Minimum TL for a self-sufficient Vault City or equivalent bunker?

[Kromey]

New user here, thought I'd throw in my 2 cents. (Disclaimer: Very new to GURPS; I've read the Lite rules, I've ordered the Basic Set [currently being shipped], I've never played a GURPS game in my life; my RPG background is overwhelmingly D&D, although I did play a Paranoia game at a convention once...)

A large enough volcanic eruption can blanket the entire globe, choking off virtually all plant life, in turn starving off animal life. The ash clouds released can remain in the atmosphere, blotting out the sun, for decades. The thick ash blanket would quickly cover up any air exchangers the city might otherwise have been able to use, conveniently explaining why they're hermetically sealed in.

However, it's easy to overestimate the extent of a volcanic eruption (especially if the politicians have a vested interest in exaggerating the threat) -- it could be that they saw this one coming somehow, ushered everyone inside, sealed up the city, and expected the world to suffer a catastrophic global extinction event. They remain in the city until they think enough time has passed for the air to have cleared and life to begin to recover on the surface.

In reality, though, the eruption only affected the local continent/region/whatever. The city could easily have no way of knowing this, until the 3rd Gen decides to take a peek and see how things on the surface look now. (1st Gen was under the boot of the Top 200, who had a vested interest in keeping everyone sealed in the city; 2nd Gen, well, simply wouldn't have thought to look!)

(Alternate explanation: The Top 200 simply lie about the extent of the disaster. Fearing someone might learn the truth, they even go so far as to reprogram Friend Computer to perpetuate the lie as well, which explains why in persists after they die off. Then the doors are only unsealed when "rogue" 3rd Geners decide they don't trust FC for some reason and have a look for themselves.)

Another disaster option could be an incoming extinction-sized meteor spotted by the astronomers. We all know what those can do to a planet (see: dinosaurs). Only the astronomers got their calculations wrong, and only a small fragment actually struck the local area, while the larger piece actually passed by harmlessly. Otherwise, everything is as above. (I'm not familiar with the tech levels (I mean, I know what they are, but I'm not familiar with what exists/doesn't exist at the different TLs), so I have no idea where astronomy would be, or if this is a reasonable scenario for your desired entry TL.)

As a third option: There are, in the real world, "dead zones" where no plant life grows. Some of these we can't explain -- no known toxins or radioactivity or anything present to explain them. Perhaps one of these "dead zones" appears nearby and begins spreading. Maybe more than one. No one knows what the cause is, but as it spreads further and further people start to panic. Fear overrules reason, and society retreats into the underground city.

In this scenario, since no one knows the cause of the growing "dead zone" that eventually engulfs the entire continent, completely sealing in the city seems like a prudent idea -- maybe it's an airborne contaminant of some kind, in which case you definitely don't want it getting inside the city. Likewise, no one knows that it's not global -- in fact, it's reasonable to suspect that it is, especially if several seemingly independent "dead zones" appear, as opposed to just one that grows. Similarly, scouts can routinely peek outside the vault, and honestly report that the surface world is still a barren wasteland.

This scenario, though, becomes problematic at the unsealing point: What makes them suddenly think they can safely unseal? What's the point in unsealing and emerging if the local area's still a "dead zone"? Why would their society want to venture out into that wasteland? If it's still a "dead zone", they can't farm outside, so what do they have to gain?

I suppose they could finally discover the cause and develop an antidote. If the antidote is expensive enough to produce (and/or requires constant re-application to keep the revived areas from returning to the "dead zone"), it would mean they could only re-inhabit small pockets of the wasteland -- the surface world on this continent becomes a vast desert pock-marked with tiny "oasis" towns and outposts. Life is hard on the surface, and the city then becomes the desirable place to be for the relative ease of life.

Alternatively, a band of scouts could, quite by happenstance, encounter a band of explorers from another continent trying to figure out what happened to everyone. In that case, it wouldn't take long for the city's scouts to learn that the disaster is actually quite localized, and now contact with the rest of the world enables trade, which opens the door for the city to, well, open their doors and re-emerge into the sunlight. Maybe they still can't grow anything in their "dead" soil, but at least it's not directly hazardous to human life, and between the city's resources and trade*, they can get what they need to live under the sun again. Life on the surface is, again, very hard, though, and the city is again the most desirable place to live, except for the hardy and foolhardy.

*What would they trade? Well, you've already established that the city has, in the intervening decades, developed pretty advanced divergent technology; this could easily give them material and/or knowledge to offer in trade for food, supplies, etc.

[vicky_molokh]

Originally Posted by Kromey

New user here, thought I'd throw in my 2 cents. (Disclaimer: Very new to GURPS; I've read the Lite rules, I've ordered the Basic Set [currently being shipped], I've never played a GURPS game in my life; my RPG background is overwhelmingly D&D, although I did play a Paranoia game at a convention once...)

Thanks for jumping right in like that. BTW, at first sight I though the Line Editor Himself was replying. :)

Originally Posted by Kromey

[ . . . ]
(I'm not familiar with the tech levels (I mean, I know what they are, but I'm not familiar with what exists/doesn't exist at the different TLs), so I have no idea where astronomy would be, or if this is a reasonable scenario for your desired entry TL.)

