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quicksilver
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Electrical Conductivity of Energetic Materials
There have been some papers written & research done on the subject of electrical conductivity of energetic materials. Most notably that of HE
compostions w/ metalic elements; when found that there was an element of resistence, with that material. Obviously metalic based molocules such as
lead styphnate proved to be conductive and one patent for a "bridge-wireless" squib was as simple as Pb styphnate 95% and Graphite 5%.*
The study I found most interesting was of Physical-Chemical Transformations in Detonation by Electric-Conductivity Method (Russian work, translated).
This study allow the tracking of detonation waves in the Nonel-type shock tube as an example with HMX-Al as well as the differing type of detonation
in TNT using similar monitoring gear. The study in question was a goverment funded research grant and the equipment was very sofisticated but with a
simple power supply and measuring equipment there can be some very interesting experiments preformed by the hobbyist
What I had was a Fluke MultiMeter and various powder supplies.
Many of the experiments in energetic research labs use Joules as a unit. I had a tough time with this as I didn't think that Joules had a direct
corrisponding electrical equivelancy. I have also noted that commercial blasting machines also use Joules as a means of measurment (I have yet to
understand exactly why, when dealing with # of caps a machine can detonate, Joules are the approprate yardstick).
Be-that-as-it-may, I designed a series of experiments from various power sources as well as means of measurments with a simple multimeter and had some
interesting results. Most are awair that the resistence of a bridgewire provides energy
which stimulates energetic material. EBW units and standard bridgewire units are basically the same in that sence. If energy is applied directly to an
energtic material it is the foundation of the study that the detonation wave may be monitered more exactly. For some materials this is an easy task.
For others, much more challenging.....but it may be that every energetic material may be stimulated to the point of activity by some level of input
energy.
I am trying to find the damn paper as I am writing this as I want to provide a background for what I think would be a series of very interesting
experiments.
Anyway I will post the bridgewireless patent and if anyone can find the paper by Gilev and Trubachev, please let me know what the name of it
is....I'll post it with the series of experiments I have done that co-incide with it.
Anyway in a nutshell, a simple "stun-gun" circuit or something simplar with cap-discharge will provide enough energy to detonate a varity of materials
and I would like to know how these things are measured and why a detonation occurs when the input energy isa varience from static electricty to a full
amp (or greater) shock of 800 volts or more.
Most people know that static electricy can detonate certain materials from AP to flash compostion but I found it facinating that simple 60cycle 120
volt energy could stimulate Hg Fulminate and a host of other materials. The paper pointed that a secondary explosive such as TNT could be stimulated
in such a way as could picric acid.
To me this whole concept is broad and interesting but I don't have my thoughts together on this as it's New Years day and I am somewhat relaxed.
*
Which, by the way is very workable. By altering the percentages + or - .1% it has been the most productive bridgewireless electric match one could
imagine.
In the art of pyrotechnics the standard for a bridgewireless Electric Match is:
KCLO3 57.25%
Graphite / conductive lampblack 27.25%%
PbO2 9%
Al (Ekhrt 5413) 5%
Mg 5%
Manganese Dioxide 1%
Attachment: bridge-wire-less.txt (29kB)
This file has been downloaded 1338 times
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12AX7
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Er, well, one joule is the energy of exactly one coulomb of electrons accelerated to a velocity corresponding to 1eV (i.e., falling through an
electric potential of 1V).
Electrical detonation isn't that hard to imagine, especially in nonconductive materials. Consider applying a voltage between two electrodes, in
excess of the breakdown voltage. Electrons force through in nanoseconds, bouncing off atoms and molecules as they pass. Atoms are ionized by the
collisions, and molecules decomposed. This alone may be enough, since as the atoms fall to lower energy states, they form more stable molecules,
releasing energy in the process. Although the recombination may take as long as a milisecond, the spark itself can be much faster than a microsecond.
The expansion in that time could undoubtedly cause a small shockwave sufficient to sustain the explosive.
A peak of 1 ampere (or more is easily achieved) at 800V corresponds to a peak power of 800 watts, but such a pulse only 10 microseconds in duration is
a mere 8 milijoules, easily stored in a capacitor of say 22µF charged to 27V.
