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you can make the simplest atomic bomb by dropping one piece of fissile material on another, provided they are big enough to become a critical mass. My understa

by Amadou 13y ago

you can make the simplest atomic bomb by dropping one piece of fissile material on another, provided they are big enough to become a critical mass. My understanding of Ted Taylor's claims about compact fission bombs is that, absent high-grade manufacturing processes to properly shape the fissile material, we are looking at a couple of hundred kilograms to achieve critical mass. Actual "suitcase nukes" in the 10-20 kilogram range require perfectly shaped components and are also very high maintenance due to their electronics degrading rapidly from such close proximity to radiation sources. Then there is the question of testing. They say you can recognize veteran bomb makers by their missing fingers because they don't get things right the first time. Any testing of a fission bomb anywhere in the world is going to be noticed by seismographs at the very least.

archgoon 13y ago
Why is testing an issue? The Trinity test was successful on the first run. Nation-states only conduct tests to calibrate destructive capabilities and fallout effects (a non-issue if you just want a big boom) and signal to other nation-states 'Don't mess with me'. Furthermore, states such as Israel, are believed to be nuclear, without ever having conducted any (known) tests. An unsuccessful nuclear explosion would just be a dirty bomb, which would still have the desired effects from a terrorist attack perspective. So there's no real reason to test before hand.
- Amadou 13y ago
  In the case of a ultra-simple design available to terrorists that reaches critical mass by simply "dropping" one chunk of fissile material on another there is no explosion if it doesn't actually reach critical mass. Israel is a nation-state with a lot more resources available to it like the ability to measure purity and to conduct simulations. In fact a key part of nuclear politics for the last 20 or so years has been super-computer based simulations in lieu of testing. In the US the programs have been responsible for the construction of some of the largest super-computers of their time(s). https://en.wikipedia.org/wiki/Accelerated_Strategic_Computing_Initiative https://en.wikipedia.org/wiki/Accelerated_Strategic_Computin...
  - jlgreco 13y ago
    I am of the opinion that "dropping" is an exaggeration of what a gun type uranium bomb entails. Less "drop" and more "shoot with conventional explosives down a big pipe we picked up from Home Depot." Simple either way should be the take away. The hard part is getting the uranium. That is really hard.
  - justin66 13y ago
    > In the case of a ultra-simple design available to terrorists that reaches critical mass by simply "dropping" one chunk of fissile material on another there is no explosion if it doesn't actually reach critical mass. Actually, you can get a nuclear "fizzle" and if you had enough nuclear material to build a reasonable bomb that just didn't quite come off quite right, you will still get everyone's undivided attention: http://en.wikipedia.org/wiki/Fizzle_(nuclear_test) http://en.wikipedia.org/wiki/Fizzle_(nuclear_test)
- jlgreco 13y ago
  And the gun type Little Boy bomb was never tested. They used it in the field, over Hiroshima, and it worked.
  - Amadou 13y ago
    It was also manufactured with much more resources than any terrorist group could hope to muster. This is a problem in discussions of this topic - al-qaeda is not some james bond villain like goldfinger.
- justin66 13y ago
  > Why is testing an issue? The Trinity test was successful on the first run. The gun-type nuclear device which was dropped on Hiroshima was never tested at all (not enough HEU to build a test bomb and a bomb for the attack). It's fundamentally an easy machine to build if a terrorist has the nuclear material, it's easy for them to unit test the gun bits and so on, and if the nuclear material is good the final product is as sure to work as any other sophisticated bomb. All very depressing, but the point is that controlling the material is what's important. The idea that it takes a government to build the gadget itself is just plain silly, unless you're talking about a fusion device.
InclinedPlane 13y ago
The first nuclear bomb ever used in combat, "Little Boy" dropped on Hiroshima, was of a design that was previously not tested, a gun-assembly Uranium bomb. Pretty much anyone with modern off-the-shelf machine tools and enough HEU (which is the tricky part) could make such a bomb fairly easily.
snowwrestler 13y ago
According to the article, there were a couple hundred kilograms of plutonium available at that site. The situation was obviously scary enough to scientists with expertise in that field.

by Amadou 13y ago

archgoon 13y ago

Why is testing an issue? The Trinity test was successful on the first run. Nation-states only conduct tests to calibrate destructive capabilities and fallout effects (a non-issue if you just want a big boom) and signal to other nation-states 'Don't mess with me'. Furthermore, states such as Israel, are believed to be nuclear, without ever having conducted any (known) tests. An unsuccessful nuclear explosion would just be a dirty bomb, which would still have the desired effects from a terrorist attack perspective. So there's no real reason to test before hand.

Amadou 13y ago
In the case of a ultra-simple design available to terrorists that reaches critical mass by simply "dropping" one chunk of fissile material on another there is no explosion if it doesn't actually reach critical mass. Israel is a nation-state with a lot more resources available to it like the ability to measure purity and to conduct simulations. In fact a key part of nuclear politics for the last 20 or so years has been super-computer based simulations in lieu of testing. In the US the programs have been responsible for the construction of some of the largest super-computers of their time(s). https://en.wikipedia.org/wiki/Accelerated_Strategic_Computing_Initiative https://en.wikipedia.org/wiki/Accelerated_Strategic_Computin...
- jlgreco 13y ago
  I am of the opinion that "dropping" is an exaggeration of what a gun type uranium bomb entails. Less "drop" and more "shoot with conventional explosives down a big pipe we picked up from Home Depot." Simple either way should be the take away. The hard part is getting the uranium. That is really hard.
- justin66 13y ago
  > In the case of a ultra-simple design available to terrorists that reaches critical mass by simply "dropping" one chunk of fissile material on another there is no explosion if it doesn't actually reach critical mass. Actually, you can get a nuclear "fizzle" and if you had enough nuclear material to build a reasonable bomb that just didn't quite come off quite right, you will still get everyone's undivided attention: http://en.wikipedia.org/wiki/Fizzle_(nuclear_test) http://en.wikipedia.org/wiki/Fizzle_(nuclear_test)
jlgreco 13y ago
And the gun type Little Boy bomb was never tested. They used it in the field, over Hiroshima, and it worked.
- Amadou 13y ago
  It was also manufactured with much more resources than any terrorist group could hope to muster. This is a problem in discussions of this topic - al-qaeda is not some james bond villain like goldfinger.
justin66 13y ago
> Why is testing an issue? The Trinity test was successful on the first run. The gun-type nuclear device which was dropped on Hiroshima was never tested at all (not enough HEU to build a test bomb and a bomb for the attack). It's fundamentally an easy machine to build if a terrorist has the nuclear material, it's easy for them to unit test the gun bits and so on, and if the nuclear material is good the final product is as sure to work as any other sophisticated bomb. All very depressing, but the point is that controlling the material is what's important. The idea that it takes a government to build the gadget itself is just plain silly, unless you're talking about a fusion device.

InclinedPlane 13y ago

The first nuclear bomb ever used in combat, "Little Boy" dropped on Hiroshima, was of a design that was previously not tested, a gun-assembly Uranium bomb. Pretty much anyone with modern off-the-shelf machine tools and enough HEU (which is the tricky part) could make such a bomb fairly easily.

snowwrestler 13y ago

According to the article, there were a couple hundred kilograms of plutonium available at that site. The situation was obviously scary enough to scientists with expertise in that field.