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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Space Station Freedom - Initial plans for U.S. utilization

NASA's utilization plans for the Space Station Freedom (SSF) are outlined with references to the Consolidated Operations and Utilization Plan (COUP) being developed to cover the first five years of the program. The SSF is described with particular attention given to the spacecraft capabilities, and initial long-term U.S. objectives are set forth with more immediate corresponding research areas. U.S. plans include research in microgravity, life sciences, and technology, and payload concepts are shown to be in development for each area. The SSF is expected to be a useful resource for: (1) commercial research on crystal growth; (2) investigations into physical and chemical processes in the microgravitational environment; and (3) technology studies relevant to the efficient exploitation of space. The NASA Partner Utilization Plan on which these observations are based is being prepared for incorporation into the SSF COUP.

Epstein, Barry↗
NASA NTRS1994

Microbial biofilm formation and its consequences for the CELSS program

A major goal of the Controlled Ecology Life Support System (CELSS) program is to provide reliable and efficient life support systems for long-duration space flights. A principal focus of the program is on the growth of higher plants in growth chambers. These crops should be grown without the risk of damage from microbial contamination. While it is unlikely that plant pathogens will pose a risk, there are serious hazards associated with microorganisms carried in the nutrient delivery systems and in the atmosphere of the growth chamber. Our experience in surface microbiology showed that colonization of surfaces with microorganisms is extremely rapid even when the inoculum is small. After initial colonization extensive biofilms accumulate on moist surfaces. These microbial films metabolize actively and slough off continuously to the air and water. During plant growth in the CELSS program, microbial biofilms have the potential to foul sensors and to plug nutrient delivery systems. In addition both metabolic products of microbial growth and degradation products of materials being considered for use as nutrient reservoirs and for delivery are likely sources of chemicals known to adversly affect plant growth.

Mitchell, R.↗
NASA NTRS2005

Numerical Modelling of the Deep Impact Mission Experiment

NASA s Deep Impact Mission (launched January 2005) will provide, for the first time ever, insights into the interior of a comet (Tempel 1) by shooting a approx.370 kg projectile onto the surface of a comets nucleus. Although it is usually assumed that comets consist of a very porous mixture of water ice and rock, little is known about the internal structure and in particular the constitutive material properties of a comet. It is therefore difficult to predict the dimensions of the excavated crater. Estimates of the crater size are based on laboratory experiments of impacts into various target compositions of different densities and porosities using appropriate scaling laws; they range between 10 s of meters up to ~250 m in diameter [1]. The size of the crater depends mainly on the physical process(es) that govern formation: Smaller sizes are expected if (1) strength, rather than gravity, limits crater growth; and, perhaps even more crucially, if (2) internal energy losses by pore-space collapse reduce the coupling efficiency (compaction craters). To investigate the effect of pore space collapse and strength of the target we conducted a suite of numerical experiments and implemented a novel approach for modeling porosity and the compaction of pores in hydrocode calculations.

Wuennemann, K.↗
NASA NTRS2005

High performance p-type thermoelectric materials and methods of preparation

The present invention is embodied in high performance p-type thermoelectric materials having enhanced thermoelectric properties and the methods of preparing such materials. In one aspect of the invention, p-type semiconductors of formula Zn4-xAxSb3-yBy wherein 0?x?4, A is a transition metal, B is a pnicogen, and 0?y?3 are formed for use in manufacturing thermoelectric devices with substantially enhanced operating characteristics and improved efficiency. Two methods of preparing p-type Zn4Sb3 and related alloys of the present invention include a crystal growth method and a powder metallurgy method.

