Sciencemadness Discussion Board

Unconventional Shaped Charges

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Axt - 24-10-2005 at 18:57

I choose to forget about using steel, not worth the risk and PVC obviously works even if performance is somewhat reduced.

Easiest way to fit the liner is to use a liner that will slide into the pipe, then fix it with a smaller diametre pipe as shown below. In this case a 4" PVC fitting is used as confinement and a small section of 4" pipe glued into the fitting hods the liner in place.

Alternatively leave the top of the charge open, with sufficient head height and fix the standoff to the liner. This stops the liner from being pushed out the bottom.

The only charge here that failed to penetrate was the "tulip" charge on the first page, in this case the liner wasn't secured firmly, rather glued into the end of 3" pipe without any support.

<center><img src="http://ww1.webtop100.net/~52497/rogue.webtop100.net/images/shapedfront.jpg"></center>

This particular one was <a href="http://ww1.webtop100.net/~52497/rogue.webtop100.net/images/shaped.jpg">setup</a> but failed to detonate.

[Edited on 25-10-2005 by Axt]

glass liners

nitro-genes - 26-10-2005 at 07:02

I'm confused why glass works so well as a liner, since on sudden force it behaves as a very brittle material. Though there is some discussion about glass being a solid or a supercooled liquid, the myth of slowly downwards flowing window glass doesn't seem to be true.
Modern soda/lime glass has a transition temperature ranging from 270-550 deg C. Which means above these temperatures it behaves as a liquid. These temperatures are easily reached for copper liners. This could also be the case for glass if the high temperature of a jet is mainly formed because of internal friction in the liner when it collapses. (Is this true?) I can't imagine that there is a large conduction of heat from the explosive to the liner material in those few microseconds...
I'm convinced however the glass liner doesn't form a jet of glass powder because in a test with a 3 cm glass cone I found the glass to have formed a thin deposit layer on the inside of the perforation hole. It appeared as a shiny light blue plastic like layer. Has someone else noticed this?
Anyway, the jet didn't travel through the entire 5 cm of steel, but 4,7 cm instead. Although the jet penetrated almost the entire block, there was not even a slight bumb on the other side of the block! Incredible to see that there is indeed only sideway displacement of the steel around the jet.
This time i used a 85% PETN platique as I found that NM plastique isn't detonable with these diameters, or has a very poor performance instead. (i used 37 mm steel hemispheres with a 50mm PVC tube earlier) So I really expected a full penetration this time.
I am wondering if the standoff might be to blame, as I used 2 times standoff as usual. Could it be that a because of the brittle nature of glass the jet is less coherent? The M2A4 demolition charge also uses a 60 degrees glass cone, but is used with only a 1,2 times cone diameter standoff...

Microtek - 27-10-2005 at 13:03

In some advanced shaped charges, the liner is composed of a powdered metal such as tungsten which is pressed into the desired shape. When the glass is shocked, it probably shatters into a fine powder similar to the pressed metal.
Since this presumably works well ( or they'd just use cheap copper instead ), it might be worth considering if copper powder could be bound with something ( plaster of paris or perhaps a suitable polymer ) if copper cones were difficult to come by.

Axt - 27-10-2005 at 21:18

I cant remember the name of the process so I cant give references, but some exotic alloys are formed by explosive compression of metal powders, when normal processes cant be used. This is a solid homogeneous alloy, not a compressed powder.

I'm willing to bet this is also what happens to glass, rather then a "powder stream" the pressure involved squeeze it into a cohearent solid. Glass being lighter then the metal will be accellerated faster, in part compensating for its lower density.

Another advantage of using glass, and possibly the reason it is used commercially is that thee will be no "carrot" formed as at those presures and velocity it will just shatter. Thus there will be no obstructions left in the hole.

chemistr1 - 28-10-2005 at 12:45

I have been designing aluminium cold cast cones but with limited results as I have been using ANxxx secondaries.
Now that I have some erythritol maybe it is time to restart the research.
With 75% Al 25% resin cold cast cones. If this works satisfactorily then 75% copper 25% resin would be the next logical step or maybe a mix of metal powders.

Not wanting to start a new thread but how high a yield have people had with ETN as I have around 100gm yield for a 45gm/180gm/300ml E/AN/H2SO4 batch.
Its still drying, is perfectly neutralised and white but the yield just seem very high although I know that it is in the theoretical range.
Was I just lucky or has something gone wrong?

[Edited on 28-10-05 by chemistr1]

Chris The Great - 28-10-2005 at 14:16

Very interesting idea with metal powder/resin! I am inclined to try it, as I tried making a cone before and had a very hard time. Does any particular resin work better? I think I will try my 5-minute epoxy since I happen to have it lying around. It would appear to be a very easy and (hopefully, have you tried yet) effective method of making good cone liners. Although it should also work well for trumpet cones and other exotic shapes.

As for the ETN yield, check some threads about it, everyone seems to get huge yields from what I've read. Since it has a low melting point (?) I think it would work well in a shaped charge as it could be melted with hot water and cast.

Axt - 28-10-2005 at 20:52

Take ETN discussion not related to shaped charges here http://www.sciencemadness.org/talk/viewthread.php?tid=1100

Cast ETN failed in the bullet jacket SC's, exploding with a vvvvvppBANG, very little penetration. Though it will probably perform better it larger quantities.

Boomer - 11-11-2005 at 07:48

Axt wrote: "Also with thick containment the liner should be held as firm as the body, no point constructing a SC out of 5mm steel pipe and then sticky taping the liner in."

Could you please elaborate on this? While I *did* experience that a thick-walled metal pipe gives better penetration than a cardboard pipe, I thought it was from higher VoD with confinement, especially with a dense, nearly void-free plastique that needs confinement at low diameters. I do not understand the reason for having to firmly hold the liner:

IIRC the pressure on the liner is much higher than its tensile strength, and the VoD is higher than the speed of sound in copper. How can the lower rim of the liner 'know' that it should dislodge from the casing and spoil jet formation, when the collapsing upper part of it is overtaking the sound wave in the liner which would 'tell' the rim that something is happening upstairs? Hope that is clear, what I mean is the forming liner will overtake the rim (folding over) before it can dislodge. Am I mistaken here? If yes why?

Axt - 11-11-2005 at 09:35

I cant say with certainty, and can provide no direct references to liner "security", but my thoughts and experiances follow;

The liner which ideally is acting as in incompressible liquid (though nothings ideal) will "know" its been hit. Pretend you have a long incompressible rod, hit one end and the end will move before you hear it. The cone shaped liner won't collapse in on itself perfectly and is "pushed" along the axis of its walls if not secured.

I have read your posts on SC's, from memory your ("laminated" I guess your could say) liners are quite thin correct? easily collapsed thus liner "security" is less of an issue with liner collapse, but more important for explosive VOD in this case (HDN).

The steel liner I used and the stronger "tulip" shape failed miserably where the liner wasnt secured, yet whenever the standoff held up the liner (the glass liner) or the liner sits directly on the target itself (cylindrical/linear/bjsc) the holes have been very concentric circles with no spray at all.

The posts on body confinement above are mainly restating, and adding lost context to the fundamentals of shaped charges extract. Which unequivocally states that heavy confinement aids to keep detonation pressures high during liner collapse (thus doing more then just ensuring high VOD).

Boomer - 14-11-2005 at 00:25

"Pretend you have a long incompressible rod, hit one end and the end will move before you hear it"

I get your point, and a have no reference either. But my 'gut feeling' (read limited understanding of thermo/hydrodynamics - my nick is not cheetah :P ) tells me there is a fault in this reasoning: Firstly, you rod example would suggest the whole mass moving *before* the shock reaches the other end. That cant be. Secondly, this wave (shock or sound) *is* a compression wave. Though compression factor is usually small, since e-module is big. Thirdly, while (nearly) incompressible, metals *are* compressed considerably by HE shock waves. IIRC the Pu in a non-gun-type nuke is compressed 2-3 times, going from 20 to 40-60 g/ccm !!! This is in addition to collapsing the hollow sphere. (Fat Man had a massive pit, not relying in collapsing a cavity at all.)

Apart from this, just for fun I calculated the acceleration of the liner material. It cannot be instantaneous, since this would require infinite pressure: Assuming linear acceleration over 5mm from zero to 8 km/s, you get 640 million g acting for 1.25 µs.
To back this up, I chose one square cm of 0.8mm thickness, weighing roughly 0.65g. If hit by 400 kbar, this will accelerate with a = 4 million N / 0.0065 kg = 615 million g for 1.3µs. Close enough!

Now please tell me, what is happening to the metal in that microsecond? Is it being compressed while speeding up? Is the det wave slowed down at first, speeding up again with the metal? As I said above it cannot go to full jet speed instantaneously. I whish I were cheetah.... :(

Edit: It was not too much HDN, mostly NG, MHN, RDX, so quite fast at 1.65 g/ccm I bet.

