SEARCH · Engineering Papers

Results for “ISM”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9

All sources NASA NTRS DOE OSTI

NASA NTRS2001

Detecting and Identifying Organic Molecules in Space - The AstroBiology Explorer (ABE) MIDEX Mission Concept

Infrared spectroscopy in the 2.5-16 micron (4000-625/cm) range is a principle means by which organic compounds are detected and identified in space. Ground-based, airborne, and spaceborne IR spectral studies have already demonstrated that a significant fraction of the carbon in the interstellar medium (ISM) resides in the form of complex organic molecular species. Unfortunately, neither the distribution of these materials nor their genetic and evolutionary relationships with each other or their environments are well understood. The Astrobiology Explorer (ABE) is a MIDEX (Medium-class Explorer) mission concept currently under study at NASA's Ames Research Center in collaboration with Ball Aerospace and Technologies Corporation. ABE will conduct IR spectroscopic observations to address outstanding important problems in astrobiology, astrochemistry, and astrophysics. The core observational program would make fundamental scientific progress in understanding (1) the evolution of ices and organic matter in dense molecular clouds and young forming stellar systems, (2) the chemical evolution of organic molecules in the ISM as they transition from AGB outflows to planetary nebulae to the general diffuse ISM to H II regions and dense clouds, (3) the distribution of organics in the diffuse ISM, (4) the nature of organics in the Solar System (in comets, asteroids, satellites), and (5) the nature and distribution of organics in local galaxies. Both the scientific goals of the mission and how they would be achieved will be discussed.

Sandford, Scott A.↗

NASA NTRS1995

Chemical Evolution of Interstellar Dust into Planetary Materials

Comets are believed to retain some interstellar materials, stored in fairly pristine conditions since-their formation. The composition and properties of cometary dust grains should reflect those of grains in the outer part of the protosolar nebula which, at least in part, were inherited from the presolar molecular cloud. However, infrared emission features in comets differ from their interstellar counterparts. These differences imply processing of interstellar material on its way to incorporation in comets, but C and N appear to be retained. Overall dust evolution from the interstellar medium (ISM) to planetary materials is accompanied by an increase in proportion of complex organics and a decrease in pure carbon phases. The composition of cometary dust grains was measured in situ during fly-by missions to comet Halley in 1986. The mass spectra of about 5000 cometary dust grains with masses of 5 x 10(exp -17) - 5 x 10(exp -12) g provide data about the presence and relative abundances of the major elements H, C, N, O,Na, Mg, Al, Si, S, Cl, K, Ca, Ti, Cr, Fe, Ni. The bulk abundances of major rock-forming elements integrated over all spectra were found to be solar within a factor of 2, while the volatile elements H, C, N, O in dust are depleted in respect to their total cosmic abundances. The abundances of C and N in comet dust are much closer to interstellar than to meteoritic and are higher than those of dust in the diffuse ISM. In dense molecular clouds dust grains are covered by icy mantles, the average composition of which is estimated to be H:C:N:O = 96:14:1:34. Up to 40% of elemental C and O may be sequestered in mantles. If we use this upper limit to add H, C, N and O as icy mantle material to the abundances residing in dust in the diffuse ISM, then the resulting values for H. C, and N match cometary abundances. Thus, ice mantles undergoing chemical evolution on grains in the dense ISM appear to have been transformed into less volatile and more complex organic residues wherein the H, C and N are largely retained and ultimately accreted in cometary dust. The abundance of O is about the same for cometary dust, meteorites and interstellar dust. In all these samples, most of O in a solid phase is bonded to silicates. In dense molecular clouds, the abundance of O in dust+mantles is significantly higher then in cometary dust. This difference may reflect the greater lability of oxygenated species toward astrophysical processing. Laboratory studies show that O-bearing functional groups in organic compounds tend to be relatively easily removed by heating and/or UV and particle irradiation . In Halley's coma, O-containing organic grains, being unstable, were located closest to the nucleus. The decomposition of the organic grain component in the coma provided a significant extended source contribution to O-containing gaseous species such as CO and H2CO.

Fomenkova, M. N.↗

NASA NTRS1995

Polarimetry of the Interstellar Medium

The talk will review what is known about the composition of ices and organics in the dense and diffuse interstellar media (ISM). Mixed molecular ices make up a significant fraction of the solid materials in dense molecular clouds and it is now known that thermal and radiation processing of these ices results in the production of more complex organic species, some of which may survive transport into forming stellar systems and the diffuse ISM. Molecular species identified in interstellar ices include H2O, CH3OH, CO, CH4, CO2, and somewhat surprisingly, H2. Theoretical and laboratory studies of the processing of interstellar analog ices containing these species indicate that species like HCO, H2CO, CH3, and NH3 are readily made and should also be present. The irradiation of mixed molecular ices containing these species, when followed by warming, leads to the production of a large variety of more complex species, including ethanol (CH3CH2OH), formamide (HC(=O)NH2), acetamide (CH3C(=O)NH2), nitriles or isonitriles (R-CN or R-NC hexamethylenetetramine (HMT; C6H12N4), a number of polymeric species related to polyoxymethylene [POM,(-CH2O-)n], and ketones {R-C(=O)-R'}. Spectral studies of dust in the diffuse ISM indicate the presence of fairly complex organics, some of which may be related to the organics produced in dense molecular clouds. Spectral comparisons indicate that the diffuse ISM organics may be quite similar to meteoritic kerogens, i.e. they may consist largely of aromatic moieties interlinked by short aliphatic bridges. Interestingly, recent evidence indicates that the galactic distribution of this material closely matches that of silicates, but does not correlate directly with visual extinction. This implies that a large fraction of the visual extinction is caused by a material other than these organics and silicates and that this other material has a significantly different distribution within the galaxy.

Sandford, Scott↗

NASA NTRS1998

Fifteen Years of Laboratory Astrophysics at Ames

Tremendous strides have been made in our understanding of interstellar material over the past fifteen years thanks to significant, parallel developments in two closely related areas: observational astronomy and laboratory astrophysics. Fifteen years ago the composition of interstellar dust was largely guessed at, the concept of ices in dense molecular clouds ignored, and the notion of large, abundant, gas phase, carbon-rich molecules widespread throughout the interstellar medium (ISM) considered impossible. Today the composition of dust in the diffuse ISM is reasonably well constrained to cold refractory materials comprised of amorphous and crystalline silicates mixed with an amorphous carbonaceous material containing aromatic structural units and short, branched aliphatic chains. In the dense ISM, these cold dust particles are coated with mixed-molecular ices whose compositions are very well known. Lastly, the signature of carbon-rich polycyclic aromatic hydrocarbons (PAHs), shockingly large molecules by early interstellar chemistry standards, is widespread throughout the ISM. This great progress has only been made possible by the close collaboration of laboratory experimentalists with observers and theoreticians, all with the goal of applying their skills to astrophysical problems of direct interest to NASA programs. Such highly interdisciplinary collaborations ensure fundamental, in depth coverage of the wide-ranging challenges posed by astrophysics. These challenges include designing astrophysically focused experiments and data analysis, tightly coupled with astrophysical searches spanning 2 orders of magnitude in wavelength, and detailed theoretical modeling. The impact of our laboratory has been particularly effective as there is constant cross-talk and feedback between quantum theorists; theoretical astrophysicists and chemists; experimental physicists; organic, physical and petroleum chemists; and infrared and UV/Vis astronomers. In this paper, two examples of the Ames Program will be given. We have been involved in identifying 9 out of the 14 interstellar pre-cometary ice species known, determined their abundances and the physical nature of the ice structure. Details on our ice work are given in the paper by Sandford et al. Our group is among the pioneers of the PAH model. We built the theoretical framework, participated in the observations and developed the experimental techniques needed to test the model. We demonstrated that the ubiquitous infrared emission spectrum associated with many interstellar objects can be matched by laboratory spectra of neutral and positively charged PAHs and that PAHs were excellent candidates for the diffuse interstellar band (DIB) carriers. See Salama et al. and Hudgins et al.

