Escape From L.A. Goldeneye. The Matrix. Ocean’s 11. The Fate of the Furious. These are but a few of the many popular films to feature electromagnetic pulse, or EMP. As depicted in these films, EMP is the ultimate weapon of the electronic age, able to destroy every electric or electronic circuit within its blast radius and plunge entire cities or even countries into the Stone Age. But is this terrifying weapon real, or is it just another pop culture fabrication, designed to provoke the same primal fear as when the wifi signal goes out? Incredibly, EMP weapons do indeed exist, though perhaps unsurprisingly their design, use, and capabilities are considerably different from what Hollywood would have us believe.

An electromagnetic pulse is a powerful burst of electromagnetic radiation, and can be generated by a variety of natural phenomena, including lightning strikes, falling meteorites, and coronal mass ejections or solar flares. Such pulses damage electrical and electronic equipment by inducing powerful electric currents, the wiring within the equipment essentially acting as a radio antenna. This current then overloads vulnerable components in the circuit. While the effects of lightning-generated EMP is typically minor and short-range, solar flares can cause significant damage to electrical infrastructure. In 1859, a large coronal mass ejection known as the Carrington Event knocked out telegraph networks around the world, causing telegraph poles to spark and giving telegraph operators electric shocks through their headphones. In certain areas telegraphs were even able to function without batteries, the power being supplied by the electromagnetic pulse itself. It is fortunate that this event took place at a time when earth’s electrical infrastructure was limited to telegraph networks; had it occurred today it would have wrought untold destruction. Thankfully, there have been no Carrington-level events since, though a 2012 solar flare of the same magnitude came very close, missing the earth by only 9 days.

In today’s digital age, the ability to instantly disable an enemy’s electrical infrastructure would give an attacking army a huge advantage on the battlefield, and so since the 1950s research into EMP weapons has been ongoing in several countries. Real EMP weapons fall into two basic categories: nuclear and non-nuclear. Nuclear EMP results from the intense burst of gamma radiation emitted by a nuclear explosion, which strips atoms in the surrounding air of electrons. These free electrons then flow along the earth’s magnetic field in what is known as a Compton Current, which in turn generates a powerful electromagnetic field. This phenomenon was anticipated by the scientists of the Manhattan Project, the WWII effort to build the first atomic bomb, and in the lead-up to the July 16, 1945 Trinity Test – the world’s first nuclear detonation – Italian physicist Enrico Fermi ordered all instruments monitoring the test double-shielded to protect them from damage. However, the EMP generated by a ground-level nuclear blast is relatively weak and short-range, and thus of limited utility as whatever electronic equipment is disabled by the EMP is immediately destroyed by the blast itself. This is because the high atmospheric density and weak magnetic field  at low altitudes prevents the free electrons from travelling far before being scattered, limiting the strength of EMP that can be produced. In order to generate a truly powerful and effective EMP, nuclear weapons must be detonated at extremely high altitudes, where the atmosphere is thinner and the earth’s magnetic field stronger.

This phenomenon was first observed in 1958 during Operation Hardtack I, a series of 35 nuclear tests carried out in the Marshall Islands in the South Pacific. Three of these tests, codenamed Yucca, Teak, and Orange, were conducted at high altitudes. The 1.7 kiloton Yucca device, carried by a helium balloon, was detonated at an altitude of 26 kilometres on April 28, 1958, while the 3.8 megaton Teak and Orange devices were launched aboard Redstone ballistic missiles, detonating at an altitude of 76 and 41 kilometres on July 31 and August 11, respectively. These tests were intended to determine the effectiveness of high-altitude nuclear explosions as a defence against incoming enemy ballistic missiles and to gauge the effects of the resulting electromagnetic pulse on communications equipment. The results were alarming, with the EMP exceeding predictions by more than fivefold and causing extensive damage to scientific instruments.

