Sciencemadness Discussion Board

Safer Charge Designs

SB15 - 31-12-2010 at 11:44

Recently, I've been attempting to develop a HE charge design that eliminates the risk of the base charge detonating during handling, and also requires no on-site assembly. Here's a crude MS Paint diagram of what I've been testing over the past few days.



Essentially, the cap is held in place above the main charge, while the fuse is under tension from a light compression spring. Once the fuse burns through the glue joint, the tension is released and the spring extends, propelling the cap down the tube and into the ETN base charge, where it detonates a couple seconds later. This has proved reliable in the 3 tests I've conducted thus far.

A device was also tested with the spring removed and the cap glued in place at the top of the tube. The detonation of the 0.2g HMTD cap was only able to burst the upper section of the casing, with no damage to adjacent surfaces. Excellent. I believe this adds a whole new dimension of safety to my HE experimentation.

Thoughts and suggestions are appreciated.

hissingnoise - 31-12-2010 at 12:26

Quote:
Excellent. I believe this adds a whole new dimension of safety to my HE experimentation.

It looks good, but . . .
Overconfidence - especially when using any organic peroxide is fraught with danger!
A less sensitive primary would lessen your chances of doing yourself serious damage, or worse!

SB15 - 31-12-2010 at 12:39

I wasn't implying that this is completely safe, just that it's significantly less hazardous than pressing the primary directly on top of the base charge, then manually inserting the cap into the main casing.

Obviously a safer primary would be beneficial, HMTD is just an example.

hissingnoise - 31-12-2010 at 12:51

I wouldn't feel too safe with a spring acting on the cap as I handle the charge!
I'd be inclined to let gravity unite base charge and initiator . . .



crazedguy - 1-1-2011 at 13:25

Quote: Originally posted by hissingnoise  
I wouldn't feel too safe with a spring acting on the cap as I handle the charge!
I'd be inclined to let gravity unite base charge and initiator . . .


That is exactly what I thought seems like using the fuse to suspend it would be much easier/safer.

Microtek - 1-1-2011 at 15:20

I think it's a rather impractical idea. I'm sure it will make it a little less likely that you will be killed by a premature blast, but it may make it a little more likely that you will lose some fingers due to increased handling of the peroxide charge.

I've said this numerous times before: The home experimenters first step should be to source or synthesize nitrite. Once you have that it is easy to make a good dependable primary that is superior to organic peroxides in just about every way.
There are many ways to obtain nitrite even if you can't just buy it. Search through inorganic chemistry texts, patents and the internet and you will get many many hits.
With appropriately tuned azo-chlathrates or the right nitrotetrazolate adducts, you have a primary with sensitivity comparable to that of RDX, making handling of the cap a non-issue.

mabuse_ - 2-1-2011 at 09:58

The whole construction looks simple, but i bet it's not very easy to build robust and reliable enough.

This guy got the same idea:
http://www.youtube.com/watch?v=nMil37G1F2Q


I like the idea to seperate the primary explosive and the booster of a blasting cap. 200mg Lead azide oder Silver Carbide sure whould hurt, but the same amount plus 1g of PETN oder ETN going off at the workbench...

Is there a reason why obviously nobody in the hobby blasting szene is attempting such a thing?

[Edited on 2-1-2011 by mabuse_]

[Edited on 2-1-2011 by mabuse_]

Microtek - 2-1-2011 at 14:31

Oh, I've experimented with that sort of thing in the past (separating primary and base charge). The most practical way I found was to simply make a standard cap with only base charge and a smaller cap with primary that fits into the base charge cap. This works just fine, but then I shifted my focus to finding less sensitive primary explosives. When the primary is less sensitive than the base charge there is just no good reason to complicate things by making them separate.

Lord Emrone - 3-1-2011 at 06:13

Quote: Originally posted by mabuse_  

Is there a reason why obviously nobody in the hobby blasting szene is attempting such a thing?

