Results for “laser simulation” — Page 15

NASA NTRS1989

Low-speed aerodynamic characteristics of a powered NASP-like configuration in ground effect

Results are presented on the low-speed aerodynamic characteristics of a simplified NASP (for National Aerospace Plane Program)-like configuration, obtained in the NASA-Langley 14-by-22-foot subsonic tunnel. The model consisted of a triangular wedge forebody, a rectangular midsection housing the propulsion simulation system, and a rectangular wedge aftbody; it also included a delta wing, exhaust flow deflectors, and aftbody fences. Flow visualization was obtained by injecting water into the engine simulator inlets and using a laser light sheet to illuminate the resulting exhaust flow. It was found that power-on ground effects for NASP-like configuration can be substantial; these effects can be reduced by increasing the angle-of-attack to the value of the aftbody ramp angle. Power-on lift losses in ground effect increased with increasing thrust, but could be reduced by the addition of a delta wing to the configuration. Power-on lift losses also increased with use of aftbody fences.

Gatlin, Gregory M.↗

NASA NTRS1990

A synopsis of Langley Research Center's lidar effort for the 1986 FIRE IFO

The lidar data obtained by the Langley Aircraft Lidar in October 1986 in Wisconsin is being reduced in a transparent, simple fashion and will be published in its reduced form in a NASA Reference Publication (RP). This reduced data will also be submitted to the FIRE data archives. Some of this reduced data will be presented at the FIRE FSET Workshop to acquaint the science team with the data format to be used in the archive and the upcoming catalog contained in the RP. A new method was utilized in Wisconsin for obtain the depolarization ratio of aerosols. This method involves using a half-wave plate to calibrate the lidar under field conditions. The theory behind this technique will be presented at this workshop as well as some of the lidar calibration results. The lidar calibration will be utilized in interpreting some of the dual polarization lidar data obtained during the IFO in Wisconsin. Some of these data are also discussed. A continuous wave laser lab-type lidar simulator was constructed during the previous year. One of the primary reasons for the construction of the simulator was to attempt dual-polarization lidar-like calibrations under laboratory, rather than field conditions. The data collected by this system was used to experimentally check and thus, inspire confidence in the algorithms being used to interpret the lidar data obtained in the field. A computer program which simulates noisy lidar data was used as a part of this effort in order to obtain some feel for the noise in the inversion parameters as a function of noise in the actual measurements. The lidar simulation will be described in addition to presenting some of the lab-generated calibration data.

Alvarez, Jose M.↗

NASA NTRS1992

Time resolved simulation of lightning by LIP

Results of time-resolved spectra of lightning simulation in air by laser-induced plasma (LIP) are reported. The measured electron temperatures varied from 17,000 +/-1000 K at 600 ns to 12,000 +/-1000 K at 4 microsec after the ignition of the plasma. Electron densities in the plasma varied from (7.0 +/-1.4) x 10 exp 17/cu cm to (9.0 +/-1.8) x 10 exp 16/cu cm for the above times. A comparison of state variables for LIP and natural lightning is presented. Immediately following the ignition, both natural lightning and LIP are found to reach temperatures in excess of 16,000 K and relax to ambient pressure with different rates. They are expected to approach the 2000-4000-K temperature range, which is important to chemical synthesis, in an asymptotically similar fashion.

Jebens, D. S.↗

NASA NTRS1991

The lightcraft project

Rensselaer Polytechnic Institute has been developing a transatmospheric 'Lightcraft' technology which uses beamed laser energy to propel advanced shuttle craft to orbit. In the past several years, Rensselaer students have analyzed the unique combined-cycle Lightcraft engine, designed a small unmanned Lightcraft Technology Demonstrator, and conceptualized larger manned Lightcraft - to name just a few of the interrelated design projects. The 1990-91 class carried out preliminary and detailed design efforts for a one-person 'Mercury' Lightcraft, using computer-aided design and finite-element structural modeling techniques. In addition, they began construction of a 2.6 m-diameter, full-scale engineering prototype mockup. The mockup will be equipped with three robotic legs that 'kneel' for passenger entry and exit. More importantly, the articulated tripod gear is crucial for accurately pointing at, and tracking the laser relay mirrors, a maneuver that must be performed just prior to liftoff. Also accomplished were further design improvements on a 6-inch-diameter Lightcraft model (for testing in RPI's hypersonic tunnel), and new laser propulsion experiments. The resultant experimental data will be used to calibrate Computational Fluid Dynamic (CFD) codes and analytical laser propulsion models that can simulate vehicle/engine flight conditions along a transatmospheric boost trajectory. These efforts will enable the prediction of distributed aerodynamic and thruster loads over the entire full-scale spacecraft.