The most dramatic demonstration of the power of EMP, however, took place four years later during Operation Fishbowl, another series of high-altitude nuclear tests carried out in the South Pacific. These tests were conducted at much higher altitudes than the Hardtack series and were intended to study the creation of an artificial radiation belt around the earth that could potentially disable enemy nuclear warheads as they reentered the atmosphere. On July 9, 1962, the 1.4 megaton Starfish Prime was carried aloft by a Thor ballistic missile, detonating 14 minutes later 1100 kilometres above Johnston Island. The flash from the detonation was so bright it could be seen through heavy cloud cover in Hawaii some 1,500 kilometres away, while the radiation emitted by the blast caused the sky to light up with bright, multicoloured aurora. But as in the Operation Hardtack tests, the power of the EMP generated by Starfish Prime exceeded all predictions, wreaking havoc on Hawaii’s electrical infrastructure. More than 300 streetlights were knocked out, burglar alarms were set off, and the microwave telephone relay links between the Hawaiian Islands were severely damaged. Many scientific instruments, ships, and aircraft monitoring the test were also damaged by the pulse. Though the United States Military never formally admitted to the incident, it did not take long for the people of Hawaii to make the connection between the sudden blackout and the recent nuclear test. Meanwhile, the artificial radiation belt generated by the explosion orbited the earth for months, damaging several spacecraft including Telstar 1, the first telecommunications satellite, and Ariel, the United Kingdom’s first satellite – and for more on this please check out our video That Time the U.S. Accidentally Nuked Britain’s First Satellite.  

Two months later, the Soviet Union conducted its own series a high-altitude nuclear tests, with equally dramatic results. Known as Project K, these tests were launched from the Kapustin Yar missile development site, the warheads travelling across populated areas of central Kazakhstan to the Sary Shagan Test Range. The largest of these experiments, known simply as Test 184, was carried out on October 22, 1962, the 300 kiloton warhead detonating at an altitude of 290 kilometres. In anticipation of the test, Soviet scientists instrumented a 570 kilometre section of telephone line, which was protected from overload by dozens of fuses and gas-filled overvoltage protectors. Despite these precautions, the EMP generated by Test 184 induced massive currents of up to 3400 amperes, fusing the entire length of the cable and burning out every single fuse and overvoltage protector. The pulse also started an electrical fire that destroyed the Karaganda power plant and shut down 1,000 kilometres of underground power cables running between the cities of Astana and Almata. Though never confirmed by the Soviets, it is believed that the blast also inflicted severe damage to the nearby Baikonur Cosmodrome, since for nearly two months following the test every mission launched from the site failed. The Vostok 5 and 6 manned orbital missions, originally scheduled for November 1962, were also abruptly postponed, and would not be flown until seven months later.

The Americans managed to conduct two more high-altitude nuclear tests, codenamed Bluegill Triple Prime and Kingfish, before the Limited Test Ban Treaty of 1963 put an end to all atmospheric nuclear testing. Nonetheless, the data collected during these tests allowed American and Soviet scientists to make a number of key discoveries regarding the effects of EMP. Among these was the fact that high-altitude nuclear detonations actually produce three distinct pulses: the E1 pulse, lasting one microsecond, the E2 pulse, lasting between one microsecond and one second, and the E3 pulse, which can last from tens to hundreds of seconds. While the E1 pulse is the most powerful of the three, the E3 pulse is the most dangerous to electrical systems, mimicking the effects of coronal mass ejections like the 1859 Carrington Event. Most fuses and surge-protection devices can withstand high voltages and currents if they are applied over a short enough period, and will thus likely survive the powerful but brief E1 pulse. The extended surge produced by the E3 pulse, however, will cause most of these devices to fail. The high-altitude nuclear tests also revealed that when it comes to EMP, bigger is not always better. While most of the American tests used thermonuclear warheads in the megaton range, Soviet tests revealed that smaller kiloton-range fission weapons are just as if not more effective at generating EMP. This is because the casings of thermonuclear weapons tend to be thicker, blocking the prompt Gamma Rays essential for EMP generation. The primary stage of thermonuclear weapons also tends to pre-ionize the surrounding air, further reducing efficiency. The ability to use simpler, cheaper pure-fission warheads theoretically makes EMP a very cost-effective weapon. Indeed, since the 1960s, nearly every nuclear-armed nation has developed some means of using its nuclear weapons to carry out an EMP attack if required. For example, when on January 25, 1995 a Russian radar station mistook a Norwegian atmospheric research rocket for an American Trident submarine-launched missile, the radar operators assumed the Americans were carrying out a preemptive high-altitude EMP attack to blind Russian defences prior to launching an all-out nuclear strike – and for more on this please check out our videos That Time the Moon Nearly Started World War III and Briefcase of Armageddon: the Exact Sequence of Actions Behind a Hypothetical US Nuclear Attack.

