Uranium city

The greatest need of the permanent flotilla – and a need for all the solar-system – is energy. Some of it is solar, especially close to the Sun - like dayside Venus. But solar is not always enough. Plan B, then: nuclear fuel.

Start with the fuel itself. Wherever the ore comes from; we must refine it, and reprocess it. That takes a centrifuge. You may remember such from the news where they're talking Iran. The material I've chosen is Uranium-235; but we can analogise from here to any other separation-process that involves high temperature, high pressure, high energy, dangerous chemicals, and toxic waste. All the stuff you'd rather have done on another planet.

Uranium-hexafluoride has a “triple-point” from 340-500 K. Over Venus a bubble can reach the low-end of this (high) temperature - assuming the mid latitudes - from up to 50 km altitude, the lower range of where these latitudes hit pressure of one bar (pdf); down to where (by coincidence) tin melts, at 30 km altitude. All below the cloud deck but still in the haze. UPDATE 7/24: We have tech for that 40 km up and, since air isn't liquid, our design can be more uniform per vertical level. UPDATE 8/9: We can recapture waste energy here; unlike that 900 tonne submarine-reactor. So: helicopter-assisted?

This bubble is untethered, so drifts over the surface. This way the bubble can jettison depleted-UF₆ and other wastes onto the low parts of said surface, and not mess up the environs of such surface mines as I expect for the highlands.

For the centrifuge, this bubble (city) uses its own power supply – and, since solar and wind power are insufficient down here, that supply is itself nuclear. That extra heat would also pull water (as steam) from the ambient acids directly, without a Sabatier; and it sterilizes the “grey water” from the crew.

The city takes in spent uranium, for reprocess. And replacement parts.

The most important (and first) industrial low-floater floats over the equator; that's mainly a warehouse, for the flotilla. This further can take advantage of the upwelling Hadley air although it's not very strong (D Crisp, "Radiative forcing of the Venus mesosphere" #2, Icarus 77, 1989: 0.015 m/s).

As to the water, the Girdler sulfide process exists between this factory and whatever is above, to grab some of that Deuterium. Normally the hot tower could ride further below but we have extra heat here. That 15%-20% H-2 water is exported, along with excess U-235.

These bubbles drift like the farm bubbles. I'd suggest the industrial bubble and a farm bubble float in tandem but this might be a waste of energy over the long term. Also semipermanently tethering the low-altitude powerplants with mid-altitude farms across, what, 20km seems dangerous. I think each balloon handles its own watermaking from the acid, and does the best it can generating its own electricity. Every few days the low bubbles and high bubbles resync, and they can trade.

The productive farms will be in the 50s° latitudes: where the weather is nicer, the industrial bubble can change its farm as needed, phosphates can come up from the mines, and the bubbles can (probably) float closer together. In early days the Aphrodite Terra farm is nonideal but good for practice in extreme conditions. That one later will become a university.