American physicist Kip S.
American physicist Kip S. Thorne (1940-) never participated in nuclear weapons projects, unlike his teacher Wheeler, Zel'dovich and Stirling.

In his book "Black Holes and Time Warps" (p.241-243)
http://books.google.com/books?id=GzlrW6kytdoC&pg=PA241
he tells a fascinating story:
[...]
        The adaptation of bomb design codes to simulate stellar implosion is juts one of many intimate connections between nuclear weapons and astrophysics. These connections were obvious to Sakharov in 1948. Upon being ordered to join Tamm's bomb design team, he embarked on a study of astrophysics to prepare himself. My own nose was rubbed into the connection unexpectedly in 1969.
        I never really wanted to know what the Teller-Ulam/Sakharov-Zel'dovich idea was. [...] I didn't want even to speculate about how it worked.
        Zel'dovich, several years earlier, had pointed out that gas from interstellar space or a nearby star, falling onto a neutron star, should heat up and shine brightly. It should become so hot, in fact, that it radiates mostly high-energy X-rays rather than less energetic light.  The infalling gas controls the rate of outflow of X-rays, Zel'dovich argued, and conversely, the outflowing X-rays control the rate of infall of gas. Thereby, the two, gas and X-rays, working together, produce a steady, self-regulated flow.  If the gas falls in at too high a rate, then it will produce lots of X-rays, and the outpouring X-rays will strike the infalling gas, producing an outward pressure that slows the gas's fall (Figure 6.4a). On the other hand, if the gas falls in at too low a rate, then it produces so few X-rays that they are powerless to slow the infalling gas, so the infall rate increases. There is just one unique rate of gas infall, not too high and not too low, at which the X-rays and gas are in mutual equilibrium.
        This picture of the flow of gas and X rays disturbed me. I knew full well that on Earth, if one tries to hold a dense fluid such as liquid mercury up be means of a less dense fluid such as water below it, tongues of mercury quickly eat their way down into the water, the mercury goes whooshing down, and the water goes whooshing up (Figure 6.4a). This phenomenon is called Rayleigh-Taylor instability. In Zeldovich's picture, the X rays were like the low density water and the gas was like high density mercury. Wouldn't tongues of gas 
eat their way into the X rays, and wouldn't the gas then fall freely down 
those tongues, destroying Zel'dovich's self-regulating flow (Figure 6.4c)? A detailed calculation with the laws of physics would tell me whether this happened, but such a calculation would be very complex and 
time consuming; so, rather than calculate, I asked Zeldovich one afternoon in 1969, when we were discussing physics in his apartment in Moscow.
        Zeldovich looked a bit uncomfortable when I rased the question, but his answer was firm: "No Kip, that doesn't happen. There are no tongues into the X rays. The flow of gas is stable." "How do you know, Yakov Borisovich?" I asked. Amazingly, I could not get an answer. It seemed clear that Zeldovich or somebody had done a detailed calculation or experiment showing that X rays can push hard on a gas without Rayleigh- Taylor tongues destroying the push, but Zel'dovich could not point me to any such calculation or experiment in the published literature, nor would he describe for me the detailed physics that goes on. How uncharacteristic of him!
        A few months later I was hiking in the high Sierras in California with 
Stirling Colgate. (Colgate is one of the best American experts on the flows of fluids and radiation and was deeply involved in the late stages of the American superbomb effort, and he was one of the three Livermore physicists who had simulated a star's implosion on a computer). As we hiked I posed to Colgate the same question I had asked of Zeldovich, and he gave me the same answer: The flow is stable; the gas cannot escape the force of the X rays by developing tongues. "How do you know, Stirling?" I asked. "It has been shown", he replied. "Where can I find the calculations or experiments?" I asked. "I don't know...
        "That's very peculiar," I told Stirling. "Zel'dovich told me precisely the same thing - the flow is stable. But he, like you, would not point to any proofs." "Oh! That's fascinating. So Zeldovich really knew," said Stirling."
        And then I knew as well. I hadn't wanted to know. But the conclusion was unavoidable. The Teller-Ulam idea must be the use of X rays emitted in the first microsecond of the fission (atom bomb) trigger to heat, help compress, and ignite the superbomb's fusion fuel (Figure 6.5). That this is, indeed, part of the Teller-Ulam idea was confirmed in the 1980's in several unclassified American publications, otherwise I wouldn't mention it here."

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I did not find what those are.
http://books.google.com/books?id=GzlrW6kytdoC&pg=PA241

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