(Inspired by a discussion in the Discord chat)
Nuclear weapons do lots of nasty, horrible things.
Drain Constitution 20 (“immediate radiation”; Extras: Area [General, Burst, 100 ft. 5,000 radius], Linked [Damage], Linked [Drain Toughness], Linked [Transform]; PFs: Affects Insubstantial 2, Progression [Area] 5 [5 ft. to 250 ft.; 100 ft. radius to 5,000 ft. radius], Slow Fade 7 [regain 1 point of CON per week]; Drawback: Full Power)
plus Linked Transform 20 (“flash”; sighted person to blind person; Extras: Area [General, Burst, 5,000 ft. radius], Linked [Damage], Linked [Drain Constitution], Linked [Drain Toughness])
plus Linked Drain Toughness 20 (“EMP”; Extras: Affects Objects, Area [General, Burst, 5,000 ft. radius], Linked [Damage], Linked [Drain CON], Linked [Transform]; Flaws: Limited [Objects Only], Limited [Electrical Circuits Only])
plus Linked Damage 20 (“thermal blast & blast wave”; Extras: Area [General, Burst, 5,000 ft. radius], Linked [Drain CON], Linked [Drain Toughness], Linked [Transform], Secondary Effect [first is heat, second is wind + debris]).
Note: Linked Powers share power feats and drawbacks, though in this case the Affects Insubstantial should only apply to the Drain Constitution.
HOW NUCLEAR BOMBS WORK
There are basically two types of nuclear bombs: fission bombs and fusion bombs. Fission bombs work by splitting apart the large atoms of the elements uranium or plutonium. On detonation, the bomb uses high explosives to force two chunks of the fissionable material together, thus splitting one atom, which causes a chain reaction of fissioning atoms and a tremendous release of energy. Scientists refer to the smallest amount of uranium or plutonium needed to achieve this chain reaction as the “critical mass.”
Fusion bombs are generally three to four times as powerful as fission bombs. They work by fusing two or more atoms together to form a diff erent element. Usually they fuse deuterium atoms to form helium-3, or deuterium and tritium atoms to form helium-4. To cause this result, a fusion bomb uses a fission bomb as a “trigger.”
For either type of bomb, the amount of material needed to produce the nuclear explosion is surprisingly small — approximately 25 kg (55 pounds) of enriched uranium, or a mere 8 kg (18 pounds) of plutonium, are all that’s needed to make a bomb as powerful as the one used on Hiroshima (the United States and Russia can make a miniature nuke out of as little as 2.7 kg [6 pounds] of plutonium, but terrorists and criminals do not have such resources). This makes it easy for the GM to run all sorts of scenarios involving the theft or smuggling of uranium or plutonium (both of which are produced in certain types of nuclear reactors).
The construction of the bomb mechanism itself is far easier than acquiring the uranium or plutonium — in the past, college undergraduates have designed workable nuclear devices using only declassified United States government documents and readily available materials. It would certainly be possible for clever terrorists, unscrupulous scientists (including former Soviet nuclear scientists hired by criminals), or master villains to do the same. However, the machinery and technological parts needed to build the bomb may not be so easy to acquire; in many cases they are quite rare, and require highly specialized skills to build or use.
Physicists rate the force of a nuclear explosion by comparing it to an equivalent amount of tons of TNT. A kiloton (kt) equals a thousand (1,000) tons of TNT, and a megaton (Mt) equals a million (1,000,000) tons. The smallest American nuclear explosive is .1 kiloton (100 tons), and various nations have bombs ranging into the tens of megatons or higher. (The most powerful nuclear weapon ever created, the Soviet RDS-202 hydrogen bomb, aka “Tsar Bomba,” had a measured yield of 50 Mt, but some modifications could have given it a theoretical yield of 100 Mt.) Nuclear warheads have been placed on every type of launch system, from relatively short-range artillery to intercontinental ballistic missiles (ICBMs).
