[ufmace]

I'm not sure about most of this. The great majority of the articles and stories about this I've read trace back to layman speculation and disaster porn fiction written by people who have never claimed to actually be informed about how these things work. There's damn little stuff out there that traces back to actual experiments with real hardware. Probably most of the serious experiments are by various militaries and are highly classified. I've seen some more believable stuff suggesting that most consumer electronics and automobiles are not vulnerable at all to the much-fictionalized high-altitude nuclear EMP.

Either way, the author of this article does not cite any sources or relevant experience, and he doesn't include any biographical information about himself to judge how qualified he is to speak on such subjects. There's not much reason I see to take this any more seriously than any piece of fictional disaster porn you could buy on Amazon.

I don't know the truth for sure myself, but hopefully we all know better than to believe everything we read, especially about subjects like this where there appears to be very little hard science published.

[Animats]

There's plenty of unclassified info available. Start here.[1] This is an overview document from Defense Acquisition University, a unit of DoD. It's a painful PowerPoint. You have to plow through a lot of really boring military documents to get the details.

EMP doesn't address small devices much. Small devices with no wires connected are not very vulnerable, because the energy is mostly at somewhat longer wavelengths, meters or tens of meters. Worry about cell towers, not cell phones.

Other than the power grid people, the civilian sector doesn't look at EMP hardening much any more.

[1] https://www.dau.edu/sites/default/files/Migrated/CopDocument...

[timewizard]

> Worry about cell towers, not cell phones.

The grounding is usually required to meet a standard and is tested during the towers installation. There are also coaxial surge arrestors and isolators that get used along the span.

Some of the site to site communications equipment has no ground component other than a PoE switch. The ethernet interface, radio, and antenna are all in a single packaged unit installed at height on the tower.

[Animats]

That's a good point. Anything that is designed to survive lightning strikes also has considerable EMP resistance.

[resters]

Communications equipment is not designed to withstand lightning strikes. Lightning protection is meant to prevent the tower from melting or the building from burning down, not to protect a receiver!

[timewizard]

I'm not at all sure why you'd think that. Here's an actual product that sits inline with the coaxial cable and is absolutely intended to protect the receiver.

https://www.dxengineering.com/parts/ntk-pti-bb50nff?seid=dxe...

[resters]

Serious HEMP protectors are tested to MIL-STD-188-125 or IEC 61000-2-10

[ufmace]

I did run through the whole thing. It doesn't actually say anything at all about what is or is not vulnerable, it's just a bunch of military standards and procedure about how to test for things and what to test, and some vague stuff about potential ways to protect things and what large military hardware they'd like to test.

Curiously, all of the links people have thrown out in this thread seem to prove exactly what I said - there's damn little available to the public in the way of documented experiments on real hardware for EMP susceptibility.

I don't have any really solid cites for it offhand, but it has been my understanding that small devices aren't vulnerable. I don't know EMPs specifically, but I have been involved in standard EMI testing for approval of consumer-grade electronics, so I know there's already a fair amount of testing for and shielding against EM interference with everyday consumer electronics.

[hxorr]

I happen to be from the same town as this guy. He is well known for building his own ramjet-powered cruise missile.

I don't know about recently but he was actively involved in the local RC airplane club for quite a while if I recall correctly.

His website is well worth checking out, he has a very extensive technical knowledge.

[ufmace]

Okay, that's very cool! I don't mean to trash this guy at all, he may well be a real expert in some fields.

However, it is a failure mode that people who are really smart and qualified about one thing can assume they are equally smart and qualified about a bunch of other fields that require their own specific expertise. Alas, it doesn't work that way.

There's nothing wrong with not knowing about some specific technical subject. It is a red flag though when someone takes it as a threat to their identity and self-worth to acknowledge that they don't know much about some particular subject, even if they do know a lot about a different subject.

[hxorr]

I fully agree with you and have unfortunately seen this happen with a number of youtubers I follow as their channel and influence has grown.

[jvanderbot]

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

> Starfish Prime caused an electromagnetic pulse (EMP) that was far larger than expected, so much larger that it drove much of the instrumentation off scale, causing great difficulty in getting accurate measurements. The Starfish Prime electromagnetic pulse also made those effects known to the public by causing electrical damage in Hawaii, about 900 miles (1,450 km) away from the detonation point, knocking out about 300 streetlights,[1]: 5 setting off numerous burglar alarms, and damaging a telephone company microwave link.[6] The EMP damage to the microwave link shut down telephone calls from Kauai to the other Hawaiian Islands.[7]

This was a 1 Mt bomb 10x as far from the surface as the article discusses.

