Way back in 1955 a then secret project set out to build an aircraft which could fly indefinitely, never needing power. How so you ask? By using a nuclear reactor powered jet engine. In fact the aircraft concept was called the NB-36 and it was built with a 10,000 lb lead bulkhead to shield the pilots from radiation. Originally the aircraft would have spewed radiation out the back and then some brilliant scientists came up with a heat conversion process using liquid metal which allowed the nuclear reactor to remain in a closed loop system heating the liquid metal which was used to spin a turbine jet engine.
The new design was contracted with GE to build the engine although they did not know what the engine was to be used for. It was to be what would be called the Convair B-36 WS125, (weapons system 125), a project which would eventually be cancelled. Perfect for the cold war, never needing fuel with unlimited range. Something we will need for our future exploratory spacecraft, which may be used for generations and cannot simply stop to re-fuel you see?
The USSR was said to have build during this past period the Soviet Bounder supposedly