THE EFFECTS OF A NUCLEAR EXPLOSION
This section describes the effects of a one megaton (1 MT) nuclear bomb using the Mutants & Masterminds 2nd Edition rules. The effects of a nuclear explosion can be roughly summarized as follows:
initial explosion (immediate release of radiation, thermal blast/flash, electromagnetic pulse [EMP])
blast wave and wind effects
lingering radiation and fallout.
Ground Bursts And Air Bursts
Many of a nuke’s effects vary substantially depending upon whether the attack was a “ground burst” or an “air burst.”
In a ground burst, some or all of the nuclear fireball touches the ground. A ground burst creates a large mushroom cloud, a crater, and tremors. For example, a 1 MT bomb creates approximately a 200 meters (656 feet) crater 50-70 meters (164-229 ft.) deep (in ordinary soil), and its mushroom cloud may be as much as thirteen miles wide and ten miles high.
In an air burst, the fireball does not touch ground. For a 1 MT bomb, this means it would have to be detonated about 2,000 feet to half a mile above the ground). An air burst nuclear explosion doesn’t create a crater or tremors, but has a greater EMP.
FIRST EFFECT: IMMEDIATE RADIATION
First, a nuclear explosion releases tremendous amounts of radiation (in the form of neutrons and gamma rays). The radiation doesn’t cover as large an area as the heat or blast effects, but is nonetheless deadly (particularly to Insubstantial characters who might otherwise survive the explosion). Scientists measure the amount of radiation released in roentgens and Roentgen Absorbed Dose (rads), which describe the effects of radiation on humans. A 1 MT bomb irradiates about a 1 mile (1.6 km) radius area with over 19,000 rads, enough to kill humans instantly (if near the blast) or within minutes or hours (if slightly farther away). However, by 2 miles this drops off to about 24 rads, which is not likely to have much effect on humans. People caught between one and two miles are likely to absorb enough radiation to cause them a slow and painful death in days or weeks. Humans lacking special equipment or senses cannot detect radiation, but survivors feel its effects for the rest of their lives (however short those lives may be).
Targets within 1 mile of Ground Zero are hit with a Drain Constitution 20 (“initial radiation”; Flaw: Limited [Gradual Effect - targets take half the CON damage immediately, and the other half at a rate of 1 point per day]; PFs: Affects Insubstantial 2, Slow Fade 7 [1 point per Week]) effect.
Targets more than 1 mile away but less than 2 miles away are hit with a Drain Constitution 10 (“initial radiation”; Flaw: Limited [Gradual Effect - targets take half the CON damage immediately, and the other half at a rate of 1 point per day]; PFs: Affects Insubstantial 2, Slow Fade 7 [1 point per Week]) effect.
SECOND EFFECT: FLASH
When a nuclear bomb explodes, it immediately releases about one-third to one-half of its energy in the form of a blast of thermal energy. The nuclear fireball formed by the explosion of a 1 MT bomb is as hot as the heart of the sun and is more than 300 feet wide less than a thousandth of a second after detonation. It continues to grow (and to rise off the ground) until it’s about 2,000 feet to half a mile wide. The heat and light energy travel at just under the speed of light, and last for about two seconds.
One of the effects from this release of energy is that persons looking in the direction of the blast suffer flash-blindness or permanent eye damage (retinal burns and possibly total blindness) because of the brightness of the light. Estimates on the reach of this effect range from 13 miles to 27 miles (21 km to 43.2 km) during the day, and 53 miles to 70 miles (112 km) at night.
Those in the area of effect and who are able to see it are hit with a Transform 20 (sighted being to blind being; Extra: Duration [Continuous]; Flaw: Staged) effect. Those who fail by 1-4 have their vision impaired (-2 penalty). Those who fail by 5-9 have their vision disabled (-5 penalty). Those who fail by 10+ are rendered completely & permanently blind.
