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All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Behavior of molecules on interstellar grains - Application of the Langevin equation and iterative extended Hueckel

The Langevin equation was used to explore an adsorbate desorption mechanism. Calculations were performed using iterative extended Hueckel on a silica model site with various small adsorbates, e.g., H, CH, OH, NO, CO. It was found that barriers to free traversal from one site to another are substantial (about 3-10 eV). A bootstrap desorption mechanism for some molecules in the process of forming at a site also became apparent from the calculations. The desorption mechanisms appear to be somewhat balanced by a counterforce - the attraction of sites for the newly desorbed molecule. The order of attraction to a silica grain site for the diatomic molecules considered was OH greater than CH greater than CO greater than NO, when these entities were sufficiently distant. The nature of the silica grain and that of the 'cold' desorption mechanism, when considered together, suggest that the abundance of very small grains might be less common than anticipated.

Aronowitz, S.↗
NASA NTRS1976

IR pumped third-harmonic generation and sum-frequency generation in diatomic molecules

The potential efficiency of using nonlinear up-conversion techniques for the high efficiency type lasers (CO,CO2, and chemical) is assessed. Results indicate that: the small pump photon energy necessitates the use of molecular media for conversion if resonance enhancement is to be used and that molecular systems present several problems. These difficulties include: their levels are complex; their transition probabilities are often unknown; and the oscillator strengths among vibrational levels in the ground electronic state of a molecule are much smaller than those among electronic states of an atom, thus limiting the magnitude of nonlinear interactions. It is shown that this problem can be eliminated by making use of vibronic transitions which, being primarily electronic transitions have much larger matrix elements and efficient conversion can be achieved with molecular systems.

She, C. Y.↗
NASA NTRS1974

An inversion in the atmosphere of Titan

A very detailed greenhouse model derives a methane to hydrogen ratio of unity and a minimum surface pressure of 0.4 atm. Based on a surface gravity g = 140 cm sec/2, the minimum CH4 abundance is 30-40 km-A and the minimum H2 abundance varies from 15 to 85 km-A. A model of the atmosphere of Titan is proposed which seems to be consistent with observations and requires a much smaller CH4 abundance (of the order or 2 km-atm). Although no H2 is required, the presence of some H2 is readily accommodated. In this model, a temperature inversion exists in the atmosphere due to absorption of blue and ultraviolet solar radiation by small particles. The absorbed radiation is re-radiated by the dust and by molecules having long wavelength bands such as CH4 7.7 micrometer and ethane at 12.2 micrometer. The brightness temperature at 20 micrometer is primarily due to re-radiation by the dust.

Danielson, R. E.↗
NASA NTRS1977

What's new on the moon. II

Apollo missions and returned lunar samples have provided new information about the moon, the earth, the sun, and the universe. Analyses show that all the planets were formed by the rapid accumulation of small bodies into larger ones about 4.6 billion years ago. The existence of simple molecules formed by reactions between the soil particles and atoms of carbon, oxygen, and nitrogen that have come from the sun, suggests that the basic ingredients for life are common in the universe. The ratio of hydrogen to helium in the solar wind reaching the moon is found to be 20 to 1, whereas the earth-based measurements show this ratio to be 10 to 1. Although the moon does not have any magnetic field at the present, the analyses revealed the existence of such a field three billion years ago. The understanding of the reasons for the disappearance of this field is vital for understanding planetary magnetic fields. The determination of the chemical composition of the whole moon, the explanation of the moon's observed asymmetry, and the understanding of the nature of moon's interior will have to be achieved by future, possibly unmanned, missions.

French, B. M.↗
NASA NTRS1977

Galatry profile convolved with the Fabry-Perot instrument function

The physical conditions in laboratory gases and in the upper atmosphere of the planets, including earth, can be deduced from a measurement of the intensity and line profile of different radiating molecules. Because of the low pressures in the upper atmospheres, many molecular lines with small pressure-broadening coefficients are collisionally narrowed. These lines are resolvable with a Fabry-Perot interferometer. Analytical expressions are given relating the measured line intensity and profile to the true line intensity and profile. A deconvolution of the measured profile gives the parameters A, beta, and K characterizing the collisionally narrowed Galatry profile. General expressions for the nonideal interferometer are discussed, and, specifically, mirror defects and a limited detector aperture are treated.

Goorvitch, D.↗
NASA NTRS1998

Demonstrations at Supercomputing 1998

Contents of the papers include: Visualization techniques- The next generation, Small-machine visualizing very big data sets, Public display of Lunar Prospector data, Steering molecules via Feel, High-dimensional data browser, Multi-source visualization, Interactive surface flow visualization, and the Virtual Windtunnel.

