Sciencemadness Discussion Board - Thermobaric explosives

Thermobaric explosives

tom haggen - 10-2-2007 at 23:23

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.

Rosco Bodine - 10-2-2007 at 23:41

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 .

nitro-genes - 11-2-2007 at 05:25

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...

Zinc - 11-2-2007 at 08:13

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

Magnesium can also use nitrogen from air.

[Edited on 11-2-2007 by Zinc]

up - 28-2-2007 at 17:52

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...

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]

Rosco Bodine - 28-2-2007 at 18:44

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 .

not_important - 28-2-2007 at 18:44

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.

Rosco Bodine - 28-2-2007 at 18:57

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]

nitro-genes - 28-2-2007 at 19:24

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]

up - 1-3-2007 at 16:49

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.

quicksilver - 2-3-2007 at 06:31

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.

Marsh - 28-5-2007 at 21:30

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?

quicksilver - 29-5-2007 at 06:36

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.

Marsh - 29-5-2007 at 07:23

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.

E-tech - 30-5-2007 at 12:51

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.

Marsh - 30-5-2007 at 13:48

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?

nitro-genes - 30-5-2007 at 13:58

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]

E-tech - 31-5-2007 at 06:25

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.

quicksilver - 31-5-2007 at 06:44

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?

E-tech - 31-5-2007 at 09:23

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.

Axt - 31-5-2007 at 10:06

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

E-tech - 31-5-2007 at 11:27

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?

pinky - 31-5-2007 at 12:29

Composition PBXIH-135(or PBXN-113)

• 45% HMX
• 20% Binder Material(hydroxyl terminated polybutadiene binder)
• 35% Aluminum

quicksilver - 1-6-2007 at 06:55

Damn good stuff there...AXT, thanks for taking the time posting that!

Mardec - 1-6-2007 at 09:04

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]

nitro-genes - 1-6-2007 at 12:42

I don't think detonating IPA itself will produce any effect at all. TNT isn't a thermobaric explosive despite of its negative oxygenbalance as well. There is an orange fireball from oxygen-poor explosives though it doesn't add to the blast energy like metal powders do. Most of the carbon after a TNT or semtex detonation is visible as blacksmoke consisting of unreacted sooth that hasn't reacted with the surrounding air.

Metal powders can somehow burn much better under the oxygen poor conditions after the detonation, possibly because the reaction of aluminium with oxygen doesn't produce an expanding gas like carbon does, diluting the heat produced. For this reason I was quite surprised to see a reactive surround EBX consisting of an carbon based surround, I'm curious which additives they used to pull that off.

AN + Al mixtures can defenitely produce thermobaric effects, the only difference beeing the amount of aluminium that can be added to be still detonable. In that way are aluminized PBX compositions much more energy dense.

IIRC, depending on the mesh size of the aluminium only 3-5% of the aluminium reacts directly in the reaction zone that is followed by the shockwave itself. This is why Ammonal compositions are more sensitive than AN itself, and about 3-5% gives the most sensitive mixture. Larger percentages added behave inert and produce the elongated pressures characteristic for thermobaric devices hence react after the initial detonation. The secondary combustion cloud can be seen very well in videoclips that were shot at night of booster initiated 80% AN + 20% Al charges. The shockwave felt very "thick", and much more pronounced then from ANNM or ANFO charges of the same weight.

[Edited on by nitro-genes]

quicksilver - 2-6-2007 at 06:49

Quote:

Originally posted by Mardec
And the Al, which mesh should it be? Using precious german blackhead just isn't going to happen..

I have actually seen mil-surplus Al in various grades and the material used for energetic materials. Clearly written on the packing was "400 mesh or finer w/ .05% ALB" (I don't know what ALB meant, however).
It was flake but appeared to be a less reflective material and did not have such a "greasy" feel like 325 mesh w/ stearic acid.

Mardec - 2-6-2007 at 07:39

Quote:

Originally posted by quicksilver

Quote:

Originally posted by Mardec
And the Al, which mesh should it be? Using precious german blackhead just isn't going to happen..

Google is saying all sorts of crazy shit, that AlB = Aluminium boride. AlBx

X being a variable..

AlB is used as coating for metals..

But anyway, I have some 400 mesh Al in my lab, with stearic acid on it. Will get that shit of off my Al and then after exams do some testing

[Edited on 2-6-2007 by Mardec]

E-tech - 2-6-2007 at 12:57

There are no single-component thermobaric explosives, they are all mixes using Al, or fuels surrounding the charge. The isopropyl nitrate is used as an energetic binder to insure that all the aluminum fuel is consumed; It won't do much on it's own as far as thermobaric effects are concerned.
In other news- the Russians have another thermobaric mix that does use AN. It also includes Al and isopropyl nitrate, but the exact mix is not known. Military Parade Publishing (a Russian arms catalog they print) has pics of what is sold as a thermobaric submunition; it is said to hold 22 pounds of the mix. It looks like they are forgoing the weight/volume efficiency of explosives like HMX in order to obtain better far-field effects. The submunition looks like a coffee can on a parachute- still wouldn't like to get caught in a field of them, though.
I've worked with small (100gram) charges of RDX explosives with a thermite surround, and found the effects to be noticably different; materials pushed farther away and scorched whereas the no surround charge barely moved the objects around it. I haven't had a chance to test the really noticable (by the US military) effect of the thermobaric charge- the ability to go around corners. During one of it's first few tests, the BLU-118/B was found to be capable of sending it's blast/heat waves around a horshoe- shaped bend in a test tunnel complex in the Nevada desert. It's likely nothing more than a heat-driven pressure spike, but the ability to control or "bounce" a blast wave around a corner sounds like a nice challenge, especially once you get "mach stem" effects mastered. Thanks for the -135 mix. Where did you find it?

HMTD - 3-6-2007 at 07:48

Couple months ago I’ve tested EBX charge consisted of 21.5 g PBX center charge ( D=18 mm, 92.5/7.5=PETN/Polybutylene with d=1.62 g/cm3 and calc. VoD=8026 m/s and calc. P=26.3 GPa) and about 20-23 g Solid Fuel shell ( inner D=18 mm, outer D=25 mm, 70% ultra fine sph. Al(85)-Mg(15) , 25% NH4NO3 , 5% Polybutylene , d=1.5 g/cm3 ). So the total weight was about 45 g with explosive to fuel ratio ~ 1. EBX charge was placed in old felling to simulate partially closed volume. Two beer bottles were placed at different distances ( ~30 and 40 cm) from charge and also two plugged Al beer bottles (~50 and 70 cm) as pressure witnesses. The blast effect was much louder and with longer echo, I was (staying at 15 m away) a little stunned (maybe because the interference of blast waves had been reflected from the rear walls). So I would assume the total power was about 50-80 g TNT ( Of cause, it’s all very subjective, but several independent people (not knowing what the charge was, by video) said it was about 50 g TNT. Glass bottles were completely destroyed, closest Al bottle was slightly shrunk by blast wave, the second stayed untouched.
Vids&photos here:
http://rapidshare.com/files/35011853/Test.rar.htm
password to archive: 232348sdbjsdfgasmsuertr8wdaseke45yefajsd

[Edited on 6/4/2007 by HMTD]

pinky - 3-6-2007 at 10:56

Here is the source of composition PBXIH-135(PBXN-113)
and cool article "Optical Pyrometry of Fireballs of Metalized Explosives" from Propellants, Explosives, Pyrotechnics
-it's about testing a charges composed from metallic particles saturated with sensitized NM.

http://rapidshare.com/files/35054170/Metalized_Explosives.ra...

the password to archive: PBXN-113

Marsh - 4-6-2007 at 08:46

It does seem that the aluminum surrounds go on to react with the air with moderate means of pressure/dispersal/heat - although as to how efficiently I do not know.

