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Author: Subject: Fuel-Air Explosives
IrC
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[*] posted on 29-3-2009 at 00:16


I imagine you all think too much and therefore miss the simple and often best answers. The best FAE I have yet seen is non dairy powdered coffee creamer. The largest and most powerful FAE detonations in human history have all so far been grain dust (usually initiated by static electricity) as was mentioned in a previous post. Mythbusters did a hell of a good job demoing the creamer FAE. For initiation all they did was stick a lit flare at the mouth of their dust cannon powered by compressed air.

While fireballs were the result little thought is needed to achieve power, as in study of an implosion type fission bomb. Logic indicates the FAE inside the spherical explosive blanket is going to expand in a superheated state while delaying detonation until the cloud has mixed with enough air to reach stoimetric proportions (since it would fail to burn until enough O2 was present). Whether a delayed initiator of compressed piezo design in the center or use of self initiation of the heated expanding cloud for initiation is utilized (which would still be hot enough for enough time near the center), it seems on the surface either way the desired result would be reached.

I have always found it safer to invent these things in thought and let the uncle fester idiots actually try them. We already know that if the idea is a good one somewhere someones military R&D labs has already toyed with the idea. Or have they?



[Edited on 3-29-2009 by IrC]
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[*] posted on 29-3-2009 at 14:55


Here it is. Also I took advantage of the lovely new multi-attach feature and attached another very interesting patent about a hybrid thermobaric warhead...

I believe the main reason the Hellfire missiles use the laminated type warhead, is because it is much less sensitive to mechanical shock than the normal charge containing Al powder. They have to be extra insensitive to be able to punch through tank armour and detonate on the inside... I remember seeing a little slow motion video of a Hellfire punching through about three feet of reinforced concrete and detonating on the other side...

While we may not want a charge to be extra extra insensitive, the laminated design is still interesting because it allows the use of totally ubiquitous materials like Al foil and telfon tape. It could be especially useful if/when the government decides to regulate reactive metal powders more heavily.. I think it would be especially interesting if it was possible to simply make a loose spiral of Al foil and fill the gaps with a high powered liquid (or castable) explosive to get a comparable thermobaric effect to Al powder... It would be both safer and simpler/easier/cheaper.

@IrC, I can pretty well guarantee that every accidental "fuel-air explosion" involving a particulate fuel was a deflagration.. Personally, I doubt that you're ever going to get more than a fireball out of nondairy creamer..

Quote:

I have always found it safer to invent these things in thought and let the uncle fester idiots actually try them.


For a given explosive yield, fuel-air detonations (the two event style) are far safer than the equivalent quantity of HE. Simply because the burster and initiator must both be detonated synchronously, which is almost impossible to do accidentally.


Attachment: layered EBX warhead.pdf (170kB)
This file has been downloaded 970 times

Attachment: Hybrid_warhead.pdf (124kB)
This file has been downloaded 823 times


[Edited on 29-3-2009 by 497]
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[*] posted on 29-3-2009 at 15:48


I think both types of FAE fuels have use. The lower impulse fireball fuels can be used as decontamination devices for bio-hazards where the structural damage is minimum.
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[*] posted on 29-3-2009 at 19:58


was it in good ol mexico that a gas line ruptured in a large sewer filling several square city blocks with natural gas/propane.Townspeople were annoyed when they began detonating destroying entire city blocks ,the affected area looked like a warzone.Many deaths/wounded IIRC actually took them some time to determine the cause as the destruction was so intense and widespread.The solution I would have though relatively obvious.I dont care deflagration or DDT. videotape of a fire dept waiting a bit to long to ignite what they thought was diesel fuel poured in a basement was in fact gasoline, gave it the time to disperse(practice)
to what must have been near ideal ratios and the house demolished with splinters remaining and fortunately the guy tossing the flare miracoulously unharmed as the video looked as if the entire side of the home took him with the flying debris which while slow Im sure by HE standards was to fast for the eye w/o slo mo assist and even then it wasnt clear what happened to the fireman.Unassisted dust/gas explosions arent something to sneeze at w/200mph wind speeds and the real killer 90psi overpressure.

