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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 1,369 records · Page 76

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NASA NTRS1981

The nature of the solar wind interaction with CO2/CO-dominated comets

The nature of the interaction of the solar wind with the ionospheres (field-free ion cavities) of comets with CO or CO2 as their dominant volatile species is considered and compared with the solar wind interaction with H2O-diominated comets. Calculations of the heliocentric variation of scale lengths defined as the nuclear distance at which the mean free path for ion-neutral collisions becomes equal to the nuclear distance, and the ion and neutral stand-off distances are presented for different modes of energy addition, nuclear radii and ionization time scales. Results indicate that whereas little activity can be expected from H2O-dominated comets at distances beyond 3 AU, COand CO2-dominated comets can be expected to be quite prolific at such distances. In contrast to H2O-dominated comets characterized by weak shocks, CO/CO2-dominated comet solar wind interactions are found to produce strong bow shocks within a specific heliocentric distance for the isothermal case of a CO-dominated comet, and a weak shock outside of this distance. In the general case, two types of cometary ionosphere transitions are found: a transition from strong to weak bow shock and from a compressible (soft) to an incompressible (hard) ionosphere, and a transition from a soft to a hard ionosphere with the bow shock remaining weak at a heliocentric distance dependant on atmospheric optical depth, bolometric albedo, nuclear radius, latent heat of sublimation of nuclear material, ionization time scale and type of heat addition. It is pointed out that the behavior of Comet Humason can be explained by solar wind interactions with a CO- or CO2-dominated comet.

Houpis, H. L. F.↗

NASA NTRS1975

Correlation of materials properties with the atomic density concept

Based on the hypothesis that the number of atoms per unit volume, accurately calculable for any substance of known real density and chemical composition, various characterizing parameters (energy levels of electrons interacting among atoms of the same or different kinds, atomic mass, bond intensity) were chosen for study. A multiple exponential equation was derived to express the relationship. Various properties were examined, and correlated with the various parameters. Some of the properties considered were: (1) heat of atomization, (2) boiling point, (3) melting point, (4) shear elastic modulus of cubic crystals, (5) thermal conductivity, and (6) refractive index for transparent substances. The solid elements and alkali halides were the materials studied. It is concluded that the number of different properties can quantitively be described by a common group of parameters for the solid elements, and a wide variety of compounds.

Source record↗

NASA NTRS1980

Lunar radionuclide records of average solar-cosmic-ray fluxes over the last ten million years

The use of cosmogenic radionuclides in lunar materials as indicators of solar cosmic ray fluxes and thus solar activity over the past 10 million years is discussed. The nature of solar and galactic cosmic ray particles and their interactions with matter are reviewed, with particular emphasis on nuclide production by cosmic-ray-induced nuclear reactions. Evidence of galactic cosmic ray flux variations from measurements of radionuclide activities in meteorites is considered which has indicated changes of less than about 25-50% over the last few million years. Measurements of radionuclide activities in lunar materials which are used to determine solar cosmic ray fluxes are then examined together with direct proton measurements indicating variations in solar fluxes with different solar cycles. It is noted that whereas average solar proton fluxes determined for the last 1-10 million years from Al-26 and Mn-53 data show little variation and are similar to recent values, lunar C-14 and Kr-81 activities indicate average solar proton fluxes several times greater over the past 10,000 to 100,000 years.

Reedy, R. C.↗

NASA NTRS1974

Status of JPL solar powered experiments for terrestrial applications

Results of an ongoing program set up to evaluate solar terrestrial photovoltaic power sources. The results of this program, which now includes a solar array encapsulant and materials test and a solar-powered buoy study, are updated, and the results of efforts to study the dynamic interaction of a solar photovoltaic array and a water electrolysis system coupled to produce hydrogen are reported for the first time.

Yasui, R. K.↗

NASA NTRS1977

The first Spacelab payload - A joint NASA/ESA venture

Planning for the 1980 qualification flight of Spacelab, which will involve a long module and one pallet, is discussed. The mission will employ two payload specialists, one sponsored by NASA and the other by ESA. Management of the Spacelab mission functions, including definition and execution of the on-board experiments, development of the experimental hardware and training of the payload specialists, is considered; studies proposed in the areas of atmospheric physics, space plasma physics, solar physics, earth observations, astronomy, astrophysics, life sciences and material sciences are reviewed. Analyses of the Spacelab environment and the Spacelab-to-orbiter and Spacelab-to-experiment interactions are also planned.

