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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 181 records · Page 10

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NASA NTRS1972

The synthesis of starch from carbon dioxide using isolubilized stabilized enzymes

Systems for artificial manufacture of starch and for delineation of technological areas, and the rationale for studying them are considered. A discussion of the enzyme-catalyzed routes of synthesis available and a choice as to the most promising route are presented. A discussion of the enzymes involved, of enzyme insolubilization technology, and of possible engineering approaches, with examples in the form of model calculations for both reactors and separators, are also presented.

Bassham, J. A.↗

NASA NTRS1972

A discussion of CO and O on Venus and Mars

The absorption of solar ultraviolet radiation in the wavelength range 2000 to 2200 A by CO2 strongly reduces the dissociation rate of HCl on Venus. The Cl catalytic reaction for the rapid recombination of O and CO and the yellow coloration of the Venus haze by OCl(-) and Cl3(-) appears to be unlikely. At the time of the Martian dust storm, the dissociation of H2O in the vicinity of the surface may vanish. The increase of dissociation at high altitudes, however, can be the source of H atoms in the upper atmosphere. The H atoms from the dissociation of hydrides may catalyze the recombination of CO and O in the lower atmospheres of these planets according to the following scheme: H + CO + M yields HCO + M, and HCO + O yields H + CO2. In the case of Venus, there may be other kinds of sinks for the photodissociation products, and its chemical environment might be more complex than that of Mars.

Shimizu, M.↗

NASA NTRS1971

Synthesis of adenine, guanine, cytosine, and other nitrogen organic compounds by a Fischer-Tropsch-like process.

Study of the formation of purines, pyrimidines, and other bases from CO, H2, and NH3 under conditions similar to those used in the Fischer-Tropsch process. It is found that industrial nickel/iron alloy catalyzes the synthesis of adenine, guanine, cytosine, and other nitrogenous compounds from mixtures of CO, H2, and NH3 at temperatures of about 600 C. Sufficient sample was accumulated to isolate as solid products adenine, guanine, and cytosine, which were identified by infrared spectrophotometry. In the absence of nickel/iron catalyst, at 650 C, or in the presence of this catalyst, at 450 C, no purines or pyrimidines were synthesized. These results confirm and extend some of the work reported by Kayatsu et al. (1968).

Yang, C. C.↗

NASA NTRS1971

The possible participation of esters as well as amides in prebiotic polymers.

Demonstration that alpha-hydroxy acids may have participated in the formation of prebiological polymers in a manner similar to the participation of alpha-amino acids. Ex periments are described which indicate that the system for forming peptide bonds in present-day biological organisms is equally competent in forming ester and polyester bonds. In particular, the experiments described are directed toward answering questions regarding the action of peptidyl transferase in ester formation. Also, an attempt is made to determine whether a complete protein synthetic system can operate with transfer RNA molecules which have alpha-hydroxyl acids attached to them instead of alpha-amino acids, using both synthetic and natural mRNA. The ability of ribosomal peptidyl transferase to catalyze the formation of an ester bond as well as its normal product, the peptide bond, is demonstrated.

Rich, A.↗

NASA NTRS1972

3-phosphoglycerate kinase from Hydrogenomonas facilis.

Description of studies of the kinetics of heat inactivation of phosphoglycerate kinase in the soluble fraction from Hydrogenomonas facilis, its extensive purification, and inhibition by adenosine monophosphate (AMP). No evidence was found for an enzyme which catalyzes adenosine-triphosphate-dependent conversion of 3-phosphoglycerate to 1,3-diphosphoglycerate, AMP, and phosphate.

Mcfadden, B. A.↗

NASA NTRS1972

Development of moldable carbonaceous materials for ablative rocket nozzles.

Description of a materials system developed for use as low-cost ablative nozzles for NASA's 260-in. solid rocket motor. Petroleum coke and carbon black fillers were employed; high density was achieved by controlling particle size distribution. An alumina catalyzed furfuryl ester resin which produced high carbon residues after pyrolysis was employed as the binder. Staple carbon fibers improved the strength and crack resistance of molded bodies. In static firing tests of two subscale nozzles, this material compared favorably in erosion rate with several other ablative systems.