I dont claim alotta knowledge about the hellfire missile but my belief was it was intended as a large very long range anti-tank missile armed with a variety of warheads like the TOW but with 2-3 x the range possibly fire and forget with
tandem warheads etc but penetrating 3ft reinforced concrete just by the effect of kinetic energy?I believe youve mistaken a hellfire for a bunkerbuster.Only an air drpped bunker buster from altitude of at least 500lbs will penetrate 3ft of concrete by kinetic energy alone.Only the 120mm abrams firing APFSDS long rod DU penetrators will penetrate 3 ft reinf concrete or the armor of a modern mbt but not a lightly built missile whose intented use is penetration/destruction by means of chemical energy.








[Edited on 30-3-2009 by grndpndr]

[Edited on 30-3-2009 by grndpndr]

[Edited on 30-3-2009 by grndpndr]

[Edited on 30-3-2009 by grndpndr]
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[*] posted on 29-3-2009 at 20:44


Well they do weigh 100 pounds... and move 1000 mph...

But really, they don't have to penetrate all the way through, just enough to direct the explosion mostly to the back side. The warhead is only ~10 kg. And now that I see that they also make shaped charge variants, it is certainly possible that the video I saw was a shaped charge in action.

Here's some good info. They call it an "FAE" a few times, which is false, but other than that, it seems like accurate. Here's a nice video of one in action.

[Edited on 30-3-2009 by 497]
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[*] posted on 30-3-2009 at 13:44


Sounds more like a squash head SC. obsolete against modern composite armor,reactive armor and spaced armor.
like the name the thin walled warhead impacted the target material'squashing' the explosive charge into something like a pancake.When tightly compressed against the target the warhead detonated setting up shockwaves overstressing the material and causing spalling to the interior of the heaviest tanks and causing large chunks of concrete to spall from the interior of hardened buildings at several hundred MPH still devastating against bunkers/std armor w/o penetration.

You likely saw an advanced warhead design 497 that used chemical energy rather than kinetic.Regards

I sure like the teflon/al Idea ,sadly I dont indulge myself any...:(
Really think you should view some grain dust explosions that have occurred in concrete structures.The effects are devestating ,reinforced concrete shattered if you hadnt known better youd have swore it was a HE demolition.
They peaked around the 70s but still occur in many different situations were flammable dusts can become dispersed and ignited.90 PSI isnt a fireball! Regards
OK i looked at the link,its a thermobaric warheaad intended for use against enclosed buildings/caves.Its accuracy meant to hit tanks at IIRC 5kilometers allows it to go through windows/doors cave entrances. It is as you say an enhanced warhead using some sort of metals 'increasing pressure peaks for longer durations than normal explosives' similar effects to a dust explosion but with all that power (Heat/pressure) contained in a small package[Edited on 30-3-2009 by grndpndr] Pott perchlorate/AL dust?

[Edited on 31-3-2009 by grndpndr]

[Edited on 31-3-2009 by grndpndr]

[Edited on 31-3-2009 by grndpndr]

[Edited on 31-3-2009 by grndpndr]
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[*] posted on 12-4-2009 at 17:18


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

2 liters fuel in a standard soda bottle, 23% Isopropyl Nitrite, 23% Diethyl Ether, 54% Heptane

Approx 1.2 meter standoff at 1 meter elevation over hard packed snow.

0.080 second delay between burster and initiator.

Captured at normal speed with sound, and 600fps.




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[*] posted on 12-4-2009 at 17:53


It was even more impressive seeing it in person.. The videos just don't do it justice. But the high speed footage is nice, I love the second frame after the initiator fires, it's just a perfect spherical orange detonation cloud (the second to last still frame shown in the video.)

