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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 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Silicon carbide-silicon nitride fibers: Preparation and characterization of polycarbosilazane precursors

This study examines the effect of modifications of the chemical structure of the monomers on the properties of the polymeric precursor and and ceramic fibers. A group of silaneamines, R'-Si (NH-R) sub 3, taken from the series where R' is methyl or phenyl and R is n-propyl, n-butyl, phenyl or allyl, are converted to polycarbosilazanes by heating in excess of 500 C. Resins obtained from this polymerization are characterized by NMR and IR spectroscopy and GPC. Each resin is tested for fiber-forming properties. Resin samples and fibers are hydrolytically cured. Thermogravimetric analyses are conducted on the cured resins to compare the relative thermal stability and examine the pyrolysis process. Cured fibers are tested for tensil strength.

Crouse, D. J.↗
NASA NTRS1984

Alternative Food Preservation Techniques, New Technology in Food Preparation and Appropriateness of Food Supply for the Permanently Manned Space Station

Alternative food preservation techniques are defined as unique processes and combinations of currently used processes for food preservation. Food preservation is the extension of the useful shelf-life of normally perishable foods (from harvest to final consumption) by controlling micro-organisms, enzymes, chemical changes, changes in sensory characteristics and the prevention of subsequent recontamination. The resulting products must comply with all applicable food manufacturing practice regulations and be safe. Most of the foods currently used in both space and military feeding are stabilized either by dehydration or the use of a terminal sterilization process. Other available options would be formulation to reduce water activity, the refrigeration and freezing of perishable foods, chemical addition, and physical treatment (ionizing or nonionizing radiation or mechanical action). These alternatives are considered and proposals made.

Richard H. Whelan↗
NASA NTRS1985

Preparative electrophoresis of cultured human cells: Effect of cell cycle phase

Human epithelioid T-1E cells were cultured in suspension and subjected to density gradient electrophoresis upward in a vertical column. It is indicated that the most rapidly migrating cells were at the beginning of the cell cycle and the most slowly migrating cells were at the end of the cell cycle. The fastest migrating cells divided 24 hr later than the slowest migrating cells. Colonies developing from slowly migrating cells had twice as many cells during exponential growth as did the most rapidly migrating cells, and the numbers of cells per colony at any time was inversely related to the electrophoretic migration rate. The DNA measurements by fluorescence flow cytometry indicates that the slowest migrating cell populations are enriched in cells that have twice as much DNA as the fastest migrating cells. It is concluded that electrophoretic mobility of these cultured human cells declines steadily through the cell cycle and that the mobility is lowest at the end of G sub 2 phase and highest at the beginning of G sub 1 phase.

Kunze, M. E.↗
NASA NTRS1985

Pre-flight report on cultured human embryonic kidney cell handling and cell electrophoresis. Prepared prior to continuous-flow electrophoretic separation experiments aboard space shuttle flight STS-8

Studies of the physical properties of continuous-flow zero-G electrophoretic separator (CFES) buffer, the electrokinetic properties of human erythrocytes in the CFES buffer, the electrokinetic properties of human embryonic kidney cells in the CFES buffer, and the viability and yield of human embryonc kidney cells subjected to flight handling procedures are discussed. In general, the procedure for cell handling and electrophoresis of HEK-8514 cells in 1st or 2nd passage on STS-8 is acceptable if executed properly. The CFES buffer has ionic strength that is barely compatible with cell viability and membrane stability, as seen in experiments with human erythrocytes and trypan-blue staining of human kidney cells. Cells suspended in 10% dialysed horse serum for 3 days in the cold appear to be more stable than freshly trypsinized cells. 10% horse serum appears to be superior to 5% horse serum for this purpose. The mean absolute raw mobility of HEK-8514 cells in CFES buffer at 6 degrees, conductivity 0.055 mmho/cm, is 1.1 to 1.4 um-cm/V-sec, with a range of nearly a whole mobility unit.

Todd, P. W.↗
NASA NTRS1985

Remarks on preparation of indandione detection reagents

A modified Claisen condensation with sliced sodium at a higher temperature was recommended for the production of ungranulated charcoal. A new ninhydrin production method by oxidation of benzaldiketohydrinden using available reagents was tried and was unsuccessful. Triketohydrinden was obtained by boiling ninhydrin in acetic acid anhydrides.

