A news conference was held around an hour after a successfull 500 second test firing of a J-2X Engine.br br The engine is a key component of NASA's Space Launch System, which will carry the Orion spacecraft, its crew, cargo, equipment and science experiments beyond Earth orbit. br br Pratt and Whitney Rocketdyne is developing the J-2X engine for NASA's Marshall Space Flight Center in Huntsville, Ala. The SLS rocket engines will use a liquid hydrogen and liquid oxygen propulsion system, which will include the J-2X engine for the upper stage and RS-25DE engines (space shuttle main engines) for the core stage.