The North American SM-64 Navaho was a supersonic intercontinental cruise missile project built by North American Aviation (NAA). The final design was capable of delivering a nuclear weapon to the USSR from bases in the US, while cruising at Mach 3 (2,284 mph; 3,675 km/h) at 60,000 feet (18,000 m) altitude. The missile is named after the Navajo Nation.The original 1946 project called for a relatively short-range system, a boost-glide weapon based on a winged V-2 rocket design. Over time the requirements were repeatedly extended, both due to the US Air Force's desire for longer ranged systems, as well as competition from similar weapons that successfully filled the shorter-range niche. This led to a new design based on a ramjet powered cruise missile, which also developed into a series of ever-larger versions, along with the booster rockets to launch them up to speed.Through this period the US Air Force was developing the SM-65 Atlas, based on rocket technology developed for Navaho. Atlas filled the same performance goals, but could do so with total flight times measured in minutes rather than hours, and flying at speeds and altitudes which made them immune to interception, as opposed to simply difficult as in the case of Navaho. With the launch of Sputnik 1 in 1957, and the ensuing fears of a missile gap, Altas received the highest development authority. Navaho continued as a backup, before being cancelled in 1958 when Atlas successfully matured.Although Navaho did not enter service, its development provided useful research in a number of fields. In particular, the booster engine design, spun off to NAA's new Rocketdyne subsidiary, was used in various versions by the Atlas, PGM-11 Redstone, PGM-17 Thor, PGM-19 Jupiter, Mercury-Redstone, the Juno series, and is the direct descendant of the engines used to launch the Saturn I and Saturn V moon rockets.