John C. Stennis Space Center in south Mississippi is one of 10 NASA field centers in the United States. Because of its important role in engine testing for four decades, Stennis is NASA's program manager for rocket propulsion testing with total responsibility for conducting and/or managing all NASA propulsion test programs. Stennis tested the first and second Saturn V rocket stages for NASA's Apollo Program, including those used to carry humans to the moon. In fact, in the late 1960s and early 1970s, there was a saying in the communities surrounding Stennis, "If you want to go to the moon, you first have to go through Hancock County, Mississippi."

In 2009, Stennis completed 34 years of testing space shuttle main engines used on more than 130 low-Earth orbit missions. The high-performance, liquid-fueled engines provide most of the total thrust needed during the shuttle's eight and one-half-minute-flight to orbit. All space shuttle main engines had to pass a series of test firings at Stennis prior to being installed in the back of an orbiter. Stennis also provided testing for engine components, design modifications and shuttle-related needs as they arose.

Next-generation rocket engines now are being developed to help carry humans beyond low-Earth orbit once more. Stennis is testing the J-2X engine for use on NASA's new Space Launch System (SLS). The center also will test RS-25 engines that will power the SLS core stage.