Dust Explosion - Grain, flour, wheat

[Donny Brook]

Originally Posted by Icelander

There's a lot of arrows, crossbow bolts, darts, javelins and scorpion bolts.

What about using pebbles and fly higher?

[Icelander]

Originally Posted by Donny Brook

What about using pebbles and fly higher?

I doubt that the terminal velocity of a pebble is significantly higher than that for a heavy crossbow bolt falling point first and the crossbow bolt is both heavier and sharper. When I think 'pebble', I imagine something no heavier than an ounce, maybe lighter. So pebbles would be a lot less effective as weapons than bolts.

You could, of course, probably carry much more of them, as there is no need to drop them in a specific way that ensures that they fall point-first. But how much damage would a pebble at Move 70 (or even Move 100+) do against a hoplite in a DR 6+ helmet and with both shoulder and upper torso armour of DR 5+?

I don't really know how high you'd need to go to get terminal velocity from a pebble or a bolt. I imagine that at a 1,000 yards, you are likely close enough to it so that going higher is probably not worth it, but I haven't actually modelled the physical dimensions of the objects and calculated air resistance.

Rocks of four ounces or so are more promising as weapons, of course. But as long as you have heavy crossbow bolts weighing four ounces, why not use those instead? If they hit point-on, they should penetrate armour much better than a round stone of the same weight and the after-armour effects are most likely more dramatic.

The drawback to dropping pebbles, rocks, bolts, arrows or javelins, however, is that from a height of 1,000 yards, the odds are that most of the weapons do not hit anything. With Dropping skill 8-12, I think it's easy for the flying mages to miss columns of enemy troops entirely. And even if they hit, most of the weapons will hit the spaces between men.

Sure, there will be casualties. Have been, as the PC did make a sortie dropping bolts on the vanguard of the enemy army as they approached the city walls. But he was dissatisfied by the effects and wanted to explore if anything in the city would have more impact for the same payload weight.

[Icelander]

Originally Posted by Nereidalbel

Two tons of flower? What else can your mages and/or army grind into dust? If you can grind things fine enough, almost anything is explosive, even aluminum and wood. Do note that sawdust should be readily available, and probably a bit cheaper than flour.

The cost of a couple of tons of flour or grain dust is irrelevant at this point. They've captured so many thousands of ton of grain that they can't usefully account for it all before they have to fight off the army trying to take their recently acquired city.

With good enough Administration rolls, the PC could manage to get maybe several dozen sailors acting as foremen for an unknown number of recent POWs and/or local slaves to work for them during the 12 hours they have. But grinding sawdust to save the cost of a couple of tons of grain dust is insanely low on the priority scale. Far better to have all available workers move artillery from the coastal forts to the land walls, collapse houses near likely breach points, erect obstacles around the gates, etc.

Originally Posted by Nereidalbel

Here's some data on various explosive dusts.

Awesome! So, judging by these stats, under perfect conditions, distributed evenly, around one and a half tons of grain dust in a cloud 20' high and 50 yards in radius is just about enough concentration to explode.

That means that two tons under combat conditions is not going to be enough for such a big cloud. On the other hand, a unit of thousand men might only occupy 20 yards by 50 yards when massing for an assault through a breach and an explosion of half the volume above would tear the heart out of one (and probably everyone nearby)

Originally Posted by Nereidalbel

And here's 4 kilograms of flour exploding.

Pretty cool.

[Nereidalbel]

Originally Posted by Icelander

Awesome! So, judging by these stats, under perfect conditions, distributed evenly, around one and a half tons of grain dust in a cloud 20' high and 50 yards in radius is just about enough concentration to explode.

While the initial fireball doesn't meet the goal, the shockwave will throw powder from the ground into the air, which ignites, throws more powder into the air, ignites again...basically, you have a cluster bomb.

[Refplace]

Its possible but harder to do in the way described then many realize.
The key is concentration percentage.
https://en.wikipedia.org/wiki/Lower_flammable_limit
However I couldn't find the flashpoint fo flour and grains, probably varies by type but maybe not enough to matter.
IIRC from a very long time ago the ration had to be between 25 and 35% but I don't recall or have access to those sources anymore.

Why not use catapults for delivery by the way?

Edit according to the link above grain dust has a LFL of 125
A Dijinn spreading it around could help but even if no explosion if its concentrated enough to all burn it will look spectacular and scary.

[Nereidalbel]

Originally Posted by Refplace

Why not use catapults for delivery by the way?

Flying mages can follow up with fireball wands to ignite things right after they hit the ground.

[Refplace]

Originally Posted by Nereidalbel

Flying mages can follow up with fireball wands to ignite things right after they hit the ground.

Right but the can fire at catapult targets as well and wont be as tired trying to haul sacks of grain around. Or as much of a target.

[Icelander]

Originally Posted by Refplace

Why not use catapults for delivery by the way?

Originally Posted by Nereidalbel

Flying mages can follow up with fireball wands to ignite things right after they hit the ground.

Originally Posted by Refplace

Right but the can fire at catapult targets as well and wont be as tired trying to haul sacks of grain around. Or as much of a target.

The larger catapults are located near the sea walls. They can shoot outside the land walls, but only around 100-200 yards away from them. Smaller ballistae can reach 300-350 yards from the walls.

The PCs would be more comfortable if the explosion took place maybe 500 yards away from the walls, unless there is just no good concentration of enemy troops that far out.*

Also, I think falling from a 1,000 yards** in a bag spreads flour or grain dust around better than being shot from a ballista a mere 300 yards.

*In which case the PCs may throw caution to the winds and elect to aim for a point closer to the walls anyway, in typical PC fashion. Hoping that they calculate the blast radius close enough to correctly so that they don't scour the walls clean of their own men.
**Or higher, if desired, given that the higher they go, the safer the mages are.

[Dalillama]

Originally Posted by Icelander

The larger catapults are located near the sea walls. They can shoot outside the land walls, but only around 100-200 yards away from them. Smaller ballistae can reach 300-350 yards from the walls.

The PCs would be more comfortable if the explosion took place maybe 500 yards away from the walls, unless there is just no good concentration of enemy troops that far out.*

Also, I think falling from a 1,000 yards** in a bag spreads flour or grain dust around better than being shot from a ballista a mere 300 yards.

Why not both? You've got plenty of flour, after all, and the more you can send over, the better your chances of getting a boom.