Yet despite their awesome destructive power, high-altitude nuclear explosions are hardly the most convenient or diplomatically desirable means of carrying out an EMP attack. This has prompted extensive research into non-nuclear EMP alternatives. From a technical perspective, generating an EMP is relatively simple, requiring little more than a powerful capacitor bank to store and discharge electricity and a specially-designed antenna to generate and direct the pulse. One of the most extraordinary examples of such a non-nuclear EMP generator is the Air Force Weapons Lab Transmission-Line Aircraft Simulator, or ATLAS I, constructed in 1975 near Kirtland Air Force Base in New Mexico. Also known as “Trestle,” the 120-metre long, 36-metre tall platform was designed to test the resistance of military aircraft to nuclear EMP, and can support the weight of a fully-loaded B-52 Stratofortress bomber. A pair of EMP generators can bombard the test aircraft with a Doc Brown-pleasing 200 Gigawatts of electromagnetic energy, accurately simulating the effects of a nearby nuclear explosion. Incredibly, as metal would interfere with the test results, the entire platform uses no nails, screws, or bolts, being built entirely using woodworking joints and glue. Using up 6.4 million board feet of lumber, it is still the largest all-wooden structure in the world.

Unfortunately, EMP generators like those used on ATLAS I are too bulky and heavy to be feasible combat weapons. Fortunately, there is a more compact alternative: explosively-pumped flux compression generators. First conceived by Soviet nuclear scientist Andrei Sakharov in the early 1950s, these devices convert the chemical energy of conventional explosives into powerful instantaneous electromagnetic pulses. At their most basic, explosively-pumped flux compression generators consist of a coil of wire surrounded by a shell of explosives. Just prior to firing, a bank of capacitors charges the coil, generating an electromagnetic field. The explosives are then detonated, compressing the coil and the magnetic flux in milliseconds and generating an electromagnetic pulse of up to 1000 Tesla – 200,000 times more powerful than an average fridge magnet. Unfortunately, the device is also destroyed in the process. Though originally designed for fusion and plasma physics research, explosively-pumped flux compression generators could theoretically be turned into EMP weapons compact enough to be delivered by a missile, air-dropped bomb, or – in the case of a terrorist-built weapon – a car. Such devices would be closer to those depicted in films like Ocean’s 11 and The Fate of the Furious. Compared to a nuclear EMP, however, the power of such weapons is extremely limited, with effective range being measured in hundreds of metres. On the other hand, such a precision weapon would allow small areas like individual buildings to be targeted, and could still knock out an entire city if detonated near a power plant, substation, or other vital piece of electrical infrastructure.

While it is unknown whether any nation currently fields an explosively-pumped EMP weapon, the United States does have at least one non-nuclear EMP weapon in its arsenal: the Counter-electronics High Power Microwave Advanced Missile Project, or CHAMP. A joint venture by Boeing, Raytheon, and the U.S. Air Force Research Laboratory, CHAMP consists of a high-power microwave emitter mounted in an AGM-85 air-launched cruise missile, and is capable of permanently disabling conventional civilian electrical and electronic equipment at close range. On October 22, 2012, a prototype CHAMP-equipped missile carried out a highly successful demonstration at the Utah Test and Training Range, knocking out multiple banks of computers and even the remote cameras monitoring the test. As of May 2019 the United States Air Force has deployed at least 20 CHAMP missiles, and while the details of the technology are highly classified, it is believed the weapons are based on compact particle accelerator tube called a Vircator. Raytheon is also developing a ground-based version of CHAMP for use against drones.

