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Comment by KineticLensman | Hacker News Reader

> trillions of people

Really? A frozen dwarf planet in the outer solar system supporting a thousand times more people than the Earth? Without a functioning biosphere or solar energy?

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Yup. Leaving aside that we have never yet to send an unmanned lander there, and it has roughly the surface area of Russia. If it were as densely populated as Manhattan over its entire surface it would have a population of less than half a trillion (appr 442,000,000,000) people. That on less than a thousandth of the W/(m^2) solar radiation of Earth.

I'd be really interested if anyone is bored enough to figure out a trillion person's population energy requirement and see how long a 50% mass/energy efficient fusion process could sustain a population of that size of a fuel base the size of Pluto. edit: assume 1 year at 1 GW-year per 1000 kg fuel for fusion power.. global energy use is about 18 TW-years, and round the population to 10^10 people. Not entirely comparable, but 10^12 people -> 1.8 * 10^3 TW-years or 1.8 * 10^6 GW-years. So about 200 million kgs of fusion fuel burned per year? And how much of the H in Pluto's water would be T or D?

Technically, once you start colonizing a planet's underground you have little vertical limitations. Manhattan isn't a cube, most people live in a 50 meters layer from the ground. 50 meters is nothing if you are building an underground grid.

Thermal insulation would be nearly perfect and radiating excess heat can be passive, so there wouldn't be energy usage from that.

Yes, but people have to eat and try accounting for per 1000 w/m^2 of sunlight over crop and grazing land, after adapting for food production in tunnels with LEDs. Or trying to figure imagine what transportation looks like. Easier to just look at current usage and accept it's a spitball estimate. For cubes, what building material available there will support 3-d structures at that scale? It's mostly ices out there. Relying Ni/Fe asteroids feels like magical thinking and is not in line with scales involved. For that mater, where's all the carbon going to come from to make the people out of?

For reference, if you assume 1000 sq ft per person (maybe generous, but you have to account for transportation conduits, plumbing, food production, structural reinforcement) with 10 ft height, it's about 300 cubic meters. For a trillion people, that ends up being a 70km cube. I doubt there is any durable foundation on Pluto, and any structure would melt the ground it's (axiomatic thermodynamics) without active cooling, which increases the energy requirements.

Ultimately, I don't see why anyone would want to live packed into a small cube on Pluto eating engineered food. A trillion people packed in a cube underground in a block of gas ices isn't going to experience wonder and joy of exploration.

Building a massive Trantor-like vertical city over the entire surface area would presumably exhaust / deplete the non-renewable resources that is the driver for this concept. What do the trillion people do then?

To quote Asimov:

"Its dependence upon the outer worlds for food and, indeed, for all necessities of life, made Trantor increasingly vulnerable to conquest by siege. In the last millennium of the Empire, the monotonously numerous revolts made Emperor after Emperor conscious of this, and Imperial policy became little more than the protection of Trantor's delicate jugular vein".

What would be the point of that? Even if possible, Mars is orders of magnitude easier.

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