All that to say, it's plausible.

[jcrawfordor]

It should be understood that the largest impact of the Starfish Prime test, knocking out streetlights, was the result of a very specific design detail of the street lights that is now quite antiquated (they were high-voltage, constant-current loops with carbon disc arc-over cutouts, and the EMP seems to have caused some combination of direct induced voltage and disregulation of the constant current power supply that bridged the carbon disks). The required repair was replacement of the carbon disks, which is a routine maintenance item for that type of system but of course one that had to be done on an unusually large scale that morning. The same problem would not occur today, as constant-current lighting circuits have all but disappeared.

In the case of the burglar alarms, it is hard to prove definitively, but a likely cause of the problem was analog motion detectors (mostly ultrasonic and RF in use at the time) which were already notorious for false alarms due to input voltage instability. Once again, modern equipment is probably less vulnerable.

Many of the detailed experiments in EMP safety are not published due to the strategic sensitivity, but the general gist seems to be along these lines: during the early Cold War, e.g. the 1950s, EMP was generally not taken seriously as a military concern. Starfish Prime was one of a few events that changed the prevailing attitude towards EMP (although the link between the disruptions in Honolulu and the Starfish Prime test was considered somewhat speculative at the time and only well understood decades later). This lead to the construction of numerous EMP generators and test facilities by the military, which lead to improvements in hardening techniques, some of which have "flowed down" to consumer electronics because they also improve reliability in consideration of hazards like lightning. The main conclusion of these tests was that the biggest EMP concern is communications equipment, because they tend to have the right combination of sensitive electronics (e.g. amplifiers) and connection to antennas or long leads that will pick up a lot of induced voltage.

The effects of EMP on large-scale infrastructure are very difficult to study, since small-scale tests cannot recreate the whole system. The testing that was performed (mostly taking advantage of atmospheric nuclear testing in Nevada during the 1960s) usually did not find evidence of significant danger. For example, testing with telephone lines found that the existing lightning protection measures were mostly sufficient. But, there has been a long-lingering concern that there are systemic issues (e.g. with the complex systems behavior of electrical grid regulation) that these experiments did not reproduce. Further, solid-state electronics are likely more vulnerable to damage than the higher-voltage equipment of the '60s. Computer modeling has helped to fill this in, but at least in the public sphere, much of the hard research on EMP risks still adds up to a "maybe," with a huge range of possible outcomes.

[genewitch]

LEDs use constant current drivers, though. And even if you disagree, LEDs need to be current limited, so something will break with a large pulse of current, the driver or the LEDs themselves.

Maybe sodium lights are immune, in isolation?

[jcrawfordor]

the constant-current drivers in LED lighting are a very different concept from constant-current lighting circuits, which are a ~1920s technology rarely seen today. constant-current lighting circuits can be miles long, operate at up to 1kV or so, and require some type of cut-out/bypass feature at each individual light so that a failure of a single bulb does not take the entire circuit out. The problems that constant-current lighting circuits address (maximizing the life of incandescent bulbs) are all solved in different, more robust ways in modern lighting systems. Most significantly, the carbon-disc cutouts that were the direct cause of the street lighting failures are no longer used (even in legacy constant-current lighting systems, where they have been replaced with more modern devices).

[acidburnNSA]

Here's congressional testimony on the topic from a top Pentagon Weaponeer named Lowell Wood, who I can personally assure you is well credentialed in this area.

https://spp.fas.org/starwars/congress/1999_h/99-10-07wood.ht...

[ufmace]

Note that this testimony is a persuasive presentation, an effort to persuade congress to allocate additional spending for EMP protection. Mr. Wood may indeed be qualified to speak on the subject, but this aspect necessarily colors his speech. It's not like there's a shortage of cases of decently qualified people exaggerating the risks of something in order to get more funding and status for themselves and their pet programs.

What I'd really like is hard data on what is or is not actually vulnerable to these hazards and to what extent, based on hard proof rather than fear-mongering by interested parties, which this doesn't get us any further towards.