Stardate 20030119.1530

(On Screen): Bradley writes to point me to an article describing one of the wizard weapons we may unleash in this war. The report is, typically, mangled and demonstrates that the reporter who wrote it was probably a liberal arts major, but it's possible to see through the reporter's confusion to the underlying weapon's characteristics.

They're referred to as HPM, or High Power Microwave, and they generate a very brief but massively powerful burst of microwaves.

HPMs can unleash in a flash as much electrical power—2 billion watts or more—as the Hoover Dam generates in 24 hours. Capacitors aboard the missile discharge an energy pulse—moving at the speed of light and impervious to bad weather—in front of the missile as it nears its target. That pulse can destroy any electronics within 1,000 ft. of the flash by short-circuiting internal electrical connections, thereby wrecking memory chips, ruining computer motherboards and generally screwing up electronic components not built to withstand such powerful surges. It's similar to what can happen to your computer or TV when lightning strikes nearby and a tidal wave of electricity rides in through the wiring.

The first sentence in this paragraph is nonsense. Power, measured in watts, is an instantaneous measurement of energy release. 1 gigawatt released for one microsecond is exactly the same as 1 gigawatt released for 24 hours. However, 1 gigawatt released for one microsecond is only 1 kilojoule, whereas 1 gigawatt released for 24 hours is 86.4 terajoules. But they're both a gigawatt, at least for a moment.

What the reporter got told was that the power level of the pulse was about the same as the power output of Hoover Dam (which depends on the flow of the Colorado but actually limits out at about 1.5 gigawatts).

Most of the rest of this is mangled, too. The zorch this releases may well be stronger in some directions than in others, but something like this is basically going to go in all directions and not just to the front.

It will indeed zorch semiconductors, and in a way similar to one of the effects of a lightning strike, but not the one this describes. When lightning strikes and hits part of the power grid, such as a telephone pole with a transformer on it, then some of the electricity from the strike will ride in onto the power lines. Even if it doesn't hit a power pole, it will temporarily change the electrical potential of the "ground" near where it hits, and since the electrical system is grounded everywhere, that also will generate a temporary blip since that can travel faster through power lines than it can through the ground itself, to even out the differential. That's the effect we defend against with surge protectors.

That's not what an HPM would do. Lightning has a different effect as well; it generates a huge burst of radio waves, photons at a wide variety of frequencies. That's why it is bright, and that's why you can pick it up with an AM radio. (If you're in a lightning storm some time, turn on your AM radio and tune to between stations; you can hear the lightning very clearly, including the majority which are up in the clouds and never come near the ground. FM isn't the same, and you won't hear anything with FM.)

The generic term for this is EMI; electromagnetic interference. Given that all wires are antennas, a sufficiently powerful burst of EMI can generate local electrical current flow of a sufficient magnitude to toast inadequately-shielded semiconductors, especially MOSFETs (which are extremely susceptible to overvoltages even at tiny current levels). Since MOSFETs are the foundation of most modern semiconductor designs, and with the increasing reliance on semiconductors in modern weaponry, the potential for this as a weapon in war is clear.

HPMs are man-made lightning bolts crammed into cruise missiles. They could be key weapons for targeting Saddam Hussein's stockpiles of biological and chemical weapons. HPMs fry the sophisticated computers and electronic gear necessary to produce, protect, store and deliver such agents. The powerful electromagnetic pulses can travel into deeply buried bunkers through ventilation shafts, plumbing and antennas. But unlike conventional explosives, they won't spew deadly agents into the air, where they could poison Iraqi civilians or advancing U.S. troops.

Again, what comes through here is distorted. An HPM isn't a lightning bolt (though they may be generating their flux with a big brief arc), but some of its effects would be similar. But if a weapon like this had sufficient area effect (the article says 1000 foot radius, which is not inconceivable) then it could deactivate the guidance electronics on missiles and the targeting computers on artillery, which would turn them into inanimate junk, and also deactivate a lot of other kinds of essential electronics. Any installation using electronic locks on its doors is obviously vulnerable.

It can't be guaranteed that this would not lead to a release of chemical agents, but it is certainly much less likely to do so than any kind of attack with explosives. And if there are indeed installations thought to be holding these kinds of weapons, and if we do have some sort of HPM system, I think they'd be near the top of the list of places to use them (right behind Saddam's bunker).

I'm sure that these are designed to be delivered by cruise missiles, but I doubt that'