Caillat, Thierry↗
NASA NTRS2012

Nonhazardous Urine Pretreatment Method

A method combines solid phase acidification with two non-toxic biocides to prevent ammonia volatilization and microbial proliferation. The safe, non-oxidizing biocide combination consists of a quaternary amine and a food preservative. This combination has exhibited excellent stabilization of both acidified and unacidified urine. During pretreatment tests, composite urine collected from donors was challenged with a microorganism known to proliferate in urine, and then was processed using the nonhazardous urine pre-treatment method. The challenge microorganisms included Escherichia coli, a common gram-negative bacteria; Enterococcus faecalis, a ureolytic gram-positive bacteria; Candida albicans, a yeast commonly found in urine; and Aspergillus niger, a problematic mold that resists urine pre-treatment. Urine processed in this manner remained microbially stable for over 57 days. Such effective urine stabilization was achieved using non-toxic, non-oxidizing biocides at higher pH (3.6 to 5.8) than previous methods in use or projected for use aboard the International Space Station (ISS). ISS urine pretreatment methods employ strong oxidants including ozone and hexavalent chromium (Cr(VI)), a carcinogenic material, under very acidic conditions (pH = 1.8 to 2.4). The method described here offers a much more benign chemical environment than previous pretreatment methods, and will lower equivalent system mass (ESM) by reducing containment volume and mass, system complexity, and crew time needed to handle pre-treatment chemicals. The biocides, being non-oxidizing, minimize the potential for chemical reactions with urine constituents to produce volatile, airborne contaminants such as cyanogen chloride. Additionally, the biocides are active under significantly less acidic conditions than those used in the current system, thereby reducing the degree of required acidification. A simple flow-through solid phase acidification (SPA) bed is employed to overcome the natural buffering capacity of urine, and to lower the pH to levels that fix ammoniacal nitrogen in the non-volatile and highly water soluble NH4 + form. Citric acid, a highly soluble, solid tricarboxylic acid essential to cellular metabolism, and typically used as a food preservative, has also been shown to efficiently acidify urine in conjunction with non-oxidizing biocides to provide effective stabilization with respect to both microbial growth and ammonia volatilization.

Akse, James R.↗
NASA NTRS2014

NASA Fixed Wing Project: Green Technologies for Future Aircraft Generation

The NASA Fundamental Aeronautics Fixed Wing (FW) Project addresses the comprehensive challenge of enabling revolutionary energy efficiency improvements in subsonic transport aircraft combined with dramatic reductions in harmful emissions and perceived noise to facilitate sustained growth of the air transportation system. Advances in multidisciplinary technologies and the development of unconventional aircraft systems offer the potential to achieve these improvements. The presentation will highlight the FW Project vision of revolutionary systems and technologies needed to achieve the challenging goals of aviation. Specifically, the primary focus of the FW Project is on the N+3 generation that is, vehicles that are three generations beyond the current state of the art, requiring mature technology solutions in the 2025-30 timeframe.

aircraft engines↗
NASA NTRS2015

Green Propulsion Technologies for Advanced Air Transports

Air transportation is critical to U.S. and Global economic vitality. However, energy and climate issues challenge aviation's ability to be sustainable in the long term. Aviation must dramatically reduce fuel use and related emissions. Energy costs to U.S. airlines nearly tripled between 1995 and 2011, and continue to be the highest percentage of operating costs. The NASA Advanced Air Transports Technology Project addresses the comprehensive challenge of enabling revolutionary energy efficiency improvements in subsonic transport aircraft combined with dramatic reductions in harmful emissions and perceived noise to facilitate sustained growth of the air transportation system. Advanced technologies and the development of unconventional aircraft systems offer the potential to achieve these improvements. The presentation will highlight the NASA vision of revolutionary systems and propulsion technologies needed to achieve these challenging goals. Specifically, the primary focus is on the N+3 generation; that is, vehicles that are three generations beyond the current state of the art, requiring mature technology solutions in the 2025-30 timeframe.

Del Rosario, Rubén↗
NASA NTRS2015

Green Propulsion Technologies for Advanced Air Transports

Air transportation is critical to U.S. and Global economic vitality. However, energy and climate issues challenge aviations ability to be sustainable in the long term. Aviation must dramatically reduce fuel use and related emissions. Energy costs to U.S. airlines nearly tripled between 1995 and 2011, and continue to be the highest percentage of operating costs. The NASA Advanced Air Transports Technology Project addresses the comprehensive challenge of enabling revolutionary energy efficiency improvements in subsonic transport aircraft combined with dramatic reductions in harmful emissions and perceived noise to facilitate sustained growth of the air transportation system. Advanced technologies and the development of unconventional aircraft systems offer the potential to achieve these improvements. The presentation will highlight the NASA vision of revolutionary systems and propulsion technologies needed to achieve these challenging goals. Specifically, the primary focus is on the N+3 generation; that is, vehicles that are three generations beyond the current state of the art, requiring mature technology solutions in the 2025-30 timeframe, which are envisioned as being powered by Hybrid Electric Propulsion Systems.

