5 ms·

Cleaner designs tend to leave out the final fission stage in the standard fission-fusion-fission "H-bomb" design - as this is where most energy is generated eve

Cleaner designs tend to leave out the final fission stage in the standard fission-fusion-fission "H-bomb" design - as this is where most energy is generated even though fissioning uranium with neutrons from the fusion step is, I believe, inherently messy. Edit: I'd have thought the biggest factor in how messy things would be is whether it is a ground or air burst, rather than the weapon design.

formerly_proven 5y ago
Is radioactive fallout from a thermo-nuclear weapon an important consideration (compared to the destruction of the "thermo" part)? The bombs dropped in Japan only contained a few kg of fissile material, those cities were rebuilt within years. Modern bombs are probably way bigger, but even a W78 warhead comes in at only 120 kg or so and I'm guessing most of that is not plutonium. Compare this to the thousands of tons of radioactive or activated material that flew around Europe following the steam explosion at Chernobyl.
- arethuza 5y ago
  According to Daniel Ellsberg the only thing considered by US planners was blast yield - fallout and direct radiation (particularly thermal effects) were ignored as their effects were regarded as too unpredictable. This was in the 1960s though - things may have changed. edit: Fall out, even with modern weapons, would be a huge consideration if you are downwind of a target likely to be hit by a surface burst. You can experiment on Nukemap with the different options: https://nuclearsecrecy.com/nukemap/ https://nuclearsecrecy.com/nukemap/
  - CapitalistCartr 5y ago
    It hadn't in the Eighties. If you want to be a nuclear war planner, I suggest Nukemap. https://nuclearsecrecy.com/nukemap/ https://nuclearsecrecy.com/nukemap/ No more plastic wheels to spin like a sliderule. Want to take out a target? What's your weapon system's CEP (Circle of Equal Probability)? How is the target built, that is, how much overpressure to destroy it, and how deeply buried is it? Now choose a weapon. If it'a high-priority target, aim more than one weapon at it.
- caf 5y ago
  The fallout by mass isn't primarily the direct daughter products of the fission. It's the thousands of tonnes of pulverised dirt and rock (and concrete and steel and...) that has been neutron-activated and ejected high into the atmosphere.
  - refurb 5y ago
    This was my understanding as well. Radiation levels of daughter products from the weapon drop quite quickly. But the dirt that’s been neutron activated can take a while to come back down and the exposure levels are much higher.
CapitalistCartr 5y ago
Air versus ground is a major factor. In the early days, we targeted whole cities with air bursts, relying on a WWII mentality to warfare. Then, as we gained the ability to target specific military installations, which simultaneously became more hardened, we moved to high ground bursts, then impact bursts, which pretty much means a huge mess. We can easily dig a hole in the ground 60 meters deep, but that means a staggering amount of debris high in the air, some of which will be radioactive.

formerly_proven 5y ago

Is radioactive fallout from a thermo-nuclear weapon an important consideration (compared to the destruction of the "thermo" part)? The bombs dropped in Japan only contained a few kg of fissile material, those cities were rebuilt within years. Modern bombs are probably way bigger, but even a W78 warhead comes in at only 120 kg or so and I'm guessing most of that is not plutonium. Compare this to the thousands of tons of radioactive or activated material that flew around Europe following the steam explosion at Chernobyl.

arethuza 5y ago
According to Daniel Ellsberg the only thing considered by US planners was blast yield - fallout and direct radiation (particularly thermal effects) were ignored as their effects were regarded as too unpredictable. This was in the 1960s though - things may have changed. edit: Fall out, even with modern weapons, would be a huge consideration if you are downwind of a target likely to be hit by a surface burst. You can experiment on Nukemap with the different options: https://nuclearsecrecy.com/nukemap/ https://nuclearsecrecy.com/nukemap/
- CapitalistCartr 5y ago
  It hadn't in the Eighties. If you want to be a nuclear war planner, I suggest Nukemap. https://nuclearsecrecy.com/nukemap/ https://nuclearsecrecy.com/nukemap/ No more plastic wheels to spin like a sliderule. Want to take out a target? What's your weapon system's CEP (Circle of Equal Probability)? How is the target built, that is, how much overpressure to destroy it, and how deeply buried is it? Now choose a weapon. If it'a high-priority target, aim more than one weapon at it.
caf 5y ago
The fallout by mass isn't primarily the direct daughter products of the fission. It's the thousands of tonnes of pulverised dirt and rock (and concrete and steel and...) that has been neutron-activated and ejected high into the atmosphere.
- refurb 5y ago
  This was my understanding as well. Radiation levels of daughter products from the weapon drop quite quickly. But the dirt that’s been neutron activated can take a while to come back down and the exposure levels are much higher.

CapitalistCartr 5y ago

Air versus ground is a major factor. In the early days, we targeted whole cities with air bursts, relying on a WWII mentality to warfare. Then, as we gained the ability to target specific military installations, which simultaneously became more hardened, we moved to high ground bursts, then impact bursts, which pretty much means a huge mess. We can easily dig a hole in the ground 60 meters deep, but that means a staggering amount of debris high in the air, some of which will be radioactive.