Bryson, Steve↗
NASA NTRS2014

Rapid Electrochemical Detection and Identification of Microbiological and Chemical Contaminants for Manned Spaceflight Project

Microbial control in the spacecraft environment is a daunting task, especially in the presence of human crew members. Currently, assessing the potential crew health risk associated with a microbial contamination event requires return of representative environmental samples that are analyzed in a ground-based laboratory. It is therefore not currently possible to quickly identify microbes during spaceflight. This project addresses the unmet need for spaceflight-compatible microbial identification technology. The electrochemical detection and identification platform is expected to provide a sensitive, specific, and rapid sample-to-answer capability for in-flight microbial monitoring that can distinguish between related microorganisms (pathogens and non-pathogens) as well as chemical contaminants. This will dramatically enhance our ability to monitor the spacecraft environment and the health risk to the crew. Further, the project is expected to eliminate the need for sample return while significantly reducing crew time required for detection of multiple targets. Initial work will focus on the optimization of bacterial detection and identification. The platform is designed to release nucleic acids (DNA and RNA) from microorganisms without the use of harmful chemicals. Bacterial DNA or RNA is captured by bacteria-specific probe molecules that are bound to a microelectrode, and that capture event can generate a small change in the electrical current (Lam, et al. 2012. Anal. Chem. 84(1): 21-5.). This current is measured, and a determination is made whether a given microbe is present in the sample analyzed. Chemical detection can be accomplished by directly applying a sample to the microelectrode and measuring the resulting current change. This rapid microbial and chemical detection device is designed to be a low-cost, low-power platform anticipated to be operated independently of an external power source, characteristics optimal for manned spaceflight and areas where power and computing resources are scarce.

Pierson, Duane↗
NASA NTRSDate not supplied

Exploring the Atmosphere of Uranus with Small Next-generation Atmospheric Probe (SNAP)

In-situ atmospheric exploration of giant planets is a top priority of the planetary science community and NASA. The Galileo Probe a Jupiter made the first and only in-situ composition measurements of the atmosphere. Most importantly, the noble gas and isotopic ratio can be made only through in-situ measurements, and the Galileo Probe measurements must be followed up by similar measurements at Saturn, Uranus, and Neptune. In addition, abundances of condensable cloud-forming species are also needed to measure the vertical distribution of those molecules to provide ground-truths measurements for remote-sensing measurements. My talk will focus on the Small Next-generation Atmospheric Probe (SNAP) design developed in partnership by Hampton University and NASA Langley Research Center to enable delivery of multiple probes. Using SNAP as a reference design, I will also discuss key instrument trades and the state of the art in the atmospheric composition instruments.

Kunio Sayanagi↗
NASA NTRS2011

Axisymmetric Implementation for 3D-Based DSMC Codes

The primary objective in developing NASA s DSMC Analysis Code (DAC) was to provide a high fidelity modeling tool for 3D rarefied flows such as vacuum plume impingement and hypersonic re-entry flows [1]. The initial implementation has been expanded over time to offer other capabilities including a novel axisymmetric implementation. Because of the inherently 3D nature of DAC, this axisymmetric implementation uses a 3D Cartesian domain and 3D surfaces. Molecules are moved in all three dimensions but their movements are limited by physical walls to a small wedge centered on the plane of symmetry (Figure 1). Unfortunately, far from the axis of symmetry, the cell size in the direction perpendicular to the plane of symmetry (the Z-direction) may become large compared to the flow mean free path. This frequently results in inaccuracies in these regions of the domain. A new axisymmetric implementation is presented which aims to solve this issue by using Bird s approach for the molecular movement while preserving the 3D nature of the DAC software [2]. First, the computational domain is similar to that previously used such that a wedge must still be used to define the inflow surface and solid walls within the domain. As before molecules are created inside the inflow wedge triangles but they are now rotated back to the symmetry plane. During the move step, molecules are moved in 3D but instead of interacting with the wedge walls, the molecules are rotated back to the plane of symmetry at the end of the move step. This new implementation was tested for multiple flows over axisymmetric shapes, including a sphere, a cone, a double cone and a hollow cylinder. Comparisons to previous DSMC solutions and experiments, when available, are made.