Hybrid Electric↗
NASA NTRS2015

An Enriched Shell Element for Delamination Simulation in Composite Laminates

A formulation is presented for an enriched shell finite element capable of delamination simulation in composite laminates. The element uses an adaptive splitting approach for damage characterization that allows for straightforward low-fidelity model creation and a numerically efficient solution. The Floating Node Method is used in conjunction with the Virtual Crack Closure Technique to predict delamination growth and represent it discretely at an arbitrary ply interface. The enriched element is verified for Mode I delamination simulation using numerical benchmark data. After determining important mesh configuration guidelines for the vicinity of the delamination front in the model, a good correlation was found between the enriched shell element model results and the benchmark data set.

McElroy, Mark↗
NASA NTRS2017

The Electrifying Future of Air Transportation

This presentation discusses the NASA Aeronautics Advanced Air Transport Technology Project’s perspective on electric, hybrid-electric, and related distributed propulsion technologies for future generations of large transport aircraft. Recent system studies commissioned by NASA and other organizations have identified these technologies as promising approaches to dramatically reduce aircraft fuel consumption, noise, and emissions. These technologies are part of the Project’s overall research portfolio aimed toward developing ultra-efficient commercial aircraft in conjunction with alternative low carbon propulsion and energy systems to enable safe and sustainable future growth in global aviation. It is anticipated that both room temperature and cryogenic electrical technologies will be needed in the future. Room temperature electrical systems are likely to impact aviation in the near term by making their way onto smaller aircraft and by augmenting traditional propulsion systems on larger aircraft, while cryogenic technologies will likely be needed in the far term to deliver the several tens of megawatts of propulsive power needed for large transport aircraft. The presentation outlines the opportunities and challenges for electric propulsion technologies for commercial aviation, and describes some of the related concepts and enabling technologies that are currently being developed.

Future↗
NASA NTRS2020

Understanding and Improving Model Representation of Aerosol Optical Properties for a Chinese Haze Event Measured During KORUS-AQ

KORUS-AQ was an international cooperative air quality field study in South Korea that measured local and remote sources of air pollution affecting the Korean Peninsula during May–June 2016. Some of the largest aerosol mass concentrations were measured during a Chinese haze transport event (24 May). Air quality forecasts using the WRF-Chem model with aerosol optical depth (AOD) data assimilation captured AOD during this pollution episode but overpredicted surface particulate matter concentrations in South Korea, especially PM2.5, often by a factor of 2 or larger. Analysis revealed multiple sources of model deficiency related to the calculation of optical properties from aerosol mass that explain these discrepancies. Using in situ observations of aerosol size and composition as inputs to the optical properties calculations showed that using a low-resolution size bin representation (four bins) underestimates the efficiency with which aerosols scatter and absorb light (mass extinction efficiency). Besides using finer-resolution size bins (8–16 bins), it was also necessary to increase the refractive indices and hygroscopicity of select aerosol species within the range of values reported in the literature to achieve better consistency with measured values of the mass extinction efficiency (6.7 m2 g−1 observed average) and light-scattering enhancement factor (f(RH)) due to aerosol hygroscopic growth (2.2 observed average). Furthermore, an evaluation of the optical properties obtained using modeled aerosol properties revealed the inability of sectional and modal aerosol representations in WRF-Chem to properly reproduce the observed size distribution, with the models displaying a much wider accumulation mode. Other model deficiencies included an underestimate of organic aerosol density (1.0 g cm−3 in the model vs. observed average of 1.5 g cm−3) and an overprediction of the fractional contribution of submicron inorganic aerosols other than sulfate, ammonium, nitrate, chloride, and sodium corresponding to mostly dust (17 %–28 % modeled vs. 12 % estimated from observations). These results illustrate the complexity of achieving an accurate model representation of optical properties and provide potential solutions that are relevant to multiple disciplines and applications such as air quality forecasts, health impact assessments, climate projections, solar power forecasts, and aerosol data assimilation.