[Edited on 14-11-2005 by Boomer]

Rosco Bodine - 14-11-2005 at 06:12

There has been an idea which I have never tried for a PETN melt cast composition that may be useful for
shaped charges and should have about
10 % ( or more ) brisance than C4 or SEMTEX :D

The constituents would need to be very pure acid free and and stabilized , perhaps with urea / dicyandiamide / betaine via the entrapped trace stabilizer
method applied during the recrystallization of each of the nitroester
constituents for the eutectic .

The composition would predominately consist of the 80/20 PETN / MHN eutectic which melts at 101.3 C . It seems likely that the m.p. of the eutectic could be lowered further by addition of yet a third
nitrated polyol , ETN or perhaps Inositol Hexanitrate or one of the other nitrated polyols . The possible use of RDX as a filler of suspended solid particles,
using such a melt as an energetic binder
is also contemplated if the RDX is found to
be compatable with the melt .

The output of such a melt cast should be very high energy and velocity , and not difficult to initiate .

Axt - 14-11-2005 at 08:40

But it stands to reason that the transference of detonation pressure into the liner will be greatest if its firmly held. Same as if a coin will be pancaked if placed between an explosive and steel plate but flung largely unharmed into the air if placed on top. I guess it comes down to a matter of significance, I think its going to be just as significant as strong confinement regarding transfer of detonaton pressure when it comes to strong rigid liners.

"<i>Allison and Vitali (1963) and Harlow and Pracht (1966) indicated that the effect of compressibility on penetration of metal jets into metal targets is slight.</i>" FOSC.

Not entirely within context, but I'll concede that slight compression doesn't necessarily mean insignificant.

Quote:
Originally posted by Microtek
it might be worth considering if copper powder could be bound with something ( plaster of paris or perhaps a suitable polymer ) if copper cones were difficult to come by.


A mixture of latex and copper powder (~50:50 by volume) was made and an aluminium cone (alternatively, use a plumb bob) was dipped into it. Once a skin formed on the surface it was dipped again, and repeated again. Latex was used since it is sticky when wet but not once dry so can easily be removed off the cone.

The copper mixture was more viscous then straight latex and held a thicker layer easier, but when I left it upside down to dry it drooped a bit resulting in the outside forming a tulip shape, but its proof of concept. The dried latex/Cu is quite strong and elastic.

<center><img src="http://www.sciencemadness.org/scipics/axt/latex-liners.jpg"></center>

[Edited on 14-11-2005 by Axt]

Cylindrical charge?

lacrima97 - 15-11-2005 at 18:49

I looked at the picture from the very first post and I don't see the inverted cone part, but a narrow tube. Is this tube used instead of the cone?

Axt - 16-11-2005 at 02:52

Quote:
Originally posted by lacrimachemist
Is this tube used instead of the cone?


Yes, through the combination of title, picture and quote that really should have been obvious :/

lacrima97 - 16-11-2005 at 11:40

Oh, I'm sorry Axt, I have never seen a shaped charge that looks like that, but nice job on the charge btw.

Axt - 18-11-2005 at 23:20

Quote:
Originally posted by Axt
A mixture of latex and copper powder (~50:50 by volume)


I have to go back on that, It was a guess as I was just adding copper while mixing it in. I tried weighing while mixing some today and there is no way you can get 50:50 by volume and keep it runny enough to dip. Also, copper reacted with my latex due to its ammonia content, its OK if used immediately but cannot be stored.

Anyway, you can dilute liquid latex with water, and nickel powder can be substituted for copper (Probably still reacts slowly, but Ni is a better material for SC liners anyway). The following worked for me.

90g 5 micron nickel powder
35g Liquid latex
20ml Water

Ratio is probably the same for copper due to simular densities, though not all liquid latex is the same, simply add water until a viscosity simular to glycerine.

Place them into a small container and give it a shake, this will give ~80% Ni by weight once dry. Problem is, it no longer comes off the cone easily. Solution is to first use a coat of pure latex, dry it and remove it, slide it back on and dip that into the Ni/Latex emulsion.

Alternatively, since you now have the latex sleeve, you could add any binder to the metal powder and dip that since the problem of removing the liner from the cone is no longer an issue.

chemoleo - 19-11-2005 at 11:42

In casting (for art purposes) Cu, Al or Bronze powder is often mixed into clear casting resin, to give a thick paste that is identical in strength, very heavy and can be polished to a metallic sheen.
Trust me, I tried it. The resin can be made so saturated with Cu that it is hard to tell it apart from real copper, by weight and touch (it even feels cold).
Something you may want to try. You'd need an outer and inner mold for the cone however, you'd really want to do it properly. You *will* be impressed by the strength and metal-likeness of the resulting material, however.

Axt - 11-12-2005 at 17:34

Heres some of the same .45 colt/.357 mag shaped charges as shown on page 3. This time into 6 3mm plates. Also the plates were clamped and a .45 was fired into the side.

<center><img src="http://www.sciencemadness.org/scipics/axt/45-357-hole.jpg">

<img src="http://www.sciencemadness.org/scipics/axt/45-357-plates.jpg">

<img src="http://www.sciencemadness.org/scipics/axt/45-peno.jpg"></center>

MephistosMinion - 15-12-2005 at 04:55

Very nice Axt.

Hypothetically, if someone was pissed off at the cost of plasma cutting, and somone wanted to cut 25mm mild steel plate, would a linear charge similar to the one posted on page one be adequite for the job using pressed ETN?

Hypothetically of course.

Fulmen - 15-12-2005 at 10:17

Personally I feel that any time a problem that can be solved (or at least complicated in an amusing way) with high explosives it should be used.

Plasma torch? We don't need no stinkin plasma torch!
*BOOOOOM*

Duster - 15-12-2005 at 11:03

Theres more than one way to cut down a tree eh?

Chris The Great - 16-12-2005 at 01:49

I think that it would work very well for cutting your hypothetical metal very well. Axt managed to do a VERY nice striaght cut with his linear shaped charge, I doubt you would have any trouble.

Guys, although I agree (HE makes things alot easier, quicker, more enjoyable etc) it is getting pretty off topic. Unless you're cutting down trees with linear shaped charges :D

Hypothetically of course.


Have you tested the latex bonded cone Axt? Or are you going to try again and make a better one before testing how well it works?
Nice pics btw. I fired a shaped charge recently but it just splattered a bit of the liner on the target, making lots of microscopic, round craters on the metal (looks cool under microscope) but penetrating only 2mm in one spot. No jet formed at all. I wasn't really surprised, it was made with 15g of excess AP from a higher than expected yield, and I don't think I gave the detonation enough space to build up before it hit the 60 degree poorly made cone (it was my first try :P )

PHILOU Zrealone - 16-12-2005 at 14:22

Quote:
Originally posted by Axt

NM/HNO3 Is a very brisant explosive in its own right, and the intimate contact between these liquids is better then NM/AN for example. Ammonium sulphate will happily explode as well, and acts to hold it into a solid structure.

Though im not sure about the safety of this mix, pure NM mixed with pure HNO3 is very sensitive. Theres many dilutants in this mix however NH4NO3/NH4HSO4/H2SO4/HNO3/NH4CH2NO2 probably more... I'll try shooting it to get some measure of its safety.

[Edited on 7-6-2005 by chemoleo]

Axt,
I believe you must be a noctambule almost not sleeping :o unless you are jobless and single :P... regarding the amount of good experiments you have done and the impressive amount of data you gathered here in so little time. RESPECT!

Back to the black sheep... I like the mix you invented!
NH4NO3 + NM + H2SO4

First of all allow me to make a tiny correction NH4O-NO=CH2 can't be a potential dillutant in the mix for the simple reason media is fairly acidic.

It is interesting in many aspects although stability is a bit complex to evaluate owing to the incredible amount of sensitisers that will arise from that a priori simple mix.

As you said HNO3 and NH4HSO4 aside from (NH4)2SO4...but also HO-NH2 hydroxylamine (as hydroxylamine sulfate)...
CH3-NO2 -H2SO4-> HO-NH3HSO4 + CH2=O
This proces is usually done upon heating but it happens moderately at lower temperatures.While CH3 oxydises into CH2=O, NO2 reduces to HO-NH2 ...

As a mather of fact a good lab procedure to get hydroxylamine sulfate is to mix H2SO4 and O2N-CH2-CH2-NO2 to get glyoxal and hydroxylamine sulfate...although I would spare DNE for other uses :cool: ...

You thus have two extra guest molecules and what VIP guests...
CH2=O is very prompt to oxydise with HNO3...I stil remember the runnaway I had during my first attempt to get CH2(ONO2)3...delayed boiling suffocating mix...man I felt the temp rise so fast a just had the time to drop the contain and take cover a lot of gas... and NOx the HNO3 was only 70%conc and the CH2O was 30% conc and stil reaction was quite fast. Later I tried with (-CH2-O-)3 and got a milder oxydation but speeding up as the prills dissolved and the HNO3 warmed up.
CH2=O + HNO3 --> CO2(g) + H2O + NOx

In this case you have almost no heating and so liberation of NH2OH and CH2=O is slow...concentration remains low but you stil get CO2 bubbles which are scavenged by your ingenious matrix...bubbles also mean hot spots and sensitisation...

