Q: Early in 1951 Stanislaw Ulam comes up with a new idea for a superbomb
design. What do you know about that?|
RR: At that particular time, after Ulam finished these calculations on the
Super, he really was interested in making better atomic bombs, fission bombs.
And he started thinking about how you could do that. The thing that limited
the yield on the classic implosion type bomb (the spherical bomb with the
explosive squeezing the plutonium or uranium core until it was a critical mass,
and then you had a nuclear explosion), the thing that limited the yield was
that you couldn't get a lot of compression with high explosives. It occurred
to him that maybe you could use the blast from one atomic bomb to squeeze a
second atomic core, and thereby get the much more enormous compression that you
would get from this much more enormous explosion. So he called it an iterative
scheme, meaning something that repeats. And in fact, he envisioned the
possibility of one atomic bomb setting off a second core, which in turn set off
a third core. Theoretically, you could chain these together and have a larger
and larger yield. That was the basic idea that he had. And he played with
that for quite some time.
But at some point (it seems to have been around the beginning of 1951,
January) it occurred to Ulam that the same iterative scheme of using the blast
from an atomic bomb to set off a second bomb, might be the answer for the
hydrogen bomb. If that second piece were hydrogen fuel, then you might be able
to heat it and compress it sufficiently to start a fusion reaction going...
So he went to see Teller. Before he talked to Teller, though, he talked to
Carson Mark. He seems to have talked to Norris Bradbury (Oppenheimer's
successor as director of the laboratory). Then he took the idea to Teller.
Teller was immediately hostile. He didn't think it was a good idea. But as
they talked about it and looked at the numbers, within about (he--Ulam says)
about 30 minutes, Teller got more and more enthusiastic.
But Teller then was able to connect this idea presumably with the George shot,
with the idea of using not the blast from an atomic bomb, which travels
relatively slowly because it's matter (neutrons mostly), but the
radiation from the bomb. X-rays from an exploding atomic bomb travel 10
feet in the time it takes the neutrons to travel 4 inches. So as Carson Mark
told me later, he couldn't have avoided the radiation. It was there. You had
to deal with it. And in the more sophisticated and efficient bombs that by
then we had in our arsenal, there was a lot more radiation than had been true
of the first bombs. So there it was. Teller saw that the radiation could be
used, and that that would solve the whole problem of the whole thing blowing
itself apart before you could get much reaction going. And that truly was the
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