For resistive materials, you have some amount of loss. The advantage of sparking is the breakdown is sudden, like imploding a plutonium critical mass
in an atom bomb, as compared to sitting it lazily together inside a reactor and letting it do its thing. Likewise, you might cook off a bit of the
composition, but if it isn't fast enough, you may not get a detonation.
This can, of course, be solved with booster materials, such as starting with a thermally sensitive deflegrating composition which ignites a primary,
heat sensitive explosive.
For increasingly conductive materials, pulse current goes up, while pulse voltage goes down. Thermal (joule) heating takes over when voltage is too
low to cause electrical breakdown in the material. With sufficient voltage and current, peak power can be had in a similar range for similar pulse
lengths and thus pulse energies, ultimately allowing the same sort of impulse to be delivered.
Just my electro-physical thoughts on the matter (and an unusually long post owing to my tiredness)..
Tim
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sylla
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Several months ago I started a study about the sensibility of energetic materials upon sparks. Unfortunately I lost the results sheet so I'll have to
do it again when I have spare time...
The device is quite simple, high voltage is fed into big capacitors and then two tiny edged connectors are placed near the explosive until there is a
spark. The experiment is done 10 times at differents voltages (10Volts, 20Volts, 30Volts, 40Volts, ...) using constant capacity. The power stored in
the capacitors can be found using the well known formula W = .5CV². Then explosives can be compared with their respective "spark energy of
activation". You'll find that @ 1.25J (from memory) 50% of the samples of nitrocellulose blow up. You'll also find that peroxides are really dangerous
and sensitive...
The interresting part comes in the device itself. It is very easy and cheap to build once you can do your own PCBs. You start with 9V or 12V DC from
batteries, so far it is very common. Then you send that current to an alternator to make it AC. It is very easy to build too, with a NE555 for the
clock connected to a NOR gate for the inverse. Using the output of the nor gate and the output of the clock you have something that goes 9V on one
wire and 0V on the other wire and it changes, 0V on the first wire and 9V on the second wire, and so on. I recommand using 10kHz to 15kHz frequencies
(because of the capacitors in the greinacher scale). The square 9V AC current is the easiest and cheapiest part of the design. Now come the GREINACHER
scale. It's something very great that increase your voltage using only capacitors and diodes. You can go up to 400V with about 15€ from 9V~12V. Then
the result is made "plane" using a diode and the result is put in big big capacitors; they are expensive. By linking a voltmeters to the capacitors
you know their charge, apply the spark and blow your hands up.
If someone is interessted in the greinacher I can upload the PCB and some pics of the device.
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jpsmith123
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| Quote: |
Many of the experiments in energetic research labs use Joules as a unit. I had a tough time with this as I didn't think that Joules had a direct
corrisponding electrical equivelancy.
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Energy is energy is energy; it doesn't matter whether it's mechanical, electrical, chemical, etc.
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I have also noted that commercial blasting machines also use Joules as a means of measurment (I have yet to understand exactly why, when dealing with
# of caps a machine can detonate, Joules are the approprate yardstick).
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Is there a better way to do it?
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Be-that-as-it-may, I designed a series of experiments from various power sources as well as means of measurments with a simple multimeter and had some
interesting results.
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Experiments regarding what?
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Most are awair that the resistence of a bridgewire provides energy which stimulates energetic material. EBW units and standard bridgewire units are
basically the same in that sence. If energy is applied directly to an energtic material it is the foundation of the study that the detonation wave may
be monitered more exactly. For some materials this is an easy task. For others, much more challenging.....but it may be that every energetic material
may be stimulated to the point of activity by some level of input energy.
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Well I would hope so.
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I am trying to find the damn paper as I am writing this as I want to provide a background for what I think would be a series of very interesting
experiments.
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Which paper are you referring to, this one?
http://www.math.rpi.edu:16080/faculty/Kapila/OSX/REVIEWS/DET...
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Anyway I will post the bridgewireless patent and if anyone can find the paper by Gilev and Trubachev, please let me know what the name of it
is....I'll post it with the series of experiments I have done that co-incide with it.
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You were somehow measuring the conductivity of detonation products?
