Baseline Tests

[dbooksta]

We need a suite of benchmark tests that can be setup by amateur chemists to determine the performance of explosives. You may see an explosion, but was it a detonation or just deflagration? How efficient was the reaction?

Rather than just confirming which chemicals go BOOM, and how, I would like to compare the maximum effects people are observing with specific compounds, densities, and detonators. If we build a common baseline of observations we can all draw more useful conclusions from our experiments.

I am not experienced enough to propose a set of benchmarks that would be useful for all explosives we contemplate here, but trying to create testbeds that would be widely accessible I would throw out the following ideas:

1. Plate Denting Test -- Rest charge on plate and detonate to see how big a hole it makes. Suggest using 1" MDF resting on 2x4's on 4 corners, instead of the traditional metal plate?

2. Rodman Penetration Test -- Explosive-backed piston drives hardened penetrator into soft target to see how far it goes. Suggest using 3 layers of 2x12 softwood against four 1/2" spikes resting on hard ground.

3. Ballistic Mortar Test -- Charge mounted under heavy projectile to see how high it blows. Not sure the best way to run this.

4. Ballistic Pendulum Test -- See how far charge can push a heavy weight with plugged lateral hole. Supposedly best measure of "heave." Is this one useful in the context of the others?

5. Fragmentation Test -- See how many / how small pieces are created by the confined charge. Suggest putting 1" schedule 40 steel pipe in 5 gallon bucket of water to trap fragments.

6. Hess/Trauzl Lead Block Compression/Expansion Tests. Not sure how easy it would be to find consistent and appropriate lead specimens. Besides, Trauzl is known to be inappropriate for aluminized compounds.

If people start posting results in terms of such standardized tests we can learn just how good our chemistry and devices are.

[Kleng]

Very hard to do these kind of test. You can surely run them for your own, because you then use the same metal for all your metal plates, the same pressure for pressing the charge, and you use the same detonator. Remember, small differences in the charge, can make a big difference in the result. Just think of how you place the charge upon the softwood.

If this test is to be run, we all need to use exactly the same things. Of course, if you can make a test of a explosive were all these things are included, you've done very well.

I guess I can also take part in such a test. Anyway, film it is very important.

[sirthomasthegreat]

I would suggest that a earth test be done. Dig a 1' deep hole, plant charge and cover it. Measure depth and width of crater. However shaping the charge would give different effects. So benchmarking a charge isn't a good idea but benchmarking the explosion velocities of the materials would be good.

A good demolitionist usually never uses the same charge more that once as the situation and need changes. For example you wouldn't use a coffee pot charge to take down a door but it makes an excellent road charge.

++++++++=

And how variable is dirt around the world, or even five feet over from your last test hole? NBK

[dbooksta]

Right, we should start with ways of benchmarking just the explosives and basic detonators, without getting into nuances of charge geometry. I imagine most of us beginners are more concerned with confirming efficient detonation before moving to specific applications.

One variable of interest will certainly be the detonators.

The other variable being the explosive should be easy to standardize based on weight and volume.

To simplify matters we could stick to tests with charges in 1" and 2" diameter PVC or steel pipe, which we can find at any hardware store.

So someone may come back and say: "I packed 100 grams of 95/5 Ammonal into 2" length of 1"-diameter PVC -- i.e., 4g/cc density. I shot it with a 150gr .308 FMJ bullet (chronographed 3000fps) and got an explosion. It was sitting vertically on 1" thick elevated MDF and left a clean 4" hole. Here's a video."

Now, if someone else comes back and says, "I detonated the same charge with a #6 cap and got a 12" hole in the MDF" then we know the bullet didn't give a complete detonation, or else there was something wrong with the chemicals.

As Kleng noted, getting metal plates is hard enough -- much less standardized ones we could share. That's why I was suggesting we try MDF -- which should be both very uniform and widely available -- for a plate test.

The crater test would be a good measure of heave if standardized earth were used -- say, dry 30-mesh sand (again easy to acquire).

[sirthomasthegreat]

NBK you raise a very good point. A standard must be set. However it is very hard to standardize everything over the internet. So we must determine standards. I would say that we use ratio standards, like energy (in joules) per gram and the like. So you could easily decide that a certain type is better for your application than the other because they give the same amount of Punch, but you need 1kg of one and 30g of the other. You will also need to create standards for each type of device. For example you wouldn't want to do a crater test on thermite. I don't know. All I'm saying is that a lot, and I mean a lot needs to be determined before we start standardizing. I also suggest that one person does the standardizing as you and I may have different techniques for making and detonating.

[TreverSlyFox]

Maybe I'm missing something here, but exactly what is going to be accomplished with these "Standardized Standards" of testing? None of the explosives we "Imagine" to make have the same source of chemicals, except maybe for AP.

Since many of the chemicals we use are extracted from OTC sources there is no "Quality Control" of the chemicals themselves. Since we aren't using the same source and quality each makers product will be a little different so there is no way to reproduce what one testing source finds to be good. Nor may two different "batches" by the same maker test out the same.

Since your talking about a testing procedure that will take some time and effort to standardize and produce. With all the "unknowns" will the information gained be useful in a direct way that makes the project worth the effort?

[sirthomasthegreat]

Don't quote whole posts! NBK

My point exactly. It would be too hard. I have acces to labratory grade chemicals and could possibly standarize with the best of the best. Soon here I am probably going to try some TACN and thermite.

[Chris The Great]

The tests would give a good benchmark on what one can expect from such improvised explosives, vs a commercial product. This could also tell you exactly how powerful whatever you made is in real life, and not just in a book. Somebody just needs to make a batch of military grade TNT (not an involved task if one has the proper equipment and chemicals) for the benchmark, and then fire it for each of the tests 3-5 times to get a good result.

