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At least 127 records · Page 7

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DOE OSTI2024

Estimation of mean electron energy in helium surface ionization waves on dielectric substrates

Abstract The determination of basic plasma parameters in atmospheric pressure discharges is critical to advancing their use in applications. Atmospheric pressure plasma jets have found use in the fields of medicine, agriculture, material modification and others. Atmospheric pressure plasma jets often generate plasma surface ionization waves (SIW) which interact with and propagate over surfaces. Electrical diagnostics are challenging in SIW due to high collision frequencies and small scale of the plasma discharge. This work employs a passive optical emission line ratio technique to estimate the mean electron energy in SIW over planar dielectric substrates. The method uses an intensity ratio of two helium triplet lines: He( 3 3 S ) at 706.5 nm and He( 3 3 D ) at 587.56 nm. A collisional-radiative model is used to correlate line ratio to mean electron energy and determine dependencies on electron density and He/air gas mixture. Mean electron energies ranging from 3–8 eV are determined in He/air mixtures and are found to remain constant as the surface wave propagates radially. This work provides a 2D, time-resolved, mean electron energy diagnostic for surface ionization wave propagation and validation of numerical modeling in atmospheric pressure systems with spatially varying He/air gas mixtures. The model in question is designed for use with any He line ratio in the n = 3 excitation level.

Morsell, Joshua (ORCID:0000000331073002)↗

NASA NTRS1972

Investigation of gaseous nuclear rocket technology

The experimental and theoretical investigations conducted during the period from September 1969 through September 1972 are reported which were directed toward obtaining information necessary to determine the feasibility of the full-scale nuclear light bulb engine, and of small-scale nuclear tests involving fissioning uranium plasmas in a unit cell installed in a driver reactor, such as the Nuclear Furnace. Emphasis was placed on development of RF simulations of conditions expected in nuclear tests in the Nuclear Furnace. The work included investigations of the following: (1) the fluid mechanics and containment characteristics of one-component and two-component vortex flows, both unheated and RF-induction heated; (2) heating of particle-seeded streams by thermal radiation from a dc arc to simulate propellant heating; (3) condensation and separation phenomena for metal-vapor/heated-gas mixtures to provide information for conceptual designs of components of fuel exhaust and recycle systems; (4) the characteristics of the radiant energy spectrum emitted from the fuel region, with emphasis on definition of fuel and buffer-gas region seed systems to reduce the ultraviolet radiation emitted from the nuclear fuel; and (5) the effects of nuclear radiation on the optical transmission characteristics of transparent materials.

Kendall, J. S.↗

NASA NTRS1976

Electrophoresis experiment, experiment MA-014

A continuous, free flow electrophoresis study was conducted during the Apollo Soyuz Test Project mission to investigate and evaluate the increase in sample flow rate and sample resolution achievable in space. The electrophoresis equipment was designed for the separation of four mixtures of biological cells with variable sample flow rates, buffer flow rates, and electric field gradients. Separation quality was assessed by measuring the light from a quartz lamp through the electrophoresis channel and on to a photodiode system. The preliminary results indicate that all monitored systems operated correctly during the experiment. The optical system produced a light that was too bright to discern true cell distributions, but data were received that show a distribution of separated cells.

Hannig, K.↗

NASA NTRS1977

Electrophoresis experiment. Experiment MA-014

A continuous free-flow electrophoresis study was conducted during the Apollo-Soyuz Test Project Mission to investigate and evaluate the increase in sample flow rate and sample resolution achievable in space. The electrophoresis equipment was designed for the separation of four mixtures of biological cells with variable sample flow rates, buffer flow rates, and electric field gradients. Separation quality was assessed by measuring the light from a quartz lamp through the electrophoresis channel and onto a photodiode system. The data evaluation indicates that all monitored systems operated correctly during the experiment. The optical system produced a light that was too bright to discern true cell distributions, but final analysis of scientific data by computer processing shows the expected distribution of separated cells.

Hannig, K. H.↗

NASA NTRS1981

The storage of hydrogen in the form of metal hydrides: An application to thermal engines

The possibility of using LaNi56, FeTiH2, or MgH2 as metal hydride storage sytems for hydrogen fueled automobile engines is discussed. Magnesium copper and magnesium nickel hydrides studies indicate that they provide more stable storage systems than pure magnesium hydrides. Several test engines employing hydrogen fuel have been developed: a single cylinder motor originally designed for use with air gasoline mixture; a four-cylinder engine modified to run on an air hydrogen mixture; and a gas turbine.

