Among helicopters and airplanes, there have been other fascinating flight machines designed and constructed for experimental purposes by the US, which sometimes led to actual production.
US X-Craft
In the United States, most prototype and test aircraft contain an “X” series name/designation; though, there are some without the “X” label. Of course, pre-production models are not always suitable for flight, and are usually intended to be an idea or inspiration – such as the following “X” series designs which were purely experimental:
Convair X-6
The idea of this model was an attempt to implement nuclear power into an aircraft. The engines would be nuclear-reactive, but were never created. The X-6 was involved in a series of experimental programs (from 1946-1961) funded by the US at a cost around $7 billion. read more