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NASA NTRS2020

X-HAB 2020: AR Field Treks Summary and Conclusions

As part of the FY20 X-Hab Challenge, BLiSS sought to create an Augmented Reality (AR) toolkit to help with analog field trek operations under the supervision of the Solar System Exploration Research Virtual Institute (SSERVI). These treks are operational and technical demonstrations at space-like destinations on Earth to test current extra-vehicular activity (EVA) techniques. While BLiSS as an organization has experience studying operational tasks such as this, it has never developed AR software at this scale. For that reason, another team at the University was brought on to work in parallel. The Collaborative Lab for Advancing Work in Space (CLAWS) is a veteran group of the NASA Spacesuit User Interface Technologies for Students (SUITS) challenge in which Hololens displays for astronauts are created within a year. The operational and technological pairing was ideally suited for tackling this problem. The team divided its responsibilities so that BLiSS would handle the research required to shape the project. As this deliverable had an end user, it was decided that interviewing these field geologists and operations specialists would provide the best insight. These interviews paired with literature review would reveal niche applications for AR that remained within feasible bounds. These science-driven EVAs in unknown terrain require more flexible tools than the current generation of EVA assistants. Rather than focus on sequential instructions, there instead needs to be a broad toolkit that's only called upon in specific instances. This AR Toolkit for Lunar Astronauts and Scientists (ATLAS) became the development goal of the project: create a non-intrusive assembly of tools that could be accessed in AR on the field. The current ATLAS design makes use of a geospatially and temporally annotated eld note system called GeoNotes. This allows for data to be collected and coordinated in a way that's synchronized across time, space, and different users. A Mission Control Center (MCC) and Mobile Support Equipment (MSE) were all needed to transport the AR headset into the field with the user. A network infrastructure was designed and set up within the University to enable this functionality. The software is based on a Protocol-Module structure that allows for modular development of each capability. A Protocol Manager coordinates different protocols that make use of modules. Each module tackles a different individual task while the protocol puts each one to use. The protocol manager coordinates when these are called to be used. This software is hosted on a head-mounted display (HMD) with the MCC acting as support from afar. While the software would be unit-tested at each level and each hardware component verified, a final demonstration would serve to prove the system's capabilities: an analog field trek. The team would prepare to support a user in a remote location from the MCC back at the University. A local area near campus would be tested before going out to do sample field geology further away. This unfortunately became impossible with the arrival of COVID-19. Access to all of the facilities to complete the project as planned were shut down. Our team was scattered across the globe and forced to complete the rest virtually. Adjustments were made to produce a small virtual concept in Adobe XD in the meantime. Even digital surveys were created based on the NASA task-load index (TLX) originally intended for testing actual users. The goal shifted towards completing software and getting feedback on the user interfaces (UI) and user experiences (UX). This team has reformed in response to COVID and its focus has shifted to what can be done remotely. There is still an intention to finish the original deliverable described in this report. The work has been expanded beyond the original X-Hab challenge and has instead become its own research e ort to be continued afterwards. This report collects the processes and knowledge gained from a year of studying and working at this problem with two teams. It should preserve it for the time until the world returns to normal and work can resume. CLAWS will be taking over full responsibility from that point forward, eventually surpassing the original needs of the project. While this document captures the work done towards an eventual end, the CLAWS team has written their own proposal alongside it. It outlines a new future for ATLAS beyond X-Hab, BLiSS, and hopefully beyond COVID-19. This project began as a vague goal hoping to place a new technology into the unique setting of exploration science. The project has since comfortably taken root and will hopefully bloom over the next year.

Alex Sena↗

NASA NTRS2020

Velocity, Temperature and Density Measurements in Supersonic Jets

Prediction of the flow field properties in supersonic jets using computational fluid dynamics (CFD) codes is challenging when there is a significant temperature difference between the jet core and the ambient air and/or compressibility effects are substantial. A benchmark set of flow field property data were obtained to assess current CFD capabilities and develop better modeling approaches for these turbulent flow fields where accurate calculation of turbulent heat flux is important. Three different convergent-divergent nozzles were investigated with exit Mach numbers of: 1.36, 1.63 and 2.0 at their perfectly expanded conditions. The conditions of the jet were set to obtain a temperature difference of zero between the jet core and the ambient air, and then the temperature difference was progressively increased, at the same jet Mach number. Particle Image Velocimetry (PIV), spontaneous rotational Raman scattering spectroscopy (SRS), Background Oriented Schlieren (BOS) and probe-based measurements were used to acquire high quality, spatially-resolved measurements of the mean and root mean square (rms) velocities as well as the mean and rms gas temperatures and densities in both hot and cold supersonic jet flows. The non-intrusive flow measurements are compared both against probe measurements and against standard Reynolds averaged Navier-Stokes (RANS) predictions of the supersonic jet flow properties.

