Explosives: Lethality of 1 pount of TNT

[Anthony]

Originally Posted by Luther

Of course we are talking about explosions, Rupert. That's the whole point of the thread. Since you ask for details, I'm actually talking about static overpressure, that is overpressure after the blast wave (which is called dynamic).

I believe you're misusing the terms, though I'm uncertain because I might just be misreading you. The overpressure that occurs after the initial blast wave is dynamic overpressure. The overpressure caused by the blast wave is static.

Static overpressure results from compressing the atmosphere, and shatters things but doesn't really move them about. Dynamic results from moving the atmosphere, and tends to throw things around but isn't too effective at destroying them. Typically, a blast wave on the building first breaks the building's structure, then the dynamic overpressure knocks the building down.

On a human, the static overpressure might kill (at 50-100 psi, due to lung damage typically), the dynamic overpressure will not kill directly but can cause casualties by throwing objects or people around (shrapnel or translation injuries). Static overpressure is pretty much constant in duration, as it's a single wave, though it can be amplified by bouncing off of things; dynamic overpressure varies with the size of the explosion, and might last longer indoors due to being channeled about.

My main objection to the chunky salsa effect, in any case, is the fact that humans are generally more resistant to overpressure than buildings, so unless you're in a hardened building, or the blast waves are too weak to hurt you anyway, blast waves don't reflect back on you, they just blow out the walls.

[Luther]

Just to make sure we are on the same page: dynamic overpressure is what kicks things around (blast wave), static overpressure is what crushes sealed cans.

Originally Posted by Kromm

"Static overpressure" is almost meaningless when speaking of the effects of explosives on human beings.

OK, thanks. I'll do some more research on the subject.

EDIT:

Originally Posted by Anthony

On a human, the static overpressure might kill (at 50-100 psi, due to lung damage typically), the dynamic overpressure will not kill directly but can cause casualties by throwing objects or people around (shrapnel or translation injuries).

actually, after having read Anthony's post I must agree with him. Yes, I think I use the terms correctly. I must point that my sources agree with what Anthony wrote, and seems to contradict Kromm . . . confused 8-|

[schnuersi]

Originally Posted by Anthony

I would classify a stone building as armored.

Very interesing approach. That would mean virtually any building in germany would qualify as armored. Like the house of my parents or any appanrtement building i lived in until now.

Originally Posted by Anthony

In any case, the 50 psi or so required to actually kill a human from overpressure will definately flatten anything not built like a bunker.

Sice psi is non metric i did a bit of calculation.
50psi are about 3,5 bar or 3,5 times the presure of the atmosphere at ground level. A diver will be exposed to this kind of presure if he dives about 25m (83ft) deep. Even long time exposure will not kill anyone.
So it is not the overpressure itself but the speed at wich the pressure change occures - the speed at wich the front of the shockwave moves.
The dynamic presure is a result of the kinetic energy of a body with a significant mass, wich is moveing. So i guess the shockwave (wich has a physically significant mass and is fast moveing) creates a sudden change of dynamic presure.
Overpressure will not damage a building. Buildings can withstand the force of wind or the weight of water or snow.
Furthermore pressure is force applied by area. If you have 50 psi in the hex of the explosion - wich means if the hex was a 3D-body 50psi would effect every square inch of its surface - that doesn't mean you have 50psi in the six surounding hexes. The surface area the 5m*5m*2,5m room i sugested is much bigger that the surface area of the hex the TNT is placed in.
This is why explosive charges have to be embedded ( i don't know the english word: "verdämmt"). If you put down simple charges you will need a lot more explosives to simply damage a building. I have tables for sizeing breaching charges. But i can't find them right now. But i remember that about 1pound (500g) of TNT will only breach a load bearing brick wall (double layer standart bricks) if it will be properly embedded. Either by takeing some bricks out and place the charge into the wall or by useing sandbags. Furthermore even shaped charges of LAWs (Panzerfaust) or 120mm tank guns are not sufficient to make a building collapes with one hit. While it is possible that a part of the building will colapse and break away that is rather unlikely. There will be quite impressive holes in the walls though.