Part of the NOx reacts with the NH2OH to form H2O, N2O and N2...here again slow release of tiny bubbles ...and resulting sensitisation.

In the mix dus also:
*NH4NO3, CH2=O --> Hexamine dinitrate (VOD 7000m/s), sulfate
*CH2=O, CH3-NO2 --> CH2=CH-NO2, HOCH2-CH2-NO2, (HOCH2)CH-NO2, (HOCH2)3C-NO2
And the resulting nitric esters...(VOD > 7000 m/s)
*HO-NH3ONO2 (VOD 8000m/s)


Note that from a single slow reaction to make hydroxylamine and formaldehyde, you get more and more other reactions that free H2O...(esterification, oxydations)...there is thus a good chance the mix isn't stable if kept in big quantities at ambiant temp (what favours hotspots). Better consider this mix as "a make and use".

That's it for the chemical point of view.
:):):)

To get a bit back on the track of shaped charges:
1)
*The macroscopic effect can be seen with shaped charges.

*This can be transposed to a microscopic level with the famous "microballoons effect"...those tiny gas bubbles in a hard matrix...are the bubbles or foam that is used to sensitise AN based explosive...they account for the need of low densities (a lot of air in the solid matrix).

If you think wel a detonation wave comes into contact with a hollow sphere...the system is thus a hollow hemispheric shaped charge.In the hollow globe a high pressure and VOD dart forms and percuts the otherside of the sphere and enters the explosive again giving a kick. In low reliability detonating explosives this allow a better propagation of the detonation wave and the use of sub critical diameter of detonation (wich is quite high for plain AN).

The same principle applies to sonochemistry and the cavitation effect... except here the waves are periodic and at a given time, the bubble compressed kind of adiabatically by steps, ends to be unstable and implodes in the almost same fashion...dart from one side imploding the other side of the hollow chamber.
**********************************************
In sonochemical processes very high temps are produced and very high local pressures are reached.
One can observe radical reactions like formation of H2O2 in water with O2, complete destruction of benzene to CO2 and H2O, nuclear reactions (neutrons are formed and they start now to make Tritium from water (the tiny % deuterium allow this)-what will happen if they play with D2O (100%?)..nuclear fusion?)).

Also some unfavourised endothermic reaction vs exothermic major product passes from 0% to 50% yield...
***********************************************

Now that this is said, imagine you make detonators based on the hollow shape principe; I would call this the hollow chamber principle...

Schema:

See attachment

Then an explosive with a too low VOD and initiation property would be transformed into a device of better output and localised efficiency...Since locally the heat of reaction, the pression and VOD would be higher and pollarised in direction of the target explosive at the exit of the detonator...
Advantages lower quantities of explosive needed in detonator for a better effect.
Diminution of the diameter also possible

Sole factor to determine...as a function of the inner diameter of the tube (d)... the position of the center of the cavity (a)...

Note the fact there is a transition explosive...air...explosive and that the hot dart will activate thisone before entering the main charge...this gap might be filled with the same compound as the other side or with another one...3 possibilities then exists...
Fuse --> E1-R-E1--> E2
Fuse --> E1-R-E2--> E2
Fuse --> E1-R-E3--> E2

Test must be done on various explosives to determine if there exist some constant behind this theory!

f(d) = f(e)*f(a)

2)
Your modified ammos...remind me a story my father told me:
When he was at the army (a few 40 years ago), he remember that he had tried "Energa" gun cartiges...those where stange gun bullets looking precisely like common ammos but with a hole on the top.
He remember it made almost no noise upon shooting and had almost no backshoot effect...but when this percuted the armored target...it was perforated and on the other side there was a terrific amount of flame and a sharp detonation...
I'm sure it was based on the shaped charge principle...but it was adaptable to normal gun...I stil don't figure how they didn't had it to explode on shooting...maybe delayed ignition?

Has someone else heard of such things?
My guess is that it was made by the Fabrique Nationnale of Belgium (FN).

:D:cool::D:);):):P:cool::P

[Edited on 16-12-2005 by PHILOU Zrealone]

Attachment: hollow chamber det.ppt (14kB)
This file has been downloaded 1657 times


lacrima97 - 16-12-2005 at 16:41

Quote:
Originally posted by PHILOU Zrealone
Quote:
Originally posted by Axt

2)
Your modified ammos...remind me a story my father told me:
When he was at the army (a few 40 years ago), he remember that he had tried "Energa" gun cartiges...those where stange gun bullets looking precisely like common ammos but with a hole on the top.
He remember it made almost no noise upon shooting and had almost no backshoot effect...but when this percuted the armored target...it was perforated and on the other side there was a terrific amount of flame and a sharp detonation...
I'm sure it was based on the shaped charge principle...but it was adaptable to normal gun...I stil don't figure how they didn't had it to explode on shooting...maybe delayed ignition?

Has someone else heard of such things?
My guess is that it was made by the Fabrique Nationnale of Belgium (FN).

:D:cool::D:);):):P:cool::P

[Edited on 16-12-2005 by PHILOU Zrealone]


I believe sir, what you might be talking about is a "Complete Round of Ammunition?". There is a section in it in Tenney L Davis's Chemistry of Powder and Explosives.

It is a bullet which does in fact have an explosive inside.

I hope this might help and is what you are talking about.

PHILOU Zrealone - 16-12-2005 at 16:50

You play matriochka with quotes...a bit confusing I must say...:D

Axt - 19-12-2005 at 20:50

Quote:
Originally posted by MephistosMinion
Hypothetically, if someone was pissed off at the cost of plasma cutting, and somone wanted to cut 25mm mild steel plate, would a linear charge similar to the one posted on page one be adequite for the job using pressed ETN?


The one as shown, while capable of very clean cuts only managed ~8mm. the 90° aluminium liner didnt show great penetration using NM/70%HNO3. You may get a bit further through with ETN but I think 25mm is a stretch. possibly replace the Al angle with Cu half-pipe.

Quote:
Have you tested the latex bonded cone Axt? Or are you going to try again and make a better one before testing how well it works?


No I cut that one up to see how thick the liner was. I havn't fired the nickel one I made. I've been looking into the casting resin/metal powder with this looking like the easiest way to form a mould:

Using two funnels with spouts that allow centreing of the funnels. Ideally one would place some resin/Cu in the funnel then push the other one into it to extrude it out the top, then clean it up. I think lubricants for molds are sold with the resin? which allows the extraction of the set liner from the funnels. Or just break it free, these glass funnels are only a dollar a piece.

<center> <img src="http://www.sciencemadness.org/scipics/axt/funnel-liners.jpg"> <img src="http://www.sciencemadness.org/scipics/axt/funnel-mould2.jpg"> <img src="http://www.sciencemadness.org/scipics/axt/funnel-mould.jpg"> </center>

Quote:
Originally posted by PHILOU Zrealone
Now that this is said, imagine you make detonators based on the hollow shape principe; I would call this the hollow chamber principle...


Oh.. but they do!

Heres a test I did ~10min ago with a couple commercial detonators, one having a concave end, the other flat. Both are #8 strength containing PETN. They were taped end-on onto 3mm steel and fired under sand.

<center> <img src="http://www.sciencemadness.org/scipics/axt/dimple-detonator.jpg"></center>

MephistosMinion - 20-12-2005 at 02:38

Well having met a new friend who has previously held abn explosives permit and is hopefully going to renew it I think i will use shaped charges for the steel. Is copper half pipe availiable or do I have to cut some copper pipe lengthways?

Axt - 20-12-2005 at 02:52

Quote:
Originally posted by MephistosMinion
Is copper half pipe availiable or do I have to cut some copper pipe lengthways?


Dont think you can buy it as half-pipe. Perhaps just use it as is, it will provide standoff, that extra mm of copper to penetrate may be negligible.

MephistosMinion - 20-12-2005 at 03:54

Well there is a section of the metal that will not be used in the press (that is what I am using the steel for) so I suppose I shall just have to do some testing (hurray soon I can contribute something to this thread that wil be worthwhile and have pics :P)

Would I be correct in assuming that the HNO3/NM mix would react with the copper in a negative way? Also I may try a glass liner if I can find glass at a 90 degree angle.

PHILOU Zrealone - 20-12-2005 at 10:13

:D
Axt,
Displayed the 3mm steel a characteristic hole that proves a shaped charge effect? Is it following you the purpose of the incuved end?
No doubt it has more kicking effect :)!
:P:P:P
"Oh.. but they do!

