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NASA NTRS1983

The first dedicated life sciences mission - Spacelab 4

The details of the payload and the experiments in Spacelab 4, the first Spacelab mission dedicated entirely to the life sciences, are discussed. The payload of Spacelab 4, carried in the bay of the Shuttle Orbiter, consists of 25 tentatively selected investigations combined into a comprehensive integrated exploration of the effects of acute weightlessness on living systems. The payload contains complementary designs in the human and animal investigations in order to validate animal models of human physiology in weightlessness. Animals used as experimental subjects will include squirrel monkeys, laboratory rats, several species of plants, and frog eggs. The main scientific objectives of the investigations include the study of the acute cephalic fluid shift, cardiovascular adaptation to weightlessness, including postflight reductions in orthostatic tolerance and exercise capacity, and changes in vestibular function, including space motion sickness, associated with weightlessness. Other scientific objective include the study of red cell mass reduction, negative nitrogen balance, altered calcium metabolism, suppressed in vitro lymphocyte reactivity, gravitropism and photropism in plants, and fertilization and early development in frog eggs.

Cramer, D. R.↗

NASA NTRS1983

Cumulus cloud transport of transient tracers

A theoretical framework is developed for including cumulus cloud transport, rainout of water soluble gases, and aqueous phase chemistry into gas phase photochemical models. Cloud populations are represented as ensemble distributions of individual clouds of various heights. An individual cloud is represented as a one-dimensional, steady state plume with height-independent radius entraining air from the boundary of the cloud. The model is applied to several hypothetical atmospheric tracers to show how clouds may affect the tropospheric distributions of ozone, NO(y), SO2, peroxyacetylnitrate, hydrocarbons, and other gases. Although the numerical experiments were based on cloud mass fluxes from diagnostic studies in the tropics and thus are not representative of the entire globe, it was found that an increasing mixing ratio with height in the free troposphere can be produced for some gases with only a surface source when clouds are present. This suggests that some reactive tropospheric species with primarily surface sources may play a somewhat more important role in tropospheric chemistry than is presently believed depending on the global distribution of cloud mass fluxes. Deficiencies in existing photochemical models due to the way clouds are typically treated are discussed.

Gidel, L. T.↗

NASA NTRS1983

Aqueous-phase source of formic acid in clouds

The coupled gas- and aqueous-phase cloud chemistry of HCOOH were examined for controlling factors in the acidity of cloud and rainwater. Attention was given to the aqueous OH/HO2 system that yields an OH species that is highly reactive with other species, notably SO2 and the formaldehyde/formic acid complex. A numerical model was developed to simulate the cloud chemistry in the remote troposphere, with considerations given to CH4-CO-NO(x)-O3-H(x)O(y) system. It was determined that aqueous phase OH radicals can produce and destroy formic acid droplets in daylight conditions, as well as control formic acid levels in rainwater. It is sugested that the same types of reactions may be involved in the control of acetic acid and other organic acids.

Chameides, W. L.↗

NASA NTRS1983

Executive summary, aerothermal modeling program, phase 1

Submodels used in the combustor analytical models that were successfully used in designing advanced technology combustors were assessed. Specific recommendations for further improvement of model accuracy for combustor design purposes were made. Based upon an exhaustive literature survey, a number of test cases were selected to assess accuracy of submodels of turbulence, turbulence/chemistry interaction, spray combustion, and dilution jet mixing processes within a confined cross-stream. These test cases included simple flows and complex flows with and without swirl. Nonrecirculating and recirculating, and nonreactive and reactive flows were investigated. It was concluded that the current models give qualitative trends for the recirculating secondary flows (as encountered in a gas turbine combustor primary zone), but the predictions are good for the dilution zone.

