pace GDP growth upwards of 100% per year seems strangely plausible
it can be even bigger than that, it all a matter of energy EROEI of that automated ecosystem, it can be a month or even less for 100% growth.
Admittedly, the idea that constructing artificial habitats in space could end up being cheaper than purchasing and developing equal amounts of suburban land, exurban land, deserts, tundras, or floating cities on Earth seems implausible currently.
Implausible? No, it will be exactly what happens - cheaper, cheaper than a tonne of dirt you can buy here on earth.
How could building an O'Neill cylinder in space be cheaper than building the most luxurious home downtown or in the suburbs?
Cities on the planet are the most expensive constructions we own, we build and put resources in them for hundreds of years and that process never stopped. We maybe chip a fraction of resources and power for that, but it is not such a small fraction, we could or would like to chip more for the goal, because it would be mean cheaper real estate, but we can't as we need those resources elsewhere as well, including to support other technological structures and infrastructure in between. But if it could be easy - we would absolutely do because population growth and a place to live in is one of the fundamental necessities for all sorts of reasons.
If we would imagine a necessity or a desire to build a freshly new city from scratch for let's say a million people, which is not even a big number for the good portion of countries - for any of those countries economy it would be a big burden, a job of titanic proportions.
After all, we have the industrial capability on-world
For any noticeable progress in space, technologies have to be moved in space, exported in space, we need to have them in space if we think about anything human-related on a scale of more than a thousand people.
So early human habitats could be built for entertainment or a way to signal high social status
Nah, not doing to happen, it like that argument that tourism will propel space exploration and all that. And if you look at numbers on how much money is spent on \$50k and more expensive tours - the market cap isn't high at all. At least, when I did such research I wasn't impressed.
yes, one can spend a billion on a yacht, and space hab may be considered to be a yacht-like expense/investment - but without a change of technological paradigm in space how big it will be? Will it even be a space hab.
We do have some number of riches on the planet, and how much out of them are space-oriented? Five? I'm about right, eh? And who succeeds? One, maybe a second as well but it takes a long time for him.
They do have all the billions, all the billions they need but it does not look like enough, nor are the results that impressive. SpaceX is good, and I expect a lot from them, but yeah, it a long way to space habs that way.
So if we see space habs only if it will be interesting for many people. If the move promises them something better in terms of opportunities or future or present. Riches can make a pinhole, at best, the flood which breaks the wall is the people. Those riches who get rich forsee and cave in for the needs and desires of these many people.
That's your frame challenge if you like.
Can space be cheaper than Earth
Let's see which prerequisite we may have in space. Can goods be cheaper than on earth? Live cheaper and better?
Solar energy is on the rise on the hype, for quite a long time on earth. But let's see what it is in space, right?
The same solar panel as one my use on earth, let's place it in space:
- it gets 30% more power, just because there is no atmosphere
- it gets around 3-4 times(not an exact number) more sunlight just because there is no day/night cycle
- no weather, not blackouts - constant supply of constant power
So energy price, in the case of solar panels, without a change of technology - can be improved about 5 times, compared to the same on the planet.
Solar for space, at least in our orbit, is one of the most convenient sources of energy, and that 5 times difference does not end yet, continue:
- the panel does not have to be strong, robust as it is in a microgravity
- there is no wind that tries to rip it off
- not water, no snow - which tries to corrode it
So for the reasons and conditions which are in space, a panel loses weight considerably, and that are the materials on which we do not have to spend energy to produce them, making the thing even cheaper, improving EROEI.
And here is a nail in a coffin of expensive - food-grade foil that can be used to concentrate light. Do you know those stations?
This is Crescent Dunes Solar Energy Project, and its construction cost is $0.9B, for production, if everything is good, 110MW. In the picture, there are about 10'000 mirrors, and I guess it easy can be at least 10 grand apiece, and the mirror isn't that big less than 70 square meters, and that amount of aluminum foil in small rolls costs about less than 20 bucks (two rolls 44 meters each). And it will concentrate at least a few times more energy.
So how about that as price slashing - 10 grand best cases vs 20 bucks worst-case prices.
Energy prices can be orders of magnitude cheaper, there is just no way we can dream about such prices even if we get fusion working. Not talking about no need for land reclamation, works everywhere in orbit. There is no way we can achieve that in foreseeable future on earth.
But that isn't the most fun part of it, if you still there, let's get to the fun part
Goods, can they be cheaper?
Take look at your phone, tablet - those are small devices, they are technologically advanced devices, but the amount of materials used in them is small.
Do you think, that you would sell the materials, raw components - will you get even 1 percent of the sum you paid for the device?
The main cost of production, not the design, is the energy we use in conversion of initially small amounts of materials - shaping, purifying, etching, cutting, etc. And on the production of tools, we use in the processes.