Heres a test I did ~10min ago with a couple commercial detonators, one having a concave end, the other flat. Both are #8 strength containing PETN. They were taped end-on onto 3mm steel and fired under sand."
:P:P:P

It would be great to test subdetonic stufs and see if under shaped form they can undergo detonation...in theory any convergent shockwave must display such additive effect...increasing pressure and intensity...but not the speed...
For detonating stufs it seems the VOD increases after a slight speed reduction...Right?
Maybe this effect is due to a phase transfer wave passing from solid to gaseous media....? I wonder if by a mere chance such an effect also exist for Solid to liquid phase transfer...
So what would a shaped charge do if water was present instead of a gas...?
Would a vaccuum chamber increase slightly the effectiveness of a common shaped charge?

:D:cool:

[Edited on 20-12-2005 by PHILOU Zrealone]

MephistosMinion - 21-12-2005 at 02:44

I have drawn (or attempted to) a diagram of what I think Axt means by using copper pipe. I appologise for the text in the diagram I am unsure how to change it.

http://img.photobucket.com/albums/v466/mephistosminion/Shape...

I will be making a small test one of theese 5 centimeters long to test on the "offcut" section of the plate.

EDIT: If I can find a cheap amine source to sensitize NM I may use that.

[Edited on 21-12-2005 by MephistosMinion]

PHILOU Zrealone - 21-12-2005 at 05:10

I think he meant that but without the lower half pipe :P;)...thus simply a halfcylindrical shaped charge instead of a ^ shaped charge....

Axt - 21-12-2005 at 06:04

Quote:
Originally posted by PHILOU Zrealone
I think he meant that but without the lower half pipe :P;)...thus simply a halfcylindrical shaped charge instead of a ^ shaped charge....


I originally meant that, but then suggested that the extra mm of Cu on the full pipe would be insignificant if your aiming to penetrate 25mm of steel. Still, you could easily take that bottom off by using a grinding disk on an angle grinder. Run it up and down until it breaks through.

Deceitful_Frank - 21-12-2005 at 09:49

Sorry guys to deviate from the current discussion but concerning the start of this thread and the cylindrical lined shaped charge using the 16mm aluminium tube...

I can source 16.5mm COPPER tubing and am looking to make a shaped charge of similar design using this tubing and 5cm diameter PVC piping.

One question, Do you think that because of the density of copper and the mass of the tubing being three times that of one of aluminium, this would be to the detriment of performance and I would need a wider diameter PVC pipe to compensate and provide more crushing power on detonation to form the molten jet and give good results?

[Edited on 21-12-2005 by Deceitful_Frank]

[Edited on 21-12-2005 by Deceitful_Frank]

[Edited on 21-12-2005 by Deceitful_Frank]

Cu/ epoxy cone formation

chemistr1 - 21-12-2005 at 15:12

The moulding of Cu/ epoxxy is not required as it can be painted on and then built up in layers and then sanded for final finish.
75% Cu 25% resin works well but requires sanding to finish off.

Axt - 27-12-2005 at 06:52

Quote:
Originally posted by Deceitful_Frank
One question, Do you think that because of the density of copper ....


I dont "know" (the word "know" is very powerful!) but if you want me to guess, I'll say no, you won't need a wider diametre charge to compensate. Any bigger and you'll end up punching through it without the help of any cavity, its quite inefficient as is. As I've said previously I dont even know the true nature of the penetration and would be of most interest to make two identical charges and lay one flat on the target and hold one at a couple inches of standoff. That way you can distinguish blast effects from the metal jet effects. This Polish reference may hold the answer, but I dont have nor know how to aquire it.

E. Włodarczyk. "Effectiveness of the cylindrical hollow charge" Journal of Technical Physcs. vol. 42, no. 2 (2001)

Heres an extract thats of interest regarding the discussion of metal powder liners being compressed into cohearent solids:

<u>Explosive Compaction of powders, principle and prospects</u>
Materialwissenschaft und Werkstofftechnik
Volume 20, Issue 12, Date: Dezember 1989, Pages: 410-415
R. Prümmer

<i>"The explosive compaction method consisting of a cylindrical container surrounded by a proper type and amount of explosive is an inexpensive method to achieve high densities close to theoretical density. The explosive's parameters have to be adjusted to the type of the powder to be compacted. The required explosive's pressure is linearly related to the Vickers hardness of the metal powder particles. If higher pressures are applied, an explosive liquid phase sinter - process can be achieved, allowing the welding of individual particles."</i>

And one regarding open poled hemispherical liners, I dont know is this can be related to the open poled conical liners that would result from casting using funnels:

<u>The Behavior of Shaped Charges with open-poled hemispherical liners</u>
Propellants, Explosives, Pyrotechnics
Volume 16, Issue 3, Date: June 1991, Pages: 140-144
Richard L. Summers, William P. Walters, Richard D. Dick

<i>"An experimental study was performed in which various diameter holes were made in otherwise similar shaped-charge liners. Flash radiographs were taken to observe changes in the liner collapse and the jet characteristics. The collapse process and jet characteristics of a hemispherical liner are significantly altered for a hole diameter which is 10% or more of the outer liner diameter. The jet tip velocity is increased by 26% for a hole diameter-to-liner diameter ratio of 0.25."</i>

kABOOM! - 28-12-2005 at 21:50

A small Wine bottle shape charges seem to work well when filled with PLX/Al powder. I tryed this one already! Very hot detonation!

Axt - 4-1-2006 at 07:42

Quote:
Originally posted by kABOOM!
filled with PLX/Al powder.


Aluminium powder can only act to lower detonation pressure in an explosive firing at high velocity, low velocity dets shouldn't be a problem with PLX thus aluminium powder shouldnt be used with shaped charges. <a href="http://scipic2.ft100.net/banners/aluminized explosives.pdf">(ref)</a>

<center><img src="http://www.sciencemadness.org/scipics/axt/sc-comps.jpg"></center>
<center><a href="http://scipic2.ft100.net/banners/explosives with lined cavities.pdf">Birkhoff, G. <i>et. al.</i> "Explosives with Lined Cavities"., J. Appl. Phys., vol. 19, p. 563-582, (1948).</a></center>

[Edited on 4-1-2006 by Axt]

nitro-genes - 4-1-2006 at 21:16

Great review! Very comprehesible... although the mathematics require some more time to think about :D
Like the statement that the depth of penetration is independant of the jet velocity, as long as the jet velocity is high enough to produce pressures far above the yield strength of the target materials. :o
Jet velocity is correlated directly with detonation pressure, so there should be no increase in penetration depth above a certain detonation pressure... Which can't be true. Why should there be any need for superfast explosives with high detonation pressures then?
Another thing is the "wobbling" of the liner, what causes it? Imperfections in the liner, charge density etc? I suspect it is something like a wave, comperable when you move the garden hose while a continuous stream of water is coming out.

Must be great to be able to access all these articles. Not everything can be simply "googled" together unfortunately...:(

Chris The Great - 5-1-2006 at 17:33

I've read most of that review and it is extremely food, and helped give me an understanding of chaped charges I didn't have before.

It DOES make some errors however (it is from 1948), the statement that target hardness is irrelevent has been found to be false, so jet velocity will have an effect on jet penetration in different materials.
Obviously det pressure comes into play somewhere. However, it seems Gurney energy will actually have the largest effect on the performance, as it will determine the liner collapse velocity and hence the jet velocity.

Extremely detailed, explanatory, and very easy to understand. Thank you Axt!

I found the section on using an inverted cone detonation wave to strike the entire liner at once interesting. It should be able to produce 50km/s+ jets, if you take the time and effort to do a perfect job of shaping the detonation shock (much easier said than done). It would be an interesting experiment...

nitro-genes - 5-1-2006 at 18:40

Quote:
Originally posted by Chris The Great
I found the section on using an inverted cone detonation wave to strike the entire liner at once interesting. It should be able to produce 50km/s+ jets, if you take the time and effort to do a perfect job of shaping the detonation shock (much easier said than done). It would be an interesting experiment...


The easiest way to achieve such a thing would be to use a thing that is called a shaped charge lens. It is in fact little more than an improved "wave shaper disc".
In the attachment is a patent dealing with the concept. It will however most likely only apply to hemispherical, and parabolical liners... There isn't any information given about the increase in jet velocity or penetration ability except that it is "significant".
I didn't find any evidence that it is used in a lot of shaped charges nowadays, so it might as well be of not a to great importance for overal performance...