Srinivasan, R.↗

NASA NTRS1983

LaNi5 hydride cryogenic refrigerator test results

A complete LaNi5 hydrogen absorption cryogenic refrigerator system was developed. The system uses low temperature waste heat of approximately 100 C as a power source, and has no moving parts other than self operating valves. The cycle continues automatically by an electronic sequencing timing mechanism for the three compressors which are phased such that a constant supply of high pressure hydrogen gas is provided. It is indicated that with a fully clean hydrogen system, hundreds of thousand cycles should be attainable, even though some degradation may eventually occur. Simple vacuum reactivation of the hydride of moving parts, other than self operating, long life valves, the refrigerators predicted life is extremely long.

Jones, J. A.↗

NASA NTRS1984

Phenoxy resins containing pendent ethynyl groups

As part of an effort on tougher/solvent resistant matrix resins for composites, research was directed towards exploring methods to improve the solvent resistance of linear amorphous thermoplastics. Ethyl reactive groups were placed on the ends of oligomers and pendent along the polymer chain and subsequently thermally reacted to provide crosslinking and thus improvement in solvent resistance. This concept is extended to another thermoplastic, a phenoxy resin. A commercially available phenoxy resin (PKHH) was systematically modified by reaction of the pendent hydroxyl groups on the phenoxy resin with various amounts of 4-ethynylbenzoyl chloride. As the pendent ethynyl group content in the phenoxy resin increased, the cured resin exhibited a higher glass transition temperature, better solvent resistance and less flexibility. The solvent resistance was further improved by correcting a low molecular weight diethynyl compound, 2,2-bis(4-ethynylbenzoyloxy-4'-phenyl)propane, with a phenoxy resin containing pendent ethynyl groups.

Hergenrother, P. M.↗

NASA NTRS1984

Regulation of hematopoiesis in the suspended rat as a model for space flight

A series of studies was completed in which a variety of routine hematological and other parameters were obtained from sequential sampling of control and suspended rats. These data showed that, during suspension, the rats failed to gain weight at the same rate as the controls, ate and drank significantly less, demonstrated a transient increase in peripheral hematocrit and RBC count, a transient decrease in MCH, suppressed reticulocyte counts and a progressive decrease in MCV but no change in RBC shape. Leukocyte counts were variably decreased but no significant changes in platelet numbers were noted. Post-suspension, evidence of anemia was present from a reduced RBC count, hemoglobin, hematocrit, and MCV. A leukocytosis was also noted. Efforts directed to the collection of data aimed at understanding changes in blood volume during suspension are also discussed. As part of these studies the following parameters were investigated; RBC survival, in vitro leukocyte reactivity to PHA, bone marrow and spleen cellularity and morphology, ferrokinetics, and the hematopoietic inductive microenvironment.

Dunn, C. D. R.↗

NASA NTRS1984

Isolation and characterization of beta-glucan synthase: A potential biochemical regulator of gravistimulated differential cell wall loosening

In plants, gravity stimulates differential growth in the upper and lower halves of horizontally oriented organs. Auxin regulation of cell wall loosening and elongation is the basis for most models of this phenomenon. Auxin treatment of pea stem tissue rapidly increases the activity of Golgi-localized Beta-1,4-glucan synthase, an enzyme involved in biosynthesis of wall xyloglucan which apparently constitutes the substrate for the wall loosening process. The primary objective is to determine if auxin induces de novo formation of Golgi glucan synthase and increases the level of this glucan synthase mRNA. This shall be accomplished by (a) preparation of a monoclonal antibody to the synthase, (b) isolation, and characterization of the glucan synthase, and (c) examination for cross reactivity between the antibody and translation products of auxin induced mRNAs in pea tissue. The antibody will also be used to localize the glucan synthase in upper and lower halves of pea stem tissue before, during and after the response to gravity.

Kuzmanoff, K. M.↗

NASA NTRS1984

Ultra-high molecular weight silphenylene-siloxane polymers

Silphenylene-siloxane copolymers with molecular weights above one million were prepared using a two stage polymerization technique. The technique was successfully scaled up to produce 50 grams of this high polymer in a single run. The reactive monomer approach was also investigated using the following aminosilanes: bis(dimethylamino)dimethylsilane, N,N-bis(pyrrolidinyl)dimethylsilane and N,N-bis(gamma-butyrolactam)dimethylsilane). Thermal analyses were performed in both air and nitrogen. The experimental polymers decomposed at 540 to 562 C, as opposed to 408 to 426 C for commercial silicones. Differential scanning calorimetry showed a glass transition (Tg) at -50 to -55 C for the silphenylene-siloxane copolymer while the commercial silicones had Tg's at -96 to -112 C.

