-Daniel aka Obsidian
The F-35 comes in three variants, with key mechanical differences for the Air Force, Marines, and Navy - the F-35A, F-35B, and F-35C respectively. Of the three models, the F-35B is the most technologically different. Unlike the F-35A and F-35C, the Marines needed their variant to be capable of conducting short take-off and vertical landing (STOVL) operations.
This request necessitated that the F-35B be given a lifting fan. And, as Desire Francine G. Fedrigo, Ricardo Gobato, Alekssander Gobato note in a paper at the Cornell University Library, the F-35B's lifting fan has its conceptual roots in flying saucers.
Between 1954 and 1961, the US Air Force spent $10 million attempting to develop a flying saucer that became known as an Avrocar. The Avrocar was a vertical and/or short take-off and landing (V/STOL) saucer that was powered by one giant central fan.
MIT Technology Review notes that the aircraft was "hot and almost unbearably uncomfortable for the pilot. And it demonstrated various idiosyncrasies such as taking five seconds to turn 90 degrees to the left but 11 seconds to turn the same amount to the right, presumably because of its central rotating fan." However, despite the Avrocars' failings, the technology did point researchers towards the feasibility of developing and embedding a central lift fan turbine within an aircraft for variations of vertical take-off and landing (VTOL) technology.
"The concept of a lift fan, driven by a turbojet engine is not dead, and lives today as a key component of Lockheed X-35 Joint Strike Fighter contender," Fedrigo notes, adding that the conceptual framework of the Avrocar helped General Electric's own development of a booster fan propulsion system.
Whereas the Avrocar's development ultimately failed, though, GE's "Vertifan" went on to prove the concept of successful lifting fan technology. This in turn lead to a DARPA sponsored development challenge that gave birth to lifting fans being used in the F-35B. The F-35B was declared ready for combat by the Marine Corps on July 31.