Pablo E. Saide↗
NASA NTRSDate not supplied

Corridor Design and Analysis for UAM Operations

The Urban Air Mobility (UAM) concept is a part of Advanced Air Mobility (AAM), a joint initiative between the Federal Aviation Administration (FAA), NASA, and industry to develop an air transportation system that uses new electric (i.e., green) air vehicles in geographical areas previously underserved by traditional aviation. Market forecast studies predict that there will be demand for alternate modes of air transportation using electric Vertical Take-off and Landing aircraft. UAM expands transportation networks by introducing short flights to move people and goods around metropolitan areas​. UAM is expected to improve mobility for the public, decongest road traffic, reduce trip time, and decrease strain on existing public transportation networks. Various challenges exist to make the introduction of UAM operations successful in the U.S. National Airspace System (NAS). These include but are not limited to integration with existing airports and airspace, provision of air traffic services (e.g., separation), vehicle design and certification, and community acceptance. The focus of this paper is on integration of UAM operations into the NAS via introduction of new airspace structures. UAM will operate within a regulatory, operational, and technical environment that is incorporated into the NAS​. As per the UAM Concept of Operations (ConOps), the FAA retains regulatory authority and is responsible for establishing operational parameters and maintaining oversight. The FAA’s UAM ConOps describes flights at low altitudes (below 5,000 ft) with minimal disruption to established conventional aircraft traffic and limited voice interactions with the Air Traffic Control (ATC). Early stages of UAM may use existing procedures to safely integrate UAM with conventional flights. This would involve flying under Part 91 Visual Flight Rules (VFR) and using voice for communications. The initial UAM ecosystem will utilize the current infrastructure such as routes, helipads, and ATC services, where practicable. ​A NASA study explored the use of existing helicopter routes in Dallas Fort Worth (DFW) airspace for initial UAM operations with a Letter of Agreement (LOA) that included procedures to request a Class B (controlled airspace) clearance. The research showed that the chosen approach was feasible for near-term, low-demand UAM traffic, but was not scalable. The growth of operations in today’s aviation system has resulted in airspace reorganization and procedures to ensure safety and efficiency as traffic rates increase. One proposed operating innovation that can help with the scalability of UAM is establishing routes and corridors. This may look similar to the Area Navigation (RNAV) procedures used today to streamline operations into busy airports. However, instead of FAA automation systems and ATC managing the flow of traffic, some UAM concepts envision a third-party service provider performing this role as part of the Provider of Services for UAM (PSU) network. The FAA’s UAM ConOps posits that new airspace structures such as UAM corridors include the following design criteria: 1) Minimal impact on existing NAS operations, 2) no or minimal additional ATC services, 3) public interest considerations such as noise, safety, and security, and 4) customer needs. The airspace available in urban environments is limited by the height of buildings, the effect of weather including wind gusts, privacy needs, and a clearance envelope. The new airspace structure would need to be designed around large airports and urban areas where the initial market demand is likely to exist. NASA has started evaluating airspace in the Dallas Fort Worth area to design new airspace structures, keeping the first two design criteria in mind. It is assumed that there will be an on-board pilot-in-command, and the flights will operate under VFR in Visual Meteorological Conditions. Corridors will be required in controlled airspace, whereas UAM operations can fly in uncontrolled Class G and E airspace using current day rules. Keeler et. al identified factors and heuristics for development of routes for UAM operations for integration with airspace close to large airports such as Dallas Fort Worth and Dallas Love Field. This paper describes the heuristics applied to define the corridors, analyzes them with respect to legacy traffic and presents key results.

Urban Air Mobility↗
NASA NTRS1985

Defects in silicon effect on device performance and relationship to crystal growth conditions

A relationship between material defects in silicon and the performance of electronic devices will be described. A role which oxygen and carbon in silicon play during the defects generation process will be discussed. The electronic properties of silicon are a strong function of the oxygen state in the silicon. This state controls mechanical properties of silicon efficiency for internal gettering and formation of defects in the device's active area. In addition, to temperature, time, ambience, and the cooling/heating rates of high temperature treatments, the oxygen state is a function of the crystal growth process. The incorporation of carbon and oxygen into silicon crystal is controlled by geometry and rotation rates applied to crystal and crucible during crystal growths. Also, formation of nucleation centers for oxygen precipitation is influenced by the growth process, although there is still a controversy which parameters play a major role. All these factors will be reviewed with special emphasis on areas which are still ambiguous and controversial.

