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At least 181 records · Page 10

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NASA NTRS1972

Design and test of porous-tungsten mercury vaporizers

Future use of large size Kaufman thrusters and thruster arrays will impose new design requirements for porous plug type vaporizers. Larger flow rate coupled with smaller pores to prevent liquid intrusion will be desired. The results of testing samples of porous tungsten for flow rate, liquid intrusion pressure level, and mechanical strength are presented. Nitrogen gas was used in addition to mercury flow for approximate calibration. Liquid intrusion pressure levels will require that flight thruster systems with long feed lines have some way (a valve) to restrict dynamic line pressures during launch.

Kerslake, W. R.↗

NASA NTRS1971

Dissociation-excitation reactions of argon metastables with carbon dioxide.

Results of a study showing that a metastable argon-carbon dioxide reaction results in dissociation of carbon dioxide and electronic excitation of one of the products, carbon monoxide or oxygen. A flow system using a 2450-MHz discharge was used to produce metastable argon atoms. Metastable argon in the afterglow was confirmed by adding nitrogen to the afterglow. Without addition of carbon dioxide no argon line emission, or any other emission, is observed from the reaction zone. Absence of argon line emission produced by recombination indicates the absence of charged species.

Starr, W. L.↗

NASA NTRS1972

Design and test of porous-tungsten mercury vaporizers.

Future use of large size Kaufman thrusters and thruster arrays will impose new design requirements for porous plug type vaporizers. Larger flow rate coupled with smaller pores to prevent liquid intrusion will be desired. This paper presents the results of testing samples of porous tungsten for flow rate, liquid intrusion pressure level, and mechanical strength. Nitrogen gas was used in addition to mercury flow for approximate calibration. Liquid intrusion pressure levels will require that flight thruster systems with long feed lines have some way (a valve) to restrict dynamic line pressures during launch.

Kerslake, W. R.↗

NASA NTRS1973

The effect of photochemical models on calculated equilibria and cooling rates in the stratosphere

Simplified models were developed for radiative heating and cooling and for ozone photochemistry in the region 22-60 km. The latter permit the inclusion of nitrogen and hydrogen reactions in addition to simple oxygen reactions. The simplicity of the scheme facilitates the use of a wide variety of cooling and reaction rates. It is shown that joint radiative-photochemical equilibrium is appropriate to the mean state of the atmosphere between 35 and 60 km. The relaxation of perturbations from joint radiative-photochemical equilibrium was also investigated. In all cases the coupling between temperature dependent ozone photochemistry and radiation lead to a reduction of the thermal relaxation time from its purely radiative value. The latter, which amounts to about 10 days, is reduced to 2-4 days at heights of 31-35 km. This greatly enhances the dissipation of waves traveling through the stratosphere.

Blake, D.↗

NASA NTRS1987

MSIS-86 thermospheric model

The MSIS-86 empirical model of thermospheric temperature, density and composition uses new temperature and composition data from the Dynamics Explorer satellite to improve the representation of polar region morphology over that in the MSIS-83 model. Terms were added or changed to better represent seasonal variations in the polar regions under both quiet and magnetically disturbed conditions. Local time variations in the magnetic activity effect were added. In addition a new species, atomic nitrogen, was added to the previous list of N2, O2, He, O, H, and Ar covered by the model.

Hedin, Alan E.↗

NASA NTRS1987

Simulation and control of a Space Station air revitalization system

A computer simulation tool is written to investigate simulation and control of a Space Station air revitalization system. Candidate subsystems for various air revitalization roles in the Space Station have been and continue to be tested. However, integration and control of these subsystems into an effective system which revitalizes the air in all habitable areas needs to be evaluated. From such an evaluation, the size of subsystems, size and location of accumulators, and decisions on bussing of carbon dioxide, hydrogen, oxygen, and nitrogen can be affected. In addition, various control approaches can be assessed. The computer simulation model is described and its applications are presented.

Yanosy, James L.↗

NASA NTRS1988

Heterogeneous chemistry related to Antarctic ozone depletion: Reaction of ClONO2 and N2O5 on ice surfaces

Laboratory studies of heterogeneous reactions of possible importance for Antarctic ozone depletion were performed. In particular, the reactions of chlorine nitrate (ClONO2) and dinitrogen pentoxide (N2O5) were investigated on ice and HCl/ice surfaces. These reactions occur on the surfaces of polar stratospheric clouds (PSCs) over Antarctica. One reaction transforms the stable chlorine reservoir species (ClONO2 and HCl) into photochemically active chlorine in the form of HOCl and Cl2. Condensation of HNO3 in the reactions removes odd nitrogen from the stratosphere, a requirement in nearly all models of Antarctic ozone depletion. Other reactions may also be important for Antarctic ozone depletion. Like the reactions of chlorine nitrate, these reactions deplete odd nitrogen through HNO3 condensation. In addition, one reaction converts a stable chlorine reservior species (HCl) into photochemically active chlorine (ClNO2). These reactions were studied with a modified version of a Knudsen cell flow reactor.

