Colonizing Venus

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It's been years since I learned my Archimedes, but wouldn't that be the point precisely? Wouldn't the structure tend to settle at an altitude where the inner and outer pressures are the same?

No, it will settle where it's buoyant. In other words, it will settle where the mass of the volume of fluid (gas or liquid) it displaces is equal to the weight of the structure itself. So it's going to be settling at an altitude that is most likely going to have a much higher pressure than the pressure inside of it.

Aerostat habitats and floating cities
Geoffrey A. Landis has summarized the perceived difficulties in colonizing Venus as being merely from the assumption that a colony would need to be based on the surface of a planet:
"However, viewed in a different way, the problem with Venus is merely that the ground level is too far below the one atmosphere level. At cloud-top level, Venus is the paradise planet."
He has proposed aerostat habitats followed by floating cities, based on the concept that breathable air (21:79 Oxygen-Nitrogen mixture) is a lifting gas in the dense Venusian atmosphere, with over 60% of the lifting power that helium has on Earth.[4] In effect, a balloon full of human-breathable air would sustain itself and extra weight (such as a colony) in midair. At an altitude of 50 km above Venusian surface, the environment is the most Earth-like in the solar system - a pressure of approximately 1 bar and temperatures in the 0°C-50°C range. Because there is not a significant pressure difference between the inside and the outside of the breathable-air balloon, any rips or tears would cause gases to diffuse at normal atmospheric mixing rates, giving time to repair any such damages. In addition, humans would not require pressurized suits when outside, merely air to breathe and a protection from the acidic rain. Alternatively two-part domes could contain a lifting gas like hydrogen or helium (extractable from the atmosphere) to allow a higher mass density[5].
Cloud-top colonization also offers a way to avoid the issue of slow Venusian rotation. At the top of the clouds the wind speed on Venus reaches up to 95 m/s, circling the planet approximately every four Earth days in a phenomenon known as "super-rotation".[6] Colonies floating in this region could therefore have a much shorter day length by remaining untethered to the ground and moving with the atmosphere. While a space elevator extending to the surface of Venus is impractical due to the slow rotation, constructing a skyhook that extended into the upper atmosphere and rotated at the wind speed would not be difficult compared to constructing a space elevator on Earth.
Since such colonies would be viable in current Venusian conditions, this allows a dynamic approach to colonization instead of requiring extensive terraforming measures in advance. The main challenge would be using a substance resistant to sulfuric acid to serve as the structure's outer layer; ceramics or metal sulfates could possibly serve in this role.
Landis has suggested that as more floating cities were built, they could form a solar shield around the planet, and could simultaneously be used to process the atmosphere into a more desirable form. If made from carbon nanotubes (recently fabricated into sheet form) or graphene (a sheet-like carbon allotrope), the major structural materials can be produced using carbon dioxide gathered in situ from the atmosphere. The recently synthesised amorphous carbonia might prove a useful structural material if it can be quenched to STP conditions, perhaps in a mixture with regular silica glass. According to Birch's analysis such colonies and materials would provide an immediate economic return from colonizing Venus, funding further terraforming efforts.
Landis' point about the ground level being too far below the one atmosphere level was also used by Larry Niven in his depiction of Plateau, a Venus-like planet with a small section of its surface rising up to the habitable level of the atmosphere. Similar setting is used in one of the early Poul Anderson novels.

Wikipedia words it in a slightly different manner: According to Archimedes' principle, "Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object." (...) The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (if the surrounding fluid is of uniform density). Thus (...) objects with greater volume have greater buoyancy.

Don't thousand-ton ships float on Earth at sea level?

Don't thousand-ton ships float on Earth at sea level?

The atmospheric mass is 93 times that of Earth's atmosphere while the pressure at the planet's surface is about 92 times that at Earth's surface—a pressure equivalent to that at a depth of nearly 1 kilometer under Earth's oceans. The density at the surface is 65 kg/m³ (6.5% that of water).

Despite the harsh conditions on the surface, the atmospheric pressure and temperature at about 50 km to 65 km above the surface of the planet is nearly the same as that of the Earth, making its upper atmosphere the most Earth-like area in the Solar System, even more so than the surface of Mars. Due to the similarity in pressure and temperature and the fact that breathable air (21% oxygen, 78% nitrogen) is a lifting gas on Venus in the same way that helium is a lifting gas on Earth, the upper atmosphere has been proposed as a location for both exploration and colonization.

The atmospheric pressure at the surface of Venus is about 92 times that of the Earth, similar to the pressure found 910 metres below the surface of the ocean. The atmosphere has a mass of 4.8×1020 kg, about 93 times the mass of the Earth's total atmosphere.[1] The pressure found on Venus's surface is high enough that the carbon dioxide is technically no longer a gas, but a supercritical fluid. The density of the air at the surface is 67 kg/m3, which is 6.5% that of liquid water on Earth.

The area of the troposphere most similar to Earth is near the tropopause—the boundary between troposphere and mesosphere. It is located slightly above 50 km.[11] According to measurements by the Magellan and Venus Express probes, the area from 52.5 to 54 km has a temperature between 293 K (20 °C) and 310 K (37°C), and the area at 49.5 km above the surface is where the pressure becomes the same as Earth at sea level.[11][14] As manned ships sent to Venus would be able to compensate for differences in temperature to a certain extent, anywhere from about 50 to 54 km or so above the surface would be the easiest area in which to base an exploration or colony, where the temperature would be in the crucial "liquid water" range of 273 K (0°C) to 323 K (50°C) and the air pressure the same as habitable regions of Earth.

I'm unable to find any references claiming that there's a "layer" of nitrogen/oxygen in the upper reaches of Venus' atmosphere. Rather, as listed here, it's largely carbon dioxide and sulfur dioxide, with clouds of sulfuric acid (and tropospheric winds upwards of 300 kph!).

Nope, overall Venus looks like a pretty sucky place to attempt to colonize. I think I'd prefer to carve out (or maybe find?) caves beneath the Lunar regolith, or build shelters on Mars - they're both downright homelike compared to Venus!

Which is why you terraform it

The water's the easy part, at least easier than constructing magical floating cities. You just need to redirect a few megatons of ice from, say, the rings of Saturn into an orbit that will intersect Venus. (Relatively easy because all that requires is a lot of bombs and massive computing power. The computers are available, and if there's one thing we humans are good at, it's building bombs.)

Diversion by explosion is an excercise in chaotic dynamics. Diverting ice chunks is not cost effective. We simply do not have the resources even though the problem is, in theory, solvable. Venus is a losing proposition. We do not have the wealth necessary to undertake the terraforming activity.

Forty billion dollars and what do we have to show for it? ISS (aka sh**-can one)

ruveyn

Diversion by explosion is an excercise in chaotic dynamics. Diverting ice chunks is not cost effective. We simply do not have the resources even though the problem is, in theory, solvable. Venus is a losing proposition. We do not have the wealth necessary to undertake the terraforming activity.

Forty billion dollars and what do we have to show for it? ISS (aka sh**-can one)

ruveyn