English: Title page of classified scientific paper by US nuclear physicists Edward Teller and Stanislaw M. Ulam March 9, 1951 On Heterocatalytic Detonations I: Hydrodynamic Lenses and Radiation Mirrors, at US nuclear weapon design facility Los Alamos Scientific Laboratory, Los Alamos, New Mexico, which contains their historic breakthrough idea for how to build a practical thermonuclear weapon, staged implosion, generally referred to as the "secret of the hydrogen bomb". This concept, which may have been independently invented by scientists in other countries, is thought to be the design used in all modern thermonuclear weapons, which includes virtually all nuclear weapons in the arsenals of major "nuclear" nations. This declassified version is heavily redacted; out of 20 pages only a few paragraphs are not blacked out. Only pages with text remaining have been uploaded here.

However the remaining content does reveal a few facts. The 3 unredacted paragraphs on page 3 state the basics of the idea; that by the explosion of one or more "auxiliary" fission bombs they hoped to ignite a reaction in a "principal" assembly of either fission or fusion fuel outside the bombs. The jargon they used for this revolutionary idea was the term "heterocatalytic", appearing in the title. This is in contrast to the "autocatalytic" action of a fission bomb, which ignites fuel inside itself.