Energy is the blood and air of technological society, civilization.
Wages in the production business are about, 20% of expenses in a place where I live, and the rest can be attributed to energy this or another way - wear and tear of equipment, direct energy expenses, raw materials - those are the main expenses.
Raw materials - making steel as an example - energy expenses are the main expense in that process.
Wear and tear mostly the same problem - spend energy to shape blanks and raw materials in some product, which makes the tool which wears and tears - to replace or make a brand new tool, and recycle the old.
Recycling - the same main problem is in energy for the separation of things in useful composition.
Nothing works in modern society without electricity and energy and it is an important part of GDP and its availability and its prices will be reflected in all the products which are made.
So they absolutely can be cheaper multiple times cheaper, especially if there is enough automation. And especially those which are high-tech units.
A lot can be said here but if you connect the two dots - you will be on a right track for anything else.
Speeds and feeds
The prerequisite for human expansion is exporting technologies in space, in its full capacity basically, it may be not that hard as many may perceive that problem, won't be easy as well. It can be significantly cheaper than many think, in terms of what we need to get in space to bootstrap that, and most of the work should be done here on earth, in a sense of designing systems and collecting technologies in a suitable package.
Exporting technology in space is a big topic, but it is a necessity if you like to think about human expansion and an absolute necessity if you think about overtaking the earth's production capacities.
It will take some time, but again things may be simpler, as bootstrapping technologies can be quite limited and not great in numbers, and the rest we can transmit over the link from the planet - so mostly a groundwork on the planet - how much it may take - there is no way to say this - a decade may be more than enough.
Growth
At quite extremes but the speed of growth of technologies, meaning production capacities, can be extremely high, like 100% every 3 days, based on EROEI.
It will be different for different products, energy production is most basic, most important and fastest. With some lag next level production, next next level, and so on. But in the end, the first most basic layer in the technological pyramid will define the power of production output, and the whole pyramid establishing may take few years, depends on how you do that, how prepared you are. if you have all the plans ahead of time then it may take a year or something around that time, if not then a decade.
So for multiple reasons, a topic for a different q, technology won't be a source of the bottleneck.
Human growth is about 2 percent per year, but it is a number that can be regulated and the results of it take time if we talk about natural means to grow people.
2 percent of population growth is a relaxed number it can be higher and it can be lower no matter the other factors, but with 2 percent nobody is stressed, everyone has time for many things, one of which raising humans.
2 percent growth, per year, means in a century it is a 7 times increase of initial population. So if you start with a million then it just 7 million after 100 years.
But with technologies exported to space it possible to lift everyone who wishes to live in space, so the number may be bigger, to begin with, but it depends on the living places.
- my apologies here, 2 percent, remembered the number incorrectly, history-wise there were 2.2 percent and a bit more, but today's averaged around 1.2 percent. All statements are still true, and it can be considered to be one of the fast versions of growth, but it may be more than just 1-2-3 kids in a family which is more like the modern way with all that. But all that does not affect conclusions or potential timeline.
Space habitats
it a topic on its own, but what is related to the question of speed of growth - is the attractiveness of those places.
Easier access to technological products, food, resources for personal and group projects - definitely may attract quite a number of people. Have 5 time more for the same work - quite good, maybe - work less, have more - like that better. So we may expect a potential of a billion or even a few billion people to consider the idea to move in space, but if their environment conditions will be good enough there.
if environmental conditions will be good - spreading the idea and catching up on it and moving to the idea to move won't be difficult in our days - youtube will help, or whatever user governed analog will there be in that time.
But designing, ironing the inside of space habitats will take time. We not exactly starting from scratch, and there may be healthy ideas out there about nuances and stuff, but ecological microbiological aspects it will take time - decades.
All in all, it may start with 10-100million people. Space and that growing expanding situation is the real future and where real opportunities and real rewards for your effort are, so based on regular migrations in the world, the number may be quite realistic. And better are the conditions, faster people move.
So growth probably will be mostly due to the move from the planet in space, so it may take less than a century before space population will be bigger than earth one, and thus make more and have bigger numbers in everything.
side note
This is one of the aspects I hate in The Expanse.
besides water, another aspect which irritated me the whole seasons is that - man, you already in space, nothing separates you from turning the sky with your hands why aren't you doing it - why???!!!! There are thousands of roads to heaven and no road to hell, but you manage to breach into hell - how, why, aaaaaa!!! LoL
Conclusion
The most critical part is exporting technologies in space, until it has done, nothing extreme will happen. Mars won't happen. Space habitats won't happen. And as long as this part is postponed, by so much you can delay the expansion. A century, few, as many as you pleased with.
The rest, dust most likely settles in 50 years after that.