TL6 is roughly 1800s-1930s tech (though I'm aiming at roughly 1920s in the context of this tread), TL7 is roughly after nuclear tech becomes possible (1940s+ equivalent), TL8 is 1980s+ equivalent.

Originally Posted by Kromey

*What would they trade? Well, you've already established that the city has, in the intervening decades, developed pretty advanced divergent technology; this could easily give them material and/or knowledge to offer in trade for food, supplies, etc.

I'm not even aiming at trade much, at least not as something 'must-have'. I do think some trade early on will help them expand beyond the underground city a bit at first. Also, mining! Their area is rich in various precious minerals (this is why the 'capital of mining' was established there in the pre-sealing centuries).

[Kromey]

Originally Posted by vicky_molokh

Thanks for jumping right in like that. BTW, at first sight I though the Line Editor Himself was replying. :)

Hehe, every time I see His Lineness's name myself, I have to do a double-take because I don't remember writing that!! :-P

Originally Posted by vicky_molokh

TL6 is roughly 1800s-1930s tech (though I'm aiming at roughly 1920s in the context of this tread), TL7 is roughly after nuclear tech becomes possible (1940s+ equivalent), TL8 is 1980s+ equivalent.

Sorry, I wasn't clear. I meant that I don't know how accurate astronomy was in these periods, so I don't know if it would be feasible to spot an asteroid, plot its course with any level of certainty, and declare that it would strike the planet.

How far out could 1920s astronomers see an Earth-bound asteroid? And how quickly could they calculate that it was, indeed, Earth-bound? And how accurately could they say that it would strike?

Maybe it's enough for them just to say it might strike, especially once the politicians got hold of it (recent events here in the US and elsewhere prove that politicians have no problem terrifying their people for political gain); then that small chunk happens to break off and decimates the local area, "proving" their worst-case predictions true.

Originally Posted by vicky_molokh

I'm not even aiming at trade much, at least not as something 'must-have'. I do think some trade early on will help them expand beyond the underground city a bit at first. Also, mining! Their area is rich in various precious minerals (this is why the 'capital of mining' was established there in the pre-sealing centuries).

If they're going to grow beyond their city into a wasteland they can't farm, trade will be essential, I think -- their population will be growing as their territory does, and they'll have to feed those people, easily and quickly exceeding whatever food generation capabilities the city might have.

They'll have to trade for food and other essentials at some point, unless they limit their total population to just what the city can support.

Or maybe you're looking to start your campaign just as they're unsealing the vault? Or very shortly afterwards? In such case trade wouldn't be essential for them -- yet. Potential plot point for the PCs to negotiate opening trade discussions with their neighbors perhaps?

[Fred Brackin]

Originally Posted by Kromey

Sorry, I wasn't clear. I meant that I don't know how accurate astronomy was in these periods, so I don't know if it would be feasible to spot an asteroid, plot its course with any level of certainty, and declare that it would strike the planet.

How far out could 1920s astronomers see an Earth-bound asteroid? And how quickly could they calculate that it was, indeed, Earth-bound? And how accurately could they say that it would strike?

Dififcult to say but not that much worse based on the telescopes. The biggest telescopes avaialable took a jump with the 5 meter Palomar mirror in the 40s and have exploded by leaps and bounds since the 80s but those aren't the ones you use for asteroid spotting. Much smaller telescopes are used for that.

How far is at least 5 AU or the orbit of Jupiter as the so-called "Trojan" asteroids were discovered well before the 20s.

The problem is happening to look in the right place at the right time. There has been some effort ot systematize the search for Earth-grazers in recent years but a lot of it is still amateurs with modest instruments hunting for comets because .....well, you get to name comets after yourself. See Shoemaker-Levy-9 as just one example. Odds are stil high that no one sees it in time.

The complexity of the math isn't a problem. Chandrasekhar was (correctly) doing math for fundamental nuclear physics and stellar evolution in the 20s. See "Chandrasekhar's Limit" in any astronomy text. Orbits are way simpler by multiple centuries.

[vicky_molokh]

Originally Posted by Kromey

If they're going to grow beyond their city into a wasteland they can't farm, trade will be essential, I think -- their population will be growing as their territory does, and they'll have to feed those people, easily and quickly exceeding whatever food generation capabilities the city might have.

Why? By TL9ish, they can simply build more aeroponic farms at the new colonies. The problem is actually in how fast they can build all the infrastructure to support the colonies, not in some sort of hard cap.

Originally Posted by Kromey

Or maybe you're looking to start your campaign just as they're unsealing the vault? Or very shortly afterwards? In such case trade wouldn't be essential for them -- yet. Potential plot point for the PCs to negotiate opening trade discussions with their neighbors perhaps?

Nah, the campaign is set no less than a decade after the unsealing. Perhaps two to three decades. And the Justicariate is just one of the many states in the world (though an internationally notable one).