Allamandola, L. J.↗

NASA NTRS2002

Gas Phase Spectroscopy of Cold PAH Ions: Contribution to the Interstellar Extinction and the Diffuse Interstellar Bands

Polycyclic Aromatic Hydrocarbon molecules (PAHs) are ubiquitous in the interstellar medium (ISM) and constitute the building blocks of interstellar dust grains. Despite their inferred important role in mediating the energetic and chemical processes in thc ISM, their exact contribution to the interstellar extinction, and in particular to the diffuse interstellar bands (DIBs) remains unclear. The DIBs are spectral absorption features observed in the line of sight of stars that are obscured by diffuse interstellar clouds. More than 200 bands have been reported to date spanning from the near UV to the near IR with bandwidths ranging from 0.4 to 40 Angstroms (Tielens & Snow 1995). The present consensus is that the DIBs arise from free flying, gas-phase, organic molecules and/or ions that are abundant under the typical conditions reigning in the diffuse ISM. PAHs have been proposed as possible carriers (Allamandola et al. 1985; Leger & DHendecourt 1985). The PAH hypothesis is consistent with the cosmic abundance of Carbon and Hydrogen and with the required photostability of the DIB carriers against the strong VUV radiation field in the diffuse interstellar clouds. A significant fraction of PAHs is expected to be ionized in the diffuse ISM.

Biennier, L.↗

NASA NTRS2003

Interstellar Deuterium Chemistry

The presence of isotopic anomalies is the most unequivocal demonstration that meteoritic material contains circumstellar or interstellar components. In the case of organic compounds in meteorites and interplanetary dust particles (IDPs), the most useful isotopic tracer of interstellar components has been deuterium (D) excesses. In some cases these enrichments are seen in bulk meteoritic materials, but D enrichments have also been observed in meteoritic subfractions and even within specific classes of molecular species, such as amino and carboxylic acids. These anomalies are not thought to be the result of nucleosynthetic processes, but are instead ascribed to chemical and physical processes occurring in the interstellar medium (ISM). The traditional explanation of these D excesses has been to invoke the presence of materials made in the ISM by low temperature gas phase ion-molecule reactions. Indeed, the DM ratios seen in the simple interstellar gas phase molecules in cold dense clouds amenable to measurement using radio spectral techniques are generally considerably higher than the values seen in enriched Solar System materials. However, the true linkage between the DM ratios in interstellar and meteoritic materials is obscured by several effects. First, current observations of D enrichment in the ISM have been made of only a few simple molecules, molecules that are not the main carriers of D in Solar System materials. Second, some of the interstellar D enrichment is likely to reside on labile moieties that will have exchanged to some degree with more isotopically normal material during incorporation into the warm protosolar nebula, parent body processing, delivery, recovery, and analysis. Third, ion-molecule reactions represent only one of at least four processes that can produce strong D-H fractionation in the ISM.

Sandford, S. A.↗

NASA NTRS2004

The AstroBiology Explorer (ABE) Mission Concept

Infrared spectroscopy in the 2.5-16 micron range is a principle means by which organic compounds can be detected and identified in space via their vibrational transitions. Ground-based, airborne, and spaceborne IR spectral studies have already demonstrated that a significant fraction of the carbon in the interstellar medium (ISM) resides in the form of complex organic molecular species. Unfortunately, neither the distribution of these materials nor their genetic and evolutionary relationships with each other or their environments are well understood. The Astrobiology Explorer (ABE) is a MIDEX mission concept currently under study by a team of partners: NASA's Ames Research Center, Ball Aerospace and Technologies Corporation, and the Jet Propulsion Laboratory. ABE will conduct IR spectroscopic observations to address outstanding important problems in astrobiology, astrochemistry, and astrophysics. The core observational program would make fundamental scientific progress in understanding (1) The evolution of ices and organic matter in dense molecular clouds and young forming stellar systems, (2) The chemical evolution of organic molecules in the ISM as they transition from AGB outflows to planetary nebulae to the general diffuse ISM to HII regions and dense clouds, (3) The distribution of organics in the diffuse ISM, (4) The nature of organics in the Solar System (in comets, asteroids, satellites), and (5) The nature and distribution of organics in local galaxies. The technical considerations of achieving these science objectives in a MIDEX-sized mission will be presented.

