Just a Normal Town...
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. What’s 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 wouldn’t take a criminal genius to
put one
together and wreak havoc. Some believe attacks have started already,
but because the weapon leaves no trace it’s a suspicion that’s hard to
prove. The irony is that it’s 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. It’s 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 O’Bryon, 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 we’re 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 O’Bryon
is happy to divulge.
E-bombs may already be part of the military arsenal.
According to some, these weapons were used during NATO’s 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. "We’re 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, it’ll 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 missile’s electronics.
Marx generators have the advantage of being able to
operate repeatedly. But to generate a seriously powerful, one-off
pulse, you can’t 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 compressor’s 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 you’re 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, you’d 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 he’s developing for the US Air Force. "We’re using
explosive flux generators to generate the power, then sending that
straight into an antenna," he says. "One of the systems we’re 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." Schilling’s company
is also looking at putting flux compressors into air-to-air missiles.
It’s 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 city’s
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 doesn’t make these weapons totally safe,
especially if they’re being used to
mess up the electronics of aircraft. "If you’re in an aeroplane that
loses its ability to fly, it’s 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 don’t
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 you’ve 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. "There’s 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, it’s 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 Britain’s
Defence Evaluation and Research Agency in Farnborough, Hampshire.
Microwaves can easily leak between panels on the fuselage, he says.
"You’ve also got an undercarriage with hatches that open, there’s
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 can’t watch TV any more," says Carter. "It’s 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 plane’s 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 it’s 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. "We’ve done experiments that show it’s
very easy to do," says Radasky. "We’ve damaged a lot of equipment with
those little boxes." If some reports are to be believed, they’re 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, they’re
perfectly plausible. "If you’re asking whether it’s technologically
reasonable that someone
could do something like this," says Gardner, "then the answer is yes."
Gardner’s claims are backed by Nitsch. He is
investigating how vulnerable computers and networks are to powerful
bursts of microwaves. Surprisingly, he has found that today’s 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 doesn’t make the processor chips
overheat. In the 1980s, most computers operated at 5 volts. Today’s
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 companies’ reluctance to
admit their systems have been breached and you’d expect attacks to go
unreported.
The good news is that protection isn’t too difficult if
it’s done at the design stage, says Carter. The first thing to do is
make sure you’ve 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 it’s 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 won’t 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
Achilles’ heel. The next time your computer crashes, don’t
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?
by Ian Sample