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Ral123
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I'm worried about the high flammability of Tetryl and RDX if used in their sensitive crystaline form, I don't know what to say about massing up TNP
and DDNP for boosters :/ It reminds me of a mixture called APAN 
I've considered using lead picrate contaminated with TNP as a base charge when the primary is weak.
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Hennig Brand
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DDNP is one of the least sensitive primaries, reasonably stable and compatible with picric acid. I wouldn't compare a mixture of DDNP and picric acid
to APAN. Picric acid, judging from pretty much everything I have read, is only a little more sensitive than TNT. Tetryl is much more sensitive than
TNT. I can look up some figures and post them if need be, but they are easy to find. My picric acid does seem a little harder to initiate than I feel
it should be, but it tests very close to pure by melting point.
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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DubaiAmateurRocketry
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is 5-Nitrominotetrazole a suitable primary? it has a high VoD and acceptable impact sensitivity of 6cm H50 2.5 kg drop height
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Ral123
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The APAN comparison was a bit of trolling, the TNP/DDNP mixture will be much more stable, robust and powerful, surely can be a basecharge.
If 0,5g of primary cant set off TNP while surrounded by all that metal, I can't consider it reliable. Don't get me wrong, it surely hits much harder
then AP, but considering my success to initiate TNP with it, with the confinement of cardboard, I think something is not right with the DDT of your
DDNP. Only the DDNP in your setup has more energy then a gram of silver azide. I can't see how can it be reliable with conventional cap No8
configuration. May be it's like styphnate, only good for ammunition primers.
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Hennig Brand
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How much acetone peroxide did you you use to detonate your picric acid and at what diameter?
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Ral123
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May be no more then a gram if my feeling of volume and density is not mistaken me, but here's the test: http://www.youtube.com/watch?v=t5AUT48E7w4 As a matter of fact, the TNP I suspect is highly nitrated, as I used quite a lot of WFNA/H2SO4 and a
gram of primary ain't little.
Doesn't your designs have too much wall/bottom thickness, preventing good shock wave transfer? I love my azide-Tetryl straws.
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Hennig Brand
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Interesting video. The inside diameter of that charge looks to be at least 3/8" and maybe closer to 1/2"(I measured a similar lighter with vernier
callipers). I have been using 5/16" diameter aluminum tubing, which probably gives stronger confinement but less diameter. A little extra diameter
might make a big difference to how easily picric acid is initiated.
Those critical diameter specifications from the text books are best case scenario, with ultra pure picric acid. A little less purity or density
difference (or whatever) and the critical diameter could become significantly larger (I think).
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Ral123
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The diameter is exactly 9mm. And I like giving the primary some distance to develop it's velocity.
For the DDNP, may be the confinement factor is the only thing left. I suspect the arrow tube can still make good cap. Here's how I've sealed the
bottom by bending material inwards and hammering down some Al foil for extra seal: http://youtu.be/luj3NdyBisA?t=37s That way the bottom is both thin and strong. For the upper part: e-match, some inert/heavy/incomressible powder
and than epoxy. The gases won't have anywhere to go and may be most of the material will be detonated with high velocity.
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Hennig Brand
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The aluminum arrow is just a hair under 5/16" id (~7.6-7.8mm), which is significantly under 9mm. "Propellants and Explosives" By Naminosuke Kubota,
gives the critical diameter of picric acid as 6mm. I wonder if it's kind of like fat people losing weight. You know, the first ten pounds does much
more for their health than the ten pounds after that, and so on (so they say). If the critical diameter is 6mm for picric acid, going from 7.6mm to
9mm might make one hell of a difference.
I wonder how much impurity it would take in a picric acid sample to raise that critical diameter from 6mm to 7mm. I am guessing probably not that
much.
[Edited on 3-7-2014 by Polverone]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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Quote: Originally posted by Hennig Brand  | Interesting video. The inside diameter of that charge looks to be at least 3/8" and maybe closer to 1/2"(I measured a similar lighter with vernier
callipers). I have been using 5/16" diameter aluminum tubing, which probably gives stronger confinement but less diameter. A little extra diameter
might make a big difference to how easily picric acid is initiated.
