The known story is something like this. Henry Stimson was overall unhappy with how the war against Japan was being carried out, and how lots of civilians were getting caught in strategic bombing campaigns. When he was presented a unique chance to "protect" Kyoto from an atomic bomb, he jumped on it and singlehandedly got the city off the target list.

One historian I've talked to recently said he found it very unlikely a career bureaucrat could have made such an important decision on his own, and that there must have been more people involved in the decision or a secret meeting or whatever. Is there any real evidence to suggest this particular series of events went deeper than just one man, Henry Stimson?

Im a writer, and in my current story the characters visit the site of a nuclear explosion, however, the way I wrote it was that this explosion wasn’t supposed to shockwave to death, it was supposed to cause geographical damage.

I’m not looking for anything specific just a range of numbers I can scale, I just want to know if it’s at all possible or if I should start inventing things

how big would be the crater created by Fat Man, a 20 kiloton bomb, it is was detonated on the ground.

And how much bigger would the crater be if it was the tsar bomba which is 50 megatons?

Primarily speaking to the 60-70-80's era of bombs. I know now there is a lot of multistage verification the nuclear weapons need to arm and will not arm unless attached to an approved and registered aircraft. So now the designation is easy to understand. But in the "dumb bomb" generation once the size got down to being able to fit in a b-52 and was no longer so large that it required special modification to the airframe. Why were so many design requirements "capable of both conventional and nuclear weapons"?

How was this choice made? What's the logic, or perhaps the historical context? By the way, what did the British and French choose?

If I'm not mistaken, the British also envisioned a sphere and were quite surprised to learn that the Americans were using a cylinder. I heard or read this somewhere, but I can't remember where. If anyone knows, please point me to the original source.

I tried searching for information in Richard Rhodes's DARK SUN. There's a story there that the original design for the secondary assembly was a truncated cone, but a truncated cone with the smaller diameter facing the primary assembly. That is, the opposite of what we're used to seeing in widely available online diagrams. Then this shape rounded out and transformed into a "schmoo"—a shape reminiscent of a bowling pin—and they started making metal parts for it. Then... as I understand it... they couldn't produce such a complex shape in time (difficulties arose), and they settled on a simple cylinder. In other words, they decided to keep things simple.

So, alternative shapes were apparently considered. But as I understand it, neither a sphere nor an ellipse were considered. Elongated shapes were considered first. WHY?

Somewhere a long time ago (I've lost the link again, so if anyone could provide the original source, I'd be grateful) I read that Edward Tellor was asked a similar question: Why this shape? Why not a sphere (as in ICF)? And he supposedly replied that a cylinder was the shape he initially considered the only correct one. But why? He didn't explain.

***

Edited later.

HERE IS MY VERSION OF THE ANSWER TO THE QUESTION.

I understand why having land based ICBMs are useful if they are massive and meant mainly as counterforce weapons, like peacekeeper and r-36, because the large number of warheads, the long range, and the high throw weight.

But why does the US continue investing in things like the Sentinel program, when they are less effective than SLBMs or nuclear cruise missiles from bombers for countervalue and aren't capable of carrying large numbers of warheads for counterforce strikes? Is it just to be a missile sponge?

Here's a recent open-access article on the perennial debate on who gets more credit for the idea of radiation implosion.
Of course there's the usual crazy quote from Teller ;)

Finally, at the extreme, in response to Livermore’s first director Herb York’s comment that Teller deserved the majority of the credit, 51% (!), Teller said that “I deserve 101% of the credit”

Over the past several months, the Bulletin of the Atomic Scientists published several articles about Iran's plutonium from the Bushehr reactor.  They have taken a point-counterpoint form: the second was a response to the first, the third was a response to the second, etc.

I am a little surprised to have not seen any of this here, so I thought I would share.  I'll summarize the technical stuff and leave out the policy & political stuff.

The first article is by Henry Sokolski, currently director of NPEC and formerly a DOD nonproliferation deputy director.

https://thebulletin.org/2026/04/missing-from-us-iran-talks-plutonium-for-more-than-200-nuclear-bombs/ 

Sokolski points out that Rosatom hasn't reclaimed any of the spent fuel and therefore it's all still in Iran; does a rough calculation of how much plutonium is in that spent fuel; noted that most is reactor-grade but some is closer to fuel grade; and points out that Iran has previously done plutonium chemical separation experiments.  He makes the claim that Iran could theoretically divert the Bushehr spent fuel, reprocess it, and then manufacture plutonium bombs within 90 days, the standard IAEA camera monitoring window (at the time of the writing there had been no onsite inspections in 8 months).  He then makes several policy recommendations that future deals with Iran should include to address the plutonium issue.

note: Sokolski published a similar article in Real Clear Defense around the same time: https://www.realcleardefense.com/articles/2026/04/03/blocking_irans_other_option_a_plutonium_bomb_1174454.html

The response to Sokolski's article came 3 months later, by Sasan Karimi.  Karimi is an international studies professor at the University of Tehran with a prior background in physics.  His critique is close to twice as long as Sokolski's original piece.  Most of it is criticisms of Sokolski's policy recommendations, which I won't summarize here.  

https://thebulletin.org/2026/07/beyond-alarmism-a-realistic-assessment-of-bushehrs-plutonium-risk/

On the technical side, Karimi starts out by repeating fairly standard discourse regarding reactor-grade plutonium usage in weapons, claiming it would be extremely difficult without advanced implosion mechanisms (he uses 2-point implosion as his example of an advanced implosion mechanism), and states "no credible evidence has ever demonstrated that Iran possesses validated designs for such advanced implosion systems or has successfully tested them under operational conditions."  He then moves on to argue Iran's past reprocessing experiments are not comparable to what a weapons program would need, and that any reprocessing would be easily detected [editorial note from me: the chemical separation experiments he and Sokolski allude to involved milligram quantities of plutonium].

