X-51A Completes Low-Mach Test Series Published Sept. 25, 2007 By Propulsion Directorate AFRL/PR WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- AFRL engineers completed low-Mach tests on the SJX61-1 engine using the National Aeronautics and Space Administration (NASA) Langley Research Center's 8-foot high-temperature tunnel. The Pratt & Whitney Rocketdyne SJX61-1 (or X-1) is a hydrocarbonfueled scramjet [supersonic combustion ramjet] engine featuring full X-51A flight hardware: flowpath with forebody and nozzle, F-119 fullauthority digital engine control/fuel control, and closed-loop thermal management system. The X-1 successfully completed low-Mach testing, demonstrating JP-7 operation at flight-simulated Mach 4.6 and 5.0 conditions. Early estimates indicate measured performance and operability meet or exceed pretest predictions. To date, the X-1 has logged over 900 seconds of combustion time, more than the previous AFRL HyTech ground demonstration engines 1 and 2 combined. Despite enduring over 35 hot cycles, engine hardware remains in excellent condition. Completion of this test series is a critical step in the development of the X-51A integrated propulsion system and has provided the data necessary to support the X-51A Critical Design Review. The X-51A Flight Test program plans to demonstrate the AFRL HyTech scramjet engine within the Mach 4.5 to 6.5 range with four flight tests, beginning in Fiscal Year 2009. The X-51A program is a collaborative effort between the Air Force; the Defense Advanced Research Projects Agency; Boeing (Huntington Beach, California); NASA; and X 1 builder Pratt & Whitney Rocketdyne. The dedication of the joint NASA/Pratt & Whitney Rocketdyne test team made the successful test a reality. Subsequent tests will characterize the closed-loop thermal management system at Mach 6.5 conditions. The X-1 is the first of two ground engines planned in the X-51A Flight Test program.