It was surprising to me how much damage it did to the hard packed snow below it. You can't really see it in the videos, but the snow is substantially cratered and pulverized for several meters around the initiator stand.

As the video says, hopefully more to come.

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[*] posted on 15-4-2009 at 07:28


Congrats! I think you are the first amateur that actually made a working FAE! :D

Care to elaborate a little more on the timing of the two charges, the fuel weight/explosive weight ratio, confinement and composition of both the dispersal and detonation charge? :)

I'm surprised that the fuel cloud was able to make DDT with only 2 liters fuel! I guess that is why you used the relatively large amount of IPN? Are you planning the same ratio's for the 20 liter charge? Maybe 10 or even 5% IPN would suffice in this case...

What is your opinion about the possibility of using methylated spirits with a good deal of dissolved ammoniumnitrate as the fuel? This would have been my fuel of choice since both are cheap and easily obtainable around here. Energy output would be somewhat less on a weight basis compared to your mix. It would be a simple mix-and-fire option, although I've never read about the performance of ethanol/methanol as the fuel in the available patents concerning FAE's...

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[*] posted on 15-4-2009 at 16:07


"Care to elaborate a little more on the timing of the two charges"

Radio transmitter with multiple channels, receivers programmed to specific channels (1 and 2). Transmitter set to send out signal on channel 1 at time X, channel 2 at time Y.

"the fuel weight/explosive weight ratio"

Fuel weight roughly 1400 grams, explosive burster roughly 9 grams.

"confinement and composition of both the dispersal and detonation charge? :)"

Dispersal charge pure recrystallized Erythritol Tetranitrate (ETN) powder in 11mm OD vinyl tubing, inside 12.7mm ID PVC pipe, inserted in the center of the fuel. Initiating charge was a small plastic bag of cast ETN.

"I'm surprised that the fuel cloud was able to make DDT with only 2 liters fuel!"

As I understand it, DDT refers to deflagration-to-detonation transition, the general process by which a subsonic combustion wave becomes a supersonic detonation front. In this case it would be the exact opposite. The initiating charge gave the dispersed fuel a shock wave, detonating it. This detonation front traveled through the fuel until it made the transition to a deflagration. Additionally, the amount of fuel is largely unrelated to its ability to detonate, in fact larger charges would have more difficulty fully detonating than smaller tests.

"I guess that is why you used the relatively large amount of IPN?"

Isopropyl nitrite is added to increase volatility and sensitize the mixture.

"Are you planning the same ratio's for the 20 liter charge? Maybe 10 or even 5% IPN would suffice in this case..."

The 20 liter charge is tentatively planned to be a mixture of roughly 2.5 liters Isopropyl nitrite, 5 liters hexane, 12.5 liters heptane. These are rough estimates, actual content may vary.

"What is your opinion about the possibility of using methylated spirits with a good deal of dissolved ammoniumnitrate as the fuel?"

Sounds feasible, but defeats the purpose of an FAE in some ways. For me the entire idea of an FAE is to utilize non-explosive fuels and take advantage of atmospheric oxygen in creating an explosion. Using fuels with high amounts of molecular oxygen content would defeat this to some degree, not to mention using something that's already a high explosive.

[Edited on 4-16-2009 by NameWithheld]




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[*] posted on 15-4-2009 at 17:13


I don't think adding AN would help at all for the sensitivity of the fuel cloud. Its not a particularly strong or unstable oxidizer, and it is insensitive to shock waves. I doubt it would add much/any to the power of the FAE, since all the oxygen necessary is supplied by the air, the AN may well be wasted.

I have never seen any mention of alcohols as fuels in all the military FAE literature I've seen. I don't see why it wouldn't work, but testing is the only way to know anything for sure.. "Methanol is a high octane fuel that is extremely resistant to detonation." Yes I realize this is in the context of an internal combustion engine, but similar principles may apply to FAEs...
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[*] posted on 16-4-2009 at 11:22


Great achievement.
What kind of hardware did you use for the FAE ?