[Edited on 6-1-2006 by nitro-genes]

Attachment: 5565644.pdf (304kB)
This file has been downloaded 1279 times


fallout - 5-1-2006 at 19:29

Not trying to get off subject but these tests of shaped charges are being down with rdx,AP,and i think i seen a post that talk about MEK.Right now i do not have the means to rdx.....once agian i not sure of the matierials that are need to produce RDX i do know that piric,nitric,and sulfuric acids and some sort of acid bath process??But anyways i was wondering about using triacetonetriperoxide,and if its possible about how much would be need for a smaller smaller scale charge?

nitro-genes - 5-1-2006 at 21:02

I seriously want to discourage you from using AP for shaped charges. The maximum achievable detonation pressure of AP is nowhere near that of pressed PETN or RDX, meaning that even with a very strong confinement you would get very little penetration. But pressing one of the more sensitive and notorious explosives over a sharply pointed cone raises the hairs at the back of my neck, even at a less than 10 gram scale...:o
Better use the MEKP you were talking about, no need to press it, less friction and impact sensitive because its a liquid...

back on topic:

While searching the patent database I found this other concept of efficiency improvement for shaped charges which seems to be to good to be true :D
The increase in performance from what I can understand is almost 100% :o (Fig-14)
The range in which the angle can deviate from the optimal angle seems to be quite tight though, so that would require some experimentation...
If only I had the time to try everything out :(

[Edited on 6-1-2006 by nitro-genes]

Attachment: US4109576.pdf (703kB)
This file has been downloaded 1399 times


Axt - 5-1-2006 at 21:55

Quote:
Originally posted by nitro-genes
Why should there be any need for superfast explosives with high detonation pressures then?


Good point, since we know det pressure correlates to shaped charge performance, in fact the "aluminized explosives" article above made use of shaped charges to determine det pressure.

Quote:
Another thing is the "wobbling" of the liner, what causes it?


Yes, I think the water hose analogy is a good one. I'm quite sure they are just refering to inconsistancies within the charge resulting in the jet firing off at different angle along its length, this can be seen in charges that have been purpously made with irregularities. The following was fired with an off-centre detonator.

<center><img src="http://www.sciencemadness.org/scipics/axt/offset-initiation.jpg"></a></center>

Quote:
However, it seems Gurney energy will actually have the largest effect on the performance, as it will determine the liner collapse velocity and hence the jet velocity.


There is this, combining gurney with PER theory. PER is available in FOSC but its all nuthin' but letters'n numbers to me.

<u>The Simplified Model for Predicting Shaped Charge Jet Parameters</u>
Propellants, Explosives, Pyrotechnics
Volume 20, Issue 5, Date: October 1995, Pages: 279-282
Liu Gui-Xi

Abstract
<i>The model is based on the more recent work of Hirsch and the original analytical work of Pugh, Eichelberger and Rostoker. Namely, the simplified Gurney formula for imploding cylinders derived by Hirsch is combined with the PER theory forming one-dimensional computer code, and then it is used for predicting the 80-mm diameter shaped charge jet parameters. Good agreement has been found with the experimental results.</i>

Fallout, <b>stop posting and start reading</b>. No person here has got the time to explain such things to someone, that knows nothing more then how to mix acetone, peroxide and acid together and thinks RDX is made by the nitration of picric acid. Or is that a result of you very poor grammer? Anyway arn't there better forums for you? <font size="1">(ahem... totse.com)</font>

Lotek_ - 5-1-2006 at 22:32

totse is down so they are all here ^_-

Fulmen - 6-1-2006 at 07:46

Quote:
Originally posted by nitro-genes
While searching the patent database I found this other concept of efficiency improvement for shaped charges which seems to be to good to be true :D
The increase in performance from what I can understand is almost 100% :o (Fig-14)
[Edited on 6-1-2006 by nitro-genes]


Great Scott, this is brilliant!

Boomer - 6-1-2006 at 08:28

Just a few thoughts:

- Any reference for the 50 km/s jets Chris? I very much doubt that, *having read somewhere* 2 times VoD is max?

- I also doubt the 100% increase, remember it is a patent. But I'll read it at home before further commenting. On a side note, for improvised liners this will help little, since jet breakup is caused by non-perfect symmetry more than by turbulent gas flow around it.

- I agree det pressure is more important than gurney. We *squeeze out* material by pressure, we dont accelerate it like a fragment. Maybe the slug is faster (useless)?

I knew about radioactive fallout, intellectual fallout was new to me... :P

Chris The Great - 6-1-2006 at 11:59

The 2x det velocity is for a cylinderical cavity with a standard detonation shock wave passing over the liner over a period of time.

The theoretical 50+ km/s one has the detonation shock wave coverge on the liner and impact all points on the liner simultaneously. In this case, the jet velocity can (in theory) increase to inifinity as the liner becomes closer to a cylinder, while the momentum decreases to zero at the same time, and (theoretically) depends solely on the angle of the liner. So, for example, a 85 degree cone being impacted by a detonation shockwave shaped exactly the same, would produce a jet with the velocity of about 70km/s (and very little mass).

EDIT: US Patent 6,167,811 looks interesting... I haven't had time to read it since lunch is almost over. From the abstract:
Quote:
In operation, a conically capped hemispherical liner is collapsed in reverse sequence. Detonation of the base of the hemisphere, done earlier in sequence, produces a thick massive jet for initial penetration as a deep crater, in the armor. The conical liner is collapsed afterward, producing a thin jet which reaches the armor deep into the crater earlier produced, at an increased distance than would be usual without a crater.


[Edited on 6-1-2006 by Chris The Great]

Joeychemist - 6-1-2006 at 15:46

Quote:
Originally posted by Boomer
Just a few thoughts:
- Any reference for the 50 km/s jets Chris? I very much doubt that, *having read somewhere* 2 times VoD is max?


According to Melvin Cook in his book "The Science of High Explosives", the velocity of the liner NEVER reaches a full 2x the velocity of the explosive employed in the charge.

nitro-genes - 7-1-2006 at 06:39

Quote:
Originally posted by Boomer
I also doubt the 100% increase, remember it is a patent. But I'll read it at home before further commenting. On a side note, for improvised liners this will help little, since jet breakup is caused by non-perfect symmetry more than by turbulent gas flow around it.


Yes, patents are usualy fairly vague concerning precise data. But this patent seems to give some real experimentational data. The penetration was measured in grannite however, and 4 times cone diameter in grannite seems poor performance to me...
You are right about the fact that the jet breakup is caused mainly by imperfect cone symmetry and charge density, however the improved gasflow seems to allow the jet to form over a smaller distance, increasing the effective length of the jet by decreasing optimal standoff... (1-1,5 cone diameters instead of 2,5) I see no reason why this should not apply for an improvised liner. Even if the breakup lenght of the jet will be the same, the standoff can be reduced to 1 cone diameter, thus increasing the effective jet length with 1 cone diameter! :D

For the 50 km/s jets, even if they would exist I wonder if they would be very effective.... A very thin, low mass jet traveling at the tip at 50 km/s would create such an enormous velocity gradient from tip to slug that very quickly the jet would disintegrate into tiny particles (jet density is very important in correlation with penetration). So the breakup time of the jet will be very short. (Maximum strain rate that copper can handle before diintagration is constant I think) Of course because of it's large velocity it will cover more distance in this short time. Maybe they cancel eachother out... Question thus is if a 50 km/s jet would have a longer effective length :P (Edit: I think this is what they mean by saying that penetration is independant jet of velocity!)

If I understand well there should be a correlation between the detonation pressure or Gurney energy and jet lenght?!

Edit: left the fucking insert on while typing, explains the all the edits ;)

[Edited on 7-1-2006 by nitro-genes]

[Edited on 7-1-2006 by nitro-genes]

[Edited on 7-1-2006 by nitro-genes]

[Edited on 7-1-2006 by nitro-genes]

ZoSo357 - 17-1-2006 at 15:47

I was thinking, with shaped charges, is there an angle which the cone should be that has the highest possible penetration? Inline with the munroe effect, the direction of the surface of the explosive, is the direction that the force will travel. Having said that, say something with too small of an angle was used, would a lot of the energy near the "peak" of the cone be wasted on the inside of the charge itself?

I have included a diagram to help explain better. Basically what is happening here, is the red lines show the direction of the cone's movement. (yes, MS paint diagram:( )I tried to show that if you were using a 90 degree angle cone, it would work well, where as using, say a 45 degree, or something like a 150 degree angle cone, you may be losing a lot of the penetrating power since the peak of the cone will be just "sandwiching" in on itself. In the case of using cones, would a 90 degree angle be most efficient for penetration?

[Edited on 17-1-2006 by ZoSo357]

angles.bmp - 220kB

Quince - 17-1-2006 at 21:01

Just run a FEM simulation and see for yourself. There are plenty of tools that make it easy for you, like Fastflo and stuff.

[Edited on 18-1-2006 by Quince]

Axt - 18-1-2006 at 05:08

Its a trade off between jet velocity, mass, length and stretch.

Typically the smaller the angle the faster the jet with lower mass percentage of liner in the jet (the majority of the liner doesnt form a jet at all rather a low velocity "carrot"). Also, for example in a 40° cone will weigh more and contact the explosive over a greater area then in a 90° cone. Typically somewhere between 40-60° angle is used.

Its only the skinny spike at the front that penetrates, the black lump at the back is the "carrot".

