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Well, not quite. They were making diamond windows from atmospheric carbon dioxide at room temperature in household machines or machines you could rent at the po
by db48x 2y ago
Well, not quite. They were making diamond windows from atmospheric carbon dioxide at room temperature in household machines or machines you could rent at the post office. We’re a ways off from that yet.
- Terr_ 2y agoAlso the whole aerostat thing where you make a diamond "balloon" full of vacuum that floats in air, using the strength of the rigid diamond to avoid it being crushed and popped. I'm no materials-scientist, but I did some napkin-math on that once and it came out to some ridiculously-thin-sounding layer of diamond.
- jayd16 2y agoso I guess it needs to be like 1/4th the thickness of the latex in a balloon (diamond is 4x the density). Vacuum gives you a bit more lift than helium but not that much. Yeah, seems pretty thin.
- db48x 2y agoYea, a bit of artistic license on the author’s part. You could make things quite light though.
- _yb2s 2y agoThe pressure across a latex balloon is only about 0.5% that of maintaining a vacuum in earths atmosphere. I’m guessing the diamond would need to be much more than 1/4 the thickness of a latex balloon.
- HPsquared 2y agoBuckling would be a problem.
- deleted 2y ago[deleted]
- Terr_ 2y agoRedoing the napkin math because I can't find the original and I've somehow nerd-sniped [0] myself. Assume a sphere that contains a cubic meter of air and is neutrally buoyant: Vacuum volume 1.00 m^3 Vacuum radius 0.62 m Air density 1.23 kg/m^3 Displaced mass 1.23 kg Diamond density 3250 kg/m^3 Diamond volume 3.77E-04 m^3 Sphere surface area 4.84E+00 m^2 (Thin shells can be approximated by ignoring curvature) Shell thickness 7.79E-05 m Shell thickness 77.94 μm (microns) Human hair thickness 17 to 181 μm (microns) So the big vacuum-ball somehow needs to withstand crushing using only the strength of a diamond skin, and that skin is around as thick as (some) human hairs. It has to be thinner if you want it to float with a payload. Remember: The walls of party-balloons and soap-bubbles are a very different situation: They can have extremely thin skins because the gas inside is doing almost all the "don't get crushed" work, the skin is really just there to keep the two gases from mixing. [0] https://xkcd.com/356/ https://xkcd.com/356/
- db48x 2y agoPerhaps they use a diamond frame filled in with graphene instead. Still seems pretty unlikely though. And probably too easy to puncture, ruining the vacuum. Or perhaps they just build surfaces out of more complicated things than carbon. Hydrocarbons could be as easily assembled as diamond with similar techniques, and are a lot lighter than pure carbon. Plus they would want to put electronic advertising on the surface of the ball anyway, so it’s got to have a bit more going on to form LEDs and whatnot.
- Terr_ 2y agoI was thinking about smaller bubbles and aerogels, but when the volume changes by a factor of 0.10, the thickness-budget only changes by a factor of ~0.46. So while many smaller spheres--or pockets sharing walls--might be easier to engineer, the square-cube law [0] eats away at your lifting-power as everything becomes mostly-diamond with very little air-displacing vacuum. [0] https://en.wikipedia.org/wiki/Square%E2%80%93cube_law https://en.wikipedia.org/wiki/Square%E2%80%93cube_law
- hammock 2y agoI guess there is some sci-fi book everyone has read but me?