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Can North Korean nukes hit US mainland? Maybe. But EMP blast threat is 'highly credible'

El Reg talks to experts on Kim's capabilities

By Iain Thomson, 22 Aug 2017

Feature When they said a week is a lifetime in politics, they weren't kidding.

One moment, President Donald Trump talks of "fire and fury," the likes the world has never seen, in response to an increasingly aggressive North Korea, which is trying to menace the US with nuclear weapons.

Then that's shoved to the side by neo-Nazis marching on the streets of Charlottesville, Virginia, resulting in the killing of an antifascist protestor. Then it's back to musical chairs at the White House with Steve Bannon ousted and tech leaders quitting the administration's advisory panel.

One moment, we were all awaiting the warm, so very warm, embrace of all-out global annihilation. The next, it goes quiet. But it's not over. This week, the US and South Korea are carrying out military drills that North Korea claims could lead to "uncontrollable phase of a nuclear war." The Kim Jong-Un-led hermit nation is also hell bent on building an arsenal of nukes despite international resistance, and even its ally China is urging it to calm down.

So, what can the Norks actually achieve: do they have working nukes, and can they reach the US? Realistically, the chances of either North Korea or the US slinging missiles at each other are slim. China says it will retaliate if America launches a preemptive strike against North Korea, filling the skies with warheads aimed at US cities. So it's, as we say around here, suboptimal even for Trump to wipe North Korea off the map. However, China said it will take a neutral stance if the US responds to a Nork launch, so it would be pure suicide for Kim Jong-Un to try to hit America. And he doesn't want death, well, not for himself: he wants sanctions lifted and respect from world leaders.

And whatever happens, if North Korea is going down, it's taking South Korea with it. And no one wants the blood of Seoul on their hands.

Having said that, North Korea has, allegedly, perfected a nuclear device small enough to fit in one of its intercontinental ballistic missiles, and has test fired a few of these rockets without them exploding en route.

However, experts are still skeptical that North Korea has the ability to successfully lob a nuke all the way to the American mainland. While its rockets work some of the time, and even accepting reports that they have a nuclear bomb that can fit inside a missile, there are still hurdles to overcome – chiefly reentry and targeting.

After its boost phase, an ICBM will travel through space and then reenter the atmosphere. That's a really tough process, because it involves compressing the air around it at such a rate that it quickly heats up the rocket. Without a nose cone capable of withstanding these temperatures, and there appears to be no sign of one on Nork missiles, the bomb would burn up before it could detonate. There's also the slight possibility that Uncle Sam's missile shield might actually work and shoot down Kim Jong-Un's package.

So far, the answer to the question, can North Korea reach California with a rocket, is: probably possibly. Can it actually survive reentry and nuke the Golden State? Maybe.

But there is another option for the North Koreans, and one that could possibly do far more damage than a single nuclear strike. Before reentry temperatures kick in, the bomb could be detonated in the upper atmosphere – and the electromagnetic pulse (EMP) generated would potentially do more damage than a single missile could ever manage. Successfully emitting an EMP blast over the US West Coast, with Silicon Valley within its grasp, or further inland, would be extremely bad news for our future on this planet.

In other words, Kim Jong-Un doesn't have to strike America, setting off a cliched mushroom cloud: using EMP high in the skies to wreck our electronics and communications could be, potentially, enough to upturn society and put us on the path to global thermonuclear war.

EMP, silent but deadly

When a nuclear weapon is detonated it doesn't just generate the massive ball of fiery destruction we're all familiar with, but also three distinct levels of electromagnetic pulse.

  1. As gamma rays erupt from the exploding bomb, they generate a "fast pulse" EMP, or E1, as they strike air molecules. This peaks at tens of kilovolts per metre in a few nanoseconds, lasts for a few hundred nanoseconds in total, and can induce thousands of amperes in electrical systems.
  2. From around one microsecond to one second after the explosion, the interaction of gamma rays also generates E2 EMP. This is less of an issue, but coupled with the E1 pulse could cause electrical damage.
  3. However, it's the E3 "slow pulse" that's a massive problem for industries, like power generation and telecommunications, below the blast. It is caused by the effect of the explosion on the planet's magnetic field and can last hundreds of seconds. Its effect on electrical systems using long cables is immense, generating hundreds to thousands of amperes in conducting lines.

The electromagnetic pulse (or "radioflash," as the British called it) generated by a nuclear explosion has been known about since before the first Trinity test in 1945. It was an annoying side effect but could easily be protected against.

However, in the 1960s the US and the Soviet Union began to consider the offensive uses of EMP. In 1962 both sides began detonating atomic bombs in the upper atmosphere and recording the effects on the ground.

On the US side, the Starfish Prime test on July 9, 1962 detonated a 1.4 megaton bomb 250 miles up over Johnson Island in the Pacific. It caused electrical damage on Hawaii 1,400 miles away, crippled eight satellites, and killed three of them stone dead. War planners took note.

While Hollywood fiction usually depicts the start of a nuclear war with masses of rockets firing off, in fact the first sign of war would probably be power failures and electronics temporarily freaking out. Both sides had war plans that called for the first detonations to take place in the upper atmosphere, generating a massive EMP that would hopefully stun or cripple the enemy and reduce their ability to retaliate and recover.

Testimony to the US Congressional EMP Commission stated that in the event of a massive EMP attack on the US using multiple high-yield warheads, around 90 per cent of the American population would be dead after 18 months due to famine, disease, and societal breakdown.

Small bomb, big noise

"EMP is the most asymmetric threat there is in terms of a single weapon taking out large categories of infrastructure," Dr George Baker, former leader of the Defense Nuclear Agency's EMP program, told The Register. "It's a lot easier to achieve, since you don't need reentry capabilities."

Baker said that a low-yield device such as that thought to be owned by North Korea, detonated at optimum height, would generate EMP over an area with a diameter of around 1,000 miles. He understandably declined to specify the optimum height, but it's thought to be around 50 to 80 miles up.

If such a device were to be detonated over the most densely populated part of the US, namely the North East, the consequences for power grids, computing centers and telecommunications systems could be catastrophic, he explained. Baker and others have formed the Foundation for Resilient Societies to advise Congress on this and other critical infrastructure issues.

His colleague at the foundation, retired Air Force captain Thomas Popik, is principal investigator for the group. Popik told The Register that by far the most vulnerable infrastructure is the power grid. E3 pulses are amplified by the length of the conductive cable they encounter, and the power grid has some very long cables indeed.

"A North Korean EMP attack is extremely credible," he said. "No reentry is required and a low-yield weapon could produce a significant impact on the electrical grid. The grid is designed to be resilient to single failures but not multiple simultaneous failures."

The problem is amplified by the nature of the grid. A series of failures can cause a catastrophic knock-on effect on the rest of the grid as power surges and troughs play merry hell with the network.

Most vulnerable would be the handful of massive transformers needed to keep power regulated through the grid. These enormously costly and complex pieces of equipment currently take around 22 months to build and deliver, so the power companies don't keep many in reserve.

To complicate matters the US has outsourced about 80 per cent of the production of these transformers to countries like China and Germany. They also require a specialized kind of high-tensile coated steel, but as US companies don't make a lot of the transformers, American steel producers have stopped making the necessary materials.

Power plants are going to take a hit, Popik warned, but there was some good news on that front. Many power stations are dual-fuel systems, capable of running on gas and fuel oil. The problem is that many stations don't keep the reserve oil tanks topped up for emergencies.

There's also a surprising number of power stations that don't rely on digital controls. A lot of the hydroelectric stations built in the 1930s and 40s in the West of America, including Hoover Dam, can operate perfectly well using analogue controls and so might well survive an EMP attack.