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Most people know that static electricy can detonate certain materials from AP to flash compostion but I found it facinating that simple 60cycle 120
volt energy could stimulate Hg Fulminate and a host of other materials.
The paper pointed that a secondary explosive such as TNT could be stimulated in such a way as could picric acid.
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I can understand primary explosives being caused to detonate by joule heating from an electric current, but you're claiming that insensitive secondary
explosives like TNT or Picric acid can be similarly "detonated" by the casual application of 120 V, 60 Hz AC?
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quicksilver
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| Quote: |
I can understand primary explosives being caused to detonate by joule heating from an electric current, but you're claiming that insensitive secondary
explosives like TNT or Picric acid can be similarly "detonated" by the casual application of 120 V, 60 Hz AC? |
No, not a claim but a query....could that be possable? And certainly not limit the concept to one range of energy but from a general perspective;
could secondaries be so detonated? EBW dets come close to the concept that one would imagine that such a thing is more than possible but has been
utilized in various applications.
I would love to get more info on the subject as it seems really unique.
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Boomer
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Given enough confinement and material, you might start a cook-off that leads to detonation of the TNT/PA after some time. Detonating it from the mains
power directly is very unlikely.
IIRC PETN is the only material useable for EBWs (except for some new ones with super-high-surface RDX) because it needs least energy. And even those
need several hundred amps from a cap charged to some kilovolts. They are safe towards mains voltage, though they might deflagrate and burst open.
These use a 1.5 mil gold wire 40 mil long. My tests with a TR5 fuse (much thicker and longer bridge wire) showed a *threshhold* of 1kV / 1kA, and got
reliable at 1.5kV/1.5kA. The current is reached in under a microsecond btw, i.e. power rises at several TW/s, that is why (slow) photo flash
capacitors wont work!
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jpsmith123
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| Quote: | Originally posted by quicksilver
No, not a claim but a query....could that be possable? And certainly not limit the concept to one range of energy but from a general perspective;
could secondaries be so detonated? EBW dets come close to the concept that one would imagine that such a thing is more than possible but has been
utilized in various applications.
I would love to get more info on the subject as it seems really unique. |
As I understand it, an EBW detonator merely substitutes the sudden release of electrical energy for the sudden release of chemical energy in creating
the same old boring shock wave used to initiate a secondary explosive (thereby eliminating the need for a primary explosive). IOW, I don't think there
is some mysterious property of electricity whereby you can just stick some electrodes on a lump of TNT, apply some handy voltage, and have high order
detonation.
Moreover, AFAIK, being that EBW detonators have typical useful input energies of perhaps 1 or 2 joules maximum, the shock wave they provide is rather
weak, requiring a relatively sensitive secondary at low density.
Maybe we should start a thread regarding primary-less detonators? I've seen some interesting patents for such.
I don't remember if I've saved them or not...I'll have to look.
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Microtek
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EFI's ( exploding foil initiators ) are capable of initiating very insensitive secondaries such as HNS which is about as sensitive to impact as TNT.
I don't think there can be any doubt that it is possible to initiate any explosive via direct electrical stimulation if a sufficiently powerful
discharge is used, the question is just if it is practical ( and by definition this is not a discussion of the practical applications of explosives...
). Likewise, other methods of shocking an explosive can be used such as laser pulses.
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quicksilver
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I am quoting "12AX7":
"One joule is the energy of exactly one coulomb of electrons accelerated to a velocity corresponding to 1eV (i.e., falling through an electric
potential of 1V)"....This is something I was not aware of...
If one looks at professional blasting machines (http://idealsupplyinc.com/) one of the things that is confusing is that they are rated in Joules. Is this the method voltage and current are
formulated to an energetic measurment such as Joules? Appearently this (Joules) is the standard of the industry and has a relationship to overall
strength of the machine (a 50 cap machine is rated as putting out 8 joules, etc). Everywhere one looks at professional equipment the rating is not
listed as "voltage/amperage" but Joules. If there would be such a formula to include material (and I believe there may be), would that not tell us
more about the sensitivity of the materials per se'? My point here is that to heat a bridgewire the focus would be on current: correct? If the
machines used today are formulated to work with the energy measurment of Joules does that not lead one to a concept of energy initation more complex
than just cooking a wire immersed in an energetic material? I am taking a leap here in assuming that the caps of today are engeneered to greater
degree than those of the 1950's.
