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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Analysis of Emission Spectra from Arc-jet Shock Layer Flows

This paper reports computational comparisons with experimental studies of a nonequilibrium blunt body shock layer in a high enthalpy arc-jet wind tunnel at NASA Ames Research Center. The primary objective of this work is to investigate the existence of a thermochemical equilibrium region in the shock layer. The existence of such an equilibrium region is of interest for following reasons: (1) to understand the equilibration process behind the shock in an arc-jet flow environment; (2) to interpret measured surface heat transfer data for purpose of determining surface catalytic efficiency, and (3) to determine the total enthalpy from the spectroscopic measurements. The paper will present an analysis of the experimental data obtained in the arc-jet wind tunnel. Experimental data includes measurements of emission spectra of radiation emanating from a shock layer formed in front of a 6-inch flat-faced cylinder. The measurements, obtained using a two dimensional CCD camera mounted on a spectrograph, provide spatially resolved spectra along the stagnation streamline of the model. Computational analysis includes simulation of nonequilibrium flow in the arc-jet facility (flow in the conical nozzle and shock layer in front of a flat-faced cylinder) using 2-D/axisymmetric Navier-Stokes codes and prediction of the radiation spectra from the axisymmetric flowfield using NEQAIR radiation code. Various line-of-sight averaged flow properties such as vibrational and rotational temperatures, species number densities within the shock layer are deduced from the experimental spectra. Comparison of the computed and experimental line-of-sight averaged flow properties provides assessment of thermochemical equilibration processes in an arc-jet shock layer.

Gokcen, T.↗
NASA NTRS2001

Gravity Estimation from a Simulated GRACE Mission: Short vs. Long Arcs

We present simulations of gravity estimation from a GRACE-like satellite mission: low-low intersatellite tracking with a precision of order 1 micron s(exp -1) yielding gravity fields of degree and order 120. We employ a unique parameterization of the intersatellite baseline vector which allows the gravity estimation to be performed (relatively) independently of the GPS (global positioning system) tracking data once sufficiently accurate orbits are obtained. This considerably simplifies data processing during the gravity estimation. During that process only certain components of the baseline parameterization need be adjusted; other components are uncorrelated with gravity and may be adopted unchanged from the initial GPS orbits. The technique is also amenable to very short arcs of data. We present comparisons of gravity estimation from 30 days of observations with arcs of length 15 minutes vs. arcs of one day. Our 'truth' field is the EGM96 (Earth Gravitational Model) model; our prior field is a degree-70 clone of EGM96, perturbed from it by amounts comparable to the standard errors of EGM96 (and identically zero for degrees 71-120). For a high inclination orbit, the short-arc analysis recovers low order gravity coefficients remarkably well, although higher order terms, especially sectorial terms, are understandably less accurate. The simulations suggest that either long or short arcs of GRACE data are likely to improve parts of the geopotential spectrum by several orders of magnitude. This is especially so for low order coefficients, which are markedly improved for all degrees through 120.

Rowlands, David D.↗
NASA NTRS2002

Solar Array Arcing Failure Mode and High Voltage Array Testing

In 1998, a new failure mode for space solar arrays was discovered. A flowchart for this failure mode is presented. Since the discovery of this arc failure mode, many tactics have been used to defeat it. The arc thresholds and arc mitigation strategies must be determined in vacuum-plasma tank testing on Earth. Results from these tests must then be extrapolated to the space plasma environment. Thus, the test conditions on Earth must be adequate to reproduce the important aspects of the phenomenon in space. At Glenn Research Center, we have been testing solar arrays for their arc thresholds and sustained arcing thresholds. In this paper, we detail the test conditions for a specific set of tests-those aimed at qualifying the Boeing Solar Tile solar arrays to operate in space at very high voltages (300 V or more).

Ferguson, Dale C.↗
NASA NTRS2002

Thermal Protection System Evaluation Using Arc-jet Flows: Flight Simulation or Research Tool?

