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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Carbon Dioxide Active Remote Sensing Using Pulsed 2-µm Lidar

A pulsed 2-µm Integrate Path Differential Absorption (IPDA) lidar was developed at NASA Langley Research Center for high-accuracy and high-precision measurements of atmospheric carbon dioxide (CO 2 ). The instrument targets the R30 CO 2 absorption line and implements high-energy tunable on-line transmitter and advanced HgCdTe avalanche photodiode receiver. During 2019 airborne validation campaign, the IPDA was tested over the ocean for retrieving the weighted-average column dry-air volume mixing ratio of CO 2 (XCO 2 ) from 4.5 km altitude. XCO 2 measurement resulted in 404.43 ± 1.23 ppm using 10 s average, as compared to 405.49 ppm from prediction models. This translates to 0.26% and 0.30% relative accuracy and precision, respectively. Performance models were updated to scale the IPDA technology assuming operation from space platform. Results present XCO 2 measurements using the instrument capabilities considering different target scenarios for Earth’s surface. This demonstrates the potential for the IPDA technique and technology to achieve sustained global CO 2 measurement.

Active Remote Sensing↗
NASA NTRSDate not supplied

Carbon Dioxide Active Remote Sensing Using Pulsed 2-µm Lidar

A pulsed 2-µm Integrate Path Differential Absorption (IPDA) lidar was developed at NASA Langley Research Center for high-accuracy and high-precision measurements of atmospheric carbon dioxide (CO 2 ). The instrument targets the R30 CO 2 absorption line and implements high-energy tunable on-line transmitter and advanced HgCdTe avalanche photodiode receiver. During 2019 airborne validation campaign, the IPDA was tested over the ocean for retrieving the weighted-average column dry-air volume mixing ratio of CO 2 (XCO 2 ) from 4.5 km altitude. XCO 2 measurement resulted in 404.43 ± 1.23 ppm using 10 s average, as compared to 405.49 ppm from prediction models. This translates to 0.26% and 0.30% relative accuracy and precision, respectively. Performance models were updated to scale the IPDA technology assuming operation from space platform. Results present XCO 2 measurements using the instrument capabilities considering different target scenarios for Earth’s surface. This demonstrates the potential for the IPDA technique and technology to achieve sustained global CO 2 measurement.

Active Remote Sensing↗
NASA NTRS2006

Reducing Propulsion Airframe Aeroacoustic Interactions with Uniquely Tailored Chevrons: Isolated Nozzles - 1.

The flow/acoustic environment surrounding an engine nozzle installed on an airplane, say, under the wing, is asymmetric due to the pylon, the wing and the interaction of the exhaust jet with flaps on the wing. However, the conventional chevrons, which are azimuthally uniform serrations on the nozzle lip, do not exploit the asymmetry due to these propulsion airframe aeroacoustic interactions to reduce jet noise. In this pioneering study we use this non-axisymmetry to our advantage and examine if the total jet-related noise radiated to the ground can be reduced by using different types of azimuthally varying chevrons (AVC) which vary the mixing around the nozzle periphery. Several scale models of the isolated nozzle, representative of high bypass ratio engine nozzles, were made with a pylon and azimuthally varying chevrons on both fan and core nozzles to enhance mixing at the top (near the pylon) with less mixing at the bottom (away from the pylon) or vice versa. Various combinations of fan and core AVC nozzles were systematically tested at typical take-off conditions inside a free jet wind-tunnel and, here, in Part 1 we analyze the acoustics results for the isolated nozzle with a pylon, with installation effects reported in Parts 2 and 3. Several interesting results are discovered: amongst the fan AVCs the top-enhanced mixing T-fan chevron nozzle is quieter in combination with any core AVC nozzle when compared to conventional chevrons; however, the bottom-mixing B-fan chevrons, as well as the core AVC nozzles, by themselves, are noisier. Further, the low-frequency source strengths in the jet plume, obtained via phased microphone arrays, also corroborate the far field sound, and for the T-fan chevrons such sources move further downstream than those for baseline or conventional chevron nozzles.

