“To take an organism whose every feature has evolved to keep it alive and thriving in a world with oxygen, gravity, and water, to suspend that organism in the wasteland of space for a month or a year, is a preposterous and captivating undertaking.”

Roach finds the endeavor to keep the human organism alive in the least likely of environments both foolish and inspiring. Her designation of space as a “wasteland” alludes to one of her main themes, The Hostility of Space. Space lacks all the essentials needed to keep a human alive, much less comfortable. The book’s subtitle also reiterates the setting’s barrenness by referring to space as “the Void”—a place that should be off-limits to humans until scientific curiosity and ingenuity achieve the remarkable.

“Space exploration is in some ways an exploration of what it means to be human. How much normalcy can people forego? For how long, and what does it do to them?”

One of Roach’s themes is that space exploration reveals just as much about humanity as it does about the cosmos. In crossing the boundaries of the Earth, astronauts also test the physical and psychological limits of human existence. The frontiers of space travel are both external and internal; Roach addresses the personal consequences of sleep deprivation, stress, exhaustion, depression, uncleanliness, motion sickness, confinement, and boredom—all of which strain an astronaut’s physical and mental well-being. By framing “normalcy” as a relative condition, Roach emphasizes that space exploration is not only an exercise in conditioning and adaptability, but also in sacrifice and suppression.