Electronics-frying "e-bombs" have been discussed for decades — but rarely, if ever, deployed. Knocking out computers and communications gear with electromagnetic radiation is nice, but commanders prefer the proven method: blowing stuff up.

Now the U.S. Army is developing technology to do both at the same time. Hybrid munitions would give warheads the added punch of an e-bomb that can "destroy and disable electronic systems and their operators"

all in one blast. The key is a magnet that blows up and spontaneously demagnetizes, releasing energy as a pulse of power. Oh, and antennas made of fire. My story in the current Defense Technology International explains.

Previous e-bomb designs were based on explosively driven magnetic flux compression generators. They used a series of tightly wound, current-carrying metal coils that are rapidly compressed by an explosion. The new technology is much more compact. It's based on research showing that some magnets will spontaneously demagnetize when hit by a powerful enough shock wave, releasing a pulse of energy, in the process. The technical term is "pressure-induced magnetic phase transition."

Having proved the principle by blowing up neodymium magnets (like the ones in your headphones) the Army's Aviation and Missile Research Development and Engineering Center (Amrdec) have moved on to lead zirconate titanate magnets. The current state of the art is described as a completely explosive ultracompact high-voltage nanosecond pulse-generating system, occupying about one-fifth of a cubic inch.

There are engineering challenges at the other end. For this new weapon to work, you need an antenna that can fit inside a warhead, but is big enough to do the job. The problem is, the size is dictated by the properties of the electromagnetic pulse to be generated. You could used some sort of folding antenna, perhaps. The Army is going one step further and using an antenna made out of fire. To be more exact, Allen Stults of Amrdec is using the jet of ionized plasma produced by the explosion as an antenna.

It has been known for centuries that flames will conduct electricity; there are a few neat applications, like flame speakers.

This makes it possible to use a length of ionized gas rather than a piece of metal as an antenna. By tinkering with the chemical mixture in shaped charge warheads, Stults is creating a "plasma antenna" that will direct an electromagnetic pulse at the target. Like a lightsaber blade, the plasma antenna is a glowing tube that appears from nowhere —

and it should be quite deadly to electronics.

The multifunction warhead technology is being applied to several types of weapon, including TOW missiles, 70mm helicopter rockets and the bomblets dispensed by MLRS artillery. The effects of e-bombs are notoriously unpredictable. A lot depends on the exact type of electronic component and its orientation compared to the e-bomb. The new munitions will have two crucial advantages over previous e-bombs:

they are small, and should not cause electronic "friendly fire"

casualties hundreds of meters away. And because they still have the same blast, fragmentation and armor-piercing properties as they did, commanders can be confident that they're not wasting space carrying rounds that might have no effect.

A couple of weeks ago Col. Laurie Buckhout of the Army's new

Electronic Warfare Division, mentioned at a blogger's roundtable that technology for grenade-sized e-bombs existed. "But I've never had my hands on one," he added. There could be a lot of tactical applications for this sort of weapon. However, it's worth noting that if the technology spreads, U.S. forces are likely to be among the most vulnerable due to the heavy dependence on electronic devices.

[Illo: U.S. Army]

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