In the late 1940s, as the Cold War began to heat-up, the Soviet Union began research into the development of nuclear reactors as power sources to drive warships. The work was performed at first by an academic Russian engineer, I.V. Kurchatov, which added aviation as a possible recipient of the new nuclear power plants. On August 12th, 1955 the Council of Ministers of the USSR issued a Mandate which ordered certain groups within the aviation industry to join forces in this research. As a direct result of the Mandate, the design bureaus of Andrei Tupolev and Vladimir Myasishchev became the appointed chief design teams on a project to develop and produce several aircraft designs intended to be powered by nuclear propulsion while a bureau headed by N.D. Kuznetsov and A.M. Lyulka, were assigned to develop the engines for the aircraft. They promptly decided on an energy transfer method: Direct Cycle. This method will enable the engines to use the energy supplied by the reactor, replacing the combustion chamber power supply that the jet engine utilizes. Several types of nuclear powered engines were tested: ramjet, turboprop and turbojet, with different transfer mechanisms for transmitting nuclear generated thermal energy across each one of them. After extensive experimentation with various engines and transfer systems, Soviet engineers concluded that the direct cycle turbojet engine offered the best alternative. In the direct cycle power transfer configuration, the incoming air enter through the compressor mechanism of the turbojet engine, then, passes through a plenum that direct the air to the reactor core. Then the air, by this time acting as the reactor coolant additive, is constantly heated as its move through the core. After exiting the core, the air goes back to another plenum and from there is directed to the turbine section of the engines for thrust production. New coolant systems were also tested, as it was the protective shielding for the crew cabin. This and the size of the initial nuclear power plants were the main problem facing engineers working on the project. Shielding the crew and reducing the size and weight of the reactors in order to fit one on an airframe became the main technical hurdle in the project.