Wednesday, August 26, 2015

Why Worrying About Iran Getting the Bomb Is Silly

From Bulletin of the Atomic Scientists:

What would happen if an 800-kiloton nuclear warhead detonated above midtown Manhattan?


StormCchaser said...

It will be quite awhile before Iran can build an 800kt bomb, as that would have to be thermonuclear - a more difficult technology than fission.

But... even with a fission nuke, they could destroy our society by setting it off above the atmosphere near the center of the US. The resulting EMP (technically HEMP - High altitude Electromagnetic Pulse) would destroy our power grid (and lots of other electronics). It would take 6 months to a year to get it back sort-of working, because a whole bunch of gigantic, custom made transformers would have to be manufactured overseas and then transported here. By that time, most of us would be dead.

North Korea already has most of the technology to do this, except perhaps for the long range missile and a small enough warhead. In this scenario, the warhead does not even have to be hardened to survive re-entry, because it doesn't re-enter - it detonates first.

This scenario is unfortunately treated as science fiction by too many folks. But... the government put out a detailed technical report on the subject that lays it out clearly. There is also precedent - a high altitude nuclear explosion back in the '50s above Johnson Island took out power in Oahu, Hawaii - 1000 miles away. That evening, my father and I were monitoring short wave radio to hear the effects - he was a nuclear weapons designer and ionosphere expert.

The reports are at .

Yes, I said "destroy our society" as in many tens of millions of deaths - perhaps as high as 250,000,000.

David aka True Blue Sam said...

The hope during the Cold War was that the Russians did not want to be destroyed along with us. The muslims do not care if they die destroying us. I have no hope that we will avoid this.

David aka True Blue Sam said...

My dad's brother was in England during the Cold War practicing the delivery of thermonuclear bombs with Voodoos. He tells me that the delivery was done from a vertucal climb after a below-the-radar approach, roll and run while the bomb goes up, and comes down on a chute. They figured out that the flash would melt their control surfaces. Suicide Mission. They practiced anyway to keep it from happening. If they flew that mission there would be nothing to come back to, anyway. This is about the time the Beetles came along. My cousin was a little boy in England at the time, and he loved them before I ever heard of them. We are so darn lucky to be alive today.

hga said...

To the extent there's saving graces about the EMP danger, the last time I looked at the technical details, it would take 3 warheads to cover the continental US, which significantly increases the difficultly of a state like Iran successfully pulling it off.

Nuke based EMP is also something we don't have a lot of hard data on, although the ex-Soviets were thought to have a lot more.

StormCchaser said...

Take a look at the link I gave.

As you say, there are some unknowns. But the physics is believed to be pretty well understood. The US proximity to the magnetic north pole makes the problem much worse, btw. I believe the US did two high altitude tests, and the Soviets one or two. As you get farther from the hypocenter, the effects diminish. However, they are pretty constant over a quite large area - pretty much anywhere the upper atmosphere is visible from the point of detonation. I don't remember the extent of the magnetic disturbance - it might extend even farther. But under the ionization disk in the upper atmosphere, the whole area is subjected to a very fast rise-time (<1nsec) electric field pulse, plus other phenomena.

I remember a couple of the ways it hits the high voltage distribution system. The electric pulse can cause flashover - electric arcs within transformers that destroy insulation. The magnetic pulse can cause high surge currents and magnetic core saturation that results in destruction of the transformer windings. Just 100A of DC current on a major distribution line is enough to cause the transformer to hit saturation for part of the AC cycle.

My father knew that there would be some sort of interesting effects in the ionosphere. He didn't mention if he knew, in advance of Starfish Prime, whether it would do anything else. It might have been a security clearance issue, or more likely it just wasn't well known.

There is also another form of EMP which was discovered accidentally when someone forgot to connect an instrument at the end of a long cable tied to a chart recorder. It is generated directly by an in-atmospheric fireball. It doesn't have a wide geographic extent, but is enough to cause problems to nearby systems. I know that at least some military systems are hardened against that kind of EMP.