I don’t think you can participate meaningfully in an extended discussion about the bomb without reading Rhodes’s book, unless you’ve somehow read all the equivalent material elsewhere. It and to a slightly lesser degree the follow-up Dark Sun are one of the finest, most complete and most insightful modern histories I’ve ever read.
No, I understand that different engineering processes are used to get the final result, but it is exactly the same final process and result - quickly creating a critical mass that then releases some very large part of its energy. You could compare various forms of IC engine or various forms of jet engine, but the difference between those two is much greater than the difference between the two bomb techniques. IMVHO.
A piston compressing a fuel mixture and a Wankel rotor compressing a fuel mixture is very close to an exact analogue… again IMHO.
Might want to inform the people of Hiroshima that they should move.
Hmmm…not bad!
Well, given History Channel’s penchant for fabulification, I expect the next one to claim that the Nazis had the bomb and tested it and that’s why all the people in the concentration camps were sick and dying.
People seem to not notice that Hiroshima and Nagasaki are healthy large inhabited cities and not radioactive wastelands from science fiction.
And any seven-foot, three-eyed denizen of those cities will be happy to give you a taste of his bottom-left tentacle should you imply it!
There was an incident with Uranium, however. Mind you it was equipment failure and not anything like a critical mass situation.
Fight my ignorance here. How is the mechanism for fissioning uranium different from the fissioning of plutonium?
You can answer for controlled fission (aka reactor) as well as uncontrolled (aka bomb).
When atoms split they give off stray neutrons. Those neutrons then hit other atoms causing them to split as well. If you put enough radioactive material – a critical mass – in one place you get an out of control chain reaction that produces a big explosion.
An atom bomb consists of separate pieces of radioactive material that can be brought together to form a critical mass. This has to happen quickly because once the chain reaction starts the increasing heat and pressure blows the pieces apart. If the assembly of the pieces happens too slowly the result is a fizzle – a small explosion that blows the core apart before very much fission happens.
Uranium bombs work like cannons. You set off a normal explosion to fire a “bullet” of uranium into a “target” of uranium. This creates a critical mass quickly enough to avoid a fizzle.
Plutonium is so reactive that even a cannon isn’t fast enough to get the pieces together in time. Plutonium bombs work through implosion. A hollow sphere of plutonium is surrounded by a spherical jacket of explosives. When the explosives detonate it creates a spherical shock wave that compresses the plutonium into a critical mass.
Designing an explosive jacket that will produce a perfectly spherical implosion is very, very hard.
Thanx Hamster. Got that. I knew the basic principle of critical mass and that Pu is more reactive. (And not naturally available.) I didn’t know the implications for bomb design or that the spherical implosion was so difficult to achieve.
And there were a very limited number of Wicked Witches left to drop those houses on.
That’s an interesting point—never even occurred to me before. Is there any measurable radiation at all left over from the blasts?
As an interesting sidenote, there actually have been a couple of Uranium-implosion bomb designs—the bomb used in the Ivy King test and the first Chinese atomic bomb, for example.
just to nitpick - the Plutonium pit is not, strictly speaking, hollow. There is a small, spherical “spark plug” that resides at the center of the pit, but that is only there to provide enough free Neutrons at the moment of maximum compression to initiate the reaction. Interestingly, the Manhattan- era design of this initiator is considered one of the top secrets of the bomb, and AFAIK, it’s design is still classified 70-odd years later. If this initiator was not necessary, a perfectly round, solid sphere of PU-239 could be used. In other words, it’s not the “crushing” of a hollow sphere that makes the mass go critical, it’s the actual change in density caused by the compression of the explosive force.
62 tons, in fact. Meet Ivy Mike.
More or less. The Teller-Ulam design is used for all modern thermonuclear weapons, and although heavily classified, the basics are assumed to be as described in the Wikipedia article. A “primary” plutonium fission bomb provides heat, x-rays and compression to ignite a “secondary” supply of fusion fuel, and that in turn usually fissions the uranium “tamper” (heavy shell that contained the initial explosions for a few milliseconds to allow fusion to start). It’s a convenient factor that the more common uranium isotope U-238, which does not normally fission, is dense enough to serve as an ideal tamper and also will fission under the neutron flux caused by the fusion explosion. Often, the majority of a bomb’s “yield” is actually caused by this third-stage fissioning of the tamper.
It’s diabolically clever and efficient. Elegant…except for being the worst thing ever conceived.
Pripyat, OTOH…
What makes you think a few kiloton nuclear bomb being detonated would require fencing off an area a “hundred square miles?” I wouldn’t have wanted to live on top of ground zero in Hiroshima a year after the bombing but lots of people did and the impact was fairly minimal. Especially relative to WWII era norms where governments threw away thousands of lives a day. I think something like 1500 cancers over a 50 year period in which hundreds of thousands of people lived in Hiroshima have been attributed to radiation effects from the bombings.
I’m always in shock at how people seem to have all these crazy ideas about what nuclear weapons do and this is one of the most frequent, that any area hit by any type of nuclear weapon becomes “uninhabitable” forever. The radiation levels that can actually kill humans outright dissipate very quickly from a Little Boy type bomb, and the amount left wouldn’t be enough for a war time government to quarantine off the area forever. Maybe in c. 2013 United States or Europe they’d just quarantine it off, because there’s no acceptance for sacrificing a small portion of people to the side effects, but we’re talking the 1940s here and Japanese controlled Korea.
Okay, seriously, this did not happen. There’s no way Japan ever built an atomic bomb.
The United States occupied Japan after the war and had full access to all its secrets. There’s no way the Japanese government would have been able to hide a development program much less actual production and use of an atomic bomb.
The United States made a big point out of how the Manhattan Project was a response to fears of a German atomic bomb program. Full publicity was given to the German program after the war. Why wouldn’t a more successful Japanese program have also been publicized? America had every reason to portray Hiroshima and Nagasaki as responses to a Japanese bombing if they could have.
The Koreans have long complained about Japanese treatment of their country. Why would they not talk about it if Japan had used an atomic bomb in their country?
Japanese research in chemical and biological weapons has been publicized. Why would Japanese research in nuclear weapons be concealed?