[Edited on 3-1-2006 by quicksilver]
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12AX7
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| Quote: | Originally posted by quicksilver
Everywhere one looks at professional equipment the rating is not listed as "voltage/amperage" but Joules. |
Well, yeah... joules are ENERGY, and you presumably need ENERGY, in a given short duration (microseconds, giving however much POWER, where P = E / t),
to ignite a given explosive with some detonator or whatever.
Note that typical power levels are easily in the fractional-megawatt range. This shouldn't be suprising, though quantitatively you may just not be
aware of it. A candle has more energy than the same weight of any explosive, but the explosive has gobs more peak power.
But volts/amps. Volts are fine, but V * A = P. Amperes is a quantity of FLOW, which is PER TIME, hence WATTS. Volts times COULOMBS (a quantity)
however is in terms of energy. That now said, they could list, say, peak voltage output and energy, from which you could determine the remaining
value (charge (Q) in coulombs in this case), or they could list peak current, peak power and approximate pulse duration from which you can determine
the other values. These are useful from an electrical standpoint, but if you are only interested in using it to blowing shit up, you aren't going to
care about how many electrons pass through the discharge before the thing gets 'splodey, and that's probably why they don't specify.
Tim
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neutrino
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Just to quantify and clarify this whole watts/joules thing:
96485.3415 Coulombs = 1 Mole of electrons
1 Volt = 1 Joule / 1 Coulomb
1 Amp = 1 Coulomb / 1 Second
1 Watt = 1 Volt * 1 Amp
1 Joule = 1 Watt * 1 Second
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franklyn
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Just goes to show you can get anything to detonate if you put enough juice through it.
See the amazing exploding watermelon ->
http://www.powerlabs.org/images/watermelon.jpg
Hmm what if you used a Dill Pickle
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not_important
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| Quote: | Originally posted by franklyn
Just goes to show you can get anything to detonate if you put enough juice through it. |
As can be demonstrated by getting a fairly small diameter wire across two phases of a 250 KV power line. Not only can copper be made to explode, but
so can ordinary air.
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Hennig Brand
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To convert from capacitance and voltage to joules is done with this formula normally.
Energy(in joules)=0.5 x capacitance x square of voltage
note:capacitance is in Farads not uF, which is usually how caps are rated.
There maybe some other formula and consideration for the blast machine, I don' t know. It is also the square of the voltage that the capacitor is
charged to, not the square of the voltage rating on the side of the cap. It is the same as the kinetic energy formula, in that if the velocity(in this
case voltage) is halved, the energy goes down by a factor of 4, or 1/4 the amount. If you double the voltage, you get four times the energy.
I built a stungun a couple of years ago, and it hurts bad to get shocked by it, but there is no serious injury, except maybe if one has a weak heart.
It has a 1uF@1000V capacitor, which is charged and dumped( I forget how many times a sec) through a trigger transformer which has a 50:1 ratio. So I
get about 50,000 Volts and 0.5J per pulse, assuming 1000V cap was fully charged(pretty typical for stungun/tazer). The point is the capacitors used
for EBW Bcaps can store massive amounts of energy that can be released explosively(as is the idea, eh). I have caps that are 2KV@25uF, so if these
where fully charged they would have the ability to deliver 50J, which can kill many times over, or do very serious damage at least. One joule as
pointed out is the equivalent of 1Wx1second, so if we divide one second by the fraction of a second that it takes to discharge/deliver that charge we
could multiply that by the 50J and get our approx, max, peak Watts. If switching is done properly, the discharge can be over in only a few
microseconds. Type of capacitor, and the configuration(how many and how large each is), and other all effect speed as well. So assuming a pretty fast
capacitor or bank of capacitors, lets say it takes 10usec., 50 divided by 0.00001 gives 5,000,000 Watts of power:! Which remember does not mean the capacitor has a great amount of total energy(much
less than a battery of similar size actually) but it can deliver that energy at a very high rate(like explosives).
http://www.kpsec.freeuk.com/capacit.htm
This page has some good basic info on capacitors, which I should read as well. I think I may have a bit of a capacitor phobia, but they are dangerous.
