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Author: Subject: Prince Rupert's primary?
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[*] posted on 25-12-2017 at 09:16
Prince Rupert's primary?


Perhaps the fumes from the eggnog are affecting my reason, but I've had a thought.

I just watched a prince Rupert drop shatter. Speed of propagation quoted as speed of sound in the glass, around 1,600 m/second for cheap, low density soda glass. That's a good bit faster than is required for a bullet to initiate some secondary explosives, granted that this effect has some other components than mere speed of a projectile impact.

"Glass" can be a lot denser than this. Not sure about the thermal coefficient of expansion to produce the stress required for the effect in the very dense glasses, leaded glass? Optical (flint, crown?) glass? A quick look at online sources for predicting speed of sound in solids shows several other physical characteristics that will affect this, have not corelated these with any candidate materials yet. But let's assume it is possible to fabricate stressed "glass like" objects cranked up in density and otherwise tuned to "shoot" as rapidly as possible? Perhaps obtaining propagation speeds of shattering 2-3X or more of the observed speed in soda glass???

Initiation of secondary explosives is said to depend on the speed of the impulse applied more than the total energy of that impulse... Some relatively low energy but high speed reactions are known to serve.

Has anyone tried initiating a fairly sensitive secondary via the stress release from this type of shattering? A type of NPED detonator with no fuse, electric match or high speed discharge of hefty capacitors required. Just scratch the "tail" to shoot.

[Edited on 25-12-2017 by Bert]




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[*] posted on 25-12-2017 at 09:26


Interesting idea.

Not sure the finished item would be safe to transport.

Maybe best to pack with mince pies for safety.




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[*] posted on 25-12-2017 at 11:47


Wouldnt this also be safer? The tails can be protected. Yes its a really interesting idea, I am surprised the speed is the same as sound waves in the glass. In slow motion films it looks alot faster than that.

A drop made with quartz glass would be interesting to film shattering. Do they shatter along a defined stress line or is it more a wave moving forward effect (if that makes sense?).
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[*] posted on 25-12-2017 at 13:20


I believe the high lead content glasses aren't really glasses but crystal, so in addition to the added density there may be some effects from the (presumably) less flexible material.

Might give higher kinetic energy?




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[*] posted on 25-12-2017 at 13:59


The energy from the explosion comes from strain in the surface of the glass. It should be possible to increase it by squeezing in ions in the glass. Applied science made gorilla glass by immersing microscope slides in molten alkali nitrate for some time.

I think this is better suited as a cheap primary because you will still want to be far away from any explosion involving glass and/or a secondary. If you used it as a detonator you would still want to trigger it electrically for maximum safety. The easiest way to do that - assuming the tail of the drop is somewhat resilient - is with a small detonator which would just add unnecessary complexity and danger of accidental detonation.

Still i think it will be hard to get to work reliably because of the tails varying shape and the droplets stability. Maybe you can see it with polarized light or something?


Writing on mobile sure is a pain...

[Edited on 25-12-2017 by Σldritch]
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[*] posted on 25-12-2017 at 14:30


Very interesting phenomena and idea :)

In terms of energy density, transfer and "pressure" produced it is unlikely to work as a primary probably, at least for normal soda glass. Glass is almost incompressible (like hydraulic fluid), so unlike a rubber band e.g, I would say it can only store a very small amount of energy.

[Edited on 25-12-2017 by nitro-genes]
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[*] posted on 25-12-2017 at 15:05


Two properties are required here, the drop needs to store a good amount of energy and it has to have a high speed of sound. Since the outside layer is compressed and the inside is stretched, the material needs good tensile strength and toughness to store a lot of energy. Soda glass has an ultimate tensile strength of around 33 MPa while fused quartz has 48 MPa so there is quite a difference there.

Speed of sound is calculated as the square root of the bulk modulus divided by density, so to get high speed of sound the material needs to be light, not dense! The speed of sound in glass is between 4000 and 5000 m/s and a bit higher, 5800 m/s, in quartz according to some sources.
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[*] posted on 25-12-2017 at 15:24


There are at least two technologies besides the liquid quench induced strain of the classic Princ Rupert's drops. One is placing melted glass in a chilled metal mould, such that the skin is frozen while the interior is still plastic and expanded.

The other I know of is to fabricate the (Soda) glass shape, and then soak it in a melt of Potassium nitrate. A good portion of the Sodium atoms in the outermost layer of glass will exchange with Potassium from the melt, as I see it described, potassium atoms require about 30% more volume than Sodium, which causes the Potassium doped skin to compress the Sodium based core material.

