Electromagnetic

The Perfect Weapon: No Fractured Bricks or Spilled Blood

Just a Normal Town...
by Ian Sample

Source: New Scientist

July 1, 2000

... but out of nowhere a wave of chaos was to wash over that world. In a millisecond it was gone. There were no phones, no computers, no power, nothing. Yet nobody had died, no buildings razed to the ground. And then the blind panic set in. Whatís going on, asks Ian Sample

IT SOUNDS like the perfect weapon. Without fracturing a single brick or spilling a drop of blood, it could bring a city to its knees. The few scientists who are prepared to talk about it speak of a sea change in how wars will be fought. Even in peacetime, the same technology could bring mayhem to our daily lives. This weapon is so simple to make, scientists say, it wouldnít take a criminal genius to put one together and wreak havoc. Some believe attacks have started already, but because the weapon leaves no trace itís a suspicion thatís hard to prove. The irony is that itís our love of technology itself that makes us so vulnerable.

This perfect weapon is the electromagnetic bomb, or e-bomb. The idea behind it is simple. Produce a high-power flash of radio waves or microwaves and it will fry any circuitry it hits. At lower powers, the effects are more subtle: it can throw electronic systems into chaos, often making them crash. In an age when electronics finds its way into just about everything bar food and bicycles, it is a sure way to cause mass disruption. Panic the financial markets and you could make a killing as billions are wiped off share values. You could freeze transport systems, bring down communications, destroy computer networks. Itís swift, discreet and effective.

Right now, talk of the threat of these weapons is low-key, and many want it to stay that way. But in some circles, concern is mounting. Last month, James OíBryon, the deputy director of Live Fire Test & Evaluation at the US Department of Defense flew to a conference in Scotland to address the issue. "What weíre trying to do is look at what people might use if they wanted to do something damaging," he says. With good reason, this is about as much as OíBryon is happy to divulge.

E-bombs may already be part of the military arsenal. According to some, these weapons were used during NATOís campaign against Serbia last year to knock out radar systems. So do they really exist? "Lots of people are doing lots of work to protect against this type of thing," says Daniel Nitsch of the German Army Scientific Institute for Protection Technology in Muster, Lower Saxony. "You can make your own guess."

Interest in electromagnetic weapons was triggered half a century ago, when the military were testing something a lot less subtle. "If you let a nuclear weapon off, you get a huge electromagnetic pulse," says Alan Phelps of the University of Strathclyde in Glasgow. If this pulse hits electronic equipment, it can induce currents in the circuitry strong enough to frazzle the electronics. "It can destroy all computers and communications for miles," says Phelps.

But the military ran into problems when it came to finding out more about the effects of these pulses. How could they create this kind of powerful pulse without letting off nuclear bombs? Researchers everywhere took up the challenge.

The scientists knew that the key was to produce intense but short-lived pulses of electric current. Feeding these pulses into an antenna pumps out powerful electromagnetic waves with a broad range of frequencies. The broader the range, the higher the chance that something electrical will absorb them and burn out.

Researchers quickly realised the most damaging pulses are those that contain high frequencies. Microwaves in the gigahertz range can sneak into boxes of electronics through the slightest gap: vent holes, mounting slots or cracks in the metal casing. Once inside, they can do their worst by inducing currents in any components they hit. Lower radio frequencies, right down to a few megahertz, can be picked up by power leads or connectors. These act as antennas, sending signals straight to the heart of any electronic equipment they are connected to. If a computer cable picks up a powerful electromagnetic pulse, the resulting power surge may fry the computer chips.

To cook up high-frequency microwaves, scientists need electrical pulses that come and go in a flash--around 100 picoseconds, or one ten-billionth of a second. One way of doing this is to use a set-up called a Marx generator. This is essentially a bank of big capacitors that can be charged up together, then discharged one after the other to create a tidal wave of current. Channelling the current through a series of super-fast switches trims it down to a pulse of around 300 picoseconds. Pass this pulse into an antenna and it releases a blast of electromagnetic energy. Marx generators tend to be heavy, but they can be triggered repeatedly to fire a series of powerful pulses in quick succession.

Deadly burst

Marx generators are at the heart of an experimental weapons system being built for the US Air Force by Applied Physical Sciences, an electronics company in Whitewater, Kansas. "Weíre trying to put them on either unmanned aerial vehicles or just shells or missiles in an effort to make an electromagnetic minefield," says Jon Mayes of APS. "If something flies through it, itíll knock it out." It could also be used on a plane to burn out the controls of incoming missiles, says Mayes. Put it on the back of a military jet and if a missile locks onto the plane, the generator can release a pulse that scrambles the missileís electronics.