Rotational Raman Spectroscopy↗

NASA NTRS2021

Velocity, Temperature and Density Measurements in Supersonic Jets

Raman Spectroscopy↗

NASA NTRS2021

Raman Temperature and Density Measurements in Supersonic Jets

Prediction of flow-field properties in supersonic jets using computational fluid dynamics (CFD) code predictions has become routine; however, obtaining accurate solutions becomes more challenging when there is a significant temperature difference between the jet core and the ambient air and/or compressibility effects are significant. Benchmark sets of flow field property data are required in order to assess current CFD capabilities and develop better modeling approaches for these turbulent flow fields where accurate calculation of temperatures and turbulent heat flux is important. Particle Image Velocimetry (PIV), spontaneous rotational Raman scattering (SRS) spectroscopy and Background Oriented Schlieren (BOS) have been previously used to acquire measurements of the mean and root mean square (rms) velocities, the mean and rms gas temperatures and density gradients in subsonic jet flows and film cooling flows. In this work, the ability to measure density is added to the list of measurands available using the acquired Raman spectra. The suite of measurement techniques are now applied to supersonic jet flows. The computation of the local gas pressure in the potential core of an over-expanded jet is demonstrated using the Raman measured gas temperature and density. Additionally, a unique density feature in temperature matched, perfectly expanded jet flow shear layers identified using BOS was verified using the Raman measurement technique. These non-intrusive flow measurements are compared against RANS predictions of the supersonic jet flow properties as a means of assessing their prediction accuracy.

Raman Spectroscopy↗

NASA NTRSDate not supplied

Uncertainty Estimates for Sonic-Boom Pressure Signatures and Loudness Carpets

A non-intrusive uncertainty quantification method is applied to computational analysis of supersonic, low-boom aircraft. The mean and standard deviation statistics of the pressure waveforms and loudness metrics are evaluated through use of numerical quadrature. The probability density function (p.d.f.) of these outputs is evaluated via kernel density estimation. The simulations use an inviscid, embedded-boundary Cartesian-mesh flow solver in the nearfield combined with an augmented Burgers’ equation solver for propagation in the farfield. The results show that the p.d.f. of the waveform is bimodal at shocks, which makes the mean and standard deviation statistics inappropriate. Despite this limitation, we show that the moment statistics can provide effective assessment of discrepancies when comparing with experimental data. This is demonstrated by presenting uncertainty analysis of a wind-tunnel test and showing that we significantly improve the predictions when we include the test uncertainties in the simulation. Normal distributions are obtained for the ground signature and loudness metrics, which is primarily due to the careful shaping of the low-boom waveform. Separation of variables and error control are used to reduce computational cost. We demonstrate that this is an efficient approach in the sense of balancing numerical errors in the statistics quadrature with discretization errors in the solvers.

ARMD↗

NASA NTRS2021

High-speed wide-angle interleaved scanning technique for a 3D imaging lidar

In this paper, we describe a novel interleaved scanner for an eye-safe 3D scanning lidar system to measure aerodynamic phenomena in a wind tunnel using elastic backscatter from seeding particles. The scanner assembly consists of a rotating polygon scanner for line scanning along the fast axis, a galvanometer (galvo) scanner for scanning along the slow axis, angular position sensors and motor controllers. The polygon scanner sweeps the lidar beam at up to 10,000 lines/s across a 27 deg angular field-of-regard in the fast axis, while the galvo scanner covers an angular range of 20 deg in the slow axis. Using this scanner, the lidar can perform non-intrusive flow visualization, velocimetry, and hard target mapping at mmscale spatial resolution to a standoff range of 5 m at an update rate of 50 Hz for the full field-of-regard. An interleaved scanning methodology for the acquisition of two snapshots of 3D lidar intensity data with a 100 μs time offset is discussed. The design of the control and data acquisition electronics is described. The effects of rapid scanning on the response of a narrow field-of-view lidar are addressed. The design of the scanner is scalable and can be tailored to meet the requirements of other applications by increasing or decreasing the standoff range, angular field-of-regard and scan rate.

