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"Nuclear Archaeology" Inspires Replica of Hiroshima's Little Boy
James Cho writes "Through a decade of painstaking reverse engineering, trucker John Coster-Mullen built the first accurate replica of the Hiroshima bomb. His work yielded a new history of the first nukes, 'Atom Bombs: The Top Secret Inside Story of Little Boy and Fat Man,' with historian Robert Norris saying, 'Nothing else in the Manhattan Project literature comes close.' Philip Morrison, one of the physicists who helped invent the bomb, deemed it 'a remarkable job.'"
"Reverse engineering" is a pretty broad phrase. It can mean anything from taking an actual working example of a machine and figuring out how to build it, to the kind of thing you're talking about, observing what a machine does and figuring out how to build something that does the same thing (whether or not the internal mechanism is the same.) I'd say what Coster-Mullen did falls right in the middle of this range, so calling it "reverse engineering" is fair.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
The Hiroshima bomb was a very simple "gun" design. Plenty of published info on it. It used a navy gun barrel cut down to size, a U235 doughnut target, a polonium initiator, and a U235 projectile. Mighty simple. Any chopper shop could build one, with the exception of getting the Polonium and U235.
This design was abandoned as it had many drawbacks-- it used about 8 times more U235 than absolutely necessary, there was a 7% chance of a fizzle, and there was no way to make it safe.
But it had the advantage that it was dead-simple and guaranteed to work, well 93% of the time.
Now if he made a replica of Fat Man, that would really be something.
There are a lot of stories that appear on /. in which I have absolutely no interest. (The same could be said by practically anyone here.) So you know what I do when one of those stories comes up on the front page? I don't click on it. Easy, simple solution -- let the people who do care about that particular story talk about it, and go find something I care about to read and comment on instead. Everybody wins. It's not that hard a concept to grasp.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
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Besides, a lot of the difficulty in making even an inefficient nuclear bomb at all obtaining the weapons grade fissile material.
I'd say that the vast majority of the difficulty is obtaining the fissile material. Weapons grade uranium/plutonium doesn't exactly grow on trees. Creating it yourself (and preventing anyone from stopping you) takes the power of a government.
This has essentially been the policy to control proliferation for 60 years now. Stopping the knowledge of the design details is merely security theater.
AccountKiller
Its a little sad to skim through the posts on this story and find pretty much all of them are lame.
Its a long article but its really a fascinating read and I'm guessing almost no one did. It makes a couple really insightful points:
A. All of the U.S. governments obsessive secrecy about nuclear bomb technology is pure security theater. The hard part is mastering the fuel cycle. If you can acquire the fuel or master the fuel cycle, making the bomb is pretty easy.
B. Much of what we read and take for authoritative is in fact garbage. There have apparently been a number of works on Fat Man and Little Boy, often by well educated and authoritative authors that were apparently complete nonsense. It just took an obsessive photographer/truck driver with no college degree to debunk one authoritative work after another. In particular apparently everyone thought the Uranium bomb was a female target shot with a male shaped projectile because thats the way people expected it to be, when in fact it appears it was the other way around.
One also wonders if the U.S. government intentionally propagated nonsense in these "authoritative" works thinking it would set back some aspiring bomb maker. For example, in one work it apparently said the barrel in the Uranium bomb was made of wood which was apparently pretty comical since it had to contain the explosion of several bags of cordite.
@de_machina
Actually, it is a pair of nested cylinders, and the rationale behind it is brilliant.
To get the biggest possible boom, you want to bring together the largest possible mass of fissile material. Problem: if you accumulate too large a mass, it starts a chain reaction on its own.
But if you form that mass into a ring shape, and make the hole in the ring large enough, you create extra surface area for neutrons to escape, but the gap is too big for them to have sufficient energy to split an atom on the other side of the gap.
For a given outer diameter (fixed by the inner diameter of the bomb casing) the maximum mass of fissile material is obtained with a cylinder whose height is determined by the mass on the "side" of the cylinder nox exceeding criticality. A mating cone shape results in a smaller usuable mass.
So why make the projectile hollow instead of shooting a slug into a hollow target? Because the sides of the gun barrel constrain the movement of the projectile and ensure that the mating surfaces are aligned.
It's actually, for such a "crude" design, brilliant engineering.
DG
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