This is one of the first sections in a book I was writing on how to survive a nuclear exchange. The book was only intended for my own family and a few close friends … and only to be sent to them if it looked like a nuclear war was likely. And, only because, given how relevant it is to my own knowledge base, I felt I ought to have an answer, if they did ask me for advice … and I knew how I would feel if I had nothing to say.
2.1The flash (first seconds)
Fig 1: Relative heat intensity of the flash over relative time (seconds). The time is approximately in seconds for a 1mt explosion. Larger explosions last longer, with each 10fold increase in size there is a 3fold increase in length.
If there were an unexpected nuclear attack, the first anyone would know of the explosion, is an extremely bright, but totally silent, flash of intense heat and light.
DO NOT LOOK TOWARD THE FLASH!
If the first thing you know about a nuclear explosion is the intense light, then you must hit the ground, face down, immediately. Don’t look at the flash. Hit the ground and close your eyes.
If you are still exposed to the heat, cover bare skin and try to get to shade. If you have even a few second’s warning use this to get behind cover so you are not exposed to the flash.
Rationale: The reason to follow this advice is that many of the survivors of the atomic bomb in Japan mention that they had been taught to to drop to the ground this and that is what they did. The reason this works is that in a nuclear explosion anyone who is exposed to the flash could suffer extreme burns. As fig 1 shows, most of the heat energy of the initial flash energy arrives at the beginning. For a 1mt explosion, a third of the heat arrives within 1second.
With a reaction time of 0.3seconds, and a time for gravity to bring a person to the ground of 0.6seconds, the fastest anyone can “hit the deck” is about a second. So for a 1mt a third of the injury from the flash occurs before you have any time to react. Think about it for a second, choose to move and not drop, and you’ve doubled your potential injuries. You cannot afford to wait. There is no time to think. There is no time to weigh up the options. Your best hope is to use the fact that the closer you are to the ground, the more shielding you get. Because even plants, walls, chairs, desks, cars on the street, even small changes in the surface will shield you. You could reduce your exposure by 70% which would change third degree burns into something more akin to bad sun burn. If you think about it for even one second, you have lost the opportunity to make a substantial impact. If you start running, you will never get anywhere quick enough to effectively reduce your exposure to the initial flash.
My comment
After a discussion on another forum about the best approach and whether a “table” would provide protection I made this comment:
It’s an extremely difficult problem, because any response has to be done extremely quickly, so basically “drilled” and done without thought. I took the approach of “what action can make the most impact in improving survivability for the most people”. And, what most people can do, is reduce their exposure to IR, which will cause third degree burns (likely to lead to a slow death). The other key thing is to preserve sight. Because anyone blinded by the flash is far more likely to die afterwards.
Most people will be in one of three places: in bed, in their living room, or in an office. The ideal thing is to “look around for shade” … by which time they are blind. The only universal fall back that works in most places is “hit the deck and don’t look” (looking is quite hard when you’re on the deck)
If you take into account acceleration from gravity and reaction time, most people can be down on the ground in about 1sec. Ask them to think and that time probably doubles, doubling the initial injury. Hitting the deck doesn’t guarantee protection, but it doesn’t make the situation worse than not hitting the deck.
Once down you can then think … and then crawling or rolling into shade is the best way to move. But you have to be able to see to know where the shade is. And, if you did not hit the deck, you will have looked and won’t be able to see.
In the survival zones, the blast wave will arrive toward the end of the flash (or later). My bet, is that most people will be completely stunned by the event, partly blinded by the light, in severe pain from the IR burns and basically incapable of doing anything more. The blast wave will hit … the wave is a tsunami of debris that is flung horizontally at any wall or through any opening . So “hit the deck” is likely to be all most people actually do before the blast wave. The only general guidance is to be “low down” (below a window sill) where there is generally more protection.
After the blast wave, comes the reverse suction … where everything is pulled back and then things begin to fall out the blast wave tsunami. At that point, there may be parts of walls carried by the blast wave falling through the roof. At any point after the blast wave arrives, a wall may collapse and you want something like a desk over your head.
Addendum … close to the detonation, you can reduce the high energy radiation exposure in various ways. You might also factor in that an air blast “looks down” and so a window sill isn’t a great barrier. But close to the detonation, you are toast whatever you do. There is no point advising someone to do change their behaviour when it doesn’t change the outcome.
