DnD and Massive Explosions

[Yanisa]

Note: This happened during a pathfinder game, but general advice is always appreciated.

My party walked into classic trap. They went into a large room, where normally the doors would close, and then they realize the walls are full of arrow slits, leading to a nasty ambush. But they were lucky and spotted the mechanic of the door and sabotaging it. They still got their pelted with bolts and were not able to attack properly. Then the alchemist says: "Hey guys, my car is outside and loaded with explosive. Let's grab a couple of those and blow up the wall." Then the barbarian decided he will grab them, being the fastest of the group, but he decides to grab ALL the explosive, about 3 crates with 10 each, and set them all off.

According the numbers, and rules as written, the wall as 180 hitpoints (12 inch thick) and 8 hardness. The explosives are Fuse grenades (http://www.d20pfsrd.com/equipment---final/weapons/alchemical-weapons#TOC-Fuse-Grenade) dealing 2d6 bludgeoning damage and 1d6 fire. The 2d6 is against 8 hardness, and the 1d6 fire doesn't have face hardness, but only does half damage (if I remember the rules correctly)
I used an online generator to roll (average would mean 1 damage per grenade*) and got a total of 85 damage, meaning the wall would be at roughly at half hit points for the 2 squares that were hit.

*2d6 average = 7, doesn't beat 8 hardness, 1d6 average = 3.5, half damage is 1.75, rounded down to 1...

But I feel, and I might be wrong at this having no experience with explosives, that so many explosive together would deal a lot more damage. Also I find it sad for the poor alchemist to see all his supplies wasted...

So my questions to the playground are:
Do you know of any rules about massive explosives within dnd (or even real life, just as a reference)
And how would you handle this insanity of explosives?

[CaladanMoonblad]

You could have required a "Knowledge (Architecture and Engineering)" DC of say, 15 or 20 to find the weakest spot to escape the room. Maybe give a +2 synergy for 5 or more ranks in Perception.

Except here's the thing... they all go off at once? I would have treated it as the same explosion. So... 2d6xtotal number of grenades then -8 hardness.

That might give you a more cinematic scene.

When someone uses C-4 to demolition a bank vault, they use a certain amount of the stuff to create a single explosion. They don't add up all the ounces for several tiny explosions : /

[xkaliburr]

You could have required a "Knowledge (Architecture and Engineering)" DC of say, 15 or 20 to find the weakest spot to escape the room. Maybe give a +2 synergy for 5 or more ranks in Perception.

Except here's the thing... they all go off at once? I would have treated it as the same explosion. So... 2d6xtotal number of grenades then -8 hardness.

That might give you a more cinematic scene.

When someone uses C-4 to demolition a bank vault, they use a certain amount of the stuff to create a single explosion. They don't add up all the ounces for several tiny explosions : /

I would agree with that assesment, if there were 30 grenades, this does 60d6 against a hardness of 8.

[lsfreak]

Except here's the thing... they all go off at once? I would have treated it as the same explosion. So... 2d6xtotal number of grenades then -8 hardness.
This would be a good short-and-fast solution, provided the PC's don't manage to abused it somehow.

Long Version:
Realistically, the power of an explosive depends on how long it can be contained - basically, the most it's contained (including packed together, with gunpowder), the more of the material can explode before the explosion pushes it too far apart to react, and the sharper the shockwave (think of a gun - a small amount of charge that produces a nice fast flame if you light it in the open, but completely contained...).

So, depending on the amount of realism* you want, I'd say the best option would be to crack open the grenades, extract the gunpowder, and pack it into one of the traps. That's going to give you a much more focused, relevant blast - it's actually inside the walls, and thus focuses the shockwave against the walls. Then I'd have each grenade's worth of gunpowder do a flat 3d6 bludgeoning damage to the wall, ignoring half hardness**. Once you have at least X powder, the damage goes to 4d6, representing a tighter pack and higher burn rate from exploding in an increasingly-constructed space. Since this is the first time it's come up, depending on how flexible your group is, I'd let them retroactively change it, with the alchemist (and maybe others) making Int or Wis checks to come up with this plan.

*Actually, a clay pot won't be enough to turn gunpowder into a really effective grenade, as far as I know. Traditional, gunpowder-based grenades were cast-iron or steel, in order to keep the reaction contained long enough to turn it into a real *explosion* (and the resulting shrapnel when the explosion finally overcame the shell). So we're likely dealing with something much more powerful than gunpowder if it doesn't even need contained to explode well (or it's bad writing and they mixed up the clay pots used for early napalm-like materials, which only burn, with the iron ones used with explosives).

**Disclaimer: I don't play Pathfinder and don't know if this makes disassembled frag grenades better than something that already exists.

[EyethatBinds]

The trouble with explosives is their steadfast determination to take the path of least resistance. Setting a grenade next to a stone wall will certainly make a dent, but it's extremely difficult to shape the blast to be specifically directed towards the wall. The burst goes in all directions equally, then encounters resistance from the wall. I might allow each charge to do damage, but they would be applied separately with no particular modifiers.

A laboratory where they routinely test explosives today often has a two or three foot thick reinforced concrete blast shield that ensures those testing said explosives minimal risk. I would say that wall should be standing because clay grenades couldn't do too much to the wall.

Here's a link for more scientific information on the use of explosives against standing structures.
http://www.orau.gov/DHSsummit/presentations/March18/Panel19/Shukla_Mar18.pdf

[Slipperychicken]

What was the wall made of? Judging by the stats you gave, Reinforced Masonry. Fuse grenades aren't exactly bunker-busters, they're primitive handheld incendiaries. These grenades would have logically gotten through wood no problem, but not solid reinforced stone. The game mechanics support this.

