Direct Energy weapons.

The Economist January 30, 2003

Electromagnetic weapons

“Come fry with me

In-Depth Coverage

Experimental electromagnetic weaponry may soon see combat use

The first well-known strategic weapon was the Trojan horse, which allowed the Greeks to capture Troy without damaging the city's walls. If comments last year by Donald Rumsfeld, America's defence secretary, are to be believed, new electromagnetic weapons may yet allow America to do the same to Baghdad. This would, some think, represent the first combat use of such weaponry.

Using different types of electromagnetic energy (the same stuff as radio waves, X-rays and light), these weapons are able to destroy electronic systems and temporarily incapacitate people, all without the mess of explosions and gunfire. Although the systems are still said to be experimental, the recent use of armed, unmanned drones in Afghanistan and Yemen has shown that America's armed forces have become good at applying new weapons technology in the field.

It all started in 1962, when America first exploded a nuclear bomb 30km (19 miles) up in the atmosphere. The energetic gamma rays caused by the explosion triggered an electromagnetic pulse that disrupted radio stations 1,200km away. Although the pulse lasted for only a fraction of a second (and thus was harmless to humans) it was enough to seed the idea that electromagnetic pulses were possible, and potentially useful.

Luckily, an electromagnetic pulse can be generated without a nuclear explosion. America's efforts are centred at a research laboratory at Kirtland Air Force Base in New Mexico. A spokesman from Kirtland refuses to comment on the research, but according to a study done for the Australian air force, the most likely way of creating weaponised high-powered microwaves (HPMs) is through a device known as a vircator.

A vircator works by discharging stored electricity into a coil of wires wrapped around an explosive. The flowing electricity creates a magnetic field, which is then compressed as the (relatively small) explosive goes off. This causes a low-frequency electromagnetic pulse that is used to accelerate electrons to high energies and punch through a sheet of foil. The electrons form an unstable bubble of charge that oscillates in a cavity designed for the purpose. The oscillation creates HPMs that are then emitted from an antenna that guides them towards the target.

Because the source of the energy is a compact explosive, a vircator could fit inside bombs or cruise missiles. Deployed, they could disrupt a variety of enemy systems, from missile targeting and launch electronics, to command-and-control systems. It is possible that they could penetrate hundreds of metres below the ground and reach underground bunkers built for protection against explosives. Larger, reusable weapons are also being developed for use on ships to disable incoming missiles such as China's Silkworm.

Microwave on "high"

At a time when America's war technology is the most advanced in the world, and the most dependent on electronics, an obvious problem with such weaponry is that attackers may themselves be susceptible to damage when in proximity to an attack. It is a phenomenon known to military theorists as the "fratricide" problem-and to everybody else as a double-edged sword. Because the wavelengths of HPM weapons are so short, they are also the most difficult to protect against, as they can penetrate the smallest of gaps.

Systems for protecting against electromagnetic radiation are already being developed. They have evolved from civilian research into ways of protecting aircraft against lightning strikes. One approach is to shield equipment by surrounding sensitive components in a swathe of conducting material (such as metal) that excludes external electric and magnetic fields. Another is to use antennas designed to shunt energy away from sensitive components, and to direct it towards the ground.

According to Lieutenant-Colonel Piers Wood, a fellow at GlobalSecurity.org, an American think-tank, even with such protection America remains nervous about using electromagnetic weapons close to manned aircraft. That is why HPMs are a driving force behind the development of more sophisticated unmanned craft, from bomb-sized drones such as the "loitering electronic warfare killer", to automated helicopters and even giant blimps that may soon ring America as components of a missile-defence system.

Sophisticated armies are not the only potential users of electromagnetic weaponry. Unlike military planes, passenger jets are not well protected against electromagnetic weapons and so are susceptible even to chance electromagnetic emissions from mobile phones, CD players or laptop computers that come from within the plane's metal skin. In what is a textbook case of asymmetrical warfare, a terrorist equipped with a low-powered device (ie, one that is not explosively powered and rather simple to build) could still conceivably cause a plane to crash.

Less technologically challenging than high-powered devices designed to knock out electronic systems are those designed to work against humans. These fall into the same category of weaponry as schemes for slippery foam and powerful laser pointers to blind temporarily (or rather, to "impair visual efficiency"), being developed by the American Marine Corp's Joint Non-Lethal Weapons Directorate, in Quantico, Virginia.

Hot to trot

So-called "active denial" technology (which earns its moniker by actively herding people out of its path) works by using a beam of millimetre-length microwaves to heat up a person's skin. The marines are planning to put a version of the weapon on to a jeep. Its range and properties are classified, but military newspapers say it can heat a person's skin to 55°C (130°F) at distances of up to 750 metres. This has urban-warfare planners excited, as it would let American forces clear city blocks in, say, Baghdad, without going door-to-door and risking American casualties.

At first glance, such devices as HPMs and the active denial system seem to be a good idea. They would allow well-equipped armies to conquer more quickly and effectively, with less loss of life. But some observers are more cautious about the technology. Steve Goose of Human Rights Watch, an American advocacy group, although noting that he has no problem with the idea of non-lethal weapons, says that too much secrecy still surrounds them. Weapons such as HPMs may have unintended long-term health consequences, he says. And weapons such as the active denial system could cause severe trauma, or even death, if fired at close range or held on a target for too long. Critics of non-lethal systems also worry that they might be used for repression of civilian populations.

David Fidler, a law professor at Indiana University, says that, because these weapons are most likely to be used on civilians, it is not clear that using them is legal under the international rules governing armed conflict. He also notes that, if they are used in conjunction with conventional weapons, they could end up making war more deadly, rather than less. And he adds that non-lethal weapons raise a new ethical conundrum: is it acceptable to shoot or bomb somebody if you have the option only to disable them?

Odysseus's scheme ended a bloody war, though it did so bloodily. Electromagnetic weapons could avoid this. But the secrecy over them makes it hard to judge.

Copyright © 2003, The Economist”

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