The arc-jet has been used to evaluate thermal protection systems (TPS) and materials for the past forty years. Systems that have been studied in this environmerd include ablators, active, and passive TPS concepts designed for vehicles entering planetary and Earth atmospheres. The question of whether arc-jet flow can simulate a flight environment or is it a research tool that provides an aero-thermodynamic heating environment to obtain critical material properties will be addressed. Stagnation point tests in arc-jets are commonly used to obtain material properties such as mass loss rates, thermal chemical stability data, optical properties, and surface catalytic efficiency. These properties are required in computational fluid dynamic codes to accurately predict the performance of a TPS during flight. Special facilities have been developed at NASA Ames Research Center to approximate the flow environment over the mid-fuselage and body flap regions of proposed space-planes type vehicles. This paper compares flow environments generated in flight over a vehicle with those created over an arc-jet test articles in terms of scale, chemistry, and fluid dynamic properties. Flight experiments are essential in order to validate the material properties obtained from arc-jet tests and used to predict flight performance of any TPS being considered for use on a vehicle entering the Earth atmosphere at hypersonic speed.

Stewart, David A.↗
NASA NTRS2003

Thermo Physics Facilities Branch Brochure ARC Jet Complex Fact Sheets, Hypervelocity Free-Flight Aerodynamic Facility Fact Sheets, Ames Vertical Gun Range Fact Sheets

The Ames Arc Jet Complex has a rich heritage of over 40 years in Thermal Protection System (TPS) development for every NASA Space Transportation and Planetary program, including Apollo, Space Shuttle, Viking, Pioneer-Venus, Galileo, Mars Pathfinder,Stardust, NASP,X-33,X-34,SHARP-B1 and B2,X-37 and Mars Exploration Rovers. With this early TPS history came a long heritage in the development of the arc jet facilities. These are used to simulate the aerodynamic heating that occurs on the nose cap, wing leading edges and on other areas of the spacecraft requiring thermal protection. TPS samples have been run in the arc jets from a few minutes to over an hour,from one exposure to multiple exposures of the same sample, in order t o understand the TPS materials response to a hot gas flow environment (representative of real hyperthermal environments experienced in flight). The Ames Arc l e t Complex is a key enabler for customers involved in the three major areas of TPS development: selection, validation, and qualification. The arc jet data are critical for validating TPS thermal models, heat shield designs and repairs, and ultimately for flight qualification.

Fretter, E. F.↗
NASA NTRS2006

Free Fall Plasma-Arc Reactor for Synthesis of Carbon Nanotubes in Microgravity

High temperatures inside the plasma of a carbon arc generate strong buoyancy driven convection which has an effect on the growth and morphology of the single-walled carbon nanotubes (SWNTs). To study the effect of buoyancy on the arc process, a miniature carbon arc apparatus was designed and developed to synthesize SWNTs in a microgravity environment substantially free from buoyant convective flows. An arc reactor was operated in the 2.2- and 5.18-second drop towers at the NASA Glenn Research Center. The apparatus employed a 4 mm diameter anode and was powered by a portable battery pack capable of providing in excess of 300 amps at 30 volts to the arc for the duration of a 5-second drop. However, the principal result is that no dramatic difference in sample yield or composition was noted between normal gravity, 2.2-and 5-second long microgravity runs.

Alford, J. M.↗
NASA NTRS1997

Arc burst pattern analysis fault detection system

A method and apparatus are provided for detecting an arcing fault on a power line carrying a load current. Parameters indicative of power flow and possible fault events on the line, such as voltage and load current, are monitored and analyzed for an arc burst pattern exhibited by arcing faults in a power system. These arcing faults are detected by identifying bursts of each half-cycle of the fundamental current. Bursts occurring at or near a voltage peak indicate arcing on that phase. Once a faulted phase line is identified, a comparison of the current and voltage reveals whether the fault is located in a downstream direction of power flow toward customers, or upstream toward a generation station. If the fault is located downstream, the line is de-energized, and if located upstream, the line may remain energized to prevent unnecessary power outages.