Both of these methods bypass the random tadpole shape of the classic Prince Rupert's drops and allow fabrication of the proposed initiator element to an optimized design via a reasonably repeatable process.

So, let's make a heavily stressed more or less rod shaped glass bead with a very narrow parabolic indentation in the far end from that which will be scratched, snapped or otherwise initiated. Load that parabolic cavity with very fine crystals of NON phlegmatized PETN, mannitol hexanitrate, etc. and point it into the next stage of the detonator.




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[*] posted on 26-12-2017 at 11:16


OK, I am eggnog free and the idea of a (cheap) simple mechanical replacent for the initial primary explosives in a firing train still is interesting.

I can find references to silica based glass with relative density as low as 2. Not yet linked that to specific mixtures, but Lithium oxide is claimed to make a good flux.



Question: Glass is a silica based mixture with various fluxes and modifiers, never intended to do what I'm thinking of here. So what other melts of elements, chemical compounds or blends could be encouraged to behave similarly? Hard, light, tough but not TOO tough, large coefficient of thermal expansion, cheap.

Next question, is glass/whatever with thermally induced stress the ideal stored energy system, or just the first one to pique my interest... The forest just got a lot bigger.

Attachment: Glass-Fluxes.pdf (128kB)
This file has been downloaded 91 times





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[*] posted on 26-12-2017 at 11:21


Would looking at very high temperature glass be the best start point? The glass used in multi fuel stoves might be a good candidate. Not sure what glass it is though.

https://www.ceramtec.com/perlucor/

Lye resistant!!! Ok thats off topic

I sent an email asking if Prince Rupert drops would be possible with this material, no idea what kind of reply i am going to get :D
Lets hope someone with a sense of adventure gets the email....

You never know, they might go Hmmm lets see.

[Edited on 26-12-2017 by NEMO-Chemistry]

[Edited on 26-12-2017 by NEMO-Chemistry]

[Edited on 26-12-2017 by NEMO-Chemistry]
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[*] posted on 26-12-2017 at 11:48


Fused quartz is well known for a low expansion coefficient.
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[*] posted on 26-12-2017 at 11:54


Quote: Originally posted by unionised  
Fused quartz is well known for a low expansion coefficient.

I will watch this thread with interest, but clearly its way over my head so I am bowing out of taking part.
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[*] posted on 26-12-2017 at 12:14


Hey, I did those public speaking exercises they make us do in USA high schools, around 40 years ago. One "information speech" was on glass technology- So my personal store of info is just a BIT dated.

Think we're all about equally disadvantaged here, jump on in, the Googling's fine.




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[*] posted on 26-12-2017 at 12:39


You have probably seen this, but wiki says the property is also found in Volcanic particles, it also mentions the university of Bristol doing research on it. I did a little google and it looks like they have done research from the volcanic perspective, BUT reading the University site it also appears they have a lab devoted to the properties of glass. Unless i have misread something, so i might have a look and see what research they have done, if its relevant to volcanic particles then there should be alot of information.

Wiki also gives some figures for speed of propagation, these are phenomenal. I might do some digging and send some emails, cant hurt to ask can it.

Also some direct research this year on PRD is here https://www.purdue.edu/newsroom/releases/2017/Q2/research-so...

It has an interesting paper and video

paper http://sci-hub.tw/10.1063/1.4971339

Video https://youtu.be/lt-zvsGvtqg

Cambridge University might be a better choice for me to email. Any idea of what kind of thing would be useful to ask?

EDIT]
I missed a link. One of the researchers has made information available on his google drive thingy

https://drive.google.com/drive/folders/0B5pvN1C9I3pbWnlKaUNC...


From a safety aspect, this is an interesting video, watch the bit leading upto 2:40 mins https://www.youtube.com/watch?v=dViDJti9eCA

They use a hydraulic press to sink a drop into a solid lead block, the guy tries to then break the drop by breaking the tail. The drop dosnt break.. I am not sure if it dosnt break because he fucks up the tail break, or if its because of being sunk in the lead block.

But it might have implications if you are putting it into a explosive.
At around 4:12 they dent a steel block and the drop goes off, a tiny fragment hits the go pro casing and breaks it! The bit that hit must have been tiny

[Edited on 26-12-2017 by NEMO-Chemistry]

[Edited on 26-12-2017 by NEMO-Chemistry]

[Edited on 26-12-2017 by NEMO-Chemistry]

[Edited on 26-12-2017 by NEMO-Chemistry]
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[*] posted on 27-12-2017 at 16:06


I think Bert's idea will work. In the youtube video NEMO Chemistry shows us, the steel block is dented. Perhaps we can also use wave shaping, and put a hollow hemisphere in the strained glass (at the business end), and load this with a secondary too.

