Electromagnetic pulse grenades are a favourite of sci-fi storytellers and videogame designers, a la Halo and Call of Duty. The US Army evidently doesn't want to be left out: it's seeking a real-life version that can blast electromagnetic signals and fry an opposition's bombs.

To be specific, the US Army wants "High Power Microwave (HPM) grenades" to "generate an electromagnetic pulse that could be used to defeat the electronics used to activate [homemade bombs] or that could be used to attack blasting caps," according to its latest round of research contracts with small businesses. In theory, the electrical components on improvised explosive devices, like radio transmitters, could be overwhelmed by surging electromagnetic radiation emitted by such a weapon.

If the US Army can actually develop this kind of Halo weapon, it'll take a step toward making each of its soldiers a kind of one-man bomb squad.


While the improvised bomb is the primary weapon used against US troops, not every soldier or marine can destroy a bomb in the same way he or she can target an opponent. To defuse bombs, troops rely on explosive ordnance demolition specialists, bomb-disposing robots and vehicle-mounted jammers. The Pentagon has also desperately struggled to stay a step ahead of the bombs' technical adaptations. But if the Army has working EMP grenades, any soldier could conceivably lob one into a room, around a corner or into a ditch to fry an awaiting booby-trap's circuits. As the Army puts it, it could mean "defeating IEDs by the individual soldier, while minimising the collateral damage to humans." Easier said than done.

An EMP grenade has to be small and lightweight enough to carry.

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The Army is requiring companies participating in the project to design their prototypes to fit the size of "hand or robot delivered munitions, 40 mm grenades, Rocket Propelled Grenades (RPGs), and Stinger, Hydra, and Javelin missiles." The next step is figuring out a working design itself.

The first thing to know is that an EMP grenade could be either explosive or non-explosive, with trade-offs for each. According to the 2011 textbook Explosive Pulse Power by Army engineer Larry Altgilbers, who is overseeing the project, a non-explosive device could use "pulse compression," or blasting brief but fierce electrical pulses while compressing the electrical current and voltage, thereby making the pulses stronger. As the device continues to blast out signals, the pulses then gradually decrease in duration. For a bomb circuit without protection diodes, such a burst of energy could theoretically fry its circuits or cause it to detonate.

Unfortunately, non-explosive systems "tend to be massive, large in size and fairly expensive," Altglibers wrote. But explosive systems are smaller, lighter and can generate a lot more electrical power. The Army solicitation refers to potentially using "energy stored in ferromagnetic, ferroelectric or superconducting materials." Possibly, these various magnets and superconductors could trap an electrical field inside a grenade, and when exploding, the grenade could compress the field. That would cause rapid changes in the field's structure, boosting its power and thus generating -- and releasing -- tremendous amounts of electromagnetic energy.


A downside to that, though, is superconducting materials have to stay cool. It's also likely to be a one-shot weapon as explosive pulse devices "generally destroy themselves and, quite usually, the load they are driving," according to Altgilbers. But if it's a grenade, then that might be no loss.

Less certain is how such a device would be used to neuter a bomb detonated with minimal electrical parts, like the Taliban bombs that detonate when someone compresses a wooden pressure plate; whether it would inadvertently fry US troops' own electronic circuits; or how difficult (or expensive) it'll be to develop an EMP grenade. One Israeli company has developed a much more conventional IED-jamming "grenade," but it uses tiny antennas to scram bomb signals instead of exploding out EMP waves. Perhaps if all else fails, the US Army could consider it. If not, it might play another round of Halo in order to brainstorm.

Source: Wired.com