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tom haggen
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Thermobaric explosives
For quite sometime I was having a really hard time wrapping my head around the mechanics of a fuel air explosion. That is untill I saw it demonstrated
on the discovery channel the other night. Anyway the military is now using these special explosives that seem to have a thermobaric effect much like
that of a fuel air explosion, however everything is contained in one unit. Apparently they use these devices to blast rag heads out of their caves in
afganistan. I was just curious if any of you guys have had any first hand experience with these types of explosives. Apparently they require much
less air then a standard fuel air explosive.
N/A
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Rosco Bodine
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They are basically fuel rich , negative oxygen balance explosives that create a lot of air fueled afterburning of highly thermic incompletely burned
detonation products ,
precisely the sorts of gaseous fireball afterblast that
is very unhealthy in places like a mine or tunnel or cave .
It does two things that are deadly in an enclosed space ,
it sucks all the oxygen out of the air , and coverts it to a whole lot of heat which lasts for an unbearable number of seconds sufficient to
incinerate or cook or cookoff whatever is there .
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nitro-genes
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A FAE is not very effective in confined spaces, since the fuel cloud needs a lot of oxygen to be able to detonate. Thermobaric weapons are basically
enhanced blast explosives that use a large excess of a reactive metal powder like aluminium or magnesium to lengthen the pressure pulse and create a
forward moving combustion front of burning metalpowder that moves through the tunnel some distance away from the initial detonation point. Metal
powders can burn much longer and easier in an oxygen poor environment than other fuels can do, so this makes them much more suitable for this use.
Unlike the fuel in an FAE, the metal powders merely combust instead of detonate slowly releasing a large amount of heat and pressure...
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Zinc
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| Quote: | Originally posted by nitro-genes
Thermobaric weapons are basically enhanced blast explosives that use a large excess of a reactive metal powder like aluminium or magnesium
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Magnesium can also use nitrogen from air.
[Edited on 11-2-2007 by Zinc]
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up
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| Quote: | Originally posted by Rosco Bodine
They are basically fuel rich , negative oxygen balance explosives that create a lot of air fueled afterburning of highly thermic incompletely burned
detonation products ,
precisely the sorts of gaseous fireball afterblast that
is very unhealthy in places like a mine or tunnel or cave .
It does two things that are deadly in an enclosed space ,
it sucks all the oxygen out of the air , and coverts it to a whole lot of heat which lasts for an unbearable number of seconds sufficient to
incinerate or cook or cookoff whatever is there . |
| Quote: | Originally posted by nitro-genes
A FAE is not very effective in confined spaces, since the fuel cloud needs a lot of oxygen to be able to detonate. Thermobaric weapons are basically
enhanced blast explosives that use a large excess of a reactive metal powder like aluminium or magnesium to lengthen the pressure pulse and create a
forward moving combustion front of burning metalpowder that moves through the tunnel some distance away from the initial detonation point. Metal
powders can burn much longer and easier in an oxygen poor environment than other fuels can do, so this makes them much more suitable for this use.
Unlike the fuel in an FAE, the metal powders merely combust instead of detonate slowly releasing a large amount of heat and pressure...
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Well guys. You are saying to different things now.
Me myself, I have learned what Rosco Bodine says.
The explosive is calculated to form CO and H2, instead of CO2 and H2O, based on that the oxygen will burn first with the aluminium, and then it is
just enough oxygen to react with the carbon to form carbon monoxide, and the hydrogen is just H2.
Since The aluminim is highly energetic, the extrem amount of heat will cause oxygen from the air to react with the CO, to form CO2, and the H2 reacts
to H2O.
So it will be 3 "special effects"
1. It will suck the oxygen from the air woilently
2. The aluminium is higly energetic and gives alot of heat and pressure.
3. The products of the detonation wich is allready generated, will react 1 more time, so it works like a second shot. But practicaly all this happends
so fast that it seems like 1 shot.
Well. Thats how I have learned it.
Is there someone else that have some clue about thermobaric explosives? And dont mix with FAE's.
And one thing more. If it work like this, is there any reason that
Beryllium or Boron not can be used?
1 mol aluminium generates about 814,3 Kj.
1 mol Beryllium generates about 602,1 Kj.
