I was working on something else this morning and posted this to SFIA: I've heard it said that we're already building a Dyson swarm, the constellation of orbital satellites around the Earth and our satellites and probes around other planets and the Sun. That's thousands in about six decades massing a few thousand tonnes (I'm spitballing, should go look for the numbers) in six decades, call it 10^3.6 in 60 years, so about a megatonne in a century or a quarter gigatonne by 2100, a quarter million gigatonnes by 2200 and do on.

An Earth planetary swarm by the 22nd century and a solid Dyson swarm a few centuries afterwards. If one percent of the mass is habitats at a kilotonne per peep, that's a population of 2500 living in space by 2100 and 2.5 billion by 2200.

Thoughts, please? I got a few replies but I’m not expecting much. Interestingly, at 6 gigatonnes, we could have about 400 (1% of mass) by 2200, but this probably isn’t enough for 2.5 billion- oh, that's about 6 million per, a small country. Some of these are provinces or something of Earth-side countries, but many would be their own independent nation states.

This afternoon at dinner I was rewatching ‘Evacuating Earth’ again and Mom overheard the bit about getting a whale into orbit, so I told her about getting 8 billion people offworld, which is a couple of thousand of oil megatankers at a quarter megatonne each; squishy, rendered human bits… If we load up 747’s at about a thousand on 3 flights per day, 24 million flights into orbit somehow, that’d be about 1100 flights per year, round it up to four hundred thousand per 747 per year and need 20K spaceplanes. Of course, what we really want is a train, so a launch loop or a tether up to an orbital ring.

Honestly, we want to send each person into space with a bit of home, or even their entire home, as well as enough biomass to farm and keep them in milk and cookies, or pizza and beer. A hectare per person, 10^4 m^2 times at least a tonne of dirt per m^2, call it 10 times 10^4 is a tenth of a megatonne per person. This is completely unreasonable; we can pare it down to a kilotonne and bring their house or even their apartment building, at least their share of it, along with their neighbors… (Incidentally, I was figuring on rolling a strip of land up into a cylinder a kilometer in circumference and that works out to about 40 m/s or just under 88 miles per hour!) The payload needs to be kept at around one earth gravity, a little more or a little less, so we could accelerate at a constant 8 m/s^2 sideways for about 24 minutes, just above escape velocity and an upward spin gravity of about two gees less the one gee down to Earth. The passengers and payload experience between ~13 and 8 m/^2 until we roll them up in one smooth motion, hopefully!

A strip of earth 100 m wide by one kilometer times a tonne/m^2 is 100K tonnes, the aircraft carrier equivalent Isaac Arthur usually references, a sort of squat tube a hundred meters deep and about 300 meters across, something we could fit inside a football stadium. We’d want about 80 million of them each with a hundred peeps, and we will want to buff them up immediately with more mass for radiation shielding, at least a megatonne which we could source from the Moon, a cube ~30 kilometers across...