Rocketdyne is the premier rocket engine design and production company in the United States. The company was related to North American Aviation for most of its history. NAA merged with Rockwell International, which was then bought by Boeing in December, 1996. In February, 2005, Boeing reached an agreement to sell Rocketdyne to Pratt & Whitney, and this transaction was completed on August 2, 2005.
Rocketdyne was formed by NAA in the immediate post-WWII era to study the German V-2 missile and adapt its engine to SAE measurements and US construction details. They also used the same general concept of separate burner/injectors from the V-2 engine design to build a much larger engine for the Navaho missile project. This work was considered unimportant in the 1940s and funded at a very low level, but the opening of the Korean War in 1950 changed priorities. Navaho ran into continual difficulties and was cancelled in the late 1950s when Redstone missile design (essentially a much larger V-2) had caught up in development. However the Rocketdyne engine, known as the A-5 or NAA75-110 proved to be considerably more reliable than the one developed for Redstone, so the missile was redesigned with the A-5 even though the resulting missile had much shorter range. As the missile entered production NAA spun off Rocketdyne in 1955 as a separate division.
Rocketdyne's next major development was their first all-new design, the S-3D, which had been developed in parallel to the V-2 derived A series. The S-3 was used on the Jupiter missile design, essentially a development of the Redstone, and was later selected for the considerably more capable Thor missile. An even larger design, the LR89/LR105, was used on the Atlas missile. Both Thor and Atlas had a short military careers, but were used as satellite launchers 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 their updated RS-27 design, originally developed as a single engine to replace the three-engine cluster on the Atlas.
Rocketdyne also became the major supplier for NASA's development efforts, supplying all of their major engines for the Saturn (and potentially, Nova) designs. Rocketdyne's H-1 engine was used by the Saturn I booster main stage, which consisted essentially of a cluster of eight Jupiter's. The F-1 powered the Saturn V's, S-IC, first stage, while the J-2 powered its S-II second, and third stages, S-IVB. By 1965 they built the vast majority of US rocket engines, and their payroll had expanded to 65,000. This sort of growth appeared to be destined to continue in the 1970s when they won the contract for the Space Shuttle Main Engine, but the rapid downturn in both military and civilian contracts led to a similar downsizing of the company as well. North American, now largely a spacecraft provider and also tied almost entirely to the Space Shuttle, merged with Rockwell in 1966 to form North American Rockwell (soon to become Rockwell International), with Rocketdyne as a major division.
During continued downsizing in the 1980's and 90's, Rockwell shed several parts of the former NAA empire. First to go was their General Aviation division in 1980, followed by the venerable Saberliner bizjet division in 1983. The rest of NAA, along with Rocketdyne, was sold to Boeing in 1996. Rocketdyne served as part of Boeing Integrated Defense Systems until its sale to Pratt & Whitney on August 2, 2005. 
Some of the engines developed by Rocketdyne are:
- H-1 (RP-1/LOX) Used by the Saturn I, Saturn Ib, Jupiter, and some Delta rockets
- F-1 (RP-1/LOX) Used by the Saturn V.
- J-2(LH2/LOX) Used by both the Saturn V and Saturn IB.
- SSME (LH2/LOX) The space shuttle main engine
- RS-68 (LH2/LOX) Used by the Delta IV first stage
- RS-27A (RP-1/LOX) Used by the Delta II/III and Atlas ICBM
Many Rocketdyne engines were tested at Boeing's Santa Susana Field Laboratory, (SSFL), located in the Santa Susana Mountain Range and Simi Hills, (northwest of Los Angeles, and Chatsworth, California). Rocketdyne, now known as Pratt & Whitney Rocketdyne, Inc., a wholly owned subsidiary of United Technologies Corporation, is headquartered in Canoga Park, California and has additional operations in West Palm Beach, Florida, Huntsville, Alabama, Kennedy Space Center, Florida and Stennis Space Center, Mississippi.
Rocketdyne produced many projects and programs concurrently with Edwards Air Force Base located in the Antelope Valley within the high desert area of California at Rosamond, as did the aerospace industry corporation, Lockheed, now known as Lockheed Martin.