using it to initiate the fusion part of the bomb. This idea parallels the Teller–Ulam design used in the Mike detonation. They subsequently abandoned the single-stage layer-cake and tube designs, and focused entirely on the two-stage bomb project. A report on the activity of the theoretical sector No. 1 published in 1954 states: Atomic compression is being investigated theoretically in collaboration with members of sector No. 2. The main problems associated with atomic compression are in the developmental stage. Emission of radiation from the atomic bomb used to compress the main body. Calculations show that for radiation is emitted very strongly. Conversion of radiant energy into mechanical energy to compress the main body. These principles have been developed through the efforts of Sectors No. 2. and No. 1. On 22 November 1955, the Russians tested their first true two-stage hydrogen bomb in the megaton range, the RDS-37. This test implemented the two-stage radiation implosion. This was also the world's first air-dropped fusion-bomb test. Foundations of RDS-37 After the Bravo Test in March 1954, Soviet scientists started to search for ways to make an effective large-yield thermonuclear bomb. After a lot of intensive research of past experience with these bombs, a new two-stage bomb was devised. The RDS-37's thermonuclear charges are founded in fundamental scientific concepts of high-energy-density physics. The principle of radiation implosion assumes three concepts. According to Ilkaev, they are: "the predominant proportion of the energy of the explosion of the nuclear charge (the primary module) is generated in the form of X-ray radiation; the energy of the X-ray radiation is transported to the fusion module; the implosion of the fusion module using the energy of the 'delivered' X-ray radiation". Hopes for a better compression of nuclear material that could be initiated had been in discussion since the early 1950s. Not long after, Yakov Borisovich Zel'dovich and Andrei Sakharov started to work on this theory. "In January 1954, Ya. B. Zeldovich and A. D. Sakharov considered in detail a device layout which incorporated the principle of a two-stage nuclear charge". Many people questioned whether they could be successful from the very beginning. Questions concerning the two-stage nuclear charge fell into two categories. The first set of questions concerned nuclear implosion. The first module, or fission trigger, initiated "by compression of nuclear material or fission and fusion of materials by spherical explosion of chemical explosives, in which the spherical symmetry