Those critical diameter specifications from the text books are best case scenario, with ultra pure picric acid. A little less purity or density
difference (or whatever) and the critical diameter could become significantly larger (I think). |
It is virtually impossible for an individual to reproduce exactly the same scale of detonator as is made by professional ordnance manufacturers, using
special techniques and trade secrets that exploit economy to the fullest for a mass produced item. What can be done is to duplicate the general
principle in a less highly refined implementation where the general principle is reduced to practice.
AP can definitely detonate picric acid but it has to be a special configuration using generous amount of the AP used for the initiator. The
configuration described worked with the ball of putty used to hot start and compress in situ the firing train. Without the AP / Bullseye putty for
the top charge the device failed. But with that quarter gram as first fire, the device worked fine. The details are in the links here.
http://www.sciencemadness.org/talk/viewthread.php?tid=179&am...
http://www.sciencemadness.org/talk/viewthread.php?tid=179&am...
http://www.sciencemadness.org/talk/viewthread.php?tid=179&am...
Most interesting among the AP variants would be the terameric AP
http://www.sciencemadness.org/talk/viewthread.php?tid=179&am...
My thoughts about isolation and purification of AP would be beneficial due to the inclusion of water in AP as crystallized from aqueous reaction
mixtures, so it would probably be a good scheme to dissolve the AP in hot toluene and decant from any crystal water which settles out or easier pipet
the water globule away, and precipitate anhydrous AP with methanol added to the hot toluene.
Likewise for AP is the DDT operating principle applicable for HMTD and DDNP which have in common with AP the same lack of unequivocality, slow self
accelleration and a larger than ideal critical diameter, particularly true and more evident for an improvised configuration no matter how refined it
may be thought by the improviser that such configuration is. An improvised detonator is still unsophisticated and crude compared to the detonators
made by professional ordnance manufacturers, who simply don't publish all the details of everything done. Almost nothing about the initiating
quantities reported in the literature will ever translate directly to what is found to be the case by direct esperimentation to confirm. The general
principles will hold true but your numbers won't be close to their numbers for a working device, a multiplier will apply.
If you get similar performance at 150% as a minimum of what is reported, then count that as excellent. 200% or even more would be the more common
result as a materials demand for an improvided device.
Not mentioned very often is the fact styphnic acid is almost an equally good base charge as is picric acid and styphnic acid is more sensitive to
initiation than is picric acid requiring perhaps 20% less impulse to initiate.
[Edited on 4-2-2014 by Rosco Bodine]
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Hennig Brand
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It's not that I ever disagreed with you on this, but let’s just say I agree with you a lot more than ever. Trying to replicate those published
numbers is cruel and unusual punishment and will just result in unreliable blasting caps. I know this has been discussed to death, but things often
take a while to sink in (at least for me).
That work you did, detonating picric acid with acetone peroxide, is interesting and telling. Do you remember 4 or 5 years ago when I posted about
trying to detonate picric acid with acetone peroxide? By the end of it I had a full gram of AP pressed really hard in a vise, on top of 1.5 or 2g of
picric acid, in a 3/8" aluminum tube. I was watching from behind cover and what I saw when the acetone peroxide detonated was a big yellow cloud of
vaporized picric acid.
I have been sort of off and on questioning how pure my picric acid is for the last few years. It really is just insensitive stuff, especially if
conditions aren't just right.
[Edited on 4-2-2014 by Hennig Brand]
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Rosco Bodine
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BTW a reenforcing cap is generally a short length to diameter like 1:1 and is domed like freeze plug for an engine block, flattening the dome and
pressure laterally inside the skirt expands the diameter and locks the inverted cup in place. Not all of the initiator is necessarily confined within
the reenforcing cap but maybe only the first fire or small increment of the initiator, which may have full bore diameter in its main increment length
atop the base charge.
