Patrick Disney, who runs the Talking Warheads blog, has a published an article in the Atlantic about the threat (or lack thereof) from EMP.  It is part of a broader paper he wrote in his graduate program.

Patrick asked to write something for the blog and, since Patrick is a nice fellow and EMP is an interesting topic, I agreed.  So, here you go!

There is a group of Washington policy specialists who put on a show every summer of which I enjoy being a spectator.  Each year this group proclaims that, far surpassing any other strategic threat facing America today, electromagnetic pulse (EMP) will be our country’s undoing.  Feature films are made, conferences are organized, and lobbyist breakfasts are shared.

But this year has witnessed a shift.  The message about the impending blackout has softened.  The jihadi boogeyman, who until recently was perched in a rowboat off the East coast ready to launch a scud, has vanished.  The new EMP monster under the bed is: solar weather?

NASA has warned that a significant solar event could take place during the solar maximum next year, with the potential to disrupt electronics on Earth. They’re taking the potential seriously enough that a group of scientists got together in June for the annual Space Weather Enterprise Forum (SWEF) to raise awareness of the threat to our technology-dependent society.  Organizations and individuals known for trumpeting the EMP threat to policymakers have also latched on, pointing to natural solar activity as the reason to protect the country’s electrical grid where previously their focus was on rogue ICBMs.  I have been puzzled, though, at what caused the sudden shift in messaging about the EMP issue.

It’s not in response to any blows landed by a counterattack from opposing interests.  To be honest, not a lot of folks have taken the EMP threat seriously enough to give it a thorough rebuttal.  Nick Schwellenbach from the Project on Government Oversight (POGO) is one exception, having penned the seminal beat-down in the Bulletin in 2005, which this blog duly covered. I myself have tried to dive into the issue as part of my graduate research, imagining various scenarios in which an electromagnetic pulse attack could seriously threaten the United States, its allies or its military.  And although I still maintain that EMP is, in general, a laughably overhyped “threat,” the issue deserves better treatment from the analytical community than it has gotten.

Shutting down “continental shutdown”

Mention EMP in Washington circles and you’ll likely hear about catastrophic failure of America’s electrical grid, or what some call “continental shutdown.”  [Mention EMP anywhere other than Washington and you’ll probably hear “That thing from Oceans’ 11?”]  In this scenario, a terrorist or rogue state launches a ballistic missile that detonates a couple hundred kilometers above Nebraska, which sends out a pulse of electrons that short-circuits regional power transformers continent-wide, which then causes fuel and food delivery to halt, which then causes millions to starve and the inevitable breakdown of society.  Next to zombies, EMP is one of the best horror stories around.

But this is by far the least likely scenario.  Imagine a terrorist who has somehow managed to acquire a nuclear warhead and an acceptable delivery vehicle with a range of a couple hundred miles capable of reaching an altitude of a couple hundred kilometers (essentially a modified SCUD).  Under what circumstances would a terrorist be unsatisfied with an old-fashioned, direct nuclear strike against a city?  If the goal is to crash the US economy, the terrorist could hit Wall Street; if the goal is mass social panic, hit a nuclear reactor.There isn’t a terrorist in the world who wouldn’t be content with killing hundreds of thousands of people and calling it a day.

Even if that weren’t enough, there are real reasons for an enemy not to be comfortable risking an attempt at an EMP.  For starters, the continental shutdown scenario depends inherently on cascading effects; as one key node in America’s infrastructure goes down, it is supposed to bring down others.  This sequence of events is complex and entirely unpredictable, making it impossible for the perpetrator to know how effective the attack will be in advance.  Furthermore, the effects of an EMP are not universal. The US first noticed that high-altitude nuclear detonations can produce gadget-frying EMPs after the Starfish Prime test in 1962, which knocked out street lights in Hawaii 800 miles away from the test. According to a 1989 Sandia National Lab report, however, only 1 percent of the lights went out.

When commissioned to do a study in 2007 by Instant Access Networks, the Sage Policy Group estimated the upper rangeof systems affected by an electromagnetic pulseto be around 70%; the lower range was around 5-10%.  That means that for any given EMP attack, somewhere between 5% and 70% of systems would be affected.  There’s no way to know for sure which end of that range it will actually be, making it much harder to pull the trigger in the first place.  And when the alternative is a direct nuclear strike against a city, why would a terrorist take his chances?


