NASA Has No Clear Use for the J-2X That It Once Needed

NASA's J-2X Engine To Be Mothballed After Testing, Aviation Week

"NASA's J-2X engine, once considered the pacing item for the next U.S. human-rated rocket, will go on the shelf after development testing wraps up next year because it will be years before the engine is needed to push humans toward Mars. While the agency is actively seeking other missions for the heavy-lift Space Launch System (SLS) in the planetary science and military arenas, most of the human flights it has in sight for the big new rocket probably can be accomplished with an upper stage powered by the RL-10 engine instead of the J-2X. "The J-2X for certain [design reference missions] is somewhat overpowered," said Todd May, NASA's SLS program manager."

NASA MSFC Solicitation: J-2X Design, Development, Test and Evaluation (2006)

"NASA/MSFC has a requirement for the design, development, test, and evaluation (DDT&E) of an engine to support the Crew Launch Vehicle (CLV) Upper Stage and the Cargo Launch Vehicle (CaLV) Earth Departure Stage (EDS). The engine, a J-2 (Saturn Heritage engine) derivative, will be a 250,000 pound thrust class human-rated engine and is planned to support a human launch of the CLV in 2012."

Pratt & Whitney Rocketdyne Awarded $1.2 Billion NASA Contract for J-2X Ares Rocket Engine (2007)

"Pratt & Whitney Rocketdyne (PWR), a United Technologies Corp. (NYSE: UTX) company, was awarded a NASA contract valued at $1.2 billion to design, development and test a J-2X engine that will power the upper stages of the Ares I and Ares V launch vehicles."