fnal.gov/archive/test-tm/1000/fermilab-tm-1378.pd... 1.2cm thick walls, which is much thinner than the gas pipeline. 5ft * ((1-.28^2) * 30psi/(2 * 30 * 10^6psi))^(1/3) in cm https://www.google.com/search?q=5ft*((1-.28^2)*30psi/(2*30*10^6psi))^(1/3) https://www.google.com/search?q=5ft*((1-.28^2)*30psi/(2*30*1... So those gas pipelines should already be plenty thick enough for vacuum service. My point stands.