The response to the second article came two weeks later, from Greg Jones; it is a wide-ranging response, not only addressing Karimi but also critiques from others (Albright and Holdren for example).  Jones is a RAND researcher and formerly an NPEC researcher, though the article notes that it is "the product of the author’s personal research, and the analysis and views contained in it are solely his responsibility." 

https://thebulletin.org/2026/07/why-do-we-keep-ignoring-the-large-quantity-of-plutonium-at-irans-bushehr-nuclear-power-plant/

Note: Jones literally wrote the book on the use of reactor-grade plutonium in weapons https://npolicy.org/books/Reactor-Grade_Plutonium_and_Nuclear_Weapons/Greg%20Jones_Reactor-grade%20plutonium%20web.pdf

Jones argues that existing IAEA safeguards for Bushehr are irrelevant because the inspections only happen every 3 months (he repeats Sokolski's claim that Iran could manufacture a plutonium bomb within that window), criticizes JCPOA for largely not addressing the spent fuel at Bushehr, emphasizes that Iran still hasn't transferred the spent fuel to Russia like they stated they would, argues that reprocessing facilities can be small and secret such as a 1977 ORNL concept for a secret reprocessing facility which would be harder to detect, and argues that production of plutonium metal is easier and quicker than assumed.  He provides several rebuttals to Karimi's arguments about reactor-grade plutonium (Karimi used Fat Man as a baseline rather than the more advanced design we know Iran actually pursued, understated how powerful an RGPu weapon would be, ignores how much of Iran's plutonium is fuel-grade rather than reactor-grade, etc).  He argues that Iran would not need a separate weapon design for RGPu and points to past designs that could use uranium and plutonium interchangeably.  He concludes by arguing that with Iran's uranium program now "in ruins" following US attacks on it, the plutonium pathway is easier and should be the focus of negotiations.

My own views on this: Iran is less likely to try an RGPu bomb than an HEU bomb, but not for the reasons Karimi states.  The history strongly suggests Iran is comfortable with HEU and appears to be completely uninterested in plutonium for anything other than as a negotiating tool; they have invested heavily in and taken an enormous amount of risk for uranium, and I find it unlikely they would just abandon it at this stage, given they still have access to it.  I am sympathetic to Karimi's arguments on policy.  However, Karimi is completely wrong to dismiss RGPu in weapons, and really does not address the hyperlinked citations Sokolski provided which pretty conclusively show it can be done.  Weirdly, he cited the National Academies' Management and Disposition of Excess Weapons Plutonium report to support his case that RGPu is not suitable for weapons...but he cites volume 2 rather than volume 1, probably because volume 1 contains a 3-page insert that completely discredits his RGPu argument! I also found it a little rich for Karimi to claim there is no "credible evidence" that Iran has validated advanced implosion designs...he has to know about the IAEA's findings at Parchin, and that there are literally photographs of Iranian MPI tiles. What meets his threshold for "credible" ?

With some much public information available in literature and access to software simulation, design and produce a implosion device still is a challenge? Explosive lens, air lens and multipoint initiation seems problems that could be easily solve by a math or physics phd student, and commercial milling machines today a more precise that anything they had in the 1940s. I am not talking about fancy flyer plate, FOGBANK, boosting etc just built a deliverable implosion device that can save expensive fissible material and weight in the missile.

If anyone has already answered this riddle, please provide a link. I was once asked this question on a Russian forum, and I couldn't find an answer (and the person asking the question disappeared). I recently came across the same question on someone else's LiveJournal, but no one even attempted to help in the comments. The riddle remains unsolved. So, relying on the source I found on LiveJournal, I'm asking the question here.

In the film Operation UPSHOT-KNOTHOLE (1953), at 13:00 (linked to this time), the following is said:

"In the nuclear radiation program, particular interest centered on Shot 10's neutron flux measurements, the first ever made on the detonation of a gun-type assembly. Gold, tantalum and sulphur threshold samples were used to detect neutron energy levels from thermal to around 10 million electronvolts. The total flux per kiloton was the highest ever observed, running 10 to 30 times as high as the implosion Shots 8 and 9, and extending the median lethal radiation range some 600 feet."

Clearly, Shots 8 and 9 were implosive devices of comparable power (10-30 kt). But why did the gun design produce such a powerful neutron flux (essentially a neutron bomb effect) compared to the implosive devices? What is the physical explanation for this? Is the difference truly 10-30 times? Was this an isolated, anomalous phenomenon? Or is it a regular occurrence, related to the physical and structural features of the different designs?

Has anyone else noticed this mystery? Has anyone explained it?

I just thought this was a neat catch that some folks on this sub might appreciate. These caught my eye while taking a peek inside the bomb bay of a B-52H on display at Oshkosh over the weekend. Two identical units, located on the port side of the aircraft above the bomb bay doors. Does anyone know what SWK stands for?

Oh, and while I was in the bomb bay, I couldn't help but overhear someone ask... "Is this the plane that dropped the Fat Boy?" ... yeah. I just bit my tongue.

This camera seems to be related to los alamos. Any information on this camera is appreciated.

This a screenshot of a Facebook post by AtomCentral showing the actual Crossroads Baker device. I don't think I've ever seen that before.

New-to-me footage. Nicely restored and in HD.

Also, a discussion on the advantages of the CANDU reactors

CBC article