Game Mechanics. Thermobaric rounds.

[ArmySGT.]

Have any of you found or brewed your own game mechanics for depicting these weapons?

[mmartin798]

Construction and fuel mix will cause a lot of variation. Off hand I would say take the explosive weight, assume C4 and multiply the DPW by 3 to get the resultant blast plus a fireball of 1200C that covers the blast radius for 1-2 sec would be a good place to start if you needed something fast. I don't think the shockwave + vacuum effect really needs to be exploited. The larger DPW per unit mass is just simpler and gets the job done.

I may have to look more thoroughly into this later.

[ArmySGT.]

Originally Posted by mmartin798

Construction and fuel mix will cause a lot of variation. Off hand I would say take the explosive weight, assume C4 and multiply the DPW by 3 to get the resultant blast plus a fireball of 1200C that covers the blast radius for 1-2 sec would be a good place to start if you needed something fast. I don't think the shockwave + vacuum effect really needs to be exploited. The larger DPW per unit mass is just simpler and gets the job done.

I may have to look more thoroughly into this later.

See that is part of it....... Everything takes burn damage, if only a flash burn...... but, it is the nasty out then in shearing forces of the vacuum effect.

I was thinking of one set of damage for the explosion..... then more damage, possibly half that of the original DPW, as the atmosphere rushes back in.

[mmartin798]

Originally Posted by ArmySGT.

See that is part of it....... Everything takes burn damage, if only a flash burn...... but, it is the nasty out then in shearing forces of the vacuum effect.

I was thinking of one set of damage for the explosion..... then more damage, possibly half that of the original DPW, as the atmosphere rushes back in.

So are you proposing a table similar to the RE chart for round composition for the two effects, i.e. ethylene oxide causes X1 then Y1 dpw, ethylene oxide plus aluminum powder does X2 then Y2 dpw, etc.?

This then questions is there a difference in effect for the two blast effects? They happen very quickly one after the other which is why I suggested a single larger value with an implied greater RE for the explosive to simplify the use. If there is difference, how does that manifest in the application of the damage? Something like you are inside an armored vehicle with weapon ports open that spares you from the initial blast, but the sudden pressure changes rupture ear drums and may cause other whole body damage?

[mmartin798]

Found this article that gives some general figures for FAE used by Russian forces in 2000. Need to think more about how this could work in game.

http://fmso.leavenworth.army.mil/doc...ir/fuelair.htm

Plus Global Security gives some general formulas for calculating distance to 1 PSI over pressure in this article. Using these might get us on the right track.

http://www.globalsecurity.org/milita...itions/fae.htm

[Matt W]

From wikipedia (Quoting the Defense Intelligence Agewncy)

"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."



I don't know if this helps, but the "Modern Firearms" website has this this description of the real-world 93mm thermobaric RPG-7 or RPO-A warhead

"The blast effect of the thermobaric / FAE RPO-A warhead,which contains about 2.2 kg of Fuel-Air Explosive is roughly equivalent to the blast effect of the 107mm / 4" HE artillery shell. Upon explosion, RPO-A warhead generates the cloud of high-temperature flame (blast) which is about 6-7 meters in diameter(blast radius 3 meters or more). The blast cloud lasts as long as 0.4 seconds, thus allowing for significant incendiary effect in addition to the massive pressure wave (typical HE explosion lasts much shorter)."

What rules do you need?