I viewed one blasting cap closely to get an idea of sound and light when it detonated.

I then placed a duplicate 1.5g cap inside of a film container containing a small amount of 400 mesh aluminum powder around it.

The noise produced by the latter was quite noticeably louder, and a large flash fireball was also witnessed. The container and surrounding area still contained spread aluminum powder, so it was not all utilized. However enough of it was to notice a considerable effect.

This makes me ponder the idea of a peroxide water gel containing 50% aluminum as a possible useful surround charge covering something like a PETN PBX.

[Edited on 4-6-2007 by Marsh]

E-tech - 6-6-2007 at 15:06

If you were to try that experiment again, an easier idea wouls be to use a container with a heavier wall than a film canister. The confinement would allow the heat/pressure from the cap to spend a bit more time working on the Al powder, heating it to the point of ignition. The timing of that ignition is all important in this type of system. This can be determined through experiments with various Al particle sizes used in different charge diameters and with different casing strength. When the research was being conducted, it was found that 240um sized aluminum particles wouldn't ignite reliably until charge diameters were about 35cm. Below that, the Al would move ahead of the blast wave, and, even if it ignited later- it's burning would not contribute any aid to the initial blast wave. The three effects they found were1)immediate reaction of the Al behind the blast wave, assisting in it's formation/movement. 2)delayed/inconsistant reaction of the Al, which contributed little to the blast effect (most home experiments would likely be in this category) and 3)failure of complete Al ignition.
Adding 10 to 25% of an energetic material to the aluminum would also aid in it's complete combustion. double or single-based propellants should work fine for this. If you have a good amount of a single size of Al powder, then adjusting the strength of the container, adding an energetic material to the Al, and finally, increasing the size of the charge should allow you to fine-tune the design till you get the noticable effect. The problem is scaling up your experiments. The same size Al particle may not work in a larger design- casing, energetic binders, etc, all will need to be re-evaluated. The idea is to find what is called the "Critical diameter for particle ignition". An immediate ignition of the Al after the initial reaction of the explosive is the best way to get the desired effect. Flourine containing compounds ("inter-halogen oxidizers") are often used as a coating of the Al because it has been found that a telfon/viton coating of the Al will reduce the initial reaction energy requirements. A good ratio to start would be equal parts by weight of surround to explosive. Some designs go as high as 10 parts surround to 1 part (by weight) of explosive charge- these require a full 25% of an energetic binder for the Al, however. Monopropellant liquids are a good choice for this, but evenly dispersed gunpowder mixed in the Al will work, as may a high concentration of peroxide (I'd use 25% of my strongest peroxide and 75% Al)
Marsh- you said you used a 1.5 gram cap in your film canister experiment. 1.5 grams of what? and, where did you obtain the 400 mesh Al powder?

Marsh - 6-6-2007 at 22:45

Sorry, it was a 1.5g PETN cap.

The Al came from a barrel of unknown use.

nitro-genes - 7-6-2007 at 03:24

Nice one HMTD, definitely looks like an effective charge to me. The energy transferred to the rear wall of the felling appears much larger than can be expected from 21 grams of PBX alone. I think your fuel/PBX ratio of 1 is better than the 10:1 that I used, especially unconfined. How important is the density of the surround btw? Higher densities and plasticizing would yield higher pressures over the decreased distances and improved shock transmission of the PBX to surround. Is this why you plastized the surround as well? Never thought about this.

Like E-tech suggests, I reckon that most of the aluminium reacted long after the initial blastwave thus not aiding much in increasing the blasteffect in the simple setup I used. It would be nice to compare one of these surround EBX of yours with an equal weight of 70/20/10 PETN/Al/Pib aluminized PBX. The lowering of the activation energy for the aluminum particles is interesting as well. Teflon grease and spray are cheap and could be used to treat the aluminium powder to give better results.

PS, I tried your KNO3 PBX variant as well, though it seems to be pretty hard to detonate, would the KNO3 be replaceble by something like KClO4? (of course not mixing the Al and KClO4 together prior to plasticizin, which would be pretty dangerous

)

[Edited on by nitro-genes]

HMTD - 8-6-2007 at 03:27

Quote:

Originally posted by nitro-genes
Higher densities and plasticizing would yield higher pressures over the decreased distances and improved shock transmission of the PBX to surround. Is this why you plastized the surround as well?

Well, I think the same way - the denser the fuel=> the thinner the layer of it (with the same fuel mass) and lower the attenuation of initial blast wave from the PBX center(less dens.=>more air hollows=>energy consumption on air shrinking&heating ). So, the greater would be fuel speed and it’s temperature, faster the reaction with air and more energy would go to the increasing of the total blast effect. And you know better than me that plasticizing is pretty good and relatively easy way to increase density of anything in form of powder.

Quote:

Originally posted by nitro-genes
I reckon that most of the aluminium reacted long after the initial blastwave thus not aiding much in increasing the blasteffect in the simple setup I used.

This is also seems to be reasonable, but the speed of reaction of Al oxidation probably depends on Al particle size, its the temperature and speed, presence of oxidizing gases ( NOx, O2, CO2 etc.) and its concentrations. My example shows than fuel burns so quickly, that it forms the additional blast wave, probably with elongated zones of high or/and low pressure like in case of thermobaric explosives. I don’t know, separated the initial wave from the additional, or the charge forms just one enhanced blast wave (which probably would be better).

Quote:

Originally posted by nitro-genes
It would be nice to compare one of these surround EBX of yours with an equal weight of 70/20/10 PETN/Al/Pib aluminized PBX.

I think EBX would be significantly better than aluminized. Let’s see: The VoD of your composition would be ~ 7100 m/s, P ~ 18 GPa since, as you know, Al is inert in PBX. So, the result speed of Al particles will be the same as those for detonation products ( which also poor with oxidizing substances) and maximum what you can get is the enhanced sound & flash with no extra blast wave – so the explosion would be like the same charge of picric acid + extra flash and sound.

Quote:

Originally posted by nitro-genes
I tried your KNO3 PBX variant as well, though it seems to be pretty hard to detonate, would the KNO3 be replaceble by something like KClO4?

Sensitivity for any PBX(>30% explosive) depends on explosive %, its particle size and density. So it doesn’t matter KNO3 or KClO4 you will use, though the total power with KClO4 can be greater. I used KNO3 because it is cheap, and that type of PBX was just for fun like firecrackers. It better to use NH4NO3 but it is hydroscopic…

[Edited on 6/8/2007 by HMTD]

nitro-genes - 8-6-2007 at 08:57

Quote:

I think EBX would be significantly better than aluminized.