Gales, C.↗

NASA NTRS1990

Space Station auxiliary thrust chamber technology

The objective was to establish a technical data base to support future development of GO2/GH2 flight thrusters for a Space Station Auxiliary Propulsion System. Specific issues of concern were thruster performance and cycle life. To address these issues, NASA funded Aerojet to design, fabricate, and altitude test two 25-lbf GO2/GH2 thrusters. The first thruster was designed to operate at a nominal mixture ratio (O/F) of 4.0 and expansion area ratio (epsilon) of 100:1. It was tested over a range of O/F from 2.0 to 8.0, achieving a range of specific impulse (Isp) from 440 to 310 lbf-sec/Ibm. The second thruster was optimized for a nominal O/F of 8.0 at a lower nozzle expansion area ratio, epsilon, of 30:1. This second thruster was tested over an O/F range of 3.0 to 9.5, achieving an Isp range of 416 to 3323 lbf-sec/Ibm, respectively. At O/F = 8.0, the Isp was 360 lbf-sec/Ibm, as predicted.

Robinson, Philip J.↗

NASA NTRS1999

Non-Toxic Orbital Maneuvering System Engine Development

Recent results using the Aestus engine operated with LOx/ethanol propellant are presented. An experimental program at Rocketdyne Propulsion and Power is underway to adapt this engine for the Boeing Reusable Space Systems Division non-toxic Orbital Maneuvering System/Reaction control System (OMS/RCS) system. Daimler-Chrysler Aerospace designed the Aestus as an nitrogen tetroxide/monomethyl hydrazine (NTO/MMH) upper-stage engine for the Ariane 5. The non-toxic OMS/RCS system's preliminary design requires a LOx/ethanol (O2/C2H5OH) engine that operates with a mixture ratio of 1.8, a specific impulse of 323 seconds, and fits within the original OMS design envelope. This paper describes current efforts to meet these requirements including, investigating engine performance using LOx/ethanol, developing the en-ine system sizing package, and meeting the vehicle operation parameters. Data from hot-fire testing are also presented and discussed.

Green, Christopher↗

DOE OSTI2024

Rapid Assessment of Sulfate Resistance in Mortar and Concrete

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can reduce the time required for assessing the sulfate resistance of mixtures by 70%. Class F fly ash has historically been used in concrete mixtures to improve sulfate resistance. However, environmental considerations and the evolving energy industry have decreased its availability, requiring the identification of economically viable and environmentally friendly alternatives to fly ash. Another challenge in addressing sulfate attack durability issues in concrete is that the standard sulfate attack test (ASTM C1012) is time-consuming and designed for only standard mortars (not concrete mixtures). To expedite the testing process, accelerated testing methods for both mortar and concrete mixtures were adopted from previous work to further the development of the accelerated tests and to assess the feasibility of testing the sulfate resistance of mortar and concrete mixtures rapidly. This study also established criteria for interpreting sulfate resistance for each of the test methods used in this work. A total of 14 mortar mixtures and four concrete mixtures using two types of Portland cement (Type I and Type I/II) and various supplementary cementitious materials (SCMs) were evaluated in this study. The accelerated testing methods significantly reduced the evaluation time from 12 months to 21 days for mortar mixtures and from 6 months to 56 days for concrete mixtures. The proposed interpretation method for mortar accelerated test results showed acceptable consistency with the ACI 318-19 interpretations for ASTM C1012 results. The interpretation methods proposed for the two concrete sulfate attack tests demonstrated excellent consistency with the ASTM C1012 results from mortar mixtures with the same cementitious materials combinations. Metakaolin was shown to improve sulfate resistance for both mortar and concrete mixtures, while silica fume and natural pozzolan had a limited impact. Using 15% metakaolin in mortar or concrete mixtures with Type I/II cement provided the best sulfate resistance.

