A century ago engineer Luigi Stipa did experiments with several flying wing aircraft designs. Here is Stipa-Caproni's "intubed propeller" from the 1930s: https

A century ago engineer Luigi Stipa did experiments with several flying wing aircraft designs. Here is Stipa-Caproni's "intubed propeller" from the 1930s: https://en.wikipedia.org/wiki/Stipa-Caproni https://en.wikipedia.org/wiki/Stipa-Caproni Even newer patents should cite this research: https://en.wikipedia.org/wiki/Luigi_Stipa https://en.wikipedia.org/wiki/Luigi_Stipa