Comment by credit_guy | Hacker News Reader

Comment by credit_guy | Hacker News Reader

I don't buy it.

The crucial detail to buy the story is that Jim Frank told Dobson and Selden the truth:

  They were pulled aside by a senior researcher, Jim Frank. "Jim said, 'I bet you guys want to know how it turned out,'" Dobson recalls. "We said yes. And he told us that if it had been constructed, it would have made a pretty impressive bang." How impressive, they wanted to know. "On the same order of magnitude as Hiroshima," Frank replied.

The way the project was described to work, information was going only one way (from students to researchers) with the flow the other way on a strict need-to-know basis (where need-to-know means need to know in order to deliver the results). Once the students delivered the results, there was absolutely no need for them to know if their design was successful or not. It is incredibly naive to think this was not classified.

There are now a number of options: 1. Frank disclosed classified information, 2. Frank told them some bullshit, following some instructions, 3. Frank didn't tell them anything, and Dobson and Seldon were instructed what to say if anyone asks them, 4. the whole episode is come corrupted memory: maybe Frank gave them a nice pat on the back and decades later Dobson remembered a much more impressive congratulations, just like hunters remember they shot a bigger game than they did.

From all these options I find the first one the most unlikely. By far.

I buy it.

I believe it's fairly well understood that designing a theoretical atom bomb that probably works isn't "difficult", the difficulty is building it. The logistics, and procuring the materials, that's very very hard.

Also note, they did not cover refining the fissile material as part of their process, it was assumed that they had that. Arguably it's the refining that's by far the most difficult process.

> Arguably it's the refining that's by far the most difficult process

I think a large part of what makes it difficult is not the logistics, or even the refinement process. It's the other states looking over and thinking "these guys are making atom bombs", then putting a stop to it. Much like the Iranian attempt where the US injected a worm into the centrifuges that caused them to spin themselves to death.

That kind of dramatic industrial espionage just isn’t very common outside of fiction. Uranium enrichment really is that difficult due to the precision required to build gaseous centrifuges and the nasty hydrofluoric acid chemistry involved. ITAR and other restrictions on sale of advanced machinery has much more effect than espionage - the latter is more likely to spread the technology like with Dr Khan and Pakistan/North Korea

On top of that, uranium is naturally 99.3% is non-fissile so you need tons of yellowcake to produce a small amount of weapons grade uranium, which requires crazy amount of power for the centrifuges.

> That kind of dramatic industrial espionage just isn’t very common outside of fiction.

I was making specific reference to Stuxnet, and Operation Merlin. There's been several cases of this happening, so I'd say it's hardly fictional.

I didn’t say it was fictional, I said it wasn’t very common outside of fiction.

The effects of the stuxnet virus is highly overrated. Within a few months they were replaced with a new generation of centrifuges.

Iran and North Korea have managed to figure it out. Note that the concern/news around Iran is their ability to make fissionable material, and not their ability to build a bomb if they have that material. The principals behind the bomb are (particularly the WWII bombs) are not that difficult to figure out. You can find pictures and diagrams with a simple google search. Even in WWII the hard part was getting material, not the design itself.

Making fissionable material is also conceptually easy, but the process is tricky to do without killing yourself. Still Iran has figured it out from publicly available sources (and a lot of smart people). (as the other reply points out, the process is also leaves signs that other nations are likely to pick up on)

edit: I'm not sure if Iran actually has made a working bomb, but the general consensus is they have the ability. If they don't have one it is only because between diplomatic pressure and sabotage they haven't got that far yet - absent of those two they would.

Yup. A gun-type fission bomb is very straightforward if you have access to U235.

Like fission WILL happen, the question is yield. Is it going to fizzle or will a large fraction of the fuel be burned up?

They talk about how to encourage the latter in the paper:

“The most important feature of the assembly times calculated in subsection (6) above is that they are more than 10 times the total fission chain reaction time. This means that it is essential for the fissile material to be neutron free during the assembly or the reaction will take place prematurely. If the fissile material is neutron free, then it is necessary to "turn on” neutrons to initiate the chain reaction at the desired time. This is the role of the so-called initiator”

Looking at the now-unclassified report, it appears that the results were disclosed, though, in a way that seems generally consistent with the article. Page 8 of the linked PDF (the report of this experiment, heavily redacted for public release, even now; note that it was edited by Frank) says that the outcome of the experiment was disclosed to the designers:

https://nsarchive2.gwu.edu/news/20030701/nth-country.pdf

Cripes there’s a lot of stamps on that scan

The article clearly states that they had to get clearances before they could start the job. Everything they created was top secret.

Therefore it was not necessarily in violation of any rules to tell them the outcome after they had finished their project.

Ok, but it’s in violation of their own clearance for them to give interviews about the whole affair, no?

Building a bomb isn’t a secret. Tom Clancy wrote a very technically detailed description of the tooling and process and building of a nuclear weapon in 1991 in The Sum of All Fears.

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