Stepan, J.↗
NASA NTRS1985

Voyager flight engineering - Preparing for Uranus

Two Voyager spacecraft are currently engaged in exploration of the outer solar system with Voyager 2 scheduled to conduct the first close-up investigation of the planet Uranus during the period November 4, 1985 through March 3, 1986. Flight engineering for the Voyager project has the objectives of delivering a functioning spacecraft containing observing sequences to the right places at the right times. Due to the changing environment as the mission has progressed outward from Jupiter to Saturn to Uranus (and on to Neptune), this engineering task has included the development of significant new capabilities. The paper utilizes the case-study method to examine some new spacecraft capabilities in three subsystems: data, attitude and articulation control, and power. The implementation of a new navigational data-type, delta DOR, is also reviewed. An overview is given of the Voyager sequencing process for the cruise and encounter phases with a case study focusing on late updating of part of the near encounter sequence. The prospective mission to Neptune is previewed.

Mclaughlin, W. I.↗
NASA NTRS1984

A morphological study of silicon carbide prepared by chemical vapor deposition

Surface morphologies of SiC deposits obtained via chemical vapor deposition (CVD) were studied as functions of substrate surface temperature and the concentration of the silicon and carbon source material, methyltrichlorosilane. Substrates of graphite and alpha-SiC crystals were used. Explanations of the observed morphologies on graphite substrates and their marked changes with temperature are given in terms of chemical kinetics and mass transport arguments. The results of thermodynamic calculations were used to help explain the observed morphologies of the deposits on alpha-SiC substrates.

Tsui, P.↗
NASA NTRS1986

Preparation, analysis and release of simulated interplanetary grains into low Earth orbit

Astronomical observations which reflect the optical and dynamical properties of interstellar and interplanetary grains are the primary means of identifying the shape, size, and the chemistry of extraterrestrial grain materials. Except for recent samplings of extraterrestrial particles in near-Earth orbit and in the stratosphere observations were the only method of deducing the properties of extraterrestrial particles. In order to elucidate the detailed characteristics of observed dust, the observations must be compared with theoretical studies, some of which are discussed in this volume, or compared with terrestrial laboratory experiments. The formation and optical characterization of simulated interstellar and interplanetary dust with particular emphasis on studying the properties on irregularly shaped particles were discussed. Efforts to develop the techniques to allow dust experiments to be carried out in low-Earth orbit were discussed, thus extending the conditions under which dust experiments may be performed.

Stephens, J. R.↗
NASA NTRS1986

The preparation of new perfluoroether fluids exhibiting excellent thermal-oxidative stabilities

A series of low molecular weight perfluoroalkylethers (PFAE) were synthesized by direct fluorination. Viscosity-temperature properties and oxidation stabilities were determined. Viscosity-temperature correlations indicated that increases in branching and increases in the size of the branching substituent caused a deterioration in viscometric properties (i.e., an increase in ASTM slope). In addition, increasing the ratio of carbon to oxygen in these compounds also increased the ASTM slope. Preliminary oxidation stability tests indicated that highly branched PFAE fluids. (i.e., those containing quaternary carbons) may be less stable than either those containing a single trifluoromethyl pendant group or those containing no branching at all.

Jones, W. R., Jr.↗
NASA NTRS1985

Preparation for microgravity science investigation of compound semiconductor crystal growth

Preparatory work on Bridgman directional solidification (BDS) of PbSnTe crystals prior to microgravity crystal growth experiments on Shuttle flights are reported. Gravitational effects become important in crystal growth when density gradients are present. The situation is critical in BDS of PbSnTe because of the necessity of obtaining homogeneous compositional distributions, which can be disturbed when convective processes occur. Numerical models have been defined which quantify the effects of convection in the crystal growth solution. The models were verified by earth-based crystal-growth tests in a two-zone furnace using equal concentrations of each of the elements. Data are provided to demonstrate the differences in composition among crystals grown at different orientations to the gravitational field vector.