Marx generators have the advantage of being able to operate repeatedly. But to generate a seriously powerful, one-off pulse, you canít beat the oomph of old-fashioned explosives. The energy stored in a kilo or two of TNT can be turned into a huge pulse of microwaves using a device called a flux compressor. This uses the energy of an explosion to cram a current and its magnetic field into an ever-smaller volume. Sending this pulse into an antenna creates a deadly burst of radiowaves and microwaves.

Simplicity is one of the flux compressorís big attractions. Just take a metal tube, pack it with explosives, and stick a detonator in one end. Then fix the tube inside a cylinder of coiled wire, which has a wire antenna attached at the far end. Finally, pass a current through the coil to set up a magnetic field between the metal tube and the coil, and youíre ready to go.

Setting off the detonator triggers the charge, sending an explosion racing along the tube at almost 6000 metres per second. If you could slow this down, youíd see that in the instant before the explosive pressure wave begins to shatter the device, the blast flares out the inner metal tube. The distorted metal makes contact with the coil, causing a short circuit that diverts the current--and the magnetic field it generates--into the undisturbed coil ahead of it. As the explosive front advances, the magnetic field is squeezed into a smaller and smaller volume. Compressing the field this way creates a huge rise in current in the coil ahead of the explosion, building a mega-amp pulse just 500 picoseconds wide. Finally, just before the whole weapon is destroyed in the blast, the current pulse flows into an antenna, which radiates its electromagnetic energy outwards. The whole process is over in less than a tenth of a millisecond, but for an instant it can spray out a terawatt of power.

Tom Schilling of TPL, an electronics company in Albuquerque, New Mexico, is working along similar lines with the microwave weapons heís developing for the US Air Force. "Weíre using explosive flux generators to generate the power, then sending that straight into an antenna," he says. "One of the systems weíre looking at is a guided bomb that can be dropped off a plane. Targets would be things like command and control centres--we should be able to shut those down with little or no collateral damage." Schillingís company is also looking at putting flux compressors into air-to-air missiles. Itís an appealing idea, as even a near miss could bring down a plane.

It certainly ought to be practical. As long ago as the late 1960s, scientists sent a pair of flux compressors into the upper atmosphere aboard a small rocket to generate power for an experiment to study the ionosphere. "You can build flux compressors smaller than a briefcase," says Ivor Smith, an electrical engineer at Loughborough University who has worked on these devices for years.

Perhaps the biggest benefit of these weapons is that they carry the tag "non-lethal". You could take out a cityís communications systems without killing anyone or destroying any buildings. In addition to the obvious benefits for the inhabitants, this also avoids the sort of bad press back home that can fuel opposition to a war. But that doesnít make these weapons totally safe, especially if theyíre being used to mess up the electronics of aircraft. "If youíre in an aeroplane that loses its ability to fly, itís going to be bad for you," points out James Benford of Microwave Sciences in Lafayette, California.

Another big plus for people thinking of using these weapons is that microwaves pass easily through the atmosphere. This means that you can set off your weapon and inflict damage without having to get close to your target. "People think in terms of a kilometre away," says Benford. According to some estimates, a flux compressor detonated at an altitude of few hundred metres could wipe out electronics over a 500-metre radius.

Electromagnetic weapons can be sneaky, too. You donít have to fry everything in sight. Instead you can hit just hard enough to make electronics crash--they call it a "soft kill" in the business--and then quietly do what you came to do without the enemy ever knowing youíve even been there. "That could be useful in military applications when you just want to make [the opposition] lose his electronic memory for long enough to do your mission," Benford says. "You can deny you ever did anything," he adds. "Thereís no shrapnel, no burning wreckage, no smoking gun."

Did it work?

The downside is that it can sometimes be hard to tell when an electromagnetic weapon has done its job. This is compounded by the fact that unless you know exactly what kind of electronics you are attacking, and how well protected they are, itís hard to know how much damage a weapon will do. This unpredictability has been a major problem for the military as it tries to develop these weapons. "Military systems have to go through an enormous amount of development," says Benford. "The key thing is that it has to have a clearly demonstrated and robust effect."

