[orbital-decay]

>ZERO have ever been tested

Wait what? There were specific nuclear EMP tests. And sure, in any realistic nuclear war scenario EMP is just an unpredictable byproduct like your link says, but that doesn't make it fantasy I believe?

[irjustin]

I wonder if the parent is talking about pure EMP without the nuke because those are pure fantasy. Kill all electronics w/o all the fallout.

[jonathankoren]

No. That’s not what I mean. I’m talking about big boogeyman of an EMP attack that destroys the either the North American electrical grid and assorted electronics or merely all electronics in a city.

There is no nonnuclear EMP weapon. Every proposed EMP attack is literally a hydrogen bomb delivered via an ICBM and detonated at extremely high altitude. That is the only way to deliver one to the proper place and the only way to deliver the required energy. That’s just the physics. Even then, the actual effect at ground level, is unpredictable because of simple shielding and atmospheric turbulence. But the undetermined effects aren’t what makes an EMP fantastical. It’s fact that it’s delivered by an ICBM!

The premise of an EMP attack is that somehow the attacker could surprise their enemy and land a catastrophic knockout blow near instantaneously (where “instantaneous” is defined as “between 10 and 30 minutes” (i.e. the flight time of either an SLBM or ICBM)) with little to no retaliation. A Launch on Warning policy (i.e. launch a retaliatory strike when an incoming missile is detected in the air) along with ground and space based surveillance systems makes attempting to execute an EMP attack suicidal.

Missile launch detection systems have been operationally deployed and maintained since the 1960s. They work. Launch on Warning has been the policy of the United States since the 1960s. Implicit in a LOW policy is that the retaliatory strike order is given in minutes from a detected launch. This means the retaliatory nuclear weapons are already sent on their irreversible course before any incoming detonation occurs. This is the defense posture a hypothetical EMP attacker is lobbing an ICBM into. This isn't fantasy. This isn't just math. It’s the explicit nuclear posture of the United States for the past 60 years. It’s what makes Mutually Assured Destruction (MAD) work, and arguably has maintained peace between nuclear states for 70 years.

If an attacker has decided to launch a nuclear laden ICBM they just started a full on nuclear exchange, because that’s the response. No one is waiting to see where it goes. It’s “The missiles are flying. Hallelujah, Hallelujah.” Now. Given that you’re in an inevitable nuclear exchange, is it reasonable to waste a nuke on a roll of the dice on whether it actually do anything when you could actually blow something up? Nay! Knowing that you are being blown up?

On a related note, this is the exact situation why the proposed Prompt Global Strike weapon is suicidal. An ICBM armed with high explosives, looks exactly like an ICBM armed with nuke. Similarly, a kinetic energy hypersonic glide vehicle is not suicidal specifically because it doesn’t travel on a ballistic arc.

[orbital-decay]

> Even then, the actual effect at ground level, is unpredictable because of simple shielding and atmospheric turbulence.

https://en.wikipedia.org/wiki/Soviet_Project_K_nuclear_tests

>EMP ran to thousands of amps, damaged at least 570 km of telephone lines, 1000 km of buried power lines, and caused the destruction of the Karaganda power plant.

A 300kt blast at 290km was able to induce 1.5 to 4.5kA in the unshielded power line buried underground at 2m, over the area hundreds of kilometers across. Imagine what it could do to the areas that are a bit more populated than Kazakh steppes in 60's.

So yeah, while the nuclear EMP is probably not going to be used as a primary weapon in a global nuclear strike as you said, it's not a huge stretch for one of the warheads to be dedicated for the EMP over some large but less important area, not necessarily as a decapitating strike, so preparing for it makes sense. Besides, there would be at least local EMPs in the area after the "ordinary" nuclear strike, which can be really disabling if unprepared for.

[TTorler]

> literally zero nuclear weapons have been detonated at high altitude https://en.wikipedia.org/wiki/Starfish_Prime

[krisoft]

Yeah. So you are probably correct that it is unlikely that someone only sends a single warhead to do an EMP attack. What I don't understand is why you would think that it is unlikely that they send their whole volley, and some warheads are programmed to hit targets while some others are programmed to detonate to maximise EMP damage.

Sure there is MAD, but if you are a military leader would you like to hang your hat entirely on that? After armageddon when you climb out of your bunker would you like to be the one who still has tanks to command, or the one who can't command anyone because all your radios have fried?

[wnkrshm]

Regarding your other comment: why wouldn't a high-altitude detonation, even outside the atmosphere cause an EMP? I feel like the gamma photons emitted in space will eventually hit the atmosphere and with that cause electrons to spiral along field lines. Isn't the question just one of intensity?

Or is it largely dependent on multi-photon interactions to impart enough impulse on the electrons?

[helpfulContrib]

>There is no “fallout free” EMP.

False. There are non-Nuclear EMP's, and the USA even has a bit of experience with the Russian variants ..