Kennedy, R.↗

NASA NTRS1978

An overview of dredging operations in the Chesapeake Bay

Maintenance of the Baltimore and the Newport News/Norfolk harbors as well as of the Chesapeake and Delaware Canal is accomplished by different dredging operations which depend on the amount and type of material to be moved, water depth, and location of disposal sites. Methods for determining the physical or chemical-biological interactive effects of these activities on the environment and on the shellfish and finfish industries on the Bay are discussed. The types of dredges used are classed according to their mode of operation.

Silver, R. H.↗

NASA NTRS1981

Remote manipulator with force feed-back

Controller for remote manipulators gives user "feel" for forces required to lift, slide, turn, and otherwise handle objects. Because operator experiences sensations similar to those he would perceive if he handled objects directly, he needs much less skill and training for manipulator than for one with force feedback. It was developed to handle hazardous materials, such as radioactive substances, explosives, or corrosive chemicals. Other possible uses include tracking moving objects, vehicle control, and human interaction with computers (for example, via three dimensional display of computer model).

Hill, J. W.↗

NASA NTRS1983

Aeroacoustic research facilities at NASA Langley Research Center: Description and operational characteristics

A number of facilities were developed which provide unique test capabilities for aeroacoustic research. Information regarding physical layouts, dimensions, construction features, and operating capabilities of these facilities is compiled. Possible research applications include the behavior of such noise sources as jets, rotors, and propellers in simulated forward motion; studies of noise due to the interactions of aerodynamic flows with solid surfaces and bodies; sound propagation in ducts with airflow; and the evaluation of acoustical materials.

Hubbard, H. H.↗

NASA NTRS1985

Investigation of semiconductor clad optical waveguides

A variety of techniques have been proposed for fabricating integrated optical devices using semiconductors, lithium niobate, and glasses as waveguides and substrates. The use of glass waveguides and their interaction with thin semiconductor cladding layers was studied. Though the interactions of these multilayer waveguide structures have been analyzed here using glass, they may be applicable to other types of materials as well. The primary reason for using glass is that it provides a simple, inexpensive way to construct waveguides and devices.

Batchman, T. E.↗

NASA NTRS1983

Correlation of infrared reflectance ratios at 2.3 microns/1.6 micron and 1.1 micron/1.6 micron with delta O-18 values delineating fossil hydrothermal systems in the Idaho batholith

Reflectance ratios from laboratory spectra and airborne multispectral images are found to be strongly correlated with delta O-18 values of granite rocks in the Idaho batholith. The correlation is largely a result of interactions between hot water and rock, which lowered the delta O-18 values of the rocks and produced secondary hydrous material. Maps of the ratio of reflectivities at 2.3 and 1.6 microns should delineate fossil hydrothermal systems and provide estimates of alteration intensity. However, hydrous minerals produced during deuteric alteration or weathering cannot be unambiguously distinguished in remotely sensed images from the products of propylitic alteration without the use of narrow-band scanners. The reflectivity at 1.6 micron is strongly correlated with rock density and may be useful in distinguishing rock types in granitic terranes.

Gillespie, A. R.↗

NASA NTRS1989

Mass transfer during ice particle collisions in planetary rings

Experimental results are presented from laboratory environment simulations of the ice particle collisional properties defining the structure and dynamical evolution of planetary rings. It is inferred from these data that there is a dependence of the interacting volume on the impact velocity. Although the volume fraction exchanged during a collision is small, the net amount of material transferred can be substantially smaller. Attention is given to the implications of these determinations for planetary ring structure and evolution.

Mcdonald, J. S. B.↗

NASA NTRS1996

Investigation of Natural and Man-Made Radiation Effects on Crews on Long Duration Space Missions

Over the past several years, NASA has studied a variety of mission scenarios designed to establish a permanent human presence on the surface of Mars. Nuclear electric propulsion (NEP) is one of the possible elements in this program. During the initial stages of vehicle design work, careful consideration must be given to not only the shielding requirements of natural space radiation, but to the shielding and configuration requirements of the on-board reactors. In this work, the radiation transport code MCNP has been used to make initial estimates of crew exposures to reactor radiation fields for a specific manned NEP vehicle design. In this design, three 25 MW(sub th), scaled SP-100-class reactors are shielded by three identical shields. Each shield has layers of beryllium, tungsten, and lithium hydride between the reactor and the crew compartment. Separate calculations are made of both the exiting neutron and gamma fluxes from the reactors during beginning-of-life, full-power operation. This data is then used as the source terms for particle transport in MCNP. The total gamma and neutron fluxes exiting the reactor shields are recorded and separate transport calculations are then performed for a 10 g/sq cm crew compartment aluminum thickness. Estimates of crew exposures have been assessed for various thicknesses of the shield tungsten and lithium hydride layers. A minimal tungsten thickness of 20 cm is required to shield the reactor photons below the 0.05 Sv/y man-made radiation limit. In addition to a 20-cm thick tungsten layer, a 40-cm thick lithium hydride layer is required to shield the reactor neutrons below the annual limit. If the tungsten layer is 30-cm thick, the lithium hydride layer should be at least 30-cm thick. These estimates do not take into account the photons generated by neutron interactions inside the shield because the MCNP neutron cross sections did not allow reliable estimates of photon production in these materials. These results, along with natural space radiation shielding estimates calculated by NASA Langley Research Center, have been used to provide preliminary input data into a new Macintosh-based software tool. A skeletal version of this tool being developed will allow rapid radiation exposure and risk analyses to be performed on a variety of Lunar and Mars missions utilizing nuclear-powered vehicles.

