105 miles above Ohio, a single nuclear warhead explodes. Because it is far above the atmosphere, there will be no blast or fire effects felt on Earth, however this high-altitude nuclear detonation will create a gigantic electromagnetic pulse or EMP.

In one billionth of a second, the initial E1 EMP wave will cause massive voltages and currents to form within power lines, telecommunication lines, cables, wires, antennas, and any other electrically conductive material found beneath the nuclear detonation in a circular area covering hundreds of thousands of square miles.

Within this region, under ideal conditions, the E1 wave will produce 2 million volts and a current of 5,000 to 10,000 amps within medium distribution power lines. Any unshielded modern electronic devices that contain solid-state circuitry, which are plugged into the grid, will be disabled, damaged, or destroyed. This includes the electronic devices required to operate all critical national infrastructure.

Unshielded electronic devices within ground, air, and sea transportation systems, water and sanitation systems, fuel and food distribution systems, telecommunication systems, and banking systems would all be simultaneously knocked out of service – and all these systems would be disabled until the solid-state electronics required to operate them could be repaired or replaced.

In a region below the detonation, which can range in size from the state of Missouri to the state of Texas (70,000 to more than 100,000 square miles), the E1 wave can also penetrate, damage, and destroy unshielded electronic devices that aren’t plugged into the grid.

The E1 wave will also instantly destroy millions of glass insulators found on 15 kilovolt-class electric power distribution lines. 78% of all electricity in the US is delivered to end users (residential, agricultural, commercial) through these 15 kV power lines. The loss of a single insulator on a line can knock out power distribution on the entire line.

At the same instant, the massive voltage and current induced by the E1 wave will damage and destroy the relays, sensors, and control panels at 1783 High Voltage Substations, knocking out the entire electric power grid in the eastern half of the United States.

One to ten seconds after the nuclear detonation, the following E3 waves would induce powerful current flows in power lines and communication lines, including lines that are both above and below ground. E3 would damage or destroy many – if not most – of the Large Power Transformers and Extra High Voltage Circuit Breakers that are required for the long-distance transmission of about 90% of electrical power in the United States.

The loss of Large Power Transformers and Extra High Voltage Circuit Breakers would mean that entire regions within the United States would be left without electric power for up to a year or longer. This is because Large Power Transformers are not stockpiled and the current wait time for their manufacture is 18 to 24 months; they must be custom designed and manufactured and about 80% are made overseas. They each weigh between 200 and 400 tons and must be shipped by sea and moving them to their final destination is quite difficult even under normal circumstances.

Because nuclear power plants are not designed to withstand the effects of EMP, the solid-state electronics within their backup electrical and cooling systems would also be damaged and disabled. The failure of their Emergency Power Systems and active Emergency Core Cooling Systems will make it impossible to cool their reactor cores after emergency shutdown; this will quickly lead to reactor core meltdowns at dozens of nuclear power plants.

To summarize, a single nuclear high-altitude electromagnetic pulse can instantly take out most or all of the US power grid while simultaneously destroying the solid-state electronic devices required to operate US critical national infrastructure – including the safety systems at nuclear power plants. Following a nuclear EMP, the people of the US would suddenly find themselves living the conditions of the Middle Ages for a period possibly as long as a year – many would not be able to survive such circumstances.

For less than 4% of the US national defense budget, the US power grid and critical infrastructure can be shielded from EMP. However, the political will to implement this protection has not yet been found, so Americans remain very much at risk.