Russell, B. Don↗
NASA NTRS2010

Arc-Second Alignment of International X-Ray Observatory Mirror Segments in a Fixed Structure

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc-seconds. These mirror segments are 0.4 mm thick, and 200 to 400 mm in size, which makes it hard to meet the strict angular resolution requirement of 5 arc-seconds for the telescope. This paper outlines the precise alignment, verification testing, and permanent bonding techniques developed at NASA's Goddard Space Flight Center (GSFC). These techniques are used to overcome the challenge of transferring thin mirror segments from a temporary mount to a fixed structure with arc-second alignment and minimal figure distortion. Recent advances in technology development in addition to the automation of several processes have produced significant results. Recent advances in the mirror fixture process known as the suspension mount has allowed for a mirror to be mounted to a fixture with minimal distortion. Once on the fixture, mirror segments have been aligned to around 5 arc-seconds which is halfway to the goal of 2.5 arc-seconds per mirror segment. This paper will highlight the recent advances in alignment, testing, and permanent bonding techniques as well as the results they have produced.

Evans, Tyler, C.↗
NASA NTRS2005

More About Arc-Welding Process for Making Carbon Nanotubes

High-quality batches of carbon nanotubes are produced at relatively low cost in a modified atmospheric-pressure electric-arc welding process that does not include the use of metal catalysts. What would normally be a welding rod and a weldment are replaced by an amorphous carbon anode rod and a wider, hollow graphite cathode rod. Both electrodes are water-cooled. The cathode is immersed in ice water to about 0.5 cm from the surface. The system is shielded from air by flowing helium during arcing. As the anode is consumed during arcing at 20 to 25 A, it is lowered to maintain it at an approximately constant distance above the cathode. The process causes carbon nanotubes to form on the lowest 5 cm of the anode. The arcing process is continued until the anode has been lowered to a specified height. The nanotube-containing material is then harvested. The additional information contained in the instant report consists mostly of illustrations of carbon nanotubes and a schematic diagram of the arc-welding setup, as modified for the production of carbon nanotubes.

Benavides, Jeanette M.↗
NASA NTRS2011

Emission Spectroscopic Measurements with an Optical Probe in the NASA Ames IHF Arc Jet Facility

An optical probe was designed to measure radiation (from inside the arc heater) incident on a test sample immersed in the arc-heated stream. Currently, only crude estimates are available for this incident radiation. Unlike efforts of the past, where the probe line of sight was inclined to the nozzle centerline, the present development focuses on having the probe line of sight coincide with the nozzle centerline. A fiber-coupled spectrometer was used to measure the spectral distribution of incident radiation in the wavelength range of 225 to 900 nm. The radiation heat flux in this wavelength range was determined by integration of measured emission spectral intensity calibrated to incident irradiance from an integrating sphere. Two arc-heater conditions, corresponding to stream bulk enthalpy levels of 12 and 22 MJ/kg, were investigated in the 13-inch diameter nozzle of the Interaction Heating Facility at NASA Ames Research Center. With the probe placed at a distance of 10 inches from the nozzle exit plane, total radiative heat fluxes were measured to be 3.3 and 8.4 W/sq cm for the 12 and 22 MJ/kg conditions, respectively. About 17% of these radiative fluxes were due to bound-bound radiation from atoms and molecules, while the remaining 83% could be attributed to continua (bound-free and/or free-free). A comparison with spectral simulation based on CFD solutions for the arc-heater flow field and with spectroscopic measurements in the plenum region indicates that more than 95% of the measured radiation is generated in the arc region. The total radiative heat flux from the line radiation could increase by a factor of two through contributions from wavelengths outside the measured range, i.e., from the vacuum ultraviolet (wavelengths less than 225 nm) and the infrared (wavelengths greater than 900 nm). An extrapolation of the continuum radiation to these two wavelength regions was not attempted. In the tested configuration, the measured radiative heat flux accounts for only about 1.4% of the nominal heat flux on a flat face model and therefore is considered negligible. In the 6-inch diameter nozzle, on account of shorter path lengths, the radiation heat flux could be significant. Therefore, future tests in the 6-inch nozzle will have radiometers in addition to the optical probe.