I am still going to play though, but carefully.
[Edited on 7-7-2009 by Hennig Brand]
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franklyn
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@ quicksilver
SOLID salts or molecular compounds, whether energetic or not are all dielectric ( insulators )
There are very few organic conductors , polyacetylene for example.
Indications of conduction reflect impurities present , such as carbon or metal particles ,
and moisture in the case of salts. Only explosives which are a liquid and ionic or that may
be acidic such as nitromethane will exhibit conductivity.
Placing a segment of explosive in between two metal foils forms a capacitor. If this is
subjected to an alternating current , depending on many factors such as the frequency of
applied signal , a primary explosive can be heated enough after about a minute to set it off.
Secondary explosives can only deflegrate , however the plasma now conductive can serve
as a path for an arbitrary source of current adding energy to enhance the reaction and so
perhaps could serve as an improvised bridgewire device in this regard. This is so far as I know
not an area investigated.
Quote: Originally posted by Boomer  | The current is reached in under a microsecond btw, i.e. power rises at several TW/s,
that is why (slow) photo flash capacitors wont work! |
@ Boomer
Only if an application requires great precision is a short time frame called for.
If a pulse width a millionth of a second is not needed, an electrolytic capacitor
can provide a pulse width a ten thousandth of a second as pointed out in this
thread -> http://www.sciencemadness.org/talk/viewthread.php?tid=12414
A very brief pulse requires a capacitor of very low ESR ( Equivalent Series Resistance )
Because capacitors with this property are of very small capacitance, to provide
enough energy to explode even a small 40 AWG wire , requires charging to a
very high voltage. Joules = ( C x V x V )/ 2 , , C = capacitance , V = voltage
If one is small the other must be high, or else reduce a wire to the smaller output.
.
[Edited on 8-7-2009 by franklyn]
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Mr. Wizard
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How much energy can be stored in a charged dielectric explosive? How many joules per gram? How does this compare with the chemical energy, and how
does it effect the speed of a shock wave? How would the current flow during a detonation interact with the conductive ionized gasses. Even if the
amount of energy in a dielectric was small, it might have interesting actions on the explosive, and nearby matter.
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Hennig Brand
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I just realized when reading your posts more carefully, and doing a little google searching, that my 25uF@2KV caps are probably less than ideal, too
slow. Maybe their massive size could make up for it to some extent, but from descriptions of blasting machines, they are too big and slow. According
to Wikipedia(not best source), a ball park figure for the cap is 1uF@5KV(I wonder if it is actually a bank) giving 12.5joules. This would be much ,
much faster than my 25uF cap, all things being equal. A 50 cap machine as described in one of Quicksilver' s posts above, and putting out 8 joules,
probably has a value for each capacitor much smaller than 1uF, assuming those high voltages(which seems to be a given). If I connected 2 of my 2KV
caps in series, I would have 4KV@12.5uF, giving me 100J(man we are in the defibrillater joule range now!). Boomer, what are you using for caps? Mine
are to big and dangerous, and not fast enough right? Good pulse capacitors are normally pulse rated as well aren' t they?
Just realized that boomer' s post was from quite a while ago, so it may be silly to ask. It was him though I think, that was doing some practical
stuff with this here and over at RS.
I don' t know if this is the right analogy, but trying to set of explosives with a large capacitance(slower), capacitor through exploding a bridge
wire, may be kind of like trying to set of dynamite with a large black powder blasting cap(lots of energy, but poor initiator).This may be an
exaggeration of what is going on in my case, and mine could work. The slower that you go the more energy is needed until at some point you can' t
initiate at all by that method. The slower capacitors I would say are unneccesarily dangerous, even if they do work, because of the extra energy
needed. It is hard to say what is in those metal cans that I have, it could be a bank in there(probably not though).
