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What you need to know about EMP weapons

6 June 2025

As we sit, possible poised on the verge of a nuclear conflict in the Northern Hemisphere,
maybe it’s time to look at the damaging effects of the electromagnetic pulse that follows
a nuclear detonation.

Apparently, if a nuke is deployed at high altitude, the EMP produced can have some rather
nasty effects on our delicate electronics below.

You can also forget about the inverse-square law to protect you because some components of
the EMP are not “point source” but actually generated by the interaction of gamma radiation
with the earth’s magnetic field. That produces a very large area of EMP which creates
high flux-levels at ground-level, even though the detonation may be tens or hundreds
of Km away.

For this reason therefore, it strikes me that we should all know a little more about
EMPs and ways we could hopefully mitigate the damage they cause.

Apparently there are three phases to the way a nuclear detonation produces an EMP.

However, it’s kind of reassuring to know that nukes detonated at or near ground level don’t
produce nearly as much EMP as those detonated at 30Km or so above the planet’s surface. To be
truly effective, a nuke designed to disrupt or destroy infrastructure by way of EMP has to
be exploded pretty damned high so direct radiation and thermal damage won’t be much of a risk.

During the first phase (known as E1), the detonation creates massive levels of gamma radiation which
interacts with the upper level of earth’s atmosphere to strip electrons from the rarefied
gasses there and subsiquently induced massive currents (known as a Compton current)
that creates a magnetic pulse with an extremely fast rise-time, typically 10nS or less.

The result is a burst of EM energy that spans the spectrum from near-DC to tens of gigahertz
and which induces currents in any conducting material that gets in its way. The earth’s
magnetic field also helps contain this burst of energy, meaning even more of it ends
up directed towards the surface of the planet.

This first phase is what’ll fry your computer, your phone and any other sensitive devices
that are not adequately screened from the EMP energy being produced.

After the first phase begins to subside, the second phase (E2) becomes prevailent and that sees
the spectral composition of the EMP change markedly. Now most of the energy exists in the
Khz to low Mhz range. This is because the Compton current has now stabilised somewhat
and is changing less rapidly than in phase 1.

While the E1 phase lasts just microseconds, E2 lasts anywhere from hundreds of mS to as long as
several seconds. Fortunately the reduced intensity and reduced spectral range of E2 means that
it’s easier to protect against.

The third phase (E3) can last anywhere from several minutes to tens of minutes and has a much
lower average frequency, typically no more than a few Khz.

This is the phase that is likely to cause issues with longer conductors, such as power lines,
pipelines and other long runs of metal. This phase could cause damage to transformers,
switching equipment and other vital pieces of energy infrastructure. It can also cause fires
as a result of arcing and localised heating within conductive structures.

So that’s the bad news, what can we do to mitigate all this EMP energy?

The primary tool is the Faraday cage — or a variant thereof.

In its most effective form, this consists of placing the gear to be protected
inside several layers of conductive material, each separated by an insulating layer. This works
by converting the magnetic fields generated by the EMP into currents within the conductive layers
and those currents automatically create a magnetic field that opposes the EMP energy which creates
them. Simple eh?

There are some caveats however.

Firstly, the conductive layers must be free from gaps or holes. During E1 the frequencies are so
high that even small gaps,cracks or openings could allow enough energy through that the delicate
electronics inside might be fried. This is another reason to use multiple layers — so that
any access holes can be staggered layer upon layer such that there’s no direct path for energy
to slip through.

Secondly, the devices being protected must be totally enclosed. No power leads, antennas or other
wiring must be left outside the shielding.

Thirdly, the device being protected must not be in direct contact with any of the shielding material
or the currents that flow in that material could also flow through the device itself.

So what happens if you’re told there’s going to be a nuke going off next door and you want to protect
your new Nintendo Switch2 so that during the nuclear winter that follows, you’ll at least be able
to play some games to while-away the time while your hair falls out?

Well wrap your Switch in plastic film or bubble wrap. Then wrap that in aluminium foil, making sure that
the ends are folded over and pressed down hard to provide good inter-layer contact and so that there
are no gaps. Then… more plastic, more foil, more plastic… etc… until you either get tired or
run out of materials.

That’s it.

Put your sunglasses on, apply some sunscreen, place your head between your knees and relax until
the debris has settled.

Mario… here we come!

Also, be annoyed that thanks to ever-shrinking fab technologies and the fact that so much of our
gear is now infested with microprocessors, the damaging effects of an EMP will be far more brutal
than they would have been backin the 1950s or 60s.

If you’ve got an old Morris Minor then chances are that it’ll still run just fine as the ash is falling
but that new Toyota Prius… not so much.

If there’s an old valve radio in the shed somewhere, it would also keep running just fine (if there
was any mains power) but without the bubble-wrap and foil it’s most unlikely that any of your
modern solid-state electronics will be anything other than ewaste.

Happy days!

Carpe Diem folks!

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