After the events of Destination Moon
Tintin, Haddock, Snowy, Professor Calculus and his assistant Frank Wolff are currently en route to the Moon in Calculus' rocket. Shortly into the trip however, a serious predicament arises: Thomson and Thompson are found inside the rocket, having decided to "guard it" having thought the time of the launch was at 1:34 AM instead of 1:34 PM — the oxygen supply was designed for four people (plus Snowy), not six.
From that point on, the trip is still plagued with difficulties: the Thompsons accidentally turn off the nuclear motor, leading to microgravity hijinks; Haddock gets drunk on some smuggled whiskey, goes on an impromptu space walk and starts orbiting around an asteroid, forcing Tintin to rescue him and the Thompsons are still suffering occasional relapses of the bizarre condition caused by their ingestion of Formula Fourteen
. Despite all this, the rocket successfully lands on the Hipparchus Crater and Tintin becomes the first man to walk on the moon.
They quickly proceed to unpack their scientific payload and explore Earth's natural satellite. Unfortunately the trip has to be cut short not only because of the oxygen issue but due to a far graver development: the spy subplot of the previous book comes to a head when Colonel Jorgen
is revealed to have stowed away on the rocket with a gun, and Wolff is revealed as his accomplice and the foreign power's mole
in the center. Wolff, who was informed that Jorgen was simply there to observe the expedition is horrified when he finds out Jorgen's plan is to steal the rocket for his employers and maroon everyone else on the Moon. Wolff is forced to launch the rocket at gunpoint but Tintin manages to sabotage it and foil the plot. After interrogating the two, they are locked in the hold but Tintin's move had a grave price: the rocket will have to be repaired while the oxygen supply quickly dwindles.
After leaving the Moon in haste and an incorrect trajectory which causes them to waste even more time and oxygen, Jorgen manages to break free and regain his gun, intending to kill the rest of the crew. He and Wolff struggle causing Jorgen to shoot himself in the heart, killing him instantly. Eventually, Wolff decides to sacrifice himself by leaving the rocket without the others' knowledge so that they have enough oxygen to make it to Earth, leaving a note asking for forgiveness.
The rocket lands on autopilot in Syldavia, with the entire crew unconscious from lack of oxygen. Despite a brief scare with Haddock, everyone has survived. Calculus makes a grand speech claiming that man will return to the moon prompting an enraged Haddock to vow never to enter a rocket again, claiming that "Man's proper place...is in dear old Earth!"
- Almost Out of Oxygen / Cold Equation: The biggest problem during the book, beginning with the discovery that the Thompsons accidentally found themselves on board during liftoff... and even that doesn't cover the extent of the stowaways on board. It's solved in part by the Heroic Sacrifice of The Mole.
- Artificial Gravity: Which of course gets accidentally switched off just when the Captain breaks out his hidden bottle of whisky, allowing for some early sight gags before the book's tone turns sour.
- Artistic License – Astronomy and Artistic License – Engineering: Hergé was well aware that the space suits would require helmets much like the astronauts we see today, but then the readers wouldn't be able to tell who was Haddock and who was Tintin? So, for their convenience he made the helmets more fish bowl shaped.
- Ascended Extra: Colonel Jorgen. In his first appearance in King Ottokar's Sceptre he was a pretty minor character who disappeared halfway through the book and was never mentioned again. In this volume, he proves himself to be one of Tintin's most out-and-out heartless and dangerous foes.
- Burial in Space: It doesn't occur on the page, but the heroes jettison Jorgen's body into space. And, of course, Wolff's fate is comparable, although chosen himself.
- Darker and Edgier: While people have been killed in a number of Tintin stories, this is the first to cover the topic of suicide, excluding Mitsuhirato's suicide near the end of The Blue Lotus.
- Dead Man Writing: Wolff leaves a letter explaining his suicidal action and asking for forgiveness.
- Driven to Suicide: Frank Wolff leaves the rocket so that the others have enough oxygen to survive the trip back home.
