I regularly follow Centauri Dreams, a great blog on the future of interstellar travel, and one of the more compelling technologies makes a recurring appearance – Bussard Ramjets. Think of these as jet engines that take in hydrogen with enormous electromagnetic collectors, feeding a fusion engine. They can’t break the speed of light, but they’re fast enough to being humans to the stars. Eventually.
These ships are enormous. From a distance you would mostly see the side effects of this exotic drive – glowing fields and hot plasma. In my mind these starships would resemble cathedrals set against a tapestry of stars.