Pratt & Whitney Rocketdyne employees Carlos Alfaro (l) and Oliver Swanier work on the main combustion element of the J-2X rocket engine at their John C. Stennis Space Center facility. Assembly of the J-2X rocket engine to be tested at the site is under way, with completion and delivery to the A-2 Test Stand set for June. The J-2X is being developed as a next-generation engine that can carry humans into deep space. Stennis Space Center is preparing a trio of stands to test the new engine.