I recently watched Destination Moon, the 1950 film about — what else? — a manned rocket flight to the moon.
Unlike most 1950s sci-fi flicks, this is a work of serious science fiction with no rubber-suited monsters. Robert Heinlein contributed to the script and served as technical advisor — which might also explain why the atomic rocket gets built by private industry and launched early, against a local demagogue’s court order.
Because many concepts of space travel were so new to the public, the film features an expository film within a film, starring a major Hollywood actor — Woody Woodpecker: