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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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

The nature and evaluation of commercial expert system building tools

This memorandum reviews the factors that constitute an Expert System Building Tool (ESBT) and evaluates current tools in terms of these factors. Evaluation of these tools is based on their structure and their alternative forms of knowledge representation, inference mechanisms and developer/end-user interfaces. Next, functional capabilities, such as diagnosis and design, are related to alternative forms of mechanization. The characteristics and capabilities of existing commercial tools are then reviewed in terms of these criteria.

Gevarter, William B.↗
NASA NTRS1989

Vacuum resource provision for Space Station Freedom

The use of vacuum resources is integral to a number of proposed concepts for gas disposal from Space Staton Freedom. These include both direct overboard venting and onboard collection and storage of waste gases. A methodology is presented for determining flowrates through proposed vacuum lines. The flowrates through overboard vents are used to calculate number column densities, which are compared with current Freedom program requirements. The results are combined with discussions about the relative merits of some proposed and alternate concepts for providing vacuum resources.

Laskey, Kenneth J.↗
NASA NTRS1992

Development of task network models of human performance in microgravity

This paper discusses the utility of task-network modeling for quantifying human performance variability in microgravity. The data are gathered for: (1) improving current methodologies for assessing human performance and workload in the operational space environment; (2) developing tools for assessing alternative system designs; and (3) developing an integrated set of methodologies for the evaluation of performance degradation during extended duration spaceflight. The evaluation entailed an analysis of the Remote Manipulator System payload-grapple task performed on many shuttle missions. Task-network modeling can be used as a tool for assessing and enhancing human performance in man-machine systems, particularly for modeling long-duration manned spaceflight. Task-network modeling can be directed toward improving system efficiency by increasing the understanding of basic capabilities of the human component in the system and the factors that influence these capabilities.

Diaz, Manuel F.↗
NASA NTRS1993

Miniature Optical Wide-Angle-Lens Startracker (Mini-OWLS)

This paper provides a brief overview of the design considerations and the current status of the Miniature Optical Wide-Angle Lens Startracker Program. Mini-OWLS offers a revolutionary alternative to the conventional startracker. It is a small, lightweight, low cost, high performance startracker that can be used in a variety of applications including calibration and alignment of Inertial Measurement Units (IMU's) Mini-OWLS makes use of a strap down design incorporating Holographic Optical Elements (HOES) in place of conventional optics. HOES can be multiplexed so that the same aperture can be used for multiple separate optical paths looking in several directions simultaneously without startracker rotation. Additionally, separate Schmidt corrector plates are not required to compensate for spherical aberration. The optical assembly, or what would normally be considered as the telescope, is less than 20 cc in volume, weighs less than 55 grams, and contains the equivalent of three individual telescopes. Each one has a 4 deg Field of View (FOV) with a field of regard of 48 square degrees. Mini-OWLS has a bandwidth of approximately 300 nm in or near the visible wavelength. The projected resolution of the startracker is 5 to 10 arcseconds, depending on the centroiding algorithm used. The Mini-OWLS program was initiated last year and represents a miniaturized version of a similar design for aeronautical applications. The contract is managed by Wright Laboratory, Air Force Systems Command, Wright-Patterson AFB, Ohio, with funding from the Strategic Defense Initiative Organization through Eglin AFB. The initial phase of the program is to build and test a development unit. The second phase is to integrate the startracker with the Charles Stark Draper Laboratory Micromechanical Inertial Guidance System (MIGS) and the Signal Processing Packaging Design (SPPD) being developed by Texas Instruments. The preliminary design review was conducted in November 1991. Three-axes prototype telescope assemblies have been built and design evaluation tests initiated.

Miller, Rick↗
NASA NTRS2000

How do Polar Stratospheric Clouds Form?

SOLVE measurements have been compared with results from a microphysical model to understand the composition and formation of the polar stratospheric clouds (PSCs) observed during SOLVE. Evidence that the majority of the particles remain liquid throughout the winter will be presented. However, a small fraction of the particles do freeze, and the presence of these frozen particles can not be explained by current theories, in which the only freezing mechanism is homogeneous freezing to ice below the ice frost point. Alternative formation mechanisms, in particular homogeneous freezing above the ice frost point and heterogeneous freezing, have been explored using the microphysical model. Both nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD) have been considered as possible compositions for the solid-phase nitric acid aerosols. Comparisons between the model results and the SOLVE measurements will be used to constrain the possible formation mechanisms. Other effects of these frozen particles will also be discussed, in particular denitrification.

Drdla, Katja↗
NASA NTRS2005

MIT Participation in the Data Analysis of the XRS and XIS Instruments on the Astro-E2 Mission

Since the inception of this grant six weeks ago, we have completed the initial activation of the Suzaku X-ray Imaging Spectrometer (XIS) (on 13 August) and we have supported initial calibration observations. The instrument is performing very well in all respects. We have characterized the spectral resolution and effective area of each XIS sensor. We are especially excited about the scientific opportunities provided by the XIS'S back- illuminated sensor, which exhibits spectral resolution in the sub-keV band unmatched by any X-ray CCD currently in orbit. As specified in our proposal, we have established a web site (http://space.mit.edu/XIS) on which we maintain an up-to-date summary of instrument performance characteristics. Gain, spectral resolution and system noise, as well as residual background rates, are currently available on this site. Although the particle background level is low compared with Chandra and XMM, we are currently evaluating methods to reduce it still further. Techniques under study include use of 5x5 mode information and alternative grade selection methods. Although the primary responsibility for development of instrument response functions rests with our Japanese colleagues, we are incorporating our latest measurements of spectral resolution into some temporary response functions which we hope to make available to the Suzaku General Observer Facility and the Science Working Group(SWG). We are also preparing proposals for use of SWG observing time.

Bautz, Mark↗
NASA NTRS2005

Investigation of Ruthenium Dissolution in Advanced Membrane Electrode Assemblies for Direct Methanol Based Fuel Cell Stacks

Dissolution of ruthenium was observed in the 80-cell stack. Duration testing was performed in single cell MEAs to determine the pathway of cell degradation. EDAX analysis on each of the single cell MEAs has shown that the Johnson Matthey commercial catalyst is stable in DMFC operation for 250 hours, no ruthenium dissolution was observed. Changes in the hydrophobicity of the cathode backing papers was minimum. Electrode polarization analysis revealed that the MEA performance loss is attributed to changes in the cathode catalyst layer. Ruthenium migration does not seem to occur during cell operation but can occur when methanol is absent from the anode compartment, the cathode compartment has access to air, and the cells in the stack are electrically connected to a load (Shunt Currents). The open-to-air cathode stack design allowed for: a) The MEAs to have continual access to oxygen; and b) The stack to sustain shunt currents. Ruthenium dissolution in a DMFC stack can be prevented by: a) Developing an internally manifolded stacks that seal reactant compartments when not in operation; b) Bringing the cell voltages to zero quickly when not in operation; and c) Limiting the total number of cells to 25 in an effort to limit shunt currents.

alternative power sources↗
NASA NTRS2010

ISS Plasma Environment: Status of CCMC Products for ISS Mission Ops

ISS Program currently using FPMU Ne, Te in-situ measurements to support operations and anomaly investigations. Working to acquire alternative data sources if FPMU is not available. Work is progressing on CCMC tools for low Earth orbit ionosphere characterization. Validation against FPMU data required before model output can be used for ISS operational support. MSFC plans to continue comparing CTIP output during FPMU campaigns. Results to date have been useful in identifying ionospheric origins of high latitude charging environments.

