The sky is ablaze with the flash of the Starfish Prime nuclear test as seen from Hawaii. The test, performed hundreds of kilometres away, had a significant effect on electrical systems in the archipelago.

Unleashing the power of the electromagnetic pulse could be devastating for critical national infrastructure.

In late February, Rafael Advanced Defence Systems announced the selection of its BNET Electromagnetic Pulse (EMP) protected very/ultra high frequency (30 megahertz to three gigahertz) Land Mobile Radios (LMRs) by an undisclosed US power company. These transceivers are protected against the EMP’s crippling effects, which could cause major damage to Critical National Infrastructure (CNI).

Rafael’s news put the EMP threat into sharp relief. The EMP was an ever-present concern during the Cold War. The British Broadcasting Corporation’s chilling 1984 docudrama Threads depicted the devastating effects of a nuclear war on the United Kingdom through the prism of a nuclear attack on the city of Sheffield, northern England.

Shortly before the salvo of Soviet weapons visits atomic fury on the British Isles, nuclear weapons are detonated hundreds of miles above the country. In the film, these detonations were performed to exploit the EMP phenomena accompanying nuclear explosions.

The EMP is a powerful burst of electromagnetic radiation accompanying a nuclear blast. It is dangerous to electronics as the pulse can be conducted by antennas or power lines, for example, into equipment. The EMP can cause voltage surges in electronics which maybe powerful enough to significantly damage their circuitry.

In nuclear combat, using an EMP shortly before the arrival of the first salvo of weapons could damage the electronic equipment of one’s opponent. This may hamper their ability to retaliate, and to coordinate civil defence efforts in response to the catastrophic damage the incoming attack will cause. To put matters into perspective, open sources say that an EMP can have an equivalent power to 20,000 volts per metre (three feet), easily overloading consumer and industrial circuit breakers and safety equipment.

Rafael recently concluded a sale of its EMP-protected BNET LMR transceivers to a power company in the United States.

Starfish Prime

The power of the EMP was demonstrated time and again during the Cold War. Numerous nuclear tests performed by east and west studied the EMP. In July 1962 a US nuclear test codenamed Starfish Prime saw a W-49 1.44 megaton/MT (one megaton is equal to one million tonnes of conventional explosive) warhead lofted into space atop a Douglas PGM-17 Thor intermediate range ballistic missile.

The warhead detonated over the Pacific Ocean at an altitude of 217 nautical miles/nm (402 kilometres/km). The resulting EMP reached Hawaii, a distance of 782 nautical miles (1,448km) from the explosion. Street lights were damaged, burglar alarms activated and telephone microwave links severally disrupted. The US referred to this phenomena as a High Altitude Electromagnetic Pulse (HEMP) with the British calling it ‘radioflash’.

The Soviet Union also witnessed HEMP effects. On 30th October 1963 she detonated the AN-602 Tsar Bomba (King of Bombs) 57MT nuclear gravity bomb above the Novaya Zemlya archipelago in the Arctic Ocean. This remains the largest explosion in human history. Soviet sources said the blast was so powerful that the EMP caused disruption to radio communications several hundred kilometres from ground zero for almost one hour after the blast.

The end of the Cold War has not meant the end of the EMP threat. Nuclear weapons are owned by a handful of countries around the world. The strategic edge that the EMP brings to nuclear combat will be as integral to those states’ nuclear warfighting plans as they were during the Cold War. Meanwhile, the dependence that the military and civilian worlds alike have on electronics and communications will only deepen in the future. More people and organisations will enjoy the benefits emerging wireless communications protocols like 5G (fifth generation) and the Internet of Things will bring. The latter will see increasing connectivity of appliances beyond computing and communications systems.

Electronics can be protected against the EMP through shielding, a process known as ‘hardening’. This prevents the entry of the energy accompanying the EMP which could wreck circuitry. However, hardening can be expensive and is often reserved for military systems. Even key CNI nodes may lack this protection. Cost imperatives mean there will be multitudes of businesses and organisations with unhardened electronics which could find their operations badly disrupted by an EMP event, even if they are hundreds of miles from the epicentre, as events in Hawaii almost 60 years ago demonstrated.

