4 ms·

Yes but maintaining a vacuum over long distances is a huge challenge.

paulmd 9y ago
Any public information on what Musk thinks he can get the leakage rates to? I assume the metric here would be something like cubic-yards-per-mile-per-day or something like that.
- grkvlt 9y ago
  Or acres per fortnight, perhaps?
Xeoncross 9y ago
I'll say, mine always gets caught going around corners or on chairs...
Obi_Juan_Kenobi 9y ago
It's a 'soft' vacuum, so doesn't have anywhere near the difficulty of a 'hard' vacuum. IIRC the detailed specs of what they intend to do aren't out, so it's all just speculation.
guimarin 9y ago
This might be a case where no one has actually tried it with a maker mentality. Musk was saying the other day that you need 1 atmosphere of pressure capability to create a vacuum, but 5-6 to hold back the watertable related to his tunneling network. Seems like from a first principles perspective making a vacuum should be much easier than an underwater tunnel. I'm guessing that you could create a partial vacuum in such a tunnel fairly easily. But I haven't 'done it' and that's the rub.
- murbard2 9y ago
  I don't think the problem is the pressure - holding up one atmosphere is not big deal - I think it's the porosity. It just takes one hole, anywhere, and pscchht you start losing your vaccum. You have to continuously run pumps to get rid of the air that finds its way in, and their efficiency is inversely proportional to the pressure difference.
  - Robotbeat 9y ago
    This is also true of below-water-table tunnels and pipelines of various sort, which are often at much higher pressure and with much greater environmental risk.
    - AstralStorm 9y ago
      It is quite a bit easier to hold back a liquid than a gas. Different minimum pore size and you get hydrophobic chemistry and surface tension on your side. Especially at such big pipe diameters as required. You can use cheap materials like modified concrete to patch a hole in an underwater tunnel, not so in a vacuum tube - that needs something much better and more expensive.
      - Robotbeat 9y ago
        Not true. You can use concrete to hold back a vacuum and cheap materials like a thin polymer coating, too. Remember, Hyperloop does not require an ultra hard vacuum.

Any public information on what Musk thinks he can get the leakage rates to? I assume the metric here would be something like cubic-yards-per-mile-per-day or something like that.

grkvlt 9y ago
Or acres per fortnight, perhaps?

Xeoncross 9y ago

I'll say, mine always gets caught going around corners or on chairs...

Obi_Juan_Kenobi 9y ago

It's a 'soft' vacuum, so doesn't have anywhere near the difficulty of a 'hard' vacuum. IIRC the detailed specs of what they intend to do aren't out, so it's all just speculation.

guimarin 9y ago

This might be a case where no one has actually tried it with a maker mentality. Musk was saying the other day that you need 1 atmosphere of pressure capability to create a vacuum, but 5-6 to hold back the watertable related to his tunneling network. Seems like from a first principles perspective making a vacuum should be much easier than an underwater tunnel. I'm guessing that you could create a partial vacuum in such a tunnel fairly easily. But I haven't 'done it' and that's the rub.

murbard2 9y ago
I don't think the problem is the pressure - holding up one atmosphere is not big deal - I think it's the porosity. It just takes one hole, anywhere, and pscchht you start losing your vaccum. You have to continuously run pumps to get rid of the air that finds its way in, and their efficiency is inversely proportional to the pressure difference.
- Robotbeat 9y ago
  This is also true of below-water-table tunnels and pipelines of various sort, which are often at much higher pressure and with much greater environmental risk.
  - AstralStorm 9y ago
    It is quite a bit easier to hold back a liquid than a gas. Different minimum pore size and you get hydrophobic chemistry and surface tension on your side. Especially at such big pipe diameters as required. You can use cheap materials like modified concrete to patch a hole in an underwater tunnel, not so in a vacuum tube - that needs something much better and more expensive.
    - Robotbeat 9y ago
      Not true. You can use concrete to hold back a vacuum and cheap materials like a thin polymer coating, too. Remember, Hyperloop does not require an ultra hard vacuum.