There is a limit of course to the extend by which you can keep adding aluminium to any explosive while still beeing detonable. So, the higher fuel/PBX ratio in a surround charge wil result in a much larger total energy release, but only if all of the fuel is efficiently utilized in the shortest timeframe possible. This is no problem for aluminized compositions since all the aluminium particles in an aluminized composition are subjected to the peakpressure of the detonation and for longer times than for the aluminium particles in a surround charge. Even in oxygen poor compositions there will be a lot of water and CO2 present after the detonation to react directly with the aluminium. So I believe that aluminized explosives would give faster reaction times for the aluminium than for any surround, which makes them much easier to work efficiently and aid more effectively to the blastwave. This is how I see it anyway, the closer the secondary combustion follows the inital blastwave the more it adds to it...

Quote:

Sensitivity for any PBX(>30% explosive) depends on explosive %, its particle size and density. So it doesn’t matter KNO3 or KClO4 you will use, though the total power with KClO4 can be greater.

I know you use the enthalpy of formation to determine whether a compound will act as an inert (absorp energy) or release energy to add directly to the shockwave. Though the lower activation energy for decomposition and/or higher energy release upon decomposition make that KClO3 is detonable on its own, while KNO3 isn't. So wouldn't there also be a difference in the amount of energy that needs to be absorbed by the oxidizer salt in order to release more energy by the reaction of its decomposition products? A composition containing a large percentage of KNO3 would therefore need a larger initial shock than one containing a large percentage of KClO3 or KClO4, no?

Anyway, the water resistance, higher energy and oxygen content, and higher density seemed advantageous to me.

[Edited on by nitro-genes]

HMTD - 10-6-2007 at 02:06

Quote:

Originally posted by nitro-genes
This is no problem for aluminized compositions since all the aluminium particles in an aluminized composition are subjected to the peakpressure of the detonation and for longer times than for the aluminium particles in a surround charge. Even in oxygen poor compositions there will be a lot of water and CO2 present after the detonation to react directly with the aluminium. So I believe that aluminized explosives would give faster reaction times for the aluminium than for any surround, which makes them much easier to work efficiently and aid more effectively to the blastwave.

You can believe in whatever you want, but there is a fact: for some reason the design of aluminized explosives charges was changed to more complex by separating HE from aluminium and sometimes by adding extra oxidizer and binder. And this was made for one reason – to achieve 100% combustion efficiency. (Do you see some accordance with the SC – the more complex is design (liner, lens, etc) - the more efficient the SC?). For additional info, see US6969434 , US5996501, US5467714 and related.

Quote:

Originally posted by nitro-genes
A composition containing a large percentage of KNO3 would therefore need a larger initial shock than one containing a large percentage of KClO3 or KClO4, no?

No, the difference in initiator mass would be hardly noticeable (in equal conditions – the same partial density of the same HE, additives particle size). All these additives (until them nano-sized, even KClO3) not reacting before the C-J, so there is no influence on detonation parameters (VoD, P, n). But I never told anything about after-reacting – there is no doubt, that more reactive components will react easier, producing more heat and pressure. But when using such powerful oxidizer like KClO4 there is no need to use HE at all – the KClO4/Al/S flash is one of the powerful non-explosive things I’ve ever saw. Just use card tube and the fuse.

E-tech - 14-6-2007 at 16:28

A patent that uses perchlorates mixed with the Al surround in the warhead design:
US6955732 Advanced thermobaric compositions

tito-o-mac - 30-6-2007 at 00:24

I would like to know whether I can make TBX(thermobaric explosives) with Nitrogen trichloride, or chloride or azode with aluminium powder. If it is possible, I would also like to know the detonation velocities of Nitrogen trichloride and the ratio of the mix.Thanks a dozen to everyone for giving the information!

Thanks!

Oh... 1 more very important question! In the discovery channel video, the expert said "the secondary charge will go off sometime after the explosion"- to ensure that the liquid is properly dispersed and ignited... So must all thermobaric explosives undergo a secondary explosion sometime after the 1st one to properly achieve the required properties of the detonation?

[Edited on 30-6-2007 by tito-o-mac]

not_important - 30-6-2007 at 01:39

NCl3 detonates sooner than you think, such as on contact with many organic materials. I would not like to mix it with aluminium, except by remote manipulation.

tito-o-mac - 30-6-2007 at 01:49

So what is the ratio of high explosives do I use? Petn or RDX : AL mesh

[Edited on 1-7-2007 by tito-o-mac]

tito-o-mac - 6-7-2007 at 08:12

Here, maybe this may be something useful to you guys.

------------------------------------------------------------------------------

Attachment: Fuel Air Explosive Systems.pdf (278kB)
This file has been downloaded 1945 times

TBX - 11-7-2007 at 14:32

These weapons work by mixing one or more reactive metals with a monopropellant and then placing this as a "surround" around a charge of conventional high explosive. The detonation of the high explosive causes the surround to react after the initial event,which is the main effect of these weapons. I thought this quote from patent 4331080 summed up these weapons quite well.

(1) The high rate of pressure generation or shock induced by the conventional high explosives causes shock initiation of the boron and the metal or other metal compounds to form the intermetallic compounds. The initiation mechanism is thought to be one of temperature elevation to the autoignition temperature of the boron and the metal or other metals which form the intermetallic compounds by shock compression of the distended mixtures.

(2) The resulting implosion of the boron and the metal or other metals to form the intermetallic compounds causes outward moving pressure waves to reflect on the inward moving shock waves. The reflected waves, generally more intense, (greater magnitude and shorter time) than the original waves enhances the fireball effect of the molten intermetallic compounds causing molten metal droplets to react violently with the oxygen in the explosive reaction environment.

(3) Interaction with the ambient environment causes tertiary burning and cratering to occur resulting from the adiabatic reaction temperatures, at least 3,000.degree. K., and generally within a range of 3,000.degree.-4,000.degree. K., and the high pressure shock generated. Confined composite high explosives when cast or consolidated to pressures ranging from 5,000 to 20,000 pounds per square inch with a column to diameter ratio of 2:1, provides detonation rates of 4-5 millimeters per microsecond. The sensitivity and stability of the composite high explosive is equivalent to the conventional high explosive used in the composite formulations.

Marsh - 11-7-2007 at 18:34

So this would go on to mean that it is more appropriate, based upon description, to use a surround of different composition rather than a continuous phase of thermobaric explosive, as the colliding shockwaves increase the reactivity with the air in the afterburn event.

That is interesting, I did not ever imagine this event helping the afterburn like this. Sounds as if the vacuum/pressure differences actually help to mix the fuel more intimately with the air.

[Edited on 11-7-2007 by Marsh]

TBX - 12-7-2007 at 00:17

Quote:

So this would go on to mean that it is more appropriate, based upon description, to use a surround of different composition rather than a continuous phase of thermobaric explosive, as the colliding shockwaves increase the reactivity with the air in the afterburn event.

This is basically the difference between a reactive surround explosive and a thermobaric weapon.