I bet , because it's too time consuming to build.

@SB15 : since you allready use ETN, why not just heat-det it ? No primary needed. You could as well use a small PVC-pipe and let gravity do the job.

@crazedguy : how were you tests ?

Jimbo Jones - 3-1-2011 at 10:35

Quote: Originally posted by Lord Emrone  
Quote: Originally posted by mabuse_  

Is there a reason why obviously nobody in the hobby blasting szene is attempting such a thing?

I bet , because it's too time consuming to build.

@SB15 : since you allready use ETN, why not just heat-det it ? No primary needed. You could as well use a small PVC-pipe and let gravity do the job.

@crazedguy : how were you tests ?



In the past I have tried to initiate some ETN based caps with fast thermite, but they all fail to detonate, even in bigger diameters. The thermite was based on “painted” with acetone & NC & flake aluminum powder Teflon tape. This thing is extremely fast, almost as flash powder, so in confined spaces….how knows. It’s somewhat difficult for ignition, but even a Visco will do the trick if the tape thermite is rolled around the fuse. After 3 tests, I just abandoned the idea.

But…..a nice thought popped in my mind before some months. This Teflon thermite is superior to the thermobaric aluminum foil & Teflon tape combo. The patent is already on the forum, but I’m too lazy to put the link to it. The whole idea is good, but I hardly doubt that the oxide layer on the aluminum surface will allow some reaction with the Teflon. On other hand the Teflon tape & aluminum “paint” thermite is very reactive and will disperse and combust in seconds. Hmm….a micro, thermobaric charge….

Lord Emrone - 4-1-2011 at 04:24

@Jimbo: you're making it far too difficult. Just wrap the ETN mixed with some al powder in 5 layers al-foil and heat with something that burns for a while.

Cuauhtemoc - 4-1-2011 at 06:30

I'm sorry but that look dangerous, if your design contain any flaws, especially with the spring, it can go off.
Let's say the hmtd gets dropped without using the fuse, the impact may set it off and you are dead.
Also, considering it's somewhat "complex" you may be tempted to build it and only use it later, and organic peroxides should be used ASAP

mabuse_ - 4-1-2011 at 13:02

Quote:

When the primary is less sensitive than the base charge there is just no good reason to complicate things by making them separate.


How can a primary be less sensitive than the base charge?
I mean, you have to start the reaction somehow?

quicksilver - 4-1-2011 at 14:00

If you truly have an interest in this issue it would be extremely important to learn detonation modeling which is not a lightweight element of physics and chemistry.
Detonation is one of the most interesting subjects in energetics. True detonation takes place where the molecule breaks apart via a variety of stimulus. What is typically used is a mathematical model of the molecule in order to compartmentalize the phenomenon.
True detonation differs from other forms of combustion in that all the important energy transfer is by mass flow in [strong] compression waves {Fickett 1979} with negligible contributions from other processes like heat conduction. Experiments (Los Alamos) have shown that these waves have a complex transverse structure & have puzzled scientists by yielding some results that are at odds with theoretical predictions. Therefore the need for mathematical modeling.
Pioneers in that field have been; Zeidovich, von Neumann, & Doering who independently formulated treatments of detonation. This is a very exciting subject as it deals with molecular structure; both in building and breaking down [& in that course creating energy].
The independent science in the case of a single irreversible (forward only)reaction of thermicity (the conversion of chemical bond energy to macroscopic transitional energy) are known as the "Simple Model" (or Simple Theory). Study and comprehension must make use of the "reaction zone" & "final state" to compartmentalize the existing understanding of the elements of detonation.

Application of stimulus alone may or may NOT complete this transition. Such transitions are often referred to as the detonation velocity, final flow, following flow, transition zone, etc. Unsupported case, overdriven cases & boundary conditions all contribute to understanding what and how detonation takes it's form (& of course what defines it's elements in study or model).

