From Larry Niven's novel Ringworld.
Almost only used for intestellar travel, this statoreactor device allows for a "permanent" refueling of the engine: an electromagnetic field supplied by autorecharging batteries and built around the prow captures interstellar hydrogen atoms and carries them back to the huge front overture, mouth of the main reactor; this field compresses the hydrogen particules until they reach fusion point –this power source allows propulsion. See a cargo variation here: [link]
And a generation ship version there: [link]
Made with pencil & marker in 1996