Explosions

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Explosions

Certain attacks, such as hand grenades and Explosive Fireball spells, produce a blast when they hit. Such attacks have the notation “ex” after their damage type: “cr ex” for a crush- ing explosion, “burn ex” for a burning explosion, and so on.

In addition to doing the listed dam- age to whoever was struck directly, an explosion inflicts “collateral damage” on everything within (2 × dice of dam- age) yards. For instance, if an explo- sion does 6d×2 damage, everyone within 24 yards is vulnerable – although some might be lucky enough to take little or no damage.

The listed damage only applies “as is” to the target struck. For everything else caught in the blast, roll this dam- age but divide it by (3 × distance in yards from the center of the blast), rounding down. Roll damage individ- ually (but the GM can save time by using one roll for several NPCs). Use torso armor to determine DR against explosion damage.

If an explosive attack has an armor divisor, it does not apply to the collat- eral damage. For example, the shaped- charge warhead of an anti-tank rocket has an armor divisor of (10), but this only reduces the DR of a target it actu- ally strikes; those nearby get their full DR against the blast.

Explosions are considered incendi- ary attacks, and can start fires; see Catching Fire (p. 434).

Anyone caught in a blast may attempt an active defense roll to dive for cover from the explosion’s collater- al damage and fragmentation; see Dodge and Drop (p. 377).

Explosions in Other Environments

Other Atmospheres: These rules assume Earth-normal air pressure. A thicker or thinner atmosphere enhances or reduces the blast effect. Underwater, divide collateral damage by range in yards instead of 3 × range in yards. In a vacuum or trace atmosphere, with no medium to carry the shockwave, damage comes only from the expanding gases themselves: divide damage by 10 × range in yards.

Contact Explosions: A person can throw himself on a grenade, etc. to protect his friends; see Sacrificial Dodge and Drop, p. 377. He takes max- imum possible damage; his DR protects him normally. Everyone else gets his torso’s DR + HP as “cover DR.”

Internal Explosions: If an explosive goes off inside someone – e.g., a follow-up attack penetrates the target’s DR, or a dragon swallows a hand grenade – DR has no effect! In addition, treat the blast as an attack on the vitals, with a ×3 wounding modifier.

Fragmentation Damage

Many grenades, bombs, and artillery shells have metal casings designed to shatter when they explode, producing a storm of sharp fragments. Some are packed with extra material (pellets, nails, etc.) to enhance this effect.

Fragmentation damage, if any, appears in brackets after explosive damage; e.g., “[2d]” means 2d frag- mentation damage. Everyone within (5 × dice of fragmentation damage) yards is vulnerable. For example, that [2d] attack would throw fragments out to 5 × 2 = 10 yards.

The farther a target is from the blast, the less likely the fragments are to hit him. A hit is automatic if the explosive attack actually strikes the target. The fragments attack everyone else in the area at skill 15. Only three modifiers apply: the range modifier for the distance from the center of the blast to the target, the modifier for the target’s posture (prone, etc.), and the target’s Size Modifier. It is possible for several fragments to hit! For every three points by which the attack roll succeeds, one additional fragment strikes the target.

The only active defense against fragments is to dive away from the explosion that produced them; see Dodge and Drop (p. 377).

For each hit, roll hit location ran- domly. If that location is behind cover, the fragment hits cover.

Fragmentation damage is cutting. Note that if an explosive attack has an armor divisor, this does not apply to the fragments it produces.

Airbursts: Against an airburst, do not apply posture modifiers – lying prone under an airburst does not decrease the body area exposed to the rain of fragments! Only overhead cover protects.

Incidental Fragmentation: An explosion with no listed fragmenta- tion damage can still create fragments if there is any loose or frangible mate- rial at the explosion site. Incidental fragmentation damage ranges from 1d-4 for ordinary earth to 1d for an explosion on loose scrap.

Hot Fragments: White phosphorus- type smoke warheads produce this effect. The fragments typically inflict 1d(0.2) burning damage every 10 sec- onds for one minute.

Demolition

Sometimes the only way to deal with a problem is to blow it up! If the adventurers are using or facing explosives, the PCs or GM should decide how many dice of damage – in multiples of 6d – the blasting charge is supposed to do, and what kind of explosive it is.

Explosives normally do crushing damage with the Explosion modifier (p. 104) – and often the Fragmentation modifier (p. 104).

How Much Explosive? An explo- sion doing 6d×n damage takes (n×n)/4 pounds of TNT. If you are using an explosive other than TNT, divide the weight required by its relative explosive force (REF) – see the Relative Explosive Force Table, below. How Big a Blast? Reverse the for- mula to determine how much damage a given weight of explosive will do: damage is 6d × square root of (weight of explosive in lbs. × 4 × REF).

Example: A 1920s Chicago safe- cracker plans to blast through a bank vault. Estimating the toughness of the vault (see p. 557), he decides he needs a blast that does 6d×8 damage. He’s using dynamite. The weight of dynamite he needs is (8 × 8)/(4 × 0.8) = 20 lbs.

Relative Explosive Force Table

TL	Type	REF	Description
3	Serpentine Powder	0.3	Standard gunpowder, pre-1600.
4	Ammonium Nitrate	0.4	Common improvised explosive.
4	Black Powder	0.4	Standard gunpowder, 1600-1850.
5	Black Powder	0.5	Standard gunpowder, 1850-1890.
6	Diesel Fuel/ Nitrate Fertilizer	0.5	Common improvised explosive.
6	Dynamite	0.8	Commercially available for mining, demolition.
6	TNT	1.0	The basic, stable, high explosive.
6	Amatol	1.2	TNT-ammonium nitrate. Fills bombs & shells in WWII.
6	Nitroglycerine	1.5	Unstable! If dropped, detonates on 13+ on 3d.
7	Tetryl	1.3	Common for smaller explosive shells and bullets.
7	Composition B	1.4	Another common explosive filler.
7	C4 Plastic Explosive	1.4	Standard military and covert-ops explosive.
9	Octanitrocubane	4	Theoretical advanced explosive.
10	Stabilized Metallic Hydrogen	6	Exotic science-fiction explosive.