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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Characterization of the Sol-Gel Transition for Zirconia-Toughened Alumina Precursors

High purity ZTA ceramic powders with and without yttria were produced using metal alkoxide precursors. ZTA ceramic powders with varying volume percents of zirconia were prepared (7, 15, and 22%). Aluminum tri-sec butoxide, zirconium propoxide, and yttrium isopropoxide were the reagents used. Synthesis conditions were varied to control the hydrolysis and the aging conditions for the sol to gel transition. FTIR analysis and theological characterization were used to follow the structural evolution during the sol to gel transition. The greater extent of hydrolysis and the build-up of structure measured from viscoelastic properties were consistent. Heat treatment was conducted to produce submicron grain fully crystalline ZTA ceramic powders. In all experimental cases a-alumina and tetragonal zirconia phases were confirmed even in the absence of yttria.

Moeti, I.↗
NASA NTRS2000

Robotic Precursor Missions for Mars Habitats

Infrastructure support for robotic colonies, manned Mars habitat, and/or robotic exploration of planetary surfaces will need to rely on the field deployment of multiple robust robots. This support includes such tasks as the deployment and servicing of power systems and ISRU generators, construction of beaconed roadways, and the site preparation and deployment of manned habitat modules. The current level of autonomy of planetary rovers such as Sojourner will need to be greatly enhanced for these types of operations. In addition, single robotic platforms will not be capable of complicated construction scenarios. Precursor robotic missions to Mars that involve teams of multiple cooperating robots to accomplish some of these tasks is a cost effective solution to the possible long timeline necessary for the deployment of a manned habitat. Ongoing work at JPL under the Mars Outpost Program in the area of robot colonies is investigating many of the technology developments necessary for such an ambitious undertaking. Some of the issues that are being addressed include behavior-based control systems for multiple cooperating robots (CAMPOUT), development of autonomous robotic systems for the rescue/repair of trapped or disabled robots, and the design and development of robotic platforms for construction tasks such as material transport and surface clearing.

Huntsberger, Terry↗
NASA NTRS2002

Single Source Precursors for Thin Film Solar Cells

The development of thin film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power, (W/kg). The use of a polycrystalline chalcopyrite absorber layer for thin film solar cells is considered as the next generation photovoltaic devices. At NASA GRC we have focused on the development of new single source precursors (SSP) and their utility to deposit the chalcopyrite semi-conducting layer (CIS) onto flexible substrates for solar cell fabrication. The syntheses and thermal modulation of SSPs via molecular engineering is described. Thin-film fabrication studies demonstrate the SSPs can be used in a spray CVD (chemical vapor deposition) process, for depositing CIS at reduced temperatures, which display good electrical properties, suitable for PV (photovoltaic) devices.

Banger, Kulbinder K.↗
NASA NTRS2002

Environment Conscious, Biomorphic Ceramics from Pine and Jelutong Wood Precursors

Environment conscious, biomorphic ceramics have been fabricated from pine and jelutong wood precursors. A carbonaceous preform is produced through wood pyrolysis and subsequent infiltration with oxides (ZrO2 sols) and liquid silicon to form ceramics. These biomorphic ceramics show a wide variety of microstructures, densities, and hardness behavior that are determined by the type of wood and infiltrants selected.

Singh, Mrityunjay↗
NASA NTRS2002

Ternary Precursors for Depositing I-III-VI2 Thin Films for Solar Cells via Spray CVD

The development of thin-film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power (W/kg). Thin-film fabrication studies demonstrate that ternary single source precursors (SSP's) can be used in either a hot or cold-wall spray chemical vapour deposition (CVD) reactor, for depositing CuInS2, CuGaS2, and CuGaInS2 at reduced temperatures (400 to 450 C), which display good electrical and optical properties suitable for photovoltaic (PV) devices. X-ray diffraction studies, energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) confirmed the formation of the single phase CIS, CGS, CIGS thin-films on various substrates at reduced temperatures.

Banger, K. K.↗
NASA NTRS2003

Reactive Processing of Environmentally Conscious, Biomorphic Ceramics from Natural Wood Precursors

Environmentally conscious, biomorphic ceramics (Ecoceramics) are a new class of materials that are manufactured from renewable resources and wastes. In this study, silicon carbide and oxide-based biomorphic ceramics have been fabricated from pine and jelutong wood precursors. A carbonaceous preform is produced through wood pyrolysis and subsequent infiltration with oxides (ZrO2 sols) and liquid silicon to form ceramics. These biomorphic ceramics show a wide variety of microstructures, densities, and hardness behavior that are determined by the type of wood and infiltrants selected.

