Dust Explosion - Grain, flour, wheat

Icelander · 11-04-2015, 10:07 AM

A PC in a fantasy campaign set at TL4*, a PC mage who has access to a lot of fire magic and a fair amount of flying magic wants to explore the possibilities of burning and/or exploding a huge number of people in a besieging army around the walled city he and his men are occupying.

This PC commands some fifty mages, most of whom are very low-powered on a Mass Combat scale. Magery levels are mostly 1 (ca 60% of them), with a minority of Magery 2-3 and maybe eight mages who are Magery 4+. These mages have a way to fly magically, but most of them are not powerful enough to cast such a spell themselves, but instead use one of several Wands that can be used to cast up to 50 such spells before being depleted.

All of the flying wizards also have at least one Wand (from 5-25 charges) that can make a ranged attack, mostly Fireballs** that can cause significant injury within 10' or so and wound out to 30' radius.

Now, the PC wants to increase the destructive power of these flying wizards against a mostly earth-bound foe. Low-flying wizards casting fireballs are cool and all, but not only would they be taking huge risks flying that low over enemy lines, they could also expend all their fireballs without taking out all the enemy. There is a very large army of 30,000 men coming, with the cavalry vanguard and elite light troops already outside the city walls preparing the assault.

With trial and error, our PC has already found out that flying high and dropping stuff on ground-bound foes is very effective. On the other hand, such indiscriminate dropping of sharp and/or heavy things from the air not going to make much of a dent in the numbers of 30,000 enemies marching to take the city the PCs are defending, especially as those 30,000 enemies are going to either take the city or be broken against the walls within the next 24 hours.

The flying wizards don't have the flight magic for more than one or two sorties within that time. Also, lingering above the enemy lines dropping stuff on them eventually leads to them summoning flying creatures to kill the mages. Any height where the mages can actually see valuable targets and hit them with fireballs or dropped stuff is also a height where ground-bound enemy spellcasters can take them out and/or summoned flying creatures can easily catch them.

The city where the PCs are preparing their defence used to be the primary port city of the invading enemy armies. Military supplies for three field armies, more than 70,000 men, were kept in warehouses there, after being shipped in from the country where the enemy comes from. There is also food for the population of the city and for tens of thousands of labourers working for the invading armies. That means a lot of tons of grain (so many thousands), some of which has already been ground and made into flour.

So the flying mages can get as much grain as they want. And more of that grain than they could carry up in the air, even in several sorties, is available as finely ground as they'd like.***

Is dropping a ton or two of flour into the air around enemies they want blown up before fireballing them even a viable strategy?

The way the PC sees it happening is that his mages carry up into the air as much flour, still in bags, as they can carry. Then they drop it all on the foe, hoping that it will hit the ground hard and a lot of it will be spread to the sides and float around in the air. The PC then thought he'd get a summoned djinn to spread the flour around at ground level before hitting the area with as much fire as possible.

How much flour do you need to spread into the atmosphere for a proper dust explosion?

Working with no more than maybe two tons of flour, how large an area could the PC realistically aim for?

What are guidelines for the damage of such a dust exlosion, if I can get one to happen?

*With modifiers, the most significant one being that conventional gunpowder doesn't work for some arcane reason and smokepowder, the alchemical alternative, is a couple of orders of magnitude more expensive.
**6d burn ex/2.
***There were enough nobles and commanders in the city for there to be a lot of demand for top-quality unhealthy white bread and other baked goods.

11-04-2015, 10:07 AM	#1
Icelander Join Date: Mar 2006 Location: Iceland*	Dust Explosion - Grain, flour, wheat A PC in a fantasy campaign set at TL4, a PC mage who has access to a lot of fire magic and a fair amount of flying magic wants to explore the possibilities of burning and/or exploding a huge number of people in a besieging army around the walled city he and his men are occupying. This PC commands some fifty mages, most of whom are very low-powered on a Mass Combat* scale. Magery levels are mostly 1 (ca 60% of them), with a minority of Magery 2-3 and maybe eight mages who are Magery 4+. These mages have a way to fly magically, but most of them are not powerful enough to cast such a spell themselves, but instead use one of several Wands that can be used to cast up to 50 such spells before being depleted. All of the flying wizards also have at least one Wand (from 5-25 charges) that can make a ranged attack, mostly Fireballs** that can cause significant injury within 10' or so and wound out to 30' radius. Now, the PC wants to increase the destructive power of these flying wizards against a mostly earth-bound foe. Low-flying wizards casting fireballs are cool and all, but not only would they be taking huge risks flying that low over enemy lines, they could also expend all their fireballs without taking out all the enemy. There is a very large army of 30,000 men coming, with the cavalry vanguard and elite light troops already outside the city walls preparing the assault. With trial and error, our PC has already found out that flying high and dropping stuff on ground-bound foes is very effective. On the other hand, such indiscriminate dropping of sharp and/or heavy things from the air not going to make much of a dent in the numbers of 30,000 enemies marching to take the city the PCs are defending, especially as those 30,000 enemies are going to either take the city or be broken against the walls within the next 24 hours. The flying wizards don't have the flight magic for more than one or two sorties within that time. Also, lingering above the enemy lines dropping stuff on them eventually leads to them summoning flying creatures to kill the mages. Any height where the mages can actually see valuable targets and hit them with fireballs or dropped stuff is also a height where ground-bound enemy spellcasters can take them out and/or summoned flying creatures can easily catch them. The city where the PCs are preparing their defence used to be the primary port city of the invading enemy armies. Military supplies for three field armies, more than 70,000 men, were kept in warehouses there, after being shipped in from the country where the enemy comes from. There is also food for the population of the city and for tens of thousands of labourers working for the invading armies. That means a lot of tons of grain (so many thousands), some of which has already been ground and made into flour. So the flying mages can get as much grain as they want. And more of that grain than they could carry up in the air, even in several sorties, is available as finely ground as they'd like.*** Is dropping a ton or two of flour into the air around enemies they want blown up before fireballing them even a viable strategy? The way the PC sees it happening is that his mages carry up into the air as much flour, still in bags, as they can carry. Then they drop it all on the foe, hoping that it will hit the ground hard and a lot of it will be spread to the sides and float around in the air. The PC then thought he'd get a summoned djinn to spread the flour around at ground level before hitting the area with as much fire as possible. How much flour do you need to spread into the atmosphere for a proper dust explosion? Working with no more than maybe two tons of flour, how large an area could the PC realistically aim for? What are guidelines for the damage of such a dust exlosion, if I can get one to happen? With modifiers, the most significant one being that conventional gunpowder doesn't work for some arcane reason and smokepowder, the alchemical alternative, is a couple of orders of magnitude more expensive. 6d burn ex/2. **There were enough nobles and commanders in the city for there to be a lot of demand for top-quality unhealthy white bread and other baked goods. __________________ Za uspiekh nashevo beznadiozhnovo diela!