Black Sky Hazard

This so-called ‘Black Sky Hazard’ should concentrate minds. As these nuclear explosions would be performed at very high altitude, accompanying bursts of electromagnetic radiation could range hundreds of kilometres beyond the detonation.

The Black Sky Hazards Resource Guide, published by the EIS Council, an international advocacy organisation raising awareness of the threat to electrical infrastructure from the EMP, highlights the danger an electromagnetic pulse event could have to CNI. The report says that the EMP has two parts: ‘E1’ is a very short burst of electromagnetic radiation, microseconds long, that would affect unshielded electronics. The E3 component could last several minutes and wreck unprotected high voltage electrical infrastructure like power lines, substations and switching yards causing major power cuts.

National electricity grids could be badly damaged by these E3 power surges. One does not have to think too hard about the severe disruption that even a short power cut brings to a town, city or region. The report says that damage to the electricity grid caused by the EMP would take time to repair. It warns that “the resulting breakdown of water, wastewater and food processing and delivery systems would lead to millions of deaths from dehydration, starvation and disease.” This would result from damage to the grid causing “cascading failures of all other lifeline infrastructures in those regions: Tap water, functioning toilets and sewage systems, food production and delivery, pharmaceutical supplies, communication, transportation, local and national security and distribution of all normally-available products and services would come to a halt.”


A scenario mooted by the report is one where a country chooses to detonate one or several warheads high above its adversary, but does not follow this with a salvo of nuclear weapons against strategic targets. The high altitude detonations could cause major CNI damage through the EMP, but no direct physical damage. This would place the country suffering the attack in a quandary: It would have just experienced a nuclear attack, albeit one in which the weapons themselves were not targeted against specific aim points. If that state also possessed nuclear weapons would this justify a retaliatory nuclear attack against the aggressor’s strategic targets, or only a response in kind? Regarding the latter, with both countries having now performed devastating EMP attacks above one another, would the next frightful step not be a nuclear exchange?

The repercussions of such an attack on CNI maybe blamed by the affected population on their own government, particularly if the attack causes widespread disruption and recovery efforts are slow and badly coordinated: “Failures to deal with the attack become the failures of the targeted government,” warns Lord Toby Harris, chair of the UK’s national preparedness committee and, until recently, UK coordinator for the EIS Council.

The report argues that such scenarios should be taken seriously: “Adversary countries or terrorist organizations with access to a small number of nuclear warheads may choose this mode of attack, rather than using their limited arsenal on a small number of ground targets. There is evidence that both North Korea and Iran have developed such plans.” Lord Harris believes that it is unlikely a non-state actor like an insurgent group or doomsday cult would mount such an attack. Quite simply, they may be unable to source the considerable nuclear technology this would need: “It would be difficult for an insurgent group but easier for a rogue nation,” says Lord Harris: “They could have the capacity to get the rocket into the air and deliver the explosion.”

An EMP attack with a nuclear weapon could be tightly focused and controlled according to the aggressor’s desired effect, he continues. The aggressor could decide how big an area they wished to affect, and how serious they wanted the damage to be by varying the power and altitude of the blast.


Lord Harris believes that EMP dangers should not be seen in isolation from other potential threats to electricity generation and distribution infrastructure such as cyberattack and Coronal Mass Ejections (CMEs). CMEs are large ejections of plasma and magnetic energy from the sun often following solar flares. In 1859 a CME was blamed for causing widespread disruption to the US and European telegraph networks. Telegraph cables absorbed the energy damaging connected apparatus. Known as the Carrington Event, after its observation by the British astronomer Richard Carrington, the disruption wrought by this CME indicates its disruptive potential for unprotected electricity grids. Lord Harris says that protective measures to harden grids against CMEs may have relevance in helping protect these same grids against EMPs: “We need to not only think about what we need to do to mitigate the threat of an EMP attack but what we need to do to harden our electricity grid against threats like CMEs or cyberattacks.” Sales of hardened BNET LMRs are a step in the right direction, but the EMP threat, along with the other dangers highlighted by Lord Harris are not something that should be treated with complacency.

by Dr. Thomas Withington