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. The HSST project 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 Regenerative Storage Heater (RSH), which utilizes yttria-stabilized zirconia bricks, was demonstrated at temperatures in excess of 4500 R, allowing non-vitiated air up to Mach 7.5 conditions to be supplied. Final design and fabrication of the air delivery system (ADS) was completed, which will permit uniform flow into the test cabin with variable pressure and temperature from multiple sources, including the RSH. Upon installation of the ADS in HAPCAT, the facility will undergo checkout runs to validate its operation to support DoD weapon systems. The design for a free-jet, variable Mach nozzle (VMN) for use in HAPCAT was initiated. Such a capability will permit much more accurate simulation of transient operations along a flight trajectory in a free-jet configuration. The design of the VMN will also serve as a risk-reduction effort for a larger-scale VMN for use in the future full-scale facility. Efforts continued on the design, fabrication, and installation of a variable Mach number direct-connect nozzle for hypersonic ground test facilities that will provide flight-equivalent Mach numbers between 4 and 6 at true temperatures. The nozzle utilizes a metallic flexible wall to vary the Mach number while withstanding the high temperatures. It will be integrated into the HAPCAT facility upon completion for checkout. The development of a high-pressure tunable-diode laser absorption spectroscopy (TDLAS) continued for eventual integration into HAPCAT to provide accurate air temperature measurements at high temperatures and pressures, which will be used for facility control and determination of facility conditions. The TDLAS system will have uses in other facilities as well for temperature measurements. 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. Tests were conducted using a seven degree cone model to evaluate test techniques and boundary layer transition measurement capabilities between various facilities. Tests of a boost-glide vehicle were completed in a quiet wind tunnel environment and a traditional, “noisy” wind tunnel environment, providing insight into the effects of flow field disturbances on boundary layer transition. Facility flow field characterizations were conducted at the Purdue quiet tunnel and the Large Energy National Shock (LENS) facilities at Calspan University at Buffalo Research Center (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 HSST project also conducted testing of a boost-glide vehicle, resulting in critical findings to support future flight tests of the vehicle. The HSST project 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. The HSST project continued the design and development of a UAV-Based Range capability to support hypersonic flight testing. This capability aims to provide a more agile, flexible, and cost-effective method for providing support to hypersonic flight tests in the areas of telemetry, atmospheric sensing, optical imaging, flight safety, and other fields to aid in the development of hypersonic vehicles. The capability will reduce the requirement and high-costs of the “string of pearls” collection of air, sea, and land resources used for hypersonic flight tests. Several different technologies within the HSST project will be integrated as part of the UAV-Based Range. Development of an airborne version of the already completed ground LIDAR system 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 un-crewed vehicle. Design for integration of the system on-board an unmanned Global Hawk also continued. 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. Design for integration of the system on-board an unmanned Global Hawk also continued. This technology will be integrated as part of a UAV-Based Range capability as well. The fabrication and installation of a telemetry capability integrated with a High Altitude, Long Endurance Un-crewed Aerial System (HALE UAS) for a technical demonstration was completed. The system was integrated onto a Global Hawk and was deployed to Hawaii in support of flight testing in the area. Tests were conducted in a hypervelocity shock tunnel on a hollow-cylinder flare test article in order to acquire shock-boundary layer interaction data. Such data will be used to validate computational fluid dynamics (CFD) codes used in the community for hypersonic analyses. The dataset will help advance the state of the art in computational tools.
Document Details
- Document Type
- Accomplishment
- Publication Date
- Oct 01, 2020
- Source ID
- 8ca54a98fcd5a2838502db18e350480b