Singh, M.↗
NASA NTRS2003

Characterization of the Effects of Precursor Mineralogy on Hematite Spectra: Application to Martian Hematite Mineralization

The Thermal Emission Spectrometer (TES) instrument aboard Mars Global Surveyor discovered several isolated deposits of gray, crystalline hematite in Sinus Meridiani, Aram Chaos, and Valles Marineris. A variety of formation mechanisms has been proposed for the martian hematite deposits, including aqueous and nonaqueous processes. Comparison of the average Sinus Meridiani hematite spectrum measured by TES to laboratory emissivity spectra for a variety of naturally occurring hematites shows small but potentially important differences. In particular, the emissivity minimum at 300 and 445/cm in the Sinus Meridiani (SM) spectrum is displaced 10-25/cm to lower frequencies compared to some natural hematite samples. In addition, these bands in the TES data are narrower than the broad bands seen in many natural hematite spectra. These differences may imply that the natural variability of hematite spectra has not been fully characterized, especially with respect to the reaction pathway (precursor mineralogy and temperature of hematite formation) and crystal morphology. Here, we describe the thermal infrared spectral characteristics of several series of synthetic hematite samples derived by direct precipitation, dehydroxylation of fine-grained goethite and the oxidation of magnetite. Several natural hematite sample spectra are also presented for comparison. Transmission electron microscopy (TEM) and Mossbauer spectral analyses of selected samples were performed in order to help determine the causes of the changes seen in the infrared spectra.

Glotch, Timothy D.↗
NASA NTRS2003

Nanocrystalline Chalcopyrite Materials (CuInS2 and CuInSe2) via Low-Temperature Pyrolysis of Molecular Single-Source Precursors

Nanometer sized particles of the chalcopyrite compounds CuInS2 and CuInSe2 were synthesized by thermal decomposition of molecular single-source precursors (PPh3)2CuIn(SEt)4 and (PPh3)2CuIn(SePh)4, respectively, in the non-coordinating solvent dioctyl phthalate at temperatures between 200 and 300 C. The nanoparticles range in size from 3 - 30 nm and are aggregated to form roughly spherical clusters of about 500 nm in diameter. X-ray diffraction of the nanoparticle powders shows greatly broadened lines indicative of very small particle sizes, which is confirmed by TEM. Peaks present in the XRD can be indexed to reference patterns for the respective chalcopyrite compounds. Optical spectroscopy and elemental analysis by energy dispersive spectroscopy support the identification of the nanoparticles as chalcopyrites.

Castro, Stephanie L.↗
NASA NTRS2004

A New Commercializable Route for the Preparation of Single-Source Precursors for Bulk, Thin-Film, and Nanocrystallite I-III-IV Semiconductors

We report a new simplified synthetic procedure for commercial manufacture of ternary single source precursors (SSP). This new synthetic process has been successfully implemented to fabricate known SSPs on bulk scale and the first liquid SSPs to the semiconductors CuInSe2 and AgIn(x)S(y). Single crystal X-ray determination reveals the first unsolvated ternary AgInS SSP. SSPs prepared via this new route have successfully been used in a spray assisted chemical vapor deposition (CVD) process to deposit polycrystalline thin films, and for preparing ternary nanocrystallites.

Banger, Kulbinder K.↗
NASA NTRS2003

Senseless acts as a binary switch during sensory organ precursor selection

During sensory organ precursor (SOP) specification, a single cell is selected from a proneural cluster of cells. Here, we present evidence that Senseless (Sens), a zinc-finger transcription factor, plays an important role in this process. We show that Sens is directly activated by proneural proteins in the presumptive SOPs and a few cells surrounding the SOP in most tissues. In the cells that express low levels of Sens, it acts in a DNA-binding-dependent manner to repress transcription of proneural genes. In the presumptive SOPs that express high levels of Sens, it acts as a transcriptional activator and synergizes with proneural proteins. We therefore propose that Sens acts as a binary switch that is fundamental to SOP selection.

NASA Program Fundamental Space Biology↗
NASA NTRS1997

Composite Properties of Polyimide Resins Made From "Salt-Like" Solution Precursors

Recent work in high temperature materials at NASA Langley Research Center (LaRC (trademark)) have led to the development of new polyimide resin systems with very attractive properties. The majority of the work done with these resin systems has concentrated on determining engineering mechanical properties of composites prepared from a poly(amide acid) precursor. Three NASA Langley-developed polyimide matrix resins, LaRC (trademark) -IA, LaRC (trademark) -IAX, and LaRC (trademark) -8515, were produced via a salt-like process developed by Unitika Ltd. The 'salt-like' solutions (sixty-five percent solids in NMP) were prepregged onto Hexcel IM7 carbon fiber using the NASA LaRC Multipurpose Tape Machine. Process parameters were determined and composite panels fabricated. Mechanical properties are presented for these three intermediate modulus carbon fiber/polyimide matrix composites and compared to existing data on the same polyimide resin systems and IM7 carbon fiber manufactured via poly(amide acid) solutions (thirty-five percent solids in NMP). This work studies the effects of varying the synthetic route on the processing and mechanical properties of polyimide composites.

