When their latest rocket test fails and government funding collapses, rocket scientist Dr. Charles Cargraves (Warner Anderson) and space enthusiast General Thayer (Tom Powers) enlist the aid of aircraft magnate Jim Barnes (John Archer). With the necessary millions raised privately from a group of patriotic U. S. industrialists, Cargraves, Warner, and Barnes build an advanced single-stage-to-orbit atomic powered spaceship, named Luna, at their desert manufacturing and launch facility; the project is soon threatened by a ginned-up public uproar over "radiation safety". The three idealists circumvent legal efforts to stop their expedition by simply launching the world's first Moon mission well ahead of schedule; as a result, they must quickly substitute Joe Sweeney (Dick Wesson) as their expedition's radar and radio operator.
In the British city of "Everytown", businessman John Cabal (Raymond Massey) cannot enjoy Christmas Day, 1940, with the news everywhere of possible war. His guest, Harding (Maurice Braddell), shares his worries, while his other friend, the over-optimistic Pippa Passworthy (Edward Chapman), believes it will not come to pass, but if it does, it will accelerate technological progress. An aerial bombing raid on the city that night results in general mobilisation and then global war.
In the year 1946, the Soviet space program is undergoing turmoil. Professor Sedikh, who is planning to lead the first manned exploration to the moon, is denounced by his rival Professor Karin as being too old and too mentally unstable for the mission. Professor Sedikh, aided by his assistant Marina and a youth named Andryusha, disregard Prof. Karin’s authority and make a successful landing on the moon. Although a few problems occur at the moon, including the discovery of a damaged oxygen tank and Professor Sedikh’s becoming trapped under a fallen boulder, the expedition is a success and the cosmonauts return to Moscow.
The film is a melodrama with scientific speculation. Helius (Willy Fritsch) is an entrepreneur with an interest in space travel. He seeks out Professor Mannfeldt (Klaus Pohl), a visionary who has written a treatise on the likelihood of finding gold on the moon, only to be ridiculed by his peers. Helius recognizes the value of Mannfeldt's work, but a gang of evil businessmen have also taken an interest in Mannfeldt's theories.
At a meeting of the Astronomic Club, its president, Professor Barbenfouillis, proposes a trip to the Moon. After addressing some dissent, five other brave astronomers—Nostradamus, Alcofrisbas, Omega, Micromegas, and Parafaragaramus—agree to the plan. They build a space capsule in the shape of a bullet, and a huge cannon to shoot it into space. The astronomers embark and their capsule is fired from the cannon with the help of "marines", most of whom are played by a bevy of young women in sailors' outfits. The Man in the Moon watches the capsule as it approaches, and it hits him in the eye.
In the observatory, the astronomer is studying at his desk. Satan appears, then a woman appears and makes Satan vanish. Then she disappears. The astronomer draws a globe on a blackboard. The globe develops a sun-like head and limbs and starts to move on the blackboard. The astronomer looks through a small telescope.