Bolch, Wesley E.↗

NASA NTRS2000

Laser Time-of-Flight Mass Spectrometry for Space

A miniature reflection time-of-flight mass spectrometer for in situ planetary surface analysis is described. The laser ablation mass spectrometer (LAMS) measures the regolith's elemental and isotopic composition without high-voltage source extraction or sample preparation. The compact size (< 2 x 10(exp 3) cubic cm) and low mass (approximately 2 kg) of LAMS, due to its fully coaxial design and two-stage reflectron, fall within the strict resource limitations of landed science missions to solar system bodies. A short-pulse laser focused to a spot with a diameter approximately 30-50 micrometers is used to obtain microscopic surface samples. Assisted by a microimager, LAMS can interactively select and analyze a range of compositional regions (with lateral motion) and with repeated pulses can access unweathered, subsurface materials. The mass resolution is calibrated to distinguish isotopic peaks at unit masses, and detection limits are on resolved to a few ppm. The design and calibration method of a prototype LAMS device is described, which include the development of preliminary relative sensitivity coefficients for major element bulk abundance measurements.

Brinckerhoff, W. B.↗

NASA NTRS2012

Rugged, Portable, Real-Time Optical Gaseous Analyzer for Hydrogen Fluoride

Hydrogen fluoride (HF) is a primary evolved combustion product of fluorinated and perfluorinated hydrocarbons. HF is produced during combustion by the presence of impurities and hydrogen- containing polymers including polyimides. This effect is especially dangerous in closed occupied volumes like spacecraft and submarines. In these systems, combinations of perfluorinated hydrocarbons and polyimides are used for insulating wiring. HF is both highly toxic and short-lived in closed environments due to its reactivity. The high reactivity also makes HF sampling problematic. An infrared optical sensor can detect promptly evolving HF with minimal sampling requirements, while providing both high sensitivity and high specificity. A rugged optical path length enhancement architecture enables both high HF sensitivity and rapid environmental sampling with minimal gaseous contact with the low-reactivity sensor surfaces. The inert optical sample cell, combined with infrared semiconductor lasers, is joined with an analog and digital electronic control architecture that allows for ruggedness and compactness. The combination provides both portability and battery operation on a simple camcorder battery for up to eight hours. Optical detection of gaseous HF is confounded by the need for rapid sampling with minimal contact between the sensor and the environmental sample. A sensor is required that must simultaneously provide the required sub-parts-permillion detection limits, but with the high specificity and selectivity expected of optical absorption techniques. It should also be rugged and compact for compatibility with operation onboard spacecraft and submarines. A new optical cell has been developed for which environmental sampling is accomplished by simply traversing the few mm-thick cell walls into an open volume where the measurement is made. A small, low-power fan or vacuum pump may be used to push or pull the gaseous sample into the sample volume for a response time of a few seconds. The optical cell simultaneously provides for an enhanced optical interaction path length between the environmental sample and the infrared laser. Further, the optical cell itself is comprised of inert materials that render it immune to attack by HF. In some cases, the sensor may be configured so that the optoelectronic devices themselves are protected and isolated from HF by the optical cell. The optical sample cell is combined with custom-developed analog and digital control electronics that provide rugged, compact operation on a platform that can run on a camcorder battery. The sensor is inert with respect to acidic gases like HF, while providing the required sensitivity, selectivity, and response time. Certain types of combustion events evolve copious amounts of HF, very little of other gases typically associated with combustion (e.g., carbon monoxide), and very low levels of aerosols and particulates (which confound traditional smoke detectors). The new sensor platform could warn occupants early enough to take the necessary countermeasures.

