6 ms·

I read a quote somewhere (possibly via @gwern) that the only secret worth keeping about the H-bomb was that it was feasible. But I can't find it anywhere, does

I read a quote somewhere (possibly via @gwern) that the only secret worth keeping about the H-bomb was that it was feasible. But I can't find it anywhere, does someone know it?

arethuza 5y ago
I suspect the main "secret" around H-bomb design was the Teller-Ullam configuration of having a primary compress (and therefore heat) a secondary via X-rays: https://en.wikipedia.org/wiki/History_of_the_Teller%E2%80%93Ulam_design https://en.wikipedia.org/wiki/History_of_the_Teller%E2%80%93... Worth noting that this was apparently invented a number of times - first by the US, then by the Soviets, then the UK etc. Probably influenced by the fact they knew it was possible.
- pfdietz 5y ago
  The composition of fallout from US tests was also a big clue.
- cogman10 5y ago
  The hardest part about making an H-Bomb is first making a fission bomb. Once you have that, an H-Bomb is trivial by comparison. An H-Bomb is very simply just detonating a fission bomb with enough fusible material to trigger nuclear fusion. Indeed "knowing it's possible" is really all it takes.
  - justin66 5y ago
    > Once you have that, an H-Bomb is trivial by comparison. An H-Bomb is very simply just detonating a fission bomb with enough fusible material to trigger nuclear fusion. That's a completely inaccurate way of characterizing the difficulty of developing the early fusion bombs. The Russians spent years developing a hydrogen bomb they knew wasn't very good [0] because of the difficulty involved in a more sophisticated design, like the one the parent poster mentioned. The design the parent poster mentioned took also took years to develop - Teller advocated for the idea of the hydrogen bomb during the war, but had the "critical idea" in 1951. The first bomb he built in 1952 was totally impractical as a weapon. [0] https://en.wikipedia.org/wiki/Joe_4 https://en.wikipedia.org/wiki/Joe_4 (development was also discussed in one of Andrei Sakharov's memoirs)
TMWNN 5y ago
No. A gun-type atomic weapon, the type used on Hiroshima, can be built by any decent machine shop with enough enriched uranium. (It's so simple that the Manhattan Project did not bother to test it; the Trinity bomb was the more complicated implosion-type weapon used on Nagasaki.) The Teller-Ulam hydrogen bomb's theoretical underpinnings are still not public; the technique is perhaps the only known example of "born secret" technology in the US, something that the government can use prior restraint to block publication of. It is true that, as arethuza said, knowing that a Teller-Ulam device can be built certainly contributed to the Soviets, British, French, Chinese, Indians, and Pakistanis building their own hydrogen weapons. But that is not the same thing as those nations having specific knowledge of the US's pioneering method.
- lmm 5y ago
  > It is true that, as arethuza said, knowing that a Teller-Ulam device can be built certainly contributed to the Soviets, British, French, Chinese, Indians, and Pakistanis building their own hydrogen weapons. But that is not the same thing as those nations having specific knowledge of the US's pioneering method. If the end result is the same, does it matter? It doesn't seem like keeping those details secret slowed those other nations down by much.
  - TMWNN 5y ago
    >If the end result is the same, does it matter? It doesn't seem like keeping those details secret slowed those other nations down by much. For nations, no. For non nation-states, yes. As I said, Al-Qaeda, ISIS, and other groups can build an atomic weapon if they can get enriched uranium. Building a hydrogen weapon is much more difficult in terms of obtaining components and knowing what to do with them. The builders need some level of theoretical understanding of how the weapon works.
  - simonh 5y ago
    Looking back over 75+ years of atomic weapons research slowing them down by a few years or even a decade might not seem like much, but at the time such delays could have been very significant.
tyingq 5y ago
All the secret keeping seems to be about enriching fuel in a relatively affordable way. Was that not secret worthy, ever?
phreeza 5y ago
Gwern pointed me to the quote on his website: https://www.gwern.net/on-really-trying https://www.gwern.net/on-really-trying The quote is: "the one secret concerning the atomic bomb which might have been kept and which was given to the public and to all potential enemies without the least inhibition, was that of the possibility on its construction". As others had suspected, it's about the atomic bomb, not the H-bomb, which in retrospect makes more sense of course.

