That hasn’t stopped the Pentagon from trying.
One novel approach that’s been getting attention in Washington lately is microwave weapons. The idea is to zap the launch site or control center with a powerful, targeted microwave blast fired from a low-flying missile to effectively melt the target’s electronic hardware.
"Think about when you put something in your microwave that has metal on it," Senator Martin Heinrich, a Democrat from New Mexico, told NBC News. "You know how badly that goes? Imagine directing those microwaves at someone's electronics."
This month, NBC reported that the microwave concept was discussed in a White House meeting on August 4.
The weapon in question is known as a CHAMP missile, short for Counter-electronics High Power Microwave Advanced Missile Project. Delivered from a B-52 bomber, the missile can reportedly fly 700 miles at low altitude and emit sharp pulses of microwave energy. In theory, the microwave blast might be able to simply pull the plug on everything at a given facility without causing any fatalities.
One advantage of a microwave blast is that it might cause less collateral damage than a conventional attack, and therefore, possibly, represent a less aggressive approach than a conventional missile strike — reducing the odds of massive retaliation by North Korea against neighboring South Korea.
Or maybe not. The requirement to be relatively close to the target would mean launching a noisy, low-flying projectile deep into North Korea, a move that could have unpredictable consequences whether it explodes or not, analysts said.
“Something like the CHAMP is a pretty nifty idea, but if you know exactly where the missile is, and you know they're about to launch it, then it's way simpler to just drop a bomb on it,” Scharre said.
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Another high-tech solution being considered is placing high-powered lasers on drones, and hovering them near the missile’s likely early flight path. As the missile ascends, the laser could burn it out of the sky like a flying light saber.
Using a light beam would help resolve a key problem with incoming missiles: their astonishing speed. As an Intercontinental Ballistic Missile ascends, it gradually reaches a velocity of up to 7 kilometers per second. A bullet from an M16 rifle, by contrast, travels at roughly 1 kilometer per second.
That’s where a laser comes in handy.
“You don’t want to be chasing an ICBM — you’re going to lose that game,” said Thomas Karako, director of the Missile Defense Project at the Center for Strategic and International Studies. “The nice thing about the laser is that, even with a limited range, it's going to have an instantaneous reaction.”
The American Navy has already developed a laser weapon that can shoot drones out of the sky from a warship.
And back in 2010, an airborne Boeing 747 with a massive laser gun successfully shot down a missile over the Pacific. After just a few seconds, the energy beam created a stress fracture in its target that caused the missile to break apart mid-flight.
Yet while this approach works in theory, and even in limited practice, the key problem has been designing a laser weapon system that’s both powerful and small enough to fit on a drone. The Defense Department’s program to outfit a lumbering Boeing 747 with a laser weapon was retired in 2012 after 16 years and billions of dollars in spending.
“It’s not enough to build a high-powered laser, you have to stick it on an airplane,” Scharre said. “That becomes a difficult technical problem.”
For the moment, it’s still not clear whether a laser-drone solution might be right around the corner, or over a decade away, said Scharre.