Chosen to power the upper stages of the new Ares I Crew Launch Vehicle (CLV) and the Ares V cargo segment, the J-2X engine is a stepped up version of the hydrogen/oxygen-fuelled Apollo-era J-2 engine. It was developed for NASA by Pratt & Whitney Rocketdyne (PWR), a business unit of United Technologies Corporation of Canoga Park, California. As seen in this photograph, the engine underwent a series of hot fire tests, performed on sub scale main injector hardware in the Test Stand 116 at Marshall Space Flight Center (MSFC). The injector is a major component of the engine that injects and mixes propellants in the combustion chamber, where they are ignited and burned to produce thrust.