Messitt, Don G.↗

NASA NTRS2005

Processing and Synthesis of Pre-Biotic Chemicals in Hypervelocity Impacts

Hypervelocity impacts (HVIs) may have played a significant role in establishing the initial organic inventory for pre-biotic chemistry on the Earth and other planetary bodies. In addition to the delivery of organic compounds intact to planetary surfaces, generally at velocities below approx.20 km/s, HVIs also enable synthesis of new molecules. The cooling post-impact plasma plumes of HVIs in the interstellar medium (ISM), the protosolar nebula (PSN), and the early solar system comprise pervasive conditions for organic synthesis. Such plasma synthesis (PS) can operate over many length scales (from nm-scale dust to planets) and energy scales (from molecular rearrangement to atomization and recondensation). HVI experiments with the flexibility to probe the highest velocities and distinguish synthetic routes are a high priority to understand the relevance of PS to exobiology. We describe here recent studies of PS at small spatial scales and extremely high velocities with pulsed laser ablation (PLA). PLA can simulate the extreme plasma conditions generated in impacts of dust particles at speeds of up to 100 km/s or more. When applied to carbonaceous solids, new and pre-biotically relevant molecular species are formed with high efficiency [1,2].

Brickerhoff, W. B.↗

NASA NTRS2005

A Chemical Model of Micrometeorite Impact into Olivine

Laboratory simulations of space weathering using laser irradiation have been successful in reproducing space weathering characteristics such as the reduction of olivine to form nanophase iron particles. However, the chemistry of the reduction of Fe2+ in olivine to Fe metal has not been fully explored. We present a thermodynamic model of olivine undergoing post-impact cooling and decompression.

Sheffer, A. A.↗

NASA NTRS2007

The Development of Erosion and Impact Resistant Turbine Airfoil Thermal Barrier Coatings

Thermal barrier coatings are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments and extend component lifetimes. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Advanced erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the doped thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion and impact damage mechanisms of the thermal barrier coatings will also be discussed.

Zhu, Dongming↗

NASA NTRS2008

Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions (Invited paper)

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

Zhu, Dongming↗

NASA NTRS2010

Simulation Studies for a Space-Based CO2 Lidar Mission

We report results of initial space mission simulation studies for a laser-based, atmospheric CO2 sounder, which are based on real-time carbon cycle process modelling and data analysis. The mission concept corresponds to the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) recommended by the US National Academy of Sciences' Decadal Survey. As a pre-requisite for meaningful quantitative evaluation, we employ a CO2 model that has representative spatial and temporal gradients across a wide range of scales. In addition, a relatively complete description of the atmospheric and surface state is obtained from meteorological data assimilation and satellite measurements. We use radiative transfer calculations, an instrument model with representative errors and a simple retrieval approach to quantify errors in 'measured' CO2 distributions, which are a function of mission and instrument design specifications along with the atmospheric/surface state. Uncertainty estimates based on the current instrument design point indicate that a CO2 laser sounder can provide data consistent with ASCENDS requirements and will significantly enhance our ability to address carbon cycle science questions. Test of a dawn/dusk orbit deployment, however, shows that diurnal differences in CO2 column abundance, indicative of plant photosynthesis and respiration fluxes, will be difficult to detect

Kawa, S. R.↗

NASA NTRS2008

Advanced Low Conductivity Thermal Barrier Coatings: Performance and Future Directions

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future engine higher fuel efficiency and lower emission goals. In this presentation, thermal barrier coating development considerations and performance will be emphasized. Advanced thermal barrier coatings have been developed using a multi-component defect clustering approach, and shown to have improved thermal stability and lower conductivity. The coating systems have been demonstrated for high temperature combustor applications. For thermal barrier coatings designed for turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability. Erosion resistant thermal barrier coatings are being developed, with a current emphasis on the toughness improvements using a combined rare earth- and transition metal-oxide doping approach. The performance of the toughened thermal barrier coatings has been evaluated in burner rig and laser heat-flux rig simulated engine erosion and thermal gradient environments. The results have shown that the coating composition optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic durability. The erosion, impact and high heat-flux damage mechanisms of the thermal barrier coatings will also be described.