[Edited on 8-7-2009 by Hennig Brand]
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Hennig Brand
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Boomer has done a good job of explaining his equipement and procedures in primaryless detonators on this site. I left my last post as I think some of
it is of value. I have found that the most appropriate and common capacitors are probably the one' s used for switching power supplies. There are high
voltage (>1000v), switching supplies that are used but the caps for them are probably special order and expensive compaired to common, under 1KV
stuff. I called an electronics part place, and they had 0.1uF@1000V caps that were low esr, tough, and made for switching(not electrolitics). With a
few hundred dollars worth of these($5 each), or maybe only $100-200 in bulk or from a better vender, a person could make a very fast, tough blasting
machine. My idea was to do series pairs to give me 2000v and, then parrallel these pairs to give me more capacitance. It would take 80 caps to get me
8 joules at 2000v though. Seems a little impractical, but that is all the place I called could get easily. The best thing is to find some surplus
caps, that are still good. Surplus stuff, especially if it is specialty stuff can be purchased for pennies on the dollar. It might be hard to find for
many, but if one keeps their eyes open, and frequents these kinds of places, a lot of good stuff can be found. If you absolutely need the parts or
materials right now, it will usually cost much more.
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franklyn
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@ Hennig Brand
Fast ? Slow ? how did you establish this and what time frame are you citing ?
As I pointed out in great detail here
http://www.sciencemadness.org/talk/viewthread.php?tid=12414
ESR ( Equivalent Series Resistance ) is what determines the
discharge time. It is best to measure it but it can be calculated
to provide an estimate for a capacitor of known specification
from the manufacturer's given value of " Dissipation Factor " DF
http://www.illinoiscapacitor.com/uploads/papers_application/...
http://www.cde.com/catalogs/AEappGUIDE.pdf
E S R = DF / ( 2 π f C )
E S R = Equivalent Series Resistance
DF = Dissipation Factor
π = ' P i ' ~ 3.1416
f = frequency ( for an estimate use 10,000 * * )
C = capacitance
* * You really ought to derive frequency and with that the ' RC ' time constant from ESR
why it is best to measure it. Improvised oscilloscope methods without a dedicated LCR meter _
http://octopus.freeyellow.com/esr.html
http://octopus.freeyellow.com/99.html
All the way at the bottom see ' Scope ESR ' here _
http://www.anatekcorp.com/ttg/tiptrick.htm
It is possible to use your computer's sound card as an audio
bandwidth oscilloscope using only software , as outlined here _
http://www.zeitnitz.de/Christian/index.php?sel=scope_en
This next one is old from Windows 95 era, but it works
2 channel audio band oscilloscope.
http://www.tech-systems-labs.com/osc251.zip
_________________
- Instructional -
To get a sense for scope settings
and operations on a Hameg flash simulation
http://www.virtual-oscilloscope.com/simulation.html#
more orientation
http://www.doctronics.co.uk/scope.htm
a useful primer
https://www.cs.tcd.ie/courses/baict/bac/jf/labs/scope/oscill...
the last word - Tektronix
http://www.tek.com/Measurement/App_Notes/XYZs/03W_8605_2.pdf
P.S.
I just re-posted this
http://www.sciencemadness.org/talk/viewthread.php?tid=12414#...
.
[Edited on 8-7-2009 by franklyn]
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Hennig Brand
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You are right that I was not very precise in my explanation, and I don' t know everything(that is for sure), and its beem a while since I played with
electricity to. I own three oscilloscopes, but am not an expert on their use, mostly did a lot of audio experimenting. It could be done with a scope
you are right, being careful not to destroy the scope. It probably should be done at some point, but I don' t posses the capacitor bank that I
mentioned, and as of yet have not built a power supply to charge the 25uF@2KV caps, so they can' t really be tested either. The discharge rate
differences of the different sizes and types of capacitors is fairly well understood, at least well enough for a descent picture of what is
happening(you are right not exact science, but still not useless). The electrolitics(usually large capacitance), are on the slow side, usually many
times slower than the faster pulse and switching capacitors. The pulse and switching capacitors if assumed to be the same as what is used in blasting
machines, and in the sizes and voltages used in the blasting machines advertized have been referenced in encyclopedias and advertisements as having a
pulse that lasts a few microseconds or less even. Lets say RDX has about a 8000M/s detonation velocity, if that pulse lasts 4 micro seconds it will be
over before the detonation wave can travel 3.5mm. In the context of energetic materials, that is fast!
