in case of nuklear winter: when habitable?

If there was a massive nuclear exchange, lets say a Y21K problem :rolleyes: , how much of the earth would be uninhabitable? I.e., would nuclear “fall out” include radiation danger all over the place or just near the spots hit. Would the center of civilization move to Brasilia, or would they be screwed, too?

Air masses have a hard time crossing the Equator, so (assuming the present-day distribution of targets) the southern hemisphere would be largely spared. How much land total, in either hemisphere, was rendered uninhabitable depends on precisely how massive your nuclear exchange is, and on what your standard of “habitable” is. If it helps as a reference point, there are many people living in Hiroshima and Nagasaki today, and many modern bombs are actually cleaner than the two dropped on Japan.

Cleaner? :confused:

Modern nuclear weapons can produce much larger explosions, using much less fissle material, resulting in much less fallout. This is because a large portion of a modern weapon’s bang comes from fusion reactions, which are cleaner than fission one. The Little Boy bomb dropped on Hiroshima weighed about 9000 pounds, and had a yeild of 13 kilotons. In comparison, the W88 warhead used in the Trident submarine based missiles weigh only 800 lbs yet have a yield of 475 kilotons.

Of course, the big difference in fallout would depend on how many bombs were used in ground burst (which would be used to take on harded targets, and are messy) and air burst, which spread blast damage over a larger area, but don’t produce much fall out.

Cecil did a column on essentially this question:

http://www.straightdope.com/classics/a1_232.html

I’m only guessing here, but I would think that because most nukes today are higher yield, they are set to detonate much higher that the 2 WWII bombs. This would result in less interaction between the fireball and the ground, and thus less fallout.

More destruction and loss of life, certainly, but less lingering radioactive contaminants being created and also dispersed into the air.

Offestting that is the fact that some of these are in the multi-megaton range, which could produce a lot more contaminants even though detonated further from the ground.

That’s just my hunch. As to the bombs themselves being cleaner, I don’t know about that, other than neutron bombs, which supposedly are cleaner. But that’s a specialized case.

(hmm…I used all that verbiage in a GQ forum to basically say “I don’t really know.” Hopefully, there are enough points raised that I don’t get banned by the admins.)

They are. The early warheads were far more inefficient. Modern weapons use less fissile material and achieve greater yields with it, and thus, less fallout even in a similar detonation because of the smaller amount of bomb residue.

Gotcha, and thanks.

It should be noted, of course, that if fallout is your goal, it’s possible to make a weapon much dirtier than Fat Man or Little Boy. If you pack the warhead with various (otherwise stable and safe) isotopes, the radiation from the bomb will convert them to more dangerous isotopes and disperse them. Last I heard, all of the nuclear powers were officially denying that they themselves had such weapons, but publicly worrying that their rivals had them and were possibly planning on using them, so it’s hard to say whether any such devices actually exist. But they’re certainly possible.

Slap a cobalt case around it.

First of all, most modern nuclear weapons (in the US arsenal, anyway) are typically smaller than in years past. The reason for this is twofold; first, with the advent of MIRVs (Multiple Independent (or Independently-targeted) Re-entry Vehicles) it became desireable to stack as many smaller warheads on one ICBM as possible; and second, because the Minuteman III, Peacekeeper, and Trident D-5 have such high accuracy; all three have a CEP (Circular Error Probability) of under 120m, making them suitable for striking specific, hardened targets. And large devices, espeically for ground-burst targets like silos and underground installations, are terribly inefficient. The early H-bombs–the Mark 14, Mark 15, Mark 17, and Mark 21 at 7MT, 1.7MT, 10-15MT, and 4-5MT respectively, have significantly higher yields than the popular W/B-61 (which, in various mods, runs between 0.3 and 340kT). Current ICBM warheads are the W-62/Mk-12 and W-78/Mk-12A for the Minuteman III which vary from 170kT to 335kT, and the W-76/Mk-4 (C-4 and D-5 Trident) and W-88/Mk-5 (D-5), at 100kT and 475kT respectively. The largest deployed weapon the US ever developed was the Mark 41 at 25MT; AFAIK there is nothing in the modern arsenal, even as a nondeployed reserve, that is anywhere close to that yield.

