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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The Magneto-optical Filter, Working Principles and Recent Progress

The Magneto-Optical Filter is described which allows simultaneous magnetic and velocity measurements (in both imaging and non-imaging modes) without the need for a spectrograph. In this way the stability and alignment problems of the spectrograph are completely overcome. Its major advantages are: wavelength absolute reference and stability, high signal to noise ratio and independence of the transmission profile from the incidence angle of the solar beam. It is an imaging instrument allowing high wave number analysis in the solar oscillation spectrum and a continuous monitoring of the image position through the chromospheric facular structures. The apparatus in use at Mt. Wilson is assembled in a modular form. The most important part of it is a glass cell containing the sodium vapor. The filter is easy to use but the cell is not easy to construct in an optimal way. The technology is in progress both to use Na and K together and to prevent the windows from becoming coated during a long-term operation.

Cacciani, A.↗
NASA NTRS1986

Modeling of transient heat pipe operations

An analysis of the steady, compressible, one-dimensional, laminar flow of sodium vapor is presented for a case of a flat plate-type heat pipe with asymmetrical boundary conditions. In addition, shear stress at the liquid-vapor interface, variations of vapor quality, and momentum and energy factors are considered. A similarity solution for a semiporous channel is used to provide the velocity profile at cross sections.

Colwell, Gene T.↗
NASA NTRS1986

Sputtering of sodium on the planet Mercury

It is shown here that ion sputtering cannot account for the observed neutral sodium vapor column density on Mercury, but that it is an important loss mechanism for Na. Photons are likely to be the dominant stimulus, both directly through photodesorption and indirectly through thermal desorption of absorbed Na. It is concluded that the atmosphere produced is characterized by the planet's surface temperature, with the ion-sputtered Na contributing to a lesser, but more extended, component of the atmosphere.

Mcgrath, M. A.↗
NASA NTRS1987

AMTEC electrode development

The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion device, utilizing a high sodium vapor pressure or activity ratio across a beta-alumina solid electrolyte. Progress is reported on a long life, high power, porous electrode. Two electrode compositions were identified which have the potential for long life operation at power densities above 0.5 W/sq cm. Longer lifetime testing is being initiated. Successful optimization and demonstration of very long lifetimes for these electrodes will be a major step toward establishing the feasibility of AMTEC space power systems.

Bankston, C. P.↗
NASA NTRS1988

Recent advances in Alkali Metal Thermoelectric Converter (AMTEC) electrode performance and modeling

The Alkali Metal Thermoelectric Converter (AMTEC) is a direct energy conversion device, utilizing a high sodium vapor pressure or activity ratio across a beta-double prime-alumina solid electrolyte (BASE). This paper describes progress on the remaining scientific issue which must be resolved to demonstrate AMTEC feasibility for space power systems: a stable, high power density electrode. Two electrode systems have recently been discovered at JPL that now have the potential to meet space power requirements. One of these is a very thin sputtered molybdenum film, less than 0.5 micron thick, with overlying current collection grids. This electrode has experimentally demonstrated stable performance at 0.4-0.5 W/sq cm for hundreds of hours. Recent modeling results show that at least 0.7 W/sq cm can be achieved. The model of electrode performance now includes all loss mechanisms, including charge transfer resistances at the electrode/electrolyte interface. A second electrode composition, cosputtered platinum/tungsten, has demonstrated 0.8 W/sq cm for 160 hours. Systems studies show that a stable electrode performance of 0.6 W/sq cm will enable high efficiency space power systems.

Bankston, C. P.↗
NASA NTRS1990

Heat pipes for wing leading edges of hypersonic vehicles

Wing leading edge heat pipes were conceptually designed for three types of vehicle: an entry research vehicle, aero-space plane, and advanced shuttle. A full scale, internally instrumented sodium/Hastelloy X heat pipe was successfully designed and fabricated for the advanced shuttle application. The 69.4 inch long heat pipe reduces peak leading edge temperatures from 3500 F to 1800 F. It is internally instrumented with thermocouples and pressure transducers to measure sodium vapor qualities. Large thermal gradients and consequently large thermal stresses, which have the potential of limiting heat pipe life, were predicted to occur during startup. A test stand and test plan were developed for subsequent testing of this heat pipe. Heat pipe manufacturing technology was advanced during this program, including the development of an innovative technique for wick installation.

