Between Planets

Between Planets is a juvenile science fiction novel by the American writer Robert A. Heinlein. First released in serial form in 1951 under the title Planets in Combat, it appeared later that year as a hardcover edition published by Charles Scribner’s Sons as part of Heinlein’s influential series of juvenile novels. Blending interplanetary adventure with political allegory, the novel follows a young protagonist caught between competing loyalties during a time of revolution across the Solar System.

Narrative Overview

The story centres on Don Harvey, a teenager abruptly withdrawn from his school in New Mexico when his scientist parents summon him to join them on Mars. His departure is framed by mounting geopolitical tensions, and the school headmaster hints that Harvey’s ambiguous background—born in space to parents of Earth and Venus—might expose him to suspicion during the gathering crisis.
Before leaving Earth, Harvey is tasked by a family friend with delivering a ring to his father. Security forces intervene and arrest both men, though Harvey is released without explanation and the ring is returned to him after inspection. Only later does he recognise the falsehood surrounding the friend’s reported death.
From Earth he travels by shuttle to an orbital station that serves as both a transport hub and an armed military platform. On the journey he befriends Sir Isaac Newton, a highly intellectual dragon from Venus capable of speaking English through a portable device. Harvey soon becomes entangled in Venus’s war for independence when Venerian forces seize the space station. Most travellers are repatriated to Earth, but Harvey claims Venerian citizenship and, aided by Sir Isaac’s endorsement, accompanies the rebels instead.
The destruction of the station by the rebels leads Earth’s military to mistakenly obliterate a returning shuttle, heightening the conflict. When Harvey reaches Venus, he finds his Earth-backed money worthless, earning temporary sustenance from a restaurant owned by Charlie, an immigrant from China. During this period he befriends Isobel, a young woman fleeing the chaos and helping him conceal the ring when government agents pursue him.
As the rebellion falters under a powerful Earth counterattack, Charlie is killed resisting the occupation, and Harvey is imprisoned by security forces seeking the ring’s secrets. He escapes before interrogation drugs can be administered and joins the guerrilla resistance. The resistance leaders eventually locate him, as they too seek the ring. To his relief, Isobel and her father—a senior rebel leader—are alive, and he is taken to a secure base.
The ring proves to contain advanced scientific information derived from ancient Martian relics. With Sir Isaac’s expertise, the rebels apply this knowledge to create Little David, a radically superior spacecraft equipped with unprecedented propulsion, defences and weaponry. Harvey, now a battle-tested operative, joins the ship’s first mission, charged with detonating it if capture becomes imminent. The ship successfully intercepts and defeats an Earth flotilla en route to Mars, helping to safeguard the wider rebellion.

Scientific Context

Typical of mid-twentieth-century science fiction, the novel portrays Venus and Mars as habitable worlds with Earth-like conditions. At the time of writing, no space probes had surveyed either planet, and their true atmospheric conditions were unknown. As a result, the depiction reflects the scientific speculation of its era, including misconceptions regarding surface pressure, temperature and planetary rotation.

Critical Reception

Upon publication, Between Planets received strong reviews within the science fiction community. Groff Conklin described it as a vivid and convincing presentation of future possibilities. Critics Anthony Boucher and J. Francis McComas listed it among the best science fiction novels of 1951, praising its maturity compared with contemporary adult works. P. Schuyler Miller commended the logical structure and narrative clarity, though he felt it lacked the extensive world-building typical of Heinlein’s broader oeuvre.
Later assessments noted Heinlein’s increasing shift from juvenile adventure to themes of political autonomy and personal freedom. Jack Williamson argued that the novel marked a step toward more adult concerns within Heinlein’s juvenile series, balancing traditional space opera elements with well-drawn characters and a zestful narrative voice. Its closing remarks on the tension between individual liberty and expanding governmental power were seen as particularly pointed.

Adaptation in Graphic Media

In 1978, Between Planets was adapted into a monthly cartoon serial for Boys’ Life magazine. The adaptation made several modifications, such as depicting the Venerian dragons as humanoid and altering planetary names, likely influenced by the growing scientific understanding that neither Venus nor Mars could support human life. Despite these deviations, the serial was broadly faithful to the spirit and core storyline of Heinlein’s novel.