Sciencemadness Discussion Board

Did i just make a fuel air explosive?

DrManhattan - 9-6-2015 at 23:47

I was reading up about the 1983 Beirut Barracks bombing and the blast mechanism used was a "gas enhanced" fuel air explosive utilizing compressed butane in canisters employed with PETN. This really caught my eye seeing as how this bombing is cited numerously as being one of the largest non nuclear explosions. They say it was equivalent to 21,000 pounds of TNT. Im sure they used a hell of a lot of conventional high explosives but the thought of a fuel air explosive from butane really caught my eye.

Seeing as how butane canisters are sold everywhere i decided to give it a go using a 220 gram canister of butane with a a length of homemade det cord filled with 20g of ETN/AL (70 ETN/30 AL (200 mesh) wrapped around the can. First i set off 20g of ETN/AL to gauge how big the blast was. Then i set of the second charge with the butane canister added. I was really shocked by the results. I was expecting the can to go up in a flame but instead i got a much larger detonation. It wasn't the familiar sharp crack of ETN but rather a large thump and a noticeably stronger shockwave. When the shockwave hit i could really feel it on the second charge.

In my understanding fuel air explosives work by using a bursting charge to disperse a cloud of fuel that mixes with the surrounding oxygen in our atmosphere and is then detonated by a second charge.

I'm not quite sure of what happened with my second charge considering it was only initiated with the 1 charge. Maybe it was more thermobaric than fuel air explosive? My guess is the ETN/AL burst the can instantly releasing the butane. The burning aluminium only ignited the butane when it was mixed with the atmospheric oxygen. The shockwave of the initial blast sped up the deflagration of the butane to the point where it was instantaneous.

My theory is merely a guess so i thought id ask you guys for your opinion.

roXefeller - 10-6-2015 at 12:40

I would agree with your guess that it wasn't. The short time scale involved wouldn't be enough to bring oxygen into the mixture. It's been mentioned here before that the F/A bombs require a very keen sense of timing between expansion blast and detonation blast.

Dany - 10-6-2015 at 13:47

First the Beirut explosion against the U.S marine Barracks was not the most powerful non-nuclear explosion as several example exist were several 100 tons of high explosives were detonated. One example is the Sailor hat operation conducted by the U.S navy in 1965. The test was a 500 tons of TNT high explosives detonated at seashore of the Kahoʻolawe island, Hawaii. The objective of this test is to simulate the effect of small nuclear detonation on U.S navy ships. see the video of the detonation here:

http://www.youtube.com/watch?v=ZVM9_attO1Q

Now, from the experimental setup and the mode of detonation it is hard to believe that your device behave as an FAE. The overpressure felt at certain distance from your charge would result from deflagration of the released butane into the air. Butane is not generally used in FAE device. In fact isobutane require a large booster (80-100 g of Tetryl) to detonate [1] compared for example to acetylene (1-2 g of Tetryl). Single event FAE exist but need a catalyst to induce ignition and subsequent detonation. Here's a paragraph taken from [1]:

"Fuel Air Explosion is presently a two event process., viz, dispersion of fuel in air and detonation of the fuel air cloud. Current emphasis is to make it a single event process with the elimination of second event requirement. In single event process the fuel and the initiating chemical (catalyst) are dispersed simultaneously to form a vapour cloud. The catalyst reacting with either the fuel or oxygen in the air produces free radicals to initiate explosive mixture. Several worker have achieved success with the concept of single event FAE. Injection of gaseous pyrophoric fuel, dimethyl zinc, in an equi-molar oxy-acetylene mixture has been reported to initiate the detonation in the mixture. Current efforts are under way to achieve more detailed qualitative/quantitative data of this phenomenon."

Also for single-event FAE see this patent:

https://www.google.com/patents/US4463680

I strongly recommend you to read the attached file which gives you very useful info on FAE.

References:

[1] A. Appa Rao, Fuel Air Explosives, Def Sci J, Vol 37, No 1, January 1987, pp 23-28.

Dany.



Attachment: Fuel Air Explosives.pdf (347kB)
This file has been downloaded 1102 times

Hennig Brand - 10-6-2015 at 13:56

edit: Dany, I see that you got in there ahead of me. I will leave what I have anyway, since I added a few different ideas.

Under the right circumstances and quantities explosive mixtures of flammable gas and air when ignited can accelerate to a low velocity detonation. However, as RoXefeller stated, it takes time for the fuel and air/oxygen to mix and form a concentration in the correct range for detonation; according to the attached document, time between dispersion and the second charge (initiation charge) detonating is normally around 150ms (with the charge described). The aluminum in your charge likely ignited the butane, as you suspected, which then deflagrated.

This document seems to have a lot of useful information for the experimenter. I am tempted to give an FAE a try sometime. EBWs fired by trigatrons controlled by even a simple 555 timer circuit should give more than accurate enough control of the dispersion and initiation. Even well made regular low electrical power electrical detonators would probably work reasonably well (delay of commercial electric detonators can often be in the 10s of milliseconds range IIRC but can often vary considerably, while EBWs are normally extremely consistent and accurate with delays of only microseconds with long cables and a reasonably fast switch and to as little as small fractions of a microsecond with short cables and a well designed triggered spark gap switch).


Attachment: Fuel Air Explosives Technical Document.pdf (427kB)
This file has been downloaded 760 times


[Edited on 11-6-2015 by Hennig Brand]

Microtek - 11-6-2015 at 01:15

I have been wanting to try and replicate the experiments in that patent for some time (they mention doing small scale tests on sub-milliliter quantities, which appeals to me), but I have been unable to acquire ferrocene.

nitro-genes - 12-6-2015 at 07:39

Just some brainstorming... but maybe sorbate (genereally available anti-fungi) kan be converted into methyl (nitro) pyrrole species (nitrite?), reacting with FeCl2 to give organo iron complexes? :-)

If it exists, it may provide both catalizing effect from alkoxy radicals formed as well as ignition by the iron.

