I have read several stuff about fuel-air or thermobaric explosives (FAE) and I think they're used especially in an anti-personnel role. Compared to high explosives (HE) they generate much more energy (3-4 times) released in a much longer time with lower peak pressure. This has clear effects in some circumstances: HE is clearly superior in fragmentation while FAE is more deadly with the blast itself against human targets. But what is the effect against infrastructures? Or - in other words - what is more important for destroying buildings, peak pressure or energy?
Fuel-Air Explosive vs. High Explosive
- Thread starter MM90
- Start date
Always remember that pressure and heat are both forms of energy and that high explosives and thermobarics both produce heat and pressure when they detonate. The manner in which they produce these effects is what differentiates them. Thermobarics produce less heat and pressure than high explosives, but for a longer duration.
It is also going to depend on what kind of structure you are referring to and what the atmospheric conditions are. 2 psi to 5 psi is sufficient to destroy most buildings not made of poured and reinforced concrete. A large Thermobaric device can resemble a small nuclear detonation in its effects, minus radiation. With an overpressure within the detonation reaching up to 430 psi and temperatures of 4,500 to 5,400 °F, it will have no problems destroying these types of structures. The vacuum that comes after the detonation is nearly as deadly as the initial blast wave. Because the pressure wave is of a longer duration, Thermobarics are typically more destructive then are high explosives.
Much smaller devices are now being fielded. Russia has several small scale weapons of this type, some as small as 8oz and with a kill radius of 9.8 feet. The RPO-M Rocket launcher has a thermobaric warhead with similar destructive capabilities as a 152 mm High explosive fragmentation artillery shell.
The main advantages of thermobarics is that they do not need to carry their own oxidizer, like conventional explosives. This gives you a larger explosive force in a smaller package. They must be able to use atmospheric oxygen to detonate though and because of this they cannot be used underwater, in space, or even in some adverse weather or at high altitude, but because they use the surrounding oxygen, they can be useful in clearing tunnels and bunkers whereas the blast effects cannot reach deep enough, the lack of oxygen and resulting pressure front and vacuum serve to kill the occupants and destroy equipment deep inside the structure while not destroying the structure itself.
The use of these weapons in a urban setting are cause for some concern. Due to the multiple threat nature of the weapon, it is particularly difficult for civilians to take shelter from them. A human rights watch report from 2001 states:
"The [blast] kill mechanism against living targets is unique–and unpleasant…. What kills is the pressure wave, and more importantly, the subsequent rarefaction [vacuum], which ruptures the lungs…. If the fuel deflagrates but does not detonate, victims will be severely burned and will probably also inhale the burning fuel. Since the most common FAE fuels, ethylene oxide and propylene oxide, are highly toxic, undetonated FAE should prove as lethal to personnel caught within the cloud as most chemical agents."
Furthermore, a DIA article reveals, "that because the “shock and pressure waves cause minimal damage to brain tissue…it is possible that victims of FAEs are not rendered unconscious by the blast, but instead suffer for several seconds or minutes while they suffocate.”
Sources:
Backgrounder on Russian Fuel Air Explosives ("Vacuum Bombs") | Human Rights Watch
Thermobaric weapons - killer extordinaire
Thermobaric Weapons | Child Victims of War
Thermobaric Explosive
It is also going to depend on what kind of structure you are referring to and what the atmospheric conditions are. 2 psi to 5 psi is sufficient to destroy most buildings not made of poured and reinforced concrete. A large Thermobaric device can resemble a small nuclear detonation in its effects, minus radiation. With an overpressure within the detonation reaching up to 430 psi and temperatures of 4,500 to 5,400 °F, it will have no problems destroying these types of structures. The vacuum that comes after the detonation is nearly as deadly as the initial blast wave. Because the pressure wave is of a longer duration, Thermobarics are typically more destructive then are high explosives.
Much smaller devices are now being fielded. Russia has several small scale weapons of this type, some as small as 8oz and with a kill radius of 9.8 feet. The RPO-M Rocket launcher has a thermobaric warhead with similar destructive capabilities as a 152 mm High explosive fragmentation artillery shell.
The main advantages of thermobarics is that they do not need to carry their own oxidizer, like conventional explosives. This gives you a larger explosive force in a smaller package. They must be able to use atmospheric oxygen to detonate though and because of this they cannot be used underwater, in space, or even in some adverse weather or at high altitude, but because they use the surrounding oxygen, they can be useful in clearing tunnels and bunkers whereas the blast effects cannot reach deep enough, the lack of oxygen and resulting pressure front and vacuum serve to kill the occupants and destroy equipment deep inside the structure while not destroying the structure itself.
The use of these weapons in a urban setting are cause for some concern. Due to the multiple threat nature of the weapon, it is particularly difficult for civilians to take shelter from them. A human rights watch report from 2001 states:
"The [blast] kill mechanism against living targets is unique–and unpleasant…. What kills is the pressure wave, and more importantly, the subsequent rarefaction [vacuum], which ruptures the lungs…. If the fuel deflagrates but does not detonate, victims will be severely burned and will probably also inhale the burning fuel. Since the most common FAE fuels, ethylene oxide and propylene oxide, are highly toxic, undetonated FAE should prove as lethal to personnel caught within the cloud as most chemical agents."
Furthermore, a DIA article reveals, "that because the “shock and pressure waves cause minimal damage to brain tissue…it is possible that victims of FAEs are not rendered unconscious by the blast, but instead suffer for several seconds or minutes while they suffocate.”
Sources:
Backgrounder on Russian Fuel Air Explosives ("Vacuum Bombs") | Human Rights Watch
Thermobaric weapons - killer extordinaire
Thermobaric Weapons | Child Victims of War
Thermobaric Explosive
- Thread Starter Thread Starter
- #3
Yes, if you look at this http://www.ramcjournal.com/2001/wounds_of_conflict/dearden.pdf at page 3, beyond very short range FAE is clearly more destructive than HE. I think that the "strange" overpressure curve depends on that FAE is dispersed in a large volume before exploding, while HE can be almost considered an exploding point. But HE could be superior in destroying small and strong structures (steel bridge or railroad, for example). Also, what do you know about problems with adverse weather and altitude? Because I wouldn't want a bomb that doesn't explode in heavy rain or in mountain warfare... 
There was a report in Janes in the late 1990's that the British army was going to get a shoulder launched FAE weapon, not sure what came out of it. For some reason, despite their usefulness, especially in FIBUA, the use of FAEs, whether shoulder or vehicled launched, hasn't widely caught on outside of Russia. I have been told that the Indian army trialed Schmel to be used in the northern regions but it was found that FAE warheads were not effective at high altitudes due to the air density.