Mengle, Vinod G.↗
NASA NTRS1992

NASP - Focus on technology

The major changes in the NASP program caused mostly by budget pressures are described and current technology developments are highlighted. Particular attention is given to the program funding, vehicle and engine design, and the technology program. It is concluded that the success of the X-30 vehicle design depends on the success of the technology development effort. The major accomplishments of the NASP technology program include the T-5 Shock Tunnel at California Institute of Technology and Mach 16 injection and mixing experiments conducted in this facility; the low speed component integration rig which provide data on engine operation from static conditions to Mach 3.5; the module to module interaction test which provided data on the effects of inlet unstart in one engine module on an adjacent module at Mach 4.3; and the direct-connect module used for fuel injection and mixing studies at Mach 6-8.

Waldman, Barry J.↗
NASA NTRSDate not supplied

Evaluating Meteorological Dust Events and Machine-Learning Based Dust Identification in Geostationary Satellite Imagery

NASA scientists in the Short-term Prediction Research and Transition Center (SPoRT) developed a physically-based machine learning approach to identify dust in satellite imagery with a focus on night-time dust detection (Berndt et al. 201; DustTracker-AI). NASA/NOAA Geostationary Environmental Operational Satellite-16 (GOES-16) imagery was used for training and model inputs. The training, testing and validation data set consists of 28 events in the Southwest United States, capturing dust and null events in the region from 2018-2020.With 83 distinct images and millions of pixels a random forest model was trained and validated, correctly labeling 85% of dust pixels.For the first time, the model was run in near-real time production during the spring of 2022 and dust probability visualizations were made available to NOAA National Weather Service (NWS) forecasters to assess its utility for dust forecasting. Results indicated the model helped increase the confidence in the presence of dust and enabled dust tracking for a longer period of time into the night-time hours. Forecaster assessment and running the model in near real-time allowed for the team to determine the types of events missed, captured, and false alarms. To gain additional context on model performance,the SPoRT team sought to gather more detailed information on the training database(e.g., meteorological characteristics and drivers). The goal of this project was to identify the meteorological drivers for the dust events and create a database which synthesized information from observations, forecaster discussions, and analyses pertaining to the dust events to understand the types of events currently used to train the model. A more detailed meteorological synopsis was created for each dust event in the training, testing, and validation datasets. Following the completion of the database and documentation, the classification details revealed that 88% of the dust events were synoptically driven while mesoscale events were less prevalent in model datasets. Meteorological conditions found such as mixing layer depth and wind velocity had mean values of 645mb and 21kt respectively.With conditions of deep mixed layers and moderate to strong surface winds a mesoscale thunderstorm outflow event was considered and subsequently added to the model training data set to test the impact of additional mesoscale training data. The model was retrained and then qualitatively tested on a sample thunderstorm outflow case that the original model was unable to identify. Preliminary results showed potential that the addition of more mesoscale events included in the training data could help to better identify indistinct and localized dust events.

Connor Welch↗
NASA NTRS1995

CFD assessment of the pollutant environment from RD-170 propulsion system testing

Computational Fluid Dynamics (CFD) technology has been used to assess the exhaust plume pollutant environment of the RD-170 engine hot-firing on the F1 Test Stand at Marshall Space Flight Center. Researchers know that rocket engine hot-firing has the potential for forming thermal nitric oxides (NO(x)), as well as producing carbon monoxide (CO) when hydrocarbon fuels are used. Because of the complicated physics involved, however, little attempt has been made to predict the pollutant emissions from ground-based engine testing, except for simplified methods which can grossly underpredict and/or overpredict the pollutant formations in a test environment. The objective of this work, therefore, has been to develop a technology using CFD to describe the underlying pollutant emission physics from ground-based rocket engine testing. This resultant technology is based on a three-dimensional (3D), viscous flow, pressure-based CFD formulation, where wet CO and thermal NO finite-rate chemistry mechanisms are solved with a Penalty Function method. A nominal hot-firing of a RD-170 engine on the F1 stand has been computed. Pertinent test stand flow physics such as the multiple-nozzle clustered engine plume interaction, air aspiration from base and aspirator, plume mixing with entrained air that resulted in contaminant dilution and afterburning, counter-afterburning due to flame bucket water-quenching, plume impingement on the flame bucket, and restricted multiple-plume expansion and turning have been captured. The predicted total emission rates compared reasonably well with those of the existing hydrocarbon engine hot-firing test data.

