Talk:Cloud Nine (sphere)

Benefit
while the concept is intellectually interesting (make a sphere big enough and it automaticaly floats), what is the claimed benefit of living in a giant floating sphere, as opposed to a giant sphere on the ground, or just living in a city? how does he account for the mass of all the infrastructure necessary to support thousands of ppl, in addition to the mass of the sphere itself? vroman 20:43, 5 November 2007 (UTC)


 * 71% of the Earth's surface is water, not land. Combine this idea with Ocean colonization and you've got lots of room.  I just read that you could grow food in them as well, so you could have floating farms, which would prevent habitat destruction due to agricultural land use. Viriditas (talk) 13:17, 13 January 2010 (UTC)


 * Yes, yes, but where are you going to get all the soil? Even if you go with relatively light-weight hydroponics, every ton you take on board is another ton of lifting capacity you need. An empty Cloud Nine is already pretty big. Seasteading is much less technically challenging (millennia of nautical engineering to draw upon), and look how well that's worked out. --Gwern (contribs) 16:02 14 January 2010 (GMT)


 * Interesting concept, though. Invmog (talk) 01:38, 20 January 2010 (UTC)


 * Sure, it's an awesome concept. If it were more efficient, I could see it being the way to travel the world, for example. But impractical. --Gwern (contribs) 02:25 20 January 2010 (GMT)

Development
Has anyone ever planned to, or attempted to build one? Oldtimeadventures (talk) —Preceding comment was added at 22:26, 5 June 2008 (UTC)

potential sources
Lots more potential sources are available


 * at google books —Preceding unsigned comment added by 207.69.139.147 (talk) 01:31, 18 April 2010 (UTC)

Feasibility of Real floating Cities
Hey people.

I'm new to the subject, but form intuition it seem like the Tensegrity sphere concept might just work. so went to look it up online and found NO credible engineering specs or boundaries. too bad for a cool scifi idea to go untested as to it's feasibility, right? :) Cities in the Heavens!

So, with some understanding of the basic principle in mind, I cooked up this formula:
 * Da =density of air displaced = buoyancy
 * Db=density of the slightly warmer air inside the sphere
 * Ds=the mass of the sphere it self, density of material in the structure (including empty space)
 * r=radius of the shell (10cm? 5 meters? 50?)

Now, since the volume of the sphere grows at R^3, and the surface area only at R^2, Tensegrity postulated that some sufficient grand size should suffice. I do wonder though.
 * WILL IT FLOAT?
 * R^3 *(Da-Db)-Ds( (R+r)^3-R^3 ) > 0

So it turns out that every 1 C degrees of heat, there's at least 0.5% offset in density (warm air is less dance). roughly speaking. at visible "cloud level", not more than 10 km high up.

Conclusions? (ran the numbers through mac's "Numbers" ) Steel, is about 7-8 tons per cubic meter. very strong
 * My 10cm solid steel plating theme, got the raidus at more than 240 Kilometers..!! which is cool for a huge atmospheric mega -monument bouble.
 * At 20cm of some material with a density distribution of 1/10th solid-steel I got about 45 KM.
 * At a two meter thick shell, made of something 1/100th of the solid-steel solution we can also get at about 45KM radius

At these sizes you get enough buoyancy to float mega Cities with hydroponic whateverness, but these sizes aren't attainable. I hope you can do better :)

So..
 * 0.check my math.
 * 1.How is it constructed? Assuming what materials what should be the shell radius of the spheric shell?
 * 2.how much mass can such a huge sphere support?
 * 3.what's the voyage altitude range? at what temperature?

I would start with a 500 meter radius for a relevant reference frame. that's gigantic,probably the largest man made object ever, but maybe kind of somehow possible..:)

-- Namaste@ ? 01:55, 3 December 2010 (UTC)
 * This was first proposed at a time when steel was the strongest material available. We now have carbon nanotubes. How big could it be if we used them?108.23.147.17 (talk) —Preceding undated comment added 21:36, 8 September 2011 (UTC).


 * Here's some discussion and numbers from about 4 or 5 years ago (so say 2015-ish): https://worldbuilding.stackexchange.com/questions/36667/can-cloud-nine-be-built  &yen;  Jacky Tar  20:26, 10 October 2020 (UTC)

Distinction
How is this not the same thing as a hot-air balloon? Shmuser (talk) 22:24, 29 December 2016 (UTC)
 * Depends on the sense of the question, I suppose. In terms of mechanics and physics, not much - both are hot-air lift machines. Scale makes a difference, though; this would be large enough to be self-sustaining, if it were in fact feasible. You'd probably have a population of around 10 or 20 thousand in it, whereas a hot-air balloon in this sense is a vehicle, not a community.  &yen;  Jacky Tar  20:30, 10 October 2020 (UTC)