<center><img src="http://www.sciencemadness.org/scipics/axt/liner angles.jpg"></center>

[Edited on 18-1-2006 by Axt]

nitro-genes - 18-1-2006 at 15:46

About angels... I just tried a 15 mm shaped charge with a 0,4 mm, 60 deg. copper liner. The liner was made from 2 layers of 0.2 mm coppersheet like boomer did. (Hopefully you didn't patented it yet :P )
And although the use of copper made the charge fully penetrate the 1" steel plate, the entrance hole is a mess... (Because coppersheet is realy expensive I always used aluminium sheet) You can see small dimples in the steel surrounding the entrance everywhere.

My question thus is, if a decrease in the liner angle would make the demands in symmetry of the liner less than when you use a larger liner angle. In other words, would the jet form more easily at, say 40 deg. then at 60 deg.? Coudn't find any evidence for this, it is just a feeling so to say. :)

I used Petn/Pib plastique which is quite stiff, so I had to really mash it to get it in the smaller spaces of the charge. So that surely didn't help...
Petn/NG is an option, but I have very little information about sensitivity, stability and "how it handles" I've heared about 50/50 compositions that form a viscous liquid that can be poured if one wants to... But than again what about low-order detonation?

[Edited on 19-1-2006 by nitro-genes]

Quince - 18-1-2006 at 17:22

Is blasting gelatine suitable for shaped charges? I don't have any PETN.

Chris The Great - 18-1-2006 at 19:09

I would imagine it would work decently for larger charges. Nitroglycerin isn't as easy to detonate like PETN so you will need a powerful cap and good charge diameter. Probably be best to use a methyl nitrate gelatine, since methyl nitrate is a high brisance explosive and also very easy to detonate like PETN. Or at least use EGDN... nitroglycerin isn't that brisant of an explosive and EGDN would be a good improvement. Methyl nitrate would be best, but raises some challenges with handling.

Axt - 18-1-2006 at 22:53

Quote:
Originally posted by nitro-genes
Petn/NG is an option, but I have very little information about sensitivity, stability and "how it handles"

I've never had problems with PETN/NG which should be no more unstable then its parent compounds. I've never weighed the quantities, simply drip NG into it until it forms a soft plastic consistancy.
Quote:
Originally posted by Chris The Great
Probably be best to use a methyl nitrate gelatine.

I'm not so sure methyl nitrate would do any better, since the susceptability to LVD is largely dependent on viscosity, increasing MN's viscosity with NC to that of blasting gelatin would likely make it just as prone to LVD.

Coolio - 19-1-2006 at 07:45

I made twice times ANNMSA


At first the AN SA mixture geht really hard, after also poored the NM into it, it stayed hard....

then ein crushed this and mixed it very "brutaly"

but it was very liquid, and on the surface there were just liquid NMSA....

wtf do i wrong ?? :(



*sorry for my bad english, I am from Austria ;) *


@ axt, have you got an icq nummber ?

it would be an honor for me to be able to write with you about your recent "breakthroughs"

[Edited on 19-1-2006 by Coolio]

Chris The Great - 19-1-2006 at 17:01

As far as I know, methyl nitrate does not LVD easily. A #1 blasting cap gives 520 in the lead block compared to 615 with a #8. As far as I know those values are uncorrected for the cap size so that would move them even closer.

The idea with the gelatine is because methyl nitrate has a VERY low viscoisity, and it would leak out of the charge :P I gelled a some of it and it is very thick, and so it would stay put after you put it in the shaped charge. 9% nitrocellulose seems to be a bit too much in my opinion, a bit less might make it easier to get into the charge evenly.

Since methyl nitrate has a fair 240% of TNT by the plate cutting test, I imagine it would have good performance in a shaped charge.

nitro-genes - 20-1-2006 at 04:12

Quote:
Originally posted by Chris The Great
As far as I know, methyl nitrate does not LVD easily. A #1 blasting cap gives 520 in the lead block compared to 615 with a #8. As far as I know those values are uncorrected for the cap size so that would move them even closer.


Pure methylnitrate has a very low viscosity, much lower than NG. That is exactly why methylnitrate is less susceptable for LVD in the lead block tests! ;) The low viscosity allows for a better shockwave propagation and thus a higher DV. Unfortunately, that doesn't change anything about the fact that increasing the viscosity of methylnitrate will make it more sensitive to LVD...

[Edited on 20-1-2006 by nitro-genes]

PHILOU Zrealone - 20-1-2006 at 05:28

Quote:
Originally posted by Coolio
I made twice times ANNMSA


At first the AN SA mixture geht really hard, after also poored the NM into it, it stayed hard....

then ein crushed this and mixed it very "brutaly"

but it was very liquid, and on the surface there were just liquid NMSA....

wtf do i wrong ?? :(


[Edited on 19-1-2006 by Coolio]


Mix SA with ANNM and not NM with ANSA!!!!

PHILOU Zrealone - 20-1-2006 at 05:32

Quote:
Originally posted by Chris The Great
As far as I know, methyl nitrate does not LVD easily. A #1 blasting cap gives 520 in the lead block compared to 615 with a #8. As far as I know those values are uncorrected for the cap size so that would move them even closer.


As far as I know lead block test is:
Volume of of deformation due to the detonation/explosion of 10g of explosive with a given detonator (V total) minus the volume produced by the detonation of detonator itself (V detonator)

V total - V detonator = V lead block test

So there is a correction factor!


Maybe it is not linear!

Axt - 20-1-2006 at 06:21

Umm. yep, Chris you read <i>"I'm not so sure methyl nitrate would do any better"</i> but not <i>"increasing MN's viscosity with NC to that of blasting gelatin would likely make it just as prone to LVD"</i>. This is only speculation but I cant see the point choosing a low viscosity liquid to prevent LVD if your only going to increase the viscosity by gelling it.

As to the ANNMSA, this was covered before in this thread, you have to add NM to ANSA or one ends up a solid covered by a thick layer of liquid. Coolio, if your just pour the NM in and leave it, it will form a granite hard solid, it must be <b>stirred</b> in prefereably while <b>hot</b> to create the precipitation of AN/AS in the crystalline form that best holds onto all the liquid. It sounds like you cooled it down making the AN/AS precipitate prematurely.

[Edited on 20-1-2006 by Axt]

Fulmen - 20-1-2006 at 07:07

Getting back to the subject of sylindrical liners, I was wondering if the liner should be sealed at the top or not, and if so, what the shape should be. If left open, wouldn't the gasses from the explosion fill the liner and possibly disturb the formation og the jet?

BTW, any suggestions on how the following charge should perform:
Container: 62mm diameter, 90mm high
Liner: Copper tube 22mm diameter, 60mm high, 1mm thick walls
Charge: appr. 250g NMANXY (kinepak)

Deceitful_Frank - 20-1-2006 at 11:09

By the sound of it you are using a composition very similar to the one that I use. An excellent explosive, albeit not a very dence one... check out my thread on plate dent testing as I'm sure you'll find it of interest :)

As for this cylindrical lined charge, I think you could do with using a slightly taller casing and maybe 16mm copper tubing, though staying with what you have, if I were you I'd give it more comparatibe head height by reducing the length of your copper tube to around 45mm.

I have calculated the filling space inside your vessel (obviously minus the cavity) to be 237ml using your tube and reducing the length to my suggested 45mm.
I am still in the process of finding out if this 80:16:4 kinepak performs best at 1.0, 1.05 or 1.1g/cm3 but I think if you go with 1.05 and 249 grams pressed evenly with the back of a spoon then you wont be dissappointed. I would either find or sandwich together 30mm of steel plate, use a standoff of just the one diameter or about 60mm and initiate with a full gram of fresh HMTD or the equivalent :)

Dont forget to keep us posted as I'd be very intersted to learn of your results!

Fulmen - 20-1-2006 at 11:41

I thought the "1 diameter" was based on the liner diameter, so 60mm would be nearly 3x. Sounds a bit much for a homemade charge, don't you think? Regarding the performance, 30mm??? That's nothing, I pierced 15mm with a 7.62Nato jacket and 3,5g RDX. Sure kinepak is a lot weaker, but come on! Anything less than three inches is a failure in my book :-)

As for head height you might be right, the problem is that the liner is already glued to the container. Not sure if it's worth the trouble of removing it without destroying everything. Maybe I can increase the height of the charge somewhat instead.

How much does initiation influence the performance? I was thinking of a regular blasting cap, but I might spend a gram of RDX or two if it makes any real difference...

Deceitful_Frank - 20-1-2006 at 11:58

Hee hee! you are right about the standoff! It has been a long day and I'd forgotten whilst typing, that this isnt a conical liner. I feel that your cylindrical liner is a little too wide for the diameter of the charge else I would have suggested an inch.. maybe one or two centimeters would work better?

If you had NO standoff would it be at the detriment of performance due to the air in the cavity having nowhere to go?

Cylindrical lined charges are very inefficient though simple to make. If you are serious about less than three inches meaning failure then I really wouldnt waste your time! ... I trust you WERE joking :)

I havent experienced obvious LVD with this composition though I do think diameter and confinement helps. It seems to either go full power or not. I dont have access to commercial blasting caps but have a good supply of penlids that hold a gram of HMTD nicely. If you have atleast #6 caps the I wouldnt bother with RDX as well.