3D Imaging Lidar↗

NASA NTRSDate not supplied

HIFiRE Flight 2 Unstart Reliability Analysis

The objective of this work was to assess the unstart reliability of the HIFiRE Flight 2 system. To do this, a quantification of margins and uncertainties framework was used for comparing model predictions of the predicted combustion induced shock location to the predicted last stable shock location within the isolator. Uncertainty sources included parametric uncertainty in the flight conditions, the heat release model, and turbulence modeling, as well as model verification errors. Additionally, an estimate of model-form uncertainty was established by comparing the model to measured ground test data. A computationally efficient non-intrusive polynomial chaos approach was used to propagate parametric uncertainty through the computational flu-ids dynamics models of both the ground test configuration and the flight vehicle. Compared to direct-connect ground test data, computational fluid dynamics predictions yielded about two duct heights of model-form uncertainty. This was applied to a prediction of flight vehicle unstart margin at the Mach 6.5 flight condition. Building up all of the computational model uncertainty, including parametric uncertainty, verification errors, and the determined model-form uncertainty, a 95% probability level based confidence ratio, or a ratio of total uncertainty to a statistical margin measure, was found to be 0.31 for the flight system.

Thomas K West↗

NASA NTRSDate not supplied

Robust Design Under Uncertainty of Hypersonic Inlets

The objective of this work is to optimize scramjet inlet designs under uncertainty at multiple fidelity levels. Optimizations are performed for both deterministic and stochastic conditions. For stochastic conditions, robust design is used to minimize the variance in system performance in addition to optimizing mean system performance. Uncertainty quantification is performed using non-intrusive polynomial chaos. Comparisons are made between low-fidelity analysis and high-fidelity analysis, as well as deterministic optimization and robust optimization. Results indicate that the general design trend of previous inlet optimization techniques is recovered for the external compression portion of an inlet. For the internal compression portion of an inlet, when viscous effects become more significant and boundary layer separation becomes more likely, the optimal trend departs from previous results. Multifidelity uncertainty quantification methods are found to substantially reduce the computation time of robust design while obtaining results that nearly match those of high-fidelity analysis. Robust optimization is found to decrease the standard deviation of throat Mach number by up to 40% compared to deterministic optimization. Changes in the design variables and total turning that lead to robust scramjet inlets are identified and linked back to fundamental physical principles through the theta-beta-Mach function.

Hypersonic↗

NASA NTRS2022

An Agenda for Land Data Assimilation Priorities: Realizing the Promise of Terrestrial Water, Energy, and Vegetation Observations From Space

The task of quantifying spatial and temporal variations in terrestrial water, energy, and vegetation conditions is challenging due to the significant complexity and heterogeneity of these conditions, all of which are impacted by climate change and anthropogenic activities. To address this challenge, Earth Observations (EOs) of the land and their utilization within data assimilation (DA) systems are vital. Satellite EOs are particularly relevant, as they offer quasi-global coverage, are non-intrusive, and provide uniformity, rapid measurements, and continuity. The past three decades have seen unprecedented growth in the number and variety of land remote sensing technologies launched by space agencies and commercial companies around the world. There have also been significant developments in land modeling and DA systems to provide tools that can exploit these measurements. Despite these advances, several important gaps remain in current land DA research and applications. This paper discusses these gaps, particularly in the context of using DA to improve model states for short-term numerical weather and sub-seasonal to seasonal predictions. We outline an agenda for land DA priorities so that the next generation of land DA systems will be better poised to take advantage of the significant current and anticipated shifts and advancements in remote sensing, modeling, computational technologies, and hardware resources.

land surface↗

NASA NTRSDate not supplied

Efficient Parametric Uncertainty Analysis of an Earth Entry Vehicle Concept Using Least Angle Regression