Winter, Michael↗
NASA NTRS2012

Characterization of Material Response During Arc-Jet Testing with Optical Methods Status and Perspectives

The characterization of ablation and recession of heat shield materials during arc jet testing is an important step towards understanding the governing processes during these tests and therefore for a successful extrapolation of ground test data to flight. The behavior of ablative heat shield materials in a ground-based arc jet facility is usually monitored through measurement of temperature distributions (across the surface and in-depth), and through measurement of the final surface recession. These measurements are then used to calibrate/validate materials thermal response codes, which have mathematical models with reasonably good fidelity to the physics and chemistry of ablation, and codes thus calibrated are used for predicting material behavior in flight environments. However, these thermal measurements only indirectly characterize the pyrolysis processes within an ablative material pyrolysis is the main effect during ablation. Quantification of pyrolysis chemistry would therefore provide more definitive and useful data for validation of the material response codes. Information of the chemical products of ablation, to various levels of detail, can be obtained using optical methods. Suitable optical methods to measure the shape and composition of these layers (with emphasis on the blowing layer) during arc jet testing are: 1) optical emission spectroscopy (OES) 2) filtered imaging 3) laser induced fluorescence (LIF) and 4) absorption spectroscopy. Several attempts have been made to optically measure the material response of ablative materials during arc-jet testing. Most recently, NH and OH have been identified in the boundary layer of a PICA ablator. These species are suitable candidates for a detection through PLIF which would enable a spatially-resolved characterization of the blowing layer in terms of both its shape and composition. The recent emission spectroscopy data will be presented and future experiments for a qualitative and quantitative characterization of the material response of ablative materials during arc-jet testing will be discussed.

Winter, Michael↗
NASA NTRS2012

Flowfield Analysis of a Small Entry Probe (SPRITE) Tested in an Arc Jet

A novel concept of small size (diameter less than 15 inches) entry probes named SPRITE (Small Probe Re-entry Investigation for TPS Engineering) has been developed at NASA Ames Research Center (ARC). These flight probes have on-board data acquisition systems that have also been developed in parallel at NASA ARC by Greg Swanson1. Flight probes of this size facilitate testing over a wide range of conditions in arc jets available at NASA ARC, thereby fulfilling a 'test what you fly' paradigm. As indicated by the acronym, these probes, with suitably tailored trajectories, are primarily meant to be robotic flight test beds for TPS materials, although the design is flexible enough to accommodate additional objectives of flight-testing other vehicle subsystems. A first step towards establishing the feasibility of the SPRITE concept is to arc-jet test fully instrumented models at flight scale. In a follow-on to the Large-Scale Article Tests (LSAT2) performed in the 60 MW Interaction Heating Facility (IHF) in late 2008/early 2009, a full-scale model of Deep Space-2 (DS23) made of red oak was tested in the 20 MW Aerodynamic Heating Facility (AHF). There were no issues with mass capture by the diffuser for blunt bodies of roughly 15 inches diameter tested in the 18-inch nozzle of the AHF. Building on this initial success, two identical test articles - SPRITE-T1-1 and SPRITE-T1-2 (T1 indicating the choice of back shell geometry) - were fabricated, and one of them, SPRITE-T1-1, was tested in the AHF recently. Both these test articles, 14 inches in diameter, have a 45deg sphere-cone (like DS2) made of PICA bonded on to a 1/8th inch thick aluminum shell using RTV. The aft portion of the test article is a conical frustum (15deg cone angle) with LI-2200 bonded on to the aluminum shell. Each model is fully instrumented with: (a) thermocouples imbedded in plugs in the heat shield, (b) thermocouples bonded to the aluminum substructure; the thermocouples are distributed over the entire shell, and (c) a few strain gages. Data from some of the thermocouples and gages are acquired by the on-board data acquisition system (DAS), while data from the others are routed to the facility-provided DAS, thereby enabling a cross check on the in situ measurement capability. as inputs to v2.6.1 of the in-house materials thermal response code, FIAT