Infrastructure Percent of capacity damaged
Low case Mid case High case
Electric grid
Transformers 10% 40% 70%
Other 30% 40% 50%
Communications systems
Large 10% 20% 50%
Small 5% 20% 50%
All types 5% 20% 50%
Large 20% 45% 70%
Small 1% 2% 3%
Source: Charles Manto, Instant Access Networks


But that doesn’t mean it’s not tEMPting

The other, though far less well-publicized, scenario involves a state actor launching an EMP strike against the US’s superior (and technologically-dependent) military.  In 2005, the Defense Science Board created a task force to assess the military’s ability to function in post-Cold War nuclear environments.  In its report, the task force warned that a “general neglect of hardening as a requirement” as well as the shift to commercial-off-the-shelf (COTS) electronics have contributed to a growing fear that an EMP could seriously degrade the military’s operational effectiveness.  Therefore, as a way of degrading the capabilities of US troops massing on your border, an EMP could be an attractive option.

In fact, it’s an attractive enough warfighting tactic that General Norman Schwarzkopf was reported to have requested authorization to launch a nuclear EMP over Iraq at the start of the Gulf War.

Various constraints would have to be managed, of course.  For example the enemy would have to take care not to have his own critical technologies close enough to the blast that they too might be vulnerable.  Additionally, the decision to introduce nuclear weapons into a conflict with the US — even if there were no immediate casualties — risks eliciting a devastating US response, declaratory doctrine or no.  And of course, the US could repair or replace any damaged units relatively quickly, and would likely be more than willing to bear the costs of such a move because of that whole thing about a nuclear attack just launched against its forces.

All of this is to say that an EMP, though potentially damaging, would likely still not be a game changer for anybody facing the prospect of a war against the US military.


One big pain in the ASAT

With one potential exception.  So much of America’s advantage in today’s worldcomes from satellite technologylike GPS navigation, global communications, precision strike weapons, UAVs, and more.  What if an enemy carried out a high-altitude EMP detonation — like, really high — that could damage key American satellite systems?  Would that disable our ability to launch precision strike weapons anywhere we want and to communicate with assets around the world?

The short answer is no, but we reeeeeally don’t want to have to find out.

When a nuclear weapon detonates exo-atmospherically, it has two types of effects: long term and short term.  The short term effects are those you’d expect: blast, shockwave, fast-scatter EMP.  All of these propagate in line-of-sight, decreasing in strength over distance.  That means that, if a satellite isn’t directly close enough to the detonation — which most satellites would not be — it could escape relatively unscathed.

The potential danger to low-earth orbit (LEO) satellites comes from the lingering effects of a detonation.  A nuclear blast high up in the atmosphere increases the amount of ambient radiation already trapped in the lower of two radiation belts called the Van Allen belts.  When satellites are put in orbit, they are shielded against these naturally occurring radiation belts; the higher the orbit, the greater a satellite must be shielded because it will pass through more radiation on its way to its intended altitude.  For this reason, LEO satellites are not designed to withstand heavy amounts of radiation.

A problem arises from a high altitude nuclear detonation when the bomb raisesthe peak radiation levels in low Earth orbit — potentially by three or four orders of magnitude.   LEO satellites will therefore accumulate radiation damage much faster than they are designed for, meaning on-board electronics will degrade and the lifespan of the satellite will be drastically cut short.  These higher radiation levels encircle the Earth and can linger for anywhere from six months to two years.  Thus, even for satellites that are on the opposite side of the Earth at the time of detonation, their normal orbital patterns make them essentially swim in a pool of poison that shortens their operational lifespans.  In the words of a Defense Threat Reduction Agency (DTRA) study: “one low-yield (10-20 kt), high altitude (125-300 km) nuclear explosion could disable — in weeks to months — all LEO satellites not specifically hardened to withstand radiation generated by that explosion.”  Replacing these satellites quickly in the post-space shuttle era would be difficult or impossible, especially if Russia doesn’t feel like helping out our space program for some reason.

Fortunately, the US military possesses multiple redundant technologies that would preserve its core capabilities.  According to the DTRA study, if LEO satellites are degraded, satellite constellations in medium Earth or geosynchronous orbit may serve as workable substitutes and are out of the range of an Earth-based nuclear threat.  In addition, theatre capabilities like long endurance high altitude UAVs, wireless ground nets, and manned aircraft could be feasible alternatives for communications and tracking systems. Thus, the EMP would not eliminate the US’s precision strike capability, and nearly the entire range of options for a US retaliatory strike would remain intact.  However, the effectiveness of all US systems would not be guaranteed, and important civilian and military systems would likely suffer from limited bandwidth for months or even years after an exo-atmospheric nuclear detonation


Go forth and war-game

I’ll leave it to others to unpack the challenges to US deterrent credibility this sort of scenario poses.  But the prospects for an American response to an exo-atmospheric detonationare incredibly murky, especially when one imagines itin the context of a regional conflict that doesn’t involve the US,like India firing a stratospheric warning shot over Pakistan’s bow.  Plus, there are few other states that havemajor satellite holdings, making it difficult for the US to threaten in-kind retaliation.

All of this, in my humble opinion, makes for some great discussion about a fascinating topic.  So can we please stop with the Goldeneye nonsense now?