Stewart, Benedicte↗
NASA NTRS2009

Microfluidic Extraction of Biomarkers using Water as Solvent

A proposed device, denoted a miniature microfluidic biomarker extractor (mu-EX), would extract trace amounts of chemicals of interest from samples, such as soils and rocks. Traditionally, such extractions are performed on a large scale with hazardous organic solvents; each solvent capable of dissolving only those molecules lying within narrow ranges of specific chemical and physical characteristics that notably include volatility, electric charge, and polarity. In contrast, in the mu-EX, extractions could be performed by use of small amounts (typically between 0.1 and 100 L) of water as a universal solvent. As a rule of thumb, in order to enable solvation and extraction of molecules, it is necessary to use solvents that have polarity sufficiently close to the polarity of the target molecules. The mu-EX would make selection of specific organic solvents unnecessary, because mu-EX would exploit a unique property of liquid water: the possibility of tuning its polarity to match the polarity of organic solvents appropriate for extraction of molecules of interest. The change of the permittivity of water would be achieved by exploiting interactions between the translational states of water molecules and an imposed electromagnetic field in the frequency range of 300 to 600 GHz. On a molecular level, these interactions would result in disruption of the three-dimensional hydrogen-bonding network among liquid-water molecules and subsequent solvation and hydrolysis of target molecules. The mu-EX is expected to be an efficient means of hydrolyzing chemical bonds in complex macromolecules as well and, thus, enabling analysis of the building blocks of these complex chemical systems. The mu-EX device would include a microfluidic channel, part of which would lie within a waveguide coupled to an electronically tuned source of broad-band electromagnetic radiation in the frequency range from 300 to 600 GHz (see figure). The part of the microfluidic channel lying in the waveguide would constitute an interaction volume. The dimensions of the interaction volume would be chosen in accordance with the anticipated amount of solid sample material needed to ensure extraction of sufficient amount of target molecules for detection and analysis. By means that were not specified at the time of reporting the information for this article, the solid sample material would be placed in the interaction volume. Then the electromagnetic field would be imposed within the waveguide and water would be pumped through the interaction volume to effect the extraction.

Amashukeli, Xenia↗
NASA NTRS1975

Observations of the interstellar gas with the Copernicus satellite

Results are reviewed for Copernicus far-UV measurements of the absorption lines of H I, D I, H2, and heavier elements in the interstellar gas. Column densities along several lines of sight, as estimated from Ly-alpha absorption-line profiles, confirm that wide differences in the gas density are present in various directions. The measurement of interstellar D I implies an open universe unless alternate sources for this nuclide are found. Analysis of reddened stars for which the line of sight passes through one or more interstellar clouds indicates a depletion of several heavy elements in the gas. It is suggested that the depleted elements may be present in grains rather than molecules and that the intercloud medium may consist primarily of H II with a few small H I clouds.

Morton, D. C.↗
NASA NTRS1984

IUE Observations of the Gaseous Component of the Local Interstellar Medium

Discovery of interstellar Ge, Ga, and Kr is reported. Several intercombination lines of Fe 2 are detected. The depletion is most pronounced in Ca, Ti, and V. The highly ionized gas C 4 and Si 4 is not co-extensive with the Si 2 and C 2 gas nor with the O 6 gas. The molecular gas (CO) shows very small velocity dispersion (b approximately 1 km/sec). HD 149404 has the richest interstellar spectrum (except molecules) of all the stars in this study. HD 147889, the heavily obscured star in the Rho Oph cloud, has the strongest interstellar CO spectrum. Noisy nature of the spectra precludes detection of other molecules.

Gilra, D. P.↗
NASA NTRS1993

Atmospheric Sulfur Hexafluoride: Sources, Sinks and Greenhouse Warming

Model calculations using estimated reaction rates of sulfur hexafluoride (SF6) with OH and 0('D) indicate that the atmospheric lifetime due to these processes may be very long (25,000 years). An upper limit for the UV cross section would suggest a photolysis lifetime much longer than 1000 years. The possibility of other removal mechanisms are discussed. The estimated lifetimes are consistent with other estimated values based on recent laboratory measurements. There appears to be no known natural source of SF6. An estimate of the current production rate of SF6 is about 5 kt/yr. Based on historical emission rates, we calculated a present-day atmospheric concentrations for SF6 of about 2.5 parts per trillion by volume (pptv) and compared the results with available atmospheric measurements. It is difficult to estimate the atmospheric lifetime of SF6 based on mass balance of the emission rate and observed abundance. There are large uncertainties concerning what portion of the SF6 is released to the atmosphere. Even if the emission rate were precisely known, it would be difficult to distinguish among lifetimes longer than 100 years since the current abundance of SF6 is due to emission in the past three decades. More information on the measured trends over the past decade and observed vertical and latitudinal distributions of SF6 in the lower stratosphere will help to narrow the uncertainty in the lifetime. Based on laboratory-measured IR absorption cross section for SF6, we showed that SF6 is about 3 times more effective as a greenhouse gas compared to CFC 11 on a per molecule basis. However, its effect on atmospheric warming will be minimal because of its very small concentration. We estimated the future concentration of SF6 at 2010 to be 8 and 10 pptv based on two projected emission scenarios. The corresponding equilibrium warming of 0.0035 C and 0.0043 C is to be compared with the estimated warming due to CO2 increase of about 0.8 C in the same period.