Chemistry↗

NASA NTRS1992

A new unsteady mixing model to predict NO(x) production during rapid mixing in a dual-stage combustor

An advanced gas turbine engine to power supersonic transport aircraft is currently under study. In addition to high combustion efficiency requirements, environmental concerns have placed stringent restrictions on the pollutant emissions from these engines. A dual-stage combustor with the potential for minimizing pollutants such as NO(x) emissions is undergoing experimental evaluation. A major technical issue in the design of this combustor is how to rapidly mix the hot, fuel-rich primary stage product with the secondary diluent air to obtain a fuel-lean mixture for combustion in the secondary stage. Numerical design studies using steady-state methods cannot account for the unsteady phenomena in the mixing region. Therefore, to evaluate the effect of unsteady mixing and combustion processes, a novel unsteady mixing model is demonstrated here. This model has been used in a stand-alone mode to study mixing and combustion in hydrogen-air nonpremixed jet flames. NO(x) production in these jet flames was also predicted. Comparison of the computed results with experimental data show good agreement thereby providing validation of the mixing model.

Menon, Suresh↗

NASA NTRS1983

Studies of proton-irradiated cometary-type ice mixtures

Cometary ice mixtures are studied in a laboratory experiment designed to simulate the temperature, pressure and radiation environments of the interstellar Oort cloud region, in order to test the hypothesized radiation synthesis mechanism for changing the characteristics of the outer few meters of a comet stored in the Oort cloud for 4.6 billion years. All experiments conducted confirm the synthesis of new molecular species in solid phase mixtures at 20 K. When CH4 is present in the irradiated ice mixture, long chained, voltaile hydrocarbon and CO2 are synthesized together with high molecular weight C compounds present in the room temperature residue. Due to radiation synthesis, about 1 percent of the ice was converted into a nonvolatile residue containing complicated C compounds not present in the blank samples. These results suggest that initial molecular abundances can be altered, and new species created, as a result of radiation synthesis. Irradiated mixtures exhibited thermoluminescence and pressure enhancements during warming, showing the synthesis of reactive species. Outbursts in new comets resulting from similar irradiation-induced exothermic activity would be expected to begin occurring at distances of the order of 100 AU.

Moore, M. H.↗

NASA NTRS1988

Latent energy storage with salt and metal mixtures for solar dynamic applications

This paper examines three design alternatives for the development of a solar dynamic heat receiver as applied to power systems operating in low earth orbit. These include a base line design used for comparison in ongoing NASA studies, a system incorporating a salt energy storage system with the salt dispersed within a metal mesh and a hybrid system incorporating both a molten salt and molten metal for energy storage. Based on a typical low earth orbit condition, designs are developed and compared to determine the effect of resultant conductivity, heat capacity and heat of fusion on system size, weight, temperature gradients, cycle turbine inlet temperature and material utilization.

Crane, R. A.↗

NASA NTRS2003

Gravity Effects Observed In Partially Premixed Flames

Partially premixed flames (PPFs) contain a rich premixed fuel air mixture in a pocket or stream, and, for complete combustion to occur, they require the transport of oxidizer from an appropriately oxidizer-rich (or fuel-lean) mixture that is present in another pocket or stream. Partial oxidation reactions occur in fuel-rich portions of the mixture and any remaining unburned fuel and/or intermediate species are consumed in the oxidizer-rich portions. Partial premixing, therefore, represents that condition when the equivalence ratio (phi) in one portion of the flowfield is greater than unity, and in another section its value is less than unity. In general, for combustion to occur efficiently, the global equivalence ratio is in the range fuel-lean to stoichiometric. These flames can be established by design by placing a fuel-rich mixture in contact with a fuel-lean mixture, but they also occur otherwise in many practical systems, which include nonpremixed lifted flames, turbulent nonpremixed combustion, spray flames, and unwanted fires. Other practical applications of PPFs are reported elsewhere. Although extensive experimental studies have been conducted on premixed and nonpremixed flames under microgravity, there is a absence of previous experimental work on burner stabilized PPFs in this regard. Previous numerical studies by our group employing a detailed numerical model showed gravity effects to be significant on the PPF structure. We report on the results of microgravity experiments conducted on two-dimensional (established on a Wolfhard-Parker slot burner) and axisymmetric flames (on a coannular burner) that were investigated in a self-contained multipurpose rig. Thermocouple and radiometer data were also used to characterize the thermal transport in the flame.

