From TL9^ interplanetary to TL10^ interstellar space opera in 200 years or less?

[vicky_molokh]

Greetings, all!

Both single-solar-system space settings and many-star-system space operas seem reasonably common, but I'm wondering: how does one develop a setting from one to the other? Babylon 5 is occurring around 2250s; Star Control around the 2150s; Mass Effect around 2180s (with multiple colonies with populations in the millions, while the interstellar phase began in the 2150s); Star Trek TOS seems to be place around the 2200s.

So let's say that I have a TL9^ setting, with reactionless drives to solve the SSTO issue, a homeworld population of about 4 billion, and about 10-50 million spending a significant part of their lives or even outright living offworld or on other worlds of the system (unobtainium mining, orbital power plants, zero-G alchemy research, logistics for all of the above etc.). On Staryear Zero, the first successful FTL trip to a nearby system occurs. Let the staroperatification begin!

Things that worry me:

• The rate of building up colonies. Making multiple self-sustaining colonies (not outposts) with a population ranging from at least a few millions to a billion seems like something that's hard to pull off in 200ish years. It means either focusing more on non-operatic technologies such as creation of rapid-breeding transhumans, or moving lots of people around.
• Moving lots of people offworld implies having a large colonizing fleet. Yet somehow I doubt that a planetary population will spend more than about 0.5% of its Monthly Average Wealth Income on such a fleet and the colonization itself. Maybe 5% if there's some big long-term existential threat (because societies like being in denial). I suspect that this would be extremely little.
• Assuming the colonies will be founded by rather modest populations compared to that of the homeworld, just how fast can they grow, assuming that a new planet both has a biochemically compatible ecosystem (this isn't hard-sci!) and reasonable resource value?

Has anyone had the worldbuilding experience of going through this process? Or just ideas how to make it 'work'?
Thanks in advance!

[Gadget]

GURPS Space gives a good way determining homeworld colony and outpost
populations over a specified time period step 10 in the world building process p91-93

[ericthered]

If you want rapid colonization you need both a reason for people to want to get off of the homeworld and fairly cheap means to do so. This probably means dropping the cost of your ships. Or greatly increasing the wealth available. Or both.

If I read your post right, you start with "earth" at half its current population, and twice to ten times that number in orbit. At this point, why are they still using planets when they colonize the system? You don't have the population pressure you need for rapid colonization, and it looks like you have enough space infrastructure that planets aren't a big deal.

In most science fiction, you have a number of planets being colonized, and a steady stream of immigrants. you don't suddenly go from being a single system civilization to a 50 system civilization: it happens slowly, with worlds building up populations. At first, its unlikely more than six worlds can gain substantial populations compared to earth.

Think in terms of total population: what is the final number you need?

[vicky_molokh]

Originally Posted by ericthered

If I read your post right, you start with "earth" at half its current population, and twice to ten times that number in orbit. At this point, why are they still using planets when they colonize the system? You don't have the population pressure you need for rapid colonization, and it looks like you have enough space infrastructure that planets aren't a big deal.

Woops, my mistake. Edited: 10-50 millions of people in orbit/on other planets part- or full-time. But half of Terra's population is just a number in a setting I'm currently running, which I imagined as one of the possible starting points for such a development.

Originally Posted by ericthered

In most science fiction, you have a number of planets being colonized, and a steady stream of immigrants. you don't suddenly go from being a single system civilization to a 50 system civilization: it happens slowly, with worlds building up populations. At first, its unlikely more than six worlds can gain substantial populations compared to earth.

Suddenly is relative. Mass Effect lists 30 human colonies (with no less than 5 of them having a almost a million or even several millions of people).

Originally Posted by ericthered

Think in terms of total population: what is the final number you need?

I'm hoping to achieve 6-12 garden worlds with ½-1 billion (10^9) people each by the end of the expansion phase (i.e. by about mid-TL10^, about 200 human years from the start of the expansion).

[ericthered]

Suddenly is relative. Mass Effect lists 30 human colonies (with no less than 5 of them having a almost a million or even several millions of people).

One million isn't what I meant by "Substantial populations compared to earth". The United states alone sports 46 metropolitan areas with double that population. That's a collection of outposts. Million person outposts, but outposts none the less: the collection of them has roughly the same population as Canada (chosen because its similarly large, wealthy, and not known for friendly weather). All together they are significant, not alone.

I was referring to populations capable of significantly interacting with earth in terms of population. You can populate thousands of worlds with earth's current population, but you can only populate a few with meaningfully large populations.

Originally Posted by vicky_molokh

Woops, my mistake. Edited: 10-50 millions of people in orbit/on other planets part- or full-time. But half of Terra's population is just a number in a setting I'm currently running, which I imagined as one of the possible starting points for such a development.

I'm hoping to achieve 6-12 garden worlds with ½-1 billion (10^9) people each by the end of the expansion phase (i.e. by about mid-TL10^, about 200 human years from the start of the expansion).

Ok, so you want to somewhere between double and quadruple your population over the course of 200 years, meanwhile moving all this excess population to new worlds?

To hit a total of 10 billion you can use a growth rate of .5%. This is half of the current global growth rate. If you use the full current growth rate of 1% you end up with 30 billion total. In that case, you don't just have the people you need to population those worlds, you probably also want those worlds so you can put these people somewhere. And if use peak global growth from the 1960's (2% per annum), you have 200 billion people to put somewhere. Those six colonies aren't going to cut it.

If you use the populating of the united states as an example, you probably get to move more of your population at the end of the period, not at the beginning. The UK had more people than the US until about 1860. That said, the growth rate stays steady at about 30% per decade from 1800 to 1880.

So your goal is quite doable.

[whswhs]

Originally Posted by ericthered

Ok, so you want to somewhere between double and quadruple your population over the course of 200 years, meanwhile moving all this excess population to new worlds?

We have an idea of the human doubling time. It was incredibly long up until the beginning of urbanization. At that point it went to around a thousand years, and stayed there, roughly, up until 1750, when it went to 50 years. With a fifty-year doubling time you could multiply initial population by 16 in 200 years, and that's without continuing immigration.

[Fred Brackin]

Originally Posted by vicky_molokh

So let's say that I have a TL9^ setting, with reactionless drives to solve the SSTO issue,

Unless your reactionless drive is limited in some fashion it will make STL interstellar flight possible as well. If not all the way up to .99 c then still at a useful percentage of say 20-40%. Alpha Centauri is quite reachable at such speeds.

[thrash]

If you sidestep environment and resource constraints, the biggest limiting factor on colony growth is infrastructure development. This, in turn, is driven by the tech level you want the colonies to maintain on their own: TL5 is easy (with the right starter package and skill set); TL9^ will take work.

Infrastructure can be created locally, by existing colonists, or imported. The main difference is that local infrastructure can benefit from exponential growth, while imported infrastructure requires resources (ships, mostly) that are likely to have a cap. The balance between the two shifts from all imports in the establishment phase to all local by the time the colony is fully mature and sending out daughter colonies of its own.

Eric's figures on growth rates are pretty good. I suggest you look at how much shipping you want to have available (which may grow over time), how much imported infrastructure each new colonist needs (in tons, on average) to be productive, and therefore how many colonists you can add per year over the organic growth rate.

Your initial population will look like an investment curve with interest plus regular payments -- much faster than just based on interest alone. Once the local population and infrastructure increases exceed the imports, you can quit worrying about imports.

Remember that each world has a saturation population level, based on habitability, resources, and tech level. As you reach that point, the growth curve should level out and then stabilize around that value. This is a reasonable point for some worlds to start sending out daughter colonies.

In my worldbuilding, I usually anticipate that this saturation point is reached in about 400 years of uninterrupted (by war, collapse, etc.) colonization.

[Daigoro]

Originally Posted by thrash

Infrastructure can be created locally, by existing colonists, or imported. The main difference is that local infrastructure can benefit from exponential growth, while imported infrastructure requires resources (ships, mostly) that are likely to have a cap. The balance between the two shifts from all imports in the establishment phase to all local by the time the colony is fully mature and sending out daughter colonies of its own.

There'll also be a trade phase of development, when daughter colonies begin to rely less on the mother system and develop a trade interdependence. This should allow them to exploit their comparative advantage to accelerate infrastructure development and get around the support export limits of the mother system.

[Buzzardo]

The Expanse series of books deals with just such a scenario. It starts with humans confined to their own system but having reached out quite a ways within the system. Then it finds a way for humans to get to other systems. Those books might give you a model from which to work.