Patterson, W. J.↗

NASA NTRS1983

Prochloron research

The purpose was to prepare Prochloron photosynthetic membranes for the isolation of the two major chlorophyll-proteins, the P700-chlorophyll a-protein and the light-harvesting chlorophyll a/b-protein, using SDS-polyacrylamide gel electrophoresis. The prepared proteins (purified) were examined for their cross-reactivity to polyclonal antibodies prepared from higher plant proteins. In addition, material was prepared for electron microscopy, and isolation of the DNA for determination of its general complexity (COT analysis) and similarity to barley chloroplast DNA and Anabaena DNA by using restriction-endonuclease analysis. Kleinschmidt spreads of the DNA were in the electron microscope to identify and measure the extent and size of the circlar DNA.

Lewin, R. A.↗

NASA NTRS1983

Prochloron expedition

The purpose was to prepare Prochloron phototsynthetic membranes for the isolation of the two major chlorophyll-proteins, the p700-chlorophyll a protein and the light harvesting chlorophyll a/b-protein, using SDS-polyacrylamide get electrophoreses. The prepared proteins (purified) were examined for their cross-reactivity to polyclonal antibodies prepared from higher plant proteins. In addition, material was prepared for electron microscopy, and isolation of the DNA for determination of its general complexity (COT analysis) and similarity to barley chloroplast DNA and Anabaena DNA by using restriction-endonuclease analysis Kleinschmidt spreads of the DNA were in the electron microscope to identify and measure the extent and size of the circular DNA.

Alberte, R. S.↗

NASA NTRS1984

Saturated laser fluorescence in turbulent sooting flames at high pressure

The primary objective was to develop a quantitative, single pulse, laser-saturated fluorescence (LSF) technique for measurement of radical species concentrations in practical flames. The species of immediate interest was the hydroxyl radical. Measurements were made in both turbulent premixed diffusion flames at pressures between 1 and 20 atm. Interferences from Mie scattering were assessed by doping with particles or by controlling soot loading through variation of equivalence ratio and fuel type. The efficacy of the LSF method at high pressure was addressed by comparing fluorescence and adsorption measurements in a premixed, laminar flat flame at 1-20 atm. Signal-averaging over many laser shots is sufficient to determine the local concentration of radical species in laminar flames. However, for turbulent flames, single pulse measurements are more appropriate since a statistically significant number of laser pulses is needed to determine the probability function (PDF). PDFs can be analyzed to give true average properties and true local kinetics in turbulent, chemically reactive flows.

King, G. B.↗

NASA NTRS1984

Overview of zirconia with respect to gas turbine applications

Phase relationships and the mechanical properties of zirconia are examined as well as the thermal conductivity, deformation, diffusion, and chemical reactivity of this refractory material. Observations from the literature particular to plasma-sprayed material and implications for gas turbine engine applications are discussed. The literature review indicates that Mg-PSZ (partially stabilized zirconia) and Ca-PSZ are unsuitable for advanced gas turbine applications; a thorough characterization of the microstructure of plasma-sprayed zirconia is needed. Transformation-toughened zirconia may be suitable for use in monolithic components.

Cawley, J. D.↗

NASA NTRS1983

Dry etching of metallization

The production dry etch processes are reviewed from the perspective of microelectronic fabrication applications. The major dry etch processes used in the fabrication of microelectronic devices can be divided into two categories - plasma processes in which samples are directly exposed to an electrical discharge, and ion beam processes in which samples are etched by a beam of ions extracted from a discharge. The plasma etch processes can be distinguished by the degree to which ion bombardment contributes to the etch process. This, in turn is related to capability for anisotropic etching. Reactive Ion Etching (RIE) and Ion Beam Etching are of most interest for etching of thin film metals. RIE is generally considered the best process for large volume, anisotropic aluminum etching.