Tolbert, Margaret A.↗

NASA NTRS1989

A computer control system for the alternating gradient magnetometer

An alternating gradient magnetometer was interfaced to a computer for the automation of data taking. Using a fast Fourier transform analysis system data can be acquired and processed in real time. Data are stored on disk and can be recalled for plotting and further analysis. With the addition of a simple liquid nitrogen cryostat, magnetization measurements can be performed in the range from 300 to 77 K. Results are reported on three different types of piezoelectric transducers.

Garland, Michael M.↗

NASA NTRS2000

Indicator Devices for Detection of Trace Gaseous Hydrazines

The relatively recent decrease in the acceptable time-weighted-average for hydrazines from 100 parts-per-billion (ppb) to 10 ppb rendered many trace hydrazine detectors either insensitive or inaccurate. Development of a rapid detection method for hydrazines at the new 10-ppb concentration was necessary so that test area personnel could reliably assess airborne hydrazines concentrations of a potentially contaminated area prior to entry. The reduction of Au(III) to Au(0) by hydrazines is a well characterized reaction and application of the corresponding yellow to purple color change was selected as a potentially useful means for detection of trace hydrazines in air. Tests with small quantities of KAuCl4 deposited on a variety of substrates were conducted using verified sources of 1,1-dimethylhydrazine, methylhydrazine, and hydrazine at approximately 10 ppb in air. Substrates tested were glass fiber filter paper, glass beads, anion exchange resin (AuCl4- form), and diatomaceous earth. The most successful of these substrates were glass fiber filter paper and diatomaceous earth. The KAuC14 impregnated glass fiber filter paper appeared to be somewhat light sensitive so further tests were conducted using the diatomaceous earth substrate. KAuCl4 concentration, substrate particle size, and sampler configuration were evaluated. Based on these tests, the device selected for further evaluation was a 5mm OD by 50mm glass tube containing 0.02-0.03g of 45/60 mesh diatomaceous earth coated with 2 percent KAuCl4. When connected to a sampling pump, response of the device to changes in relative humidity, ambient light, and high levels of other fluids, which might also be found in a propellant test area, was evaluated. False positive responses were not detected for exposures to relative humidity changes from 10 to 80 percent, sunlight for greater than 10 minutes, or percent levels of ammonia, isopropyl alcohol, nitrogen dioxide, and hydrogen. In addition, body emissions did not produce a false positive response in view of potential application for use inside protective clothing. The device was shown to reliably detect less than 10 ppb of the hydrazines tested using a 10 to 20L sample followed by a 2 to 5 minute color development time. Some field tests were conducted in parallel with conventional acidic firebrick sorbent tubes. There was generally very good agreement between the devices and firebrick sorbent tubes when greater than 10 ppb of a hydrazine was present.

Dee, Lou A.↗

NASA NTRS2000

R6 Hexameric Insulin Complexed with m-Cresol or Rescorcinol

The structures of three R6 human insulin hexamers have been determined. Crystals of monoclinic m-cresol/insulin, monoclinic resorcinol/insulin, and rhombohedral m-cresol/insulin crystals diffracted to 1.9, 1.9 and 1,78 Angstroms, respectively, and have been refined to residuals of 0.195, 0.179, and 0.200, respectively. In all three structures, a phenolic derivative is found to occupy the phenolic binding site where it forms hydrogen bonds to the carbonyl oxygen of A6 Cys and the nitrogen of A11 Cys. Two additional phenolic derivative binding sites were identified within or between hexamers. The structures of all three hexamers are nearly identical although a large displacement of the N-terminus of one B-chain in both monoclinic structures results from coordination to a sodium ion which is located between symmetry related hexamers. Other minor differences in structure are a consequence of differences in packing in the monoclinic cell as compared to the rhombohedral cell. Based upon the differences in conformation of the B13 Glu side chains in T6, T3R3, and R6 hexamers, the deprotonation of these side chains appears to be associated with the T (right arrow) R conformational transition.

