Burning and Bombing

[NCLanceman]

Maybe I missed it somewhere, but is there a REF for Gasoline? As in, if a character threw a full jerry can of gasoline at a terrorist and somehow ignited it, how big would the explosion be? For that matter, what about propane, kerosene, diesel, aviation fuel, and so on?

Also, is there a basic identity for a single point of burning damage, kind of like how there's a basic identity for regular damage? I was looking at the Making Things Burn sidebar on B433 and was wondering if I could make a slightly more detailed flashpoint table.

[vicky_molokh]

IIRC liquid gasoline doesn't explode, gaseous gasoline does.

[Kuroshima]

Originally Posted by vicky_molokh

IIRC liquid gasoline doesn't explode, gaseous gasoline does.

I'm pretty sure it does, under the right temperature and pressure conditions ;) (hint: very few things don't explode under the right temperature and pressure conditions, now these conditions might not be very feasible)

[Michele]

Originally Posted by Kuroshima

I'm pretty sure it does, under the right temperature and pressure conditions ;) (hint: very few things don't explode under the right temperature and pressure conditions, now these conditions might not be very feasible)

At pretty average temperatures and pressures, you don't need gaseous gasoline for explosions; but you need it to be aerosolized, fairly well dispersed in the air in the form of minuscule droplets (having it liquid and all contained in a jerrycan won't work).
At that point you have FAE potential, which you can ignite by raising the temperature and pressure with any conventional means and to unexceptional values.
After all, this mechanism happened to take place (accidentally) with particles of flour or grains suspended in the air, and also (accidentally or intentionally, say as in German experimental FAE ammunition at the end of WWII) with particles of coal dust.

The good old Molotov cocktail works as burning damage.

[Bruno]

"Gasoline" as in what you put in your car, in the state ready to BE put in your car, is not an explosive. It just doesn't explode.

Kuroshima's comment about pressure and temperature is a bit deceptive, because it's true that a pressure vessel "explosion" makes a huge bang, releases a lot of energy, and throws shrapnel (and probably toxic, caustic or hot liquid/gas) everywhere, it's not a sudden conversion of chemical energy to kinetic energy. It's not an explosion. It's just something bursting REALLY HARD.

It's like the difference between something really really hot, and something on fire. One is something really really hot, the other is a chemical reaction that makes heat. Both can burn you, but there's an important difference between the two.

Gasoline (as a polite, well behaved liquid) just isn't explosive. That's why they let any idiot buy gasoline after all.

As a fuel-air mixture it's fussy (takes a precise mix, so usually wants a fairly enclosed space to prevent "contamination" with more air), and can't be stored "ready to use". A little googling says for gasoline vapor, the explosive range is from 1.3 to 6.0% vapor to air ratio. Which means its actually very easy to end up with too much gasoline in the mix, and it's not explosive any more.

I can't find a strict REF value, but:
"TNT generates well over 4,000 psi overpressure in close proximity to the source of the explosion" while "Peak pressures created within the detonated fuel-air cloud reach 300 pounds per square inch (psi)" so that seems to indicate about a REF of 0.05 to 0.075 - unless I'm totally misunderstanding this.

The first problem with this guesstimate is that this is not very clearly linked to a given quantity of material.

But don't forget that
1) FAE effects are area effects - they don't emanate from a point, they emanate from a large radius, and everything inside the radius is at ground zero (and thus takes maximum damage)

2) in GURPS has FAE damage divided by distance from the explosion, NOT distance/3 like with traditional explosions.

[Figleaf23]

Originally Posted by Bruno

... It's not an explosion. It's just something bursting REALLY HARD.

Perhaps bursting really hard is adequate for the purpose though.

[malloyd]

Originally Posted by NCLanceman

Maybe I missed it somewhere, but is there a REF for Gasoline? As in, if a character threw a full jerry can of gasoline at a terrorist and somehow ignited it, how big would the explosion be? For that matter, what about propane, kerosene, diesel, aviation fuel, and so on?

As everybody else has said, none of those would explode in reality - the ease with which gas tanks blow up in film is a cinematic convention.

If you do manage to disperse one of them as fine droplets in enough air to produce a fuel-air explosive, which is actually pretty hard to do correctly, REF values go pretty much as total energy release. With TNT at 4.2 MJ/kg, all hydrocarbon fuels are about REF 10 (some anti-knock, alcohol or biofuel mixes may go down to 9, propane is ideally 11.03, but close enough). Incidentally these are much higher than explosives because you are cheating. If you included the weight of the *oxygen*, which is generally several times heavier than the fuel used, these would drop to something closer to 3, but you usually don't have to carry the air.

[Bruno]

Originally Posted by Figleaf23

Perhaps bursting really hard is adequate for the purpose though.

Under that criteria, air and water are both explosive. :P

[malloyd]

Originally Posted by Bruno

Under that criteria, air and water are both explosive. :P

I tell you people just are so reckless with a dangerous chemical like distilled water. Look at it, it explodes under pressure, burns vigorously in a fluorine atmosphere, reacts violently if you put it in (alkali) metal containers, is lethally toxic to saltwater fish, and of course has been found in 100% of all cancer cells....

[vicky_molokh]

Originally Posted by malloyd

I tell you people just are so reckless with a dangerous chemical like distilled water. Look at it, it explodes under pressure, burns vigorously in a fluorine atmosphere, reacts violently if you put it in (alkali) metal containers, is lethally toxic to saltwater fish, and of course has been found in 100% of all cancer cells....

You really should call it by the scientific name.