[Rupert]

Originally Posted by schnuersi

Overpressure will not damage a building. Buildings can withstand the force of wind or the weight of water or snow.

But these are the sort of slow pressures that diving produces, not sudden overpressures like an explosion.

When discussing the damage a nuke does, and to how big an area the common blast radii in discussion are the 5 psi limit and the 2 psi limit. Inside the latter most wooden buildings will be severely damaged, and inside the former none will be standing and stone and concrete buildings will be considerably damaged. However, people won't be directly damaged such blast overpressures (but the fragments of buildings, etc will be very dangerous). Living beings are fairly resilient, buildings are not.

[Anthony]

Originally Posted by schnuersi

50psi are about 3,5 bar or 3,5 times the presure of the atmosphere at ground level. A diver will be exposed to this kind of presure if he dives about 25m (83ft) deep. Even long time exposure will not kill anyone.

Correct, it's the abrupt change in pressure that is lethal.

Overpressure will not damage a building. Buildings can withstand the force of wind or the weight of water or snow.

50 psi is equivalent to piling about 350 meters of snow (assuming average density for new snow) on a building, or a gust of wind moving at 500-1000 m/s. You sure ordinary buildings can withstand that?

Furthermore pressure is force applied by area. If you have 50 psi in the hex of the explosion - wich means if the hex was a 3D-body 50psi would effect every square inch of its surface - that doesn't mean you have 50psi in the six surounding hexes.

Where did I specify that it was 50 psi in the hex of the explosion?

[schnuersi]

Originally Posted by Anthony

50 psi is equivalent to piling about 350 meters of snow (assuming average density for new snow)...

But that would mean snow has less than one tenth the density of water. I know that snow is less dense than water (it floats) but really just one tenth of the density?

Originally Posted by Anthony

...on a building, or a gust of wind moving at 500-1000 m/s. You sure ordinary buildings can withstand that?

Ok, you are right a building can't withstand 50psi of presure.
But i still doubt that one pound of TNT can fill a room of 62,5 m^3 with enough gas to crate 50 psi over a significant part of the surface of the outer walls. I furthermore doubt that it can even create enough gas to blow a room appart if it is solid build out of stone (brick walls).

Originally Posted by Anthony

Where did I specify that it was 50 psi in the hex of the explosion?

"Realistically, 1 lb of TNT has a good chance of killing by overpressure at about one hex..."
"...In any case, the 50 psi or so required to actually kill a human from overpressure will definately flatten anything not built like a bunker"

Two different posts and it doesn't exactly say that.
But i just wanted to point out that the area to wich the force is applied is very important.

[Anthony]

Originally Posted by schnuersi

But that would mean snow has less than one tenth the density of water. I know that snow is less dense than water (it floats) but really just one tenth of the density?

New snow is. That much snow would actually probably compress most of it into ice, so actual thickness would be a glacier about 50m high.

But i still doubt that one pound of TNT can fill a room of 62,5 m^3 with enough gas to crate 50 psi over a significant part of the surface of the outer walls.

Don't believe I said it would. Just said that if you hit a building with the pressure required to kill a human at the same distance, the building is toast.

I furthermore doubt that it can even create enough gas to blow a room appart if it is solid build out of stone (brick walls).

Probably not, though it will take out all the windows. However, if the pressure at the walls is actually 50 psi, the building is going to blow apart.

"Realistically, 1 lb of TNT has a good chance of killing by overpressure at about one hex..."

That means 'one hex away', not 'in the same hex'.

[Luther]

50 psi?

Boys, we just need 20-30 Psi in order to destroy the vast majority of non armored buildings!

For 1 lbs of TNT this is the overpressure experimented at 1.5-2 yards from the explosion. I guess if you put 1 lbs of TNT in the middle of a 4x4yards room, that room is going to be severely damaged, if not destroyed.