Smith, G. David↗

NASA NTRS2004

Infrared Spectroscopy of Matrix-Isolated Polycyclic Aromatic Compounds and Their Ions: Phenazine, a Dual Substituted Polycyclic Aromatic Nitrogen Heterocycle - 7

The matrix-isolation technique has been employed to measure the mid-infrared spectra of phenazine (C12H8N2), a dual substituted Polycyclic Aromatic Nitrogen Heterocycle (PANH), in the neutral, cationic and anionic forms. The experimentally measured band frequencies and intensities are tabulated and compared with their calculated values as well as those of the non-substituted parent molecule, anthracene. The theoretical band positions and intensities were calculated using both the 3-31 G as well as the larger 6-3lG* Basis Sets. A comparison of the results can be found in the tables. The spectroscopic properties of phenazine and its cation are similar to those observed in mono-substituted PANHs, with one exception. The presence of a second nitrogen atom results in an additional enhancement of the cation's total integrated intensity, for the 1500-1000 cm(sup -1) (6.7 to 10 micron) region, over that observed for a mono-substituted PANH cation. The significance of this enhancement and the astrobiological implications of these results are discussed.

Mattioda, A. L.↗

NASA NTRS2001

Ultra-Efficient Engine Technology (UEET) Program

The Ultra-Efficient Engine Technology (UEET) Program includes seven key projects that work with industry to develop and hand off revolutionary propulsion technologies that will enable future-generation vehicles over a wide range of flight speeds. A new program office, the Ultra-Efficient Engine Technology (UEET) Program Office, was formed at the NASA Glenn Research Center to manage an important National propulsion program for NASA. The Glenn-managed UEET Program, which began on October 1, 1999, includes participation from three other NASA centers (Ames, Goddard, and Langley), as well as five engine companies (GE Aircraft Engines, Pratt & Whitney, Honeywell, Allison/Rolls Royce, and Williams International) and two airplane manufacturers (the Boeing Company and Lockheed Martin Corporation). This 6-year, nearly $300 million program will address local air-quality concerns by developing technologies to significantly reduce nitrogen oxide (NOx) emissions. In addition, it will provide critical propulsion technologies to dramatically increase performance as measured in fuel burn reduction that will enable reductions of carbon dioxide (CO2) emissions. This is necessary to address the potential climate impact of long-term aviation growth.

Manthey, Lori A.↗

NASA NTRS2011

A Focus on Cryogenic Engineering for the Primordial Inflation Polarization Explorer (PIPER) Mission

Cryogenic engineering involves design and modification of equipment that is used under boiling point of nitrogen which is 77 K. The focus of this paper will be on the design of hardware for cryogenic use and a retrofit that was done to the main laboratory cryostat used to test flight components for the Primordial Inflation Polarization Explorer balloon-borne mission. Data from prior tests showed that there was a superfluid helium leak and a total disassemble of the cryostat was conducted in order to localize and fix the leak. To improve efficiency new fill tubes and clamps with modifications were added to the helium tank. Upon removal of the tank, corrosion was found on the flange face that connects to the helium cold plate and therefore had to be fully replaced and copper plated to prevent future corrosion. Indium seals were also replaced for the four fill tubes, a helium level sensor, and the nitrogen and helium tanks. Four additional shielded twisted pairs of cryogenic wire and a wire harness for the Superconducting Quantum Interference Devices (SQUIDs) were added. Finally, there was also design work done for multiple pieces that went inside the cryostat and a separate probe used to test the SQUIDs. Upon successful completion of the cryostat upgrade, tests were run to check the effectiveness and stability of the upgrades. The post-retrofit tests showed minor leaks were still present and due to this, superfluidity has still not been attained. As such there could still be a possibility of a superfluid leak appearing in the future. Regardless, the copper plating on the helium tank has elongated the need to service it by three to five years.

Rosas, Rogelio↗

NASA NTRS1980

Mechanisms of nitrogen heterocycle influence on turbine fuel stability

Lewis bases were extracted from a Utah COED syncrude via ligand exchange. Addition of this extract to Jet A at levels as low as 5 ppm N produced deterioration of stability in both JFTOT and accelerated storage tests (7 days at 394 K with 13:1air to fuel ratio). Comparable effects on Jet A stability were obtained by addition of pyridine and quinoline, while pyrrole and indole were less detrimental at the same concentration level. The weight of deposit produced accelerated storage tests was found to be proportional to the concentration of added nitrogen compound. Over the narrow temperature range accessible with the experimental method, Arrhenius plots obtained by assuming specific rate to be proportional to the weight of material deposited in seven days exhibit greater slopes in the presence of those nitrogen compounds producing the greater deposition rates. It is shown that despite variation in appearance the elemental composition and spectral characteristics of the deposits are unaffected by addition of the nitrogen compounds. The linearity of the Arrhenius plots and of a plot of Arrhenius slope versus intercept for all the compounds suggests a constancy of mechanism over the range of temperature and heterocycles studied.

