High Speed Systems Test
Abstract
The HSST project continued to advance ground and flight test technologies, techniques, instrumentation, and modeling and simulation capabilities required for the development of high speed air-breathing propulsion and boost-glide weapons. HSST continued progress toward addressing the two most significant technology shortfalls in current hypersonic aero propulsion ground test capabilities: clean air heat addition (i.e. non-vitiated air) and variable Mach number test capability. Current production ground test facilities create the high temperature propulsion system inlet conditions necessary for air-breathing scramjet engine testing by burning fuel in the facility airflow supplied to the engine inlet for operation. As demonstrated by a previous HSST test, the resulting vitiated air has different gas properties than clean air found in the atmosphere and thus is not representative of what the vehicle would experience during flight. This significantly affects the engine’s performance and operability in the test environment resulting in erroneous flight performance predictions. In addition to the ability to test in clean air, a variable Mach number capability is required to “fly the mission” and determine the critical transient operability effects throughout the flight envelope. Incorporation of component technologies, previously developed by the T&E/S&T program, were integrated into a small-scale, clean air, true temperature, and variable Mach number (M4.5-7.5) aero propulsion test facility, called the Hypersonic Aerothermal and Propulsion Clean Air Testbed (HAPCAT). Completion of this facility will demonstrate that the component technologies and their integration have reached Technology Readiness Level (TRL) 6, provide an on-going test asset to the DoD, and reduce risk for construction of a full-scale facility. The HAPCAT project continued to develop and demonstrate air delivery system (ADS) technologies to provide uniform flow with variable pressure and temperature through a nozzle up to Mach 7.5 conditions. The project activities included the design and initial fabrication of the ADS and conceptual design of a full scale facility. Efforts continued on the morphing ceramic nozzle for hypersonic ground test facilities project which seeks to achieve a variable Mach number capability and variable inlet distortion patterns representative of flight-like inlet systems. Following validation testing conducted at the Air Force Research Lab (AFRL), efforts were made to begin the refurbishment of the nozzle for implementation into the HAPCAT facility. Construction of the Large Energy National Shock (LENS) Tunnel II extension was completed and evaluated to verify extended run times. Such testing will enable the full development of complex flow features affecting vehicle performance, the determination of control surface responsiveness and effectiveness, and the evaluation of the performance of aerodynamic features. The improvements will help fill a critical test capability gap and support future hypersonic vehicle programs. Initial facility performance assessments of the extended tunnel demonstrated a three-fold increase in test run time. The facility was successfully used by multiple customers who required the expanded capabilities in order to meet their test objectives. The HSST project continued development of a mid-pressure arc heater prototype. The prototype replaced an existing Huels arc heater with a segmented heater, creating a test envelope approximately three times larger than the current envelope for aerothermal testing. Validations runs were successfully completed confirming extended test run times of up to 30 minutes and a higher thermal load representative of that experienced by a hypersonic vehicle TPS. These efforts advanced progress toward the goal of improved T&E of maneuvering reentry and boost/glide vehicles. In a related effort, the arc heater flow quality aerothermal test technology development progressed toward independently-powered spin-coils to control the physical characteristics of the spinning arc column, its attachment location and duration on electrode surfaces within the arc heater. The effort investigated two different spin-coil designs, one of which was validated for use in the mid-pressure arc heater facility. This effort will improve the service life of the electrodes and improve nozzle flow quality. The HSST project continued research that will provide better prediction and determination of boundary layer growth and transition effects upon hypersonic vehicle performance. Understanding and predicting boundary layer transition represents a critical shortfall in the hypersonic community, as it affects the thermal loads, stability and control, and overall performance of a vehicle. Experimental results acquired through the boundary layer transition effort will be used to validate state of the art prediction tools and measurements of boundary layer transition mechanisms. Facility flow field characterizations were conducted at the Purdue quiet tunnel and the LENS facilities at CUBRC, enabling more effective comparisons between all the facilities and informing test customers of intrinsic flow features in each facility. The characterizations will also provide insight to boundary layer transition studies in these facilities. The project also conducted testing of a boost-glide vehicle, resulting in critical findings to support future flight tests of the vehicle. HSST completed development of a ground based, portable high altitude light detection and ranging (LIDAR) system to measure atmospheric conditions (density, temperature, pressure, wind speed/direction, oxygen/water content) along a hypersonic vehicle’s flight path. This technology is a significant advancement over current methods, which employ balloons carrying sensors to sample the atmosphere. The LIDAR will improve the accuracy of characterizing high altitude atmospheric conditions. This atmospheric data is needed to assess the performance and operability of air-breathing missiles and boost-glide vehicles during development. Testing and demonstration of LIDAR atmospheric sensing was completed and the portable system was transitioned to support test programs at coastal flight test ranges to demonstrate system performance in a maritime environment. Development of an airborne version of the LIDAR continued with the design and testing of hardware components for the in-flight demonstration of the system on a crewed aircraft in preparation for implementation on an uncrewed vehicle. Progress continued on a high fidelity automated airborne reconfigurable tracking system which seeks to provide high resolution imaging of hypersonic vehicles in flight. The final design was completed including concepts for integration onto a Global Hawk aircraft. The fabrication, and installation of a telemetry capability integrated with a High Altitude, Long Endurance Uncrewed Aerial System (HALE UAS) for a technical demonstration continued in preparation for support of flight testing. Measurements of thermal emissions from the surface of typical boost-glide vehicles in an impulse test facility were conducted to evaluate the effectiveness of different surface compositions and treatments and filter frequencies for thermal imaging. The completion of this project resulted in valuable insights gained for a boost-glide vehicle design; these insights will be useful for future testing in high-enthalpy (high-energy) facilities. Advances were achieved in the development of M&S tools. Verification and improvement of computational fluid dynamics (CFD) codes continued, making use of the unique data sets obtained from HSST scramjet engine tests and boundary layer experiments. A technical report was generated that summarizes the methodology for conducting boundary layer stability computations in support of acquisition programs, including shortfalls in current capabilities and recommended improvements for the toolsets available. This report was released to the hypersonic community and serves as a benchmark document for use in hypersonic programs. The HSST transient thermal analysis software effort transitioned to users in the hypersonic community to support ground testing and flight testing. A force measurement system technology development completed for use in short-duration, high-enthalpy test facilities. Such technology will permit testing that elucidates real gas effects on hypersonic vehicles.
Document Details
- Document Type
- Accomplishment
- Publication Date
- Oct 01, 2019
- Source ID
- 16dc85c2188a116efd3eecca7cad03f3