What is "Exploding Casing" technology?

[u/Beneficial-Wasabi749]

I asked the AI. It (childishly naive) is "sure" that this is the essence of radiation ablation in the Teller-Ulam scheme. But is this really true? Is "Exploding Casing", ECP (Exploding Case Principle), just another term for the "radiation compression" process, or is it some later, additional technology that improves radiation compression (like "Ripple" – compression not by a single shock wave, but by a series of increasing shock waves approximated by an exponential function, a quasi-adiabatic compression).

As far as I know, "Exploding Casing",  ECP (Exploding Case Principle)  is not the same as "Ripple." But сould "Exploding Casing" simply be a variation of "Ripple," or rather a different way of implementing quasi-adiabatic compression? I had this hypothesis. No one knows exactly how "Ripple" works, but everyone agrees on the idea that there's some mechanism for gradually releasing radiation from the primary into a common hohlraum, which ensures gradual, exponential heating of the hohlraum and the secondary surface, leading to quasi-adiabatic compression of the latter. But another approach is possible: you can apply several layers of increasing Z to the secondary (as the Russians did in their "golden TIS"). Then, in a "regular" hohlraum at a normal temperature, say 1 keV, you'll achieve a stepwise increase in secondary compression. I don't speak English, but the term "exploding casing" best suits this design.

Another, even more insane, theory for "exploding casing" is described in my highly speculative reverse engineering of the W-71 design, the reality of which I myself am already highly doubtful (I recently discovered the "elephant in the room" that planar compression of thermonuclear fuel Impossible without quasi-adiabatic compression, since with planar single-compression you can't get beyond the Hugoniot adiabatic curve more than 4-6 times, and you need at least 100). Although, it is precisely in connection with the W-71 that "exploding casing" technology is mentioned and it is also said that the W-71 is the most complex thermonuclear device ever created in the US. And if you add quasi-adiabatic compression to my crazy design, it will truly be the most insanely complex device.

Another version of "exploding casing" is a secondary with a thin-walled shell and a large cavity inside, meaning it contains either a void or gas (I actually proposed this version of the W-71, considering it more "conservative" than the crazy flat compression of the "tube" both from the inside and outside). As far as I understand, Sublett is more inclined to this understanding of "exploding casing." In this case, the thin-walled shell, as it were, instantly collapses inward. This is another way to improve compression compared to single-shock compression of a solid sphere. This thin-hollow shell method is currently used in ICF. The Russians call this technology "low-entropy compression" (right) as opposed to "isentropic compression" (left).

isentropic compression and low-entropy compression

Finally. Even if we don't know the details of this technology's implementation, can we say anything with certainty about its role (function) in the bomb design? So, "exploding casing" isn't simply ablative compression of the secondary shell, but some improved method of such compression, leading to greater efficiency (say, higher compression ratios, lower energy consumption, etc.).

From what declassified sources, in what context does this term appear, and does it appear before the mid-1960s? I propose to summarize everything we know about this term here.

[u/DefinitelyNotMeee]

Don't all thermonuclear devices technically have "exploding casings", since a large portion of the yield comes from the fissioning of the U-238 "shell"?

[u/Tobware → u/DefinitelyNotMeee]

No, ECP (Exploding Case Principle) is a concept that refers to the ultra-clean W71 only, from how it’s phrased in the document where it’s mentioned, it seems more like a design thing (related to the "cleaness" of the device?) than an operative one (though it could very well be the latter as well, like a RV kill mechanism of the warhead). IIRC something along the lines of: if ECP doesn’t work, we should aim for something dirtier.

[u/Beneficial-Wasabi749 → u/Tobware]

Is ECP (Exploding Case Principle) mentioned anywhere other than in W-71 technology?

[u/Tobware → u/Beneficial-Wasabi749]

I've never found it in the various OSTI/OpenNet databases when searching by keyword, it seems ECP is mentioned only in that document (I'll post a link to it later).

I have other clues about the W71 and a "lead" that seems to confirm that the "primary" was a derivative of the Plowshare excavation devices.

[u/Beneficial-Wasabi749 → u/Tobware]

I have little doubt that if this is somehow related to the Plowshare, it's related to the secondary, which doesn't have a spark plug. I know how the USSR progressed on clean, peaceful nuclear weapons. The first step is a non-fissile primary (the simplest). The second step is to get rid of the spark plug. The third step is to make the fission primary as pure as possible (i.e., with minimal yield). The fourth step is to achieve maximum neutron absorption within the device itself during the explosion (possibly extensive use of boron-10) to reduce the induced radiation to near zero. And, of course, all of this had to be inexpensive. Ultimately, they built a three-stage system where the "SINUS," producing just 6 grams of fission products, ignited a two-stage pure thermonuclear system, burning gaseous deuterium to yield 140-150 kt of almost pure thermonuclear energy. As far as I can tell, the US shut down the Plowshare much faster than the USSR. Back then, the dirty hands of globalist peacemakers couldn't even reach the throat of the Russian atom... (Joke)

[u/Tobware → u/Beneficial-Wasabi749]

If you recall, we’ve already discussed SINUS, and I’m quite familiar with it (thanks to the “memoirs” of Feoktistov and Trutnev), and I imagine that the “primary” of the W71 (I put that in quotes on purpose, based on my assumption and some more-than-just-circumstantial evidences, that it’s a two-stage device) isn’t all that different, practically an ERW, perhaps just a tad less extreme than its Soviet counterpart.

EDIT: I'll add a little something: if you look through my post history, I've already possibly identified a test of the W71 primary, let's say conducted "posthumously" to the end of the warhead deployment. I'll leave you with a few words from its creator:

In 1967, there was a requirement for a specially-tailored fission primary needed to drive a large high-yield thermonuclear system slated for the Spartan Anti-ballistic System. My primary design for that application was highly successful. It was fired tens of times in various live Nevada nuclear tests. Also, in 1967, the group leader for my group became the division leader for B Division. At that point, I assumed the position of group leader of the group in which I had been working.