The Empire State aerostat

In 2003, one Geoffrey Landis argued the case for Venus; here's PAT's copy at The Space Monitor in 2007. Landis also crunched (some) maths on how a colony there might look - it would float, using Earth's atmosphere as a lifting-gas. I'm taking this further.

Landis implied 50 km above the equator. Here, says he: A one-kilometer diameter spherical envelope will lift 700,000 tons (two Empire state buildings [ed. he means metric]). A two-kilometer diameter envelope would lift 6 million tons. He recommends the city be contained in this envelope. A half-kilometer radius sphere wraps 523,598,775 cubic metres. So he is claiming overall internal density 1/748 tonnes per cubic meter. That's the same unit as kg/L and gcm^-3. To work with it better: 1.3369 g/L. By contrast our breathable air is 1.18 g/L.

But it won't be evenly distributed. And Landis is not literally asking his Venereans to inhabit a sphere with a one-km (or two-km) equatorial platform bisecting it. A sphere rolls, and will tilt that platform. Also the platform would press upon the sides of the ball once an actual Empire State Building's worth of mass is planted on it. And it hardly makes the best use of the available outer wall.

I would suggest a sports-bleacher model. The inhabitants live, and farm, on terraces leading to a tapered bottom. That bottom is tied to Kindltot's anchoring kite-tether, to help keep this bubble from shaking. The terraces are grounded to the outer wall; which is stiffer and more resilient than the bubble walls containing the atmosphere above. The wall is also somewhat slick, but cleaning-robots can manage it.

Any trash that falls should (eventually) slide toward this well. It is the sector's responsibility to catch what trash it lets fall; those cleaning-robots will help in this. There is a final trap at the bottom of it all to catch what trash didn't get caught above. The general sector of the trash's source is marked so that the sector's cleaning efforts are audited.

An alternative shape for a floating city is the torus - the "donut". I take this shape more seriously, at least as predecessor.