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At least 1,423 records · Page 79
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NASA NTRS2007

Stardust in STARDUST - the C, N, and O Isotopic Compositions of Wild 2 Cometary Matter in Al Foil Impacts

In January 2006, the Stardust mission successfully returned dust samples from the tail of comet 81P/Wild 2 in two principal collection media, low density silica aerogel and Al foil. While hypervelocity impacts at the Stardust encounter velocity of 6.1 kilometers per second into Al foils are generally highly disruptive for natural, silicate-dominated impactors, previous studies have shown that many craters retain sufficient residue to allow a determination of the elemental and isotopic compositions of the original projectile. We have used two NanoSIMS ion microprobes to perform C, N, and O isotope imaging measurements on four large (59-295 micrometer diameter) and on 47 small (0.32-1.9 micrometer diameter) Al foil impact craters as part of the Stardust Preliminary Examination. Most analyzed residues in and around these craters are isotopically normal (solar) in their C, N, and O isotopic compositions. However, the debris in one large crater shows an average N-15 enrichment of approx. 450%o, which is similar to the bulk composition of some isotopically primitive interplanetary dust particles and to components of some primitive meteorites. A 250 nm grain in another large crater has an O-17 enrichment with approx. 2.65 times the solar O-17/O-16 ratio. Such an O isotopic composition is typical for circumstellar oxide or silicate grains from red giant or asymptotic giant branch stars. The discovery of this circumstellar grain clearly establishes that there is authentic stardust in the cometary samples returned by the Stardust mission. However, the low apparent abundance of circumstellar grains in Wild 2 samples and the preponderance of isotopically normal material indicates that the cometary matter is a diverse assemblage of presolar and solar system materials.

Stadermann, Frank J.↗
NASA NTRS1983

N-Butyl acrylate polymer composition for solar cell encapsulation and method

A polymer syrup for encapsulating solar cell assemblies. The syrup includes uncrosslinked poly(n-butyl)acrylate dissolved in n-butyl acrylate monomer. Preparation of the poly(n-butyl)acrylate and preparation of the polymer syrup is disclosed. Methods for applying the polymer syrup to solar cell assemblies as an encapsulating pottant are described. Also included is a method for solar cell construction utilizing the polymer syrup as a dual purpose adhesive and encapsulating material.

Gupta, Amitava↗
NASA NTRS2008

N-15-Rich Organic Globules in a Cluster IDP and the Bells CM2 Chondrite

Organic matter in primitive meteorites and chondritic porous interplanetary dust particles (CP IDPs) is commonly enriched in D/H and 15N/14N relative to terrestrial values [1-3]. These anomalies are ascribed to the partial preservation of presolar cold molecular cloud material [1]. Some meteorites and IDPs contain m-size inclusions with extreme H and N isotopic anomalies [2-4], possibly due to preserved pristine primordial organic grains. We recently showed that the in the Tagish Lake meteorite, the principle carriers of these anomalies are sub- m, hollow organic globules [5]. The globules likely formed by photochemical processing of organic ices in a cold molecular cloud or the outermost regions of the protosolar disk [5]. We proposed that similar materials should be common among primitive meteorites, IDPs, and comets. Similar objects have been observed in organic extracts of carbonaceous chondrites [6-8], however their N and H isotopic compositions are generally unknown. Bulk H and N isotopic compositions may indicate which meteorites best preserve interstellar organic compounds. Thus, we selected the Bells CM2 carbonaceous chondrites for study based on its large bulk 15N (+335 %) and D (+990 %) [9].

Messenger, S.↗
NASA NTRS2009

An Analytical Assessment of NASA's N+1 Subsonic Fixed Wing Project Noise Goal

The Subsonic Fixed Wing Project of NASA's Fundamental Aeronautics Program has adopted a noise reduction goal for new, subsonic, single-aisle, civil aircraft expected to replace current 737 and A320 airplanes. These so-called 'N+1' aircraft - designated in NASA vernacular as such since they will follow the current, in-service, 'N' airplanes - are hoped to achieve certification noise goal levels of 32 cumulative EPNdB under current Stage 4 noise regulations. A notional, N+1, single-aisle, twinjet transport with ultrahigh bypass ratio turbofan engines is analyzed in this study using NASA software and methods. Several advanced noise-reduction technologies are analytically applied to the propulsion system and airframe. Certification noise levels are predicted and compared with the NASA goal.

