Part Four, Critical Path, R. Buckminster Fuller, 1981, p336 – p337
Cloud Nine Floating Tensegrity Spheres
In 1958 I saw clearly the progression of technical events altering all odd engineering concepts regarding the relative increase in the overall weights of structures – and designed my sky-floating tensegrity structures, which I call “Cloud Nines.”
A 100-foot-diameter, tensegrity-trussed, geodesic sphere weighing three tons encloses seven tones of air. The air-to-structural-weight ratio is two to one. When we double the size so that the geodesic sphere is 200 feet in diameter, the weight of the structure increases to seven tons while the weight of the air increase to fifty-six tons – the air-to-structure ratio changes as eight to one. When we double the size again to a 400-foot geodesic sphere – the size of several geodesic domes now operating – the weight of the air inside increases to about 500 tons while the weight of the structure increases to fifteen tons. The air-weight-to-structure-weight ratio is now thirty-three to one. When we get to geodesic sphere one-half mile in diameter, the weight of the structure itself becomes of relatively negligible magnitude, for the ratio is approximately a thousand to one.
When the Sun shines on an open-frame aluminum geodesic sphere of one half mile diameter, the Sun penetrating through the frame and reflected from the aluminum members of the concave far side bounces back into the sphere and gradually heats the interior atmosphere to a mild degree. When the interior temperature of the sphere rises only one degree Fahrenheit, the wight of the air pushed out of the sphere is greater than the weight of the spherical-frame geodesic structure. This means that the total weight of the interior air plus the weight of the structure is much less than the surrounding atmosphere. This means that the total assemblage of the geodesic sphere and its contained air will have to float outwardly, into the sky, being displaced by the heavy atmosphere around it.
When a great bank of mist lines in a valley in the morning and the Sun shines upon it, the Sun heats the air inside the bank of mist. The heated air expands and therefor pushes some of itself outside the mist bank. The total assembly of the mist bank weighs less than the atmosphere surrounding it, and the mist bank floats aloft into the sky. Thus are clouds manufactured. As geodesic spheres get larger than one-half mile in diameter, they become floatable cloud structures.
If their surfaces were draped with outwardly hung polyethelene curtains to retard the rate at which air would come back in at night, the sphere and its internal atmosphere would continue to be so light as to remain aloft.
Such sky-floating geodesic/tensegrity spheres may be designed to float at preferred altitudes of thousands of feet. The weight of human beings added to such prefabricated “Cloud Nines” would be relatively negligible. Many thousands of passengers could be housed aboard one-mile-diameter and larger cloud structures. The passengers could come and go from cloud to cloud, or cloud to ground, as the clouds float around the Earth or are anchored to mountaintops.
While the building of such floating clouds is some years in the future, we may foresee that, with the floating tetrahedronal cities; air-deliverable sky-scrapers; submarine islands; sub-dry-surface dwellings; domed-over cities; flyable dwelling machines; and rentable, autonomous-living, black boxes, man may be able to converge and deploy around Earth without its depletion.
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