The objective of this work was to outline and apply an efficient and accurate parametric un-certainty propagation approach to the analysis of convective heating on an Earth entry vehicle concept. The described approach was based on Least Angle Regression used to solve a sparse and underdetermined linear system in the point-collocation non-intrusive polynomial chaos surrogate method. This approach involved an iterative process to computing the non-zero terms of the underlying polynomial chaos model using only enough samples to converge uncertainty interval predictions and Sobol index values based global nonlinear sensitivity estimates. The Earth entry vehicle was analyzed at three points along a representative trajectory for a Mars return mission. 329 sources of uncertainty were identified in the computational fluid dynamics model used to predict the forebody convective heating. These included uncertainty in flow field chemical rates, collision integrals, heats of formation, surface finite rate char model reaction rates, wall roughness height, and the turbulent Schmidt number. Results from this study showed that convective heating uncertainty as high as 50% of the nominal was predicted with only about 50 evaluations of the computational model. This was far fewer than would be required for a sampling-based approach or a full basis polynomial chaos model, which would have required over 50,000 samples. Additionally, results showed that over 90% of the total convective heating uncertainty was due to uncertainty in the N2catalytic rate on the surface, while the remainder of the uncertainty was attributed to the turbulent Schmidt number and the wall roughness uncertainties.

Thomas K West IV↗

NASA NTRSDate not supplied

Aerothermodynamic Measurements in Hypersonic Non-Equilibrium Flows

High enthalpy arc-jets are unique facilities particularly suited for simulating complex flows in the aerospace field, such as the aerothermodynamics of a re-entry vehicle. Arc-jets are often used to evaluate important design factors such as heat shield materials and vehicle design. Characterization of these facilities is important, as studies often match specific in-flight environments during experiments. Due to the complex environment produced by an arc-jet, with effects such as thermodynamic and chemical non-equilibrium occurring in the flow, characterization experiments are significantly more difficult than in traditional blow-down wind tunnels. The current work aims to characterize an arc-jet facility in terms of flow temperature, velocity and unsteadiness, in a spatially-resolved analysis. To achieve this goal, a non-intrusive imaging technique called “planar laser-induced fluorescence” was performed in the NASA Langley Hypersonic Materials Environ-mental Test System arc-jet facility. The experimental data was analyzed to produce the quantitative measurements in multiple regions of the flow around a blunt body sample. A quasi-1D low fidelity solver was created to numerically simulate the flow to investigate non-equilibrium effects occur-ring outside the imaging region in the arc-jet nozzle. Unsteadiness in the test section was minimized by analyzing a subset of data assessing the gas injection location. Radial velocity, rotational temperature and translational temperature measurements are provided that can be used to validate future high-fidelity computational studies. The temperature measurements revealed rotational non-equilibrium potentially occurring in the flow. This work provides a methodology for characterizing arc-jet facilities, identifying and correcting sources of systematic error, and estimating the uncertainty associated with the quantitative measurements.

laser induced fluorescence↗

NASA NTRS2022

Aerothermodynamic Measurements of Hypersonic Non-Equilibrium Flows

High enthalpy arc-jets are unique facilities particularly suited for producing complex flows in the aerospace field, such as the aerothermodynamics of a re-entry vehicle. Arc-jets are often used to evaluate important design factors that include heat shield materials and vehicle design. Characterization of these facilities is important, as studies often aim to match specific in-flight environments during experiments. Due to the complex environment produced by an arc-jet, with effects such as thermodynamic and chemical non-equilibrium occurring in the flow, characterization experiments are significantly more difficult than in conventional blow-down wind tunnels. The current work aims to characterize an arc-jet facility through spatially-resolved measurements of flow unsteadiness, temperature, and velocity. To achieve this goal, a non-intrusive imaging technique called “planar laser-induced fluorescence” was performed in the NASA Langley Hypersonic Materials Environmental Test System arc-jet facility. The experimental data was analysed to produce the quantitative measurements in multiple regions of the flow around a blunt body specimen. A three-temperature low fidelity numerical solver was created to simulate the flow in order to investigate thermal non-equilibrium effects occurring outside the imaging region in the arc-jet nozzle. Unsteadiness in the test section of the arc-jet was minimized by analyzing a subset of data assessing the gas injection configuration. Radial velocity, rotational temperature and translational temperature measurements are provided that can be used to validate future computational studies. The temperature measurements revealed rotational non-equilibrium occurring behind the bow-shock near the specimen surface. Computational results show the facility is capable of producing thermal non-equilibrium flow in the arc-jet nozzle. This work provides the first experimental and computational evidence of thermal trans-rotational non-equilibrium occurring in multiple regions of this arc-jet facility. Significant improvements to the methodology are also identified as recommendations for future arc-jet characterization studies.

