4 ms·

And is that strength enough to put vacuum airships back on the menu?

by kardos 5y ago

solarmist 5y ago
I'm intrigued. What's a vacuum airship?
- kardos 5y ago
  https://en.m.wikipedia.org/wiki/Vacuum_airship https://en.m.wikipedia.org/wiki/Vacuum_airship Like a blimp but with a rigid balloon filled (ha ha) with vacuum instead of a light gas. The article is saying it's a polymer so I'm guessing it doesn't have the right rigidity, ie, the stronger than steel bit must be with respect to a different strength measure
  - solarmist 5y ago
    ....wow, that is the most counter-intuitive idea I've seen in a long time! A helium balloon makes sense, it's lighter than air so it floats, duh. Well, what's lighter than that? Nothing (vacuum)! It's such a dumb, but correct answer that I had a hard time wrapping my head around it. Yup, theoretically a vacuum would be extremely buoyant if we could put it in a light enough structure.
    - kardos 5y ago
      Yeah it's nifty idea -- no need for explosive hydrogen or scarce helium. If the polymer sheet is strong enough, I wonder if one could use it to wrap a sort of scaffolding (a shape like https://en.wikipedia.org/wiki/Fullerene https://en.wikipedia.org/wiki/Fullerene but perhaps with struts through the interior for more strength), then evacuate the air from the interior in order to form a lighter-than-air "box". Submarines can withstand a few dozen atmospheres of pressure, this would have to withstand .. one, I suppose, so intuitively it seems plausible.
    - toss1 5y ago
      >>if we could put it in a light enough structure And there's the problem. Containing a gas with pressure equivalent to the outside air requires just a membrane. Storing a vacuum requires a container that can resist external pressure of ~ 14 psi. It scales very badly. This also creates an insane amount of stored energy in the stress on the shell. Here's a couple of videos of vacuum crushing steel tanker railroad cars [0] [1]. Of course that size doesn't even begin to scale up to the level of vacuum that would be required to buoyancy in the earth's atmosphere. [0] https://www.youtube.com/watch?v=VS6IckF1CM0 https://www.youtube.com/watch?v=VS6IckF1CM0 [1] https://www.youtube.com/watch?v=yBq5uapC-e0 https://www.youtube.com/watch?v=yBq5uapC-e0 I'd think the only way to do it might be to have many small hollow spheres contained in a net or something, but the trick would be for each one to be light enough to be positively buoyant...
hrjet 5y ago
I would be also interested in mini vacuum packets, that one could strap to their car or backpack, and make it a touch lighter. Just imagine the energy savings!

And is that strength enough to put vacuum airships back on the menu?

by kardos 5y ago

And is that strength enough to put vacuum airships back on the menu?

solarmist 5y ago

I'm intrigued. What's a vacuum airship?

kardos 5y ago
https://en.m.wikipedia.org/wiki/Vacuum_airship https://en.m.wikipedia.org/wiki/Vacuum_airship Like a blimp but with a rigid balloon filled (ha ha) with vacuum instead of a light gas. The article is saying it's a polymer so I'm guessing it doesn't have the right rigidity, ie, the stronger than steel bit must be with respect to a different strength measure
- solarmist 5y ago
  ....wow, that is the most counter-intuitive idea I've seen in a long time! A helium balloon makes sense, it's lighter than air so it floats, duh. Well, what's lighter than that? Nothing (vacuum)! It's such a dumb, but correct answer that I had a hard time wrapping my head around it. Yup, theoretically a vacuum would be extremely buoyant if we could put it in a light enough structure.
  - kardos 5y ago
    Yeah it's nifty idea -- no need for explosive hydrogen or scarce helium. If the polymer sheet is strong enough, I wonder if one could use it to wrap a sort of scaffolding (a shape like https://en.wikipedia.org/wiki/Fullerene https://en.wikipedia.org/wiki/Fullerene but perhaps with struts through the interior for more strength), then evacuate the air from the interior in order to form a lighter-than-air "box". Submarines can withstand a few dozen atmospheres of pressure, this would have to withstand .. one, I suppose, so intuitively it seems plausible.
  - toss1 5y ago
    >>if we could put it in a light enough structure And there's the problem. Containing a gas with pressure equivalent to the outside air requires just a membrane. Storing a vacuum requires a container that can resist external pressure of ~ 14 psi. It scales very badly. This also creates an insane amount of stored energy in the stress on the shell. Here's a couple of videos of vacuum crushing steel tanker railroad cars [0] [1]. Of course that size doesn't even begin to scale up to the level of vacuum that would be required to buoyancy in the earth's atmosphere. [0] https://www.youtube.com/watch?v=VS6IckF1CM0 https://www.youtube.com/watch?v=VS6IckF1CM0 [1] https://www.youtube.com/watch?v=yBq5uapC-e0 https://www.youtube.com/watch?v=yBq5uapC-e0 I'd think the only way to do it might be to have many small hollow spheres contained in a net or something, but the trick would be for each one to be light enough to be positively buoyant...

hrjet 5y ago

I would be also interested in mini vacuum packets, that one could strap to their car or backpack, and make it a touch lighter. Just imagine the energy savings!