If you want bigger explosions, I recommend the Powder Keg (http://www.d20pfsrd.com/equipment---final/weapons/weapon-descriptions/ammunition/black-powder), listed under firearm ammunition because it's technically 100 doses of powder. When it blows, it deals 5d6 fire damage, 20ft burst. With the Gunsmithing (http://www.d20pfsrd.com/feats/general-feats/gunsmithing) feat, you can craft one a day for 100gp each. 30 of those would have cleared the wall almost three times over if my calculations are correct (17.5 average/2 = 8.75 each [no hardness because it's energy damage], times 30 = 262.5).

[Yanisa]

First off, thanks for all the replies.

Just as a general fact, in game the explosion already happened. They didn't allow themselves for any thinking time (and I really tried to make them rethink their actions)

Basically my choice is to threat it either a big explosion (which was my first inclination) or go the more realistic route, which means the wall gets dented, but far from destroyed.
The silly thing is, after rereading some the rules I saw the the grenades have a random detonation timer of 1d3 rounds. Which means the first explosion will launch the rest of the grenades trough the room. Even if the explosion is strong enough the trigger the next batch to explode earlier, they are still launched away from the wall.
So I go with the more realistic route, and maybe make the grenades random scatter (not all of it has to be realistic).

[Doug Lampert]

The silly thing is, after rereading some the rules I saw the the grenades have a random detonation timer of 1d3 rounds. Which means the first explosion will launch the rest of the grenades trough the room. Even if the explosion is strong enough the trigger the next batch to explode earlier, they are still launched away from the wall.
So I go with the more realistic route, and maybe make the grenades random scatter (not all of it has to be realistic).

Simultaneous detonation is HARD, watch Mythbusters.

The first blast (probably) won't trigger the others, because blackpowder is a low explosive (it doesn't contain itself due to its own inertia but needs external force to contain and generate an actual blast as opposed to fast burning fire).

The first grenade blasts when the containment fails with pretty much exactly enough force to break the containment at the point of failure, energy density pretty much everywhere else is lower and thus not enough to cause a containment failure except on a grenade already starting to detonate on its own or badly flawed. And if we do shatter another grenade it doesn't blast because its containment just failed.

However, when the grenades scatter their fuses will be messed with, which may accelerate or delay detonation depending on the fusing used and bunches of more or less random stuff. I wouldn't want to share a room with this going off, but I doubt it would do even as much damage to the wall then what you let it do.

OTOH D&D runs largely on Rule of Cool. The only real problem with letting it work is if it then becomes SOP or is assumed to have set a houserule. If we had some sort of PC plot coupon power I'd have no trouble with letting this work with enough of that.

[Xervous]

Simultaneous detonation is HARD, watch Mythbusters.

Technically, in DnD, no two actions can happen at the exact same time, so simultaneous detonation of separate explosives is impossible.

[XionUnborn01]

I agree that it's probably easiest to treat it as one big source of damage, the players will appreciate that a lit more.

I just wanted to point out that in this case, it's probably not a good idea to use average damage, because some will be higher and some lower. Not sure how to remedy that, but i wanted to let you know.

[lsfreak]

The silly thing is, after rereading some the rules I saw the the grenades have a random detonation timer of 1d3 rounds. Which means the first explosion will launch the rest of the grenades trough the room. Even if the explosion is strong enough the trigger the next batch to explode earlier, they are still launched away from the wall.

Maybe. Once again, if it only takes a clay pot to get lethal results (3d6 damage versus a commoner's 1d4 hit points), we're probably dealing with something closer to TNT than black powder, and at that point, sympathetic detonations are a lot more likely to happen. But even so, the pot has so little hit points that it will be disintegrated by the first grenade, not launched across the room. The powder will be either ignited "instantly" (as soon as the damage is done), or not at all.

Still, this is why I recommended unpacking the grenades and packing the "powder," whatever it is, into the wall.

[Slipperychicken]

Technically, in DnD, no two actions can happen at the exact same time, so simultaneous detonation of separate explosives is impossible.

IIRC, exploding isn't an action. Otherwise, dazed creatures wouldn't be able to explode.

[Yanisa]

Maybe. Once again, if it only takes a clay pot to get lethal results (3d6 damage versus a commoner's 1d4 hit points), we're probably dealing with something closer to TNT than black powder, and at that point, sympathetic detonations are a lot more likely to happen. But even so, the pot has so little hit points that it will be disintegrated by the first grenade, not launched across the room. The powder will be either ignited "instantly" (as soon as the damage is done), or not at all.

Still, this is why I recommended unpacking the grenades and packing the "powder," whatever it is, into the wall.

All this talk about grenades did make me forgot they are little more then small clay container with powder and a fuse. The force of one will break another.

So no random scattering as well, that could have been potential deadly and hilarious.


IIRC, exploding isn't an action. Otherwise, dazed creatures wouldn't be able to explode.
I don't think explosions are a term within dnd, other then a means to explain how force, bludgeoning and fire damage happen.
Setting 90 grenades off at the same time is more like doing full round action with 90 attacks.

~~~~~~~~

Regardless, it does seem that both in real life, and in the dnd, this plan will fail, all rules and logic point to no. It most likely be a giant dud, the first explosions will destroy all the other grenades, barely hurting the wall.

I think I will discuss it with my players, showing how much it fails, and perhaps give them the wall destroying this one time, for the rule of cool.

[Slipperychicken]

I think I will discuss it with my players, showing how much it fails, and perhaps give them the wall destroying this one time, for the rule of cool.

I say give them all a Knowlege (Architecture and Engineering) roll to realize it would completely fail. DC 10-15 seems fair.

Might make sense let it work this time, depends on how serious the game is.