What a fine day for chemistry this is.
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[*] posted on 16-4-2009 at 15:10



-"As I understand it, DDT refers to deflagration-to-detonation transition, the general process by which a subsonic combustion wave becomes a supersonic detonation front. In this case it would be the exact opposite. The initiating charge gave the dispersed fuel a shock wave, detonating it. This detonation front traveled through the fuel until it made the transition to a deflagration. Additionally, the amount of fuel is largely unrelated to its ability to detonate, in fact larger charges would have more difficulty fully detonating than smaller tests."

I see what you mean, but wouldn't this mean that the initiating charge needs to be upscaled linearly with the amount of fuel used?

Pressure drops exceedingly fast with increasing distance from the initiating explosive, so I can't really see how the shockwave could propagate al the way through the fuel/air cloud without the reaction of the fuel/air mix itself adding energy to the shockwave to sustain it. This would mean that given the fuel/air cloud is of large enough size and sensitivity it would eventually sustain detonation on it's own, independant of the amount of initiating explosive.

-"]I don't think adding AN would help at all for the sensitivity of the fuel cloud. Its not a particularly strong or unstable oxidizer, and it is insensitive to shock waves."

I can't imagine that there is a lot of volatilization in those 80 miliseconds, moreover is IPN also characterized as an insensitive explosive, used for improving combustion in diesel engines. Wouldn't the insensitivity, stability and ability to mix with alkanes make IPN just a logical choice? Decomposition temperature of the additive is probably important analogous to thermobaric explosives, but this does not exclude a range of other possible additives IMO...

Anyway, can't wait to see the big one!...:D

[Edited on 16-4-2009 by nitro-genes]
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[*] posted on 16-4-2009 at 18:44


Quote:
but wouldn't this mean that the initiating charge needs to be upscaled linearly with the amount of fuel used? Pressure drops exceedingly fast with increasing distance from the initiating explosive, so I can't really see how the shockwave could propagate al the way through the fuel/air cloud without the reaction of the fuel/air mix itself adding energy to the shockwave to sustain it. This would mean that given the fuel/air cloud is of large enough size and sensitivity it would eventually sustain detonation on it's own, independant of the amount of initiating explosive.


No initiators need not be scaled up. Even if the shock wave from the initiator is not strong enough to initiate detonation in the entire cloud at once, it will begin a detonation wave in the vicinity near the initiator, which will, with proper types of fuels and fuel/air ratios continue to propagate through the rest of the cloud until it hits the outer edges were the mixture is too lean. There should be no deflagration involved, at least until the main detonation wave runs into an minor areas of too lean or rich fuel/air ratios. And size seems to be unimportant for all be the most insensitive fuels. I've seen patents for 225ml FAE charges!

Quote:
I can't imagine that there is a lot of volatilization in those 80 miliseconds, moreover is IPN also characterized as an insensitive explosive, used for improving combustion in diesel engines.


Actually yes there is substantial volitilization, and actually 80ms is pretty short, we will be using a longer delay next time. It is known that hexane nearly completely evaporates in less the 200ms after dispersion. It is far harder to detonate a fuel (with the exception of the most sensitive ones such as pure nitrates/nitrites or epoxides) that is not substantially evaporated. And the IPN I'm talking about (Isopropyl nitrite) is not explosive at all, while Isopropyl nitrate is the difficultly detonated and fairly feeble explosive cousin. The main reason the IPN is added, is that upon being subjected to a shock wave, it splits into isopropoxyl radicals and nitrogen monoxide. The alkoxyl radicals are apperently responsible for the powerful sensitizing/catalyzing effect that alkyl nitrate/nitrites have on fuels. Since the N-O bond is weak in both nitrites and nitrates, both nitrite or nitrate esters seem to work similarly.

Adding NH4NO3 to a fuel would simply result in small particles of it floating around in the cloud. I have a hunch that the particles would not even take part in the fast free radical combustion reactions that occur near the detonation front (considering some particles of fuel don't even take part.)

