It sounds like a title of a pulp-era sf story, but propellers are actual features in Saturn’s Rings that look like … well, propellers.
These things are way cool. Imagine a moonlet about the size of a sports arena or a cathedral. It has just enough gravity to attract some dust in front and behind it as it orbits Saturn, but it’s not massive enough to clear out a whole gap like the moon Daphnis:
This news release from CU-Boulder describes a whole belt of moonlets. Imagine what sf writers of the 30’s and 40’s might have thought of them.