DDNP of smaller mesh mixed 70/30 with KClO3 or KClO4 and then utilized in greater quantity not strongly pressed would likely be an improvement. A
loose flash charge of basic lead picrate in sufficient amount to low order detonate on ignition, like a quarter to a third of a gram, would give a hot
start and in situ compression, to the chlorate sensitized mixture which should then high order more easily.
[Edited on 4-2-2014 by Rosco Bodine]
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Hennig Brand
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Thanks, yeah the old document I was using as a reference had pretty sparse details regarding reenforcing detonators. I had to read it 3 or 4 times to
even figure out what I did.
What I could do with the reenforcing caps I have is to press one or more locking, domed discs in on top of them. These discs would need to have center
holes drilled in them before loading. I guess making the reenforcing caps a little shorter might be in order too, since I made them to hold the whole
primary charge.
Good ideas, regarding mesh size reduction and (per)chlorate admixture. I have been heading towards smaller mesh size lately actually. The agitated
evaporative recrystallization method could easily produce any mesh size you wanted with a little fine tuning.
[Edited on 4-2-2014 by Hennig Brand]
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Ral123
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What did you have above the AP, maybe a little putty and then epoxy would give good confinement. Also, maybe two grams would've developed higher
pressure and velocity at the TNP. In my test I had most of the TNP hammered with a bolt, but some was hand pressed like the AP.
In the suggestion of the arrow tube, I had in mind pure DDNP or DDNP>2g and the rest is crystaline secondary. As for the critical diameter, in a
test, the TNP detonated all the way in a straw, so in the confinement of the arrow tube it's sure to do well, at the right density.
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Rosco Bodine
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| Quote: Originally posted by Hennig Brand | | It's not that I ever disagreed with you on this, but let’s just say I agree with you a lot more than ever. Trying to replicate those published
numbers is cruel and unusual punishment and will just result in unreliable blasting caps. I know this has been discussed to death, but things often
take a while to sink in (at least for me). |
The context of laboratory tests done under rigid conditions for a particular sample is important to be understood applies only with specificity to
that sample and to that series of tests, and there are variables that will cause your own tests of a different sample under conditions that are not
identical to be different. If the context is not given as much consideration as it should be then it can easily lead to faulty analysis and faulty
conclusions about your own test results which should only be expected to generally follow a trend identified by other researchers, and not necessarily
show identical results. Only the general principle should be expected to hold true, not exact verbatim duplication like a carbon copy of what was
reported by others. Criticality is the factor involved when when certain tests done by others are not being reported with emphasis that their work is
being done with optimization of every parameter with an object of economy of materials as would interest investors in some patented process which is
being marketed. So an inventors euphoria and salesmanship may cause glorification to be applied to reported results bordering on making false
representation. Understanding that is a motivation for the content of published literature because of the nature of the scenario involved, should
cause some skepticism and cynicism to apply while reading the reports with a certain reservation until verifying what is reported and understanding
the context more completely.
| Quote: |
That work you did, detonating picric acid with acetone peroxide, is interesting and telling. Do you remember 4 or 5 years ago when I posted about
trying to detonate picric acid with acetone peroxide? By the end of it I had a full gram of AP pressed really hard in a vise, on top of 1.5 or 2g of
picric acid, in a 3/8" aluminum tube. I was watching from behind cover and what I saw when the acetone peroxide detonated was a big yellow cloud of
vaporized picric acid. |
I didn't follow your experiments. But obviously a "full gram" of AP thought to be "enough" is a faulty premise, and could lead to faulty conclusions
which is illustrative of the issue. Working up a loading is a practical matter that follows a certain course. When you have only half what is required
to do the job then there is no getting past doubling what you incorrectly presumed would be enough, understanding the presumption was incorrect. A
premise that is faulty will skew the analysis and conclusions every time.
| Quote: |
I have been sort of off and on questioning how pure my picric acid is for the last few years. It really is just insensitive stuff, especially if
conditions aren't just right. |
It is likely that your picric acid is fine. It is also likely that you have some faulty understandings about its properties in response to various
schemes for its reliable initiation which cause you to believe it is easier to detonate than it actually is. The literature which exaggerates and
falsely represents that picric acid is more sensitive than it actually is has skewed your expectation so that you somehow expect that picric acid
should be easier to detonate than it is. Picric acid is quite insensitive to initiation and has to be subjected to a pretty extreme provocation to
cause its detonation. If you have problems getting picric acid to detonate then the issue is very simple, and that is that you haven't gotten extreme
enough yet in the delivery of an initiating impulse to the target material to provoke its detonation. Because when that threshhold is crossed then the
picric acid or any other energetic material capable of detonation, will in fact be detonated, not by anybody's expectation of what the material should
do but simply because of the laws of physics.