Laser induced fluorescence↗

NASA NTRS2021

Three-Dimensional Measurement of the Crater Formation During Plume–Surface Interactions Using Stereo-Photogrammetry

The present investigation focused on adapting and validating stereo-photogrammetry for obtaining 3-D, time-resolved, non-intrusive, full-domain measurements of crater evolution during the plume-surface interaction (PSI) process. An atmospheric experimental facility was designed and constructed to facilitate the development of the stereo-photogrammetry technique for PSI applications. Stereo-photogrammetry was then used to measure the dynamic crater evolution process at nozzle heights of 25, 40, 55, and 70 nozzle diameters above the sand simulant bed. From the stereo-photogrammetry data, time-resolved 3-D reconstructions of the crater geometry were generated, and crater depth, radius, and volume time histories were extracted. Crater depth was observed to grow logarithmically for the two highest nozzle heights, and the depth growth rate for the lower two nozzle heights was more rapid. Crater volume growth was well characterized by a power law fit. The slope of the collapsed crater post nozzle flow was found to increase with nozzle height, along with the final crater volume. The results show that stereo-photogrammetry can be used to successfully measure the crater geometry in cases where optical access to the crater is not completely degraded by ejected particles.

DC Stubbs↗

NASA NTRS2020

Collisional-Radiative Models of Neutral and Singly-Ionized Xenon in Hall Thrusters: Experimental Validation and Model Investigations

The recently developed collisional radiative (CR) models for neutral xenon (Xe I) and singly charged xenon ion (Xe II) described by Chaplin et al. in the paper "Insights from Collisional-Radiative Models of Neutral and Singly-Ionized Xenon in Hall Thrusters" also submitted to the 2021 AIAA Propulsion and Energy Forum are more thoroughly investigated. Comparisons between the existing and recently developed JPL Xe I CR models are done and reasons for discrepancies between the two models are explored. An experiment to validate the Xe II CR model is carried out in the anode region of the UCLA Plasma interactions facility. The Xe II CR model is applied to measured xenon ion emission line intensities to determine electron temperature and density. Spatial resolution of these optical measurements is obtained through an Abel inversion for direct comparison to Langmuir probe results. Although the measured electron densities were on the order of $10^{17}$ m$^{-3}$ and the Xe II CR model is most suitable for use with densities above $10^{18}$ m$^{-3}$ due to the strong dependence of the line ratios on electron temperature in that regime, initial results from the validation experiment show reasonable agreements between the optical and Langmuir probe results. The 441 nm to 605 nm line ratio appears to have the most promise for non-intrusive electron temperature measurements with the Xe II CR model. Shortcomings of the Xe II CR model revealed in the validation experiment are to be explored further.

Lobbia, Robert B.↗

NASA NTRSDate not supplied

Development of Langmuir and Spatially Resolved OES Diagnostics for Arc Jet Shock and Boundary Layer Measurements Relevant to Atmospheric Re-Entry Environments

The second-generation miniature Arc Jet Research Chamber (mARC) ground testing facility at NASA Ames requires physical characterization of its supersonic plasma flow to verify numerical models and material sample testing. Two types of plasma diagnostics will be utilized: Langmuir probes and optical emission spectroscopy (OES). Several single and triple Langmuir probes have been constructed and will be inserted parallel to the flow via a sweep arm to measure post-shock electron temperature and number density along radial profiles at different axial distances. Due to the high heat flux (200-3000 W/cm2) sweep durations are necessarily short (< 0.1 s). Measuring these properties near the probe surface provide characterization of the post-shock environment. This is an important metric for validating coupled CFD-material codes, and will provide insight into longstanding thermocouple anomalies attributed to charging of heatshield surfaces. An OES system has also been assembled to obtain spatially resolved density and temperature for various flow species. The system consists of a convex lens that forms an image of the plasma onto a 16-channel linear fiber array, which will simultaneously capture the spectra from sixteen different locations. The light emission from the plasma is then focused by a spherical mirror into a spectrometer and recorded with a camera. These measurements non-intrusively provide a new spatially resolved flow characterization capability. This will initially be used to resolve issues with shock radiation interference in pyrometer measurements of material surface temperature. The design of each diagnostic and any initial results will be discussed.