" There are four types of recognized enhanced-blast explosives: (1) Metallized Explosives. (2) Reactive Surround. (3) Fuel-Air. (4) Thermobaric."
http://das.cs.amedd.army.mil/PDF/J04_4_6.pdf

Also,I found these pictures interesting. The secondary combustion is clearly visible in both.
http://www.spiegel.de/img/0,1020,677918,00.jpg
http://pdn.philly.com/2005/05/13/mac/08.jpg

[Edited on 12-7-2007 by TBX]

[Edited on 12-7-2007 by TBX]

tito-o-mac - 12-7-2007 at 01:43

woah... someone called ThermoBaric eXplosives in a thermobaric forum!

Do u have any experience in thermobaric explosives?

www - 14-7-2007 at 13:35

just russian video.

Attachment: thermobar.wmv (515kB)
This file has been downloaded 1756 times

Marsh - 14-7-2007 at 14:36

Quote:

Originally posted by www
just russian video.

I'm trying to figure out what is being shown in the scene at 12 seconds into the video. It looks like a line of charges is simultaneously detonated on the ground, but to me they do not look thermobaric, simply incendiary. Maybe I am wrong for those that know Russian.

tito-o-mac - 14-7-2007 at 20:41

The vehicle is TOS-1 buratino. It's something like the Multiple Launch Rocket System, except it fires rounds of rocket-armed thermobaric missiles to level house block by block. Its currently deployed in Chechnya. As it is empties its payload of 30 rounds/15 s, its probably capable of doing that. Or it fires them at different angles. The rounds take longer to reach the ground when fired at higher angles. The rounds take less time when fired at lower angles. So if a computer was to do or the number crunching, that feat would have been possible. First fire a round at a highest angle, then slowly fire the rest of the rounds at a angle lower than the other, an they will at that the same time at the same target!

www - 14-7-2007 at 21:23

Quote:

Originally posted by Marsh

Quote:

Originally posted by www
just russian video.

Give me your E-mail. I will send this movie. It's on Russian. But, they are very nice data who don’t need translation

E-tech - 23-7-2007 at 12:42

Metallized explosives are more usefull in enhancing the blastwave of explosives used at high altitudes (where less air is available for the blast wave to work on/in)- it's why they see a lot of use in air-to-air missiles, but they would be pretty close to ideal, if it wasn't for the aluminum burning just a bit too fast (according to the design criteria set down by various researchers working on this type of ordnance). The reactive surround type of warhead I have heard described as a thin metal casing filled with powdered aluminum and nitrocellulose based propellants. With a bursting charge, this may be pretty effective, but most of the reactive surround warheads in use have powdered aluminum with a monopropellant liquid, or a flourine-based binder (that may or may not have an energetic binder). Separating the aluminum may provide a delay long enough to get a better effect on target, but, 4 pounds of metallized explosives at just over 100 meters will knock you over. I wish I could find a source for powdered aluminum where I am, so I could test the idea. The ordnance itself just isn't available to play with. Pity.
Has anyone found any info on the Russian thermobaric submunition? I have no russian language skills, but the things seem to be filled with an aluminized ANFO type mix. Any got anything new on them?

Boomer - 24-7-2007 at 08:20

"4 pounds of metallized explosives at just over 100 meters will knock you over"

Where did you read that? It takes 1 - 1.5 PSI to knock a person to the ground. Taking the cubic scaling law, this equals 1 - 1.5 million PSI from one meter, or 2 billion PSI at the charge radius. Doubtful...

Taken from the a.e.e archive (cant format it here, paste into excel):

Scaled Distance Overpressure Consequences
Z (ft-kg1/3) (psi)

3000-890 0.01-0.04 Minimum damage to glass panels
420-200 0.1-0.2 Typical window glass breakage
200-100 0.2-0.4 Minimum overpressure for debris and missile damage
82-41 0.5-1.1 Windows shattered, plaster cracked, minor damage to some buildings
44-32 1.0-1.5 Personnel knocked down
44-28 1.0-1.8 Panels of sheet metal buckled
44-24 1.0-2.2 Failure of wooden siding for conventional homes
28-20 1.8-2.9 Failure of walls constructed of concrete blocks or cinder blocks
20-16 2.9-4.4 Self-framing paneled buildings collapse
20-16 2.9-4.4 Oil storage tanks ruptured
16-12 4.4-7.3 Utility poles broken off
16-12 4.4-7.3 Serious damage to buildings with structural steel framework
11-10 10-12 Probable total destruction of most buildings
15-9.0 5.1-4.5 Eardrum rupture
14-11 5.8-8.7 Reinforced concrete structures severely damaged
14-11 5.8-8.7 Railroad cars overturned
6.7-4.5 29-72 Lung damage
3.8-2.7 102-218 Lethality
2.4-1.9 290-435 Crater formation in average soil

[Edited on by Boomer]

[Edited on by Boomer]

nitro-genes - 24-7-2007 at 09:59

With all fuel-air explosives, including thermobaric charges you can't simply take the charge radius for the detonation pressures produced. It doesn't react in a C-J like manner like an ideal explosive, instead the burster charge disperses the fuel to obtain a volume a 100-1000 fold of the charge volume itself in order to react with the atmospheric oxygen. That is why the total energy released can be so much higher than with conventional explosives and can do more work over a greater distance.

[Edited on by nitro-genes]

Boomer - 25-7-2007 at 07:32

The 2 billion PSI was just for comparison with CJ shockwaves. Take the 1.5 million PSI at 1 meter if you want. A 2-meter fireball is likely in the right order, still a million PSI cannot be reached at the outer surface of a fuel/air cloud.

The number simply does not sound right, there are people here (or on E+W) who stood much closer to a similar charge, the closest I remember is either 7 or 10 meters from 10 kilos of ammonal. If you are knocked over at 100m, these people would have been thrown quite a distance, or - if already on the ground - crushed to death. One tenth the distance means between 100 and 1000 times the peak pressure, depending whether it's still a hot expanding gas cloud (cubic rule) or down to a sound wave (square rule).

Marsh - 25-7-2007 at 08:25

7-10 meters from 10kilos of ammonal? Sounds a bit close if you ask me.

Was this placed above the ground with no barrier between them?

Boomer - 26-7-2007 at 07:22

Too close for my taste also, even with earplugs. From what I remember the charge was in a paint bucket, inside a rotten tree, person was out of fragment path (another big tree or boulder, don't remember).
The closest I woul like to be from 10 kilos would be 20-25 meters, the shock drops more than one expects with distance. Less than 100g plastique gave me a much harder punch from 2.5 meters than 3 pounds on ANFO from 15m (both times crouching behind a concrete wall).

About the energy content of thermobaric/enhanced blast/... explosives, it can be a few times that of conventional HEs. The limit are FEAs with only a fragment of the charge weight HE, most of it fuel. Just compare the 4kJ/kg of TNT with the ~40kJ of petrol. The usual fuels like ethylene/propyleneoxide are lower than pure hydrocarbons, but not that much lower.

