quicksilver
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Where Chemistry & EMP Combine
Below is a Austrialian design for a EMP (electro-magnetic-pulse) device that I found. I wanted to get some opinions on the unique nature of using
energetic materials to generate EMP device weapons. The theory is sound and quite interesting if one thinks of the chemistry of energetics deploying
electro magnetic energy.
---- what do y'all think?
Los Alamos had some of the best of these designs. Unfortunatly they are not for public desemination......
Attachment: apjemp.pdf (231kB)
This file has been downloaded 1980 times
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franklyn
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The paper you cite had been refenced before first by Irc in this related thread
http://www.sciencemadness.org/talk/viewthread.php?tid=6032
then further down in my post here _
http://www.sciencemadness.org/talk/viewthread.php?tid=6032#p...
I cite this same version you do here _
http://www.airpower.maxwell.af.mil/airchronicles/kopp/apjemp...
along with some other papers below that.
Research in this area is sensitive due to its close bearing to directed energy
weapons applications. I have not seen yet much besides what was news 40
years ago.
To summarize the construction of the simpler design :
The idea in the construction of a Flux Compression Generator is to use a fast
explosive to rapidly squeeze a magnetic field, transfering much of the energy
from the explosion into the magnetic field.
An explosively expanded tube serves as the armature, this is surrounded by a
helical wire coil, which forms the stator. As the detonation proceeds along the
length of the tube, it closes and progressively shortens the circuit loop with the
stator coil. This propagating short has the effect of trapping an initial feed
current and compressing the magnetic field, inducing ever increasing current in
the coil, while reducing the overall inductance. The result is that such generators
will produce a ramping current pulse. The resulting ElectroMagnetic Pulse is in
effect an electromagnetic shock wave. The field is sufficiently strong to produce
a transient pulse of thousands of Volts ( kiloVolts ) in nearby electric conductors
and components, causing irreversable damage to electronic equipment.
[color=darkblue]The possibility of having an electrically polarized explosive which would make it
peizoelectric occured to me. If detonated in the above scheme from both ends
simulataneously, this would provide the feed current, simplifying and making
such a device self contained. The pulse developed can be tapped with a pickup
coil nearby to supply extreme high power on demand.[/color]
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quicksilver
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I find it so damn facinating that such a thing would exist - I was quite taken with it. I wonder if such a thing could not be scaled down ???? I'm
glad folks had a chance to look at it.
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nitro-genes
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Although I'm quite a noob when it comes to electricity, I wonder how you could synchronize the initial pulse of the start current with the
shortcircuiting of the armature and coil reliably? Or am I completely missing the point here? 
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12AX7
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Simple. The inductor is an inductor, and you could short it to a capacitor, perhaps with an explosively driven switch (doesn't have to turn off, eh?)
or spark gap, forming a resonant circuit. You know exactly when the current reaches peak because it's 1/4 of a cycle, and you know the inductor's
inductance and the capacitor's capacitance. At that point, short the inductor (so the current keeps flowing and the capacitor is out of the circuit)
and light off the explosive (give or take a few microseconds).
Tim
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nitro-genes
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I'm afraid you lost me at the point of the 1/4 of a cycle  I was wondering though
what would happen if the initial start current would be supplied by another EPFCG. If I understand it right, the total poweroutput depends on the
number of coil turns and the initial current. But even with a large number of windings this would mean that you would still need an incredibly large
initial pulse, wouldn't it?
There is even an entree for the "Explosively pumped flux compression generator" in wikipedia. And even better, it links to a Los Alamos paper
describing the theory behind the device in detail. I wonder if it was someone from here or roguesci that made that entree available...
-->http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator
Supposedly, An EPFCG package that could be easily carried by a person can produce pulses in the millions of amperes and tens of terawatts, exceeding
the power of a lightning strike by orders of magnitude. Saw some rumours on the net that american military may have used an EPFCG device to disrupt
the main televison station in Irac, dunno if it's true though...
[Edited on 20-12-2006 by nitro-genes]
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Twospoons
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The whole idea of the FCG is to extract energy from the explosive - fast. The initial current doesn't have to be that great. At any rate, putting a
big current into an inductor is very easy. The electric fence energiser I designed years ago put a 2000A, 100uSec pulse through the output
transformer primary (every 1.5 seconds). The whole thing was about the size of a shoebox( including transformer), and none of the electronics was
particularly exotic.
Helicopter: "helico" -> spiral, "pter" -> with wings
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Boomer
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IIRC the amplification factor you get out of the HE is 30 for good designs, and 10 would be good for homebrew me thinks. Where are you going to take a
few million gigawatts from in a portable design, to get terawatts out?
