Description: Large ground-test facilities, which simulate real flow conditions from subsonic to hypersonic, are used extensively to generate forces and moments as well as surface measurements of test articles required to validate computational tools used to extrapolate wind tunnel data to realistic flight conditions and hardware. The development of fast instrumentation and measurement capabilities that can readily be integrated into the extreme conditions present under such test conditions is one of several major technological challenges associated with the design, building, and operation of these complex test environments. Spatially and temporally resolved measurements of velocity, density and temperature remain significant yet essential challenges in these facilities. Unfortunately, widely available current suite of flow-field probes exhibit varying degrees of intrusiveness, requiring either the physical placement of probes or seeding of foreign particles or gases. The proposed research program described here expands upon our successful Phase-I results and emphasizes the development and application of optical diagnostic approaches referred to as high-repetition-rate (up to 100 kHz) Interferometric Rayleigh scattering (IRS) and 2-D Filtered Rayleigh scattering (FRS), all-optical techniques that allow non-invasive multi-flow-parameter measurements to be made in any environments containing any kind of gases without the need to seed foreign particles or gases. The concepts and ideas proposed range from proof-of-principle demonstration of novel methodologies using 100-kHz-rate burst-mode laser system to measurements in realistic tunnel conditions expected in the current solicitation.

Benefits: The proposed research program will expand upon advanced laser-based, high-data-rate, multi-dimensional, multi-parameter, noninvasive optical diagnostic platforms for NASA ground-test facilities. Such diagnostic capabilities will be a major step forward in design and model validation efforts in subsonic to hypersonic ground-test facilities developing next-generation aerospace vehicles and air-breathing propulsion systems.

The diagnostic toolkit proposed here will be a significant step forward in using cutting-edge laser technology to address a variety of diagnostics challenges in government and industrial applications. A major beneficiary besides NASA would be DoD test facilities developing advanced weapons systems such as supersonic fighter aircrafts, hypersonic vehicles, and high-Mach number reentry vehicles.