What sort of weapons manufacturing could be supported by a post-apocalyptic world?

Question

I've just been working on this post-apocalyptic setting and was wondering what level of weapons technology it would be able to support. Essentially a combination of land degradation, global warming (due to stuff like changed rainfall patterns and the spread of pests) and the depletion of resources like oil and rock phosphate (not to the point where they have been completed used up, but to the point where the easy to access deposits are mostly gone and what remains is much more expensive) led to a gradual but significant decrease in global food production. Exacerbated by increasing droughts, natural disasters and the emergence of new diseases (as habitat loss brings humans into contact with animals), our globalised, industrialised society collapses as billions die in a series of wars, famines and plagues.

Now it has been almost a century since society as we know it ended, and about 90% of humanity once again makes a living from hunter-gathering or subsistence agriculture (largely in the form of pastoralism or shifting agriculture due to poor soil quality and climate variability). The rest of humanity lives in small market towns or some larger cities that have popped up along major trade routes or near areas with some rare and useful resource/asset (like an old hydrolectric dam). While many of these cities have some degree of industrial manufacturing and some more modern technologies like electricity and wood gasification, the lack of resources and loss of more technical knowledge mean that they are pretty primitive by modern standards. Mining would be fairly limited as most easily accessed mineral deposits have been mined out and few groups would have the technology or resources to access the deeper deposits, so most metals would have been scavenged from the ruins and/or recycled over generations by survivor communities.

While day-to-day survival is the main concern of most people, various conflicts still occur ranging from tribal cattle raids to major wars between city-states. And I was wondering what sort of weaponry would likely be used. Of course this would vary based on what groups we are talking about (the army of a large city state would obviously have more advanced weapons that some isolated hunter-gatherers), but I imagine that even the most advanced groups would be limited on what they would use due to a lack of resources. The question is less what they could produce (as many cities probably have have the technical knowledge to make weapons of at least a WW1 level) and more what they would produce (as these cities would lack the population and industrial capacity to supply a WW1 level army, with the various market towns and nomadic tribes being even more limited).

I personally imagine that the advanced cities would maintain a limited stock of bolt/lever action rifles (that use black powder cartridges and mercury fulminate firing caps) with some Girardoni style air rifles (the setting would remove many of the disadvantages associated with them historically as modern materials that have been scavenged/reproduced in limited quantities would make reservoirs less likely to crack, while electric pumps powered by water/air/biofuel would make filling them easier than with hand pump). Most other peoples would use black powder flintlocks, that the more advanced peoples manufacture and the less advance trade for, while some more isolated peoples rely on bows and spears. Of course, I'm really interested to hear what other people have to say. Would the weaponry be more or less advanced than what I've described? Are there any technologies that I've forgotten? Thanks for any feedback

Answer 1

The Info Age Collapse will not Happen Everywhere

10% of the current world population is still a lot of people. Basically, you've sent the world population back to the 1700s which was enough people to support the early industrial revolution. This means you still have enough people for factories, major shipping companies, etc. as long as someone is able to maintain order in any significant portion of the world.

More over, you have not necessarily destroyed modern knowledge and technology. Currently, ~26% of the world's power is met by renewable energy; so, depending on what method people used for wiping each other out, it is very much possible that enough renewable power infrastructure was left over (or built in the aftermath) allowing new civilizations to fully power themselves entirely on renewable power sources.

Also, every war has a winner... or at least a least loser... So, while 90% of your world was wiped out, it is likely that a few nations mostly survived. They would have achieved thier goals of wiping out thier enemies and procuring the resources they need to not completely collapse. So while your super powers may have all nuked each other to into oblivion on day 1, you might have places just remote and civilized enough like New Zealand or South Africa to have survived the main conflict mostly untouched. Or it may have gone the other way where a major power like the United States or China developed good enough of a national missile defense system that they single handed wiped out all of thier rivals in a massive nuclear offensive while being able to mostly stop most attempts at fulfilling Mutually Assured Destruction.

Either way, you will probably have a few pockets of civilization still producing fighter jets, tanks, and computers, but most of the world will become more like many parts of Africa and South America are now: a weird hodgepodge of primitive technology ruled over by local warlords who have managed to buy, borrow, or steal a few modern marvels that give them incontestable control over thier territories.