As Twospoons stated, some kiloamps are easy, say 10-20kA possible. Ten times that will destroy your multimeter at some meters (*), but will not give
terawatts, especially not *radiated* power. You loose some when you transfer it out of the shorted coil, hence mil designs have antennas coupled to
the output.
(*) I once grilled my meter by discharging a 8kV/4kA cap bank (surge generator for EMC testing) into a coilled-up extension cord! It was NOT
connected, no leads plugged in, neither switched on.
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quicksilver
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| Quote: | Originally posted by Boomer
(*) I once grilled my meter by discharging a 8kV/4kA cap bank (surge generator for EMC testing) into a coilled-up extension cord! It was NOT
connected, no leads plugged in, neither switched on. |
THAT'S incredable! How far was the wire from the meter?
I know this whole issue is a workable concept for mil applications but it just seems so fantastic. I tried to get more info on this subject but came
up against a wall. I suppose it's still in use, etc, etc.
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Levi
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It seems like a shame to destroy the inductor in the process. Is it possible to compress the flux without blowing the coil to bits so it could be
used repeatedly? A FCG doesn't have much of a practical future (outside of weaponry) if it can't be reused. Perhaps a coil of uninsulated wire could
be passed a large current and a metal slug could then be explosively shot through the middle so as to short circuit without destroying the coil.
Would such a setup work or have I completely misunderstood the concept?
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12AX7
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How about this:
Make a winding out of square copper. Discharge a reasonably large capcitance into it. At a current maxima, squash the coil, shorting it. The coil
suddenly becomes a single turn and the current continues to circulate.
Hmm. Now you've got current, and it'll just decay by the copper's resistance. You've got more current, but fewer turns; the same cross section.
There's no (or practically no) voltage on the capacitor since you shorted it at a current maxima = voltage minima, so it doesn't matter. The coil is
somewhat shorter, but it can't be by much in a sufficiently short time unless you use explosives to actuate it.
Methinks the explosion is necessary to literally blow it up. Although, I neglected the armature, which is a "shorted turn" all along; it just shorts
more turns.
Hmm. A current in the primary winding causes an inverse current in the (shorted) secondary winding (the armature). Therefore, when the two are
shorted together (regardless of the primary being one or many turns), the current suddenly brick-walls and the magnetic field dies, releasing a bit
more EMP. There really isn't a good way to do this besides expanding the armature into the coil!
A big radiator is always a good way to make RF. You'd be well off by making a large loop and exciting it with things. Radiators tend to be resonant,
though, the opposite of a pulse sort of thing.
Tim
[Edited on 1-26-2007 by 12AX7]
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franklyn
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Explosively Driven Pulsed Power: Helical Magnetic Flux Compression Generators
Andreas A. Neuber - 7,8 Mb , pdf
http://depositfiles.com/en/files/2807924
While the basic operating principles of Helical Magnetic Flux Compression Generators
are easy to understand, the details of their construction and performance limits have
been described only in government reports, many of them classified. Conferences in
the field of flux compression are also dominated by contributions from government
(US and foreign) laboratories. And the government-sponsored research has usually
been concerned with very large generators with explosive charges that require
elaborate facilities and safety arrangements. This book emphasizes research into small
generators (less than 500 grams of high explosives) and explains in detail the physical
fundamentals, construction details, and parameter-variation effects related to them.
A related thread here on a pulse generator that can provide the necessary feed current
http://www.sciencemadness.org/talk/viewthread.php?tid=6032
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tito-o-mac
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have some pics here to give you all some idea what an Explosively pumped flux compression generator looks like.
Hollow tube generators
In the spring of 1952, R.Z. Lyudaev, E.A. Feoktistova, G.A. Tsyrkov, and A.A. Chvileva undertook the first experiment with this type of generator,
with the goal of obtaining a very high magnetic field.
The MK-1 generator functions as follows :
A longitudinal magnetic field is produced inside a hollow metallic conductor, by discharging a bank of capacitors into the solenoid that surrounds the
cylinder. To ensure a rapid penetration of the field in the cylinder, there is a slot in the cylinder, which closes rapidly as the cylinder deforms;
The explosive charge placed around the tube is detonated in a manner that ensures that the compression of the cylinder commences when the current
through the solenoid is at its maximum;
The convergent cylindrical shock wave unleashed by the explosion produces a rapid contraction (greater than 1 km/s) of the central cylinder,
compressing the magnetic field, and creating an inductive current, as per the explanation above (the speed of contraction permits, to first
approximation, the neglect of Joule losses and the consideration of the cylinder as a perfect conductor).