Fripp, A. L.↗
NASA NTRS1986

High-efficiency broad-area single-quantum-well lasers with narrow single-lobed far-field patterns prepared by molecular beam epitaxy

Broad-area single-quantum-well graded-index waveguide separate-confinement heterostructure lasers were fabricated by molecular beam epitaxy. A high external quantum efficiency of 79 percent and stable, single-lobed far-field patterns with a beam divergence as narrow as 0.8 deg (1.9 times diffraction limit) for a 100 micron-wide laser were obtained under pulsed conditions.

Larsson, A.↗
NASA NTRS1984

Preparing for the unexpected - A psychologist's case for improved training

In the procedures designed to minimize human errors that lead to aircraft incidents, the improved human factor engineering and automation approaches must be supplemented by new training methods. Changes are suggested in the preprogrammed training principles which are currently based almost exclusively on the procedures-oriented environment, with insufficient training for cognitive processing and awareness. Use of the Line-Oriented Flight Training procedure, in which a training simulator is supplemented by a highly structured script or scenario to simulate the total line operational environment for the purpose of simultaneously training the entire flight crew, offers one way of providing pilots and other crewmembers with the experience of dealing with unexpected or stressful events. Of primary importance is maximal coordination between the aircraft captain and other crewmembers during the flight, which puts emphasis on the importance of teamwork and personal relations among all other crewmembers. The current FARs governing training and proficiency will have to be modified to accommodate new training appoaches.

Foushee, H. C.↗
NASA NTRS1985

Microgravity associated changes in pituitary growth hormone (GH) cells prepared from rats flown on Space Lab 3

The effect of microgravity on the release of pituitary growth hormone (GH) in rats is studied. The pituitary glands from six adult rats exposed to microgravity are analyzed for in vitro and in vivo changes in pituitary growth hormone cells. The GH cell functions in the somatotrophs of flight rats are compared to a control group. The two assay procedures employed in the experiment are described. It is observed that intracellular levels of GH are two to three times greater in the flight rats than in the control group; however, the amount of GH released from the somatotrophs is 1.11 + or - 0.4 micrograms for the flight rats and 1.85 + or - 1.3 micrograms for the control rats.

Hymer, W. C.↗
NASA NTRS1985

Toward the development of guidelines for technical report preparation

American National Standards Institute (ANSI) standard Z39.18, 'Guidelines for Format and Production of Scientific and Technical Reports', is undergoing revision. Background describing the standard's evolution is presented as is the strategy used for undertaking the revision. The issues central to revising the standard are presented along with an explanation of how each issue will be handled. Related research and literature relevant to the standard's revision are included.

Pinelli, T. E.↗
NASA NTRS1986

An assessment of the status and trends in satellite communications 1986-2000: An information document prepared for the Communications Subcommittee of the Space Applications Advisory Committee

This is a response to a Space Applications Advisory Committee (SAAC) request for information about the status and trends in satellite communications, to be used to support efforts to conceive and recommend long range goals for NASA communications activities. Included in this document are assessments of: (1) the outlook for satellite communications, including current applications, potential future applications, and impact of the changing environment such as optical fiber networks, the Integrated Services Digital Network (ISDN) standard, and the rapidly growing market for Very Small Aperture Terminals (VSAT); (2) the restrictions imposed by our limited spectrum resource; and (3) technology needs indicated by future trends. Potential future systems discussed include: large powerful satellites for providing personal communications; VSAT compatible satellites with onboard switching and having voice capability; large satellites which offer a pervasive T1 network service (primarily for video-phone); and large geostationary communications facilities which support common use by several carriers. Also, discussion is included of NASA particular needs and possible future systems. Based on the mentioned system concepts, specific technology recommendations are provided for the time frames of now - 1993, 1994 - 2000, and 2000 - 2010.

Poley, W. A.↗
NASA NTRS1986

Method to prepare oxide films

This invention pertains to a method for producing metal oxide films characterized by the fact that the metal elements constituting the main metal alloys contain at least one kind of transition element, and that the metal elements which constitute said metal alloy are thin films of barium and titanium in almost the same mol ratio.

Hirota, T.↗