You are understanding that crystal mesh and form is important, but then have unreasonably focused upon a scheme of "solvent evaporation" as some sort
of special technique presumed to be somehow advantageous when that premise has no basis other than what is your expectation. It may be that you are
operating on a faulty premise and that other factors are more important.
Read the linked post with its references
http://www.sciencemadness.org/talk/viewthread.php?tid=389&am...
and this also
http://www.sciencemadness.org/talk/viewthread.php?tid=22810&...
I would again reiterate what I have said before that you can do any materials testing for proof of concept using a polypropylene test tube. It
doesn't require elaborate equipment but some basic fixtures and dies and shields for safety concerns. Tool and die shop prototyping is another level
and then mass production is yet another. Basically it is no more difficult to handload ammunition or detonators but for the availability of raw
materials that are the components and having the knowledge gotten from materials testing to assemble the components needed to do the job. Looking for
any 1-2-3 ABC "you tube" tutorial on detonator manufacture is a way to go for some folks but I'm not going there. Good information about detonators
is a hundred plus years old technology that is ubiquitous and those people who would need every minute detail spoon fed to them likely don't have the
wits to be trusted with doing anything constructive with the information. If detonator technology is left mysterious for some people then that is
probably an inherent safeguard that is prudent like not letting children play with matches.
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Hennig Brand
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Thanks for the good links; they have cleared up a few things for me. For one thing, DDNP does have its virtues which are now more clear. I am
definitely going to try the 75-25 DDNP-Potassium Chlorate mixture.
| Quote: Originally posted by Rosco Bodine |
You are understanding that crystal mesh and form is important, but then have unreasonably focused upon a scheme of "solvent evaporation" as some sort
of special technique presumed to be somehow advantageous when that premise has no basis other than what is your expectation. It may be that you are
operating on a faulty premise and that other factors are more important.
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The reason I have been focused on the solvent evaporation method is because I haven't seen anything disclosed in the literature about recrystallizing
DDNP, except for the purification technique involving dumping ice cold water into a DDNP solution in acetone. That process works for purification but
not crystal size control. In the absence of any technique, I read about recrystallization and picked a method that seemed appropriate. It seems to be
very easy to control, though it can be a bit time consuming. Vapor pressure of the solvent is controlled by temperature and the rate of vapor release
can also be controlled by the amount the evaporating vessel is sealed. Agitation can be varied also, which I have found is very important.
Having no basis is not really accurate. I did review some of the common solvents and attempted to work out some sort of normal slow cooling method,
but found most of the common solvents were not really appropriate. Also the evaporative recrystallization technique was studied a bit by me
(admittedly briefly) and the techniques and advantages and disadvantages are well documented and tested by others.
The solvent evaporation method is a bit of a novelty for me, because I hadn't heard of it being done with DDNP. If you have a better solution (pun
intended), that you know works, let me know.