Boman, B. L.↗
NASA NTRS1991

Utilization of lunar ilmenite: Basalt or regolith?

A critical discussion of whether lunar basalt or regolith should be used as a resource for mineral processing schemes on the lunar surface, with pros and cons for each argument is presented. A literature review has shown that the majority of authors feel that mining the lunar basalt, crushing it, and then processing to remove the desired minerals, would be the route to take. The argument that this method would not be a sound mineral processing practice is presented. Mining and crushing are difficult propositions even on Earth; to attempt such processes in the hostile lunar environment would be a phenomenal task. It would be better to start with a simpler scheme, such as processing the regolith, which can be adapted to the multitude of unknowns facing the first lunar production plant. If, however, the lunar mining trend is followed, it must be kept in mind that mining and processing technology which is radically different from what is currently available and used on Earth will have to be developed. Podnieks and Roepke (1987) and Lindroth and Podnieks (1987) have summarized the new technology that may be applicable, but this technology is very similar to the current, 99 percent inefficient technology used on Earth. One such possible technique is sodium vapor fragmentation of basalt. Initial testwork was conducted at Michigan Technological University on terrestrial basalt with extremely promising results, though much time and effort will be needed to fully develop this process.

Kawatra, S. K.↗
NASA NTRS1959

A 20,000-Kilowatt Nuclear Turboelectric Power Supply for Manned Space Vehicles

A conceptual design of a nuclear turboelectric powerplant, producing 20,000 kilowatts of power suitable for manned space vehicles is presented. The study indicates that the radiator necessary for rejecting cycle waste heat is the dominant weight, and emphasis is placed on the selection of cycle operating conditions in order to reduce this weight. A thermodynamic cycle using sodium vapor as the working fluid and operating at a turbine-inlet temperature of 2500 R was selected. The total powerplant weight was calculated to be approximately 6 pounds per kilowatt. The radiator contributes approximately 2.1 pounds per kilowatt to the total weight and the reactor and reactor shield contribute approximately 0.24 and 1.2 pounds per kilowatt, respectively. The generator, turbine, and piping add significantly to the total weight (between 0.5 and 0.6 lb/kw), but the heat exchanger, pumps, and so on are less important. Several important research areas associated with the development of a reliable nuclear turboelectric powerplant of the type analyzed are discussed.

English, Robert E.↗
NASA NTRS2000

Testing Plant Responses to Rarified Atmospheres for Inflatable Greenhouses

Reduced atmospheric pressures will likely be used to minimize mass and engineering requirements for plant growth habitats used in extraterrestrial applications. A chamber with high vacuum capability was used to design and begin construction of a system for testing plant responses to reduced pressure atmospheres. Several preliminary tests were conducted to evaluate chamber suitability for plant tests and to determine performance of thermal and vacuum systems at ambient and reduced pressure atmospheres down to 0.1 atm. The first tests consisted of measurements of internal gas volume and leakage rate. The method for volume determination was quite sensitive and will be needed for plant gas exchange measurements and calculations. This information will also be used in conjunction with the leak rate. Measured leak rates on the order of 0.46 mm Hg/min at 76 mm Hg pressure are low enough to conduct sensitive carbon dioxide exchange rate measurements at reduced pressure given an adequate plant sample (0.5 to 1.0 sq m area). A test rack with lighting provided by three high-pressure sodium vapor lamps was built to accommodate both short-term and long-term plant responses. Initial short-term experiments with lettuce showed that a pressure of 77 mm Hg resulted in a 6.1-fold increase in the rate of water loss compared to water loss at ambient pressure. Plants were severely wilted after 30 minutes exposure to 77 mm Hg. Water loss was found to be inversely correlated with atmospheric pressure over the range of pressures from 0.2 to 1.0 atm; the rate of water loss at 0.2 atm was 4.3 times higher than water loss at ambient pressure. Older leaves showed moderate wilting during exposure to 156 mm Hg, but those exposed to 345 mm, Hg remained turgid. Results suggest a reduced atmospheric pressure limit of 0.2 to 0.3 atm for lettuce grown in a solid medium. Follow-up experiments with carbon dioxide control and control at high relative humidity (> 90 %) will be needed to further confirm and define safe reduced pressure limits that are feasible for plant tolerance and growth.