Deceitful_Frank - 20-1-2006 at 11:58

Hee hee! you are right about the standoff! It has been a long day and I'd forgotten whilst typing, that this isnt a conical liner. I feel that your cylindrical liner is a little too wide for the diameter of the charge else I would have suggested an inch.. maybe one or two centimeters would work better?

If you had NO standoff would it be at the detriment of performance due to the air in the cavity having nowhere to go?

Cylindrical lined charges are very inefficient though simple to make. If you are serious about less than three inches meaning failure then I really wouldnt waste your time! ... I trust you WERE joking :)

I havent experienced obvious LVD with this composition though I do think diameter and confinement helps. It seems to either go full power or not. I dont have access to commercial blasting caps but have a good supply of penlids that hold a gram of HMTD nicely. If you have atleast #6 caps the I wouldnt bother with RDX as well.

Fulmen - 20-1-2006 at 12:22

Quote:
Originally posted by Deceitful_Frank
If you had NO standoff would it be at the detriment of performance due to the air in the cavity having nowhere to go?


Not really sure, since the tube collapses at supersonic speeds the air will create a high-pressure front no matter what. Could be that it plays a role as the collapse reaches the end of the tube...


Quote:

Cylindrical lined charges are very inefficient though simple to make. If you are serious about less than three inches meaning failure then I really wouldnt waste your time! ... I trust you WERE joking :)


Not really. If you look at the first posting by Axt you'll se that a similar charge with an aluminium liner punched a clean hole through a 1" plate. Now, copper is said to be almost twice as efficient as aluminium, and it doesn't look like Axt's charge had any plans of giving up anytime soon. My guess is that he could easily have penetrated another 1/2-1", so 3" doesn't sound THAT far-fetched. Or am I missing something here?

Deceitful_Frank - 20-1-2006 at 12:35

Yes, I see your point, the wider lined charge would have deffinately gone another half an inch though I doubt one inch further. 3 inches is not THAT far fetched I suppose though ANNMSA on paper is going to be denser and more homogemous than the kinepack.

If you can give your charge 5cm more height then maybe 2 inches penetration but not three... I'd love to see you prove me wrong though :)

Axt - 20-1-2006 at 14:25

Quote:
Originally posted by Fulmen
Or am I missing something here?

I dont think its a metal jet that created those holes, in fact I suspect if there were no liner the same thing would have happened. Thats why I suggested back a few pages to hold the charge off a couple inches, just to remove the blast effects from the target. See what the metal jet and only the metal jet is capable of.

If it was a "hole punch" that created those holes, which I suspect it was, then it may do very little to 3" plate as its either going to go straight through or not far at all. Alternatively it may push a small diametre hole through it, that was masked by the "hole punch" effect on the 1" plate.

Firing a charge with standoff should tell us what effect is doing what.

Coolio - 21-1-2006 at 01:15

I want to shoot throug a 6cm thick steel plate....

Do you think this is possible with annmsa an the cylindrical linder shaped method ?

which amounts of HE, length of the liner...?

[Edited on 21-1-2006 by Coolio]

Fulmen - 21-1-2006 at 10:45

Guess I'll just have to see for myself. But heck, thats half the fun anyway :-) I have placed an order for a piece of steel at least 60mm in diameter and 4" long, this should be more than enough. The idea is to split it in half afterwards to get a little more information on just how the metal behaves. Or should i reduce the length to 2-3" and see if I can get full penetration with spalling?

I've attached a drawing of the charge, do you think the metal cap will disturb the jet formation?

22mm Linjær#2.PNG - 17kB

Fulmen - 22-1-2006 at 06:57

Another idea would be to use an empty CO2-cartridge as the liner. It's made from steel, but that is supposed to be a bit better than aluminium and the hemispherical end should guarantee the formation of a jet. Also, the length of the liner gives a standoff of appr. 3 diameters so the charge should work without any additional standoff. So even if the sylindrical part fail to produce any additional jet it should neverttheless work as a unlined charge.

What'ya think?

CO2-charge.PNG - 15kB

Coolio - 22-1-2006 at 08:08

I think co2 cartridges are a little bit to hard,... but maybe it works with petn/rdx/hmx..

But why use co2 cartridges ? It`s not very difficult to get copper pipes...

I have an idea...i think it would be possible to use glas test tubes. They also have the same form like co2 cartriges.

It should work with HNO3/NM

ZoSo357 - 22-1-2006 at 08:15

I was just cutting apart a CO2 cannister to see how thick the metal wall is, and it seems like it may work, the wall is pretty well dead on 2 mm, so this seems like a good liner, but also, when i cut it off just from the tip, I noticed the tip may make a good cone. The cone almost fits into a half inch copper pipe, so this may make a good charge for something slightly bigger than the bullet jacket cones. Also you could cut off just the "butt" of the CO2 cannister and get a hemispherical charge without using the rest of the cannister. I don't have a camera right now to take a picture of this. sorry.

EDIT: Fulmen, I was talking to a friend over at APC forum about using test tubes, and you can usually buy culture tubes by the hundreads for really good prices, usually about 5 cents a tube.

[Edited on 22-1-2006 by ZoSo357]

Fulmen - 22-1-2006 at 14:01

To be honest I'm having some doubts about the CO2-cannister. Going from a sphere to a cylinder means that there will be an increasing jet velocity during formation, and that just might cause problems. Think about it, the first part of the jet from the hemisphere vill be a fairly high mass, low velocity jet, while the cylinder should produce a high velocity, low mass jet. What will happen when the latter jet catches up with the first one? My fear is that the collision will simply disperse the jet causing havoc in the bottom part of the tube.
This could account for the "head" in these pictures: http://www.llnl.gov/str/Baum.html

For a simple hemispherical charge this might not be a problem, but inside a long cylinder I'm not so sure.

This is also supported by the fact that the prefered shape today seems to be a trumpet shape. This shape has a increasing angle througout it's length, resulting in a decreasing velocity profile.

ZoSo, I like your idea. I suppose both ends could be used for smaller charges, especially the tip since it has an almost perfect trumpet shape.

As for the sylindrical liners, I still belive in them:D
Remember that the trumpet liners start out as an open cylinder, why would they choose this design if it didn't work?

Test tubes is a nifty idea, I't got me thinking of using Erlendmeyer-flasks. Guess I'll have to look around to see if I have any glassware that can be sacrified for science.

[Edited on 22-1-2006 by Fulmen]

[Edited on 22-1-2006 by Fulmen]

oneup - 23-1-2006 at 05:58

Axt, you're using an explosive mixture that contains strong acids, and you're bringing it in contact with an aluminum liner. doesn't it eat through?

Coolio - 23-1-2006 at 07:25

Alu is resistant against HNO3 ;)

oneup - 23-1-2006 at 08:19

but not against h2so4

12AX7 - 23-1-2006 at 13:22

Um, I've distilled NH4NO3 + H2SO4 with aluminum before. As long as there is very little moisture present, it does not get attacked significantly.

Tim

oneup - 24-1-2006 at 01:29

hmmm aluminum itselve might be resisitant. but i'm sure aluminum OXIDE is not. all oxides are basic, and are thus atacked by strong acids (correct me if i'm wrong) and becouse aluminium always has an oxide layer a small ammount the aluminum sulfate/nitrate will contaminate your acid.

Boomer - 24-1-2006 at 02:22

So what? 1% contamination in a shaped charge filling would not worry me in the least. If it forms a few bubbles, so much the better (detonation transfer).

Plus, does saphire really dissolve in sulfuric?

ZoSo357 - 24-1-2006 at 03:32

I found this by searching google:

http://www.monocrystal.com/products/s-features

And if you can't access that link:


Sapphire features


Benefits

Withstands high temperatures


Will not melt until 2050°. Maintains purity
in high temperature environments

Hard and strong


* High processing survival rate
* Scratch resistant to most materials
* Withstands high pressure
* Excellent wear surface

Chemically inert, insoluble
in most common industrial
solutions and corrosion resistant
(i.e. hydrofluoric, sulfuric
and hydrochloric acid)


* Can be used in harsh environments
* Can be easily cleaned
* Longer life
* Free of contaminants
* Sapphire life is up to five times that
of quartz in some environments

Transmits ultraviolet, visible,
infrared and microwaves


Excellent waveguide performance at 0.25 - 4 microns
Durable and reliable IR laser transmission

Has excellent electrical properties


Low dielectric constant

High thermal conductivity


Provides rapid heating and cooling capability

Coolio - 24-1-2006 at 09:31

A few weeks ago I tested a linear shaped charge with ANNMAL 94:25:4 :o :P

I know the idea is bullshit, but I don`t matter.....

Here is the vid:

http://rapidshare.de/files/11736125/LSC.mpg.html

Coolio - 26-1-2006 at 10:56

hm nobody is interested in my video...


question: Is it a mistake to make a standoff of 15mm by a cylindrical shaped charge ?

rot - 26-1-2006 at 13:48

12AX7, you're using Nitromethane/Nitric acid 70%. doesn't this 70% HNO3 contain way too much water?