But what kind of damage can these weapons actually inflict, and are we at risk of rogue EMP attacks? As the high-altitude nuclear tests of the 1950s and 1960s clearly demonstrate, nuclear EMP can cause serious damage to electrical systems, whose vulnerability has only gotten worse as we have moved away from vacuum tubes towards solid-state electronic technology. Indeed, as bad as the damage inflicted by the Starfish Prime test was, it could have been significantly worse had Hawaii’s electrical infrastructure not been relatively crude and robust compared to modern technology. For this reason, right to the end of the Cold War a significant amount of military equipment on both sides continued to use more EMP-resistant vacuum tube technology. Ironically, as the world’s largest manufacturer of miniature vacuum tube was – and still is – Russia, this meant that a lot of NATO equipment ran on Soviet tubes. However, while EMPs in movies are capable of disabling every electronic circuit down to a wristwatch, in reality the damage would not be so fine-grained. As noted before, much of the damage from an EMP comes from the longer-lasting E3 pulse, but this requires long conductors like power lines in order to be effective. Small electronics like wristwatches and cell phones lack these long conductors and would likely be unaffected. Cars would also likely be spared, as they, too lack long conductors and are partially shielded by their metal bodies.

But the survival of our cell phones and cars would be small comfort next to the massive destruction an EMP would wreak on the electrical grid. In addition to being controlled by EMP-sensitive electronics, most national power grids are notoriously unstable and sensitive to even minor disturbances. For example, the great Northeast Blackout of 2003, which left over 10 million people without power, was triggered by a power line shorting out on a tree in Ohio. On March 13, 1989, a relatively minor solar flare with an intensity of 480 nanoteslas per minute caused the entire electrical grid of Quebec to collapse in 92 seconds; in contrast, the 1962 Soviet Test 184 that burned down the Karaganda power plant had an intensity of 1300 natoteslas per minute. According to a recent US Government study, a weapon of similar power detonated 500 kilometres over Kansas would generate an EMP covering most of the United States and likely damage more than 300 large power transformers, leaving around 40 percent of the U.S. population without electricity. And this would not be a temporary inconvenience; given the significant time and resources needed to repair this infrastructure, the blackout could last for as long as 4 to 10 years. For many Americans, modern life as we know it would come screeching to a halt, as analyst Peter Pry vividly describes in his 2017 report Life Without Electricity:

“Some experts claim that an EMP attack that collapses the power grid would, in effect, return society to a pre-industrial condition. A February 1987 snowstorm that blacked-out the Washington, D.C. area suggested exactly this to many of its victims. According to press reports, people were reduced to using open fires for heat, cooking and, in some areas, melting snow for water. Homes with fireplaces became havens for multiple families seeking refuge from houses heated by electric, gas, or oil that no longer worked. As she “stoked a fire and began sterilizing water for her baby’s formula,” one woman told reporters, “It’s like the Colonial days.”

In response to these vulnerabilities, the United States Government has formed numerous organizations to address the EMP threat, including the aptly-named Commission to Assess the Threat to the United States from Electromagnetic Pulse Attack. The Commission estimates it would cost between $2-4 billion to protect the most vital and vulnerable pieces of electrical infrastructure, though it also recommends redesigning electrical equipment to be EMP-resistant moving forward. However, despite the fact that nations like China and North Korea are known to be developing enhanced EMP weapons, according to analysts the threat of a conventional EMP attack remains on par with that of a regular nuclear attack – that is, relatively low. But what about a terrorist EMP attack? Thankfully, obtaining a nuclear weapon is extremely difficult, while launching it above the atmosphere is even harder, requiring rocket hardware that few nations even possess. And while a non-nuclear EMP like an explosively-pumped flux compression generator is theoretically much easier to build, many of the design details of these devices remain classified and it is considered unlikely that most terrorist groups would be able to build one. So if one day the power goes out across all across North America, don’t worry: it’s probably not the handiwork of terrorists or a slick gang of thieves. More likely it’s just some tree in Ohio.

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