You can classify the laws of physics. It’s just not likely to be very effective when you do.
You need to say it like this: Ye canna change the laws of physics!
Pretty much a lot of the 1945 designs of nuclear are declassified.
The big snag - particularly compared to anything else from the period - is that 1945-style weapons are exactly what hostile powers want to currently build. So there is the level of 1945-detail that remains supposedly deeply classified. Yet, while obviously personally biased, I suspect these are areas where it’s pretty much been figured out online.
By “1945-style”, do you mean a basic concept like an implosion design to achieve supercriticality? Because a nuclear weapon designed today would not be a straightforward copy of anything from 1945. You would be engineering it from scratch (or a more modern design) anyway, with the benefit of modern simulation software.
[nitpickle]The problem was actually with impurities in the supply of PU-239, namely minute amounts of PU-240 that couldn’t be easily extracted. But the effect was the same. There was work on a gun-type Plutonium bomb called Thin Man that was abandoned when this was figured out. [/nitpickle]
Reading around about the U.S. atomic weapons program, it’s amazing at how ad hoc everything was. I mean, I guess they HAD to be that way, because they were doing things never done before, but geez. They dropped only the SECOND bomb ever made on Japan, without even testing the design?! And attention to security was so mediocre that the U.S.S.R. stole all kinds of info to help them build their own??!
Well, PU-240 has a horrible spontaneous fission rate, but PU-239 is pretty bad. I don’t feel like doing the calculations to determine if pure PU-239 is low enough to use in a gun-type bomb. I suspect it isn’t.
As for security, it was extremely tight (all mail was censored, for example). But, spies have their ways.
As an aside - tight security is a security risk in itself. Just like the “Spectre” flaw in Intel chips, the fact that mail from Los Alamos was being censored leaks information that something important is happening there.
ETA: if the PU-240 contamination is bad enough, then even an implosion-type bomb won’t work. This is a major component of nuclear non-proliferation - long fuel-cycle Uranium can’t be diverted to make bombs, because it’s too contaminated by PU-40.
I forgot to add, a simple nuclear gravity bomb is a lot less useful today than it was in 1945.
The illusion of security was very tight. The reality was different. Like, everyone had a combination-locked filing cabinet, with customizable combinations… which means that half of the combos were just left at the default, and the rest were all things you could guess if you knew the owner of the safe. Or not even need to guess, if you were ever in that office when it was open.
Well, yes, Dr. Feynman.
But, the secrets that were stolen weren’t pilfered from a safe - they were deliberately given to the soviets by one of the senior scientists, working under Hans Bethe.
And Richard Feynman famously picked those locks.
For those interested in the history and the atmosphere of Los Alamos during the Manhattan Project, I cannot recommend this book highly enough:
109 East Palace: Robert Oppenheimer and the Secret City of Los Alamos
by Jennet Connant.
Not only is Ms. Connant a skilled and entertaining writer, but also her grandfather, James B. Connant, was an administrator at Los Alamos during the Manhattan Project.
Why is that so?
I thought this thread was going to be about Gerald Bull
In response to the claim that a gun-type gravity bomb is less useful than it was in 1945:
Atomic/nuclear gravity bombs of any kind are less useful because it’s comparatively easy to to defend against the aircraft required to drop a gravity bomb. The preferred delivery mechanism nowadays is an ICBM with multiple-re-entry warheads.
What’s more, hydrogen bombs (involving fission in one way or another) are all the rage these days, and while you might be able to use a gun-type fission weapon as a primary (to set off the fusion secondary), I’m not aware of any design that has done this. Then again, I’m not aware of any particular design beyond what’s publicly available on the interwebs.
One of the reasons that gun-type assembly is no longer used is it’s extreme inefficiency. Fat Man was about 10x as efficient as Little Boy. Also, since Plutonium is easier to make than HEU, it’s pretty clear that nobody is going to be making gun-type weapons anymore.
Unless of course, they intend to fire them out of a gun, or use them in some other kind of rugged application- the last uses of the gun-type weapons was in nuclear artillery shells for that reason.
The thing with the gun-type bombs is that they’re not quite as finicky about the exact timing as implosion-type weapons are. As a result, they’re more rugged and more reliable, and the Manhattan Project scientists were confident enough of the U235 gun type weapon (“Little Boy”) that they didn’t think they needed to test it prior to use.
Of course the tradeoff is that gun-type weapons are dreadfully inefficient relative to implosion type weapons. Little Boy used 64 kilograms of U235 to get a yield of 15 kilotons, while Fat Man (implosion type) used 6.4 kilograms of Pu-239 to generate a 21 kiloton yield. So ten times as much fissile material in a gun-type bomb generated 3/4 the yield of the first implosion design.
As far as the venting of the gun barrel goes, the air itself isn’t important, but rather that an unvented barrel and consequent pressure rise could decelerate the projectile significantly and result in a lower yield, or even a fizzle due to predetonation*, if the two parts weren’t “assembled” fast enough.
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- Predetonation is the phenomenon where neutrons start fissioning material before the bomb is in the right configuration, and these early fissions destroy enough of the fissile material to render the bomb useless, or significantly reduce the yield. In the case of gun weapons, if you put the two parts together too slowly, they start to predetonate before they come together, and you end up with drastically reduced yield. Also, with plutonium, the Pu-240 impurities have such high spontaneous fission rates that gun type weapons cannot put the two parts together fast enough to prevent predetonation because of all the neutrons whizzing around.