I read a quote somewhere (possibly via @gwern) that the only secret worth keeping about the H-bomb was that it was feasible. But I can't find it anywhere, does someone know it?

arethuza 5y ago

I suspect the main "secret" around H-bomb design was the Teller-Ullam configuration of having a primary compress (and therefore heat) a secondary via X-rays: https://en.wikipedia.org/wiki/History_of_the_Teller%E2%80%93Ulam_design https://en.wikipedia.org/wiki/History_of_the_Teller%E2%80%93... Worth noting that this was apparently invented a number of times - first by the US, then by the Soviets, then the UK etc. Probably influenced by the fact they knew it was possible.

pfdietz 5y ago
The composition of fallout from US tests was also a big clue.
cogman10 5y ago
The hardest part about making an H-Bomb is first making a fission bomb. Once you have that, an H-Bomb is trivial by comparison. An H-Bomb is very simply just detonating a fission bomb with enough fusible material to trigger nuclear fusion. Indeed "knowing it's possible" is really all it takes.
- justin66 5y ago
  > Once you have that, an H-Bomb is trivial by comparison. An H-Bomb is very simply just detonating a fission bomb with enough fusible material to trigger nuclear fusion. That's a completely inaccurate way of characterizing the difficulty of developing the early fusion bombs. The Russians spent years developing a hydrogen bomb they knew wasn't very good [0] because of the difficulty involved in a more sophisticated design, like the one the parent poster mentioned. The design the parent poster mentioned took also took years to develop - Teller advocated for the idea of the hydrogen bomb during the war, but had the "critical idea" in 1951. The first bomb he built in 1952 was totally impractical as a weapon. [0] https://en.wikipedia.org/wiki/Joe_4 https://en.wikipedia.org/wiki/Joe_4 (development was also discussed in one of Andrei Sakharov's memoirs)

TMWNN 5y ago

No. A gun-type atomic weapon, the type used on Hiroshima, can be built by any decent machine shop with enough enriched uranium. (It's so simple that the Manhattan Project did not bother to test it; the Trinity bomb was the more complicated implosion-type weapon used on Nagasaki.) The Teller-Ulam hydrogen bomb's theoretical underpinnings are still not public; the technique is perhaps the only known example of "born secret" technology in the US, something that the government can use prior restraint to block publication of. It is true that, as arethuza said, knowing that a Teller-Ulam device can be built certainly contributed to the Soviets, British, French, Chinese, Indians, and Pakistanis building their own hydrogen weapons. But that is not the same thing as those nations having specific knowledge of the US's pioneering method.

lmm 5y ago
> It is true that, as arethuza said, knowing that a Teller-Ulam device can be built certainly contributed to the Soviets, British, French, Chinese, Indians, and Pakistanis building their own hydrogen weapons. But that is not the same thing as those nations having specific knowledge of the US's pioneering method. If the end result is the same, does it matter? It doesn't seem like keeping those details secret slowed those other nations down by much.
- TMWNN 5y ago
  >If the end result is the same, does it matter? It doesn't seem like keeping those details secret slowed those other nations down by much. For nations, no. For non nation-states, yes. As I said, Al-Qaeda, ISIS, and other groups can build an atomic weapon if they can get enriched uranium. Building a hydrogen weapon is much more difficult in terms of obtaining components and knowing what to do with them. The builders need some level of theoretical understanding of how the weapon works.
- simonh 5y ago
  Looking back over 75+ years of atomic weapons research slowing them down by a few years or even a decade might not seem like much, but at the time such delays could have been very significant.

tyingq 5y ago

All the secret keeping seems to be about enriching fuel in a relatively affordable way. Was that not secret worthy, ever?

phreeza 5y ago

Gwern pointed me to the quote on his website: https://www.gwern.net/on-really-trying https://www.gwern.net/on-really-trying The quote is: "the one secret concerning the atomic bomb which might have been kept and which was given to the public and to all potential enemies without the least inhibition, was that of the possibility on its construction". As others had suspected, it's about the atomic bomb, not the H-bomb, which in retrospect makes more sense of course.