Timeline for Is it possible to create a vacuum ballon using concentric partially pressured spheres?
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| Jul 16, 2013 at 12:17 | comment | added | akhmeteli | @Doug : I don't know what you mean by dynamic equilibrium in this case. You may read about buckling at en.wikipedia.org/wiki/Buckling . I am not saying I gave a solid proof. I gave some estimates that make me highly skeptical about your structure. I am afraid I don't have enough motivation to give an in-depth analysis of your structure. I hope you'll understand. | |
| Jul 15, 2013 at 13:53 | comment | added | Doug | I can see the basic point you're making; basically you're saying it's a dynamic equilibrium right? The pressure exerted on any shell is f(V,K) where V is the total volume of the structure and K is the number of shells, and the weight of the entire structure is f(V,K,M) where M is the material the shell is constructed of. You're positing that there's no M such that you can find values of V and K where the net volume of displaced air is > the total used mass. I'm not seeing this as a solid proof... I'm pretty sure you could find a very light, reasonably strong material that would do this. | |
| Jul 14, 2013 at 6:22 | comment | added | akhmeteli | @Doug: The force you are talking about is determined by P1-P2, so it is indeed related to both P1 and P2, and this difference must be less than the buckling critical pressure for the thin shell. So if you replace 1 homogeneous shell with 10 thinner shells with the same total mass, the pressure difference for each of them is roughly 10 times less than that for the initial shell, the thickness of each of them is roughly 10 times less than that of the initial shell, so the critical pressure for each of them is roughly 100 times less than that of the initial shell, so you have net loss, not gain. | |
| Jul 14, 2013 at 5:57 | comment | added | Doug | This is irrelevant if the thinner shell is strong enough to withstand that pressure; which, if the force exerted on it is less due to the pressure in the gap between shells, is not a big deal. The question is why would a single shell with pressure P1 on one side and P2 on the other side, have a force exerted on it that is magically unrelated to the P1 and P2. | |
| Jul 14, 2013 at 5:42 | history | answered | akhmeteli | CC BY-SA 3.0 |