1 mol aluminium is about 26,9 grams.
1 mol beryllium is about 9 grams.
That means, that 1 gram aluminium generates 30,9 Kj.
And Beryllium generates 66,9 Kj each gram!
Boron generates 58,8 Kj each gram.
I did some fast calculating on how much energy 100 grams of Oxygen balanced mixture of EGDN and beryllium generates, and the number was 15708,285614
Kj!
I just plussed the numbers of EGDN with the numbers of Beryllium. Gonna do a more accurate calculation one day.
But that was even the oxygen balansed mixture!
The thermobaric mixture will generate ALOT of more heat and pressure. Gonna calculate it tomorow or something.
Someone got some thoughts about this to?
And yes. I know that both boron and beryllium is super expensive! Realy expensive!
[Edited on 1-3-2007 by up]
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Rosco Bodine
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A mixture of Picryl sulfide and titanium powder would probably be just dandy as an armor piercing HE + hellfire and brimstone , thermobaric for
bunkers and caves and such .
You could wrap it around a core charge of dinitrodichlorobenzne if you really wanted to make things
doubly dirty , and throw in some capsules of white phosphorous for good measure as a 1-2-3 punch
which would leave a really nasty post detonation atmosphere .
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not_important
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And beryllium and its compound are toxic - http://rais.ornl.gov/tox/profiles/beryllium.shtml I'd not want to be troops required to enter an area where sicu a device had been recently used.
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Rosco Bodine
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Titanium powder seems to have a special ability for
ignition by a detonating explosive and continuing to
burn long enough and hot enough to ignite other flammables in the blast cloud .
This was tested in connection with reactive targets .
http://www.boomershoot.org/general/fireball.htm
[Edited on 1-3-2007 by Rosco Bodine]
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nitro-genes
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Yes, even large particles of titanium keep burning for a long time and with a bright white flame. This is one of the things it is valued for in
pyrotechnics. About 5% of sponge titanium added to flashpowder gives a very nice effect... 
Uploaded a demonstration video of the FAE and thermobaric bomb. They don't mention anything about the mixtures composition, though those all to
familiar dark grey finger prints on the bucket say enough. Yeah, 3-8 micron aluminium powder stains everything! 
http://rapidshare.com/files/18803011/New_WinZip_File.zip.htm...
[Edited on 1-3-2007 by nitro-genes]
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up
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Thanx for sharing that clip nitro-genes!
But can you guys give us an conclusion of wich way Thermobaric explosives work.
Do oxygenbalance mather, etc.
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quicksilver
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I'm actually familiar with boomershoot and can offer a little tid-bit. It's the wrapping and construction of the FAE that makes it all happen. One may
be sloppy with one's materials but if the construction is right-on you have a ball. That being said what it really needed for a good shot is a design
of "container within container".
This could be where flash powder could be very useful as well.....damn sensitive flash made from materials that are extremely impact sensitve would
light it up every time, but more importantly allow for the "layering" in construction that is nesessary for success.
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Marsh
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I have been pondering this and decided I would ask. Thermobarics still seem like a subject covered little anywhere.
It is my conclusion that the desired thermobaric effects come from a high heat from detonation, as well as the lengthened pulse of the detonation. At
which point does the lowered VoD of the explosive actually begin to have a negative effect on the ability to produce a sustained mechanical wave?
For instance, if we were talking about a simple thermobaric fuel/oxidizer composition, would we simply look to balance the oxygen ratio for a better
brisance, only with simple concern towards using a metal fuel? Or would we seek to use a quite rich metal fuel balance which could prolong the
deflagration(?) after the initial detonation, but with less concern towards brisance? Is there truely deflagration after the detonation? If so, at
what point does a fully deflagrating (non-detonating) mixture become suitable as a thermobaric composition? For instance, where does the line get
drawn to where a deflagrating mixture does not work, and a low VoD detonating mixture does? At what point does the pulses length have a deteriorating
effect on magnitude and damage it can create through energy transfer?
I have heard that one possible composition for a thermobaric effect is 43:22:35 AN:NM:AL. Like previously discussed, is it possible that another metal
would prolong or possibly greatly enhance the thermobaric "work" which the charge can perform, instead of when using aluminum?
