This question is a continuation of Unprepared and Without a Homeworld.
In my previous question, I proposed a theoretical near future in which a population of 10s of thousands of people live in space.
The vast majority of these people are machinists, pilots, geologists, chemists, engineers, industrial architects, etc. Manual labor would be mostly automated.
For understanding of how these people are living, the majority of this population exists in mining colonies distributed throughout the asteroid belt. Asteroid colonies would include hundreds of smaller, not-self sufficient bases with crews of 5-50 people, with a few dozen mostly self-sufficient industrial/economic bases with populations typically in the 200-1000 range. The total population in the belt would be about 40,000.
There would also be a larger base on Mars with about 10,000 people which would serve as an industrial center for building and maintaining the majority of the ships, space stations, and durable goods in the belt.
The general overview of the trade economy would sort of look like:
- Luxury goods, polymers, and advanced technologies would be imported from Earth to Mars.
- Mars would combine the polymers and advanced technologies with less advanced parts made from local resources to supply the belt with most of their manufactured goods.
- Mars would also act as a distribution center for the luxury goods from Earth.
- The larger asteroid bases would contain artificially lit farms that would produce regular shipments of consumer goods to the smaller mining bases.
- The larger asteroid bases would also contain refineries that process ore that they get from the smaller bases. Most of this ore would then be shipped back to Earth, some might also go back to Mars.
Based on a Ideal size for a relativistic generation ship?, it is estimated that it would take 23,000 tons of infrastructure per person to make space survival; so, assume the total mass of colonies is probably about 1.1 billion tons of infrastructure to support human life, plus a few billion tons of infrastructure to support all the cumulative mining, processing, manufacturing, shipping, and storage needs of the population.
I'm hoping for a near future scenario which is not so far in the future that modern governments and technology are still mostly relevant and recognizable, but I'm having trouble reconciling that with the several billion tons of mass required to build such colonies. According to this article, it costs 62 million dollars per launch to send 70 tons to mars. So, 3 billion tons of infrastructure would take ~266 trillion dollars just to launch into deep space barring any cleaver cost cutting solutions.
The one unrealistic technological breakthrough that can be assumed to be discovered within the next few years is cheap cold-fusion. If other un-developed technologies are proposed, please cite a source that gives reason to think it would be plausible to expect within the timeline given.
Assuming the collective Governments and Corporations of the world decided today that colonization and mining of the asteroid belt should be treated as a major priority, how could costs be cut to make this doable in the next 25-50 years using no more than 10% of the world's GPD?