known, partly because of numerous conflicting personal accounts and also by the continued classification of documents that would reveal which was closer to the truth. Previous models of the "Super" had apparently placed the fusion fuel either surrounding the fission "trigger" (in a spherical formation) or at the heart of it (similar to a "boosted" weapon) in the hopes that the closer the fuel was to the fission explosion, the higher the chance it would ignite the fusion fuel by the sheer force of the heat generated. In 1951, after still many years of fruitless labor on the "Super", a breakthrough idea from the Polish émigré mathematician Stanislaw Ulam was seized upon by Teller and developed into the first workable design for a megaton-range hydrogen bomb. This concept, now called "staged implosion" was first proposed in a classified scientific paper, On Heterocatalytic Detonations I. Hydrodynamic Lenses and Radiation Mirrors by Teller and Ulam on March 9, 1951. The exact amount of contribution provided respectively from Ulam and Teller to what became known as the "Teller–Ulam design" is not definitively known in the public domain—the degree of credit assigned to Teller by his contemporaries is almost exactly commensurate with how well they thought of Teller in general. In an interview with Scientific American from 1999, Teller told the reporter: I contributed; Ulam did not. I'm sorry I had to answer it in this abrupt way. Ulam was rightly dissatisfied with an old approach. He came to me with a part of an idea which I already had worked out and difficulty getting people to listen to. He was willing to sign a paper. When it then came to defending that paper and really putting work into it, he refused. He said, "I don't believe in it." The issue is controversial. Bethe in his “Memorandum on the History of the Thermonuclear Program” (1952) cited Teller as the discoverer of an “entirely new approach to thermonuclear reactions”, which “was a matter of inspiration” and was “therefore, unpredictable” and “largely accidental.” At the Oppenheimer hearing, in 1954, Bethe spoke of Teller's “stroke of genius” in the invention of the H-bomb. And finally in 1997 Bethe stated that “the crucial invention was made in 1951, by Teller.” Other scientists (antagonistic to Teller, such as J. Carson Mark) have claimed that Teller would have never gotten any closer without the idea of Ulam. The nuclear weapons