I guess the whole idea seems hard to grasp to me at this point. I'm trying to get an idea of the optimum thermobaric compound, if there even exists
such a thing. I guess in simplest lamen terms, it would be the device which carries a "boom" the farthest. The main delehma for me is visualizing
where the line of mechanical work differs between high-VoD energetics and thermobarics. I guess one exerts forces more directly as close, high
velocity blast waves of great pressure magnitudes (high-VoD energetics), where as the other (thermobarics) focus on the carrying of those waves to
further distances as well as greater gas output(?), like bass from a stereo system. So in a sense, thermobarics sacrifice close-proximity initial work
they can perform in trade for lengthened pulses they can transfer further away.
Am I at least close in my assumptions?
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quicksilver
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Perhaps you're comparing apples and oranges. When you described this in your last paragraph the thrust of the question dealt with sound. Remember that
"the work" being done on one level is a conflagration. On another level the action is a detonation. However the query deals with "which carries a
'boom' the farthest."...... You can see the dichotomy here. Whenever you move large amounts of gases (air) the perceived sound will be greater than
with lesser amounts, etc.
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Marsh
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Yes, I had a feeling my ability to understand this fully is compromised at the time.
Let me explain how I arrived at my reference to a "boom", or sound.
Isn't it true that the thermobaric wave produced is effectively a wave traveling at the speed of sound?
I assumed if this was true, than of coarse a wave of higher energy potential would therefore travel farther than a wave a lower energy potential. For
instance low-frequency waves generally carry on further than high-frequency waves.
So I also assumed if the optimal thermobaric compound was one that accomplished work further away than other compairing compositions, it would thus
create a louder, farther traveling soundwave, which is directly derived from the lengthened detonation wave I believe. In short, you would imagine
it's wave to produce a "boom" which would sound louder, as well as carry on to farther distances than a high VoD explosive of lesser impulse length.
That is the way I imagine it, so please do correct me on these principles so that I may better understand.
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E-tech
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I am a new member to the forum- and figured I should post on this subject- I've had personal experience with these types of weapons in the last few
months, and the designs are all familiar to me.
From what I gathered so far- it seems that the confusion is in regard to the type of explosive used in thermobaric weapons. Interestingly enough,
that isn't really as important as the design of the weapon itself. a single explosive mix can be used- it's what the U.S. uses in some systems, but,
a better effect can be had by separating the fuel from the explosive. The idea is not to generate a fireball- but to get a fireball to form behind
the initial blast wave, reinforce it, and extend the impulse (the time under pressure). Why is this important? fatalaties start at about 45psi- if
they are of an "instant" nature. If the body is put under pressure for about 150milliseconds, you can kill with only 7psi.
Reaction of insensitive metal fuels can be a problem in cold areas (like caves)- incomplete combustion occurs if the fuel exceeds about 35% of the
charge weight. If something like a monopropellant or energetic binder is added to the fuel- this will cease to be a problem, and you can go as far as
10 times as much fuel as charge (by weight). Chemistry really has little to do with the designing of these weapons- warhead mockups and testing is the
name of the game- even the thickness of the casing and it's material of construction can change the results.
simple aluminized explosives also work very well, but the more rapid reaction of the aluminum IN the charge doesn't produce as dramatic effect as an
Aluminum "surround" covering the charge.
Having been a hundred meters from equivalent warhead weights- the effect is very noticable. Regular explosives give that familiar feeling of
pressure, but of such a short duration, you don't move- it moves thru you very quickly. A thermobaric charge of the same weight WILL push you over on
your butt.
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Marsh
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So what you are saying is that it is possible to introduce enough heat from a main charge surrounded by aluminum to actually oxidize the aluminum
cloud which is dispersed by the oxygen in the surrounding air?
One would assume the degree to which this would actually work would be minimal, I can't imagine how well this could truely be made to work efficiently
without actually having the aluminum in the initial reaction zone where the majority of heat is generated.
I am quite curious about these thermobaric devices and how well they work on an amateur level.
Like previously mentioned, a mixture of 43:22:35 AN/NM/AL was detonated in a video I watched, I believe by our member Axt.