Puri, Ishwar K.↗

DOE OSTI2025

A comparison of surrogate constitutive models for viscoplastic creep simulation of HT-9 steel

Mechanistic microstructure-informed constitutive models for the mechanical response of polycrystals are a cornerstone of computational materials science. However, as these models become increasingly more complex – often involving coupled differential equations describing the effect of specific deformation modes – their associated computational costs can become prohibitive, particularly in optimization or uncertainty quantification tasks that require numerous model evaluations. To address this challenge, surrogate constitutive models that balance accuracy and computational efficiency are highly desirable. Data-driven surrogate models, that learn the constitutive relation directly from data, have emerged as a promising solution. In this work, we develop two local surrogate models for the viscoplastic response of a steel: a piecewise response surface method and a mixture of experts model. These surrogates are designed to adapt to complex material behavior, which may vary with material parameters or operating conditions. The surrogate constitutive models are applied to creep simulations of HT-9 steel, an alloy of considerable interest to the nuclear energy sector due to its high tolerance to radiation damage, using training data generated from viscoplastic self-consistent (VPSC) simulations. In conclusion, we define a set of test metrics to numerically assess the accuracy of our surrogate models for predicting viscoplastic material behavior, and show that the mixture of experts model outperforms the piecewise response surface method in terms of accuracy.

36 MATERIALS SCIENCE↗

NASA NTRS1987

RL10A-3-3B high mixture ratio qualification program

The results of the high mixture ratio qualification testing of the RL10 engine for the Shuttle/Centaur program are presented. The objective of the engine qualification test was to demonstrate the suitability of the RL10A-3-3B engine for space vehicle flight by subjecting it to the testing specified in RL10A-3-3B Model Specification Number 2295 dated February 1986. The applicable section of the specification is presented. Due to payload volume advantages which can be achieved by increasing the operating mixture ratio of the RL10, a decision was made to qualify the engine to run at a higher mixture ratio. A program was created to qualify the RL10 engine for operation at 15,000 pounds thrust and a nominal 6.0 to 1 mixture ratio. This model of the engine was designated the RL10A-3-3B. The qualification program included three test series as follows: (1) hardware durability and limits test in which the engine completed 23 firings and 4605.7 seconds with 1588.7 seconds at less than 6.6 mixture ratio; (2) preliminary qualification test in which the engine completed 26 firings and 5750 seconds; and (3) qualification test in which the engine completed 26 hot firings and 5693.4 seconds with 905.9 seconds at 6.7 mixture ratio. Several changes in engine hardware were required for operation of the RL10A-3-3B engine in the Space Shuttle which include a duel pressure switch ignition, an oxidizer flow control, and helium plumbing changes.

Vogel, T.↗

NASA NTRS1992

Orbit transfer rocket engine technology program: Advanced engine study

In Task D.6 of the Advanced Engine Study, three primary subtasks were accomplished: (1) design of parametric data; (2) engine requirement variation studies; and (3) vehicle study/engine study coordination. Parametric data were generated for vacuum thrusts ranging from 7500 lbf to 50,000 lbf, nozzle expansion ratios from 600 to 1200, and engine mixture ratios from 5:1 to 7:1. Failure Modes and Effects Analysis (FMEA) was used as a departure point for these parametric analyses. These data are intended to assist in definition and trade studies. In the Engine Requirements Variation Studies, the individual effects of increasing the throttling ratio from 10:1 to 20:1 and requiring the engine to operate at a maximum mixture ratio of 12:1 were determined. Off design engine balances were generated at these extreme conditions and individual component operating requirements analyzed in detail. Potential problems were identified and possible solutions generated. In the Vehicle Study/Engine Study coordination subtask, vehicle contractor support was provided as needed, addressing a variety of issues uncovered during vehicle trade studies. This support was primarily provided during Technical Interchange Meetings (TIM) in which Space Exploration Initiative (SEI) studies were addressed.