E-tech - 27-7-2007 at 00:42

I was wearing earplugs, and safety glasses, body armor, and an M-4 rifle (can you guess where this happened? Hint: think sand). I didn't read those numbers- I fired the weapon (SMAW-NE) myself, and we used a range finder on the house I hit to confirm the distance. One thing we noticed was that people in armor were more affected by the blast than those not wearing any. The trauma plate acts like a nice flat surface for the pressure to act on; Thermobaric weapons make your body armor work against you.

TBX - 27-7-2007 at 17:36

Here's a short video of the Hellfire Metal Augmented Charge being tested.

https://mfcbastion.external.lmco.com/mfc/videolibrary/HELLFI...

tito-o-mac - 5-8-2007 at 00:21

Yeah, they say that wearing bullet proof armour worsens the damage as it increases the surface area of the human to get hit by the blast wave. Below is a question I was still pondering on:

Say, a thermobaric explosive is one that "disperses the cloud the and ignites it with the same charge" how does one do that anyway? Is it something like a RPG ignition where a piezoelectric fuze is used? E.g. when the charge goes off, the liquid is dispersed and the sensitive piezolectric fuze ignites the cloud right after the first blast goes off?

Nerro - 5-8-2007 at 01:06

Well, I read up on it years ago but I remember that finely spread Al had something to do with it in some types of thermobaric explosives. The Al would ignite as soon as enough oxygen was available and set off the kerosene or whatever combustible was spread. It looked really effective in the video and it ensures that ignition always happens under the same conditions which makes a lot of sense.

nitro-genes - 5-8-2007 at 14:37

Aluminium powder doesn't need to react with oxygen, as most of the aluminium will be oxidized by the water, CO2, CO etc released during the detonation. The aluminium particles accellerate along with the detonation products, with a burntime determined mostly by the particle size of the aluminium. For igniting a dispersed vapour cloud, larger particle sizes do just as well or even better than expensive high mesh grades. Especially titanium keeps burning very long...

Anyway, I was thinking about these surround EBX charges in which HMTD used AN as the oxidizer additive. AN has a low decomposition temp, good oxygen balance and stability and is very cheap as well, the only disadvantage is that it makes the charge very sensitive to moisture.

How about about using urea nitrate instead? Slightly lower decomposition temp, higher density, not hygroscopic and easy to come by. Acidity is much higher though and could prove to be a problem in combination with the aluminium when not recrystallized to remove any remaining nitric acid impurities. With completely dry UN this shouldn't be a problem though...

Does anyone has experience with urea nitrate in combination with aluminium powder?

Another option would be to use aluminized AN-emulsions for the surround, maybe this is what was meant with the ANFO thermobarics mentioned earlier in this topic. Reverse emulsions are water resistant and form a soft pasty substance when warm, which allows the aluminium to be mixed in easily, although density will not be as high as for an plasticized and rolled surround composition.

[Edited on by nitro-genes]

E-tech - 6-8-2007 at 06:11

A better choice would be the perchlorate salts. It's what is used in the China Lake wepons research facility patent for a castable thermobaric explosive. One of the inventors, May L. Chan was (I believe) the leader of the project that devised the filler for the BLU-118 thermobaric bomb. The annular ("surround") design in the castable explosive patent would be perfect for rocket/missile warheads.
It's likely that the Russians are using AN emulsions in a few of their thermobaric designs (low cost, and they don't have a problem with storing liquids in a warhead like the U.S. does), but, no one can find the proportions they are using.

E-tech - 6-8-2007 at 12:55

oops- Anh Duong was the researcher in charge of the BLU-118 project, and works on the east coast. May L Chan is on the west coast.

franklyn - 9-8-2007 at 19:59

Granted a storable stable unreactive and insensitive energetic substance is a
requirment for deployable items of ordnance. This is only an idea , Triethylaluminum
is utilized for special purposes , metal ethoxide's are much less reactive , so why
not blend the two. Their detonation would produce incandescent alumina dust
and Butane gas . ( C2H5O )3Al + ( C2H5 )3Al -> Al2O3 + 3 C4H10

.

tito-o-mac - 10-8-2007 at 00:42

So what is the best or most suitable metalized powder or liquid for FAE or TBX explosives? I think the Russian's usage of AN combination is a good choice as it produces a loot of excess oxygen, making igniting conditions favourable. Doesn't ANNM do just the same?

[Edited on 10-8-2007 by tito-o-mac]

E-tech - 12-8-2007 at 14:25

Actually, triethylaluminum is already in use- as a flame weapon- the M202 "FLASH" incendiary rocket uses it. It's pyrophoric, so storage is a big problem (I've never seen one of these rockets used in combat- effective, but politically nasty. And, damaging the container it comes in could ignite the thing), plus, the U.S. doesn't like using liquids in it's ordnance- even the most durable design will likely start leaking within ten years.
There is no "most suitable metalized powder or liquid"- it all depends on the design of the overall ordnance system. Even the size of the powdered aluminum has to be changed, depending on the size of explosive charge it is used with (check "effects of scale on the blast wave from a metalized explosive"- a google search should get the paper, just enter the title).

tito-o-mac - 15-8-2007 at 06:08

Hey, check out this HMTD hexamine thermobaric bomb this guy made. I'm not convinced though: http://www.youtube.com/watch?v=dhZEeUsTrNM

Boomer - 16-8-2007 at 09:09

He's an idiot. It's just a primary (-151% OB!) diluted with an inert that happens to be flammable. Like dynamite with twice as much wood pulp. It would not even detonate if it was no primary.

Plus, he seems to use it like a fun snap (torpedo), there must have been some ball bearings or stones in that wrap-up to explode on impact. About as unsafe as it can get.... :mad:

Sauron - 12-9-2007 at 06:18

The Russians just detonated what they are calling the most powerful thermobaric airdropped munition ever. According to Russian news sources, the bomb has four times the yield of the largest such US device (MOAB) at 44 tons vs 11 tons TNT equivalence, yet the explosive is about 95% of the mass of the explosive used in the US device.

Sounds like warmed over Cold War rhetoric. They are claimning a major breakthrough in thermobaric explosives technology.

This comes at a time when indeed relations between Washington and the Kremlin are at a post 1990 nadir.

Any beef on this bun?

YT2095 - 12-9-2007 at 06:37

yeah I just posted about this on my Home Forum, here`s some links:

http://www.reuters.com/article/worldNews/idUSL11559523200709...
http://www.freemarketnews.com/WorldNews.asp?nid=48780
http://www.1tv.ru/owa/win/ort6_videopage.main?sender=news&am...

Axt - 12-9-2007 at 06:52

Quote:

Originally posted by Sauron
the bomb has four times the yield of the largest such US device (MOAB) at 44 tons vs 11 tons TNT equivalence, yet the explosive is about 95% of the mass of the explosive used in the US device.

MOAB is an aluminised HE thermobaric, composition H6 which is 29.5% TNT, 44% RDX, 21% Al (remainder being inerts), whereas the russian bomb is a true FAE. See youtube movie at 25sec.

http://youtube.com/watch?v=iCmA7xFPIdU

edit: Movie above is same as last link YT2095 posted, which is better quality.

[Edited on 13-9-2007 by Axt]

Sauron - 12-9-2007 at 07:17

IMO the claims of equivalence to a nuclear weapon are absurd; off by 3 to 7 orders of magnitude. Pure propaganda.