- Heroic Sacrifice: Wolff.
- In Space Everyone Can See Your Face: Herge knew the bubble-top space helmets were inaccurate, but used them for this trope.
- Karma Houdini: Miller, due to none of the characters even knowing about his involvement.
- Killed Off Screen: Jorgen and Wolff died outside the view of the reader.
- Knight of Cerebus: The story is fairly light hearted for a Tintin album, until Jorgen appears. Unlike other villains in the series, he is played completely seriously.
- Never Speak Ill of the Dead: Haddock regrets his harsh words against Wolff once he learns of his Heroic Sacrifice.
- Prat Fall: Haddock when he says his final line, so he's lying on the ground.
- Redemption Equals Death: Wolff throws himself out the airlock so that the rest of the explorers will have enough oxygen to get back to Earth. Considering that they just barely make it back alive (and still need supplemental oxygen administered), his sacrifice probably did make the difference.
- Reentry Scare: Good lord, yes. Admittedly, the tension involved doesn't really concern the condition of the spacecraft itself so much as the condition of its crew, but all the same, both taking off and landing the craft are consistently depicted as extremely uncomfortable and frightening experiences. One imagines that these sequences alone may have freed more than a few goggle-eyed youngsters in multiple generations from their "I wanna be an astronaut!" phase.
- Science Marches On: Debatable example when Tintin finds ice in a crevasse—for a long time it was thought there was no ice on the moon, but more recently this has been called into question again.
- Still, any ice on the moon could only exist buried underground and intimately mixed with rock; open ice in a cave, as depicted in the book, is impossible.
- Sneaky Departure: Frank Wolff has to go about his Heroic Sacrifice in a stealthy manner, lest the others wake up and try to dissuade him. Of course, Thomson wakes up and, showing the presence of mind expected of the twins, permits him to go down into the hold anyway.
- Space Clothes: Enormous bulky amber-colored spacesuits, representing a very endearingly retro vision of lunar operations (the book was published in 1954, a good fifteen years before Neil Armstrong's historic jaunt). When suited up, the characters look like fat C-3PO units.
- Space Suits Are SCUBA Gear: Notably averted, however, despite how classically retro the spacesuit design looks otherwise. There are no vulnerable oxygen tubes on the exterior of the suit.
- Space Is an Ocean: Hinted at when the nautical-minded Captain Haddock threatens to maroon the Thompsons on a desert star while in space.
- Space Is Noisy: Deliberately refuted in the original comic. The animated version by Belvision embraced this trope, however: while the meteor was silent in the original comic, in the cartoon there is a meteor shower that makes a lot of noise!
- Tech Marches On: The rocket operates by the "direct ascent" model of the whole rocket landing and later leaving on the moon in one piece. Later, NASA concluded that they could never make such a vehicle land tail down safely and went with the method of "Lunar orbit rendezvous," having the rocket traveling in ejecting stages and using a separate lander to land on the moon with the command capsule waiting in orbit to link back up and return to Earth.
- More an inversion in this case: a direct ascent (SSTO = single stage to orbit) and landing requires either much more efficient rockets or MUCH bigger spaceships: both are as much out of reach now as they were then. In fact, a manned landing on the moon is impossible today or in the foreseeable future - but wasn't 50 years ago...
- Threw Himself Out The Airlock: Wolff.
- Tragic Villain: Frank Wolff was the first character in the Tintin universe who wasn't particularly good, but not particulary bad either. He sides with Colonel Jorgen to sabotage the flight, but is more or less manipulated by him. When Jorgen wants to shoot everybody Wolff protests and interferes, killing Jorgen accidentally with his own gun. Wolff is forgiven by Tintin, but later feels remorse and decides to commit suicide by throwing himself out of the rocket so that the others can safely travel home again.
- Your Radio Hates You: The gang listens to Radio-Klow while working to repair the ship... and as soon as it comes on, the announcer says they'll be playing Schubert's "The Gravedigger".