| Quote: Originally posted by Rosco Bodine |
I would again reiterate what I have said before that you can do any materials testing for proof of concept using a polypropylene test tube. It doesn't
require elaborate equipment but some basic fixtures and dies and shields for safety concerns. Tool and die shop prototyping is another level and then
mass production is yet another. Basically it is no more difficult to handload ammunition or detonators but for the availability of raw materials that
are the components and having the knowledge gotten from materials testing to assemble the components needed to do the job. Looking for any 1-2-3 ABC
"you tube" tutorial on detonator manufacture is a way to go for some folks but I'm not going there. Good information about detonators is a hundred
plus years old technology that is ubiquitous and those people who would need every minute detail spoon fed to them likely don't have the wits to be
trusted with doing anything constructive with the information. If detonator technology is left mysterious for some people then that is probably an
inherent safeguard that is prudent like not letting children play with matches. |
I hope you’re not talking about me. I am not always the quickest to catch on, but I play with picric acid mostly just as a challenge. If it was
really just about practicality I would just stick with PETN base charges. I have known for a long time that if I increased the charge diameter that
picric acid would shoot much more easily. I resisted making really large diameter caps because I felt that they were not that practical and was hoping
that I would be able to make it work properly in smaller diameters, which I guess was unrealistic. Picric acid seems to be much better suited as a
booster or main charge than a component of a compound cap. It can be made to work, I am not denying that.
[Edited on 4-2-2014 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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What I meant by saying there is no basis for your expectation involving solvent evaporation as a crystallization method is specific to DDNP and not as
a general rule for recrystallizations. It introduces an unknown that is not described in the literature related to modifying the crystal form or mesh
of the DDNP. So you end up with a product that is unique to your process since it is not a manipulation described by others. It may coincide with the
work others have done and it may not. You can't do anyhting different from what is reported and then fairly compare what is your result doing
differently what others may have done a different way. Crystallization varies widely and this involves a property that definitely can have bearing on
the behavior of an energetic material. It is a physical parameter like progressive pressure loading that has at one end of a column a certain density
gotten by high compression reduced incrementally to a loose powder in the first fire ignition zone. That scenario might DDT high order every time,
while one uniformly compressed column of the identical material may only burn like a rocket fuel grain and never even low order. And a change in the
mesh size or crystallization method could have the effect that both go or both no go, or no change whatever. It is an unknown that is a variable
being introduced.
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Hennig Brand
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You could have a point there, I don't know. The DDNP solution is constantly pushed ever so slowly into oversaturation, growing the crystals in the
process. Evaporation seems different but really what is happening is very similar to a slow cooling or a slow addition, just different ways of
manipulating the concentration or in the case of slow cooling the solvents ability to dissolve the solute. I am really just a hobby chemist, but I was
under the impression that the crystals formed were usually more of a property of the molecule being crystallized. I know there are examples of the
same chemical crystallizing in different ways depending on solvent used, etc, but as a general rule the type of crystals formed has to do with the
type of molecule being crystallized (I think).
BTW, congratulations on reaching 5000 posts. Holy Smokes! You have made a lot of good contributions. Keep up the good work.
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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Something you have to consider when critical diameter is involved is it will be limiting as a minimum what is the larger critical diameter of any
component.
For example at a critical diameter of 6 mm for picric acid and a critical diameter of 8 mm for some primary or perhaps 9 or 10 mm for another primary,
the larger value would govern the ID for a cylindrical capsule unless it was stepped in diameter by a bushing of some kind used to couple the
increments. You can get picric acid to detonate at 1/4" column diameter but it requires an initiator like lead azide that will also develop the
needed impulse with regards to that diameter which won't quench the initiator. It wouldn't work with AP instead of lead azide at the smaller diameter.
It can easily happen that the geometry of what amounts to being a ribbon charge of the initiator, is what is needed for the portion of the column of
initiating explosive remaining after most of the column height of initiator has already deflagrated and/or low ordered in the run up as kindling for
the fire that will be the high order impulse of the remaining portion of the pellet that then operates high order as a ribbon charge. The increase in
charge weights for an increasing scale device to operate tend to follow a geometric increase meaning if you double the diameter it takes four times
the amount but less some of what is gained by the faster run up of a larger diameter charge. It generally won't reduce to a mathematical doubling of
the charge to get twice the output from a detonator scale device at the same diameter nor will it square for the doubled diameter but will fall
somewhere in the middle of that range. At near to the critical diameter every detail becomes more critical to be exactly correct. Getting
comfortably larger than the critical diameter it is easier to design a configuration having highest reliability, but at the expense of economy of
materials.
