Diode Laser-Based Flight Test Instrumentation for Scramjets

The optimization of scramjet engine performance parameters such as combustion efficiency, thrust maximization, reduction in pollutants, minimization of exhaust signatures (for stealth) are essential. Measurements of chemical species and temperature in the scramjet engine during test flight are critical for evaluating engine performance. For a diode laser-based sensor system to be a viable option for measuring chemical species and temperature, a simple, lightweight and compact sensor system is required. This will require substantial reduction in the physical size of the system, reduction in the number of lasers and detectors, innovative optics, and implementation of compact and rugged electronics. In partnership with the University of Michigan under this STTR, Southwest Sciences proposes to develop an in situ, non-intrusive, multi-species capable, lightweight, compact, and rugged sensor system based on diode laser spectroscopy to monitor the exhaust gases of a scramjet. The proposed sensor system incorporates several key technologies which will permit the development of a multi-gas sensor capable of meeting both detection and severe operational constraints. These key technologies include state-of-the-art lasers, wavelength modulation spectroscopy, modulation frequency multiplexing, time-division multiplexing, a two-color photodiode detector, absorption-based thermometry, digital signal processing, an unique supersonic combustion tunnel.