I have begun to understand the "Simple Theory"of modeling which in turn leads to a more complete understanding of what actually takes place when a molecule breaks & provides energy within this phenomenon. This is (to me) one of the most interesting subjects within energetic science.


Edit:
It can be said that in modeling; impact can be heat as can MOST other formats of initiation. The form is almost immaterial so long as it meets criteria that provide for a breakdown of the molecule. It's control in transition is what is experienced as a true detonation. We confine this by numeric conditions for elimination of combustion as a transitional state in slower molecular alterations & to have a utility such as Pi or gravity.

[Edited on 4-1-2011 by quicksilver]

Microtek - 5-1-2011 at 11:04
Quote:

How can a primary be less sensitive than the base charge?


Less sensitive to everything except flame. Azo-chlathrate can be "tuned" by adjusting the amount of azide in the structure to be quite insensitive to stimuli such as impact, friction, electrostatic discharge, etc., but still be very responsive to direct flame contact. Much the same thing can probably be done with some nitrotetrazolate salts (I say "probably" because I haven't explored these salts fully, but my preliminary experiments suggest that it is so).

gnitseretni - 5-1-2011 at 12:23

Quote: Originally posted by Microtek  
The home experimenters first step should be to source or synthesize nitrite. Once you have that it is easy to make a good dependable primary


You keep mentioning azo-clathrates, but they don't call for nitrite. So which primaries are you referring to that are so "easy" to make?

Microtek - 6-1-2011 at 02:35

Well, to make azo-chlathrate you azide. To make azide in the amateur lab, the reaction of organic nitrite with hydrazine is by far the easiest IMO. And to make an organic nitrite the easiest way is to react an appropriate alcohol with nitrous acid generated in situ by means of inorganic nitrite and eg. sulfuric acid.

Mind you, for a long time I didn't have access to inorganic nitrite, so I produced iso-propyl nitrite by heating a mix of 60 % nitric acid and starch to produce NOx. This was then led into a washing flask with iso-propanol and the produced iPr-ONO (which evaporated from the heat of reaction as well as the heat supplied by the hot NOx) was led into an ice water bath along with excess NOx. The iPr-ONO condensed and separated on the surface while the NOx mostly escaped (some was absorbed in the water to make dilute HNO3/HNO2).
This works just fine, but it is cumbersome.

You also need nitrite for aminotetrazole and for the conversion of ATz to nitrotetrazole and also for tetrazene and DDNP (some of these could likely be made by other means but this usually entails reagents or procedures that are so difficult to obtain/carry out that simply producing your own nitrite is much easier).

quicksilver - 6-1-2011 at 13:34

Getting a bit off topic for a moment....
Quite some years back I had a synthesis for tetrazene from aminogunadine from guanadine nitrate That is certainly in this forum. IIRC Roscoe had a hydrazine synthesis as well.
There is SO much material here that I really hesitate to start going into notebooks, textbooks, and archives for things that I KNOW are in this Forum.

However nitrites are available as a meat preservative in USP grade.

Getting back on topic; Microtec makes a valuable point in that all of this is possible IF you do your homework and have some glassware.

Microtek - 6-1-2011 at 14:25

Legislation differs wildly in some areas; in my country inorganic nitrite is labeled as a toxin and requires a certificate that testifies that you have a suitably equipped lab to handle it. I tried ordering some through my family's company at one point and got a call from the firm where they requested that I fax the certificate to them.

mabuse_ - 7-1-2011 at 14:24

Well, I've got the ingredients for lead azide und my last experiments with it were very succesful.
Never again HMTD - a great leap forward for me.


I've just read about these azo-clathrates for the first time.
My problem whould be getting picric acid. I just can't get phenol, maybe the aspirin route is an option...

If this stuff keeps the promises that where made here, why hasn't it become the standard primary in commercial blasting caps?
As far as i know the top choice is still lead azide/lead styphnate?