I think this is something worth looking into. I am placing my bet on the side that this is feasible, and in a small package too, like a standard detonator tube. We don't need a lot of energy, just a good impulse. A minuscule amount of plastic or foil sets off PETN very well in slapper detonators.

We could also use a high power but common 2W blue laser to set off the strained glass. Add a dark pigment to the glass so it will absorb light, and have a fiber optic cable touching the sensitive end of the glass...

[Edited on 28-12-2017 by MineMan]
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[*] posted on 27-12-2017 at 17:12


The most interesting feature of the hydraulic press movie Nemo posted is that when the drop is pressed into the lead block, only part of the tail explodes, but not nearly as far as all the way to where it contacts the lead. Maybe the drops werent made properly. Alternatively, I was thinking maybe resonance is playing a big role here, the tadpole tail acting like sort of a horn.

[Edited on 28-12-2017 by nitro-genes]
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[*] posted on 27-12-2017 at 19:34


Quote: Originally posted by nitro-genes  
The most interesting feature of the hydraulic press movie Nemo posted is that when the drop is pressed into the lead block, only part of the tail explodes, but not nearly as far as all the way to where it contacts the lead. Maybe the drops werent made properly. Alternatively, I was thinking maybe resonance is playing a big role here, the tadpole tail acting like sort of a horn.

[Edited on 28-12-2017 by nitro-genes]


A interesting concept indeed....for some reason I tend to think that perhaps the intimate contact with a soft malleable metal like lead disrupts the propagation of the destructive wave in the glass to an extent where it no longer is able to break the material apart. The strain is mostly concentrated in the outermost top layers of the glass drop so it would make sense to think that if part of the energy is absorbed by something in intimate contact with the top layer of the glass, it might bring forth a situation where the destructive propagation of the wave stops altogether.




Exact science is a figment of imagination.......
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[*] posted on 27-12-2017 at 19:43


If you can put the drop in your hand and shatter it by breaking the tail, it will probably sting but is that going to be enough directed force as opposed to holding a hot primary or catching a speeding bullet in your hand? I'd like to see it work but something like tannerite seems like a Rupert drop among the prills just wouldn't get it.

"The King would have a subject hold the bulb end in the palm of the hand, and then break off the tip, giving the startled person a small explosion right there in a closed hand. It was harmless fun, though, as the glass shatters into powder, not into jagged shards."
https://www.cmog.org/article/prince-ruperts-drop-and-glass-s...

Perhaps a snapping shrimp? (It just came to mind as something fanciful albeit doubtful)
https://www.youtube.com/watch?v=ONQlTMUYCW4#t=1m5s

The snap of the bubble also produces something called sonoluminescence, i.e., emission of short bursts of light. When the cavitation bubble collapses it reaches temperatures of over 5000 Kelvin. That is almost as hot as the surface of the sun, estimated at around 5,800 Kelvin. This produces a flash of light which lasts for no longer than 10 nanoseconds and is not visible to the naked eye.
Watch the pistol shrimp’s snapping action in this fascinating BBC video.
https://learnodo-newtonic.com/pistol-shrimp-facts



[Edited on 28-12-2017 by Morgan]
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[*] posted on 27-12-2017 at 20:03


How about firing a drop inside a calorimeter. There is some information on rate, need to get a handle on quantity.

After New Year's , I hope to have time to melt some glass.

Thanks to all for the ideas and links. I've already learned things.




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[*] posted on 28-12-2017 at 02:54


I got alot more to post, but first some info, you cant change the shape of the top of the bead. In the paper i linked to it explains why, there is a 2013-2014 paper that has been found to be wrong.

The one i linked to is apparently the paper that explains the mystery of how the drops work and the forces involved. I didnt understand alot of it, but it does mention the shape being intrinsic to the way it works.

But when you read other papers on glass, it becomes clear you could attached another shape to it. But the drop itself has to be the shape it is. Velocity and forces are in some the papers I have seen, i will dig those out.

To give you an idea of speed of propagation, one the reasons it took 400 years to fully understand the things, was the fact that they didnt have ultra fast cameras to look at it.

Large drops pack a punch, yes they shatter harmlessly in your hand, until you scale up to around 6-7cm. Apparently at that size you get some force in it. All of this is a mix of info from 15 papers I have read so far.

I am reading stuff to find the most relevant, i will post those in references i guess. NON soda test tube glass is scary!! I used map gas to melt a bead and tried it, use glasses with that stuff!

