of the implosion was dictated by the initial spherically symmetric detonation of the explosive". There seemed to be no way in which "a heterogeneous structure composed of a primary source (or sources) and a compressible secondary module" could "maintain the spherically symmetric 'nuclear implosion". The following is a report by Sakharov and Romanov on 6 August, with the title "Atomic Compression". "Atomic Compression is being investigated theoretically in collaboration with members of sector No. 2. The main problems associated with atomic compression are in the development stage. (1) Emission of radiation from the atomic bomb used to compress main body. Calculations show that for [deleted] radiation is emitted very strongly... (2) Conversion of radiant energy into mechanical energy to compress the main body. It is postulated [deleted]. These principles have been developed through the team efforts of Sectors No. 2 and No. 1 (Ya. B. Zel’dovich, Yu. A. Trutnev, and A. D. Sakharov)...". This problem with a two-stage nuclear charge brings about two other problems. One, "what is now the carrier of the explosive energy of the original source?". Two, "how is this energy transported to the secondary module?". The second set of questions concerns the secondary module impacted by the nuclear implosion of the fission trigger. At first, scientist thought that the energy of a nuclear initiation of the fission trigger in a two-stage charge would be transported by the flow of the products of the initiation as the shock wave spread through the heterogeneous structure of the secondary module. Zeldovich and Sakharov "decided to choose an analog of the inner element of the RDS-6s charge for the basic physical element of the secondary module, i.e. the 'layered' spherical configuration of the system". Factors behind the design The Soviet Union was able to form some similar achievements to the United States without the help of outside information. "The active material, instead of being a solid sphere to begin with, as in the Nagasaki bomb, would be fabricated as a shell, with a 'levitated' sphere in its center. Part of the expensive plutonium was replaced with less expensive uranium-235. Levitation increased the energy yield and made it possible to reduce the size and weight of the explosive. Similar achievements were achieved without espionage by the Soviet Laboratories." The initial alarm-clock method derived by Teller was assessed by Stanislaw Ulam, who decided that it would be more difficult and costlier than