This is quite high levels of aluminum in a reaction, more than any other composition I have stumbled across which works. In the video, it looks like
it works well, although its true thermobaric effect is unknown: http://www.youtube.com/watch?v=WElWg2I0xSA
I would imagine these sorts of energetics' effects could be tested by a wave (sound) or vibration measuring device placed some distance from the
charge. Any ideas of where one could start to actually test the effectiveness of such a device?
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nitro-genes
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Well, I've experimented with these "reactive surround EBX's" as well. Very simple setup, plastic 100 ml jar with in the middle a tube filled with 10
grams of PETN/Pib, surrounded by 100 grams of 600 mesh flake Al with various %ages of KNO3. (Usually NC is used, though this was obviously much more
simple ) To my surprise was the pressure that could be felt in the open field
much less than for aluminized explosives like ammonal type compositions or aluminized PBX compositions, although total energy release must have been
much higher. Maybe without any confinement, like inside structures or caves, these metal/air clouds may barely make DDT. IIRC, metal powder/air
mixtures proved to be very difficult to actually detonate instead of merely burn in tests concerning metal powder FAE's. Something that, like Marsh
said as well, may be less of a problem when the aluminium is used as a mixture with the explosive itself.
It looks very cool though, video on request! 
Maybe I have misunderstood the concept, as you said it is important to lenghten the pressure pulse by letting the aluminium react behind the inital
blastwave. Does this mean you need to implode the metal powder/NC?
[Edited on by nitro-genes]
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E-tech
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To tell the truth, I'm not certain about the heat introduction and it's capability to oxidize the aluminum cloud. It's the effects of the combustion,
and it's ability to aid the initial blast wave. on an amateur level, the noticable effect will be fireball, and more noticably, felt pressure-
setting off a known weight of regular explosives, and comparing how it feels, then attempt a thermobaric charge, and seeing if the pressure/shock is
longer lasting and more painfull is the only way of testing it. Short of REALLY expensive pressure transducer- type of equipment. Not just peak
pressures but impulse (time under pressure) measuring gear is needed.
The primary way the weapons gain their effect is through heat- when confined- it increases the pressure; far more noticable in confinement than in the
open. It's not a DDT type of reaction. in it's basic form, you are increasing the afterburn from the detonation. In an enclosed area, this will
cause heat/asphyxiation damage, but only secondary to the sudden spike in pressure everyone in the cave/building will experience because of that heat.
Don't confuse thermobarics with FAE (even metal powder FAE- more commonly known as SFAE- solid fuel air explosives). A FAE weapon is a two stage
event- the initial charge ruptures the fuel container and spreads the fuel. A second charge then detonates (not just lighting it) the cloud of spread
fuel. putting a fuel around an explosive will easily produce a fireball. Engineering the casing thickness/material, the fuels' particle size
(appearantly critical in using aluminum- using 50micron as opposed to 5 micron size particles radically changes the effects), the fuel to charge
ratio, the reactivity of the binder, and even the size of the charge are all taken into consideration when designing these things. I've placed fuel
around explosives on a few occasions (called Flame Field Expedients by the military), but, the damage was from flame- not pressure. When I
experienced the blast from these- I felt a wave of heat, like opening an oven door. When feeling effects from true thermobaric weapons, I was pushed
to the ground.
The open field effect nitro-genes felt from aluminized explosives is similar to the effect you are looking for. The aluminum surround method is used
by the US and Russians in shoulder weapons (it won't work in larger sizes), but it is far more difficult to engineer- especially since the aluminized
explosive method works just as well. If you want to get a truly thermobaric effect- don't use AN- that materials' well-documented "heaving" effect is
from it's heavy evolution of gases, not much more.
Nitro-genes; no- you don't need to implode the metal powder- just the fact that it will take time (microseconds in scale) for the aluminum to react
after the initial detonation is all you need. The two ways found has been aluminized explosives, or surrounding the charge with a layer of aluminum.
The surround is VERY difficult to engineer without expensive testing equipment (and a BIG budget). Using a known military mixture is possible- but
they tend to use HMX.
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quicksilver
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There are a heck of a lot of idiosyncrasies here in this discussion. Low-frequency & high-frequency waves, energy potential, & thermobaric
waves all need to be clearly defined in their respective context. Thermobarics & FAE energy are not necessarily the same correct?