Sze, Nien Dak↗
NASA NTRS2004

Soft ionization device with characterization systems and methods of manufacture

Various configurations of characterization systems such as ion mobility spectrometers and mass spectrometers are disclosed that are coupled to an ionization device. The ionization device is formed of a membrane that houses electrodes therein that are located closer to one another than the mean free path of the gas being ionized. Small voltages across the electrodes generate large electric fields which act to ionize substantially all molecules passing therethrough without fracture. Methods to manufacture the mass spectrometer and ion mobility spectrometer systems are also described.

Hartley, Frank T.↗
NASA NTRS1986

Carbon monoxide production in low energy oxygen ion bombardment of pyrolytic graphite and Kapton surfaces

The results of an investigtion of the interaction of low energy oxygen ions with pyrolytic graphite and Kapton surface are reported. CO molecules emitted from the surface as a result of the ion bombardment were detected by a mass spectrometer. Because the ion-induced signals were small compared to that arising from the CO background pressure in the vacuum system, the ion beam was modulated and the modulated component of the CO signal measured with a lock-in amplifier. The quantum yield (CO molecules emitted per incident oxygen ion) for graphite rose from 1.9 at 4.5 eV ion energy to 6.6 at 465 eV. Comparable yields were obtained for Kapton. The large size of the yields suggests contributions to the reaction process from the background O2 molecules in the vacuum system.

Horton, C. C.↗
NASA NTRS1994

Infrared spectoscopy of Triton and Pluto ice analogs: The case for saturated hydrocarbons

The infrared transmission spectra and photochemical behavior of various organic compounds isolated in solid N2 ices, appropriate for applications to Triton ad Pluto, are presented. It is shown that excess absorption in the surface spectra of Triton and Pluto, i.e., absorption not explained by present models incorporating molecules already identified on these bodies (N2, CH4, CO, and CO2), that starts near 4450/cm (2.25 microns) and extends to lower frequencies, may be due to alkanes (C(n)H(2n+2)) and related molecules frozen in the nitrogen. Branched and linear alkanes may be responsible. Experiments in which the photochemstry of N2: CH4 and N2: CH4: CO ices was explored demonsrtrate that the surface ices of Triton and Pluto may contain a wide variety of additional species containing H, C, O, and N. Of these, the reactive molecule diazomethane, CH2N2, is particularly important since it may be largely responsible for the synthesis of larger alkanes from CH4 and other small alkanes. Diazomethane would also be expected to drive chemical reactions involving organics in the surface ices of Triton and Pluto toward saturation, i.e., to reduce multiple CC bonds. The positions and intrinsic strengths (A values) of many of the infrared absorption bands of N2 matrix-isolated molecules of relevance to Triton and Pluto have also been determined. These can be used to aid in their search and to place constraints on their abundances.

Bohn, Robert B.↗
NASA NTRS2007

Anti-radiation vaccine: Immunologically-based Prophylaxis of Acute Toxic Radiation Syndromes Associated with Long-term Space Flight

Protecting crew from ionizing radiation is a key life sciences problem for long-duration space missions. The three major sources/types of radiation are found in space: galactic cosmic rays, trapped Van Allen belt radiation, and solar particle events. All present varying degrees of hazard to crews; however, exposure to high doses of any of these types of radiation ultimately induce both acute and long-term biological effects. High doses of space radiation can lead to the development of toxicity associated with the acute radiation syndrome (ARS) which could have significant mission impact, and even render the crew incapable of performing flight duties. The creation of efficient radiation protection technologies is considered an important target in space radiobiology, immunology, biochemistry and pharmacology. Two major mechanisms of cellular, organelle, and molecular destruction as a result of radiation exposure have been identified: 1) damage induced directly by incident radiation on the macromolecules they encounter and 2) radiolysis of water and generation of secondary free radicals and reactive oxygen species (ROS), which induce chemical bond breakage, molecular substitutions, and damage to biological molecules and membranes. Free-radical scavengers and antioxidants, which neutralize the damaging activities of ROS, are effective in reducing the impact of small to moderate doses of radiation. In the case of high doses of radiation, antioxidants alone may be inadequate as a radioprotective therapy. However, it remains a valuable component of a more holistic strategy of prophylaxis and therapy. High doses of radiation directly damage biological molecules and modify chemical bond, resulting in the main pathological processes that drive the development of acute radiation syndromes (ARS). Which of two types of radiation-induced cellular lethality that ultimately develops, apoptosis or necrosis, depends on the spectrum of incident radiation, dose, dose rate, and functional conditions of impacted cells/organisms. The administration of an experimental anti-radiation vaccine may provide an immunologically based, adjunct method of prevention or prophylaxis against clinical ARS. The administration of experimental anti-radiation serum (ARS) and the use of the blood dialysis methods, such as immune plasma-sorption, may assist in the clearance of radiation-specific toxins and may enhance established strategies for the mitigation of the biological effects leading to ARS, and should be evaluated for use on exploration-class space missions.

Popov, Dmitri↗