Cano, Roberto J.↗
NASA NTRS1997

Chaotic Time Series Analysis Method Developed for Stall Precursor Identification in High-Speed Compressors

A new technique for rotating stall precursor identification in high-speed compressors has been developed at the NASA Lewis Research Center. This pseudo correlation integral method uses a mathematical algorithm based on chaos theory to identify nonlinear dynamic changes in the compressor. Through a study of four various configurations of a high-speed compressor stage, a multistage compressor rig, and an axi-centrifugal engine test, this algorithm, using only a single pressure sensor, has consistently predicted the onset of rotating stall.

Source record↗
NASA NTRS2004

Precursor Science for the Terrestrial Planet Finder

This document outlines a path for the development of the field of extrasolar planet research, with a particular emphasis on the goals of the Terrestrial Planet Finder (TPF). Over the past decade, a new field of research has developed, the study of extrasolar planetary systems, driven by the discovery of massive planets around nearby stars. The planet count now stands at over 130. Are there Earth-like planets around nearby stars? Might any of those planets be conducive to the formation and maintenance of life? These arc the questions that TPF seeks to answer. TPF will be implemented as a suite of two space observatories, a 6-m class optical coronagraph, to be launched around 20 14, and a formation flying mid-infrared interferometer, to be launched sometime prior to 2020. These facilities will survey up to 165 or more nearby stars and detect planets like Earth should they be present in the 'habitable zone' around each star. With observations over a broad wavelength range, TPF will provide a robust determination of the atmospheric composition of planets to assess habitability and the presence of life. At this early stage of TPF's development, precursor observational and theoretical programs are essential to help define the mission, to aid our understanding of the planets that TPF could discover, and to characterize the stars that TPF will eventually study. This document is necessarily broad in scope because the significance of individual discoveries is greatly enhanced when viewed in thc context of the field as a whole. This document has the ambitious goal of taking us from our limited knowledge today, in 2004, to the era of TPF observations in the middle of the next decade. We must use the intervening years wisely. This document will be reviewed annually and updated as needed. The most recent edition is available online at http://tpf.jpl.nasa.gov/ or by email request to lawson@hucy.jpl.nasa.gov

Lawson, P. R.↗
NASA NTRS2005

Cu(In,Ga)S2, Thin-Film Solar Cells Prepared by H2S Sulfurization of CuGa-In Precursor

Thin-film CuInS2 solar cell is the leading candidate for space power because of bandgap near the optimum value for AM0 solar radiation outside the earth's atmosphere, excellent radiation hardness, and freedom from intrinsic degradation mechanisms unlike a-Si:H cells. Ultra-lightweight thin-film solar cells deposited on flexible polyimide plastic substrates such as Kapton(trademark), Upilex(trademark), and Apical(trademark) have a potential for achieving specific power of 1000 W/kg, while the state-of-art specific power of the present day solar cells is 66 W/kg. This paper describes the preparation of Cu-rich CuIn(sub 1-x)Ga(sub x)S(sub 2) (CIGS2) thin films and solar cells by a process of sulfurization of CuGa-In precursor similar to that being used for preparation of large-compact-grain CuIn(sub 1-x)Ga(sub x)Se2 thin films and efficient solar cells at FSEC PV Materials Lab.

Dhere, Neelkanth G.↗
NASA NTRS1997

Remote Sensing of Tropospheric Ozone and Its Precursors

Global and regional mapping of tropospheric ozone and its precursors using the Tropospheric Emission Spectrometer and its forerunner - the Airborne Emission Spectrometer - will be discussed.

ozone troposphere spectrometry Tropospheric Emissi↗
NASA NTRS1995

Collision of Comet Shoemaker-Levy 9 with Jupiter: Impact Study of Two Fragments from Timing of Precursor Events

The impacts of fragments K and R of comet Shoemaker-Levy 9 are examined with the aim to interpret the timing of the observed precursors to the main thermal emission event and to correlate the results of ground-based infrared observations with a variety of observations made onboard the Galileo spacecraft. Independent observations of the impact phenomena (of K & R) are combined.

comet Shoemaker-Levy 9 Jupiter impact Jovian atmos↗
NASA NTRS2007

Lunar Precursor Robotic Program: A Robotic Focus To The Vision

In April 2006, NASA, with help from the commercial and international communities, began developing a global Lunar Exploration Strategy. These activities resulted in themes that expanded on why we should return to the Moon and objectives that identify what we should do when we get there. NASA used these results to develop a Lunar Architecture designed to achieve the subset of the global Lunar Exploration Strategy objectives that fit within NASA's scope. A component of this architecture is the Lunar Precursor Robotic Program. This Program, anticipated to consist of both lunar orbiters and landers, is intended to meet many of NASA's lunar exploration objectives.

French, Raymond A.↗