Was kind of noodling thoughts about how you'd populate space habitats. At the very least, populate them in a way that you'd have a pretty substantial population within, say, 50 years of shifting people into space.
For any of this to work, of course, we have to assume for a moment that the costs of getting people to around LaGrangian orbit is sufficiently low to not be prohibitively expensive to move large numbers - by that I mean in the order of tens of millions - in any given year.
You'd make a handful of assumptions in addition to this.
- World population growth levels off at around ~1% per year.
- You want to keep world population more or less constant. Perhaps even lower it a bit.
- The whole point of doing a mass emigration to space is to help raise the standard of living for everyone, both earther and spacer alike.
Subsequently this means:
- You need to move about ~80 million to space per year, just to keep up with natural population growth.
- You'd hopefully select people so that you'd take people living in marginally habitable parts of the world and shift them to space habitats (O'Neill Cylinders of one sort or another), where they'd live in big giant self-contained habitats that have a nice combination of soil, air, and water and 1g gravity to make it worthwhile to live there.
Random other thoughts.
The ideal here would be to craft habitats that are sufficiently large and well developed in terms of internal environment that you could guarantee people a pretty decent standard of living but not simultaneously need to have too many of them be anything other than (at most) moderately skilled workers.
At around ~30km in length and 6 in diameter you're looking at a surface area of about 280 square km...(Since half of the surface area is just giant windows to let in sunlight.) Which sounds okay, but that gives you only about a population of ~2,500,000 per cylinder if you wanted to keep population levels at densities comparable to a highly dense North American MSA (about 10,000 per square km).
Meaning you'd have to construct 30-40 habitats per year just to keep up with population growth.
And yet even in spite of all this, the idea of settling orbital space and constructing habitats perfectly suited for human existence still would make a lot more sense than resettling them on a planet like Mars absent some serious serious unknown ability to terraform it.
In terms of everything from available resources (you can lasso asteroids into LaGrangian Points around Earth) to the ease of making people live on them, these things still make a lot more sense than going to Mars ever will. Better gravity, tailored environment (temperate!), and likely not cheaper...
...but still - it's a pretty far fetched notion unless we maybe start figuring out ways to automate building them. And in the end, we might just have to accept even making for a sizeable non-Earth population in the next 3-400 years isn't feasible.