Wang, Ten-See↗
DOE OSTI2022

Hanford Low-Activity Waste Glass Minor Component Concentration Boundary Expansion

This study investigated the effects of increasing concentrations of minor components on simulated Hanford low-activity waste (LAW) glass properties to allow for LAW glass composition envelope expansion. A test matrix of ten glasses was generated by spiking three previously studied simulated Hanford LAW glass compositions with increasing concentrations of minor component mixes up to a total concentration of 2 wt%. In this study, the ten glasses were fabricated, and key properties were measured including crystal formation after canister centerline cooling (CCC), crystallinity as a function of temperature, density, viscosity, electrical conductivity, glass durability using the Vapor Hydration Test (VHT), product consistency using the Product Consistency Test (PCT), and sulfur solubility. The data from these tests are presented in this report.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2000

Acoustic and Aerothermal Performance Test of the Axisymmetric Coannular Ejector Nozzle: Acoustic Performance - Volume 2

Acoustic and propulsion performance testing of a model-scale Axisymmetric Coannular Ejector nozzle was conducted in the Boeing Low-speed Aeroacoustic Facility. This nozzle is a plug nozzle with an ejector design to provide aspiration of about 20% of the engine flow. A variety of mixing enhancers were designed to promote mixing of the engine and the aspirated flows. These included delta tabs, tone-injection rods, and wheeler ramps. This report addresses the acoustic aspects of the testing. The spectral characteristics of the various configurations of the nozzle are examined on a model-scale basis. This includes indentifying particular noise sources contributing to the spectra and the data are projected to full-scale flyover conditions to evaluate the effectiveness of the nozzle, and of the various mixing enhancers, on reducing the Effective Perceived Noise Levels.

Herkes, William↗
NASA NTRS2006

Explosive Event in MON-3 Oxidizer System Resulting from Pressure Transducer Failure

In 2003, a Druck(Registered Trademark) pressure transducer failed catastrophically in a test system circulating nitrogen tetroxide at NASA Johnson Space Center White Sands Test Facility. The cause of the explosion was not immediately obvious since the wetted areas of the pressure transducer were constructed of materials compatible with nitrogen tetroxide. Chemical analysis of the resulting residue and a materials analysis of the diaphragm and its weld zones were used to determine the chain of events that led to the catastrophic failure. Due to excessive dynamic pressure loading in the test system, the diaphragm in the pressure transducer suffered cyclic failure and allowed the silicon oil located behind the isolation diaphragm to mix with the nitrogen tetroxide. The reaction between these two chemicals formed a combination of 2,4-di and 2,4,6-trinitrophenol, which are shock sensitive explosives that caused the failure of the pressure transducer. Further research indicated numerous manufacturers offer similar pressure transducers with silicone oil separated from the test fluid by a thin stainless steel isolation diaphragm. Caution must be exercised when purchasing a pressure transducer for a particular system to avoid costly failures and test system contamination.

