The novel introduces Bowman in Part 3, aboard the spacecraft Discovery. Along with Frank Poole and three hibernating crew members, he has been sent on a mission to Saturn—though he is not aware of the true nature of the mission until he is nearly there. His name is an allusion to Homer's The Odyssey. He is the Bow-Man, embarking on a lengthy, dangerous voyage with an uncertain outcome. In Homer's epic poem, Odysseus returns home from war after a lengthy voyage and must win back his wife and home using his prowess as an archer Bowman is the ideal astronaut—a disciplined, loyal, and emotionally stable man who is able to recover from a terrifying crisis in space, take action to solve a dangerous malfunction in Hal, and go on to complete the Saturn mission alone. He copes with the stress of the situation by adhering tightly to routine, retaining a link to his humanity through literature and music, and focusing on his unique opportunity to be an ambassador of the human race to an unknown alien life form. Bowman's persistence and ingenuity are rewarded as he is given experiences no human has ever had. After going through the Star Gate, he enters a timeless and nearly immaterial state in which he can achieve immortality.
The HAL 9000, Discovery's computer system, is better known to the crew as Hal. Although Hal is a computer, his programming is so complex he can "pass the Turing test with ease," proving his ability to think, rather than simply calculate. Hal's complexity has given him many human characteristics, so that he has a unique personality. In fact, in many ways he is the most well-developed character in the novel. Hal is so human that he experiences conflicting emotions and impulses—a drive for perfection, a fanatical commitment to the mission, guilt, and shame. Over time, these internal conflicts cause Hal to make a mistake and then create an elaborate lie to cover it up. His deceptions eventually result in a crisis and his own deactivation.
Moon-Watcher is the prehuman main character in Part 1 of the novel, which takes place in prehistoric times. He is the leader of a tribe of man-apes who, one day while at the river for water, encounter a "New Rock"—a monolith placed there by alien beings. Although he has the seeds of humanity in his genes, he and the other man-apes are near extinction due to lack of food. Moon-Watcher is an excellent student of the New Rock's teaching. Under its influence he is able to use weapons to hunt for food, allowing tribe members to transition from herbivores to omnivores, and ensuring a continuous food supply that can allow for the development of higher brain functions. The tool quickly becomes a weapon to subdue a rival tribe, a step viewed in the novel as a crucial one in human evolution.
Dr. Heywood Floyd
Dr. Floyd is the main character in Part 2 of the novel, and the narrator follows him from Earth, to Space Station One, to the moon, where he functions as the main consultant and decision-maker regarding what to do about TMA-1. Although not a well-rounded character, Floyd's function in the plot is important, as he is present for the study of TMA-1 and then becomes part of Discovery's Mission Control. In this way, he helps tie the parts of the story together. He also helps develop the setting and themes of the novel. His flight from Earth to the moon reminds the reader of the importance of the moon to human spaceflight. And his conversations with various characters bring out some of the practical issues related to the discovery of TMA-1. For example, his conversation with a Russian colleague and his discussions about the potential for the monolith to be of Chinese origin brings realistic political context to the story. After all, the discovery of such an artifact would have repercussions for an Earth divided into competing nations. Dr. Floyd's section of the novel invites readers to think about these repercussions.
A deputy on the Discovery One, Frank Poole is, along with Dave Bowman, one of the two crew members who are sentient during the mission, not in suspended animation. Poole is murdered by Hal after the computer learns Poole thinks it should be disconnected. He dies while trying to replace the AE-35 unit, which Hal has reported as malfunctioning. Although he dies before reaching Saturn—and thus never has the chance to be transformed into a Star-Child like Bowman, Poole's role is quite significant because he becomes a victim of artificial intelligence.
An extraterrestrial, highly intelligent and evolved alien race is a driving force throughout much of the novel, although actual alien beings are absent from the novel until its final chapters. The alien race, in an attempt to identify and foster the growth of intelligent species throughout the universe, deploys various devices—the monoliths. One of these devices lands on Earth, and helps Moon-Watcher and his tribe learn the skills they will need to survive and evolve. Another monolith is installed on the moon and is triggered when it is excavated by humans and comes into contact with solar energy. This monolith is an alarm that, when triggered, alerts Star Gate (another monolith installed on a moon of Saturn) to the fact that humans have achieved spaceflight. The extraterrestrial species was once made up of organic beings, who then learned to transfer their consciousness into machines, and who finally evolved to become creatures of "pure Mind." After David Bowman passes through the Star Gate, one of these creatures, metaphorically called a "weaver" as he weaves Bowman's consciousness into its new framework, transforms Bowman into an immortal and powerful life form.