Testing of the NASA Hypersonics Project Combined Cycle Engine Large Scale Inlet Mode Transition Experiment (CCE LlMX)

Abstract The NASA Fundamental Aeronautics Hypersonics project is focused on technologies for combined cycle, air-breathing propulsions systems to enable highly reliable reusable launch systems for access to space. Turbine Based Combined Cycle (TBCC) propulsion systems offer specific impulse (I sp ) improvements over rocket-based propulsion systems in the subsonic takeoff and return mission segments and offer improved safety. The potential to realize more aircraft-like operations with expanded launch site availability and reduced system maintenance are additional benefits. Among the most critical TBCC enabling technologies as identified in the National Aeronautics Institute (NAI) study were: 1) mode transition from the low speed propulsion system to the high speed propulsion system, 2) high Mach turbine engine development and 3) innovative turbine based combined cycle integration. To address these key TBCC chall enges, NASA’s Hypersonics project (TBCC Discipline) initiated an experimental mode transition task that includes an analytic research endeavor to assess the state-of-the-art of propulsion system performance and design codes. This initiative includes inlet fluid and turbine performance codes and engineering-level algorithms. This effort has been focused on the Combined-Cycle Engine Large Scale Inlet Mode Transition Experiment (CCE LIMX) which is a fully integrated TBCC propulsion system with flow path sizing consistent with previous NASA and DoD proposed Hypersonic experimental flight test plans. This experiment is being tested in the NASA Glenn Research Center 10- by 10-ft Supersonic Wind Tunnel (SWT) Facility. The goal of this activity is to address key hypersonic combined-cycle engine issues: (1) dual integrated inlet operability and performance issues—unstart constraints, distortion constraints, bleed requirements, controls, and operability margins, (2) mode-transition sequence elements caused by the switch between the turbine and the ramjet/scramjet flow paths (imposed variable geometry requirements), (3) turbine engine transients (and associated time scales) during transition. The model will be tested in four test phases to develop a unique TBCC database to validate design and analysis tools and address operability, integration, and interaction issues for this class of advanced propulsion systems. The test article insta llation and facility build-up/preparation was completed and the inlet performance and operability characterization testing commenced on March 7, 2011. The major upcoming events of this activity include: • Phase I: Parametric inlet characterization testing completed —2