Baker, David L.↗
NASA NTRS1986

Enhanced mixing of an axisymmetric jet by aerodynamic excitation

The main objective of acoustic excitation studies is to gain a high level of control over processes governing free shear flow characteristics. The basic premise is that inherent instability waves in free shear flows are excitable by external perturbations with frequencies close to the natural instability frequency of the flow. An 8.89 cm diameter axisymmetric jet was acoustically excited by four loudspeakers placed upstream of the nozzle exit. Measurements were made at Mach numbers of 0.435 and 0.2. A single hot-wire probe was used to obtain turbulence levels at the nozzle exit and along the centerline, and a microphone at the nozzle exit was used to study the resonance characteristics of the rig. A Pitot probe was stationed at X/D = 9 downstream along the nozzle axis to study the Strouhal number dependence and to look at threshold levels for excitation. The test results were obtained after a preliminary evaluation and facility improvement. Excitation at the correct Strouhal number enhanced mixing significantly. The effects were most prominent in the Strouhal number range between 0.4 and 1.0. The effects of acoustic excitation also depend considerably on the sound pressure level at the nozzle exit and were more pronounced at higher sound levels. Other factors which influenced the excitability were valve noise, exit turbulence levels, extraneous noise, and a flanged nozzle. Analysis of the hot-wire signal, in conditions of optimum jet mixing, showed vortex pairing to occur between 2 and 3 diameters downstream.

Raman, Ganesh↗
DOE OSTI2022

Improving Ni-Based SOFC Anode Resilience and Durability through Secondary Phase Formation

The project used a multi-disciplinary approach to test test if 2° materials, added to traditional cermet components, enhanced SOFC mechanical strength, anode resilience and durability when subjected to electrochemical and environmental redox cycling. Findings from fracture testing, electrochemical studies and operando Raman spectroscopy measurements demonstrated that aluminum titanate (Al 2 TiO 5 or ALT) mechanically mixed with NiO-YSZ cermets confers superior mechanical strength and slower degradation rates under polarization. No deleterious effects from ALT in conversion efficiency were observed. Specific accomplishments included the following: (1) Refined methods used to fabricate ALT enhanced anodes into bi-layer anode supports to achieve high power densities; (2) Compared the effects of adding ALT mechanically to Ni-YSZ powders prior to anode fabrication with adding ALT through infiltration and co-infiltration of YSZ scaffolds; (3) Tested the resilience of these novel materials to electrochemical and environmental redox cycling and thermal stresses commonly encountered in functioning SOFCs; and (4) Characterized the ability of ALT to improve the carbon tolerance of Ni-YSZ anodes operating with dry methane.

01 COAL, LIGNITE, AND PEAT↗
NASA NTRS2017

GEER Status Update

History: The Glenn Extreme Environments Rig (GEER) first became operational in the early part of 2015. Since that time GEER has completed a number of scientific tests and has undergone improvements in the chemical delivery system and analytics following a year of operations experience. Recent Updates: In June 2016, the GEER process system was rebuilt to provide a more robust system, higher accuracy and new capabilities. New insulation was installed on the exterior of the pressure vessel and gas lines. The newly revamped GEER plumbing system can provide extremely precise custom gas mixtures using any gas desired by the investigator in any combination. GEER can heat the resulting mixture up to 500 deg C and 1500 psia. The 304 stainless steel vessel walls were polished to reduce corrosion rate and reduce unwanted chemical reactions. The process lines were replaced with high purity Sulfinert coated tubing. The GEER team added the ability to individually boost specialty gases to GEER thus allowing operators to make very precise changes to the gas chemistry inside of GEER during a test while at high temperature and pressure. High accuracy mass flow meters were added to further improve gas mixing accuracy and precision. An in-line, integrated Inficon MicroGC Fusion was added for real time gas analysis along with a high purity gas sampling system, providing fully automated, real time analysis of the gas chemistry inside of GEER in minutes. This complements a co-located mass spectrometer and both are used for regular monitoring of the vessel chemistry. All internal vessel components were replaced with polished 304SS equivalents. Hot vent down capability was increased. Finally, an automated liquid injection system was added and is rated for max vessel operating conditions of (1500 psia, 500 C). Recent Results and Publications: In May 2016, GEER completed a test that exposed high temperature electronics to Venus surface conditions for 21.5 days. This demonstrated the potential for operating robotic spacecraft in the Venus environment without the need for thermal or environmental protection. Results from this test were published in December 2016 and received national media attention. In April 2017 GEER implemented an 80 day test at Venus surface conditions to simulate chemical weathering of expected Venus minerals. This test supported a ROSES award to a team led by Prof. Ralph Harvey of Case Western Reserve University. The test concluded in July 2017 and nearly doubled previous operation record of 42 days at Venus surface conditions. Preliminary results of these and previous experiments were presented at the recent Venus Modeling Workshop. In June 2017, NASA TM2017-219437 "Chemical and Microstructural Changes in Metallic and Ceramic Materials Exposed to Venusian Surface Conditions" was published. This report provides an extensive and valuable resource detailing the behavior of a variety of engineering materials at Venus surface conditions. Community Involvement: An external science advisory panel has been formed.