Helical generators
Helical generators were principally conceived to deliver an intense current to a load situated at a safe distance. They are frequently used as the
first stage of a multi-stage generator, with the exit current used to generate a very intense magnetic field in a second generator.
The MK-2 generators function as follows:
A longitudinal magnetic field is produced in between a metallic conductor and a surrounding solenoid, by discharging a battery of capacitors into the
solenoid;
After the charge is ignited, a detonation wave propagates in the explosive charge placed in the interior of the central metallic tube (from left to
right on the figure);
Under the effect of the pressure of the detonation wave, the tube deforms and becomes a cone which contacts the helically wrapped coil, diminishing
the number of turns not short-circuited, compressing the magnetic field and creating an inductive current;
At the point of maximal flux compression, the load switch is opened, which then delivers the maximal current to the load.
The MK-2 generator is particularly interesting for the production of intense currents, up to 108 A (100 MA), as well as a very high energy magnetic
field, as up to 20 % of the explosive energy can be converted to magnetic energy, and the field strength can attain 2 × 106 gauss (200 T).
The practical realization of high performance MK-2 systems required the pursuit of fundamental studies by a large team of researchers; this was
effectively achieved by 1956, following the production of the first MK-2 generator in 1952, and the achievement of currents over 100 megaamperes from
1953.
Disc generators
A DEMG generator functions as follows:
Conductive metallic discs, assembled in facing pairs to create hollow modules having the form of a lined torus, with explosive packed between pairs of
modules, are stacked inside a cylinder;[4] the number of modules can vary according to the desired power (the figure shows a device of 15 modules), as
well as the radius of the discs (of the order of 20 to 40 cm).
Current runs through the device, supplied by an MK-2 generator, and an intense magnetic field is created inside each module.
When initiated, the explosion begins on the axis and propagates radially outwards, deforming the disc shaped protuberances with triangular section and
pushing them away from the axis. The outward movement of this section of conductor plays the role of a piston.
As the explosion proceeds, the magnetic field is compressed in the inside of each module by the conductive piston and the simultaneous drawing
together of the inner faces, also creating an inductive current.
As the induced current attains its maximum, the fuse opening switch fuses and the load switch simultaneously closes, allowing the current to be
delivered to the load (the mechanism for the operation of the load switch is not explained in available documentation).
Systems using up to 25 modules have been developed at VNIIEF. Output of 100 MJ at 256 MA have been produced by a generator a metre in diameter
composed of 3 modules.
Here are the images:
Mk 1 generator
MK-2 generator
Disc generator
[Edited on 26-1-2008 by tito-o-mac]
[Edited on 26-1-2008 by tito-o-mac]
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franklyn
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LOKI, INC.
1006 Kingshighway
Rolla, MO 65409
Phone: (806) 742-4779
PI: Dr. Sergey I. Shkuratov
Topic#: Army 06-204 Awarded: 15NOV06
Title: Miniature Explosive Pulsed Power for Missiles and Munitions
Abstract: The proposed effort extends work recently completed (in 2003) at the
University of Missouri - Rolla (UMR) and at Texas A&M University (TAMU) under the
"Explosive-Driven Power Generation for Directed-Energy Munitions," Topic 11 of the
DoD FY 98 Multidisciplinary Research Program of the University Research Initiative
(MURI II). It also leverages the current efforts by Loki in FCG development under
an Army SBIR Explosive Pulsed Power Project (Contract W9113M-04-P-0016). The
Principal Investigators (PIs) at each of these institutes are currently the Loki PI,
Co-PI, and the PI for the subcontractor, Ktech Corporation. We also intend to
leverage the current Loki efforts to create a successful entirely explosive-driven
FCG system, utilizing an explosive-driven Ferromagnetic Generator (FMG) to
establish the seed current required by an FCG for operation. We are aware of no
existing compact, autonomous, completely explosive high power system based on
an FMG seed source for an FCG apart from the Loki system. At the successful
completion of the proposed work, we will have constructed hydrodynamic models
of FCG processes, and tested FCGs to check the results from those models. As
higher-performance explosives become available, we may evaluate their use in FCGs.
Design of Explosive Driven Ferroelectric Pulse Generators with Outputs Exceeding 200 KV
http://www.webstracts.com/ppc2005/papers/10654.pdf
Explosive Driven Power Generation for Directed Energy Munitions
http://handle.dtic.mil/100.2/ADA420276
redirects to:
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA420276&Locati...
Related thread
http://www.sciencemadness.org/talk/viewthread.php?tid=6032
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