While we couldn't remove ALL error from the tests, and those performing them would need to invest some time and effort to ensure that they are standardized, I'm sure we could get quite close if we're careful with exactly what is used for the test "target" (whatever it may be) and the detonators. Fragmentation tests, mortar tests and sand tests could easily be done by amatuers, plate tests would be a bit more complicated as thick metal plates of consistant quality are usually not available to us.

And besides, if you read a procedure for a new mixture or unexplored explosive and right there was "sand test: 85% TNT, mortar test: 110% TNT" you'd have a FAR better idea of the capability than just some educated guess (educated it may be, but it is still a guess).

I'll think about it a bit and possibly have some better ideas on how this could be practical.

[nbk2000]

I would assume that properly purified OTC explosives made by different people around the world, would be close enough in performance that any variation would disappear into the error margin of the testing equipment the typical Forumite could make.

If you have access to streak cameras and FO break timers, than yeah, explosive purity to 99.999% would matter, but not with a lead plate made from tire weights.

[dbooksta]

Exactly -- as an amateur I'd be happy with measures that are only accurate to two significant figures, just so I have an idea when something goes BOOM whether it achieved a detonation (instead of deflagration), and whether the reaction was efficient and complete. Moreover before a first test one might have some idea of the expected performance (and required safety measures).

The ideal would be if, as Chris suggests, somebody with TNT and industrial detonators runs the same tests and gives us TNT benchmarks. Then anyone who has used the tests can readily compare against all of the academic and commercial literature.

(Note also that if chemical purity is a big consideration in performance then this would also be a good way of discovering that.)

[nbk2000]

One thing I've often noticed is people experimenting with small charges of an explosive, and then asking whether or not the resulting hole in the ground was from a full or partial detonation of the main charge, or the result of the detonator alone.

Well...if you make two identical charges, one using the live HE, and another with a similar detonator, but loaded with an inert simulant instead of HE, then a simple comparison of the two results would reveal if the live charge was a complete/partial/dud. :)

For liquid HE simulants, water or antifreeze comes to mind. Solids would have to simulate the physical properties and density to be adequate substitutes.

[Microtek]

I think that we should agree on some easily made, widely available benchmarking compound such as well washed EGDN. Then each tester chooses a set of tests, for instance a plate dent test for brisance and a Trauzl test for power. EGDN is then run through each of these tests to give a certain figure which is then that testers benchmark. When that tester then produces another explosive, he can run it through the same tests to give a value relative to EGDN. This way, the tests do not need to be identical from one tester to the next, only the EGDN does.

The trick would be to decide on an explosive that every serious experimenter could make in adequate purity. Also, the benchmark explosive would need to be tested at the same density from tester to tester which would favour liquid explosives.

[nbk2000]

Liquid explosives have merit for uniformity of density and cross-section, but then you have the matter of isomers and various states of nitration.

NG has mono/di/tri-nitro state, and EGDN can be a mono-nitrate.

I'd go with PLX, or other NM-based liquid explosive.

Almost everyone can buy nitromethane as R/C fuel and purify it by steam distillation, or synth it in small quantities. Sensitizer could be Picric Acid, as that's easily made in sufficient purity.

[Kleng]

Some sort of Nitromethane explosive could be tried, but also an explosive that is so common.

Think about a nitrated sugar like Erythritol Tetranitrate, Xyliton Pentanitrate or Sorbitol Hexanitrate? All of these sugars are possible to obtain for everyone, and the synthesis of the explosive isn't that hard.

[dbooksta]

Some nutjob tried #2 from my initial suggestions using 25 grams of 70/30 KClO4/Al flash powder, and the video shows this may not be very effective (http://s188.photobucket.com/albums/z209/dbooksta/?action=view&current=Flash.flv):

- The MDF on top was unharmed (but for blast marks).
- The two 2x12 softwood layers underneath fractured along their grain -- apparently the MDF is flexible enough to transmit a shockwave without breaking itself.
- The platform was driven only a few millimeters onto the 3/8" spikes on which it was set.

But at least it was tried...

[dbooksta]

These may not be good for baselining, but if the question is just whether an explosion was detonation or deflagration I came across two good tests while re-reading the classics:

1. Microtek suggests packing the explosive into a loop of hose, igniting one end, and looking for a larger impact at the opposite end where the wavefronts would collide if it were detonating (http://www.roguesci.org/theforum/showpost.php?p=6676&postcount=60).

2. Others suggested just firing the sample on top of rocks or concrete. LE's can definitely crack rocks, but detonating HE should shatter/pulverize it. Hopefully the difference will be obvious; I'll see if I can track down and share some experimental results.

[nbk2000]

What you saw in your flash experiment is the effect of a low explosive, in that it pushes, rather than shatters, like high explosives do.

[Guerilla]

dbooksta, KClO4/Al as such is known not to detonate but seemingly a shock front in the gas phase can form, provided the aluminium particles are fine and reactive enough to ignite from the heat generated by the rapid compression of air. The propagation velocity is roughly 1000m/s anyway, which is in the range typical for fuel-air explosions. This would also explain why flash explodes more violently when loosely packed. It would be interesting to fire some charges under vacuum to see how they would compare..

In any case the peak pressures are so small that I doubt one would get readable results in those tests with flash. Anyways I like this idea of creating some sort of own measuring standards among RS members. Maybe we can gather a small group for a few simple lead block tests soon, just to see how close we can get to each others' figures..