Kremic, Tibor↗
NASA NTRS2001

Source Identification and Location Techniques

Mr. Weir presented source location results obtained from an engine test as part of the Engine Validation of Noise Reduction Concepts program. Two types of microphone arrays were used in this program to determine the jet noise source distribution for the exhaust from a 4.3 bypass ratio turbofan engine. One was a linear array of 16 microphones located on a 25 ft. sideline and the other was a 103 microphone 3-D "cage" array in the near field of the jet. Data were obtained from a baseline nozzle and from numerous nozzle configuration using chevrons and/or tabs to reduce the jet noise. Mr. Weir presented data from two configurations: the baseline nozzle and a nozzle configuration with chevrons on both the core and bypass nozzles. This chevron configuration had achieved a jet noise reduction of 4 EPNdB in small scale tests conducted at the Glenn Research Center. IR imaging showed that the chevrons produced significant improvements in mixing and greatly reduced the length of the jet potential core. Comparison of source location data from the 1-D phased array showed a shift of the noise sources towards the nozzle and clear reductions of the sources due to the noise reduction devices. Data from the 3-D array showed a single source at a frequency of 125 Hz. located several diameters downstream from the nozzle exit. At 250 and 400 Hz., multiple sources, periodically spaced, appeared to exist downstream of the nozzle. The trend of source location moving toward the nozzle exit with increasing frequency was also observed. The 3-D array data also showed a reduction in source strength with the addition of chevrons. The overall trend of source location with frequency was compared for the two arrays and with classical experience. Similar trends were observed. Although overall trends with frequency and addition of suppression devices were consistent between the data from the 1-D and the 3-D arrays, a comparison of the details of the inferred source locations did show differences. A flight test is planned to determine if the hardware tested statically will achieve similar reductions in flight.

Weir, Donald↗
DOE OSTI2020

Characterization of mechanical properties and deformation behavior of highly irradiated 316L stainless steel from target modules at the Spallation Neutron Source using digital image correlation analysis

Tensile specimens with irradiation doses ranging from approximately 0.7 to 7.6 displacements per atom (dpa) were fabricated from 316L samples removed from Spallation Neutron Source (SNS) target vessels after service. Tensile tests were performed in conjunction with digital image correlation (DIC) characterization, which permitted detailed analysis of the strain distribution and deformation behavior of the specimen gauge sections during testing. The results show, while considerable hardening (500–700 MPa increase in yield strength) occurred in the 316L SNS target material with increasing dose, appreciable ductility (19–23% total elongation) remained in the material after irradiation to 7.6 dpa in the mixed neutron/proton environment of the SNS target region. The DIC data showed the strain distribution and deformation behavior of all irradiated specimens were nonuniform during testing. Strain localization in the form of deformation bands or “hotspots” was observed during testing, and in some specimens, the bands propagated as deformation waves along the gauge section. The “traveling wave” deformation behavior affected the amount of elongation each specimen achieved, and the scatter in the elongation data was attributed to the large variation in deformation behavior observed among different specimens. Bands of localized strain, or deformation bands, oriented at specific angles were observed in two-dimensional plots of the strain distribution in the gauge sections of some specimens. Overall, this paper describes the experimental procedures, results, and deformation behavior of tensile specimens from SNS targets after service and illustrates the value of DIC characterization during tensile testing of irradiated materials.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Machine learning assisted bayesian inference of mix and hot-spot conditions in NIF implosions