atmospheric entry↗
NASA NTRS2002

The Design and Use of Calorimeters For Characterization of High-Enthalpy Flows in Arc-Heated Test Facilities

High-enthalpy, arc-heated flows used for aerothermal testing present a challenging environment for flow characterization. This paper describes the design and use of cooled dwell probes used for heat-transfer and pressure characterization of the NASA and United States Department of Defense (DoD) arc facilities located at Moffett Field, CA, and Arnold Air Force Base, TN. Dwell calorimeters designed, fabricated, and tested by Thermal Technologies, Inc. (TTI) in the NASA IHF and the USAF H1 and H2 arc test facilities provide heat flux and pressure data with excellent repeatability. These calorimeters use standard Gardon calorimeter gages and pressure ports with unique cooling systems enabling them to withstand the severe arc-heated environments for durations sufficient for acquisition of steady-state data. The TTI probes have proven very robust in the extreme aerothermal environments of these facilities. This paper provides an overview of calorimeter instruments typically used in arc facilities, discusses design features of the TTI dwell probes, presents selected data acquired by the TTI calorimeters, and provides comparisons with data acquired from using measurement techniques.

D Mark Smith↗
NASA NTRS2019

CFD Simulations of the IHF Arc-Jet Flow: 9-Inch Nozzle, Flow Surveys, LEAF Wedge Calibration Data

This paper reports computational analyses and flow characterization studies in a high enthalpy arc-jet facility at NASA Ames Research Center. These tests were conducted using a wedge model placed in a free jet downstream of new 9-inch diameter conical nozzle in the Ames 60-MW Interaction Heating Facility. Both the nozzle and wedge model were specifically designed for testing in the new Laser-Enhanced Arc-jet Facility. Data were obtained using stagnation calorimeters and wedge models placed downstream of the nozzle exit. Two instrumented wedge calibration plates were used: one water-cooled and the other RCG-coated tile plate. Experimental surveys of arc-jet test flow with pitot and heat flux probes were also performed at three arc-heater conditions, providing assessment of the flow uniformity and valuable data for the flow characterization. The present analysis comprises computational fluid dynamics simulations of the nonequilibrium flowfield in the facility nozzle and test box, including the models tested, and comparisons with the experimental measurements. By taking into account nonuniform total enthalpy and mass flux profiles at the nozzle inlet as well as the expansion waves emanating from the nozzle exit and their effects on the model flowfields, these simulations approximately reproduce the probe survey data and predict the wedge model surface pressure and heat flux measurements.

Arc-jets↗
NASA NTRSDate not supplied

Stochastic Reconstruction of Thermal Protection Material Properties from Arc-Jet Experiments