Berton, Jeffrey J.↗
NASA NTRS2010

An Analytical Assessment of NASA's N(+)1 Subsonic Fixed Wing Project Noise Goal

The Subsonic Fixed Wing Project of NASA s Fundamental Aeronautics Program has adopted a noise reduction goal for new, subsonic, single-aisle, civil aircraft expected to replace current 737 and A320 airplanes. These so-called "N+1" aircraft--designated in NASA vernacular as such since they will follow the current, in-service, "N" airplanes--are hoped to achieve certification noise goal levels of 32 cumulative EPNdB under current Stage 4 noise regulations. A notional, N+1, single-aisle, twinjet transport with ultrahigh bypass ratio turbofan engines is analyzed in this study using NASA software and methods. Several advanced noise-reduction technologies are empirically applied to the propulsion system and airframe. Certification noise levels are predicted and compared with the NASA goal.

Berton, Jeffrey J.↗
NASA NTRS2007

Representing Functions in n Dimensions to Arbitrary Accuracy

A method of approximating a scalar function of n independent variables (where n is a positive integer) to arbitrary accuracy has been developed. This method is expected to be attractive for use in engineering computations in which it is necessary to link global models with local ones or in which it is necessary to interpolate noiseless tabular data that have been computed from analytic functions or numerical models in n-dimensional spaces of design parameters.

Scotti, Stephen J.↗
NASA NTRS2010

Final Report for the Advanced Concept Studies for Supersonic Commercial Transports Entering Service in the 2030 to 2035 Period, N+3 Supersonic Program

The N+3 Final Report documents the work and progress made by Lockheed Martin Aeronautics in response to the NASA sponsored program "N+3 NRA Advanced Concept Studies for Supersonic Commercial Transports Entering Service in the 2030 to 2035 Period." The key technical objective of this effort was to generate promising supersonic concepts for the 2030 to 2035 timeframe and to develop plans for maturing the technologies required to make those concepts a reality. The N+3 program is aligned with NASA's Supersonic Project and is focused on providing alternative system-level solutions capable of overcoming the efficiency, environmental, and performance barriers to practical supersonic flight

Morgenstern, John↗
NASA NTRS2011

n-B-pi-p Superlattice Infrared Detector

A specially designed barrier (B) is inserted at the n-pi junction [where most GR (generation-recombination) processes take place] in the standard n-pi-p structure to substantially reduce generation-recombination dark currents. The resulting n-Bpi- p structure also has reduced tunneling dark currents, thereby solving some of the limitations to which current type II strained layer superlattice infrared detectors are prone. This innovation is compatible with common read-out integrated circuits (ROICs).

Ting, David Z.↗
NASA NTRS2006

Wholly Aromatic Ether-Imides as n-Type Semiconductors

Some wholly aromatic ether-imides consisting of rod-shaped, relatively-low-mass molecules that can form liquid crystals have been investigated for potential utility as electron-donor-type (ntype) organic semiconductors. It is envisioned that after further research to improve understanding of their physical and chemical properties, compounds of this type would be used to make thin film semiconductor devices (e.g., photovoltaic cells and field-effect transistors) on flexible electronic-circuit substrates. This investigation was inspired by several prior developments: Poly(ether-imides) [PEIs] are a class of engineering plastics that have been used extensively in the form of films in a variety of electronic applications, including insulating layers, circuit boards, and low-permittivity coatings. Wholly aromatic PEIs containing naphthalene and perylene moieties have been shown to be useful as electrochromic polymers. More recently, low-molecular-weight imides comprising naphthalene-based molecules with terminal fluorinated tails were shown to be useful as n-type organic semiconductors in such devices as field-effect transistors and Schottky diodes. Poly(etherimide)s as structural resins have been extensively investigated at NASA Langley Research Center for over 30 years. More recently, the need for multi-functional materials has become increasingly important. This n-type semiconductor illustrates the scope of current work towards new families of PEIs that not only can be used as structural resins for carbon-fiber reinforced composites, but also can function as sensors. Such a multi-functional material would permit so-called in-situ health monitoring of composite structures during service. The work presented here demonstrates that parts of the PEI backbone can be used as an n-type semiconductor with such materials being sensitive to damage, temperature, stress, and pressure. In the near future, multi-functional or "smart" composite structures are envisioned to be able to communicate such important parameters to the flight crew and provide vital information with respect to the operational status of their aircraft.

