From: Michael M. Butler (mmb@spies.com)
Date: Fri Feb 21 2003 - 20:35:41 MST
Greg Burch wrote:
> An article I can now only find on Drudge's archives:
>
>
> http://www.drudgereportarchives.com/data/2003/02/20/20030220_152033_flas
> h3.htm
>
> Reports on the U.S. military's reluctance to use what seems to be some
> kind of new non-nuclear EMP device because of concerns about damage to
> civilian infrastructure. This led me to wonder about the impact of EMP
> weapons on many of the weapon systems I see being developed, especially
> UAVs, other unmanned combat platforms and the generally fast-evolving
> C3I architecture of the future battlefield. If we can EMP them, what
> stops them from EMPing us? Aren't UAVs very exposed to EMP
> countermeasures? How difficult is it to make a big, non-nuclear EMP? I
> know some on the list must know why this isn't a no-starter ...
Can't answer you directly, but I can tell you some stuff I _have_ read that relates.
There are several remote-EM weapons types. Off the top of my head, and ignoring
overlap across categories for convenience, here are the ones I can think of:
There's plain vanilla nukes and tailored EMP-rich nukes, at least in principle.
These can be subdivided into supercritical (boom) and subcritical (fizzle) systems.
There's MHD-powered EM, both EMP and directed-microwave. Some of these configurations
destroy a baseball-style single loop coil and pinch exotic materials. In some designs
(don't know how practical), some of the stuff being squeezed is a subcritical nuclear
or thermonuclear "pit". In others, it's all conventional-explosives driven into a
big old supercapacitor, and it emits a cone of microwaves down the axis of the
low-drag bomb. I've seen drawings of that one.
Then there's HERF other than those sorts, for instance the weird but possibly-
practical-soon "ionize air columns with a pair of lasers, then run gobs of ~100-MHz
RF through the columns and induce secondary currents in the interior" one, and the
plain old "hit them with a gob of microwaves from a gutted Radarange and see if they
fall over/see if their receiver input stage fries" one.
http://www.lexingtoninstitute.org/defense/DirectEngery.pdf
has some stuff on microwave weapons. I love the typo in the URL.
What little I *do* know about this stuff comes from the FAS and one electronics
seminar. The seminar used EMP strictly to refer to NEMP--Nuclear EMP.
I think I have a copy of a paper around here somewhere called "EMP will do WHAT?!?"
(with the n-times-xeroxed smurfy guys rolling on the floor laughing, taken from the
ancient "You want it WHEN?!?" office art). All unclassified, but with some useful
hints. The paper was pretty much exclusively concerning nuclear weapons effects on
local systems; they didn't talk about zillions of volts being induced on long
telephone lines, etc. Let me recap what I think I know from that, about nuclear EMP.
When a nuke goes off, you get a brilliant expanding shell of gamma radiation, something
around 90 nanoseconds thick. That's what they said; I'm guessing the duration of that
is useable to measure yield in a nonlinear way.
EMP was described in that paper as AEMP and SEMP. A(tmospheric)EMP is to some degree
shieldable-against with one or more conductive (Faraday cage) layers. S(ystem)EMP, in
contrast, is vey hard to shield against.
AEMP: comes from the massive gamma burst of a nuclear fireball getting forward-scattered, ionizing the heck out of the air, being
reradiated by ionized electrons falling back to lower states, and consequently smeared
into a DC-to-daylight stretched pulse of (RF/EM) photons, with both a strong e field
and a strong b (magnetic) field.
SEMP: When the remaining gamma (and to a probably lesser extent, beta) penetrates into
the target, you get a buttload of EM, "bremmstrahlung" und so weiter, and the Faraday
shielding gets electrons knocked off of it just like any other X-ray-machine target.
With both, you can also get the circuits inside responding to the various induced/
produced currents as transformer secondaries.
A lot of EMP countermeasures boil down to "shunt what you can" (the "lightning
arrestor" approach), "be built to take it" (conservative design that can function after
degradation & damage), and "notice when you have latched up, and reboot" (scr-latching
is a thing that happens when you bias some ICs' PNPN structure funny--they chip turns
into a big "on" power switch and basically shorts the power supply until you _completely_
remove the juice).
Yes, UAVs are exposed. So are F-16s. There are always tradeoffs.
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