Corey, Kenneth A.↗
NASA NTRS2001

Gas-Phase Combustion Synthesis of Nonoxide Nanoparticles in Microgravity

Gas-phase combustion synthesis is a promising process for creating nanoparticles for the growing nanostructure materials industry. The challenges that must be addressed are controlling particle size, preventing hard agglomerates, maintaining purity, and, if nonoxides are synthesized, protecting the particles from oxidation and/or hydrolysis during post-processing. Sodium-halide Flame Encapsulation (SFE) is a unique methodology for producing nonoxide nanoparticles that addresses these challenges. This flame synthesis process incorporates sodium and metal-halide chemistry, resulting in nanoparticles that are encapsulated in salt during the early stages of their growth in the flame. Salt encapsulation has been shown to allow control of particle size and morphology, while serving as an effective protective coating for preserving the purity of the core particles. Metals and compounds that have been produced using this technology include Al, W, Ti, TiB2, AlN, and composites of W-Ti and Al-AlN. Oxygen content in SFE synthesized nano- AlN has been measured by neutron activation analysis to be as low as 0.54wt.%, as compared to over 5wt.% for unprotected AlN of comparable size. The overall objective of this work is to study the SFE process and nano-encapsulation so that they can be used to produce novel and superior materials. SFE experiments in microgravity allow the study of flame and particle dynamics without the influence of buoyancy forces. Spherical sodium-halide flames are produced in microgravity by ejecting the halide from a spherical porous burner into a quiescent atmosphere of sodium vapor and argon. Experiments are performed in the 2.2 sec Drop Tower at the NASA-Glenn Research Center. Numerical models of the flame and particle dynamics were developed and are compared with the experimental results.

Axelbaum, R. L.↗
NASA NTRS2000

Plant Responses to Rarified Atmospheres

Reduced atmospheric pressures will likely be used to minimize mass and engineering requirements for plant growth habitats used in extraterrestrial applications. This report provides a brief survey of key literature related to responses of plants to atmospheric variables and a broad rationale for designing minimal atmospheres for future plant growth structures on the Martian surface. The literature and recent work suggest that atmospheric pressure limits for normal plant function are likely to be 10 kPa or perhaps slightly lower. At Kennedy Space Center, a chamber with high vacuum capability was used to design and begin construction of a system for testing plant responses to reduced pressure atmospheres. A test rack with lighting provided by 3, high-pressure sodium vapor lamps was built to conduct measurements of short-term plant responses. Initial experiments with lettuce showed that a pressure of 10 kPa resulted in a 6.1-fold increase in the rate of water loss compared to water loss at ambient pressure (101 kPa).

Corey, Kenneth A.↗
NASA NTRS2003

Annealing Would Improve beta" - Alumina Solid Electrolyte

A pre-operational annealing process is under investigation as a potential means of preventing a sudden reduction of ionic conductivity in a Beta"-alumina solid electrolyte (BASE) during use. On the basis of tests, the sudden reduction of ionic conductivity, followed by a slow recovery, has been found to occur during testing of the solid electrolyte and electrode components of an alkali metal thermal-to-electric converter (AMTEC) cell. At this time, high-temperature tests of limited duration have indicated the superiority of the treated BASE, but reproducible tests over thousands of hours are necessary to confirm that microcracking has been eliminated. The ionic conductivity of the treated BASE is also measured to be higher than untreated BASE at 1,073 K in low-pressure sodium vapor. Microcracking resulting in loss of conductivity was not observed with treated BASE in one high-temperature experiment, but this result must be duplicated over very long testing times to be sure of the effect. Shorter annealing times (10 to 20 hours) were found to result in significantly less loss of mass; it may be necessary for the packed powder mixture to evolve some Na2O before the Na2O can leave the ceramic.