YT2095 - 12-9-2007 at 07:27

are you Mental? ever heard of Battle Field "Tactical" nukes? Tank launched shell or MLRS types?

Boomer - 12-9-2007 at 08:28

Yeah, they DO go down to 50-100 tons TNT (= only 1- 2 times the russian FAE!), usually adjustable via detonation (implosion) pattern.

Still what most people think when they hear nuklear is more like 50-100 kilotons...

Sauron - 12-9-2007 at 09:37

The Russian general on television was not quoted as comparing his new toy to a TACTICAL nuke. Besides those artillery launched devices are mostly ERWs anyway that were designed to kill tank crews.

No, he compared his FAE to a NUKE and clearly intended his audience (the great unwashed) to think of something from Hiroshima/Nagasaki size (8-12 KILOtons) to thermonuclear strategic (20-100 MEGAtons or more) Hence 3-7 orders of magnitude.

Clearly his remark was intended to intimidate his audience. It was propaganda and it was deceptive.

[Edited on 13-9-2007 by Sauron]

franklyn - 12-9-2007 at 10:38

You can't make too little of this considering its capability. Knocking down masonry is
a first for this type of ordnance. It also fits within a Backfire bomber so it is compact.
Reniniscent of BLU-82 http://en.wikipedia.org/wiki/BLU-82 which has always been
compared to the effects of atom bombs in its more limited area of devastation , and
the GBU-43 http://en.wikipedia.org/wiki/GBU-43_Massive_Ordnance_Air_Bla...
which is also shown in action in this video for comparison . - Click image for video -

[IMG]http://www.reuters.com/resources/r/?m=02&d=20070912&t=2&i=1702594&w=r=2007-09-12T153602Z_01_L11559523_RTRUKOP_0_PICTURE0[/IMG]

Sauron - 12-9-2007 at 10:41

Maybe the Kremlin plans to bomb Georgia (their Georgia not ours) as the Georgians say they already did a few weeks ago. Or Chechnya. Certainly they don'w want to get back into an expensive arms race with us! not when most of their troops haven't had a paycheck in some time, neither have their academics.

Sure they are tee'd off about the missile defense initiative, but they aren't going to provoke us into cutting off all the aid we have been giving them over that. A little saber rattling like this, fine, Putin will calm down and Bush won't be in office much longer. What's to worry?

I spent many years in Washington reading annual Pentagon reports on the Soviet military, so I am sure the USAF will be asking for more RDT&E budget because of this new Russian toy. Yawn.

YT2095 - 12-9-2007 at 10:46

yes indeed YAWN!

you are a man with a finger in EVERY single pie on the planet, that is quite evident from you speeches.

now back to Reality, yes it Comparable to a tactical "battle field" NUKE (if you want to put it in caps as you did).

[Edited on 12-9-2007 by YT2095]

Sauron - 12-9-2007 at 11:05

To be specific about realities, I lived in Arlington and Alexandria Virginia, just across the river from DC, and close to the Pentagon, throughout the Reagan years and was a defense consultant, contributing editor for a major defense journal, and writer and lecturer to conferences of the American Defense Preparedness Association (formerly American Ordnance Association) and the International Strategic Studies Association. I was a regular faculty member of the annual STRATEGY Conferences in Washington throughout that period, and also at more specialized conferences such as the Special Operations one at Artillery Hall, London 1986. I relocated to Thailand in 1989 and assumed the post of ASEAN Bureau Chief for a DC-based defense-intelligence newsletter that covers the Islamic world, a position I still hold, that makes me responsible for ten nations with a combined population of about half a billion.

There's a book on the ftp site with my photo on the front cover, and I'm not the one who uploaded it, either.

So, sirrah, since you choose to be a sarcastic SOB, kindly recite your last thirty odd years.

Or does modesty prevent you from describing your meteoric rise as a British defense intellectual?

Some of us have been there and done that, son. Don't ridicule someone about whom you know approximately nothing. You'll lose.

[Edited on 13-9-2007 by Sauron]

HMTD - 12-9-2007 at 13:22

Here's the episode that was shown on Russian First Chanel yesterday (the same is on YouTube, but this has better quality)
Here is original video (15 Mbytes)

http://rapidshare.com/files/54994339/FOAB_TVRip_.avi.html

Here is English subtittles I've tried to make:

http://rapidshare.com/files/55239093/FOAB_TVRip_.srt.html

PS. This bomb is probably like large barrel with paraсhute, MOAB has it's own navigation system... That's why FOAB is probably relatively "cheap".

tito-o-mac - 14-9-2007 at 07:44

Quote:

Originally posted by Axt

MOAB is an aluminised HE thermobaric, composition H6 which is 29.5% TNT, 44% RDX, 21% Al (remainder being inerts), whereas the russian bomb is a true FAE.
[Edited on 13-9-2007 by Axt]

Axt, I thought the MOAB just a normal explosive? I've never heard anything of a thermobaric MOAB. It produces a massive air blast because it detonates just directly above the target.

The daisy cutter is another story. Contrary to some published claims, it most certainly is not an Ethylene-Oxide Fuel-Air Explosive (FAE). Some initial reports had stated that this replacement for the BLU-82 bomb uses more of the slurry of ammonium nitrate and powdered aluminum used in the BLU-82. Other reports indicated that the MOAB might use tritonal explosive as opposed to the gelled slurry explosive of the BLU-82. Contrary to some reports, it is not capable of deep ground penetration.

The only FAEs in the American arsenal is probably the Hellfire thermobaric, the SMAW-NE. More on the MOAB: http://www.youtube.com/watch?v=9aBfOOo-n5k

[Edited on 14-9-2007 by tito-o-mac]

[Edited on 14-9-2007 by tito-o-mac]

Axt - 14-9-2007 at 10:39

<a href="http://www.fas.org/man/dod-101/sys/smart/moab.pdf">US airforce report</a> mentions H6 being used in MOAB, and an <a href="http://dspace.dsto.defence.gov.au/dspace/bitstream/1947/3621/1/DSTO-TN-0049%20PR.pdf">Australian military report</a> gives its composition as I stated. Its in full -

TNT 29.5%
Aluminium 21.0%
RDX & Nitrocellulose (RDX usually Grade B) 44.0%
Calcium Chloride 0.5%
Wax 5.0%

Theres no hard definition as to what constitutes a "thermobaric" weapon other then being a funky term for an explosive enhanced for heat and pressure. With 21% it may be a bit light on Al, call it an enhanced blast explosive if you want a more general term. This is the Talley definition-

<u>Thermobaric Compositions</u>
• Thermobaric Compositions are Fuel Rich High Explosives that are Enhanced through Aerobic Combustion in the Third Detonation Event
– Performance Enhancement Primarily Achieved by Addition of
Excess Metals to Explosive Composition
• Aluminum and Magnesium are Primary Metals of Choice
– Third Event Enhanced by Aerobic Combustion of Fuel Rich
Species in Shock Front, ie:
• 4Al + 3O2 ==> 2Al2O3
• 2Mg + O2 ==> 2MgO
• 2H2 + O2 ==> 2H2O
• 2CO + O2 ==> 2CO2
• Thermobaric Compositions are a Hybrid Explosive Composition having
the Characteristics of both a High Explosive and a Fuel/Air Explosive
– Compositions are Generally Detonable
• Talley is Currently Working on a High Heat Output Formulation
that may result in a non-detonable “Thermobaric” Composition
– Compositions may be Liquid or Solid
• Original Russian Formulations were Liquid
• More Recent US Formulations are Solid
– Compositions are Generally Less Sensitive than Classical High Explosives
• Highly Metallized Standard High Explosives meet the Definition of a Thermobaric Composition