Second, there seems to be a conflation here between radioactive fallout products and “nuclear winter”; one has nothing to do with the other. Fallout is caused by radioactive products of the bomb that are not fully decayed that attach themselves to debrisplus natural elements converted to radioactive isotopes via exposure to particle and gamma radiation. In an airburst situation there is obviously going to be little debris and relatively little concentrated fallout. A ground or near ground burst of the type that produces those beautifully hideous mushroom clouds will suck up ground material in a convection column, mix it with radioactive byproducts, and eject it into the atmosphere, to fall back to the surface. Modern boosted fission bombs and staged (thermonucluear or “hydrogen”) devices seek to minimize the needed mass of fissionable material to reduce both cost and weight. As Chronos, RandomLetters, and others have noted, this efficiency results in a radioactively “cleaner” explosion; the primary radioactive products will be produced via fast fission reactions from neutron radiation in the primary blast zone which will mostly decay within days. (Gamma rays will be largely absorbed by the atmosphere and converted into heat resulting in the thermal pulse, and the alphas and betas are only a small and relatively non-energetic portion of the radioactive yield.)

It is true that you can jacket a bomb with cobalt or other fissiable products to make it “dirty”; while the US and the former USSR (and presumably other nuclear powers) have developed this technology, I don’t believe anyone has at least publically acknowledged to placing it in deployment. Similiarly, the clean “enhanced radiation” (neutron) devices which were so feared (as they were considered to reduce the collateral damage of an exchange and therefore undermining the cataclysmic arguement beneath Mutually Assured Destruction) were not deployed as such, although a number of ER weapons made it into arsenals for a variety of non-anti-personnel missions (ABM warhead, EMP generator).

As for nuclear winter, caused by ejecta from ground bursts being suspended in the stratosphere and blocking sunlight, I expressed my opinion on the matter [post=6503586]in this thread[/post], the essense of which is that we don’t really know how extensive the long-term atmospheric affects would be, but that the popular conception, based on the TTAPS study, of an apocalypic freeze is probably overstated, perhaps massively so. Obviously, others disagree, although there’s no question that the methodology of the TTAPS study and subsequent studies using highly simplified models that don’t take into account climatological circulatory effects offer only a very limited understanding of the extend and duration of the effect. As Chronos notes, air streams don’t readily cross the equator, and given that the majority of targets for any foreseeable exchange would be in the Northern Hemisphere (so much for On The Beach) probably indicates that the Southern Hemisphere would be largely isolated from primary effects, though several climactic change in the North could have secondary effects that propagate to the South.

In short, we don’t really know how extensive the effects would be from a full-on exchange between major powers like the US and the USSR at the height of the Cold War. Certainly the primary effects on production, agriculture, and infrastructure would be devistating, as would short-term radiological and blast effects near target areas. We could certainly expect that the major players would be reduced to the status of second rate powers at best. Long-term radiological effects are probably much less than would be expected and limited to target sites; a slight increase in background radiation isn’t going to bring the human race to a halt. (We know this because we released masses of radiation over the American Southwest from very dirty atmospheric testing with only slight and debatable increases in chronic illnesses associated with elevated radiation. This probably says as much about the typical American lifestyle of the time–killing ourselves with fat, sugar, and tobacco–but indicates that even long-term exposure to moderate amounts of persistant elevated radiation levels isn’t as major a health concern as other lifestyle factors.) Climate effects are speculative at best; apocrypha regarding perpetual darkness is certainly exaggerated, but it’s possible we could suffer a year or a few of shorter, colder growing seasons and other attendant effects.

Fortunately (at least currently) while nuclear proliferation continues apace with every Samir, Al-Falud, and Kwan-Li trying to join the Big Boys Club, the massive arsenals of the major powers are being trimmed down to less devistating levels. The US has deactivated the last of the 10-RV Peacekeeper missiles, decommissioning Trident C-4 SLBMs, and is reducing Minuteman stocks to “minimum acceptible levels”, and the Russians are similiarly dismantling weapons (as much to save on the operational cost of older, maintainence intensive boosters) as well as just plain not having the budget to operate their ballistic missile submarine force. The possibility of a limited exchange between two nations continues to increase, but the likelyhood of a massive front and counterattack between superpowers is dwindling.

Stranger

Great post, Stranger! Thanks for writing it!

Your tax dollars at work. :wink:

Stranger

Stranger, thanks. But you didn’t cover avian flu. :wink: