Pratt & Whitney Rocketdyne said April 24 that it has completed the last in a series of hot-fire tests on a J-2X development engine with a stub-nozzle extension. The Canoga Park, Calif.-based propulsion company said the tests, conducted at NASA Stennis Space Flight Center’s A-2 test stand in Mississippi, pave the way toward full motion testing of the J-2X, which NASA plans to use to power the upper stage of the evolved Space Launch System heavy-lift rocket, which will be capable of hauling 130 metric tons of payload to orbit. Initial SLS flights will use a modified Delta 4 upper stage provided by Boeing Co.

The stub-nozzle J-2X engine was tested six times at simulated altitude conditions for a total of 2,156 seconds, Pratt & Whitney Rocketdyne said in a press release. The next step in the program calls for moving the engine to Stennis’ A-1 test stand where it will be fired to test the range of gamble motion for its flexible parts.

The engine is the second J-2X development engine Pratt & Whitney Rocketdyne has built for NASA. The first development engine was tested 21 times in 2012 for a total of 45 minutes.