[kulkarnic]

The rational reason we don't build nuclear shelters anymore is because they're no longer effective. As weapon yields increased, it's become apparent that a concrete, underground hideout is not going to save you.

The irrational reason is that it's been 60+ years since atomic weapons were deployed, and we are confident the danger has passed. But really, there's plenty of weapons out there: http://www.motherjones.com/politics/2011/11/map-nuclear-bomb...

[hga]

Yields didn't really increase that much, there's a limiting factor where more and more of the energy released simply radiates out into space, and that's somewhere around 1MT as I recall.

A serious, concrete underground "hideout" will save you from anything but a really close hit; I can look up numbers if you want, but I maybe remember a good metric is 1MT and one mile of separation, requiring a less intense shelter. And a large fraction of the population can get by with much less, carpet bombing suburbia and exurbia was never going to happen, especially due to counterforce requirements and the Soviets believing that MAD was profoundly immoral and never buying into it.

[waynecochran]

An underground hideout was never going to save you if you were near enough to the blast -- I always thought it was more of a way to protect yourself from nuclear fallout -- wouldn't that still be a valid reason to build a shelter?

[kulkarnic]

Yes, you can save yourself from the fallout (which decays exponentially with distance anyway). Unfortunately within around 15mi, you're still going to get pretty bad burns, unless you duck into your shelter immediately after the explosion. That's where the early warning systems are useful-- you get 6-8min with an ICBM strike.

[Someone]

You don't need reinforced shelters against fallout; above-ground buildings will do fine, as long as they can be made reasonably airtight (as additional protection, one could provide for material to replace broken windows)

Also, I think most shelters would be far enough from blast areas to provide some protection.

Eizo Nomura (who, amazingly, doesn't have a Wikipedia page) was 170 meter from ground zero in Hiroshima, and survived (http://en.m.wikipedia.org/wiki/Atomic_bombings_of_Hiroshima_...)

Akiko Takakura was above ground at less than 300m and lived for 60 years.

Even though later bombs were much more powerful that makes it likely that shelters at the edge of the blast radius can save lives.

Not all of them, but any program to protect civilians is a statistics game.

All the construction in SF isn't 100% effective against earthquakes, either.

[ZanyProgrammer]

No, a shelter is a perfectly valid way of surviving a near miss-being 20-30 miles away, you'll want a shelter.

[hga]

More like 2.3 miles for a 1MT airburst, that's just for a 15 PSI blast shelter. If you're building these for real, with concrete and so on in a real Civil Defense program, that's easy. It's pretty easy, if you have the time, to build an expedient blast shelter with wood and earth that'll handle 15 PSI.

And most warheads are less powerful (see my other comments); using my handy "RAND" nuclear effects calculator from the back of my copy of The Effects of Nuclear Weapons, 15 PSI for the following weapon air bursts (targeting cities, not ground bursts against ICBMs etc.):

  500 Kt: 1.8 miles
  300 Kt: 1.5 miles
  100 Kt: a bit over 1 mile
   50 Kt: 0.85 miles

So we're really talking a mile or two, depending on the standards to which the shelters are built. 1 MT 1 mile requires 45 PSI, call it 50 per the above. Don't know how intense a real shelter would have to be, then again that's an uncommon threat level.

[Retric]

10,000 nukes * pi * 30mi ^2 = 28,274,000 square miles.

The lower 48 states are only 3,119,884.69 square miles if you inclde waterways. With just land it's only 2,959,064.44 square miles.

So, 10k nukes let's you carpet bomb the lower 48 and have one within 10 miles of just about every point. Focus on population centers and I suspect you could easily get 95+% of the population within 5 miles of a detonation.

[masklinn]

> The rational reason we don't build nuclear shelters anymore is because they're no longer effective.

The rational reason we don't build nuclear shelters anymore (which is not actually true by the way, Switzerland still builds them although they're not required anymore for private residences) is because there's very little chance of a massive nuclear war which is what they were for.

> As weapon yields increased, it's become apparent that a concrete, underground hideout is not going to save you.

Weapon yield has decreased, not increased. In the 50s, delivery was through bombers, you wanted big bombs because many bombers were going to be shot down so each nuke delivered had to pack as much punch as it could. Early ICBM had similar-ish issue, you had few inaccurate rockets and they had a warhead each so each warhead had to count, you built a big rocket and a big warhead on top of it, and the ones that didn't fail and weren't shot down razed a city even when they missed it by tens of miles. That's where you had multi-megaton designs

With the 60s and MIRV multi-megaton went online (they'd been designed in the 50s) but systems designed in the 60s and deployed in the 70s for the exact same role all went sub-megaton, half a megaton at most, usually less, for smaller and more precise delivery platforms and MIRV systems.

The most numerous warhead in the US nuclear arsenal is the 100kT W76.

[ErikRogneby]

Here is a pretty well built companion tool for looking at blast radius. http://nuclearsecrecy.com/nukemap/

[jules]

That does not make logical sense. For any given nuclear weapon that doesn't kill the entire planet there is a range from the epicenter where a bomb shelter is effective, regardless of weapon yield. Yes, the area where people are killed even if they are in a bomb shelter is larger, but the area where people are saved by a bomb shelter is larger as well.

[dba7dba]

Some may disagree but the reason we did not have WW3 was because of nukes. Had there been no nukes, I firmly believe we would've had WW3 (or even WW4).

Because both leaderships of US and USSR knew starting WW3 would mean end of civilization on the planet, they controlled themselves.

[alan_cx]

I thought that was the whole point of building lots of nukes on both sides. They called it MAD, mutually assured destruction.