The United States SPACE FANTASY issue of 1993 (Scott 2741-2745) is a wonderful springboard for the imagination, its imagery drawn from the Golden Age of pulp science fiction of the 1930s through '50s. The bubble-helmeted space adventurers depicted on this booklet pane wearing riding boots and johdpurs as they jetpack through space may seem quaint, even naive images to us now, but were visionary projections of the future to contemporary sci-fi readers. The "Pulps" provided the launch pads for the careers of modern science fiction masters-- Robert Heinlein, Isaac Asimov, Poul Anderson, among many others.
Accompanying the story is a 1965 stamp from Romania, showing the USA Gemini 3 spacecraft ( nicknamed "Molly Brown"), an issue from Togo showing Apollo 11 landing on the moon in 1969, and pulp science fiction covers from the Golden Age. (The covers are not in the original published story.)
Many countries of the world have issued postage stamps celebrating space exploration. One of my favorites is the dramatic image to the right from the African republic of Chad, a 1972 airmail issue showing the Russian Luna XVI lunar probe.