Tests like this are close to the heart of Nigel Carter, who assesses aircraft for their sensitivity to microwaves at Britainís Defence Evaluation and Research Agency in Farnborough, Hampshire. Microwaves can easily leak between panels on the fuselage, he says. "Youíve also got an undercarriage with hatches that open, thereís leakage through the cockpit, leakage through any doors."

To find out how bad that leakage is, Carter could simply put the plane in a field and fire away at it with microwaves. But he has to be careful. "If we go blatting away at a very high level at hundreds of frequencies, people in the nearest town get a bit upset because they canít watch TV any more," says Carter. "Itís very unpopular."

To avoid annoying the neighbours, Carter beams very low-power microwaves at the plane. Sensors on board--linked by fibre optics to data recorders so they are immune to the microwaves--record the currents induced in the planeís electronics.

Knowing what currents are produced by weak microwaves, Carter calculates what kinds of currents are likely to be produced if the plane is hit by a more powerful pulse of microwaves. "You can then inject those currents directly into the electronics," he says. The results can be dramatic. "The sort of effects you might expect to get if itís not protected are instrumentation displaying wrong readings, displays blanking out and you could, in the worst case, get interference with your flight controls," he says.

The idea of weapons like these being used in warfare is disturbing enough, but what if criminals get their hands on them? According to Bill Radasky, an expert in electromagnetic interference with Metatech in Goleta, California, they may have already done so. A basic microwave weapon, he says, can be cobbled together with bits from an electrical store for just a few hundred dollars. Such a system would be small enough to fit in the back of a car and could crash a computer from 100 metres away.

Other systems are even easier to acquire. Some mail-order electronics outlets sell compact microwave sources that are designed to test the vulnerability of electronics. But they could just as easily be used in anger. "Weíve done experiments that show itís very easy to do," says Radasky. "Weíve damaged a lot of equipment with those little boxes." If some reports are to be believed, theyíre not the only ones.

Criminals may have already used microwave weapons, according to Bob Gardner who chairs the Electromagnetic Noise and Interference Commission of the International Union of Radio Science in Ghent, Belgium. Reports from Russia suggest that these devices have been used to disable bank security systems and to disrupt police communications. Another report suggests a London bank may also have been attacked. While these incidents are hard to prove, theyíre perfectly plausible. "If youíre asking whether itís technologically reasonable that someone could do something like this," says Gardner, "then the answer is yes."

Gardnerís claims are backed by Nitsch. He is investigating how vulnerable computers and networks are to powerful bursts of microwaves. Surprisingly, he has found that todayís machines are far easier to crash than older models. He says computer manufacturers used to be more worried about electromagnetic interference, so they often put blocks of material inside to absorb stray signals, and ran strips of copper around the joins in the casing to keep microwaves out.

That modern computers have less protection is bad enough. But they are also more susceptible because they are more powerful. To push signals around faster, you must reduce the voltage to ensure that the extra current doesnít make the processor chips overheat. In the 1980s, most computers operated at 5 volts. Todayís machines operate at nearer 2 volts, says Nitsch, making their signals easier to disrupt. Networks are particularly susceptible, he adds, because the hundreds of metres of cabling connecting their workstations can act as an efficient radiowave receiving antenna.

Secret attacks

So are businesses taking the threat seriously? Radasky knows of only one European company that has protected its control centre against microwave weapons. Gardner believes it will take a high-profile attack to raise awareness of the issue. But combine the lack of evidence left by microwaves with companiesí reluctance to admit their systems have been breached and youíd expect attacks to go unreported.

The good news is that protection isnít too difficult if itís done at the design stage, says Carter. The first thing to do is make sure youíve got well-constructed circuits. This means using strong signals that can easily be distinguished from the fuzz of noise generated by microwaves. "You also want to make sure your circuitry only responds at the frequency itís supposed to," he says. So if your computer is intended to respond to signals coming in at 500 megahertz, you want to make sure it wonít also respond to signals at twice that frequency--the kind that could be induced by microwaves. Another step is to wire in filters that absorb large surges of current--much like those used to protect against glitches in the mains power supply following lightning strikes.

Regardless of whether these weapons have been used yet, they highlight the way our dependence on electronics could become our Achillesí heel. The next time your computer crashes, donít automatically blame Bill Gates. Just wander over to the window and look out for that unmarked van that sometimes parks across the street. Could there be someone inside sending a blast of microwaves your way?

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