[Edited on 15-9-2007 by Axt]

E-tech - 26-9-2007 at 13:00

The SMAW-NE and the hellfire are not FAE warheads. They are thermobaric designs- no gases or liquid fuels are used.
More sabre rattling- very likely. They have also re-started their strategic bomber flights around places like Norway.
H-6 is used in things like cratering charges or SAM warheads for it's enhanced blast effect. In that way, it could be considered thermobaric, but, no government uses it in anything that they label as thermobaric. All the new fills called that have around 25-30% aluminum in them.
I remember during his first term, Bush mentioned wanting to re-arm the nuclear force with smaller (kinder friendlier) nuclear weapons. Ones capable of finding use in low-intensity conflict. Of course, almost everyone went crazy over it being nuclear. Perhaps these MOAB/FOAB type of weapons are the new, politically acceptable deterrent for countries we would prefer to nuke, but can't because of the world's opinion. If Soviet Georgia had been hit with this type of weapon, it would have shown up on satellite recon, and the story would have been published in the U.S.
It will be interesting to see what the russian model is filled with. Info will leak out over time. Stay tuned.

franklyn - 26-9-2007 at 13:57

Naming specific compositions of the handful of militarilly applicable explosive compounds
serves to make them mnemonically distinguishable from one another. The only difference
is how much of each ingredient is present in the recipe for that ordnance item. H 6 ,
Torpex , H B X , and some others I probably am overlooking , are all made up of R D X and
T N T blends enhanced with Aluminum. The original high heat effect explosive was Tritonal
( not Tritonol ) T N T mixed with Aluminum. This I guess fell out of favor because better
explosions ( more brisant ) result from those presently utilized.

http://www.sciencemadness.org/talk/viewthread.php?tid=4080&a...

Thermobaric Fuel Additives
Metal and High Energy Non-Metal Fuel Additives
• Boron, Aluminum, and Hydrocarbons Provide Highest Practical
Fuel Energy Density Based on Mass and Volume

Fuel Additive Hcomb (cal/g) Hcomb (cal/cc)
Boron . . . . . . . . . . .13,970 . . . . . . . .33,100
Aluminum . . . . . . . . 7,560 . . . . . . . .20,410
Titanium . . . . . . . . . 4,260 . . . . . . . .19,130
Zirconium . . . . . . . . 2,880 . . . . . . . .18,390
Silicon . . . . . . . . . . . 7,320 . . . . . . . .17,720
Carbon * . . . . . . . . . 7,840 . . . . . . . .13,820
Magnesium . . . . . . . 6,020 . . . . . . . .10,530
Hydrocarbons * . . . 10,000 . . . . . . . . 9,000

* Assumes combustion to CO2.

Kerosene 43 MJ/kg
Methane 50 MJ/kg
Hydrogen 120 MJ/kg

.

KemiRockarFett - 28-3-2008 at 06:28

Quote:

Originally posted by Boomer
He's an idiot. It's just a primary (-151% OB!) diluted with an inert that happens to be flammable. Like dynamite with twice as much wood pulp. It would not even detonate if it was no primary.

Plus, he seems to use it like a fun snap (torpedo), there must have been some ball bearings or stones in that wrap-up to explode on impact. About as unsafe as it can get.... :mad:

Offcourse it was a dangerous experiment. But still its a thermobaric device. No visible carbon dust. And afterburning of the fuel as visible in the slow motion of the video.
Compare with the det. of TNT giving a black carbon cloud.
It would be interesting to put an Al-rich high explosive in the centre of a can full with carbon powder. If enough Al is inmixed the rest heat will set off the carbon than its mixed with air.
W

E-tech - 3-4-2008 at 12:35

Carbon powders have been tested (Talley defense systems ran the test), but were found to have lower levels of energy than powdered metals. The biggest problem is getting the cloud of metal powder to expand from the explosion of a central bursting charge, while still retaining enough heat to ignite once it reaches enough oxygen to react with. Unless something is added to the powdered Al, it will cool itself as the cloud expands, and it will be wasted. Monopropellant liquids and flourine compounds are used as binders to sensitize the Al in most designs.

KemiRockarFett - 4-4-2008 at 03:49

Quote:

Originally posted by E-tech
Carbon powders have been tested (Talley defense systems ran the test), but were found to have lower levels of energy than powdered metals. The biggest problem is getting the cloud of metal powder to expand from the explosion of a central bursting charge, while still retaining enough heat to ignite once it reaches enough oxygen to react with. Unless something is added to the powdered Al, it will cool itself as the cloud expands, and it will be wasted. Monopropellant liquids and flourine compounds are used as binders to sensitize the Al in most designs.

Al reacts with H20 and N2 created under the detonationprocess, oxygen is not necesarry at all. Its probably better to have more metal in the edges of the explosive matrix to have a good VoD in the center helping the metal inmixed composition to detonate with an higher VoD. Even if the mix is thermobaric its energy per time that matters. And the main point with thermobaric is to overfuel the charges to get more energy out.
Offcourse metals give more energy but if you dont have a clever method of producing fine metal powder or a lot of money to buy these you may want to use sheep carbon.
I think that metal together with carbon can work.
I saw the Talley shit and is not impressed.

E-tech - 8-4-2008 at 20:26

True- oxygen isn't required, and N2 will react just as well, but, a truly better result can be had with Fluorine based compounds.
Overfueling the charge is nowhere near enough. That would only provide an increase in the levels of heat (do a search on the "la mon massacre" in Ireland- 1.5lbs of semtex launched 4-5gal of petrol into a crowded restaraunt- nasty). The main point with thermobaric charges is to overfuel at a time that extends the pressure impulse on the target. Tailoring the size of the charge, and the size of the Al particles, so they ignite at the right time, is not so easy. The size of the Al particles, and the overall charge size, the thickness and materials of the warhead casing, smong others, all fit into the design. Overfueling the charge will make a blast-incendiary device- designing it properly will create a true thermobaric.

KemiRockarFett - 10-4-2008 at 11:15

Quote:

Originally posted by E-tech
True- oxygen isn't required, and N2 will react just as well, but, a truly better result can be had with Fluorine based compounds.
Overfueling the charge is nowhere near enough. That would only provide an increase in the levels of heat (do a search on the "la mon massacre" in Ireland- 1.5lbs of semtex launched 4-5gal of petrol into a crowded restaraunt- nasty). The main point with thermobaric charges is to overfuel at a time that extends the pressure impulse on the target. Tailoring the size of the charge, and the size of the Al particles, so they ignite at the right time, is not so easy. The size of the Al particles, and the overall charge size, the thickness and materials of the warhead casing, smong others, all fit into the design. Overfueling the charge will make a blast-incendiary device- designing it properly will create a true thermobaric.

