Toroidal designs use joined, loop-like blades so thrust develops through and around the blade structure rather than across a conventional flat blade alone. The concept dates to Frederick H. Hungerford's work in the 1930s, but modern materials and manufacturing are only now making practical experimentation easier. Their apparent efficiency is promising, although present understanding of their underwater noise may limit near-term warship use. The contrast with quiet operation in air on drones shows why performance in one fluid and mission cannot simply be transferred to another.
Notable Point · 28:10-30:03
Toroidal propellers revisit an old idea with new manufacturing
Looped blades promise high efficiency, but their underwater noise and still-developing fluid dynamics leave their warship value uncertain.