With the Soviet Sputnik success, U.S. space engineers were under pressure not just to catch up but to take the lead. Less than 5 months later, von Braun and his team successfully launched America's first spacecraft, the satellite Explorer 1, on January 31, 1958. Several months after that, Congress authorized the formation of an agency devoted to spaceflight. With the birth of the National Aeronautics and Space Administration (NASA), the U.S. space program had the dedicated resources it needed for the next great achievement: getting a human being into space.

Again the Soviet Union beat the Americans to the punch. In April 1961, Yuri Gagarin became the first man in space, followed only a few weeks later by the American Alan Shepard. Gagarin's capsule managed one Earth orbit along a preset course over which he had virtually no control, except the timing of when retro-rockets were fired to begin the descent. Shepard simply went up and came back down on a suborbital flight, although he did experiment with some astronaut-controlled maneuvers during the flight, firing small rockets positioned around the capsule to change its orientation. Both were grand accomplishments, and both successes depended on key engineering advances. For example, Shepard's capsule, Freedom 7, was bell shaped, a design developed by NASA engineer Maxime Faget. The wide end would help slow the capsule during reentry as it deflected the heat of atmospheric friction. Other engineers developed heat-resistant materials to further protect the astronaut's capsule during reentry, and advances in computer technology helped control both flights from start to finish. But the United States was still clearly behind in the space race.

Then, barely 6 weeks after Shepard's flight and months before John Glenn became the first American to orbit Earth, President John F. Kennedy threw down the gauntlet in what was to become a major battle in the Cold War. "I believe," said Kennedy, "that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth."

NASA's effort to meet Kennedy's challenge was divided into three distinct programs, dubbed Mercury, Gemini, and Apollo, each of which had its own but related agenda. The Mercury program focused on the basics of getting the astronaut up and returning him safely. Gemini, named for the twins of Greek mythology, fulfilled its name in two ways. First, each Gemini flight included two astronauts, whose main task was to learn to maneuver their craft in space. Second, the overall goal of the program was to have two spacecraft rendezvous and link together, a capability deemed essential for the final Moon missions. Engineers had at least three different ideas about how to accomplish rendezvous. Gemini astronaut Buzz Aldrin, whose doctoral thesis had been on just this subject, advocated a method founded on the basic principle of orbital mechanics that a craft in a lower orbit travels faster than one in a higher orbit (to offset the greater pull of gravity at a lower altitude). Aldrin argued that a spacecraft in a lower orbit should chase one in a higher orbit and, as it approached, fire thrusters to raise it into the same orbit as its target. The system was adopted, and on March 16, 1966, Gemini 8, with Neil Armstrong and David Scott aboard, achieved the first docking in space, physically linking up with a previously launched, unmanned Agena rocket.