This is the J2-X. The liquid-fuel cryogenic rocket engine is the modernized version of the J-2, which NASA used in the late-'60s and early-'70s to thrust humans beyond low Earth orbit. (Click any image below for hi-res.)
Back then, NASA sent astronauts to deep space aboard the Saturn V. In the years to come, they'll be doing it with the Space Launch System. Perched atop the SLS will be the Orion Multi-Purpose Crew Vehicle — a manned spacecraft the Agency hopes will be used to deliver humans to the Moon (by 2021), asteroids and Mars.