Myself, I agree that CNN just got this wrong. Many otherwise competent reporters fail to distinguish between semi-automatic rifles and automatic rifles, so the difference between a high-explosive weapon and a thermobaric one is likely lost on CNN’s reporter. Moreover, the CNN article defines a thermobaric weapon as one that produces both heat and pressure, which is taking the Greek etymology of the word a bit literally, IMHO. By that definition, a hairdryer is a thermobaric weapon. It’s clear to me that the reporter doesn’t understand what a thermobaric weapon is.
I hadn’t considered the aluminum content in H6 the way you did, and I appreciate your pointing it out. It almost sounds as though you’re suggesting that the aluminum in H6 was intended to be burned by the oxygen created when the conventional explosive decomposed the water around it in naval applications. Is that right?
I have to respectfully disagree, thought, that the MOAB bomb is thermobaric by any useful definition of that term. I take your point that it includes more fuel than oxygen, but by that definition of “thermobaric,” any explosive that runs a little on the rich side of stoichiometric is a thermobaric weapon. If Timothy McVeigh went a little heavy on the fuel oil in his ANFO-filled truck, then he built a thermobaric weapon according to this definition.
The brisance and total energy of a MOAB detonation may well be affected by the aluminum content, but the weapon is not primarily a fuel/air device.
It seems (to me at least) that a reasonable definition of “thermobaric” requires dispersal of the fuel and mixing with atmospheric oxygen prior to ignition. This definition would mean MOAB, incindiary munitions, white phosphorus weapons and slightly-rich ANFO bombs are not thermobaric, while the Russian Shmel and FOAB are. I’d argue that the metal-augmented charge Hellfire is a hybrid weapon. It’s not a perfect definition, but at least it doesn’t suggest that any explosive with a little more fuel than oxidizer is thermobaric.
I’m not sure of the need for the term ‘thermobaric’. Fuel Air Explosives were around for years before the other term was used or before I ever heard it anyway, and by your definition FAE and ‘thermobaric’ would be pretty much synonymous. And OTOH as mentioned the MAC warhead of AGM-114N missiles is called ‘thermobaric’ in official sources.
It’s just a somewhat ambiguous term. I agree though it’s questionable to call an H6 filled bomb ‘thermobaric’ if it’s to mean much, just pointing out it’s not 100% untrue.
Curiously, my initial thought on the definition of a thermobaric weapon from first principles would include nuclear weapons. They convert heat into pressure. High explosives mostly create pressure by decomposition. Heat is arguably a secondary by-product. (You could no doubt create an endothermic high explosive.) So they are not thermobaric. Ordinary explosives create pressure from the heat of an exothermic reaction. So by the most simple definition they are also thermobaric. Fuel-air weapons are clearly thermobaric as they involve an exothermic reaction that creates the pressure.
My conclusion is that the word is ill chosen for purpose.
Yes, I agree. I have a hunch that “thermobaric” became a term of art in English partly because it sounds fancier than “fuel/air explosive,” sort of in the same way many police officers can’t bear to say they pulled over a “car” and instead refer to pulling over a “vehicle.” And yes, I think FAE and “thermobaric” are synonymous. Nearly all weapons that go “bang” near their targets involve both heat and pressure, so either “thermobaric” means “a weapon that goes bang near the target” (a definition so broad as to be useless) or it’s a 50-cent word for fuel-air explosive (which makes much more sense to me personally).
I appreciate your pointing out the aluminum component in H6…you’re right that that lends a kernel of truth to CNN’s assertion.
As stated above, I agree that "thermobaric"doesn’t mean much in the context of explosives. But I’m not sure what you mean when you say that “heat is arguably a secondary byproduct” of high explosives. Both ordinary and high explosives produce heat directly and produce pressure by decomposition. Then the heat expands the local air, adding to the pressure effects. And of course, compressing local air heats it as well. These effects are all intertwined, and I have a hard time understanding heat as “a secondary byproduct” in this context.
Furthermore, nuclear weapons emit both kinetic energy (heat) and electromagnetic energy (radiation, including X-rays). The X-ray emissions are absorbed by material air, rocks, whatever) near the weapon and converted into heat. Again, pressure and heat are intertwined and I’m not sure what you mean when you say that nuclear weapons convert pressure into heat. Pressure and heat are deeply intertwined; there’s no heatless pressure that is then converted into less pressure and more heat. Also, your statement implies that a nuclear weapon detonated in space would emit no heat because there’s no pressure medium. Maybe I’m misunderstanding you.
And can you elaborate on your endothermic high explosive idea? I’ve not heard of anything like that, and I have a hard time understanding how that would work chemically. Can you explain?
Sorry I was being a bit obscure. By “by-product” heat I meant heat that wasn’t part of the hot decomposition products, but just heat going into the the surrounding air - heating that to add to the pressure. The point being that my literal interpretation of “thermobaric” means a weapon that heats the air to create the pressure, rather than a device that creates its own hot gas. Perhaps I should have started from this point of view. I’m being bloody mindedly literal here.
I didn’t. I said they convert heat into pressure. Which is very loose. They radiate energy that heats the air and thus the pressure rises.
Yes, this is simply the gas laws.
A nuke detonated in space would produce no pressure. Lots of energy flux. Absent anything to adsorb it, not actually any heat, the energy just radiates away. In the context of a thermobaric weapon a nuke seems to exactly fit the literal view of the term. This weapon heats the surrounding gas and it is that hot gas that creates the explosive pressure. It isn’t hot gas evolved from the device itself.
It was a throwaway thought. High explosives are of course very exothermic - that is where the energy comes from. But it struck me that you could concoct a compound that was unstable enough that it would want to decompose, but would decompose into little more than some cold gas. Not exactly an explosive you could blow anything up with, but maybe an interesting curiosity.