3 ms·

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.

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.