Erickson, C. M.↗

NASA NTRS1989

Design, fabrication and test of the RL10 derivative II chamber/primary nozzle

The design, fabrication and test of the RL10-II chamber/primary nozzle was accomplished as part of the RL10 Product Improvement Program (PIP). The overall goal of the RL10 PIP was to gain the knowledge and experience necessary to develop new cryogenic upper stage engines to fulfill future NASA requirements. The goal would be reached by producing an RL10 engine designed to be reusable, operate at several thrust levels, and have increased performance. The goals for the chamber/primary nozzle task were: (1) to design a reusable assembly capable of operation at increased mixture ratio and low thrust; (2) to fabricate three assemblies using new or updated techniques where possible; and (3) to test one assembly to verify the design and construction. The design and fabrication phases produced an assembly having improved features such as single piece reinforcing band segments (i.e., Mae West segments) and relocated tube exit braze joints (i.e., hooked tube exit). In addition, a computer program was developed to design the chamber tubes to meet both performance and heat transfer requirements. The test phase showed the specific impulse of the test bed engine system to be as predicted. These results, along with the heat transfer data obtained, sufficiently proved the overall design of the RL10-II recontoured and shortened chamber/primary nozzle assembly.

Marable, R. W.↗

NASA NTRS1999

A High-Resolution Thermometer for the Range 0.75-1.0 K

We report on a new high-resolution thermometer (HRT) for use near the tricritical point in 3He-4He mixtures. It is based on an existing HRT design that uses a DC-SQUID to detect the magnetization of a paramagnetic sensing element.

thermometer 3He-4He Mixtures Tricritical Point Gad↗

DOE OSTI2026

Understanding Isomeric Effects on Properties of Aviation Fuels via a Group Contribution Method: Preprint

The molecular composition of aviation fuels, including conventional and sustainable aviation fuels (SAFs), significantly influences their performance, safety, and environmental impact. This study examines the effect of isomeric variation for compounds with the same carbon number and chemical family on key fuel properties, focusing on compounds commonly found in conventional jet fuels and SAFs. A group contribution method (GCM) is employed to predict thermophysical and combustion properties, providing an efficient analytical approach to evaluate the contributions of individual compounds to overall fuel mixture behavior. As part of this work, we introduce FuelLib, an open-source Python tool built around the GCM, to calculate individual compound and fuel mixture properties using various mixing rules. Our work evaluates whether the GCM can capture isomeric effects, that are often overlooked in traditional fuel property estimation. This is particularly important for SAFs, which often are composed of a more limited set of compound classes than conventional fuels, making isomeric differences more critical. Two-dimensional gas chromatography (GCxGC) data, which can be obtained from small fuel samples, provides weight percentages of compounds grouped by chemical family and carbon number rather than detailed information about individual compounds. As a result, assumptions must be made when decomposing GCxGC data into functional groups for GCM applications. Using GCxGC data, we show that the FuelLib tool can be used to predict the fuel properties of conventional jet fuels, with validation against experimental data. The provided tool enables researchers to predict fuel properties of candidate fuels and supports the design of new SAFs at both the component and mixture levels. This capability provides a foundation for studying fuel and combustion properties during SAF development, reducing reliance on costly experimental methods and advancing progress toward certification of new SAFs.The molecular composition of aviation fuels, including conventional and sustainable aviation fuels (SAFs), significantly influences their performance, safety, and environmental impact. This study examines the effect of isomeric variation for compounds with the same carbon number and chemical family on key fuel properties, focusing on compounds commonly found in conventional jet fuels and SAFs. A group contribution method (GCM) is employed to predict thermophysical and combustion properties, providing an efficient analytical approach to evaluate the contributions of individual compounds to overall fuel mixture behavior. As part of this work, we introduce FuelLib, an open-source Python tool built around the GCM, to calculate individual compound and fuel mixture properties using various mixing rules. Our work evaluates whether the GCM can capture isomeric effects, that are often overlooked in traditional fuel property estimation. This is particularly important for SAFs, which often are composed of a more limited set of compound classes than conventional fuels, making isomeric differences more critical. Two-dimensional gas chromatography (GCxGC) data, which can be obtained from small fuel samples, provides weight percentages of compounds grouped by chemical family and carbon number rather than detailed information about individual compounds. As a result, assumptions must be made when decomposing GCxGC data into functional groups for GCM applications. Using GCxGC data, we show that the FuelLib tool can be used to predict the fuel properties of conventional jet fuels, with validation against experimental data. The provided tool enables researchers to predict fuel properties of candidate fuels and supports the design of new SAFs at both the component and mixture levels. This capability provides a foundation for studying fuel and combustion properties during SAF development, reducing reliance on costly experimental methods and advancing progress toward certification of new SAFs.

33 ADVANCED PROPULSION SYSTEMS↗