Sciencemadness Discussion Board

RE Factor for different stuff

testimento - 8-7-2013 at 03:43

In wiki there is nice list for relative effectiveness factor for different kind of explosive materials and compositions.

https://en.wikipedia.org/wiki/Relative_effectiveness_factor

The list is in constant change.

My first questions is what are the RE factors for chlorate based compositions, like KClO3 + Al, KClO4 + Al, NH4ClO4 + Al, etc? Which one is more powerful, chlorate or perchlorate?

AndersHoveland - 8-7-2013 at 23:12

Quote: Originally posted by testimento  
Which one is more powerful, chlorate or perchlorate?

Obviously perchlorate compositions would release more energy, but as to whether it would have a higher detonation velocity, I do not know. Chlorate has a lower temperature of decomposition, so the reaction rate might be faster. How this would affect the propagation of the shock front, is more complicated.

Surely though, if it was a cheddite-type composition, containing some other explosive like TNT to propagate the detonation, the perchlorate would have to win out due to its higher energy content.

Whether flash powder can actually detonate is a complicated topic (which we are not going to go into), but the equivalent detonation velocity is much lower (below 1500-2000 m/s), so that is a big factor here. In the explosion of NH4ClO4 with Al, the propagation of the shock front would be almost entirely dependent on the detonation of NH4ClO4. The combustion of the Al powder would only be secondary.

doing a quick internet search, one source lists the R.E. for flash powder as .75 to .80

Do not forget that these are not really "high explosives", the reaction rates are significantly slower. I doubt they would be very effective in actually causing structural damage of hard targets.


[Edited on 9-7-2013 by AndersHoveland]

Fantasma4500 - 9-7-2013 at 01:34

indeed they wouldnt, theyre not brisant enough, a case in norway where some men were making rockets in a basement (in which is illegal in norway for some reason) it ignited
when the police arrived they saw that the basement was moved what... 5 cm from where it originally was?
they were quick to say it was dynamite
but
dynamite is far too brisant to PUSH, it would just crush the whole thing

i really think the RE factor is complete bullshit, nobody knows WHAT RE is, how they calculate it.. i mean who knows, a general which has nostalgia with a certain compound might even be part of the RE, perhaps something that doesnt matter to the actual properties but rather handling it, water resistance etc.
if you want some good info on HE's you need to find the brisance of it, gas expansion means alot also..
ammonium nitrate based binaries are good for removing buildings, while more brisant compounds like PETN and RDX would be better for blowing holes in metal or whatever, but would be much more expensive than to use AN based secondaries if you were to remove a house

anyways what would you get from having the RE factor of FP?

bfesser - 9-7-2013 at 06:42

<strong>Antiswat</strong>, I don't 'do' energetic materials, but even I can say "Don't be daft!"
<a href="http://en.wikipedia.org/wiki/Relative_effectiveness_factor" target="_blank">
Quote:
<strong>Relative effectiveness factor</strong> or <strong>R.E. factor</strong> is a measurement of an explosive's power for military demolitions purposes. It is used to compare an explosive's effectiveness relative to TNT by weight only, TNT equivalent/kg (TNTe/kg). This enables engineers to substitute one explosive for another when they are calculating blasting equations that are designed for TNT. For example, if a timber cutting charge requires 1 kg of TNT to work, it would take 0.42 kg of ONC, 0.6 kg of PETN, 1.25 kg of ANFO, or 2.22 kg of AN to have the same effect.
&hellip;
The bigger the R.E. number, the more powerful the explosive.<img src="../scipics/_wiki.png" />
</a>

Ral123 - 9-7-2013 at 07:25

On that logic anfo (http://www.youtube.com/watch?v=IPAXdgduFkQ)
is almost infinitely weaker then plastic explosive(http://www.youtube.com/watch?v=pg81-8y1FQE)
But I guess there are algorithms that can give you some data (pressures at range and other) based on that R.E. value.

testimento - 9-7-2013 at 19:07

I've played with flash powder and pyrotechnic compositions and I can say that 20 grams of KClO4+Al 70:30 will blow 20-liter paint can 20 meters up in air and deform the bottom a perfect round. But it wont rip steel, no doubt of that.

From knowing anything about the facts behind it, I could speculate that the possible RE factor of FP could come from thermobaric effect more than brisance. Brisance doesnt seem to have RE factor - like classification at all, but if The good ol' TNT would be classified as 10, PETN could be like 25-30, AN compounds at 5 and flash powder maybe somewhere 1.5-2. I've witnessed explosions from high brisance stuff and then flash powder an APAL (A.Perc.), and the brisant stuff just went off in a single hard-tack BANG, the flash powders were more like BUM and the APAL was the closest to BOOM.

malford - 11-7-2013 at 19:52

As bfess laconically addressed, 80g of FP will do the structural damage of 100g of TNT, exemplary of a random, potentially unreliable internet source to which Anders referred us.

Anti, you address ignorance regarding the blind reliance on RE, however you demonstrate the same by blindly dismissing it.

Ral123 - 11-7-2013 at 21:57

I've just had the idea: you can always use higher R.E. material in less amount, but replacing high R.E. with low can be done only of you seek energy and gases volume, not brisance.

Fantasma4500 - 12-7-2013 at 06:57

yes, but it still doesnt describe WHAT work we are to have done, is it a 80 20, 50 50 or 20 80 balance of brisance and VoD??

''It is used to compare an explosive's effectiveness relative to TNT by weight only, TNT equivalent/kg (TNTe/kg).''

i dont get it, what is effectiveness measured in..? total energy released? heat? brisance? VoD?

HE is seldomly something you can carefully measure as theres so many factors that plays in, sure call me ignorant.. but go to any demolitions site, and then you should soon realise that they do rough measurements, and not with many decimals

malford - 12-7-2013 at 15:13

Quote: Originally posted by Antiswat  
i dont get it, what is effectiveness measured in..? total energy released? heat? brisance? VoD?


I haven't spent too much time to find it, but since TNT is used to destroy things, I'm sure that is the basis on which they are compared. Does anyone have any sources for the origination of RE?

If I were the one establishing RE, I would place samples of explosives of like masses inside of samples of, say, concrete, rock, wood/drywall, etc., then analyze the destructive power by the amount or extent of dislocated material. Perhaps something similar is how they did it.

[Edited on 12-7-2013 by malford]

Ral123 - 12-7-2013 at 21:35

There are many types of tests. Everybody has heard of lead block expansion.
Let's say 100g BP can split a big log or something. Then 50g TNT would also work. Or 40g Tetryl, or 33g PETN. I suspect that's the purpose of R.E.

malford - 5-9-2013 at 19:47

I came across this thread through a search and caught a typo in my post above. Obviously with FP having a 0.80 RE, 80 grams of FP would not be equivalent to 100 grams of TNT as I mistakenly typed. The correct description is 100 grams of FP is equivalent to 80 grams of TNT. Taken from Wikipedia:

"The R.E. factor is the amount of TNT to which 1 kg of an explosive is equivalent; the higher the R.E., the more powerful the explosive."