In the video as i mentioned above, a tiny bit of the glass hit the perspex progo camera cover and broke it. Watch it really carefully again, the glass fragment is tiny! Non soda glass is like soda on steroids and TBH i didnt want to do too many! When they shatter in a gloved hand you feel it, it kinda stings a fair bit.

I found quickly melted glass to work best, i think this is so you dont soften the glass to the point its normal glass. just guessing but maybe doing that leaves part of the glass already under stress, but again, seriously make sure you got decent face protection!

I will post other stuff once I finished my distillations!! I have heating issues!
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[*] posted on 28-12-2017 at 06:57


That would be interesting to see and hear a 7 cm Prince Rupert's Drop go off. It brings to mind those heavy "Pyrex" dishes that sometimes bomb shatter if heated and a few drops of water placed on them or performed by setting them on a wet surface. There's a lot of sound produced in ideal conditions. Once I microwaved a cereal bowl that wasn't microwave proof just for a short time thinking it would be OK, but when it shattered the sound it produced was stunning.

Those Bologna bottles that are stressed like the Rupert drop, could a secondary be triggered in those somehow?
https://www.youtube.com/watch?v=DAmNmWpxo8Q
https://www.youtube.com/watch?v=rdcss3Sx6xk
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[*] posted on 28-12-2017 at 08:26


Quote: Originally posted by markx  
Quote: Originally posted by nitro-genes  
The most interesting feature of the hydraulic press movie Nemo posted is that when the drop is pressed into the lead block, only part of the tail explodes, but not nearly as far as all the way to where it contacts the lead. Maybe the drops werent made properly. Alternatively, I was thinking maybe resonance is playing a big role here, the tadpole tail acting like sort of a horn.

[Edited on 28-12-2017 by nitro-genes]


A interesting concept indeed....for some reason I tend to think that perhaps the intimate contact with a soft malleable metal like lead disrupts the propagation of the destructive wave in the glass to an extent where it no longer is able to break the material apart. The strain is mostly concentrated in the outermost top layers of the glass drop so it would make sense to think that if part of the energy is absorbed by something in intimate contact with the top layer of the glass, it might bring forth a situation where the destructive propagation of the wave stops altogether.


Exactly what I was thinking first! Later in the video posted on youtube the guy snaps the tail of one of these drops which is only partly embedded in the lead. I was very surprised to see that no propagation seemed to happen at all, he almost cleanly broke off the tail. Wouldn't this be hard to explain taking only a moving front of fracture propagation into account? (given that the drops were properly made)
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[*] posted on 28-12-2017 at 10:21


A 7 cm drop?! You mean just the length of the head? I assume the viscosity of the melt would determine what size drops can easily be made, so perhaps less flux?
.

I am seeing references to cold water being desirable to speed the quench in order to create more stress and wondering about the tradeoff between possibly slower cooling of the skin due to the lowered heat capacity/volume of a water/glycol mix and the lower temperatures possible from a sub 0 C. liquid for quenching. Something to try, it is well below 0 F. here right now.

Prince Rupert was an interesting character. May have invented one of the mezzotint processes, he originated the hand tool still used to punch the matrix of dots into the Copper printing plate for the dark to light process. Said to have come up with the idea by looking at dark oxide trapped in rust pits on a sentry's musket barrel while the soldier was trying to polish the rust dammage away- Pity his uncle was such an inadequate king, the English civil war certainly put a crimp in the prince's many intellectual and artistic endeavours.

Yes, learning things...




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[*] posted on 28-12-2017 at 10:40


I suppose the experiment would be to make a fairly sensitive secondary, melt some glass into a bucket of water and see what happens.

What would constitute a "fairly sensitive secondary" ?




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[*] posted on 28-12-2017 at 12:05


Unphlegmatized fine PETN or mannitol hexanitrate come to mind. Possibly also very fine particles of RDX from air spraying fine droplets of RDX dissolved in acetone into rapidly stirred water, there are patents on tuning up sensitivity through smaller particle size.

A while back, I had to break a bunch of light bulbs on a theatre marque sign for a video project. I used commercial electric matches with 15mg of 80:20 Mercury fulminate : Potassium chlorate introduced into to the plastic safety shroud on each match and a scrap of tape to hold it in, these were super glued to glass envelope of each bulb just above the metal threaded base. Absolute minimum charge to reliably break the glass.

I had some of the "enhanced" electric matches left over after doing the job, and wondered if they would set off a commercial Tannerite target. Answer: yes, 3 out of 3 fired from that tiny charge. Not much power there, the tiny pinch of composition would only split the plastic shrouds open for about 1/4" at the end, the plastic bits didn't even detach.







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