Jastrzebski, L.↗
NASA NTRS1994

Simulations of bypass transition for spatially evolving disturbances

The spatial evolution of disturbances in plane Poiseuille flow and zero pressure gradient boundary layer flow is considered. For disturbances governed by the linearized equations, potential for significant transient growth of the amplitude is demonstrated. The maximum amplification occurs for disturbances with zero or near zero frequencies. Spatial numerical simulations of the transition scenario involving a pair of oblique waves has been conducted for both flows. A fully spectral solver using a simple but efficient fringe region technique allowed the flows to be computed with high resolution into the fully turbulent domain. A modal decomposition of the simulation results indicates that non-linear excitation of the transient growth is responsible for the rapid emergence of low-frequency structures. Physically, this corresponds to streaky flow structures, as seen from the results of a numerical amplitude expansion. Thus, this spatial transition scenario has been found to be similar to the corresponding temporal one. In the boundary layer simulations the streaks are seen to break down from what appears to be a secondary instability.

Lundbladh, A.↗
NASA NTRS1990

AlGaAs top solar cell for mechanical attachment in a multi-junction tandem concentrator solar cell stack

Free-standing, transparent, tunable bandgap AlxGa1-xAs top solar cells have been fabricated for mechanical attachment in a four terminal tandem stack solar cell. Evaluation of the device results has demonstrated 1.80 eV top solar cells with efficiencies of 18 percent (100 X, and AM0) which would yield stack efficiencies of 31 percent (100 X, AM0) with a silicon bottom cell. When fully developed, the AlxGa1-xAs/Si mechanically-stacked two-junction solar cell concentrator system can provide efficiencies of 36 percent (AM0, 100 X). AlxGa1-xAs top solar cells with bandgaps from 1.66 eV to 2.08 eV have been fabricated. Liquid phase epitaxy (LPE) growth techniques have been used and LPE has been found to yield superior AlxGa1-xAs material when compared to molecular beam epitaxy and metal-organic chemical vapor deposition. It is projected that stack assembly technology will be readily applicable to any mechanically stacked multijunction (MSMJ) system. Development of a wide bandgap top solar cell is the only feasible method for obtaining stack efficiencies greater than 40 percent at AM0. System efficiencies of greater than 40 percent can be realized when the AlGaAs top solar cell is used in a three solar cell mechanical stack.

Dinetta, L. C.↗
NASA NTRS1973

Application of Earth Resources Technology Satellite data to urban development and regional planning: Test site, County of Los Angeles

The author has identified the following significant results. Signigicant results have been obtained from the analyses of ERTS-1 imagery from five cycles over Test Site SR 124 by classical photointerpretation and by an interactive hybrid multispectral information extraction system (GEMS). Photointerpretation has produced over 25 overlays at 1:1,000,000 scale depicting regional relations and urban structure in terms of several hundred linear and areal features. A possible new fault lineament has been discovered on the northern slope of the Santa Monica mountains. GEMS analysis of the ERTS-1 products has provided new or improved information in the following planning data categories: urban vegetation; land cover segregation; manmade and natural impact monitoring; urban design; land suitability. ERTS-1 data analysis has allowed planners to establish trends that directly impact planning policies. For example, detectable grading and new construction sites quantitatively indicated the extent, direction, and rate of urban expansion which enable planners to forecast demand and growth patterns on a regional scale. This new source of information will not only assist current methods to be more efficient, but permits entirely new planning methodologies to be employed.

Raje, S.↗
NASA NTRS1976

Electric load management and energy conservation

Electric load management and energy conservation relate heavily to the major problems facing power industry at present. The three basic modes of energy conservation are identified as demand reduction, increased efficiency and substitution for scarce fuels. Direct and indirect load management objectives are to reduce peak loads and have future growth in electricity requirements in such a manner to cause more of it to fall off the system's peak. In this paper, an overview of proposed and implemented load management options is presented. Research opportunities exist for the evaluation of socio-economic impacts of energy conservation and load management schemes specially on the electric power industry itself.

Kheir, N. A.↗
NASA NTRS1980

Low-cost solar array project task 1: Silicon material. Gaseous melt replenishment system

The operation of a silicon production technique was demonstrated. The essentials of the method comprise chemical vapor deposition of silicon, by hydrogen reduction of chlorosilanes, on the inside of a quartz reaction vessel having large internal surface area. The system was designed to allow successive deposition-melting cycles, with silicon removal being accomplished by discharging the molten silicon. The liquid product would be suitable for transfer to a crystal growth process, casting into solid form, or production of shots. A scaled-down prototype reactor demonstrated single pass conversion efficiency of 20 percent and deposition rates and energy consumption better than conventional Siemens reactors, via deposition rates of 365 microns/hr. and electrical consumption of 35 Kwhr/kg of silicon produced.

Jewett, D. N.↗