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Asthenia
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[*] posted on 7-10-2012 at 18:05
Fuel Air Explosions


Can someone explain what exactly it is? What it requires to create them. I have been blowing stuff up for a while(ANFO TATP etc) but I just ran into this concept. I want to understand this more and wanna hopefully do it.

[Edited on 8-10-2012 by Asthenia]
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[*] posted on 7-10-2012 at 18:48


Sure, I think I understand a bit what you're intending to ask. Imagine a missile that blows gasoline out the back, very powerfully in small droplets. The alkanes vaporize in the hot Vietnamese jungle air, and your left with a rather huge mass of highly inflammable air/alkane mixture. Spark and wahVoom! It's a big bang for the buck.
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weiming1998
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[*] posted on 7-10-2012 at 19:48


Quote: Originally posted by Asthenia  
Can someone explain what exactly it is? What it requires to create them. I have been blowing stuff up for a while(ANFO TATP etc) but I just ran into this concept. I want to understand this more and wanna hopefully do it.

[Edited on 8-10-2012 by Asthenia]


Fuel-air explosives are basically made of a very flammable, possibly toxic gas/volatile liquid (like ethylene oxide) and something that can ignite it. When the explosive is initiated, the gas/volatile liquid quickly escapes, vaporises and mixes with the air surrounding the explosive. A remote ignition source is then used to ignite the mix of air and flammable gases. This causes a huge explosion (because both the fuel and the oxygen are gases, having a very large surface area). The shock-waves generated and the changes in pressure also causes damage to structures and harm to people.

You can make a fuel-air mix at home. In fact, it's very simple (albeit less dangerous than the military fuel-air explosives). Just take a few ml of ethanol (or any volatile, flammable liquid) and put it in a large plastic bottle with a lid. Close the lid and shake the bottle around for a bit (that causes the liquid to vaporise and fill up the bottle). Blow air into the bottle if necessary. Finally, open the bottle and carefully ignite a match on a stick and place the burning match on the opening of the bottle. This will cause the flammable liquid (now a gas) to ignite, making a whooshing sound.
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[*] posted on 7-10-2012 at 20:13


Good ol' whoosh jug demo ;) My favorite example of this is what is termed, "ethanol cannons".

You take a bottle, drill two screws into it, opposite each other and leaving a small gap between them, and then vaporize some ethanol in there, sealed with a rubber stopper. You than touch a tesla coil to one end, creating a spark between the screws, which ignites the mixture and BOOM! Instant cannon!

Kids love this demo ;) Remember, safety first! Cover your ears!




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[*] posted on 7-10-2012 at 20:30


about that ehanol canon :D enjoy
http://www.youtube.com/watch?v=Jw5mmJ__o8U&feature=plcp
I've been interested for a while about that FAE's but I think it's too complicated to be done well. For me one volume egdn in metal will give better shock wave at any distance then same volume of something that may or may not detonate and is expected to simply deflagrate. All that can be done at home I think is conventional explosive with termobaric effect. May be the easiest way is adding Al to stuff like nitromethane.
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[*] posted on 7-10-2012 at 20:53


That is the most amazing cannon ever! I can't believe he just fires it with one hand all nonchalant! :D



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CaliusOptimus
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[*] posted on 7-10-2012 at 21:21


Quote: Originally posted by sargent1015  
That is the most amazing cannon ever! I can't believe he just fires it with one hand all nonchalant! :D



No joke! Ral has got some bad ass post-apocalyptic weaponry...
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Asthenia
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[*] posted on 8-10-2012 at 05:10


Okay guys thanks! I thought that is what it was! But does the gases that are spread out in the air really have THAT much power when they ignite??? I have seen high speed cameras shooting fuel air explosions and it was amazingly powerful!
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[*] posted on 8-10-2012 at 05:34


Quote: Originally posted by Asthenia  
Okay guys thanks! I thought that is what it was! But does the gases that are spread out in the air really have THAT much power when they ignite??? I have seen high speed cameras shooting fuel air explosions and it was amazingly powerful!


The surface area of reactants. A block of iron won't burn, but an extremely fine powder will even spontaneously combust. The larger the surface area, the faster the reaction will proceed and the larger the amount of energy produced in a certain amount of time.
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Ral123
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[*] posted on 8-10-2012 at 08:13


If I have to make a device with termobaric effect I'd use composition witch gives a lot of hydrogen, high temperatures and possibly micro sparks everywhere. But not TNT witch give only soot and causes fires supposedly.
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[*] posted on 8-10-2012 at 08:22


An interesting twist on the "whoosh jug" can be had by pouring around 15 ml of 3%H<sub>2</sub>O<sub>2</sub> into the botton of a milk jug, then add a pinch of manganese dioxide from a battery to get it to decompose and release the O<sub>2</sub>. Then spray in some flammable aresol and loosley cap the jug.