Sandford, Scott A.↗

NASA NTRS2003

The High-Excitation Planetary Nebula NCG 246: Optical and Near-Ultraviolet Observations and Two-dimensional Numerical Models

We have imaged the planetary nebula (PN) NGC 246 in the near-ultraviolet wavelengths [Ne v] 342.6 nm, the Bowen fluorescence line of 0 111 at 344.4 nm, and a nearby line-free region centered on 338.6 nm, as well as H(alpha), [O III] 500.7 nm, and [S II] 673.0 and 671.5 nm. Imaging in the 344.4 nm line is necessary to deconvolve contamination of the [Ne v] images by O III 342.9 nm. The emission from the shell and inner parts of the nebula is detected in [Ne v]. The radial profiles of the [Ne v] brightness decrease with radius from the exciting star, indicating that the bulk of the emission from this ion is due to the hard UV stellar radiation field, with a (probably) marginal contribution from collisional ionization in a shock between the PN shell and the interstellar medium (ISM). In contrast, the radial profiles of the emission in H(alpha), [0 III] 500.7 nm, and [S II] are flatter and peak at the location of the shell. The emission of [S II] probably traces the interaction of the PN with the ambient ISM. We also present two-dimensional numerical simulations for this PN-ISM interaction. The simulations consider the stellar motion with respect to the ambient ISM, with a velocity of 85 km/s , and include the time evolution of the wind parameters and UV radiation field from the progenitor star.

Szentgyorgyi, Andrew↗

NASA NTRS2006

Laboratory Spectroscopy of CH(+) and Isotopic CH

The A1II - X1(Epsilon) electronic band of the CH(+) ion has been used as a probe of the physical and dynamical conditions of the ISM for 65 years. In spite of being one of the first molecular species observed in the ISM and the very large number of subsequent observations with large derived column densities, the pure rotational spectra of CH+ has remained elusive in both the laboratory and in the ISM as well. We report the first laboratory measurement of the pure rotation of the CH(+) ion and discuss the detection of CH-13(+) in the ISM. Also reported are the somewhat unexpected chemical conditions that resulted in laboratory production.

Pearson, John C.↗

NASA NTRS2011

Possible Charge-Exchange X-Ray Emission in the Cygnus Loop Detected with Suzaku

X-ray spectroscopic measurements of the Cygnus Loop supernova remnant indicate that metal abundances throughout most of the remnant s rim are depleted to approx.0.2 times the solar value. However, recent X-ray studies have revealed in some narrow regions along the outermost rim anomalously "enhanced" abundances (up to approx. 1 solar). The reason for these anomalous abundances is not understood. Here, we examine X-ray spectra in annular sectors covering nearly the entire rim of the Cygnus Loop using Suzaku (21 pointings) and XMM-Newton (1 pointing). We find that spectra in the "enhanced" abundance regions commonly show a strong emission feature at approx.0.7 keV. This feature is likely a complex of He-like O K(gamma + delta + epsilon), although other possibilities cannot be fully excluded. The intensity of this emission relative to He-like O K(alpha) appears to be too high to be explained as thermal emission. This fact, as well as the spatial concentration of the anomalous abundances in the outermost rim, leads us to propose an origin from charge-exchange processes between neutrals and H-like O. We show that the presence of charge-exchange emission could lead to the inference of apparently "enhanced" metal abundances using pure thermal emission models. Accounting for charge-exchange emission, the actual abundances could be uniformly low throughout the rim. The overall abundance depletion remains an open question. Subject headings: ISM: abundances ISM: individual objects (Cygnus Loop) ISM: supernova remnants X-rays: ISM atomic processes

Katsuda, Satoru↗

NASA NTRS2013

The HERschel Inventory of the Agents of Galaxy Evolution in the Magellanic Clouds, a HERschel Open Time Key Program