Ethan Main-Loam Leong↗

NASA NTRSDate not supplied

Contrails Measurement and Testing Capabilities in NASA's Particulate Aerosol Laboratory

The NASA Glenn Research Center Particulate Aerosol Laboratory (PAL) is a ground test facility for studying emissions and contrails at upper atmospheric conditions. The facility consists of a small-scale combustor that generates hot combustion gases and soot nanoparticles, which flow through a transition pipe into a jet nozzle, which exhausts into an altitude chamber. Thermodynamic conditions experienced in flight are matched in the altitude chamber, allowing the study of ice particle formation of simulated aircraft engine exhaust plumes. A non-intrusive optical diagnostic technique based on Mie scattering provides ice particle size, number density, and mass density. A suite of commercial extractive particle measurement instruments provides estimates of soot number density, size, and black carbon mass distributions. Measurements are presented for various fuels at chamber conditions covering an altitude range of 20,000 ft (6 km) to 45,000 ft (14 km) altitude and ambient temperatures from -48°C to -68°C. The data presented demonstrate the effect of soot number density, altitude, and fuel-to-air equivalence ratio on the contrail ice particle formation. Ice mass density measurements are compared to values predicted by a thermodynamic plume similarity solution.

Optical Instrumentation↗

NASA NTRSDate not supplied

Summary of the 6th AIAA Propulsion Aerodynamics Workshop Nozzle Test Case: Heated Supersonic Axisymmetric Jets

This paper summarizes findings from the sixth AIAA Propulsion Aerodynamics Workshop (PAW) nozzle test case. The focus of the workshop participants was turbulent supersonic round jets with variation in jet Mach number and jet heating. Three nozzles were utilized with on-design jet Mach numbers of 1.36, 1.63, and 2.00. A heated jet for each of these three nozzles at on-design conditions, a temperature matched on-design condition at Mach 1.63, and an off-design heated condition for the Mach 1.63 nozzle were the five cases examined. Workshop participants utilized Reynolds-averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) based techniques. Computational fluid dynamics (CFD) solutions were compared with non-intrusive measurements of velocities and temperatures, including both mean values and turbulence statistics. In general, the RANS approaches were unable to capture the trend of reduced mixing as the jet Mach number increased. Incorporation of compressibility corrections improved the agreement with experimental measurements in terms of trends with varying jet Mach number, but also increased the jet potential core lengths to be in worse agreement with data. RANS methods were able to reasonably capture trends of jet heating. The LES-based approaches as a whole were able to capture the effects of compressibility more accurately. Effects of jet heating were captured well by LES. None of the LES approaches introduced disturbances from the wall boundary layers of the nozzle into the jet mixing layer, which would affect the jet flow physics modeling in the initial part of the jet shear layer, but would be very computationally demanding.

supersonic jet↗

NASA NTRSDate not supplied

Heated Supersonic Axisymmetric Jet Cases for the NASA Turbulence Modeling Resource

This paper will describe three new supersonic jet cases for the NASA Turbulence Modeling Resource (TMR). These cases were taken from the 6th AIAA Propulsion Aerodynamics Workshop (PAW) nozzle test problem, which utilized data taken at NASA GRC consisting of non-intrusive measurements of jet plume velocities and temperatures, including both mean values and turbulence statistics. The three jet cases all used a Mach 1.63 axisymmetric nozzle: A heated jet for each at on-design conditions, a temperature-matched on-design condition at Mach 1.63, and an off-design heated condition for the Mach 1.63 nozzle. Computational fluid dynamics (CFD) solutions are obtained using three established Reynolds-averaged Navier-Stokes (RANS) codes: Wind-US, FUN3D, and Vulcan, all using the Menter Shear Stress Transport (SST) k-ω turbulence model. The NASA TMR requires at least two CFD codes yielding essentially identical results to certify that the approaches are verified, that is - providing solutions that may not necessarily provide close comparisons with experimental data, but solve the posed CFD equations as intended.

nozzle↗