Rocketdyne
The Rocketdyne Division was founded by North American Aviation (NAA) in 1955, and was later part of Rockwell International (1967-1996) and Boeing (1996-2005). In 2005, the Rocketdyne Division was sold to United Technologies Corporation, becoming Pratt & Whitney Rocketdyne as part of Pratt & Whitney. In 2013, Pratt & Whitney Rocketdyne was sold to GenCorp, which merged it with Aerojet to form Aerojet Rocketdyne.
Rocketdyne J-2
An experimental program to improve the performance of the J-2 started in 1964 as the J-2X (not to be confused with a later variant by the same name). The main change to the original J-2 design was a change from the gas generator cycle to a tap-off cycle that supplied hot gas from a tap on the combustion chamber instead of a separate burner. In addition to removing parts from the engine, it also reduced the difficulty of starting up the engine and properly timing various combustors.