Pentagon Still Spooked By Space Attack

Defense Tech ^ | Nov. 4, 2004

[_Jim]

All most of us can go by is what we read, and there seems to be far fewer sources that support the contention that "EMP has been overstated."

BS.

The difference between you and I is: I know my field of expertise - AFAIC you're just a poster on the internet! (IOW, I know where to look for material to support my case.)

>On the contrary, an EMP will not really affect people, but it will do
>a good job of destroying most unprotected transistor circuitry. Old
>tube technology is pretty much immune.

That's the myth, but it has been pretty well discredited. For a normal low air burst or ground burst detonation, the EMP effects reach no further than the flash burn and blast effects, IE roughly 30 miles for the typical "city buster" bomb. In other words, if it cooks your radio, it'll cook you too.

For a very high altitude detonation, EMP effects can spread over a wide area outside the range of flash burn and blast effects. But to be damaged, electronic equipment needs to be connected to fairly long unprotected exposed conductors in order for enough voltage to be induced to cause breakdown.

The ARRL published tests on a number of amateur radios, tested in a military EMP simulator, to see what would typically happen in such a case.

Battery powered VHF/UHF equipment using a "rubber ducky" antenna was immune to damage.

Equipment connected to unprotected mains power suffered power supply damage.

And HF equipment connected to unprotected outside antennas suffered receiver front end damage. For solid state equipment, this damage was to the first RF stage transistor, for tube equipment, it was damage to the first stage grid resistor. No transmitters suffered damage.

And there is effective EMP protection available. EMP can be considered merely as a fast risetime form of nearby lightning strike. In both cases, an induced surge enters the equipment via a long exposed conductor. If you are using good lightning surge protection with fast risetime protectors, such as the EMP rated units sold by Polyphaser (and others), and have practiced the kind of station layout I've preached about here many times, there should be no more cause for concern about EMP damage than from lightning surge damage.

Thanks to inverse square effects, an EMP detonation at a 200 mile altitude, the ideal height to maximize EMP effects, has a field strength at your antenna about equivalent to a lightning strike at 7 miles. But the effect on very long exposed conductors, like the power grid or the telephone grid, is as if there were simultaneous lightning strikes 7 miles from *every* point of the grid. This causes a huge voltage to develop on these extended grids, and can cause severe damage to them. Your radio and antennas don't represent such a widespread grid, so they are only subjected to the equivalent of a single lightning surge.

In any case, if you were to suffer EMP damage, the receiver and mains power supplies would be the most likely candidates for damage. CW transmitters offer you no advantage in either of those cases since you still need a working receiver and power source to establish communications regardless of operating mode.

And frankly, for some time (perhaps years) after a massive exchange of nuclear weapons, HF would be useless thanks to disruption of the ionosphere. Only VLF would work for long range communications, which is why the military operates VLF stations for nuclear command and control. VHF+ would continue to work for short range communications. Since neither typically uses Morse, Morse knowledge would be virtually useless after a nuclear exchange.

EMP

[Joe Hadenuf]

I guess what I am trying to say is if an unknown object, the size of a golf ball or screw, enters our orbit, chances of *anyone* detecting it, let alone tracking it, are very unlikely. I think it's safe to say, there are probably tens of thousands of *small* objects orbiting the earth, that they haven't a clue about.

[1Old Pro]

If anyone shoud be worried, it should be everybody BUT us. Afterall, we have the ultimate satelitte "plucker" with the shuttle.

[Indie]

and allow resident experts in the field refute or support it with documentable fact.

Your sarcastic self-importance missed the very fact that "you" were the type expert I was appealing to for imformation.

And since all the rest of us are just "posters on the internet" and you are the know-it-all, we shall defer the thread to you, your eminence.

[Joe Miner]

You know you have your surge suppressor on your computer? Trust me, every box in a plane or missile has EMP suppressors on every wire entering the box.

Would they hold up during a real EMP event? I don't know, all I know is we were required to waste space and money including all that crap into anything we designed.

[RightWhale]

Saw a NORAD or SAC claim several years ago that they knew of everything bigger than a nickel between the earth and the moon.

[RadioAstronomer]

Would they hold up during a real EMP event?

Not a chance on Planet Earth.

[RadioAstronomer]

If anyone shoud be worried, it should be everybody BUT us. Afterall, we have the ultimate satelitte "plucker" with the shuttle.

Nope. Limited inclination and altitude.

[RadioAstronomer]

Note: I was referring to you surge supressor at home.

[RadioAstronomer]

I have a pretty good idea for a post on this subject when I get out of the lab and can put all my notes and papers into a paragraph.

I worked with the DNA (Defense Nuclear Agency) testing an EMP hardened facility back in the 80s.

[blam]

"However, trying to fire them through the Earth's atmosphere a long distances (to space) and expecting them to do much is another story."

How about if they're in a high flying aircraft? (albeit - a large aircraft)

[RightWhale]

Would they hold up during a real EMP event?

< To a small degree. All electronics has to be hardened, that is, shielded really well, and every electronic device has to withstand a substantial current that would fry almost any transistor instantly. Old tube type radios and old distributor type cars might survive.