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Rocket Genealogy
This chart shows the lineage of major U.S. space launch vehicles (view larger image). Many trace their roots to the V-2, brought back from Germany after World War II. Previously, the United States had been developing rockets, such as the Corporal, but none was as sophisticated as the V-2.
The postwar period saw the birth of the Army's Aerobee and Bumper (the first two-stage rocket) and the Navy's Viking sounding rockets. Viking was chosen as the first stage and Aerobee as the second stage for the Navy's Vanguard rocket. Vanguard later lent components and systems to Thor and its successor, Delta, as well as the small Scout rocket and the Air Force's Atlas. Scout was America's first solid-fuel launch vehicle capable of putting a satellite into orbit; it took its first stage from the Navy's Polaris missile and upper stages from Vanguard. Polaris technology would also find its way into Minuteman ICBMs. Minuteman technology is now used to build small launch vehicles such as Pegasus and Minotaur.
Another early weapon program led to the Navaho cruise missile. Although the Navaho program did not last long, its legacy was significant. The Navaho booster engine, adapted from the V-2, was used in the development of Atlas, Redstone, Jupiter, Thor, and Titan I.
Atlas D, the first operational ICBM, was deployed in 1959. These missiles were later refurbished as space launch vehicles. Atlas gave way to the Atlas II family, which gave rise to Atlas V, one of two boosters in the Evolved Expendable Launch Vehicle (EELV) program.
The Thor ballistic missile program began in 1954. Although its airframe design was new, some of Thor's subsystems were borrowed from Atlas, including the guidance system and the Navaho-based booster engine. The Air Force soon began adding upper stages to Thor, creating Thor-Able, Thor-Able Star, Thor-Agena, and Thor-Delta—or simply Delta, as it came to be known.
Delta was first launched in 1960 using a second stage borrowed from Vanguard. Solid-rocket motors, derived from Scout, were added a few years later. Today, Delta IV is one of two boosters in the EELV program.
In 1961, the Army's Redstone rocket carried the first American into space. The Redstone, given two upper stages, became Jupiter C, later renamed Juno I; its liquid-propellant main-stage engine came from Navaho. A Jupiter C placed the first U.S. satellite into orbit. Juno I and the Jupiter ballistic missile combined to form Juno II. Redstone, Jupiter, and Juno led to the Saturn series, culminating in the massive Saturn V.
The first Titan ICBM was deployed in 1962. Development of Titan II began the same year. Many variants of Titan III emerged, including the IIIC and 34D, whose solid motors were derived from Minuteman. The seven-segment Titan IIIM, conceived but never built for the canceled Manned Orbiting Laboratory, later resurfaced as Titan IV.
Centaur was the first American high-energy, liquid-hydrogen/liquid-oxygen rocket. Until 1974, Centaur was used exclusively with Atlas. It was later used with the Titan III and IV boosters and contributed to the Saturn series.
Propulsion system concepts and technologies from Saturn V and Titan III were applied to the space shuttle, whose main engines in turn contributed to the RS-68 engine used on Delta IV.
