essentially a development of the Redstone, and was later selected for the competitor Air Force Thor missile. An even larger design, the LR89/LR105, was used on the Atlas missile. The Thor had a short military career, but it was used as a satellite launcher through the 1950s and 60s in a number of different versions. One, Thor Delta, became the baseline for the current Delta series of space launchers, although since the late 1960s the Delta has had almost nothing in common with the Thor. Although the original S-3 engine was used on some Delta versions, most use its updated RS-27 design, originally developed as a single engine to replace the three-engine cluster on the Atlas. The Atlas also had a short military career as a deterrent weapon, but the Atlas rocket family descended from it became an important orbital launcher for many decades, both for the Project Mercury crewed spacecraft, and in the much-employed Atlas-Agena and Atlas-Centaur rockets. The Atlas V is still in manufacture and use. NASA Rocketdyne also became the major supplier for NASA's development efforts, supplying all of the major engines for the Saturn rocket, and potentially, the huge Nova rocket designs. Rocketdyne's H-1 engine was used by the Saturn I booster main stage. Five F-1 engines powered the Saturn V's S-IC first stage, while five J-2 engines powered its S-II second stage, and one J-2 the S-IVB third stages. By 1965, Rocketdyne built the vast majority of United States rocket engines, excepting those of the Titan rocket (built by Aerojet), and its payroll had grown to 65,000. This sort of growth appeared to be destined to continue in the 1970s when Rocketdyne won the contract for the RS-25 Space Shuttle Main Engine (SSME), but the rapid downturn in other military and civilian contracts led to downsizing of the company. North American Aviation, largely a spacecraft manufacturer, and also tied almost entirely to the Space Shuttle, merged with the Rockwell Corporation in 1966 to form the North American Rockwell company, which became Rockwell International in 1973, with Rocketdyne as a major division. Facilities and operations Canoga Park, California Rocketdyne maintained division headquarters and rocket engine manufacturing facilities at Canoga Park from 1955 until 2014. North American Aviation's rocket development activities began with engine tests nearby the Los Angeles Airport. In 1948, NAA began testing liquid rocket engines within the Simi Hills which would later become the