I have been obsessing on this for about a week now, considering the shape of the starship Enterprise, the most filmed fiction spaceship in history.
The primary hull of the Enterprise really is a flying saucer. It is propelled by twin impulse engines at the aft. In case of extreme emergency, when the secondary hull and / or the warp engines have been destroyed, the saucer section can detach from the rest of the ship.
The design of the Enterprise is pure 1960s “space culture,” a flying saucer attached to a cylinder with two “rockets” out the rear. The fact that the Enterprise is basically just a “flying saucer” with some rockets attached is obscured by our shared cultural familiarity with the ship’s design. But if the Enterprise had been designed today, without any prior history, I doubt very much it would have looked anything like the spaceship from the ’60s.