By the way on looking it up the 0.1uF@1000V caps I mentioned are mylar-foil, which are listed as a suitable type for EBW machines. I also used the
number of caps described in Quicksilvers post for a commercial blast machine and the joules, and went by typical voltage ratings( there is standards
for these machines). And using the mylar caps proposed a way to make a 2KV, 8J capacitor bank for blasting machine, which I think would be just as
fast and reliable as the proffessional version(same type and similar amount of caps), providing provision is made for good hook-up wire, etc and
switching(very important for best results). By the way I was also off by a factor of two I think for the number of caps needed to give 8J, it should
be 160, oops. This all should be tested of course, and I may, but till at least one of the caps is in my hand it is hinda hard. I was making some
assumtions, and I appologize but even in science I think that it often starts that way sometimes. Maybe I will be found wrong, through measurement.
Scientists today do take established data and use it, except under extreme circumstances they don' t test everything(or at least that is my feeling).
It has been a while since I made the call about those caps, as it was for another project, and I should have looked up some data on them. I do think
that the general idea can still be of use untill I have something better(actual measurements), and then still may prove of more practical value.
Thank you for the formula and links, they should prove useful.
Good news though my big 25uF caps are oil filled which means they could be on the fast side. The three best types for super fast pulses for EBW
according to wiki are oil-filled, Mylar-foil, or ceramic, of the several switching schemes to use to get the best advantage, spark-gap seems to be the
best/easiest for the hobbiest, even though from earlier reading I think I remember that it is only 60-70% efficient quite often(big thyristors can be
in high 90's). I promise to take measurements and get more data about this in the future. The two main types of capacitors I mentioned(electrolitics,
and switching/pulse) differ so wildly in their speeds though, I believe that comparative language without hard data can still tell us a lot. In the
end the "acid test" is going to be trying to making it work practically(I think), and seeing the results.
Have just seen the other thread. I did not see it before, my computer is slow, and I usually cut my searches a little too short because of it I guess.
I will read and try not to cause to much more trouble.
[Edited on 9-7-2009 by Hennig Brand]
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foxdrg
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joules are ENERGY, and you need ENERGY, in a given short duration.
To quantify and clarify this whole watts/joules thing:
96485.3415 Coulombs = 1 Mole of electrons
1 Volt = 1 Joule / 1 Coulomb
1 Amp = 1 Coulomb / 1 Second
1 Watt = 1 Volt * 1 Amp
1 Joule = 1 Watt * 1 Second
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franklyn
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Not exactly
A Watt is a rate.
A Joule , J = m^2•kg•s^ -2
According to NIST:
Watt , W = J / s which is m^2•kg•s^ -3
http://physics.nist.gov/cuu/Units/units.html
J = Ws only because W = J / s
according to you J = ( J / s ) s
so J = J s / s
or J = J
Duh.
It's more nonsensical if you substitute for J
then W = Ws / s
or W = W
We already know that , but what is W ?
W = J / s
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franklyn
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Patent - US 4206705 , Electric Initiator Containing Polymeric Sulfur Nitride
The preparation of the precursor for this is on page 438 - 439 of
Chemistry of Powder and Explosives , by Tenny Davis
called Nitrogen Sulfide there.
The series of transformations to obtain the polymer
http://en.wikipedia.org/wiki/Tetrasulfur_tetranitride
http://pubs.acs.org/doi/abs/10.1021/ja00855a012
http://en.wikipedia.org/wiki/Polythiazyl
Related thread _
http://www.sciencemadness.org/talk/viewthread.php?tid=10440
and another post _
http://www.sciencemadness.org/talk/viewthread.php?tid=14630#...
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Trotsky
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People frequently blame accidental detonation of TATP or HMTD on static electricity.
Years ago I wanted to test this so using a piezoelectric grill lighter, I arranged it so that I could place varying amounts of TATP in the sparks
path, figuring that this shock would be stronger than any static shock you'd expect could be possible from the situations I've heard described. I
figured this would be an easy way to detonate very small quantities which would usually deflagrate if burned or be almost inaudible over the sound of
the hammer if detonated by impact.
