Joan is an astronomy professor at Rice University who joins the first class of women astronaut candidates at NASA. She is a classically trained pianist and an amateur portrait artist. A grounded woman, she often downplays her own significant talents and struggles to assert herself emotionally with her demanding family. Her fascination with the stars provides her with a deep sense of connection to the universe.

Vanessa is a commercial pilot and aeronautics engineer with a fiercely independent streak. Having lost her military pilot father at a young age, she spent her youth acting out before finding purpose in aviation. She is determined to fly a NASA shuttle, pushing aggressively against the systemic rules designed to keep women out of the pilot's seat.

Barbara is Joan's younger sister and a single mother living in Houston. She frequently places herself in the role of the victim, relying heavily on Joan's time and financial support to manage her daily life. She prioritizes her own comfort and social status over her parental responsibilities to her young daughter.

Frances is Barbara's young daughter who is largely raised by her aunt Joan. She is intelligent and observant, though she keenly feels the sting of her mother's absenteeism. She develops a strong interest in space, looking up to her aunt's pioneering career.

Griff is a mission specialist candidate who comes from a privileged New England prep school background. He immediately establishes himself as a supportive, respectful ally to the women in the program. He consistently stands up against the misogyny of his male peers.

Donna is an emergency room physician and mission specialist candidate. She quickly forms a tight-knit supportive circle with Joan and Griff during their initial training days. She is practical and friendly, carefully guarding her personal life from NASA's strict scrutiny.

Lydia is a highly skilled trauma surgeon and mission specialist candidate. Intensely competitive, she believes she must play by the men's rules to succeed, often laughing at crude jokes to ingratiate herself with the male pilots. She views the other women not as allies but as rivals for a limited number of flight spots.

Hank is a Texas-born pilot candidate known for his southern politeness and respectful demeanor. Unlike many of the military men, he treats the women candidates as equals and actively helps them secure their required flight hours.

Jimmy is a military pilot candidate who embodies the institutional sexism of the 1980s space program. He routinely makes lewd, demeaning comments designed to isolate the women and remind them that they do not belong in space.

Steve is an experienced astronaut instructor and shuttle commander. He represents the established NASA vanguard but distinguishes himself by actively mentoring the new candidates, taking a particular interest in Vanessa's exceptional piloting skills.

Antonio is the director of flight at the Astronaut Office. He is responsible for evaluating the candidates, assigning missions, and managing the delicate public relations image of NASA's newly integrated shuttle program.

Daniel is an affluent man, ten years Barbara's senior, who offers her a comfortable suburban life. While superficially polite, he is arrogant and has little patience for Barbara's daughter, actively encouraging Barbara to distance herself from the child.

Jack is the flight director in Mission Control. He bears the heavy responsibility of making life-or-death decisions during spaceflight emergencies, relying on his communications officers to relay critical instructions to the astronauts.

Helene is Steve Hagen's wife. As the spouse of a senior astronaut, she participates in the social functions that bond the NASA community together while enduring the constant, quiet anxiety of her husband's dangerous profession.

Thea is the infant daughter of Donna and Hank. Her arrival brings joy to her parents but forces them to manage NASA's strict policies regarding family and active flight status.