Weiser, Erik↗
NASA NTRS2012

A Propensity for n-omega-Amino Acids in Thermally-Altered Antarctic Meteorites

Carbonaceous meteorites are known to contain a wealth of indigenous organic molecules, including amino acids, which suggests that these meteorites could have been an important source of prebiotic organic material during the origins of life on Earth and possibly elsewhere. We report the detection of extraterrestrial amino acids in thermally-altered type 3 CV and CO carbonaceous chondrites and ureilites recovered from Antarctica. The amino acid concentrations of the thirteen Antarctic meteorites were generally less abundant than in more amino acid-rich CI, CM, and CR carbonaceous chondrites that experienced much lower temperature aqueous alteration on their parent bodies. In contrast to low-temperature aqueously-altered meteorites that show complete structural diversity in amino acids formed predominantly by Strecker-cyanohydrin synthesis, the thermally-altered meteorites studied here are dominated by small, straight-chain, amine terminal (n-omega-amino) amino acids that are not consistent with Strecker formation. The carbon isotopic ratios of two extraterrestrial n-omega-amino acids measured in one of the CV chondrites are consistent with C-13-depletions observed previously in hydrocarbons produced by Fischer-Tropsch type reactions. The predominance of n-omega-amino acid isomers in thermally-altered meteorites hints at cosmochemical mechanisms for the preferential formation and preservation of a small subset of the possible amino acids.

Burton, Aaron S.↗
NASA NTRS2013

Dual ohmic contact to N- and P-type silicon carbide

Simultaneous formation of electrical ohmic contacts to silicon carbide (SiC) semiconductor having donor and acceptor impurities (n- and p-type doping, respectively) is disclosed. The innovation provides for ohmic contacts formed on SiC layers having n- and p-doping at one process step during the fabrication of the semiconductor device. Further, the innovation provides a non-discriminatory, universal ohmic contact to both n- and p-type SiC, enhancing reliability of the specific contact resistivity when operated at temperatures in excess of 600.degree. C.

Okojie, Robert S.↗
NASA NTRS2014

Probing the Gaseous Disk of T Tau N with CN 5-4 Lines

We present spectrally resolved observations of the young multiple system T Tau in atomic and molecular lines obtained with the Heterodyne Instrument for the Far Infrared on board Herschel. While CO, H2O, [C ii], and SO lines trace the envelope and the outflowing gas up to velocities of 33 km s(exp −1) with respect to systemic, the CN 5-4 hyperfine structure lines at 566.7, 566.9 GHz show a narrow double-peaked profile centered at systemic velocity, consistent with an origin in the outer region of the compact disk of T Tau N. Disk modeling of the T Tau N disk with the thermo-chemical code ProDiMo produces CN line fluxes and profiles consistent with the observed ones and constrain the size of the gaseous disk (R(sub out) = 110(+10/−20) AU) and its inclination (i = 25 deg +/- 5 deg). The model indicates that the CN lines originate in a disk upper layer at 40-110 AU from the star, which is irradiated by the stellar UV field and heated up to temperatures of 50-700 K. With respect to previously observed CN 2-1 millimeter lines, the CN 5-4 lines appear to be less affected by envelope emission, due to their larger critical density and excitation temperature. Hence, high-J CN lines are a unique confusion-free tracer of embedded disks, such as the disk of T Tau N.

Far Infrared↗
NASA NTRS2005

Measurements of Breakdown Field and Forward Current Stability in 3C-SiC P-N Junction Diodes Grown on Step-Free 4H-SiC

This paper reports on initial fabrication and electrical characterization of 3C-SiC p-n junction diodes grown on step-free 4H-SiC mesas. Diodes with n-blocking-layer doping ranging from approx. 2 x 10(exp 16)/cu cm to approx.. 5 x 10(exp 17)/cu cm were fabricated and tested. No optimization of junction edge termination or ohmic contacts was employed. Room temperature reverse characteristics of the best devices show excellent low-leakage behavior, below previous 3C-SiC devices produced by other growth techniques, until the onset of a sharp breakdown knee. The resulting estimated breakdown field of 3C-SiC is at least twice the breakdown field of silicon, but is only around half the breakdown field of <0001> 4H-SiC for the doping range studied. Initial high current stressing of 3C diodes at 100 A/sq cm for more than 20 hours resulted in less than 50 mV change in approx. 3 V forward voltage. 3C-SiC, pn junction, p+n diode, rectifier, reverse breakdown, breakdown field,heteroepitaxy, epitaxial growth, electroluminescence, mesa, bipolar diode

Neudeck, Philip G.↗
NASA NTRS2016

Organic Analysis in the Miller Range 090657 CR2 Chondrite: Part 3 C and N Isotopic Imaging

