This is it: The first of a series of issues of Collier’s magazine that sparked a public interest in space. Not science fiction, the article “Man Will Conquer Space Soon” was written by Wernher von Braun, with realistic illustrations by Chesley Bonestell. Von Braun gave precise details for his vision of a wheel-shaped space station, an image that became embedded in the public mind. The article begins, “Scientists and engineers now know how to build build a station in space that would circle the earth 1,075 miles up. The job would take ten years and cost twice as much as the atom bomb.” Later issues detailed trips to the moon and Mars.
At the time, Collier’s had a readership of four million. You could make a case that The Space Age, at least in the public mind, began 70 years ago with this issue.