So to answer your question, it is very much possible that some factions will remain that are 100+ years more advanced than we are today. These factions may very well have populations in the 10s or even 100s of millions and possess technologies that do not even exist yet (plasma riffles, nanite swarm weapons, holographic or neurological computer interfaces, etc.). Basically, think about how the United States economy pulled ahead of the rest of the world following WWII because they avoided the massive devastation that happened to the rest of the world, only the devastated nations in this case are much more devastated.

The collapse of supply lines will certainly cause a major economic depression at first, even in those countries that do avoid the bulk of the conflict, but as long as these countries still have thier existing computers and machine shops (or at least a few guys with better than normal garages full of tools that can be quickly worked back up to proper machine shops), they should be able to fill in the missing production gaps over the next 5-20 years before all of thier old stuff breaks down and stops working... and once they do they will enjoy at least a few decades of hegemon status that will allow thier technology to flourish and advance very quickly as they exploit the rest of the world for its resources.

Addressing Resource Scarcity

Most of the issues our world is facing on its current track have far more to do with environmental damage and a hand full of very rare resources. Both of these issues are self-solving in a future with a smaller human population.

Fossil Fuel depletion is not nearly as much of an issue as it was assumed a few decades ago. Every year we are discovering that many of our fossil fuel reserves are much larger than we first though and new ones are being found deeper and deeper. At this point in time, human kind has identified more than enough fossil fuel reserves to trigger a run-away greenhouse effect at current levels of consumption. This means that humanity will never be forced to give up fossil fuels because they have run out, instead we will have to choose to abandon them before we kill ourselves with them. However, it has been estimated that the Earth's environment can sustain ~500 million civilized humans indefinitely. So, once you reduce the human population to about 770 million people (assuming at least 1/3rd of them are forced into the uncivilized wastelands and that there is not a significant recovery of our population), consumption will be reduced enough that man kind could safely continue burning fossil fuels for hundreds of years using only the reserves we know about today.

Most common, industrially used materials like iron and aluminum are also far too abundant to ever run out. Over the course of the next few hundred years, we may be forced to use slightly less rich aluminum and iron sources which will be a little bit more expensive to refine. But economically viable versions of the ores we use most are literally everywhere on Earth.

The elements we are at much bigger risk of running out of today are the rare Earth elements used in many electronic devices (Yttrium, Scandium, Holmium, etc.). That said, many manufacturers are already working on phasing out the use of rare Earth elements from of thier designs; so, by the time we get to the point where we run out, we should not need them anymore. And if your post apocalyptic people need these elements, they just need to go find a bunch of old computer parts. Once you eliminate 90% of humanity, the amount of resources you can scrounge out of what is left over will be far greater than what you actually need.

The other somewhat scarce elements we need to worry about are conductor metals like copper and gold. While scarcity is also starting to become an issue in these areas today, it is mostly because we are using so much of the stuff at any given time with our current populations. Just like with the rare-Earth elements, unless the old cities have been vaporized, then you will have 10 times as much copper of this as need just sitting around, already refined in the form of powerlines and household wiring.

Depopulation will also mean we could no longer utilize all available landmass; so, natural landscapes will begin to re-emerge in many parts of the world making the lumber industry and crop-rotation viable again.

Answer 2

While it's a crude rule of thumb, it's a fairly good one: 90% of technology is material science.

The second rule is one about firearms--the gun is only one quarter of a mechanical system composed of the firearm, the propellant, the projectile, and the operator.

So what materials are available to your cities? If it's WWI-level weapons, well, that's almost at modern firearms levels. WWI-era firearms are high grade steel and precision mass metalworking.

From what you describe earlier, I doubt that's the case. To set up mass manufacturing, not only do you need the tooling which produces the product, you need the tools to produce the tooling. In most cases, that's very heavy equipment relying on a lot of infrastructure.

It'll be hard to answer your question with more specific definition of specific metalworking techniques available. Also consider: scavenged modern equipment isn't going to last very long esp. with frequent use. Gaskets wear out, manifolds erode, and without replacements it's probably only 50 years at the absolute most that the last few operable pieces of modern machinery are still working, ship-of-Thesaus-style using scavenged parts from all the other dead examples of the same machinery.

In short: can you clarify more specifically which materials production techniques are available, so we can figure out what you can actually do with them?