Nuclear Warfare (Overkill Supplement)
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Nuclear weapons are very interesting devices with incredible destructive abilities, capable of wiping out cities and killing tens of thousands of people outright. To put it simply, they're fun! Now with these rules, you can implement them in your very own game of Dungeons & Dragons!
The Quick Rundown on Nuclear Devices
Here's a brief on how nuclear weapons work. It's not intended to be a rigorously comprehensive or technical guide, it's just enough so that you know what you're dealing with and you can use these bombs in your game. If you want more information, read a book. Basically, there are two main types of devices: Fission (Atomic) devices and Fusion (Thermonuclear/Hydrogen) devices. Fission weapons are bombs which work by splitting apart the atoms of fissible material - plutonium or enriched uranium. On detonation, high-powered explosives are used to force two chunks of the fissionable material together, resulting in the splitting of one atom, which leads to a chain reaction of fissioning atoms and a tremendous release of energy. This is called a fission reaction. Fission reactions generate a lot of long-lived radioactive byproducts in the form of nuclear fallout.
Fusion devices, on the other hand, are called that because they use the compression and heat resulting from a fission reaction (described above) to fuse two or more atoms which are not normally fissible together and form a different element with an even larger explosive yield. Fusion weapons are more efficient than fission weapons, generating about four times the yield with the same mass of material.
Quantifying the Damage of Nuclear Devices
Following the initial fission or fusion reaction, the following stuff happens:
- Radiation Burst
The first thing a nuclear explosion does is release tremendous amounts of radiation into the immediate vicinity in the form of neutrons and gamma rays. As far as 1 mile away from a 1-megaton bomb, the radiation alone can cause instant death (treat as deadly radiation). However, radiation disperses quickly in the atmosphere. Assume for convenience that the severity of the radiation decreases by one category for every increment of a range equal to half the area of deadly radiation. Thus, assuming a 1-mile blast of deadly radiation, the area would be irradiated as follows: Very Heavy 1 mile - 1 1/2 miles, Heavy 1 1/2 miles - 2 miles, Medium 2 miles - 2 1/2 miles, Low 2 1/2 miles - 3 miles, and very low 3 miles - 3 1/2 miles. I think that should be a helpful guide.
- Thermal Flash/Thermal Burst
About a millisecond after the initial burst of radiation, a nuclear bomb releases about half of its energy in the form of thermal energy, generating a heck of a lot of heat and light. One effect of this is a thermal flash which can cause permanent blindness as far as 20 miles away from the center of the blast (DC 25 Constitution saving throw to not be affected). Another effect is naturally the sheer amount of heat, which can vaporize solid steel at the center of the blast. For a 1-megaton nuclear bomb, the effects of the thermal burst are as follows: 300 points of fire damage out to 2.5 miles, 150 points of fire damage out to 5 miles, 20d6 points of fire damage out to 7.5 miles, 10d6 points of fire damage out to 10 miles, and 5d6 points of fire damage out to 20 miles. No saving throw is allowed because no, you cannot dodge a fireball that large. Any creature or object reduced to 0 hit points by fire damage from the first two range increments of the thermal burst is disintegrated.
- Electromagnetic Pulse
When a nuclear bomb explodes, the ionizing radiation it emits fries electronic circuitry. Use the same rules for a thermal burst, only the damage of the EMP effect is lightning damage, and it only affects creatures or objects with electronic circuitry.
- Blast Wave & Intense Winds
Let's not forget about the force of the explosion itself, which contrary to what some might thank is actually the cause of the majority of the damage of a nuclear explosion. Like any other bomb, when a nuclear bomb explodes, it creates massive amounts of pressure which travel outward in a wave, accompanied by incredibly strong winds. These winds can be a couple of times stronger than the strongest tornado or hurricane, reaching sufficient speeds to break the sound barrier. The winds can slam people around with lethal force, but worse they can carry debris such as boulders, trees, and entire buildings with them. Assume the following damage for a 1-megaton bomb: 20d6 points of wind damage plus 20d6 points of bludgeoning damage out to 2.5 miles, 10d6 points of wind damage plus 10d6 points of bludgeoning damage out to 5 miles, and 5d6 points of wind damage plus 5d6 points of bludgeoning damage out to 10 miles. Within the first range increment, even the most massive reinforced structures are pulverized into rubble. A DC 20 Dexterity allows a creature to take half damage. A creature protected by cover that can survive the blast wave only takes half damage, as even if they aren't out in the open they will still be violently slammed around.
Naturally, the thermal burst sets flammable things on fire like any other fire. It isn't always the case, but if a lot of vegetation is clustered together (i.e. in a forest or an area of tall grass), or if there are a lot of flammable structures built together (i.e. a dense city with a lot of wooden buildings), then the fires can join together into a central point and begin to rapidly suck out all the oxygen. This is what's called a firestorm. Following a 1-megaton nuclear bomb exploding, then the firestorm typically affects a 1.5-mile diameter area and lasts 2d4 hours. While the firestorm rages, the air in the area is unbreathable, and creatures will need to hold their breath or begin to suffocate.
- Long-term Radiation, Fallout, & Nuclear Winter
The actual area that is irradiated by a nuclear bomb is actually much larger, though less concentrated, than the initial radiation burst might lead you to believe. You see, the force of the explosion spreads radioactive dust, smoke, and other debris into the air, contaminating an area that is as large as weather patterns allow it to be. This effect is called fallout. Assume for simplicity that an area 10 times the total diameter of the radiation burst slowly decays, while a further area out to 20 times the total diameter of the radiation burst rapidly decays. The slow-decay area starts out as an area of heavy radiation, dropping one category of radioactivity every 1d4 months until it reaches low radioactivity, at which point it remains as an area of low radioactivity for the next 1d4x10 years. Meanwhile, the rapid-decay area starts out as an area of medium radiation, dropping one category of radioactivity every 1d4 weeks until it reaches very low radioactivity, at which point it remains as an area of very low radioactivity for the next 1d4 years.
Besides radioactivity, nuclear weapons can generate a "nuclear winter" effect where the dust and smoke blocks out the sun in an area, causing the temperature to plummet.
Assume damage scales proportionately to the square root of the nuclear device in question as compared to a baseline 1-megaton nuke. Let's take "Fat Man", the real-life nuclear bomb which was dropped on Nagasaki in WWII as an example. "Fat Man" was a 21 kiloton bomb, meaning it was about 1/48 as powerful as a baseline nuclear bomb in this system. The square root of 1/48 is about equal to 1/7 if you don't sweat the math too hard, so you'd divide the radii of the effects described above by 7 to get the figures you need.