U.S. Military's Nuclear-Powered Bomber Project, 'Aircraft Nuclear Propulsion,' Abandoned Due to Strategic Shifts and Costs
The United States Army Air Forces initiated Project NEPA in 1946, later renamed Aircraft Nuclear Propulsion (ANP) in 1951, with the ambitious goal of developing a nuclear-powered bomber capable of indefinite flight without refueling. The core concept involved replacing the combustion chamber of a turbojet engine with a nuclear reactor. General Electric was tasked with developing a 'direct cycle' system, leading to the creation of test assemblies like HTRE-1, HTRE-2, and HTRE-3. To demonstrate the feasibility of carrying and operating such a reactor in flight, a B-36 Peacemaker bomber, damaged by a tornado, was modified into the NB-36H. This aircraft conducted 47 test flights over Texas and New Mexico between July 1955 and March 1957, carrying a functional three-megawatt air-cooled reactor. While the reactor never propelled the aircraft, these flights aimed to assess operational challenges. The program, spanning 15 years, incurred costs of approximately one billion dollars. 