Experiments on the National Ignition Facility (NIF) have provided clear evidence of ablator material mixing into the Hot-Spot, leading to degraded performance. However, inferring the amount of mix and Hot-Spot conditions from typical experimental observations (e.g. x-ray spectra and images) is highly challenging. Here, we have developed an analysis method that utilizes machine learning assisted Bayesian inference to find the probability distributions of the Hot-Spot and mix conditions. This approach uses a neural network, trained on an idealized 2-dimensional representation of the Hot-Spot and mix distribution, and Bayesian inference to find the statistical distributions of Hot-Spot conditions that provide a match with observations. We have tested this method with synthetic data from simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Impact of Mixed Traffic on the Energy Savings of a Truck Platoon

A two-truck platoon based on a prototype cooperative adaptive cruise control (CACC) system was tested on a closed test track in a variety of realistic traffic and transient operating scenarios - conditions that truck platoons are likely to face on real highways. The fuel consumption for both trucks in the platoon was measured using the SAE J1321 gravimetric procedure as well as calibrated J1939 instantaneous fuel rate, serving as proxies to evaluate the impact of aerodynamic drag reduction under constant-speed conditions. These measurements demonstrate the effects of: the presence of a multiple-passenger-vehicle pattern ahead of and adjacent to the platoon, cut-in and cut-out manoeuvres by other vehicles, transient traffic, the use of mismatched platooned vehicles (van trailer mixed with flatbed trailer), and the platoon following another truck with adaptive cruise control (ACC). These scenarios are intended to address the possibility of “background aerodynamic platooning” impacting realized savings on public roads. Using calibrated J1939 fuel rate analysis, fuel savings for curved track sections versus straight track sections were also evaluated for these scenarios, highlighting differences in the implementation of the CACC control strategies compared to a stock ACC implementation. The use of different trailer types and the presence of passenger-vehicle traffic patterns showed a measurable impact on platoon performance in some conditions, but the basic fuel savings trends were retained.

adaptive cruise control↗
NASA NTRS2001

Fatigue Life Methodology for Bonded Composite Skin/Stringer Configurations

A methodology is presented for determining the fatigue life of composite structures based on fatigue characterization data and geometric nonlinear finite element (FE) analyses. To demonstrate the approach, predicted results were compared to fatigue tests performed on specimens which represented a tapered composite flange bonded onto a composite skin. In a first step, tension tests were performed to evaluate the debonding mechanisms between the flange and the skin. In a second step, a 2D FE model was developed to analyze the tests. To predict matrix cracking onset, the relationship between the tension load and the maximum principal stresses transverse to the fiber direction was determined through FE analysis. Transverse tension fatigue life data were used to -enerate an onset fatigue life P-N curve for matrix cracking. The resulting prediction was in good agreement with data from the fatigue tests. In a third step, a fracture mechanics approach based on FE analysis was used to determine the relationship between the tension load and the critical energy release rate. Mixed mode energy release rate fatigue life data were used to create a fatigue life onset G-N curve for delamination. The resulting prediction was in good agreement with data from the fatigue tests. Further, the prediction curve for cumulative life to failure was generated from the previous onset fatigue life curves. The results showed that the methodology offers a significant potential to Predict cumulative fatigue life of composite structures.

Krueger, Ronald↗
NASA NTRS1991

No-vent fill pressurization tests using a cryogen simulant

The results are described of an experimental program which studied the performance of various no-vent fill techniques for tank-to-tank liquid transfer. The tests were performed using a cryogen simulant (Freon-114) and a test bed consisting of a multiple tank/plumbing network that enabled studies of a variety of different inlet flow and active mixing regimes. Several results and conclusions were drawn from the 26 transfer experiments comprising the program. Most notable was the significant improvement in fill performance (i.e., minimized fill time and maximized fill fraction) with increased agitation of the liquid surface. Another was the close correlation between measured condensation rates and those predicted by recent theories which express condensation as a function of turbulent eddy effects on the liquid surface. In most cases, test data exhibited strong agreement with an analytical model which accounts for tank heat transfer and thermodynamics in a 1 g environment.

Schmidt, G. R.↗