Field of Science

The H-Bomb Fuchs?

And a very brief history of the US hydrogen bomb effort

How the Soviets got the H-bomb by 1955 has always been something of a mystery. Although they had top-notch scientists like Andrei Sakharov working for them, they still got almost exactly the same design as the Americans in just 4 years. Nobody denies Sakharov's tremendous contributions to the H-bomb effort. And yet the question lingers whether espionage helped H-bomb design just as it had helped Soviet A-bomb design, most famously through Klaus Fuchs's efforts.

Now a new book due to be released in January claims that the authors have uncovered a spy who gave details about the H-bomb design to the Soviets. 'The Nuclear Express' is co-authored by Thomas Reed, a former weapons designer who worked at Los Alamos for many years. The authors would not name the spy since he is now purportedly dead. Historians who have weighed in don't find the idea entirely implausible; after all it is hard to believe that security would have been so tight so as to completely preclude espionage. In addition even after Fuchs was apprehended, the Soviets still had a web of spies and sympathizers spread throughout the US that even as of now is not completely deciphered.

It is worthwhile at this point to recapitulate some of the US H-bomb history:

1942: Edward Teller, the 'father of the hydrogen bomb', builds upon a suggestion by Enrico Fermi and proposes the first design for a thermonuclear weapon. This is during a secret conference at Berkeley organized by Robert Oppenheimer that's supposed to explore the feasibility of a fission weapon, not a fusion device. Teller's basic idea is to use the extreme temperatures arising from an atomic bomb to ignite a cylinder of deuterium or tritium at one end, with the unproven assumption that the fusion fuel will ignite and continue to burn, thus producing a tremendous explosion equivalent to millions of tons of TNT. The H-bomb distracts the participants enough for them to speculate on its workings, but atomic bomb design (necessary for initiating a fusion reaction anyway) is wisely given priority. The as yet speculative thermonuclear weapon is christened "The Super". The Manhattan Project is kicked off. Throughout the war Teller goes off on his own H-bomb trajectory, often contributing to flared tempers and inadequate expertise at Los Alamos.

1946: After the war, Teller who is still obsessed with the weapon convenes a short, top secret conference. Klaus Fuchs is one of the participants. The conference concludes, mostly based on Teller's optimistic assessment, that The Super is feasible. At the end of the conference, Teller submits an overly optimistic report much to the chagrin of Robert Serber, an accomplished physicist who had been Oppenheimer's principal assistant at Los Alamos. Fuchs transmits the information from this conference to the Soviets.

August 1949: The Soviets detonate their first atomic bomb. Everyone is shocked, perhaps unnecessarily so. A high-level committee headed by Oppenheimer convenes in October on Halloween and debates H-bomb development. The almost unanimous opinion is that the H-bomb is not a tactical weapon of war but a weapon of genocide and therefore its development should not be undertaken. Priority should be given instead to the development of better, tactical fission weapons.

December 1949-January 1950: Edward Teller, spurred on by the Soviet A-bomb, starts recruiting scientists to join him at Los Alamos to work on the Super. Hans Bethe initially agrees, then after a chat with Oppenheimer and Victor Weiskopf, declines. Teller blames his change of mind on Oppenheimer. Later Bethe decides to work at Los Alamos only as a consultant, mainly because he wants to prove that The Super won't be feasible.

During this time, Stanislaw Ulam and Cornelius Everett at Los Alamos embark on a set of tedious calculations to investigate the feasibility of The Super. The result is decidedly pessimistic. The Super would need much more tritium, an extremely rare and expensive isotope, to initiate burning. Even if tritium is added the probability of successful propagation is extremely low. Teller's dream is dead in the water. Fermi, one of Teller's role models, confirms the bad news.

January-February 1950: Even as Ulam's calculations give a fit to Teller, Klaus Fuchs confesses his espionage. The country gradually starts descending into a state of paranoia. Against the advice of many experts, President Harry Truman initiates a crash program to build the H-bomb. Incidentally his announcement comes before that about Fuchs. And it comes absurdly even as Ulam and others have proven that Teller's Super would not work.

1950: Throughout 1950 the options for the Super keep on looking bleaker. In June the Korean War begins, fueling more feeling of paranoia. Teller's mood blackens. At one point after Ulam reports his latest set of calculations, Teller is said to be "pale with fury"

December 1950-January 1951: Ulam makes a breakthrough. He realizes that separating the fission weapon and fusion fuel and using the extreme pressures generated by the fission weapon will cause compression of the fusion fuel, thus dramatically increasing the odds of thermonuclear burning. Ulam floats the idea to Teller who enthusiastically espouses it and also crucially realizes that radiation from the fission "primary" would do an efficient job of compressing and sparking off fusion in the fusion "secondary". The idea is so elegant that Oppenheimer calls it 'technically sweet' and now supports the program. Bethe agrees to work on the device because suddenly everyone thinks that the Soviets will now not be long in discovering it. Later, Teller makes significant efforts to discredit Ulam's role in the invention. But the Teller-Ulam design becomes the basis for almost every hydrogen bomb in the arsenals of the world's nuclear powers.

1951-1952: Work proceeds on a thermonuclear weapon. In November 1952 the world's first hydrogen bomb, Ivy Mike, explodes with a force equivalent to 650 Hiroshima type bombs. Mankind has finally invented a device that comes closest to being a weapon for complete annihilation of nations.

So that is where matters stood in 1952. That gives the spy a window of two years or so to transmit the information. It's instructive to note that after Fuchs was outed, Oppenheimer actually hoped that he had told the Soviets about the H-bomb design from the 1946 conference, since that design had been shown to fail and would have led the Soviets on a wild goose chase. However the initial thoughts that Bethe, Oppenheimer and others had about the Soviets discovering the Teller-Ulam mechanism soon don't look unfounded to me. There were experts who thought that the idea of using compression and radiation to ignite and burn the thermonuclear fuel would occur to anyone who had thought hard and long about these matters. Niels Bohr thought that a bright high-school student would have thought about it, but that's probably going a little too far. The truth could well be in between, with both original thought and espionage playing a role. In any case the new book promises fresh fodder for atomic aficionados and I have pre-ordered it.


  1. This is the weirdest coincidence. I just bought "Dark Sun" on Saturday and I was reading about Racey Jordan's accusations against the Soviets just a few minutes ago. God, it's such a good scientific story.

  2. That's a great book. The other great book is Stalin and the Bomb by David Holloway.

  3. Actually, first Russin H-bomb was of different and less efficient design:
    If Saharov and Zel'dovich had the blue-prints of american bomb they would certainly use the more efficient design which would be known to work...

  4. Thanks for reminding me Ashutosh! I have forty bucks I've been meaning to blow on something and almost forgot that I've been planning on getting to get the Rhodes books. Or... I could start saving for Dragon*Con. Crap. Damn these decisions!

  5. Go for the Rhodes books! The two combined constitute probably the best chronicle of the A and H bombs.

    Anon: True, the first design was the layer cake design from 1953. The second one was in 1955 in which I believed they used Lithium 6. That too was supposed to be a top secret. Even if S and Z had the info in 1953 they might have wanted to first test their own design.


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