Zhu, Dongming↗

NASA NTRS2013

Determination of Local Slope on the Greenland Ice Sheet Using a Multibeam Photon-Counting Lidar in Preparation for the ICESat-2 Mission

The greatest changes in elevation in Greenland and Antarctica are happening along the margins of the ice sheets where the surface frequently has significant slopes. For this reason, the upcoming Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission utilizes pairs of laser altimeter beams that are perpendicular to the flight direction in order to extract slope information in addition to elevation. The Multiple Altimeter Beam Experimental Lidar (MABEL) is a high-altitude airborne laser altimeter designed as a simulator for ICESat-2. The MABEL design uses multiple beams at fixed angles and allows for local slope determination. Here, we present local slopes as determined by MABEL and compare them to those determined by the Airborne Topographic Mapper (ATM) over the same flight lines in Greenland. We make these comparisons with consideration for the planned ICESat-2 beam geometry. Results indicate that the mean slope residuals between MABEL and ATM remain small (< 0.05 degrees) through a wide range of localized slopes using ICESat-2 beam geometry. Furthermore, when MABEL data are subsampled by a factor of 4 to mimic the planned ICESat-2 transmit-energy configuration, the results are indistinguishable from the full-data-rate analysis. Results from MABEL suggest that ICESat-2 beam geometry and transmit-energy configuration are appropriate for the determination of slope on approx. 90-m spatial scales, a measurement that will be fundamental to deconvolving the effects of surface slope from the ice-sheet surface change derived from ICESat-2.

Photon-Counting↗

NASA NTRS2014

Determination of Local Slope on the Greenland Ice Sheet Using a Multibeam Photon-Counting Lidar in Preparation for the ICESat-2 Mission

The greatest changes in elevation in Greenland and Antarctica are happening along the margins of the ice sheets where the surface frequently has significant slopes. For this reason, the upcoming Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) mission utilizes pairs of laser altimeter beams that are perpendicular to the flight direction in order to extract slope information in addition to elevation. The Multiple Altimeter Beam Experimental Lidar (MABEL) is a high-altitude airborne laser altimeter designed as a simulator for ICESat-2. The MABEL design uses multiple beams at fixed angles and allows for local slope determination. Here, we present local slopes as determined by MABEL and compare them to those determined by the Airborne Topographic Mapper (ATM) over the same flight lines in Greenland. We make these comparisons with consideration for the planned ICESat-2 beam geometry. Results indicate that the mean slope residuals between MABEL and ATM remain small (< 0.05◦) through a wide range of localized slopes using ICESat-2 beam geometry. Furthermore, when MABEL data are subsampled by a factor of 4 to mimic the planned ICESat-2 transmit-energy configuration, the results are indistinguishable from the full-data-rate analysis. Results from MABEL suggest that ICESat-2 beam geometry and transmit-energy configuration are appropriate for the determination of slope on ∼90-m spatial scales, a measurement that will be fundamental to deconvolving the effects of surface slope from the ice-sheet surface change derived from ICESat-2.

Greenland↗

NASA NTRS2017

Combustion Joining of Regolith Tiles for In-Situ Fabrication of Launch/Landing Pads on the Moon and Mars

To mitigate dust problems during launch-landing operations in lunar and Mars missions, it is desired to build solid pads on the surface. Recently, strong tiles have been fabricated from lunar regolith simulants using high-temperature sintering. The present work investigates combustion joining of these tiles through the use of exothermic intermetallic reactions. Specifically, nickel aluminum (1:1 mole ratio) mixture was placed in a gap between the tiles sintered from JSC-1A lunar regolith simulant. Upon ignition by a laser, a self-sustained propagation of the combustion front over the mixture occurred. Joining was improved with increasing the tile thickness from 6.3 mm to 12.7 mm. The temperatures sufficient for melting the glass phase of JSC-1A were recorded for 12.7-mm tiles, which explains the observed better joining.

Ferguson, Robert E.↗

NASA NTRS2017

Combustion Joining of Regolith Tiles for In-Situ Fabrication of Launch/Landing Pads on the Moon and Mars

To mitigate dust problems during launch/landing operations in lunar and Mars missions, it is desired to build solid pads on the surface. Recently, strong tiles have been fabricated from lunar regolith simulants using high-temperature sintering. The present work investigates combustion joining of these tiles through the use of exothermic intermetallic reactions. Specifically, nickel/aluminum (1:1 mole ratio) mixture was placed in a gap between the tiles sintered from JSC-1A lunar regolith simulant. Upon ignition by a laser, a self-sustained propagation of the combustion front over the mixture occurred. Joining was improved with increasing the tile thickness from 6.3 mm to 12.7 mm. The temperatures sufficient for melting the glass phase of JSC-1A were recorded for 12.7-mm tiles, which explains the observed better joining.