Lockhart, R. J.↗

NASA NTRS1972

Advanced spacecraft fuel cell systems.

The specific goals of the system selected for development are 10,000 hours of operation with refurbishment, 20 lb/kW at a sustained power of 7 kW, and 21 kW peaking capability for durations of two hours. The system is designed to operate on low pressure, propulsion grade hydrogen and oxygen. Product water is removed by a passive water removal method that employs a porous hydrophobic membrane as a part of the water transport plate. Aspects of system component testing are discussed together with advanced materials to be used. It was found that the initial performance of a cell with a gold catalyzed cathode is superior to a cell with platinum catalyst. The problem of a certain inability to maintain the desired gas-electrolyte-catalyst interface is the main source of difficulty with the gold-based catalysts.

Thaller, L. H.↗

NASA NTRS1974

A methanol/air fuel cell system

High power-density, self-regulating fuel cell develops electrical power from catalyzed reaction between methanol and atmospheric oxygen. Cells such as these are of particular interest, because they may one day offer an emission-free, extremely efficient alternative to internal-combustion engines as power source.

Asher, W. J.↗

NASA NTRS1972

The effect of solid phase reactions on the ballistic properties of propellants

The combustion of NHClO4 composite propellants was studied between 15 and 3000 psi. The emphasis was on determining the mechanisms by which the fuel components influence the burning rate of the composites. All combustion experiments were performed with pressed powder strands. The fuels affected the combustion mechanism of the composite through their effect on the oxidizer decomposition mechanism, the composite surface temperature, and by reacting heterogeneously with the oxidizer on the surface of the composite. The results indicate that the fuel component has a significant effect on the surface temperature in both catalyzed and uncatalyzed composites. The data suggest that the contribution, to the overall combustion reaction, of heterogeneous reactions increases with increasing pressure. There is also evidence that even in steady state combustion the ignition of individual oxidizer particles is an important parameter in determining the combustion characteristics of the composite.

Schmidt, W. G.↗

NASA NTRS1972

Stability of the Martian atmosphere

A detailed chemical dynamic model is presented for a moist Martian atmosphere. Recombination of CO2 is catalyzed by trace amount of H2O. The abundances of CO and O2 should vary in response to changes in atmospheric H2O and atmospheric mixing.

Mcelroy, M. B.↗

NASA NTRS1973

The photolytic stability of the Martian atmosphere.

Several recent suggestions for stabilizing the Martian atmosphere against photolysis have proved untenable. However, downward convective transport as well as a low altitude (0-35 km) aerosol, which catalyzes two-body molecular recombination reactions, can bring about such stability. The 'effective' convection velocity and 'average' two-body reaction rate coefficients required by observed abundances are evaluated. The computed profiles of CO and O at high altitude are shown to agree well with observations.

Whitten, R. C.↗

NASA NTRS1974

Application of nitrogen metabolism in autotrophic bacteria to chemosynthetic bioregeneration in space missions, supplement

The chemolithotroph, Hydrogenomonas eutropha, was considered as a life support, bioregenerative system. This project focuses on several metabolic functions that are related to the proposed nitrogen cycle between man and this microbe. Specifically this organism has the capability to utilize as the sole nitrogen source such urine components as urea and fifteen individual amino acids, but not nine other amino acids. The effectiveness of utilization was high for many amino acids. Several specific growth inhibitions were also observed. The enzyme that catalyzes the incorporation of ammonia in the medium into amino acids was identified as a NADP-specific, L-glutamate dehydrogenase. This enzyme has a constitutive nature. This organism can synthesize all of its amino acids from carbon dioxide and ammonia. Therefore with the background literature of multiple pathways of individual amino acid biosyntheses, our evidence to date is consistent with the Hydrogeneomonas group having the same pathway of valine-isoleucine formation as the classical E. coli.