We present an overview or the HERschel Inventory of The Agents of Galaxy Evolution (HERITAGE) in the Magellanic Clouds project, which is a Herschel Space Observatory open time key program. We mapped the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) at 100, 160, 250, 350, and 500 micron with the Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer (PACS) instruments on board Herschel using the SPIRE/PACS parallel mode. The overriding science goal of HERITAGE is to study the life cycle of matter as traced by dust in the LMC and SMC. The far-infrared and submillimeter emission is an effective tracer of the interstellar medium (ISM) dust, the most deeply embedded young stellar objects (YSOs), and the dust ejected by the most massive stars. We describe in detail the data processing, particularly for the PACS data, which required some custom steps because of the large angular extent of a single observational unit and overall the large amount of data to be processed as an ensemble. We report total global fluxes for LMC and SMC and demonstrate their agreement with measurements by prior missions. The HERITAGE maps of the LMC and SMC are dominated by the ISM dust emission and bear most resemblance to the tracers of ISM gas rather than the stellar content of the galaxies. We describe the point source extraction processing and the critetia used to establish a catalog for each waveband for the HERITAGE program. The 250 micron band is the most sensitive and the source catalogs for this band have approx. 25,000 objects for the LMC and approx. 5500 objects for the SMC. These data enable studies of ISM dust properties, submillimeter excess dust emission, dust-to-gas ratio, Class 0 YSO candidates, dusty massive evolved stars, supemova remnants (including SN1987A), H II regions, and dust evolution in the LMC and SMC. All images and catalogs are delivered to the Herschel Science Center as part of the conummity support aspects of the project. These HERITAGE images and catalogs provide an excellent basis for future research and follow up with other facilities.

AGENTS↗

NASA NTRS2017

NASA's In-Space Manufacturing Project: Materials and Manufacturing Process Development Update

The mission of NASA's In-Space Manufacturing (ISM) project is to identify, design, and implement on-demand, sustainable manufacturing solutions for fabrication, maintenance and repair during exploration missions. ISM has undertaken a phased strategy of incrementally increasing manufacturing capabilities to achieve this goal. The ISM project began with the development of the first 3D printer for the International Space Station. To date, the printer has completed two phases of flight operations. Results from phase I specimens indicated some differences in material properties between ground-processed and ISS-processed specimens, but results of follow-on analyses of these parts and a ground-based study with an equivalent printer strongly indicate that this variability is likely attributable to differences in manufacturing process settings between the ground and flight prints rather than microgravity effects on the fused deposition modeling (FDM) process. Analysis of phase II specimens from the 3D Printing in Zero G tech demo, which shed further light on the sources of material variability, will be presented. The ISM project has also developed a materials characterization plan for the Additive Manufacturing Facility, the follow-on commercial multimaterial 3D printing facility developed for ISS by Made in Space. This work will yield a suite of characteristic property values that can inform use of AMF by space system designers. Other project activities include development of an integrated 3D printer and recycler, known as the Refabricator, by Tethers Unlimited, which will be operational on ISS in 2018. The project also recently issued a broad area announcement for a multimaterial fabrication laboratory, which may include in-space manufacturing capabilities for metals, electronics, and polymeric materials, to be deployed on ISS in the 2022 timeframe.

Prater, Tracie↗

NASA NTRS2017

Radiation Processing of Polycyclic Aromatic Hydrocarbons (PAHs) in Space: ICEE PoC

Small Polycyclic Aromatic Hydrocarbon molecules or PAHs (<30 carbon atoms) have been identified in comets, meteorites, asteroids, and interplanetary dust particles in our Solar System, while PAHs in the Interstellar Medium (ISM) tend to be much larger, usually between 50 to 100 carbon atoms in size. The cause of the size disparity between PAHs found in the ISM and Solar System as well as their influence on Solar System organics is not yet understood. Two chemical evolutionary paths have been proposed to explain the inventory of solar system organics. In one the prebiotic material was formed from the radiation induced modification of large pre-solar carbon-bearing species (e.g. ISM PAHs). The second path suggests that Solar System prebiotic matter is the result of bottom-up synthesis from small reactive molecules after the Solar System was formed. In this second scenario very few ISM PAHs survived the harsh pre-solar radiation as aromatic structures. ICEE PoC (ICEE Proof of Concept) investigated factors impacting the chemical evolution of large PAHs irradiated under conditions similar to the proto-solar nebula. Likewise ICEE PoC will refine the technical parameters of the proposed ICEE (Institute for Carbon Evolution Experiment) laboratory.

