Nuclear Weapons
Nuclear Weapons (High-Tech) (TL7+)
Nuclear weapons, an early TL7 development, derive their immense destructive power from nuclear fission or fusion. The energy released by a nuclear explosion takes the form of a thermal pulse (heat), concussion, hard radiation, and – in a low-altitude burst – residual radiation (fallout). A nuclear device thus inflicts crushing damage with the explosion (ex) modifier, linked to burning damage with the explosion, radiation (rad), and surge (sur) modifiers; see Damage Modifiers. Divide burning damage by only (2 × distance in yards from center of blast). Flash and Blindness always applies!
It's customary to rate a nuclear weapon's yield in terms of the quantity of TNT to which it's equivalent. This is usually expressed in kilotons (thousands of tons of TNT) or megatons (millions of tons). Nuclear explosives don't appear on the Relative Explosive Force Table, though, because most of a nuclear device's weight is that of the detonator, not the explosive.
The first atomic bomb used in war was a fission device named "Little Boy." Released over Hiroshima, Japan on August 6, 1945, it devastated the city with the equivalent of 12,500 tons of TNT, or 12.5 kilotons (6d×10,000 cr ex with 6d×6,500 burn ex rad sur linked). The hydrogen bomb, developed in the mid-1950s, further refined the art of destruction. Properly known as a thermonuclear device, this two-stage weapon employs a fission bomb to provide the incredible heat necessary to fuse hydrogen. The yield can approach 100 megatons – well beyond what fission can accomplish. At the other end of the spectrum, compact, modest-yield nuclear weapons become possible at mid-TL7. The U.S. and Russia produced miniaturized warheads weighing 50-100 lbs., with yields of about 0.1 kiloton (6d×900 cr ex with 6d×650 burn ex rad sur linked).
EMP
Unshielded electronic equipment within the visual horizon of a nuclear explosion risks a surge effect that can incapacitate it. This side effect of a nuclear blast is termed electromagnetic pulse (EMP). The larger or more numerous the bombs, the greater the EMP; for example, a 10-megaton nuclear detonation 200 miles above the center of the continental U.S. would blanket the entire country in its pulse.
Treat EMP as an Affliction that only affects electronics and those who have the Electrical disadvantage. This effect is distinct from the surge modifier on the explosion's burning damage! Every vulnerable target in the radius of the EMP suffers a HT-8(2) aff attack. A failed resistance roll means that item is knocked out of action until repaired. Affected solid-state technology is likely to be permanently damaged: all repair rolls are at -10. Repairs on other devices are at only -4.
A variety of TL7-8 military hardware is shielded entirely against EMP. Fiber-optic systems are also immune. Other equipment can be protected by surrounding it with metal that is in turn grounded.
Fallout
Residual radiation – better known as "fallout" – consists of material picked up, irradiated, and spread around by a nuclear explosion. It's generally only a factor in a "ground burst," where the nuclear weapon's fireball touches the ground. When it does occur, though, the radioactive debris distributed by the mushroom cloud poses a serious threat to anyone passing through or downwind of the blast site.
In game terms, assume that the contaminated "footprint" is an area 800 yards long by 200 yards wide, drifting downwind, for a 0.1-kiloton nuke. Double length and width for each tenfold increase in yield! Everything in this zone suffers radiation damage, measured in rads. Individuals passing through soon after the detonation are exposed to 100 rads per hour. This drops to 10 rads per hour about two days after the explosion, and to 1 rad per hour some two weeks afterward. For effects, see Radiation.
Building a Nuclear Device
Realistically, designing and building a nuclear weapon requires a team of dozens of diverse specialists, several years, and the financial resources of a small country. In a cinematic game, though, a lone gadgeteer might be able to create a "home-made" nuke. Treat this as an Amazing invention that requires the Engineer (Nuclear) skill and several pounds of weapons-grade fissionables. Since such materials are almost never available on the open market, the inventor will likely have to steal them ... or develop a working enrichment process that allows him to manufacture his own, which is a separate Amazing invention!