The telecommunications cables that make up the communications backbone of the US, and the world, would also be extremely vulnerable. Signal amplifiers, switching stations and routers could all be burned out by a strong EMP pulse, and that would have a massive knock-on effect on the computing infrastructure of the nation.

Some more alarmist scenarios depict an EMP pulse destroying all electronics completely, with modern cars, all electronics with chips, and anything with a current getting taken out. That's unlikely, but we don't really know because so little testing has been done on the matter.

In 2004, the EMP Commission tested 37 vehicles by exposing them to steadily more powerful electromagnetic stimuli. The initial results looked promising – none of the cars stopped working permanently, a few did need to be restarted, and there was a minor amount of electrical damage to several of them.

There are some important caveats, however. The cars were deliberately not tested to destruction because they had to be returned to the US Department of Defense, so the minute an effect was noticed the testing was stopped on that vehicle. In addition, none of the cars were built after 2002; it would be interesting to see how a Tesla, let alone any other modern car packed with electronics, measures up.

Protect and survive

As the American military prepared to use EMP it also developed shielding against it. Ever since the 1960s military communications systems, control centers and missile bases have all had their systems hardened against attack. Even Air Force One has a measure of EMP shielding.

But the civilian sector has very little in the way of protection. Faraday cages, which protect electrical devices from EMP, are popular with some folks but aren't really practical; most of our infrastructure is totally unprotected. Part of this is down to cost, but also because no one wants to take responsibility for the issue.

"There is no single point of responsibility to develop and implement a national protection plan. Nobody is in charge," Dr Baker testified [PDF] to Congress in 2015.

"When I asked the North American Electric Reliability Corporation about EMP protection, they informed me, 'We don't do EMP, that's a Department of Defense problem.' The Department of Defense tells me, 'EMP protection of the civilian infrastructure is a DHS responsibility.' DHS explained to me that the responsibility for the electric power grid protection is within DOE, since they are the designated Sector Specific Agency for the energy infrastructure."

However, there are private companies that will design EMP shielding, for a price. Jack Pressman, managing director of Cyber Innovation Labs, works with EMP Grid Services, an organization that builds computing networks designed to withstand EMP and solar storms.

"You can't just build a Faraday cage around the data center and call it safe," he told The Register. "You can enclose one, but you'd still have to move power, cooling and telecoms in and out of the box and these can all be points of failure. You have to build in filters that ground and disperse electromagnetic energy."

Putting these kinds of protection into an existing data center is almost prohibitively expensive, but applying them to a new-build unit only increases the cost by around eight per cent, he explained. To cut costs some firms will simply harden a small portion of their data centers holding critical data.

The group has recently built an EMP-hardened data center for backup and storage group Iron Mountain, building it partially underground for additional protections. The client, a Fortune 500 financial company, is a typical type of customer.

"Most big data center infrastructure firms like Google and Amazon aren't that interested," Pressman said. "They think, 'If we lose one or two facilities then so be it, we have 40 globally.'"

Much ado about nothing?

So at the end of the day, how worried should we be about a North Korean EMP attack? Not too much, according to Herb Lin, research scholar for cyber policy and security at the Center for International Security and Cooperation at Stanford.

He told The Register that the kind of 10 or 20-kiloton device that the North Koreans are supposed to have might cause damage, but it wouldn't be the massive population killer that some have suggested.

He points out that the Starfish Prime tests in 1962 used a 1.4 megaton device and caused limited damage. The much smaller device attributed to the North Koreans, even supposing that it and the missile delivery system work, would cause less damage.

It is possible to design a nuclear bomb that is specifically built to maximize the EMP output, even if this means reducing its explosive power. But such devices are highly sophisticated and likely beyond the reach of the impoverished state. Even if they have been given the plans to build such a device, there are considerable materials engineering challenges.

However, as befits a strategic thinker, Lin raised a fascinating point that could show how, even if North Korea does launch an attack, the US might be facing something of a quandary.

"Suppose they launch it and it does no damage," he posited. "What do we do then? No one is asking that." ®

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