Daniel, S. R.↗

DOE OSTI2026

Data for Impacts of Legacy and Contemporary Nitrogen Inputs on N2O and CO2 Emissions in Miscanthus and Maize Cultivated Soils

Nutrient inputs influence the sustainability of bioenergy crop production through contemporary (shortly after addition) and legacy effects (persisting over years) on microbial nitrogen (N) and carbon cycling, which contribute to greenhouse gas emissions. However, the relative importance of contemporary and legacy effects and how that could vary by crop functional types is poorly understood. Considering its rhizomatous roots and perennial growth, we hypothesized that Miscanthus × giganteu s ( M × g ) would be more sensitive to legacy N fertilization and the historical context of its environment than an annual crop like maize. To test this hypothesis, we examined the effects of legacy and contemporary N inputs on nitrous oxide (N2O) and carbon dioxide (CO2) emissions, as well as key N cycling genes in soils where M × g and maize were grown. A 150-day soil incubation experiment was conducted using soils from a long-term M × g and maize fertility experiment with three historic N fertilization rates (0, 112, and 336 kg N ha−1 year−1) and a contemporary amendment (60 mg N kg−1) with negative control (0 mg N kg−1). We observed significant increases in cumulative N2O emissions in M × g soils relative to maize soils, particularly at higher legacy fertilization rates, while contemporary N had no significant effect. Bacterial amoA gene abundance, which plays a significant role in nitrification in nutrient-rich soils, also increased with higher legacy fertilization rates in M × g soils but was unaffected by the contemporary N. In maize soils, legacy and contemporary N did not significantly affect N2O emissions, but cumulative CO2 emissions and amoA gene abundance significantly increased. The abundances of norB genes were not significantly influenced by either legacy fertilization or contemporary N amendments in either soil. Our findings demonstrate the greater importance of fertilization history over contemporary N in mediating soil N2O emissions, particularly for perennial bioenergy crops.

Carbon↗

NASA NTRS1993

Implantation of nitrogen: Effects of hydrogen and implantation energy

To solve the question on solar nitrogen in lunar soils, i.e. variation in isotopic composition and apparently high retentivity compared with rare gases, nitrogen implantation experiments were conducted. At the Meteoritical Society Meeting in Copenhagen, the results of stepped combustion of implanted nitrogen in ilmenite and olivine were presented. The degassing behavior of nitrogen (and also Ar) was quite different from that observed in the case of lunar soils. Extraction temperatures are higher (greater than 1100 C for ilmenite and 1500 C for olivine) than that for lunar soils. Both nitrogen and Ar seem to be retained at the same efficiency. Therefore, additional experiments were conducted to make degassing behavior of nitrogen more close to that observed in the case of lunar soils.

Sugiura, Naoji↗

NASA NTRS1977

Effects of Fe2O3 addition on the nitridation of silicon powder

The reaction of silicon powder and nitrogen was studied in the range of 1300-1400 C. When an addition of Fe2O3 was more than 0.8wt%, the reaction was linear and compared to samples with no Fe2O3, the reaction velocity increased 5 to 10 times. The reactions were mediated by the process of peeling and cracking in a thin layer of Si2N4 formed on the silicon particles or on the surface of the Fe-Si melts. As the addition of Fe2O3 increased, the reaction activation energy for highly pure samples decreased. Fe2O3 which exceeded the Si3N4 solubility limits was finally converted to d-Fe.

Hasegawa, Y.↗

DOE OSTI2022

Air resonance enhanced multiphoton ionization tagging velocimetry

Air resonance enhanced multiphoton ionization (REMPI) tagging velocimetry (ART) was demonstrated in quiescent and supersonic flows. The ART velocimetry method utilizes a wavelength tunable laser beam to resonantly ionize molecular oxygen in air and generate additional avalanche-type ionization of molecular nitrogen. The fluorescence emissions from the first negative and first positive bands of molecular nitrogen are, thus, produced and used for flow tagging. Detailed characterization of ART was conducted, including the effects of oxygen resonance to fluoresce nitrogen, nitrogen fluorescence spectrum, laser energy deposition into quiescent flow showing minimal perturbations in flow, fluorescence lifetime study at various pressures, and line tagging without breakdown. Pointwise velocity measurements within a supersonic flow from a nominal Mach 1.5 nozzle have been conducted and characterized.

Clark, Aleksander↗