Talk:Cloud Nine (sphere)

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

message: 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)
thread_title:  potential sources 

message: 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" )
*My 10cm solid steel plating theme, got the raidus at more than 240 Kilometers..!! which is cool for a huge atmospheric mega -monument bouble.
Steel, is about 7-8 tons per cubic meter. very strong
*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)
replies: text: 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)
replies: text: 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    ¥    Jacky Tar  20:26, 10 October 2020 (UTC)
thread_title:  Feasibility  of Real floating Cities

message: How is this not the same thing as a hot-air balloon? Shmuser (talk) 22:24, 29 December 2016 (UTC)
replies: text: 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.    ¥    Jacky Tar  20:30, 10 October 2020 (UTC)
thread_title:  Distinction