NASA engineers are excited by their first hot-fire tests this summer of 3-D printed rocket engine parts. Reports no problems. Marshall engineers installed this 3-D printed engine injector in a subscale RS-25 engine model, and the engine was hot-fired exposing the part to temperatures of nearly 6,000 degrees Fahrenheit while burning liquid oxygen and gaseous hydrogen. A series of tests was completed in Test Stand 115 in the East Test Area at NASA’s Marshall Space Flight Center in Huntsville, Ala.