Pratt & Whitney Rocketdyne said Dec. 21 it has completed assembly of a fuel turbopump for the J-2X rocket engine the Canoga Park, Calif.-based propulsion firm intends to test fire early this year at NASA’s Stennis Space Center in Mississippi.

The J-2X fuel pump assembly follows the assembly of the engine’s oxidizer turbopump, which delivers high-pressure liquid oxygen to the main injector.

Pratt & Whitney Rocketdyne was awarded a $1.2 billion contract in 2007 to develop the J-2X engine to power the upper stages of the Ares 1 and Ares 5 rockets the space agency was then pursuing as part of its Moon-bound Constellation program. The J-2X remains an upper-stage engine candidate for the heavy-lift rocket NASA has been directed by the U.S. Congress to begin developing this year.