Williams, Roger↗
DOE OSTI2024

Thermochemical Modeling of Radionuclide Vapor-Liquid Equilibria in Sodium Pools for SFR Mechanistic Source Term Analysis

Mechanistic source term (MST) analysis of sodium fast reactors (SFR) requires understanding of various radionuclide (RN) transport phenomena influencing potential releases from the fuel to the environment. One such phenomenon includes the retention or release of RNs from the sodium coolant pool, representing the step after possible fuel failures and influencing transport to the cover gas region. Thermodynamic vapor-liquid equilibria (VLE) calculations were performed on systems representing SFR sodium pools containing oxygen impurities and radionuclide (RN) inventories. First, an assessment and recreation of a previously developed thermodynamic database was completed, including updates to thermodynamic parameters. The RN inventories used in VLE calculations represented hypothetical source terms that might be released to the pool during previously analyzed fuel failure scenarios. The calculations were performed for all possible combinations of sodium pool size (i.e., total oxygen) and number of failed fuel pins (i.e., total RNs). In this way, multiple ratios of the RN relative to the oxygen impurity (RN:O) were compared for their impact on RN volatility, which is discussed in terms of the vapor fraction (VF), defined as the fraction of the RN that is calculated to exist in the vapor phase at equilibrium above condensed phases of that element. Similar trends in VLE behavior are seen in the equilibrium calculation results for elements of similar chemistry, and for some element types, it was found that the RN:O ratio can be important due to oxide formation, which typically exist in the condensed phase.

Shahbazi, Shayan↗
DOE OSTI2025

Mechanisms Engineering Test Loop (METL) Operations, Maintenance, and Testing - FY2025

This report documents the operations, maintenance, and improvements that were performed at the Mechanisms Engineering Test Loop (METL) and its supporting infrastructure during FY2024. The METL facility had a very successful seventh year of operations while supporting the testing of multiple test article experiments in the facility. The METL facility continued supporting the Gear Test Assembly (GTA) testing and the Thermal Hydraulic Experimental Test Article (THETA) with the full testing with both the primary and secondary systems. Work to accommodate two additional experiments, a flow sensor test article (F-STAr) gripper test and a fuel handling gripper test article (GrTA) continued as they are expected to undergo testing in METL in FY2025. In addition, a new 18” test article, the Sample Testing Basket (STB) was used a few times to provide screening tests for sodium service materials. A fifth test vessel was installed in the location of Test Vessel 6, and a wet vapor nitrogen sodium processing system was developed and initially tested.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1989

Interaction of a sodium ion with the water liquid-vapor interface

Molecular dynamics results are presented for the density profile of a sodium ion near the water liquid-vapor interface at 320 K. These results are compared with the predictions of a simple dielectric model for the interaction of a monovalent ion with this interface. The interfacial region described by the model profile is too narrow and the profile decreases too abruptly near the solution interface. Thus, the simple model does not provide a satisfactory description of the molecular dynamics results for ion positions within two molecular diameters from the solution interface where appreciable ion concentrations are observed. These results suggest that surfaces associated with dielectric models of ionic processes at aqueous solution interfaces should be located at least two molecular diameters inside the liquid phase. A free energy expense of about 2 kcal/mol is required to move the ion within two molecular layers of the free water liquid-vapor interface.

NASA Center ARC↗
NASA NTRS1969

Performance of low-pressure thermionic converters is evaluated

Experiments, evaluating the performance of low-pressure thermionic converters, were conducted with cesium, potassium, and sodium-metal vapors. The results of the investigation are useful in the selection of favorable conditions for the design of thermionic reactor fuel elements, including RF output for special applications.

Richards, H. K.↗