THIRD EFFECT: THERMAL BLAST
All of the heat and light described above do more than just blind people. The heat energy vaporizes metals, ignites tremendous fires (see below), and burns people. The heat travels at just under the speed of light and lasts for about two seconds.
The accompanying chart (based primarily on one found in the book Weapons, by the Diagram Group) summarizes the exact effects and range of a 1 MT thermal blast.
Nuclear Weapon Thermal Blast Radius
From 0 to 2.25 miles -- Damage 16-20 (metals vaporize)
From 1.8 to 3.5 miles -- Damage 10-15 (metals melt)
From 3.25 miles to 7.1 miles -- Damage 6-9 (rubber & plastic ignites and melts)
From 5.1 miles to 8.0 miles -- Damage 4-5 (wood and other flammables burst into flame or char)
From 7.5 miles to 10.2 miles -- Damage 3-4 (skin suffers 3rd-degree burns)
From 9.25 miles to 13.25 miles -- Damage 2-3 (skin suffers 2nd degree burns) From 11.5 miles to 18.3 miles -- Damage 1 (skin suffers first-degree burns)
An object suffers lesser burns if it’s colored white (subtract 2 ranks of effect), and greater burns if it’s black (add 2 ranks of effect). The same applies to people, based on their clothing. For notes on the possible effects of fires, see below.
FOURTH EFFECT: ELECTROMAGNETIC PULSE (EMP)
When a nuclear bomb explodes, the radiation it emits ionizes atoms for many miles around (with some airbursts, for more than 50 miles!). This takes mere fractions of a second, but can generate thousands of volts of radio wave-like energy. This energy doesn’t affect humans, but it disrupts or destroys electrical circuits.
All electrical circuits in the area of effect are hit with a Linked Drain Toughness 20 & Damage 20 effect.
FIFTH EFFECT: BLAST WAVE
The blast wave is probably the most devastating part of a nuclear explosion. The force of the explosion creates massive pressure that travels outward in a wave, accompanied by incredibly strong winds. Sometimes this effect reflects off of the ground, thereby increasing its own power (a “mach wave”). Scientists refer to the blast effect as “static overpressure” (SO), and measure it in pounds per square inch (psi) over the standard atmospheric pressure. The extreme increase in pressure can destroy buildings miles away from the center of the blast because it affects all parts of the building and crushes the structure. Anybody inside when a building collapses is likely to die. But SO has relatively little effect on soft, malleable objects like human beings — as little as 5 psi obliterates the average residential house, but a human can withstand 30 psi before suffering injury. Unless the GM rules otherwise for some reason, the SO should not affect characters, unless the characters are unusually non-resilient (for example, they’re made of metal or the like).
However, the intense winds, known as “dynamic pressure” (DP), do affect humans. They pick up all of the rubble, shards of glass, bits of metal, and other debris created by the SO and throw it against everything in their path, such as people. They also overturn cars, uproot trees, pull people out of buildings, and slam people against other objects with lethal force. As a result, one way or another a 1 MT blast kills or injures everyone within about five miles.
The effects of the blast wave can last for several seconds, depending upon the size of the bomb; with a 1 MT bomb, they should last no more than one round. The accompanying table, also adapted from Weapons, describes the effects of a 1 MT blast wave.
Blast Wave Table
Up to 1.4 miles -- Damage 16-20 (30 psi/670 mph winds. Total destruction.)
1.5 to 1.8 miles -- Damage 11-15 (20 psi/470 mph winds. Massive structures & reinforced concrete destroyed.)
1.9 to 2.0 miles -- Damage 9-10 (15 psi/380 mph winds. Multistory buildings damaged, sometimes destroyed.)
2.1 to 2.5 miles -- Damage 7-8 (10 psi/290 mph winds. Factories and commercial structures destroyed.)
2.6 to 3.1 miles -- Damage 6 (7 psi/225 mph winds. Residential structures destroyed.)