Wixom, R. L.↗

NASA NTRS1974

Comparison of inert-gas-fusion and modified Kjeldahl techniques for determination of nitrogen in niobium alloys

This report compares results obtained for the determination of nitrogen in a selected group of niobium-base alloys by the inert-gas-fusion and the Kjeldahl procedures. In the inert-gas-fusion procedure the sample is heated to approximately 2700 C in a helium atmosphere in a single-use graphite crucible. A platinum flux is used to facilitate melting of the sample. The Kjeldahl method consisted of a rapid decomposition with a mixture of hydrofluoric acid, phosphoric acid, and potassium chromate; distillation in the presence of sodium hydroxide; and highly sensitive spectrophotometry with nitroprusside-catalyzed indophenol. In the 30- to 80-ppm range, the relative standard deviation was 5 to 7 percent for the inert-gas-fusion procedure and 2 to 8 percent for the Kjeldahl procedure. The agreement of the nitrogen results obtained by the two techniques is considered satisfactory.

Merkle, E. J.↗

NASA NTRS1973

An interfaced system for production of methane in a spacecraft

The formose reaction, the homogeneously catalyzed condensation of formaldehyde to sugars, proceeds simultaneously with Cannizzaro and crossed Cannizzaro reactions. Reaction studies in a continuous stirred tank reactor have shown that rate instabilities are exhibited. There are temperature instabilities as well as concentration instabilities in calcium hydroxide catalyst, formaldehyde reactant, and hydroxyl ion. It is postulated that Ca(OH)+ is the actual catalytic species for the formose system. A unifying mechanism is developed that postulates that reactions proceed from a common intermediate complexed species, and that the selectivity for each reaction depends on the nature of the catalyst forming the carbohydrate complex. The catalytic mechanism explains the Lobry de Bruyn-van Eckenstein aldose ketose rearrangements and mutarotations of sugars that also proceed in the system.

Weiss, A. H.↗

NASA NTRS1973

Chemistry in interstellar space

The particular characteristics of chemistry in interstellar space are determined by the unique environmental conditions involved. Interstellar matter is present at extremely low densities. Large deviations from thermodynamic equilibrium are, therefore, to be expected. A relatively intense ultraviolet radiation is present in many regions. The temperatures are in the range from 5 to 200 K. Data concerning the inhibiting effect of small activation energies in interstellar clouds are presented in a table. A summary of measured activation energies or barrier heights for exothermic exchange reactions is also provided. Problems of molecule formation are discussed, taking into account gas phase reactions and surface catalyzed processes.

Donn, B.↗

NASA NTRS1974

Stratospheric ozone destruction by man-made chlorofluoromethanes

Calculations indicate that chlorofluoromethanes produced by man can greatly affect the concentrations of stratospheric ozone in future decades. This effect follows the release of chlorine from these compounds in the stratosphere. Present usage levels of chlorofluoromethanes can lead to chlorine-catalyzed ozone destruction rates that will exceed natural sinks of ozone by 1985 or 1990.

Cicerone, R. J.↗

NASA NTRS1974

Combustion chemistry of solid propellants

Several studies are described of the chemistry of solid propellant combustion which employed a fast-scanning optical spectrometer. Expanded abstracts are presented for four of the studies which were previously reported. One study of the ignition of composite propellants yielded data which suggested early ammonium perchlorate decomposition and reaction. The results of a study of the spatial distribution of molecular species in flames from uncatalyzed and copper or lead catalyzed double-based propellants support previously published conclusions concerning the site of action of these metal catalysts. A study of the ammonium-perchlorate-polymeric-fuel-binder reaction in thin films, made by use of infrared absorption spectrometry, yielded a characterization of a rapid condensed-phase reaction which is likely important during the ignition transient and the burning process.

Baer, A. D.↗

NASA NTRS1974

Utilization of immobilized urease for waste water treatment

The feasibility of using immobilized urease for urea removal from waste water for space system applications is considered, specifically the elimination of the urea toxicity problem in a 30-day Orbiting Frog Otolith (OFO) flight experiment. Because urease catalyzes the hydrolysis of urea to ammonia and carbon dioxide, control of their concentrations within nontoxic limits was also determined. The results of this study led to the use of free urease in lieu of the immobilized urease for controlling urea concentrations. An ion exchange resin was used which reduced the NH3 level by 94% while reducing the sodium ion concentration only 10%.

Husted, R. R.↗