Mattioda, Andrew↗

NASA NTRS2018

Overview of Additive Manufacturing Initiatives at NASA Marshall Space Flight Center

NASA's In Space Manufacturing Initiative (ISM) includes: The case for ISM - why; ISM path to exploration - results from the 3D Printing In Zero-G Technology Demonstration - ISM challenges; In space Robotic Manufacturing and Assembly (IRMA); Additive construction. Additively Manufacturing (AM) development for liquid rocket engine space flight hardware. MSFC standard and specification for additively manufactured space flight hardware. Summary.

Clinton, R. G., Jr.↗

NASA NTRSDate not supplied

Double ChemFET for the In-Line Monitoring of Silver Dosing in Potable Water Systems

With NASA Advanced Exploration Systems (AES) Life Support Systems (LSS)baselining ionic silver (Ag+) as the biocide of choice, development in silver monitoring technologies becomes necessary to monitor and control Ag+ release. Ion-selective field effect transistors (ISFETs) and chemically-sensitive field effect transistors (ChemFETs) are capable of selective detection of Ag+ with reversible and low detection limit responses. However, one major hurdle to ChemFET technologies is the requirement of a reference electrode, which can leak its fill solution into the potable water system and is prone to drift requiring frequent calibration. To circumvent this issue, a double chemically-sensitive field effect transistor (dChemFET) is proposed. The dChemFET uses a second ChemFET to selectively monitor the counter ion and serves in place of the reference electrode. This work reports on the development of the dChemFET, starting with the development of the Ag+ andNO3- ion selective membranes (ISMs) to be used in the ChemFETs. The Ag+ ISM was tested in 50-105 ppb Ag+ and showed linear, sub-Nernstian response. The NO3- ISM was tested in50-500 ppb silver ion equivalents of nitrate ion (Ag+ equiv. of NO3-) and shows linear, sub-Nernstian response as well . However, the Ag+ and NO3- ISMs face significant challenges in terms of drift that obstruct its application for long-term monitoring, but it can serve as a starting point for demonstrating the dChemFET proof of concept.

John Abdou↗

NASA NTRSDate not supplied

Polymer/Regolith Composites for In-Space Manufacturing on the Moon and Mars

In-Space Manufacturing (ISM) is vital to supporting a sustained human presence on the Moon or Mars. With payload launch prices ranging from $4,000 to more than $1 million per kg, reducing payload mass is of critical interest. Using in-situ resources for ISM is particularly attractive as it allows for a system of Earth-independent manufacturing for the Lunar surface, reducing the initial payload mass that is required for current ISM systems that rely on terrestrially synthesized materials. This talk presents new composite materials made from Lunar and Martian regolith and Poly(3-hydroxybutyrate) (PHB), a thermoplastic that offers the ability to be biosynthesized in space using various in-situ resources like organic waste or atmospheric CO2 as feedstock. The addition of regolith provides a route to creating materials with a diverse set of properties which will be discussed. The development of these materials represents the first step in creating a system of closed-loop ISM, which is critical to establishing a lasting human presence in space.

In-situ resource utilization↗

NASA NTRSDate not supplied

Biosynthesized Thermoplastic/Regolith Composites for Closed-Loop In-Space Manufacturing

In situ resource utilization↗

NASA NTRS1977

The interstellar medium in the direction of the Crab Nebula - Reconciling soft X-ray and radio observations

The total soft X-ray photoabsorption cross section of the interstellar medium (ISM) in the direction of the Crab Nebula is computed on the basis of a two-phase model of the ISM. This cross section is used to reanalyze Copernicus data on the X-ray spectrum of the Crab between 0.7 and 1.5 keV. The total hydrogen column density along the line of sight to that nebula is found to be approximately 2.6 by 10 to the 21st power H atoms/sq cm. This result is evaluated in light of the two-phase model of the ISM, and the predictions based on the X-ray data are compared with results of radio and UV observations. A discrepancy between the radio and X-ray measurements of the hydrogen column density is resolved by noting that 21-cm absorption measurements sample only the neutral hydrogen in clouds while X-ray measurements are sensitive to all forms of hydrogen in both cloud and intercloud regions. It is suggested that roughly 50% of the hydrogen in the direction of the Crab Nebula is in clouds and that 85% of this hydrogen is neutral and atomic.

Ride, S. K.↗