I must have tried it a hundred times with varying quantities of the compound. I never once managed to detonate or even ignite the tatp, which was dry
(it was recrystallized from acetone, so it had to be dry or the vaporized solvent WOULD have caught).
Even dipping one of the electrodes in MEKP did not accomplish the goal.
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franklyn
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" People frequently blame accidental detonation of TATP or HMTD on static electricity."
If there is no evident cause , it is the most likely cause. No one really knows or
can state with confidence how a particular event occurs if forensic evidence is
absent. The reason it is subject to testing. The fact that there are spontaneous
explosions reported is not in dispute, what is wanting is an explanation of it.
Organic peroxides being dielectric ( non conductors ), proximity to a momentary
minor electric arc can only have minimal thermal effect which your experiment
confirms is insufficient to initiate deflagration. This observation is verified in
independent investigation of this effect.
Attachment: Character of Sensitivity of Explosives to Electric Spark.pdf (892kB)
This file has been downloaded 748 times
( Refers to pyrotechnic powder which is subject to ignition on it's surface )
Then again your results will differ from someone else's.
Excerpt from => Non-Shock Initiation of Explosives
http://books.google.com/books?id=qIQETUT9r-QC&pg=PA594&a...
Initiation from static charge is due to an accumulated electric potential on the
mass of the peroxide, acting as a capacitive element as part of a closed circuit.
This is entirely different in character to the setup you describe, Trotsky
Secondary explosives are by definition largely immune to initiation from static.
Yet are the most studied relative to peroxides, so one must infer from those.
Dielectric Properties of some Common High Explosives
www.dtic.mil/dtic/tr/fulltext/u2/a404454.pdf
This does not eliminate and exclude primary explosives from susceptibility.
Static Charge Development on Explosives
http://publications.drdo.gov.in/gsdl/collect/defences/index/assoc/HASH0182/51aa3230.dir/doc.pdf
The piezo electric crystal of a grill igniter is struck sharply by a cocked striker.
This impact strains the contained piezo ceramic producing a high voltage potential
which sparks over the air gap at the tip of the igniter. The reverse occurs if
such an electrical potential acts on an explosive crystal having piezo electric
character. It will experience an equivalent mechanical effect sufficient in itself
to initiate a primary explosive sensitive to mechanical shock. Acutely affected
are dislocations, internal fault lines between differently oriented planes of
crystallization which are susceptible to stresses not otherwise affecting the
bulk material. Myriad scenarios can be imagined. While these hypothesis may
seem far fetched , they are subject to the probability for occurrence governed
by the large numbers of individual crystal particles in any given situation. It only
takes one potential circumstance out of the many to be realized. An explosion
is as possible as it's most susceptible point of initiation.
Dislocation Assisted Initiation of Energetic Materials
www.cecd.umd.edu/documents/technical-articles/armstrong-dislocation.pdf
Materials Science & Technology Aspects of Energetic (Explosive) Materials
www.enme.umd.edu/CECD/documents/technical-articles/armstrong-materials-science.pdf
Dislocation Mechanics Aspects of Energetic Material Composites
www.ipme.ru/e-journals/RAMS/no_11909/armstrong.pdf
http://connection.ebscohost.com/c/articles/5985417/dislocati...
http://udini.proquest.com/view/dependence-of-hotspot-initiat...
Attachment: Microscopic Initiation Mechanisms in Energetic Material Crystals.pdf (844kB)
This file has been downloaded 1170 times
Crystal Sensitivities of Energetic Materials
www.smf.phy.cam.ac.uk/Publications/Energetics papers/246EMWalleyMST22.pdf
Shock Induced Subgrain Microstructures as Possible Homogenous Sources of
Hot Spots & Initiation Sites in Energetic Polycrystals
www.aero.caltech.edu/~ortiz/Pubs/2010/RimoliGursesOrtiz2010.pdf
Initiation of Explosive Crystals by Shock or Impact
http://hal.archives-ouvertes.fr/docs/00/22/66/50/PDF/ajp-jphyscol198748C418.pdf
related thread
http://www.sciencemadness.org/talk/viewthread.php?tid=16381
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