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Boulder, CO, United States

Agency: National Aeronautics and Space Administration | Branch: | Program: STTR | Phase: Phase I | Award Amount: 99.73K | Year: 2007

We propose here to develop tunable diode laser spectroscopy as a diagnostic for the Space Shuttle main engines during test stand operations. These engines represent the state-of-the-art in rocket engine propulsion systems, and as such, they stretch available technology to the limit. The engines must be test-fired through several cycles prior to incorporation into the shuttle for flight operations. Diagnostic tests for the engines are extremely limited due to the harsh nature of the environment. We propose to develop diode laser instrumentation in order to measure temperature, velocity, surface erosion, and possibly efficiency in real time with an update rate of up to 1 kHz. The system technology will be based on wavelength multiplexed tunable diode laser spectroscopy which Zolo and Stanford have jointly developed to diagnose many types of aeropropulsion systems including SCRAMJETs, augmentors, and pulsed detonation engines. This project represents the first time that the wavelength-multiplexed technology will be tested on full-scale rocket engines.

Grover S.,University of Colorado at Boulder | Dmitriyeva O.,University of Colorado at Boulder | Estes M.J.,Zolo Technologies | Moddel G.,University of Colorado at Boulder
IEEE Transactions on Nanotechnology

We evaluate a technique to improve the performance of antenna-coupled diode rectifiers working in the IR. Efficient operation of conventional, lumped-element rectifiers is limited to the low terahertz. By using femtosecond-fast MIM diodes in a traveling-wave (TW) configuration, we obtain a distributed rectifier with improved bandwidth. This design gives higher detection efficiency due to a good match between the antenna impedance and the geometry-controlled impedance of the TW structure. We have developed a method for calculating the responsivity of the antenna-coupled TW detector. Three TW devices, made from different materials, are simulated to obtain their impedance and responsivity at 1.5, 3, 5, and 10 μm wavelengths. The characteristic impedance of a 100-nm-wide TW is in the range of 50 Ωand has a small variation with frequency. A peak responsivity of 0.086 A/W is obtained for the Nb- Nb 2O 5Nb TW diode at 3-μm wavelength. This corresponds to a quantum efficiency of 3.6% and is a significant improvement over the antenna-coupled lumped-element diode rectifiers. For IR imaging, this results in a normalized detectivity of 4 × 10 6 Jones at 3 μm. We have identified several ways for improving the detectivity of the TW detector. Possible methods include decreasing the diode resistance, reducing the noise, and increasing the effective antenna area. © 2010 IEEE. Source

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 855.31K | Year: 2006

Zolo, in conjunction with researchers from Stanford University, proposes to develop multiplexed tunable diode laser spectroscopic diagnostics to measure combustion parameters in the flame holding region of jet engine augmentors. The proposed system will use wavelength modulation spectroscopy with second harmonic detection in order to measure at least water concentration and temperature inside an operating afterburner. Optical access will be gained via a water-cooled probe currently being developed for the program. The system should be able to measure high-speed combustion instabilities that currently limit augmentor performance. Detection of other species such as CO, CO2, and unburned fuel components such as methane and ethylene will be investigated as well.

Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 99.97K | Year: 2006

Zolo Technologies and Stanford University's High Temperature GasDynamics Lab have teamed to propose the development of wavelength-multiplexed diode laser absorption measurements for a novel environment - the combustion zone of a liquid fueled rocket motor. A number of unique challenges will need to be overcome to enable these measurements. First, the pressure of the measurement zone approaches 100 atmospheres making any spectroscopic measurements difficult to quantify due to pressure broadening. Second, intense scattering of the diagnostic beam is expected from fuel droplets leading to low signal beam transmission. Third, high temperature, high pressure optical access must be engineered which is not expected to be trivial. During Phase I, we intend to show that these obstacles can be surmounted so that a system to measure temperature can be designed, built and tested during Phase II.

A method of absorption spectroscopy to determine a rapidly variable gas parameter. The method includes transmitting light from a synchronization light source to a synchronization detector. The transmitted light is periodically interrupted by a moving mechanical part between the synchronization light source and synchronization detector. The output from the synchronization detector is used to generate a repeating time signal having variable phase delay. This signal is used to control the timing of laser spectroscopy wavelength scans. Multiple spectroscopic scans may be repeated at multiple selected time signal phase delay and the results averaged for each phase. Apparatus for implementing the above methods are also disclosed.

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