There also seems to be a somewhat less reactive organo iron complex with salicylic acid, no idea about the preparation though.

https://books.google.nl/books?id=LnzpCAAAQBAJ&pg=PA257&a...

Also wonder how effective an iron salt would be, coupled to a "fragile" anion, like iron oxalate (although not soluble) for example

[Edited on 12-6-2015 by nitro-genes]

[Edited on 12-6-2015 by nitro-genes]

KesterDraconis - 22-10-2015 at 15:29

Is it possible for gasoline to detonate if it were a vapor mixed with near pure oxygen gas?

I've heard of people talking about gasoline "detonating" in what is called engine knocking, but I've been unable to find (at least through many pages of a google search) a source that actually speaks of this as an actual detonation wave, rather than just switching the term out for "flash" or "explode" in this instance.

ecos - 22-10-2015 at 15:37

gasoline shouldn't detonate but deflagrate ! I am not sure but this is my conc.

Morgan - 22-10-2015 at 15:39

Tidbit
Petrol oxygen explosion, 2005
https://www.youtube.com/watch?v=s3LT3ldL8yQ

OneEyedPyro - 22-10-2015 at 16:49

Detonation in engine terms is just when the fuel/air mixture ignites before the piston reaches the top of its stroke, nothing to do with the speed at which the fuel burns.

I'd imagine gasoline would work as an FAE under the right conditions but it would likely require a stout initiator and even more precice timing compared to other more reactive fuels such as ether, isopropyl nitrate mixtures, acetylene etc.


[Edited on 23-10-2015 by OneEyedPyro]

KesterDraconis - 23-10-2015 at 16:48

Quote: Originally posted by OneEyedPyro  

I'd imagine gasoline would work as an FAE under the right conditions but it would likely require a stout initiator and even more precice timing compared to other more reactive fuels such as ether, isopropyl nitrate mixtures, acetylene etc.
[Edited on 23-10-2015 by OneEyedPyro]


Yes, I would suppose so as well.

The reason I ask is because recently I had a little fun filling up a 2.5 liter soda bottle with oxygen gas, putting about a milliliter and a half of gasoline inside*, and then capping it all. I shook it like a whoosh bottle until the gasoline had become a vapor. I then lite a fuse attached to it.

I expected it to be much like a dry ice bomb, and simply have the expanding gas explode the bottle, except with more predictability and a bit more force than a dry ice bomb.

The results were surprising, and perhaps it was just due to the force of the gases being pushed out of the bottle so fast, but it was not only far louder but also more destructive. It sparked the question in my mind as to whether this mixture, as reactive as it is, could detonate and produce a more powerful and destructive shock wave.

*using octane as an "average" for gasoline, and having previously calculated the number of moles in the 2.5 liters, this mixture was a nearly a perfect stoichiometric mixture, by my calculations.

EDIT: I normally don't touch gasoline. For some reason I find it a frighteningly dangerous thing, even when compared to many explosives. However, I felt safer with a such a small amount, and I would honestly recommend this. Good fun without too much danger form my perspective.

[Edited on 24-10-2015 by KesterDraconis]

Bert - 24-10-2015 at 05:49

https://books.google.com/books?id=lRIbOfiUEHQC&pg=PA95&a...

You probably were seeing a deflagration- experimental data shows a pretty massive HE booster initiation in open air is required, or a long tube/gallery to allow a run up from deflagration to detonation.

http://www.cdc.gov/niosh/mining/userfiles/works/pdfs/madea.p...

[Edited on 24-10-2015 by Bert]

OneEyedPyro - 24-10-2015 at 08:26

"Experimental data shows a pretty massive HE booster..."
Yes but FAEs can undergo partial dets so I'd bet a smaller initiator would suffice for a small device.

It wouldn't hurt to stick a blasting cap in the bottle instead of lighting it with a fuse just to see what would happen, maybe you could bury them in some loose sand to help show the difference in power between fuse initiated and cap initiated.

KesterDraconis - 24-10-2015 at 09:31

Quote: Originally posted by Bert  
https://books.google.com/books?id=lRIbOfiUEHQC&pg=PA95&a...

You probably were seeing a deflagration- experimental data shows a pretty massive HE booster initiation in open air is required, or a long tube/gallery to allow a run up from deflagration to detonation.

http://www.cdc.gov/niosh/mining/userfiles/works/pdfs/madea.p...

[Edited on 24-10-2015 by Bert]


Yes, I expected as much. Really though, my main question is as to whether or not the mixture actually could detonate, given a booster.

I think I may try using a high explosive booster with it sometime, like OneEyedPyro suggested. This will probably be a while in the future however, since I am currently a bit too wrapped up in school and work to synthesize any HEs for testing.

nitro-genes - 10-11-2015 at 07:40

After some patents posted by Rosco in other threads regarding the use of ferrous picrate as fuel additive, I was wondering...

For example: US 7335238 B2 (and the like)
Does the production of ferrous picrate possibly lead to organo-metal compounds (sandwich), similar to ferrocene? It can be formed from ferrous cabonate and picric acid and supposedly is soluble in very hydrophobic solvents, which seems rather strange for a picrate salt, or do organo-metal compounds need to be reduced to Fe(0) to form? Salicylic acid can form organo-metal compounds, the use of picric acid may be even more interesting for use in FAE.

[Edited on 10-11-2015 by nitro-genes]