Al and Mg will be into the reaction directly after the detonation of the thermobaric mixture than the H20 and N2 will start to react with the metal, the size of the particles affect the time of this process. The ignition of the active metal than proceed in the atmospere.

legnanu - 14-7-2008 at 18:32

Yesterday I dreamed in synthesizing some booster charges with a decent termobaric power and a generous shelf life (store at least 2 years?) in plasticized cylindrical forms.

I discarted RDX for the laborious of their optimal sinth (acid distillation/purification, elimination NOxx, etc..) and because I find easier PETN and/or ETN. I have left little PETN and what I have without problems is ETN. Then I have thought the following thing...

Pure ETN(71%) + Pure PETN(6%) + AL(12%) (in thinnest invaluable powder) + Diphenylamine(1%) + Styrene Butadiene Rubber(10%).

What do you think ? would you adjust the proportions in some other (optimal) way ?

ShadowWarrior4444 - 14-7-2008 at 19:56

Quote:

Originally posted by legnanu
Yesterday I dreamed in synthesizing some booster charges with a decent termobaric power and a generous shelf life (store at least 2 years?) in plasticized cylindrical forms.

I discarted RDX for the laborious of their optimal sinth (acid distillation/purification, elimination NOxx, etc..) and because I find easier PETN and/or ETN. I have left little PETN and what I have without problems is ETN. Then I have thought the following thing...

Pure ETN(71%) + Pure PETN(6%) + AL(12%) (in thinnest invaluable powder) + Diphenylamine(1%) + Styrene Butadiene Rubber(10%).

What do you think ? would you adjust the proportions in some other (optimal) way ?

ETN isn’t a favorite for storage--its quite shock sensitive and tends to breakdown significantly faster than PETN; as such, I'd put the shelf life that mixture at 3-6 months. Provided that they’re very stable shelves.

legnanu - 15-7-2008 at 03:08

In spite of it, what do you think of the possible explosive properties?

franklyn - 13-10-2012 at 09:27

Quote: Originally posted by E-tech

There are no single-component thermobaric explosives, they are all mixes using Al, or fuels surrounding the charge. The isopropyl nitrate is used as an energetic binder to insure that all the aluminum fuel is consumed; It won't do much on it's own as far as thermobaric effects are concerned.
In other news- the Russians have another thermobaric mix that does use AN. It also includes Al and isopropyl nitrate, but the exact mix is not known. Military Parade Publishing (a Russian arms catalog they print) has pics of what is sold as a thermobaric submunition; it is said to hold 22 pounds of the mix. It looks like they are forgoing the weight/volume efficiency of explosives like HMX in order to obtain better far-field effects. The submunition looks like a coffee can on a parachute- still wouldn't like to get caught in a field of them, though.
I've worked with small (100gram) charges of RDX explosives with a thermite surround, and found the effects to be noticably different; materials pushed farther away and scorched whereas the no surround charge barely moved the objects around it. I haven't had a chance to test the really noticable (by the US military) effect of the thermobaric charge- the ability to go around corners. During one of it's first few tests, the BLU-118/B was found to be capable of sending it's blast/heat waves around a horshoe- shaped bend in a test tunnel complex in the Nevada desert. It's likely nothing more than a heat-driven pressure spike, but the ability to control or "bounce" a blast wave around a corner sounds like a nice challenge, especially once you get "mach stem" effects mastered. Thanks for the -135 mix. Where did you find it?

Compatibility Of Thermobaric Mixtures Based On Isopropyl Nitrate And Metal Powders
Interesting paper for the wealth of information provided on Isopropyl Nitrate
http://www.vti.mod.gov.rs/ntp/rad2004/34-04/terz/terz.pdf
Related thread http://www.sciencemadness.org/talk/viewthread.php?tid=14492

" The isopropyl nitrate is used as an energetic binder to insure that all the aluminum fuel is consumed "
- or rather promotes ignition of the Aluminum it coats.

" Russians have another thermobaric mix that does use AN.
It also includes Al and isopropyl nitrate, but the exact mix is not known."
- Applied chemistry can resolve the question since it can't be too far from stoichiometric proportions.

2 C3H7NO3 + 7 NH4NO3 + 14 Al => 7 Al2O3 + 6 CO + 8 N2 + 21 H2
. . . . I P N . . . . . . . . .A N . . . . . . . . |
. . . . . .9 . . . . . . . . . . .2 5 . . . . . . . 1 6 . . . parts by weight

The procedure would be to mix Aluminum into Isopropyl Nitrate then mix with Ammonium Nitrate.
The materials are very shock insensitive so a propellant could be applied for dispersal and a delay
high order booster would detonate the aerosol. See _
http://www.reuters.com/resources/flash/embedvideo.swf?editio...

________________________________________________

Related threads
http://www.sciencemadness.org/talk/viewthread.php?tid=7762

http://www.sciencemadness.org/talk/viewthread.php?tid=21691

[Edited on 13-10-2012 by franklyn]

franklyn - 16-10-2012 at 10:18

I mistook the mixture as an FAE rather than Thermobaric ( topic of this thread )
In the latter case the amount of ammonium nitrate can be much less serving to
disperse the remainder of unburned fuel in a manner similar to a BLEVE.

.

Refinery - 1-4-2014 at 03:47

http://www.dtic.mil/ndia/2012IMEM/13879ervin8B.pdf

Does anyone know the composition of this thermobaric mixture? I would guess it'd be around 70-75% RDX/PETN and 20-25% Al powder and rest are binders..

Dany - 1-4-2014 at 05:26

Quote: Originally posted by Refinery

http://www.dtic.mil/ndia/2012IMEM/13879ervin8B.pdf

Does anyone know the composition of this thermobaric mixture? I would guess it'd be around 70-75% RDX/PETN and 20-25% Al powder and rest are binders..

PBXIH-18 is an HMX/Al based thermobaric explosive. The binder is an acrylic acid ester called HyTemp plasticized with Dioctyl adipate (DOA).

PBXIH-18: HMW/Al/HyTemp/DOA. The density is 1.91 g/cm³.

see Table 1 page 5 in this conference paper:

http://www.dtic.mil/ndia/2004guns/thurs/rockets/johnson.pdf

Dany.

NM explosive Thermobaric?

Melmoth - 20-10-2014 at 11:28

We had a discussion about definition today. One stated a amine sensitised nitromethane explosive would have thermobaric characteristics in my opinion this is only the case with addition of AL.

Any thoughts on this?

careysub - 20-10-2014 at 15:47

Quote: Originally posted by Melmoth

We had a discussion about definition today. One stated a amine sensitised nitromethane explosive would have thermobaric characteristics in my opinion this is only the case with addition of AL.

Any thoughts on this?

Nitromethane is a high gas volume high explosive, and would produce a relatively strong air blast compared to TNT-type traditional military explosives.

But it is definitely not any kind of thermobaric explosive, which specifically refers to excess high energy metal particles that burn in air to create some combination of high temperatures and/or long low pressure blast against soft targets (designs differ on which is emphasized).