12AX7 - 26-1-2006 at 14:08

Quote:
Originally posted by rot
12AX7, you're using Nitromethane/Nitric acid 70%. doesn't this 70% HNO3 contain way too much water?


Um? I haven't produced NM yet, and if you're speaking of an explosive composition, I haven't done any experimentation with that either. You must be referring to someone else.

Tim

Boomer - 27-1-2006 at 00:22

He uses distilled (99%) nitric, and he uses 70% of it with 30% NM.
That is like 100% pure HCl (i.e. no soaps etc) of 30% concentration (rest water).

nitro-genes - 27-1-2006 at 07:50

70% nitric acid with 30% NM would have a far to positive oxygen ballance...70% nitric acid with 30% nitrobenzene is maybe the composition you are confused with.

I believe the original composition of this NM sprengel type explosive was 70% NM with 30% nitric acid (99%.) There is some information about it in PATR. But as can be seen from Axt's movies, apparently 99% nitric acid can be substituted with 70% in the same quantity...

Axt - 27-1-2006 at 09:49

Its 70% HNO3 straight out of the bottle. So yes it did contain a bit less then 10% water. Obviously your better off using distilled nitric but if your lazy you dont have to, its plenty sensitive enough, even when containing a good portion of water.

For the record, with distilled nitric the best density/OB is about 62:38 NM/HNO3. Can you give that PATR reference nitro-genes, ive never seen it, I just used that ratio because it sounded good :)

Anyway ... back to shaped charges ay. :(

Axt - 28-1-2006 at 04:19

Below is 80% copper, 20% polyester cast in the funnels shown on page 6. 80:20 was pourable. Cones ended up a bit heavy duty. The taper on the plastic funnel stems didn't allow the wall thickness to be reduced further.

I broke the stems off the glass funnels trying to get it out, this was likely caused by slight defects in the glass as it wasn't completely smooth, had a bit of a "ripple" in it.

The set cone come out of the plastic funnels easily. I used some spray on wax stuff to prevent it sticking.

<center><img src="http://www.sciencemadness.org/scipics/axt/resin-liners.jpg"></center>

[Edited on 28-1-2006 by Axt]

nitro-genes - 29-1-2006 at 13:33

They certainly look quite promising! Hopefully you are going to try them out soon...:D What is your estimation of the density of the material? Is it still realy dense like copper alone?
They might prove to be a little too thick indeed :(... I've read that aproximately 3% of the charge diameter should be the thickness of the liner for soft copper. My own attempts with steel liners of 2,5 mm thickness and 5 cm diameter resulted in a rather shallow penetration hole almost completely filled with the steel from the liner. :)

As for the reference in PATR about NM/Nitric acid:

This is what I was able to find again. I am sure I have seen more information about it elseware too when I was considering to try this explosive for myself....:( (Which I never did because of the arrival of a new 2,5 kilo's of PE ;))

EXPLOSIVES NONMILITARY (COMMERCIAL)
(Papers and Reports Listed in Chronological
Order)

R.W. Lawrence, CanadP 417844 (1944) 8~
CA 38, 1644 (1944) (Expl contg concd nitric
acid and nitroparaffin, such as nitric acid
15-63%, nitromethane 85-37%)

[Edited on 29-1-2006 by nitro-genes]

Axt - 30-1-2006 at 15:08

No, the density is only about half that of copper, even though it started out 80% Cu by weight, the low density of the binder really cuts it down. So I really dont know whats going to happen, only one way to find out. The smaller liner (33mm) still weighs 17g.

I did find reference to open apexed conical liners, saying that its "desirable" to have an opening at the apex 1/10th the cone diametre. Not stated what they mean by desirable, but the previous abstract I posted relating to open apexed hemispheres mentions faster jet velocities. So I'll try to leave it as is.

Below is the .357 fired in same fashion as .45 on page 5, 3mm plates clamped together and fired through the side. Penetration was just short of an inch, though with a much thinner jet which for most of its length staying within the boundary of the 3mm steel, bulging it out as it passed through. The .357 is a nicer shape then the .45, which is quite flat on top.

<center><img src="http://www.sciencemadness.org/scipics/axt/357-peno.jpg"></center>

[Edited on 2-2-2008 by Axt]

Fulmen - 31-1-2006 at 09:24

Nicely done Axt. Impressive performance, although it is obvious they could do with a increased charce diameter. Personally I'm going to put the cylindrical charge on hold for now, as I stumbled over a 54mm stainless hemisphere in the form of a ladle. It's perfectly smooth and appr. 0,5mm thick, should do for an impressive blast. The only question is the subcalibration ratio (charge diameter to liner), is there a good rule-of-thumb to follow?

nitro-genes - 31-1-2006 at 12:08

This concept of copper powder bound by polyester is quite appealing, but what if you would mix this copper powder with the same plasticizer you would use for making C4 or semtex? The result would be a very high density 90+% copperclay which is still easy to mold. The same prinicple is used with the new "silver art clay" When baked, the organic binders "bake out" and a 99,9% metallic material remains with minimal shrinkage.

--> http://www.artclayworld.com/artclaytosilver.html

I don't see any trouble using copper powder as a subsitute for silver powder only that the melting temperature is slightly higher for copper... Forming a liner out of this clay would be more easy than pouring one I think.

First roll out the clay to a determined thickness by rolling over two plates of the desired liner thickness with the clay in between. Then cut out a circle, and lay it over a hemispherical mold for a hemispherical liner or use half the circle to form a cone. Put in a high temperature oven or use a blowtorch to heat and the liners should be ready...

As with all ideas this might sound simpler than it realy is...But I realy think when you would be able to make a good moldable clay from copper powder it would be worth the effort...

I know I'm not supposed to ask, but did you make this copper powder yourself Axt? I did a search on the internet, but couldn't find any OTC supplier of copper powder. (that delivers to individuals that is)

[Edited on 1-2-2006 by nitro-genes]

Axt - 31-1-2006 at 20:51

Quote:
Originally posted by Fulmen
Nicely done Axt. Impressive performance, although it is obvious they could do with a increased charge diameter.


I think you'll see more efficiency the larger the diametre, but less efficiency for explosive weight. Above was only 1.2g penetrating just shy of 1", thats the equivalent of a 200g SC penetrating over 4m of steel. You wont get that from larger charges, but you may penetrate more "LD's".

Quote:
The only question is the subcalibration ratio (charge diameter to liner), is there a good rule-of-thumb to follow?


Yes, most hemi sc drawings I've seen do have a larger diametre explosive loading then the liner. Right now I'm looking at a SC designed for the Jap kamakasi's in WWII. It had a 1.6m wall and 1.4m hemi liner (with 32cm hole in apex). May give you something to go off.

Interesting Idea nitro-genes, but a lot of question marks above it, like using other metals and polymers to create the same effect may not work at all.

The copper powder was bought, and sold for the purpose of resin filler. There is a topic here regarding precipitated Cu by reducing copper sulphate with vitamin C, may be an alternative, check it out.

[Edited on 1-2-2006 by Axt]

Fulmen - 1-2-2006 at 04:59

1.6m? Damn! Anyway, I ended up with the exact same ratio for my charge, since the can intended for the sylindrical charge was the most practical container i had around. Not sure how much effect kinepak will give at the edge, but it should be impressive nevertheless. There is only 4-5mm space at the end, hardly enough to sustain detonation, but then again the detonation waves will continue some distance anyway, right?

I agree that the gram-equivalent performance for the jacket-charges is quite impressive, I guess it's just a question of what is more valuable, the liner or the explosive. Next time, try to cut the jacket at the crimp-groove, I have a sneeky suspicion that the sylindrical section might disturb the collapse somewhat.

On that note, how does hemis and cones compere to each other? Are the cones more efficient no matter what, or do they just perform better for a given diameter (usually a limitation in ammunition)? Looking at xrays of collapsing liners it seems to me that the hemis deliver more mass to the target, but I'm not sure how the tradeoff between mass and velocity affects performance.

BTW, have you tried EFP's? Sounds like a fun alternative to regular target shooting ;)

h0lx - 1-2-2006 at 05:57

If we are getting into test tubes, why not use the bottom from a centrifuce tube? http://www.biomedicalmarketing.com/Simport/CultureTubes/T420...
These on the picture afe plastic, but this is the picture with the most promising angle on the bottom.

Swany - 1-2-2006 at 10:22

Perhaps because they may not make them in glass? The only ones that I have seen have been plastic.

The bullet-jacket charges are very appealing, as I am working on some high-preformance explosive cast mixtures and plastiques. I belive for charges that small, it may simply be best to stick with single types of explosives though.

I am developing a ETN/TNP cast comp that may be interesting as a shaped charge explosive, though it needs to be kept very dry. It has some interesting properties...

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