Please ignite from a distance, as the first time I tried this I lit a lighter over the opening and the jug detonated into several pieces and blew me on my ass. Quite a fright. No injury though.

Before you all start screaming "K3wl!", I was only 15 when this happened. (Now I use E-matches and 20ft leads, lol.)




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[*] posted on 8-10-2012 at 10:55


Could you do ANFO plus Gasoline? How about flash powder and gas?
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[*] posted on 8-10-2012 at 18:00


Ok ..... First you are asking about how to get PETN precursors by the gallon and now you are "curious" about how FAE's work .... Google can lead you to a lot of info.
From what I understand ..... This is not a "how do I make a ...." Forum.
If you have any input, theories, ideas, suggestions etc or results .... Discuss them.
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Asthenia
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[*] posted on 8-10-2012 at 18:14


I am sorry about that? I used Google first of course not to waste your guys time. But simply there isn't that much on Google about FAE's. Sorry, but I didn't mean to get your panties into a bunch...
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[*] posted on 8-10-2012 at 18:15


A small flash charge laid underneath a small ziplock bag of kerosene or similar should disperse and ignite the vapor/aerosol. If not, a secondary charge with proper timing could ensure ignition. In theory.



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[*] posted on 8-10-2012 at 18:21


Okay cool. That makes sense. Well I have my answer!
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[*] posted on 8-10-2012 at 18:23


Actually... If it goes into a fire ball does that mean I have achieved FAE?
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[*] posted on 8-10-2012 at 18:33


The vapor needs to expand rapidly before ignition. A good flashpowder should do this fine, and a secondary BP charge a few inches to a foot or two away, and timed right. Check youtube, and do a forum search. Several threads on this.



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[*] posted on 8-10-2012 at 18:36


Any fuel that burns in air and causes an explosive effect ..... Loosely speaking is a FAE. Hydrogen, acetylene, gasoline etc.
Typically the term is used for Thermobaric devices..
Thermo=heat, baric=pressure
Very select fuels/liquid explosives do that ....
A Propane derivative is an example ... Has the the capability of detonating while being a vapour ....
This causes the pressure wave duration to last a few hundred milliseconds instead of a few tens.
Please don't start a thread asking ..... How do I make propyl X. I can buy iso-propyl alcohol by the gallon.

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[*] posted on 8-10-2012 at 20:09


Quote: Originally posted by Asthenia  
Actually... If it goes into a fire ball does that mean I have achieved FAE?


No.... FAE is much more that a simple fireball... A FAE is pretty much a secondary explosive that use air as is source of oxidizer. The real big difference is that the fuel/air mixture is not initiate by the flamme, but by the shockwave of the second charge. Yes, it create a fireball, but it is so fast that you almost dont see it (if all detonate).

There is multiple thing you need to think before you have a complete setup for creating a FEA:

A complete fuel mixture --> You need a detonation promoter and a volatil, energetic and a big range of explosive limit fuel
ex: Iso-propyl nitrate / Ethylene oxide

A good fuel disperser charge--> You need something that will disperse all your fuel and dont prematurly ignite it (explosive that produce almost no flame) and if possible you dont want to create low oxygen spot, so try to use OB possitive explosive.
ex : Nitroglycerine/ammonium nitrate

A good fuel initiation charge--> Well the principle is as simple a a detonator, but the shockwave need to be strong enought to initiate, lets say, 4 square meter of explosive. The size of the charge depend of your detonation promoter, so you need to test or calculation if you want to be sure.
Ex : C4

A precise delay timer--> The delay depend of how good is your dispersion systeme, the temperature and how volatil is you fuel. It always change from desing, but the delay is roughly 100ms. So you need a delay timer that have a millisecond precision (really easy to make).
ex : microchip and two transistor


This is the really big line of fuel/air explosive, but you will find that even the delay that poorly made det cap create is enought too lower you detonation efficiency by 50%... You can try it yourself, but it is not a weekend trip, it is a project in itself.


I hope it help to clarify, even if my english is not perfect!:P

Good luck


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[*] posted on 8-10-2012 at 20:43


That's why I'd take the EGDN. You can rely it'll do decently :D Specially per unit weight it's superb compared to all other explosives.
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franklyn
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[*] posted on 13-10-2012 at 08:41


http://www.sciencemadness.org/talk/viewthread.php?tid=8741#p...

http://www.sciencemadness.org/talk/viewthread.php?tid=4080#p...
http://www.reuters.com/resources/flash/embedvideo.swf?editio...