Quote:
Wouldn't the insensitivity, stability and ability to mix with alkanes make IPN just a logical choice?


Yes.. though that was clear.

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[*] posted on 18-4-2009 at 17:40


What is your camcorder to film 600 fps??? high speed camera can film up to 25,000 fps easily but they cost a lot, and other camcorder can film at max 60 fps...



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[*] posted on 18-4-2009 at 18:32


http://www.dpreview.com/news/0801/08010601casiof1.asp



A word to the wise: NEUROFEEDBACK

http://citizenworks.org/corp/dg/s2r1.pdf
http://www.newscientist.com/mobile/article/mg21228354.500-re...
http://www.shadowstats.com/article/no-414-hyperinflation-spe...

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[*] posted on 19-4-2009 at 13:31


Thanks a lot!!

it more seem to be a camera that a camcorder but if it can shoot a 1200 fps:o i think it will be ok for 1200$:D




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[*] posted on 20-4-2009 at 21:37


Quote: Originally posted by 497  
I often wonder what an entire building filled with stoiciometric oxygen-acetylene would look like going off...



Hell, why settle for oxygen? What I'd like to see would be the setting off of an acetylene - ozone binary mix. If held in liquid phase at low enough temperature, could pure ozone possibly be contained long enough to allow its dispersal with acetylene liquid (or snow). Probably the detonation would be spontaneous, requiring no primer.

...it would be glorious! ;)




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[*] posted on 23-4-2009 at 14:14


May test with two litres of ordinary heptan/gasoline to compare the time scedules with the mix you already tried.
To increase the velocity in the fuel/air mix it could be of interest to add for example 1 -2 % TATP to the fuel.
The best way may be to create some acetylene under the "spray process" How? Maybe its possible by reacting the hot water gas from the first explosion with some finely grinded CaC2 to get C2H2 inmixed with the gas and air.
Probably the C2H2 will make the combustion goes faster all over the cloud.
Suggestions?
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[*] posted on 23-4-2009 at 14:57


If it's a hot day, you have a large initiator, and you get the timing right, you might be able to pull off a detonation with straight gasoline... It'd be interesting to see at least.

About the TATP, I very much doubt you'd get a noticeable increase in velocity by adding it.. I know of no fuel besides possibly hydrogen that will detonate at over 2000m/s in air. TATP might increase the fuel sensitivity a little, but I remember reading somewhere that organic peroxides were found to be ineffective sensitizers for FAEs, but it would be easy enough to try.

I must say, I seriously doubt you could generate enough acetylene quickly enough from CaC2.. But go for it if you think it could work.. If I was going to try anything with acetylene, it would be a cold saturated solution of it in acetone..

[Edited on 23-4-2009 by 497]
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[*] posted on 23-4-2009 at 23:37


Quote: Originally posted by 497  
If it's a hot day, you have a large initiator, and you get the timing right, you might be able to pull off a detonation with straight gasoline... It'd be interesting to see at least.

About the TATP, I very much doubt you'd get a noticeable increase in velocity by adding it.. I know of no fuel besides possibly hydrogen that will detonate at over 2000m/s in air. TATP might increase the fuel sensitivity a little, but I remember reading somewhere that organic peroxides were found to be ineffective sensitizers for FAEs, but it would be easy enough to try.

I must say, I seriously doubt you could generate enough acetylene quickly enough from CaC2.. But go for it if you think it could work.. If I was going to try anything with acetylene, it would be a cold saturated solution of it in acetone..