Material response models are used to assess reliability using variances in the bond-line temperature predictions based on uncertainties in trajectory, aerothermal environment, and material properties. A key deficiency in the current approach is that input uncertainties are too often subjective, empirical, or ad-hoc, and are not rigorously linked to the arc-jet test data used to develop the TPS material model. While materials such as PICA are well understood, future missions may require more novel materials such as HEEET where unknown uncertainties have real consequences on the ability to assess reliability. A quantifiable estimate of reliability requires an iterative methodology where the parameters driving the variance in bond-line temperature (for example) are systematically identified. A test campaign to collect data or develop new models can then be identified to reduce those input uncertainties. A Bayesian inference loop defines these connections mathematically, i.e., prior knowledge about uncertainty is updated based on observation. While these concepts are well known (and often applied intuitively in a non-rigorous approach), only recent advances in reduced-order modelling have made them computationally viable methods for engineering. By replacing deterministic inverse methods with stochastic approaches, the hope is new materials proposed for future missions can more rapidly be developed with a greater understanding of the TPS material reliability. Two additional steps for the analysis of arc jet test data are discussed. The first is ability to construct a reduced-order model using material response simulations (Icarus/US3D) of the arc-jet test articles, and the second is the inclusion of this surrogate model in the Bayesian inversion process. Both capabilities will be demonstrated using prior PICA arc-jet test data. The quality of a surrogate model will be investigated and the variances on the calibrated material properties will be compared to our current understanding of the PICA material model.

Material response↗
DOE OSTI2025

The Automatic Reactor Control System (ARCS) Upgrade, version 2.0 for TREAT

The Transient REActor Test Facility (TREAT) recently underwent an upgraded to the Automatic Reactor Control System (ARCS). The purpose of the upgrade was to institute a new software architecture that is better suited for the programming environment, patched software bugs and applied two new segments for reactor control. This paper will focus on the new segments for reactor control. The two new control segments added to ARCS are called Generic Power and Generic Rods. The original version of ARCS provided only two power related functions, namely periods and ramps, that had to be spliced together to generate any power shape. The Generic Power segment allows the user to input data points to define the function and then the algorithm does its best to create the desired shape. The original ARCS program utilized two direct rod commands (i.e. open loop control), these were a rod stop and clip. A Generic Rod segment extends the ability of the computer to directly command any rod position. The functionality of these new segments was proven during the TREAT outage in 2024.

46 - INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AN↗
DOE OSTI2025

ARCS: Agentic Retrieval-Augmented Code Synthesis with Iterative Refinement

Agentic Retrieval-Augmented Code Synthesis with Iterative RefinementIn supercomputing, efficient and optimized code generation is essential to leverage high-performance systems effectively. We have developed Agentic Retrieval-Augmented Code Synthesis (ARCS), an advanced framework for accurate, robust, and efficient code generation, completion, and translation. ARCS integrates Retrieval-Augmented Generation (RAG) with Chain-of-Thought (CoT) reasoning to systematically break down and iteratively refine complex programming tasks. An agent-based RAG mechanism retrieves relevant code snippets, while real-time execution feedback drives the synthesis of candidate solutions. This process is formalized as a state-action search tree optimization, balancing code correctness with editing efficiency. Evaluations on the Geeks4Geeks and HumanEval benchmarks demonstrate that ARCS significantly outperforms traditional prompting methods in translation and generation quality. By enabling scalable and precise code synthesis, ARCS offers transformative potential for automating and optimizing code development in supercomputing applications, enhancing computational resource utilization

Bhattarai, Manish [Los Alamos National Labs]↗
DOE OSTI2025

Optimization of Scrap Melting Using an Electric Arc in Steel Manufacturing

Steel industry is crucial to the national economy and security. Around 67% of crude steel in the U.S is produced in electric arc furnaces (EAF), which is energy intensive. Around 140 EAFs operate in the U.S., consuming about 8.6x10 7 MMBtu/year of electricity. One of major challenges for EAFs includes maximizing the efficiency of the electrical energy provided in the form of electric arcs to melt various scrap mixes. To address this issue, a computational fluid dynamics (CFD) methodology is chosen to analyze scrap melting using the electric arc. Due to complex furnace phenomena and the wide variety of potential scenarios, high performance computing (HPC) is essential to yield comprehensive and detailed CFD analyses and systematic parametric studies for optimized EAF operation. The objectives are to 1) simulate scrap melting using electric arc, 2) evaluate electrode/arc position for optimum scrap melting and 3) establish reduced order model for CFD data-base for fast model calculation.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