[Edited on 4-2-2014 by Rosco Bodine]
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Hennig Brand
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Makes a lot of sense. Yeah, cross sectional area is proportional to the square of the diameter. Doubling the diameter yields 4 times the cross
sectional area, which also yields four times the volume of explosive for a given height. I am definitely going for 3/8" or 9mm id for my next test.
Most of the time there really is no issue with having caps a little bit jumbo. I like the little ones with PETN in them for plastic explosives,
especially when using small charges, but for normal blasting there is really little problem with the bigger ones. What I really like about DDNP is
that it is made from picric acid and a few other very basic reactants. Basic lead picrate is also made from picric acid. Strong blasting caps made
from aspirin, gotta love it!
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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Yes the versatility of picric acid considering its useful derivatives and its easy source materials puts it in a unique role which makes it explosives
101.
For the initiator of a small diameter column of explosive as is the base charge of a detonator, confined at near to what would be its critical
diameter, it has been my observation and resulting theory as follows:
For an initiator, the function is similar as the concept of a platter charge, where the effect of a ribbon charge is observed, which obeys shaped
charge scaling rules similar to a shallow angle cone platter charge geometry approaching or configured as a flat disk. There is an optimum geometry
of diameter to thickness of the disk that is the increment of initiator undergoing high order detonation which favors a directed concentration of the
output wave perpendicular to the surface of that disk and parallel to the axis of the disk. Of course the axially directed effect is augmented by
confinement similar to a gun barrel, but there is a fundamental directivity of the shock wave that is focused axially by the geometry of the initiator
alone, even if there is no confinement for the initiator.
http://en.wikipedia.org/wiki/Misznay%E2%80%93Schardin_effect
How far up in scale away from the critical diameter the effect may hold true that geometry is an important factor I am not sure, and the geometry that
is optimum probably varies for different explosives.
It is a reasonable conclusion that follows that for a given initiator and base charge pair there will exist a practical minimum diameter which governs
the lower limit for economy of materials involved in coupling the output of the initiator to the base charge to produce a reliable device that
operates comfortably within design limits, not subject to failure for being adversely affected by small variables inherent to the system or any of its
components.
[Edited on 5-2-2014 by Rosco Bodine]
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Ral123
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If my TNP detonates in 5-6mm straw, then I can't see problem at 9+mm and metal confinement. I suppose nice "old school" cap can be made with 1cm
copper tube, 2g DDNP and 2g+TNP. But I can't trust that primary anymore :/ There are cigar tubes that are like 1,5cm+ diameter and have fine thin
walls from stainless steel or aluminium. I guess they can make a good TNP booster. May be they can have a removable thick walled DDNP element in them
also.
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Hennig Brand
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I wouldn't trust a picric acid cap to function reliably at 5-6mm id with any primary. The tolerances would be tiny. You’re talking about being below
the critical diameter and very weak confinement. Having at least 2 or 3 millimetres over the critical diameter provides reliability. Not suggesting
that picric acid at 6mm can't detonate, just that except for some sort of test it doesn't make sense to make caps that way.
@Rosco
I just read through the patent regarding the blasting caps with the cavity or shaped charge effects. Very good idea and they could be easily made. A
loading dowel with a cone shaped tip could be made to press the picric acid. A reinforcing cap over top of the primary and you would be in business.
The amount of secondary in direct contact with the primary is also much more with this design.
[Edited on 5-2-2014 by Hennig Brand]
"A risk-free world is a very dull world, one from which we are apt to learn little of consequence." -Geerat Vermeij
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Rosco Bodine
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When working up a load for a detonator using various components it requires systematic testing of performance that is identical in many ways to
working up a load for ammunition. Theory only puts you in the ball park for where testing begins and then the charting of weights and results follows
typical experimental approach.
As the load approaches critical diameter every parameter becomes more critical and works against reliability. For a carefully made metallic cap a
1/4" ID which is 6.35 mm is comfortably above the critical diameter for picric acid or styphnic acid, particularly if the initiator is lead azide and
there is a bit excess used to assure reliability.