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E-tech
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Correct- thermobarics and FAE are not the same. My previous post explains it. There is no mention of low/high frequency waves, energy potential, or
thermobaric waves in any of the test/patent/military papers I have seen in regards to these weapons. It's always about temperature and pressure- how
high it goes at it's highest point (good, but the basis for regular explosive weapons' damage) and how long it maintains a fatality-causing pressure.
The goal of a thermobaric weapon is to extend what is called the "impulse pressure" which is the time under pressure that the charge causes, not to
reach new heights of temp and pressure. In fact, the Russian system produces only 75% of the peak pressure of C-4, but, it more than quadruples the
amount of time that pressure is exerted on the target. The short, high pressure pulse is good at breaking glass, but little else at any distance. A
longer, lower "push" is capable of shoving over brick walls, and killing people much more effectively. Basically you are trying to extend the blast
pressures' "time on target". FAE weapons do this, but, thermobaric weapons do so more reliably in various enviroments, and especially in built up
areas. It also is being used in this new "precision weapon" mania. I fire a regular anti-personnel rocket in a combat situation- frag goes
everywhere, maybe through the wall of the house next door to the one I shot the rocket at- killing a noncombatant. I fire a thermobaric weapon- an
enhanced blast weapon. Keyword being BLAST. These are light cased weapons that produce almost no shrapnel, and have no fragmentation sleeves, etc.
The house I shoot with a thermobaric rocket collapses, trapping everyone the initial explosion doesn't burn/kill/crush. The blast wave slows down
rapidly as it travels through the air, and the neighbor's house is undamaged.
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Axt
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Comparison of conventional HE, FAE & thermobaric explosives.
http://videos.m90.org/videos/futureweapons-thermobaric bomb.wmv
Russian RPO Shmel-M PDM-A. Which looks like a gelled liquid monopropellant + metal thermobaric (also shows some incendiary charges).
http://warfare.ru/video/wmv/shmel.mpg
http://warfare.ru/video/2007/rpo.wmv
A vid of the M72 LAW firing thermobaric charge, attached pdf evaluates thermobaric charges for this.
http://www.talleyds.com/tds_web_videos/Improved%20M72LAW%20W...
[Edited on 1-6-2007 by Axt]
Attachment: EVALUATION OF EXPLOSIVE CANDIDATES FOR A THERMOBARIC LAW rocket.pdf (246kB)
This file has been downloaded 3537 times
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E-tech
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Currently adopted systems/fillers
SMAW-NE; PBXIH-135 (HMX, Al)
BLU-118/B; PBXIH-135 (HMX, Al)
XM-1060 40mm grenade; YJ-05 (a mix made by ensign-bickford, they aren't sharing what it's made of)
RPO-A: Filled with a mix just like Talley mix 5640, with a bursting charge.
The thermobaric Hellfire (AGM-114N) has a nifty layered warhead design (using PBXN-112 and flouridated aluminum). For the do-it-yourselfer, this
patent will point you in the right direction for experimentation:
US5467714 Enhanced Performance, High Reaction Temperature Explosive
It deals with reacting Al and flourine using common materials: aluminum foil and Teflon tape
The patent includes some tests made on concrete blocks that give some very familiar results.
I've seen the talley defense systems papers before, but have yet to see a nice LAW rocket in the hands of a soldier. The XM-1060s all went to
afghanistan. I've been trying to find the exact composition of PBXIH-135 for a while now, has anyone else found it?
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pinky
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Composition PBXIH-135(or PBXN-113)
• 45% HMX
• 20% Binder Material(hydroxyl terminated polybutadiene binder)
• 35% Aluminum
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quicksilver
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Damn good stuff there...AXT, thanks for taking the time posting that!
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Mardec
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Yeah axt thanks for the nice info as usual.
A question: If I understand right. A explosive like isopropylnitrate, which would yield N2 CO and H2 would be a good thermobaric explosive? Or does it
need to be a better explosive like RDX or PETN with Al powder to drag the O2 balance down?
And the Al, which mesh should it be? Using precious german blackhead just isn't going to happen..
[Edited on 2-6-2007 by Mardec]
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