Bollinger, D.↗

NASA NTRS1984

Photovoltaic power conditioning subsystem: State of the art and development opportunities

Photovoltaic systems, the state of the art of power conditioning subsystem components, and the design and operational interaction between photovoltaic systems and host utilities are detailed in this document. Major technical issues relating to the design and development of power conditioning systems for photovoltaic application are considered; these include: (1) standards, guidelines, and specifications; (2) cost effective hardware design; (3) impact of advanced components on power conditioning development; (4) protection and safety; (5) quality of power; (6) system efficiency; and (7) system integration with the host utility. Theories of harmonic distortion and reactive power flow are discussed, and information about power conditioner hardware and manufacturers is provided.

Krauthamer, S.↗

NASA NTRS1984

Infrared emission associated with chemical reactions on Shuttle and SIRTF surfaces

The infrared intensities which would be observed by the Shuttle Infrared Telescope Facility (SIRTF), and which are produced by surface chemistry following atmospheric impact on SIRTF and the shuttle are estimated. Three possible sources of reactants are analyzed: (1) direct atmospheric and scattered contaminant fluxes onto the shuttle's surface; (2) direct atmospheric and scattered contaminant fluxes onto the SIRTF sunshade; and (3) scattered fluxes onto the cold SIRTF mirror. The chemical reactions are primarily initiated by the dominent flux of reactive atomic oxygen on the surfaces. Using observations of the optical glow to constrain theoretical parameters, it is estimated for source (1) that the infrared glow on the SIRTF mirror will be comparable to the zodiacal background between 1 and 10 micron wavelengths. It is speculated that oxygen reacts with the atoms and the radicals bound in the organic molecules that reside on the shuttle and the Explorer surfaces. It is concluded that for source (2) that with suitable construction, a warm sunshade will produce insignificant infrared glow. It is noted that the atomic oxygen flux on the cold SIRTF mirror (3) is insufficient to produce significant infrared glow. Infrared absorption by the ice buildup on the mirror is also small.

Hollenbach, D. J.↗

NASA NTRS1983

Absorbable-susceptor joining of ceramic surfaces

An assembly of ceramic surfaces particularly refractory metal oxides and carbides, abutting a thin sheet of metal susceptor material are placed in a chamber of an enclosure containing inert gas. An RF coil is activated by power supply to melt the susceptor and adjacent zones of the ceramic. Reactive gas such as oxygen or a carbonizing gas is then fed to the chamber and reacts with the susceptor to form compounds which disperse and dissolve in the zones. On cooling, a strong joint is formed. The susceptor may contain inner perforations and outer perforations to aid in distribution of heat.

Schroeder, J. E.↗

NASA NTRS1984

Temperature Effects in Elastohydrodynamically Lubricated Contacts

This paper gives an overview of our current understanding of thermal phenomena in elastohydrodynamic contacts and suggests some avenues for fruitful research in the next decade. Typical measured temperatures are presented for representative conditions and ranges of operating parameters. Temperatures can range from bulk ambient temperature to several hundred degrees centigrade in fully separated elastohydrodynamic films. Although attention in the past decade has been on the full film for the purposes of understanding film thickness and traction phenomena, the more interesting conditions are in the mixed elastohydrodynamic films. These mixed conditions are both common in tribological systems and they are the conditions that border on unsuccessful run-in and failure of the elastohydrodynamic contact. In mixed film conditions local hotspots can have temperatures of the order of 1888 C which cause increased reactivity of the surfaces with surrounding materials as well as changes of the surface physical properties so important to the operation of concentrated contacts. An additional area discussed is that of the bulk system thermal transients which occur in tribological systems. These transients are frequently long in duration and have a direct bearing on the elastohydrodynamic film thickness and traction.

Ward O Winer↗