Space Cadet is a 1948 science fiction novel by Robert A. Heinlein about Matt Dodson, who joins the Space Patrol to help preserve peace in the Solar System. The story translates the standard military academy story into outer space: a boy from Iowa goes to officer school, sees action and adventure, shoulders responsibilities far beyond his experience, and becomes a man. It was published as the second of the series of Heinlein juveniles.
Burke eventually either resigns or is asked to leave, but the remainder do well enough to be assigned to working Patrol ships. Dodson, Jarman and Jensen ship out on the Aes Triplex. Their first real mission is to help search for a missing research vessel, the Pathfinder, in the Asteroid Belt. They find it, but all aboard are dead, the unlucky victims of a fast-moving meteor that punctured the ship when the armored outer airlock door was open. Before the accident, a researcher on the Pathfinder had found evidence that the planet which blew up to form the asteroids was inhabited by an intelligent species, and that the explosion had been artificial. The captain of the Aes Triplex transfers half the crew to the repaired Pathfinder so that they can take the ship and the news of the startling discovery back to Earth quickly. With the remainder (including all three cadets), he continues his patrol.
Then, he receives an urgent message to investigate an incident on Venus. He sends Lieutenant Thurlow and the cadets to the planet's surface. The lander touches down in a bad spot and sinks into a sinkhole in the mud, barely giving the crew enough time to get out. Thurlow is injured and comatose, forcing Jensen to take command. He contacts the sentient usually-friendly Venerians, but the entire party is taken captive. They soon find out why.
These particular natives had never seen human beings before, until old classmate Burke showed up in a prospecting ship. He had taken the matriarch of the local clan hostage when she refused to let give him permission to exploit a rich deposit of radioactive ores. The locals promptly attacked the ship and killed his crew; Burke managed to send a message for help before being overcome and taken prisoner.
Jensen skillfully gains the matriarch's trust and convinces her that they are honorable and civilized, contrary to her opinion of Burke, and the Patrolmen are released, but neither ship is flightworthy. Then to their awe and amazement, she takes them to the carefully preserved Astarte, the legendary first ship to set out for Venus over a century before and thought to have been lost en route. According to the log, the crew perished from disease. With the help of the natives, the cadets recommission the ship and fly it back to (human) civilization at Venus's South Pole colony. Dodson is initially disappointed when they are not treated as heroes--but then he realizes that what they accomplished was simply what was expected of Patrolmen.
The cadets are taught that they should renounce their allegiance to their country of origin and replace it by a wider allegiance to humanity as a whole and to all of the sentient species of the Solar System. They are told of four heroes/martyrs whom they should seek to emulate. Heinlein later expanded one of these anecdotes into the short story, "The Long Watch". Another tells of Rivera, who ordered the nuclear bombing of his own hometown because the dictator in power there was doing something unspecified which posed a grave enough risk to world peace. The bombing proceeded on Rivera's orders, even though he was being held captive in the town.
The young, starry-eyed Matt feels that he should be able, if the need arises, to emulate Rivera and destroy his own Iowa hometown with his family and friends in it. But his father tells him such a "need" would never arise, since the Patrol's cosmopolitan allegiance is little more than a sham and in fact it is controlled by the United States and serves its interests. Later, Matt's mentor in the Patrol makes him understand that if such a unlikely threat should occur from Matt's hometown, his commanding officer would lock him in his room rather than expect him to participate in the attack. The mentor uses this scenario to force Matt to confront the personal and political issues involved in the institutional control of atomic weapons in a more mature way.
Written almost a decade before the U.S. Civil Rights Movement, and at a time when non-white characters were almost entirely absent from science fiction, the book also explores the theme of racism, both literally, in discussions of the cosmopolitan racial makeup of the (all-male) Patrol, and metaphorically, in its description of conflict with the Venerians. Venus is described (incorrectly, as is we now know) as intensely hot and swampy, but nevertheless, a habitable, world. The Venerians are at first thought to be primitive, but it is later revealed that they have a high level of technological sophistication, though developed along radically different lines than that of humans.
There is also a subplot revolving around the issue of what it means to be a good soldier. The Patrol is presented as a thinking person's military organization (its motto is Quis custodiet ipsos custodes?), in contrast to the Marines, who are trained to prize unquestioning loyalty and bravery as the highest ideals. Discouraged by the intellectual demands of his Patrol training, and attracted to the glamour and esprit de corp of the Marines, Matt requests a transfer to the Marines, but he is dissuaded from this by his mentor.