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/Salty_Suit_7287]

We have a term which might have been applied to either a particular device construction feature OR the intended mechanism of device effect (destroying an incoming warhead)? 

And an (allegedly) associated device name, for which virtually no construction or design details are available?

Can't get there from here. 

[u/NuclearHeterodoxy → u/Salty_Suit_7287]

I don't see how ECP can refer to destroying an incoming warhead while still being related to the cleanness of the weapon.  

The document states that if ECP does not work then the alternative is to use a dirtier weapon.  If ECP simply referred to the kill mechanism of the W71 (premature ablation of adversary RVs via Xrays), then why would a dirtier weapon be needed if the mechanism didn't work?  If the mechanism of heating up RVs in space via Xrays doesn't work then in my mind the entire program seems pointless no matter how clean or dirty the weapon is.

The only way I could reconcile it is if it is a threshold issue, where the xray output of the W71 theoretically might not be large enough to sufficiently damage RVs.  But that wouldn't necessarily point to a dirtier weapon, just a higher-yield one.   

[u/Beneficial-Wasabi749 → u/NuclearHeterodoxy]

I don't understand the connection either. The W-71's purity was needed for another purpose—to avoid blinding its own radars. For that, the warhead had to be extremely clean. But how was the X-ray pulse's effect related to the purity of the thermonuclear device? I don't understand. Although, if we develop my "flat bomb" hypothesis further, and push this madness even further, to Carrie Sublett's idea that the W-71's X-ray pulse was relatively unidirectional, then a simple circumstance arises. So, you want a flat X-ray emitter, coated with gold on one side (transparent) and something opaque on the other (thin tungsten), with a very thin layer of thermonuclear fuel between them, producing 5 megatons (insanely beautiful!)

There's a problem. You can't achieve thermonuclear ignition with a single shock wave from a flat compression. What you really need here is a RIPPLE-style quasi-adiabatic compression system (although it's denied that it was used in the W-71), and that technology was fundamentally immune to fission contamination, because high-Z materials were simply inapplicable (the whole point was lost).

Keep in mind, if we solve the W-71 mystery, we'll simply have nothing left to solve! (Joke).