[Edited on 23-4-2009 by 497]


The CaC2 might be mixed with an explosive giving H2O as detonation product. ( An explosive not reacting with the basic carbide-ion under storage) AND hopefully the formed acetylene will NOT detonate/decompose in the same time its formed.... or it does and when this is not working :)
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[*] posted on 24-4-2009 at 16:49


You could probably do it.. Explosively disperse water and CaC2 together. You'd have to have a long delay to wait for the acetylene to form and mix with the air. It depends on whether the CaC2 could react much before it blew away or settled to the ground.. hope you have a lot of CaC2.
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[*] posted on 24-4-2009 at 23:49


Quote: Originally posted by 497  
You could probably do it.. Explosively disperse water and CaC2 together. You'd have to have a long delay to wait for the acetylene to form and mix with the air. It depends on whether the CaC2 could react much before it blew away or settled to the ground.. hope you have a lot of CaC2.


Probably its better to use several initiation points instead of one as in the movie if using pure gasoline. A cricle of initiation charges connected with detcord, this to ensure a near simultaneous combustion of the entire cloude.
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[*] posted on 27-4-2009 at 16:33


Quote: Originally posted by 497  
I often wonder what an entire building filled with stoiciometric oxygen-acetylene would look like going off"

[Edited on 17-3-2009 by 497]


I was looking at another thread with acetylene /oxygen as the mixed gas and deflagration or detonation velocity and whether by implication a detonator would be required.I found the results from a respected det vel. table dowloaded from this site and another i cant recall. Acetylene/oxygen @2/1 gas mixture det vel = 2660mps,2/3 ratio, 2720mps,3/1
ratio 2320mps VOD.Again whether by ignition or detonation initiated the chart doesnt mention.Safe wager would say very little left of a home let alone a reinforced bunker if detonated from the interior.Even if detonated from the exterior a large device retaining optimum overpressure would do substantial damage to a hard target and most likely kill all the occupants unless equipped with sealed compartments similar to bank vaults.:o JMHO

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[*] posted on 30-4-2009 at 12:43


First of all, I'm Dutch. Please don't mind the misspelled crap. Im not an idiot.

I have some experience with thermobaric explosive charges based on a high explosive center charge with a surround of plastisized metal power.

Some successful test have been done by me and other members of a dutch forum called pyroforum.nl, with for example a 30 gram plastic bonded PETN centercharge along with a surround of 40 grams 70/20/10 Al/KClO3/PIB @> 1.7 gr/cc. This is all based on US patent 6.955.732.

This setup is capable of fully burning the aluminumpowder over a (relatively) extended period of time producing roughly 20 kBars of pressure. Since I don't own a high speed camera its hard to give any data on the exact time it takes for the charge to burn the completeness.

Would it be possible to use such a setup to ignite a FAE? If you can extend the burning time of your alumnium long enough for the cloud to mix with the air properly, it might be possible to use such a charge to spread the fuel, as well as igniting it at the same time.

Unfortunately the burning time of such scarges cannot be delayed by using for example coarser aluminumpowder, since from my video material the effective range of such charges seems to be limited to about 80 cm. @7000 m/s thats uuhhm, not really long. :D Further from the charge there is simply not enough pressure and heat.

As far as I know the burning time of a thermobaric charge cannot be extended much by the reason mentioned above. The time it takes to ignite the fuel cloud cannot be speed up either since, according to tests by other members here at SMDB, is takes at least 50 milliseconds to properly spread and vaporise the fuel with air.

If a design like this would work, it wouldn't take precise timing of seperate desperion and igniting charges. Also, there's a possibility to add more oxigen to the atmosphere by raising the oxidiser content of the earlier mentioned surround charge. This would result in a more evenly mixed cloud (oxygen from the inside out!), and therefore more effective combustion.

A possible drawback, or even failure of this idea would be that the surround charge is incapable of reaching enough atmosferic oxygen because of the 'blanket' of gasoline or whatever is in its way to burn.

Any idea's? Any data on the 'burning time' of thermobaric charges? According to US patent 6.955.732 the combustion takes from 10 to 50ms to complete.






[Edited on 30-4-2009 by Leander]

[Edited on 30-4-2009 by Leander]

[Edited on 30-4-2009 by Leander]
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