A nuclear-powered aircraft is an aircraft that is powered by nuclear energy. During the Cold War, the United States and Soviet Union researched nuclear-powered bomber aircraft, the greater endurance of which could enhance nuclear deterrence, but neither country created any such operational aircraft. One inadequately solved design problem was the need for heavy shielding to protect the crew from acute radiation syndrome. The advent of ICBMs in the 1960s greatly diminished the tactical advantage of such aircraft, and respective projects were cancelled; the inherent danger of the technology has prevented its civilian use.
Some unmanned missile designs include nuclear thermal rockets.
In May 1946, the United States Army Air Forces started the Nuclear Energy for the Propulsion of Aircraft (NEPA) project, which conducted studies until the Aircraft Nuclear Propulsion (ANP) program replaced NEPA in 1951. The ANP program included provisions for studying two different types of nuclear-powered jet engines: General Electric's Direct Air Cycle and Pratt & Whitney's Indirect Air Cycle. ANP planned for Convair to modify two B-36s under the MX-1589 project. One of the B-36s, the NB-36H, was to be used for studying shielding requirements for an airborne reactor, while the other was to be the X-6; however, the program was cancelled before the X-6 was completed.