Primitive carbonaceous chondrites contain a wide variety of organic material, ranging from soluble discrete molecules to insoluble nanoglobules of macro-molecular carbon. The relationship between the soluble organic molecules, macromolecular organic material, and host minerals are poorly understood. Large H, C and N isotopic anomalies suggest some organic components formed in low-T interstellar or outer Solar System environments. The highest isotope anomalies occur in m-scale inclusions in the most primitive materials, such as cometary dust and the least altered carbonaceous chondrites. Often, the hosts of these isotopically anomalous 'hotspots' are discrete organic nanoglobules that probably formed in the outermost reaches of the protosolar disk or cold molecular cloud. Molecular and isotopic studies of meteoritic organic matter are aimed at identifying the chemical properties and formation processes of interstellar organic materials and the subsequent chemical evolutionary pathways in various Solar System environments. The combination of soluble and insoluble analyses with in situ and bulk studies provides powerful constraints on the origin and evolution of organic matter in the Solar System. Using macroscale extraction and analysis techniques as well as microscale in situ observations we have been studying both insoluble and soluble organic material in primitive astromaterial samples. Here, we present results of bulk C and N isotopic measurements and coordinated in situ C and N isotopic imaging and mineralogical and textural studies of carbonaceous materials in a Cr2 carbonaceous chondrite. In accompanying abstracts we discuss the morphology and distribution of carbonaceous components and soluble organic species of this meteorite.

Messenger, S.↗
NASA NTRS2017

An N+3 Technology Level Reference Propulsion System

An N+3 technology level engine, suitable as a propulsion system for an advanced single-aisle transport, was developed as a reference cycle for use in technology assessment and decision-making efforts. This reference engine serves three main purposes: it provides thermodynamic quantities at each major engine station, it provides overall propulsion system performance data for vehicle designers to use in their analyses, and it can be used for comparison against other proposed N+3 technology-level propulsion systems on an equal basis. This reference cycle is meant to represent the expected capability of gas turbine engines in the N+3 timeframe given reasonable extrapolations of technology improvements and the ability to take full advantage of those improvements.

Jones, Scott M.↗
NASA NTRS2020

Formal Verification of a Solution to the n-Queens Problem

This report describes a formal verification of a concise algorithm that computes a solution to the n-Queens problem for all natural numbers n, such that n > 3. The formal proof of the algorithm is completed in the Prototype Verification System (PVS) theorem prover. This verification effort serves two purposes. First, it is presented as a pedagogical example for learning a theorem prover, such as PVS, and second, as a candidate benchmark for comparing other formal methods tools to PVS.

Mahyar R Malekpour↗
NASA NTRSDate not supplied

M:N Operations NASA/Uber Collaboration

In this presentation, current approaches to enable multiple-operator, multiple vehicle (M:N) operations are reviewed together with recent collaborative efforts between NASA and Uber. Topics include a review of human-automation teaming (HAT) concepts, including plays and working agreements, and a particular task-allocation method called Automation Level-based Task Allocation (ALTA). Following introductory material on HAT, an overview of a recent (July 2020) cognitive walkthrough study of M:N operations in the context of a food delivery via small-Unmanned Aircraft Systems application is provided. Initial results from this cognitive walkthrough detailing operator feedback on displays, operator and supervisor roles and responsibilities, and the overall concept of operation are reviewed. The presentation concludes with a description of a future, human-in-the-loop simulation experiment of M:N operations in a high-fidelity environment, which will examine the effects of high workload and assistive automation/tools on operator performance.

human-automation teaming↗
NASA NTRSDate not supplied

Calibration of Landsat 8 Aquatic Reflectance Band Data to Spatial Variations in Chlorophyll a, Suspended Sediment, N, and P in Coastal Estuaries of Southern Louisiana

Nutrient enrichment of coastal estuaries is a proven causal agent of harmful algal blooms, fish kills, and hypoxic zones. To enable regional mapping in coastal estuaries of southern Louisiana of Chlorophyll a, suspended sediment, N, and P concentrations, monthly water sample data collected at over 30 stations along a 129 km transect in the Barataria Basin by Turner et al. (2019) were correlated with Landsat 8 aquatic reflectance (ar) band 3 and 4 image data (2013-2016). Results showed significant non-linear correlations (R2 > 0.2) of Landsat ar band 4 values with measured concentrations of Chlorophyll a, total suspended sediment, N, and P. The strongest correlations were revealed between Landsat ar band 4 reflectances and total P concentrations, periodically at R2 values > 0.6. Landsat ar band images revealed detailed variations in total N and P concentrations that were consistent with the measured nutrient declines associated with dilution of freshwater as sampling locations progressed toward more coastal saline waters. Regional map images of ar band 4 in 2019 and 2020 confirmed that recent openings of Bonnet Carre Spillway could have resulted in damage to oyster beds in the brackish Gulf waters near Lake Borgne and the Mississippi River Delta, possibly due to reduced salinity levels and enhanced sediment deposition.

Calibration↗