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Author: Subject: Possible? Initiation of primaries by shocks through secondaries
IndependentBoffin
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[*] posted on 22-6-2011 at 04:25
Possible? Initiation of primaries by shocks through secondaries


Hi folks,

Do you think it is possible to initiate a primary explosive by a shock travelling through a secondary explosive?

Referring to the attached diagram:
1) The initiator explosive on the LHS goes off.

2) A shock wave travels through an inert material and through a block of secondary explosive. The strength/quantity of initiator explosive should be low enough to not cause initiation of the secondary explosive.

3) The primary explosive on the RHS is initiated by being shock compressed against the hard anvil layer.

4) The RHS primary explosive, in intimate contact with the secondary explosive, initiates it.

This device essentially converts a very weak LHS -> RHS shock into a very strong RHS -> LHS shock.

The trick will be to balance sensitivities, so that the secondary explosive never goes off by passage of the first LHS -> RHS shock, but always goes off by passage of the second RHS -> LHS shock.

I was thinking about silver acetylide for the LHS primary and nitrogen triiodide for the RHS primary.

explosive_laminate_idea.jpg - 23kB

[Edited on 22-6-2011 by IndependentBoffin]




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Bot0nist
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[*] posted on 22-6-2011 at 04:55


Nitrogen triiodide? Maybe an organic peroxide even, but nitrogen triodide would be nearly impossible to work with I would think.



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IndependentBoffin
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[*] posted on 22-6-2011 at 05:02


Quote: Originally posted by Bot0nist  
Nitrogen triiodide? Maybe an organic peroxide even, but nitrogen triodide would be nearly impossible to work with I would think.


Well, in a laboratory setting (just for proof of concept), you can perfectly isolate the system from external vibrations and shocks by mounting it on a vibration isolation platform.

Being a contact explosive, you can pretty much guarantee it will go off when even a very minor shock reaches it from the LHS initiator.

With organic peroxides some trial and error may be needed to establish the right quantity of initiator explosives to set them off every time, an never prematurely setting off the secondary explosive.




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2) Alkex para-aramid Korean Kevlar analogue fabric (about 50% Du Pont's prices)
3) NdFeB magnets
4) High purity technical ceramics
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PHILOU Zrealone
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[*] posted on 22-6-2011 at 05:12


Must be possible, but not with NH3.NI3 (would explode before or at the same time of the initial shock!

Your design let me think to some kind of landmines or to anti-armourpiercing system...

Your design must be possible with the very same initiator on the right and on the left...the important variable are:
-the inert material gap between the inital initiator and the secondary explosive (L)
-the secondary explosive (C)
-the initiating explosive (A and A')
-the inert material (B)

This gap must be defined by the gap sensitivity test of the secondary explosive (C) towards the initiator explosive (A).
Supposing that A can detonate C; it is the lenght (L) of inert material (B) at wich no more detonation of initiating stuff (A) allows inflamation, explosion or detonation of secondary explosive (C).

So:
-the higher the sensitivity of C; the longer L must be.
-the higher the power (or the amount) of A, the longer L must be.

The charge C may deform under the first detonation...this deformation must push/hit/crush the second detonator (A') strongly enough to get it to detonate.
If there is no gap between this second detonator (A') and C; then C will detonate.

Beware of the casing if it is not made of the very same material as the inert material...external casing may then propagate shock wave from A into C bypassing B.

If it is made of the same material there should be no problem.


[Edited on 22-6-2011 by PHILOU Zrealone]




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IndependentBoffin
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[*] posted on 22-6-2011 at 06:21


Quote: Originally posted by PHILOU Zrealone  
Must be possible, but not with NH3.NI3 (would explode before or at the same time of the initial shock!

Your design let me think to some kind of landmines or to anti-armourpiercing system...


Let's focus on the chemistry and physics of it :)...if it gets too weapons related the thread may be locked :(

Quote:

Your design must be possible with the very same initiator on the right and on the left...the important variable are:
-the inert material gap between the inital initiator and the secondary explosive (L)
-the secondary explosive (C)
-the initiating explosive (A and A')
-the inert material (B)

This gap must be defined by the gap sensitivity test of the secondary explosive (C) towards the initiator explosive (A).
Supposing that A can detonate C; it is the lenght (L) of inert material (B) at wich no more detonation of initiating stuff (A) allows inflamation, explosion or detonation of secondary explosive (C).

So:
-the higher the sensitivity of C; the longer L must be.
-the higher the power (or the amount) of A, the longer L must be.

The charge C may deform under the first detonation...this deformation must push/hit/crush the second detonator (A') strongly enough to get it to detonate.
If there is no gap between this second detonator (A') and C; then C will detonate.


Yes I understand your points :)

Do you have any references where I can find a comprehensive review of the shock sensitivity of many primary and secondary explosives?

Quote:

Beware of the casing if it is not made of the very same material as the inert material...external casing may then propagate shock wave from A into C bypassing B.

If it is made of the same material there should be no problem.


Having a casing interfering with the shock propagation can be engineered out. Just have one with a low shock propagation velocity or make it of the same material as the inert material.

Also the only* way longitudinal shock stresses in the casing can transfer to the explosive material within the casing is by shear stresses. Therefore if a near-zero shear stiffness material (e.g. petroleum jelly) is present between the explosive and the casing, and the explosive isn't bonded or cast into the casing, it can't be initiated by shocks travelling through the casing.

*Edit: Actually another possible way is that because most casing materials have a positive Poisson's ratio, there is a coupling between longitudinal shocks and radial expansion. But this can be compensated for by putting foam (e.g. expanded polystyrene) between the casing and explosives. Zero Poisson ratio materials are also possible with composites.

[Edited on 22-6-2011 by IndependentBoffin]




I can sell the following:
1) Various high purity non-ferrous metals - Ni, Co, Ta, Zr, Mo, Ti, Nb.
2) Alkex para-aramid Korean Kevlar analogue fabric (about 50% Du Pont's prices)
3) NdFeB magnets
4) High purity technical ceramics
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PHILOU Zrealone
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[*] posted on 22-6-2011 at 07:29


I think if you search with the following keywords, you will find valuable info:
-NOL Card Gap
-EIDS Gap
-UN Gap
-explosive shock sensitivity determined from large scale gap test (LSGT).

Rudolf Meyer -Explosives 4th edition has also info on the test and some values for some explosives.




PH Z (PHILOU Zrealone)

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