3.2 to 3.8 miles -- Damage 5 (5 psi/160 mph winds. Residential and light commercial structures badly damaged or destroyed.)
3.9 to 4.8 miles -- Damage 4 (3 psi/116 mph winds. Walls of steel-framed buildings blown away, vehicles overturned, persons in the open killed.)
4.9 to 5.9 miles -- Damage 2-3 (2 psi/70 mph winds. Wooden buildings and similar structures damaged.)
6.0 to 10.0 miles -- Damage 1-2 (1 psi/48 mph winds. Little appreciable affect.)
Blast Wave (Static Overpressure) does the Damage shown over the corresponding Area, listed above, but with the Flaw Limited (little or no effect on soft, malleable objects, including living creatures).
Blast Wave (Dynamic Pressure/Winds & Debris) does the Damage shown over the corresponding Area, listed above, without that Flaw, and with a number of ranks of the Knockback power feat equal to the rank of Damage (i.e., doing double knockback).
SIXTH EFFECT: NEGATIVE PRESSURE
After the explosion creates a static overpressure and winds blowing outward, air has to rush back in to fill the vacuum left by the outrushing winds. This negative pressure effect, though much gentler than dynamic pressure, can still cause damage due to blown objects and the like.
Damage 10 over a 5.5 mile (9 km) diameter Area.
SEVENTH EFFECT: FIRES
The tremendous heat generated by a nuclear explosion ignites any flammable objects not destroyed outright. This so-called "fire zone" within which this effect occurs covers a 5-10 mile radius for a 1 MT bomb. However, the bomb's blast wave may put out many fires (the GM decides whether this occurs, and to what extent it ameliorates the fire damage)
Damage 1, Contagious, keeps burning until extinguished or fuel is consumed.
It's also possible for the fires to join together to cause even more damage. First, there could be a conflagration: the fires spread out of control and devastate many square miles of still-standing architecture and plant life. Second, or even worse, is the firestorm, in which the fires join together in a central area and begin to suck in oxygen. The inrushing oxygen feeds the fire, turning it into a raging, self-sustaining inferno that only ends when it destroys everything flammable. No one can accurately predict whether a firestorm will start; Hiroshima suffered one, but the hillier Nagasaki only experienced a conflagration.
A firestorm Boosts the “ignite flammable objects” effect from Damage 1 to Damage 5.
EIGHTH EFFECT: RADIATION, FALLOUT, AND NUCLEAR WINTER
The lingering radiation created by a nuclear detonation can last weeks, months, or years. It's been estimated that a 1 MT explosion would force the evacuation of all people in a 4,900 square mile area around the explosion for at least a week (and in the 1,400 square mile area immediately around the explosion for a month or more). As a basic rule of thumb, GMs can use the seven-tenths rule: seven hours after the explosion, the radiation levels drop to one-tenth of what they were on hour after the explosion; 49 (7x7) hours afterwards, 1/100th, and so forth.
In addition to the localized radiation, the radioactive debris kicked into the atmosphere by a nuclear explosion eventually descends to Earth as fallout. The pattern of fallout from a given nuclear explosion depends mainly on how high it goes and what prevailing weather conditions (particularly the wind) are like.
Lastly, some authorities believe a large nuclear exchange would kick so much dust and smoke into the air that it would blot out the sun, creating "nuclear winter". In the worst-case scenario, this would mean the extinction of life on Earth as temperatures dropped below freezing and food production became impossible. However, many experts question these doomsday predictions, and in any event it would require a major nuclear exchange to create this effect, something that's unlikely to happen in most gaming campaigns.
Because the effects of lingering radiation, fallout, and nuclear winter are so unpredictable, their effects are really up to the GM to adjudicate.
[[ The preceding was taken/adapted from The HERO System Equipment Guide, a sourcebook for HERO System 5th Ed., written by Steven S. Long. ]]