Suppose a 20kt bomb explodes in a major metropolitan area just as people are waiting on a subway platform underground.
Aside the possibility/likelihood of tunnel collapse, how safe are people from the fireball and blast effects: subway entrances/exits are not hermetically sealed hatches, so flame and compressed air could shoot down those stairwells.
Depends on way too many factors. Including the depth of the platforms and distance from burst.
Even if they survive, they might be screwed, having no way out.
In the event of multiple nuclear missiles striking the U.S., I prefer my location to be ground zero.
I don’t have any answers, but a lot of it will depend on depth below ground, and the configuration of routes to the surface - if the way down to the platform has lots of tight bends and zigzags, that will provide some attenuation of blast waves - and if there are places where there is a straight tunnel through, and the side tunnel to the platform branches off at more than 90 degrees (that is, you have to turn sharp right or left to get into the tunnel that leads to the platform), there could be places where the blast wavefront mostly just goes past in the main tunnel.
ISTM that the likely outcome for anyone down there who survives the blast is drowning - all those interconnected underground tunnels running under major rivers and estuaries - they’re likely to collapse enough to prevent escape and let in water, but not collapsed or blocked enough to prevent the water going everywhere.
20 ktn? Pffft, that’s Nagasaki bomb level.
At a typical subway platform that is well underground, unless there is a nearly direct line of sight from the blast to the platform they’ll only notice some noise and the power going off.
And a bomb that small isn’t going to do any real damage to water lines and such unless for some stupid reason it’s set off right next to the ground unlike the standard air blast.
In terms of surviving afterwards, just wait a day or two until the dust settles and walk out with some cloth over your mouth being careful to not touch anything. Won’t take you long (a couple hours) to get to a fairly radiation free area.
The main issue will be your fellow humans doing stupid/crazy stuff in a fairly small area. Get out of that area and things look a lot better. Shoot, if you can walk 5+ miles in the right direction along the tracks right away you’re going to be fine.
Oh, I misread the OP to mean what would happen if the bomb itself was set off inside the subway. I was thinking that that would be a less than favorable event for anyone in the whole system.
There are also likely going to be buildings in the direct line between the point of the blast and the subway entrance. Yes, nukes can blast through buildings, but they will still attenuate the effects somewhat. A grain of sand can’t stop a bullet, but a whole bag of them offers pretty good protection.
Pyongyang built it’s subway system deep so it could be used as a shelter. 110 meters deep, 22.5 km long. That’s a big shelter in way you look at it. Probably 100% safe from the initial attack too, regardless of the size of the weapon.
I laughed at this. It’s probably correct, that 20 kiloton is a mere firecracker, but it’s pretty funny. Also, it wasn’t so funny for tens of thousands of Nagasaki citizens, but I suppose most of them were unprotected.
One thing these nuke calculators don’t tell you is what would happen to the skyscrapers with low yield nukes. Is 20 kiloton enough to knock them over if the weapon went off in Times square?
Sammy. The words laugh and funny do not fit in a sentence about nuclear weapons. Just doesn’t fit.
Don’t forget to chide ftg for his insensitivity, then.
The problems is less that superheated air or thermal effects would enter the underground areas than that the firestorm the blast will ignite will evacuate air out of the subways as the air at street level rises. Public subway systems are not sealed and require regular forced air exchange, and unless built specifically for civil defense are not going to protect against this evacuation of air, nor intrusion of radioactive fallout or water. Collapse, however, is unlikely except perhaps at entrances or in the case of a subsurface detonation. Subway tunnels are well-reinforced against ground shifting and the blast may not even be dramatic in the deeper tunnels.
BTW, a 20 kiloton TNT equivalent weapon is nothing to sneeze at. While that is only a ‘tactical’ size weapon in modern terms, it is large enough than an air burst at 1000 feet above 5th Aveune and 42nd Street in Manhattan would create a fireball that would engulf Midtown completely and send a fallout plume that would basically cover all of Queens and upper Brooklyn. It would completely destroy the downtown districtcs of most mid-sized American cities.
Stranger
Well, there would not be any flame, as such. The detonation produces the powerful EM flash that sets flammable stuff on fire, then the shock wave puts those flames out within a few seconds. If it is a typical airburst, you might be best off at the subway station directly under it, because all the concrete above you will absorb most of the EM and the blast wave will be almost entirely going away from you; further out, maybe not so good, but still, most of the damage will be above ground. If it is in the back of a Hertz rental truck less than a mile or two away, you are probably fucked.
There is a book that may come with a few fictional but plausible answers. Metro 2033 by Dmitry Glukovsky. There is also a really good video game made from the story. The game is loosely based on the book though, think “Island of Dr. Moreau meets Subway Station”
People would be able to survive for the long term given they have a way to get water from deep aquifers and somehow wrangle up pigs or livestock and bring them down into the subway for breeding, the biggest problem would always be exiting to scavenge and returning not-so-contaminated by fallout.
Breeding pigs underground wouldn’t solve any food problems-- Where would you get the pig food, then?