Pilgrim, Jeffrey↗

NASA NTRS2017

CFD Simulations of the IHF Arc-Jet Flow: Compression-Pad/Separation Bolt Wedge Tests

This paper reports computational analyses in support of two wedge tests in a high enthalpy arc-jet facility at NASA Ames Research Center. These tests were conducted using two different wedge models, each placed in a free jet downstream of a corresponding different conical nozzle in the Ames 60-MW Interaction Heating Facility. Panel test articles included a metallic separation bolt imbedded in the compression-pad and heat shield materials, resulting in a circular protuberance over a flat plate. As part of the test calibration runs, surface pressure and heat flux measurements on water-cooled calibration plates integrated with the wedge models were also obtained. Surface heating distributions on the test articles as well as arc-jet test environment parameters for each test configuration are obtained through computational fluid dynamics simulations, consistent with the facility and calibration measurements. The present analysis comprises simulations of the non-equilibrium flow field in the facility nozzle, test box, and flow field over test articles, and comparisons with the measured calibration data.

TPS↗

NASA NTRS2018

New Technologies Advancing Thermophysics

Researchers at NASA Ames in California have built a new facility that uses multiple 50-kW continuous wave lasers to add the capability for simulating radiative heating on thermal protection materials. The new facility, the Laser Enhanced Arc-jet Facility (LEAF-Lite), was added to NASA Ames’s Interaction Heating Facility arc-jet and now allows for test articles to be heated by both convective and radiative heat flux, making the facility more like flight. Using this new system, researchers can now simulate radiant heating with the laser and convective heating with the arc-jet simultaneously on a single test article. During its initial test in October 2017, the lasers radiatively heated a 6” x 6” Avcoat wedge sample to 405 W/sq.cm while the arc-jet simultaneously provided 160 W/sq.cm of convective heat, resulting in a total heat flux of 565 W/sq.cm. Radiative heating is more prevalent in missions with higher atmospheric entry speeds like the Orion space capsule or interplanetary scientific probes. Later this year, scientists will expand the spot size to cover 17” x 17” to test an Orion TPS panel.

Brandis, Aaron↗

NASA NTRSDate not supplied

Recent Advances in LIBS for Real-Time Detection of Silicone Contaminants on CFRP Surfaces

Laser induced breakdown spectroscopy (LIBS) is a materials characterization technique that has been advanced and refined to provide in situ, real-time quality control of carbon fiber reinforced polymer (CFRP) surfaces. As part of an effort to improve process control for adhesive bonding, a LIBS system was designed and assembled at NASA Langley Research Center (LaRC) to enable detection of ultralow concentrations of silicone contamination on CFRP adherends. The LIBS instrument provides high sensitivity detection and quasi-nondestructive surface characterization of CFRP adherends prior to adhesive bonding. This review focuses on the advancements at LaRC using LIBS as a quality control tool for the detection of silicone contaminants for improved adhesive bonding reliability of CFRP materials. This work describes how the LIBS technique was advanced by analyzing the laser parameters, studying the laser-matter interactions, and performing time-resolved measurements to determine the optimal plasma conditions for elemental detection. In addition, LIBS results were compared to X-ray photoelectron spectroscopy data to enable quantitative analysis from analytical calibration curves. Examples are shown of how to perform surface mapping of silicone contamination. Finally, a brief discussion is also presented on LIBS instrumentation, recommendations for laser parameters and instrumentation components, and LIBS technique maturity.

Surface characterization, Carbon fiber reinforced ↗

NASA NTRSDate not supplied

Recent Advances in LIBS for Real-Time Detection of Silicone Contaminants on CFRP Surfaces

Laser induced breakdown spectroscopy (LIBS) is a materials characterization technique that has been advanced and refined to provide in situ, real-time quality control of carbon fiber reinforced polymer (CFRP) surfaces. As part of an effort to improve process control for adhesive bonding, aLIBS system was designed and assembled at the NASA Langley Research Center (LaRC) to enable detection of ultra low concentrations of silicone contamination on CFRP adherends. The LIBS instrument provides high sensitivity detection and quasi-nondestructive surface characterization ofCFRP adherends prior to adhesive bonding. This review focuses on the advancements at LaRC using LIBS as a quality control tool for the detection of silicone contaminants for improved adhesive bonding reliability of CFRP materials. This work describes how the LIBS technique was advanced by analyzing the laser parameters, studying the laser-matter interactions, and performing time-resolved measurements to determine the optimal plasma conditions for elemental detection. In addition, LIBS results were compared to X-ray photoelectron spectroscopy data to enable quantitative analysis from analytical calibration curves. Examples are shown of how to perform surface mapping of silicone contamination. Finally, a brief discussion is presented on LIBS instrumentation, recommendations for laser parameters and instrumentation components, and LIBS technique maturity

Rodolfo I. Ledesma↗