Related threads
http://www.sciencemadness.org/talk/viewthread.php?tid=7769
http://www.sciencemadness.org/talk/viewthread.php?tid=7762
Always a good place to look first , particularly references cited in footnotes
http://en.wikipedia.org/wiki/Fuel-air_explosive
From there _
Fundamental and Applied Studies of Fuel-Air Detonation
http://www2.galcit.caltech.edu/~jeshep/icders/cd-rom/EXTABS/259_20TH.PDF

Other references _
Basic Phenomenology of Deflagration, Detonation Transition & Detonation
http://ukelg.ps.ic.ac.uk/41HJ1.pdf

Detonations - Attachment: Gas Explo.pdf (207kB)
This file has been downloaded 837 times
View online
http://www.hse.gov.uk/foi/internalops/td_din/fire-exp/td5_039/td5_039.htm

Useful resources for ignition _

Engineering Design Handbook , Military Pyrotechnics Series , Part 1 ,
THEORY AND APPLICATION

http://www.dtic.mil/dtic/tr/fulltext/u2/817071.pdf

Engineering Design Handbook , Military Pyrotechnics Series , Part 3 ,
PROPERTIES OF MATERIALS USED IN PYROTECHNIC COMPOSITIONS

http://www.dtic.mil/dtic/tr/fulltext/u2/830394.pdf

Spontaneous Heating and Pyrophoricity
http://www.hss.doe.gov/nuclearsafety/techstds/docs/handbook/hdbk1081.pdf

Explosibility of Metal Powders
http://www.dtic.mil/dtic/tr/fulltext/u2/b270510.pdf
or else get it here , not as good _
http://www.titanium.org/files/ItemFileA4681.pdf

Combustible Metals
http://www.ehs.pitt.edu/assets/docs/combustible-metals.pdf


[Edited on 14-10-2012 by franklyn]
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[*] posted on 26-10-2013 at 10:48
Following on the preceding citations , further resources _


Mechanisms of Initiation of Detonation in Explosive Vapor Clouds
www.dtic.mil/dtic/tr/fulltext/u2/a051854.pdf

Fuel-Air Detonations: The Distributed Blast Concept
www.dtic.mil/dtic/tr/fulltext/u2/785681.pdf

Effect of Additives on the Lean Detonation Limit of Kerosene Sprays in Air
www.dtic.mil/dtic/tr/fulltext/u2/a095190.pdf

Detonation Characteristics of Some Dusts and Liquid-Dust Suspensions
www.dtic.mil/dtic/tr/fulltext/u2/a148735.pdf

Fuel-Air Explosive Simulation of Far-Field Nuclear Airblasts
www.dtic.mil/dtic/tr/fulltext/u2/a135042.pdf

Fundamental Mechanisms of Unconfined Detonation of Fuel Air Explosions
www.dtic.mil/dtic/tr/fulltext/u2/a084367.pdf

Requirements for Initiation and Sustained Propagation of Fuel-Air Explosives
www.dtic.mil/dtic/tr/fulltext/u2/a162301.pdf

Fundamental Aspects of Unconfined Explosions
www.dtic.mil/dtic/tr/fulltext/u2/913443.pdf

Peak Overpressures for Internal Blast
www.dtic.mil/dtic/tr/fulltext/u2/a071312.pdf

Attachment: Gas Explosion Handbook.pdf (2MB)
This file has been downloaded 13030 times


Prediction of Blast and Fragment Loadings on Structures
www.dtic.mil/dtic/tr/fulltext/u2/a476207.pdf
www.dtic.mil/dtic/tr/fulltext/u2/a111849.pdf ( likely older version of same)

Blast Effects Caused by Explosions
www.dtic.mil/dtic/tr/fulltext/u2/a433657.pdf

The Physics, Chemistry and Dynamics of Explosions
www.dtic.mil/dtic/tr/fulltext/u2/a554418.pdf

Introduction to a Unified Theory of Explosions (UTE)
www.dtic.mil/dtic/tr/fulltext/u2/758000.pdf

Modular Simulation of HEI Fragments and Blast Pressure
www.dtic.mil/dtic/tr/fulltext/u2/a248205.pdf

Fast Reactions of Aluminum - A Literature Review
www.dtic.mil/dtic/tr/fulltext/u2/a057215.pdf


.
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[*] posted on 27-10-2013 at 00:28


Great summary of articles franklyn, hail the Defense Information Center!



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[*] posted on 27-10-2013 at 05:42


A fun fuel/air explosive idea:

http://amasci.com/freenrg/ideas.html#smoke





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