Ferguson, Robert E.↗

NASA NTRSDate not supplied

Analysis of the Amplitude Response of a Two-Point and a Multi-Point Focused Laser Differential Interferometer

Experiments were performed with two different focused laser differential interferometer (FLDI) instruments to assess the relative amplitude response of each instrument to a traveling shockwave generated by a laser spark in air. The first FLDI instrument generated two slightly-separated measurement points, with each measurement point providing sensitivity to density fluctuations induced by the shockwave. By performing a cross-correlation between the signals obtained from each measurement point, the phase velocity of density fluctuations can be obtained. The second FLDI instrument generated a measurement line that was oriented parallel to the shockwave direction of travel with the resulting interference pattern sampled at multiple equally-spaced points along the line. As a result, this instrument provides density fluctuation measurement capability at multiple points simultaneously. When the measurement line is oriented parallel to the shockwave direction of travel, the phase velocity, rate of change of the phase velocity, and acceleration of density fluctuations traveling along each line can be obtained by performing a cross-correlation between points along the line. Numerical computations of the shockwave generated by the laser spark are used to simulate the response of each instrument and are compared to the experimental results. High-speed schlieren imaging has also been performed and is compared with the FLDI measurements and computational results.

Brett F. Bathel↗

NASA NTRSDate not supplied

Analysis of the Amplitude Response of a Two-Point and a Multi-Point Focused Laser Differential Interferometer

Experiments were performed with two different focused laser differential interferometer (FLDI) instruments to assess the relative amplitude response of each instrument to a traveling shockwave generated by a laser spark in air. The first FLDI instrument generated two slightly-separated measurement points, with each measurement point providing sensitivity to density fluctuations induced by the shockwave. By performing a cross-correlation between the signals obtained from each measurement point, the phase velocity of density fluctuations can be obtained. The second FLDI instrument generated a measurement line that was oriented parallel to the shockwave direction of travel with the resulting interference pattern sampled at multiple equally-spaced points along the line. As a result, this instrument provides density fluctuation measurement capability at multiple points simultaneously. When the measurement line is oriented parallel to the shockwave direction of travel, the phase velocity, rate of change of the phase velocity, and acceleration of density fluctuations traveling along each line can be obtained by performing a cross-correlation between points along the line. Numerical computations of the shockwave generated by the laser spark are used to simulate the response of each instrument and are compared to the experimental results. High-speed schlieren imaging has also been performed and is compared with the FLDI measurements and computational results.

Interferometry↗

NASA NTRS2023

Users' Guide to Vinci: Personal Computer Software for Planning Image-based Measurements in Wind Tunnels

Vinci is software that can be used to plan image-based measurements in wind tunnels. It allows the user to plan the placement of cameras and the choice of lenses well in advance of a test, thereby reducing the set-up time and cost when tunnel occupancy begins. It can also be used post-test to display data (pressure-sensitive paint, particle image velocimetry, model deformation) in context with the test article. Vinci is self-contained and runs on personal computers under Windows operating systems. No other software is required. Test articles are represented by CFD-like surface grids that may be read from an external file or created within the program as a combination of simple geometric shapes. The user controls the position and orientation of the test article through a Graphical User Interface (GUI) and may add many additional objects, including tunnel walls and windows, a wide variety of simple geometric shapes, mirrors, lamps, and laser sheets. The application computes simulated images from up to 40 cameras. Images are based on pinhole projection. Each camera is defined by the sensor size and the focal length of the lens. All camera parameters, including position and point angles, are controlled through the GUI. Simulated images are displayed in a window of the GUI and may be saved as bitmaps.

Users’ Guide, Image Planning, Wind Tunnels, Softwa↗

NASA NTRS1986

Direct solar-pumped iodine laser amplifier

In order to evaluate the feasibility of the solar pumped dye laser, the parametric study of a dye laser amplifier pumped by a solar simulator and flashlamp was carried out, and the amplifier gains were measured at various pump beam irradiances on the dye cell. Rhodamine 6G was considered as a candidate for the solar pumped laser because of its good utilization of the solar spectrum and high quantum efficiency. The measurement shows that a solar concentration of 20,000 is required to reach the threshold of the dye. The work to construct a kinetic model algorithm which predicts the output parameter of laser was progressed. The kinetic model was improved such that there is good agreement between the theoretical model and experimental data for the systems defined previously as flashlamp pumped laser oscillator, and the long path length solar pumped laser.

Han, Kwang S.↗