Generally what would occur for initial testing would be a greater amount initiator than is needed to assure detonation would be used and then the
amount would be reduced incrementally until a failure occurs, and then the amount incrementally increased again to find the point of minimum where
about 5 of 5 fire successfully and then that loading will be mulitplied by 150% t0 200% to be a standard loading acceptable designated minimum.
Whether the device is being tasked or not in a "mission critical" role would have bearing on the amount of headroom that is built into the device and
what is the degradation of components allowable before failure becomes likely.
There are different design criteria for a detonator to be used for general blasting utility uses and a detonator to be used for warhead activation in
an expensive weapons system.
A farmer blasting a stump or a boulder wants a blasting cap that is cheap and if 1 of 500 detonators doesn't work correctly as the predicted failure
rate, it isn't a situation causing much safety concern or poor economy for waste. However, for the different case where ordnance is needing a
detonator which may be the least expensive component in what may even be a million dollar cost weapon, there is a desire and an economics that is very
different and a different standard of guaranteed reliability changes what are the acceptable design limits which must be applied regardless of the
cost or scale of the detonator where different requirements than economy govern.
The economics which may govern the manufacture of detonators used in land mines or cluster bombs will incline towards keeping it cheap for mass
production even if perfect reliability is not guaranteed. But the detonator used in a naval torpedo or a guided missile will likely be the Cadillac
of detonators and there will be more than one for redundancy.
So the sophistication and complexity of the detonator is something that can cover a broad range from minimal and cheap to elaborate and advanced and
expensive, depending upon the application requirement. Detonator design covers the range of materials science and tooling requirements from basic to
elegant depending upon what is the intended purpose. There definitely will exist what may be identified as "ideal configurations" for various
purposes. Some of those configurations may be published and patented but it would be no surprise that many or most such configurations are trade or
state secrets and are not published anywhere.
[Edited on 5-2-2014 by Rosco Bodine]
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Rosco Bodine
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| Quote: Originally posted by Hennig Brand | | I wouldn't trust a picric acid cap to function reliably at 5-6mm id with any primary. The tolerances would be tiny. You’re talking about being below
the critical diameter and very weak confinement. Having at least 2 or 3 millimetres over the critical diameter provides reliability. Not suggesting
that picric acid at 6mm can't detonate, just that except for some sort of test it doesn't make sense to make caps that way. |
It actually doesn't have to go that far over the critical diameter to get relief from the precision required, Fractional millimeter changes are enough
to see real changes occur involving the criticality of a configuration. Small geometry changes can have profound effect. Likewise for other
parameters. Don't overcompensate when seeing effects that are defined by precision. You can go wide with overcorrection to compensate for small
variations when it isn't necessary to solve a design or configuration problem.
| Quote: |
@Rosco
I just read through the patent regarding the blasting caps with the cavity or shaped charge effects. Very good idea and they could be easily made. A
loading dowel with a cone shaped tip could be made to press the picric acid. A reinforcing cap over top of the primary and you would be in business.
The amount of secondary in direct contact with the primary is also much more with this design. |
Actually it is more work than necessary and it introduces additional design issues to try to use shaped charge effects. The deformation pressures
laterally from a wedge used as a ram complicate capsule and die requirements and it just isn't necessary. The patent simply shows a general concept
and it may even be inverted to what is actually occurring for an enhanced initiator, backwards to what is needed for the actual geometry applicable to
the concept. I wouldn't go there to try to solve the problem of geometry which I described involving the platter charge or ribbon charge behavior of
the initiator, attempting to make it jet like a shaped charge, but simply to be aware the effect is there which can affect loading and the geometry of
the disk that is the compressed initiator portion of the firing train. A low order detonating flash charge as first fire almost serves the same
purpose as a reenforcing cap and it compresses in situ the elements of the column when that flash charge detonates it is also doing the work of
physically compressing the increments below that flash charge along with providing ignition, and may even cause sympathetic detonation of the
initiator from the pure compression ahead of the ignition. You have a virtual reenforcing cap that is a shock wave and a wall of fire and pressurized
gases being provided by the flash charge.
[Edited on 5-2-2014 by Rosco Bodine]
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