Minow, Joseph↗
NASA NTRS2012

Preliminary Design of a Solar Photovoltaic Array for Net-Zero Energy Buildings at NASA Langley

An investigation was conducted to evaluate photovoltaic (solar electric systems) systems for a single building at NASA Langley as a representative case for alternative sustainable power generation. Building 1250 in the Science Directorate is comprised of office and laboratory space, and currently uses approximately 250,000 kW/month of electrical power with a projected use of 200,000 kW/month with additional conservation measures. The installation would be applied towards a goal for having Building 1250 classified as a net-zero energy building as it would produce as much energy as it uses over the course of a year. Based on the facility s electrical demand, a photovoltaic system and associated hardware were characterized to determine the optimal system, and understand the possible impacts from its deployment. The findings of this investigation reveal that the 1.9 MW photovoltaic electrical system provides favorable and robust results. The solar electric system should supply the needed sustainable power solution especially if operation and maintenance of the system will be considered a significant component of the system deployment.

Cole, Stuart K.↗
NASA NTRS2013

Treatment to Control Adhesion of Silicone-Based Elastomers

Seals are used to facilitate the joining of two items, usually temporarily. At some point in the future, it is expected that the items will need to be separated. This innovation enables control of the adhesive properties of silicone-based elastomers. The innovation may also be effective on elastomers other than the silicone-based ones. A technique has been discovered that decreases the level of adhesion of silicone- based elastomers to negligible levels. The new technique causes less damage to the material compared to alternative adhesion mitigation techniques. Silicone-based elastomers are the only class of rubber-like materials that currently meet NASA s needs for various seal applications. However, silicone-based elastomers have natural inherent adhesive properties. This stickiness can be helpful, but it can frequently cause problems as well, such as when trying to get items apart. In the past, seal adhesion was not always adequately addressed, and has caused in-flight failures where seals were actually pulled from their grooves, preventing subsequent spacecraft docking until the seal was physically removed from the flange via an extravehicular activity (EVA). The primary method used in the past to lower elastomer seal adhesion has been the application of some type of lubricant or grease to the surface of the seal. A newer method uses ultraviolet (UV) radiation a mixture of UV wavelengths in the range of near ultraviolet (NUV) and vacuum ultraviolet (VUV) wavelengths.

deGroh, Henry C., III↗
NASA NTRS2010

Simulating Future GPS Clock Scenarios with Two Composite Clock Algorithms

Using the GPS Toolkit, the GPS constellation is simulated using 31 satellites (SV) and a ground network of 17 monitor stations (MS). At every 15-minutes measurement epoch, the monitor stations measure the time signals of all satellites above a parameterized elevation angle. Once a day, the satellite clock estimates the station and satellite clocks. The first composite clock (B) is based on the Brown algorithm, and is now used by GPS. The second one (G) is based on the Greenhall algorithm. The composite clock of G and B performance are investigated using three ground-clock models. Model C simulates the current GPS configuration, in which all stations are equipped with cesium clocks, except for masers at USNO and Alternate Master Clock (AMC) sites. Model M is an improved situation in which every station is equipped with active hydrogen masers. Finally, Models F and O are future scenarios in which the USNO and AMC stations are equipped with fountain clocks instead of masers. Model F is a rubidium fountain, while Model O is more precise but futuristic Optical Fountain. Each model is evaluated using three performance metrics. The timing-related user range error having all satellites available is the first performance index (PI1). The second performance index (PI2) relates to the stability of the broadcast GPS system time itself. The third performance index (PI3) evaluates the stability of the time scales computed by the two composite clocks. A distinction is made between the "Signal-in-Space" accuracy and that available through a GNSS receiver.

global positioning system↗
NASA NTRS2015

Efficient Third-Order Distributed Feedback Laser with Enhanced Beam Pattern

A third-order distributed feedback laser has an active medium disposed on a substrate as a linear array of segments having a series of periodically spaced interstices therebetween and a first conductive layer disposed on a surface of the active medium on each of the segments and along a strip from each of the segments to a conductive electrical contact pad for application of current along a path including the active medium. Upon application of a current through the active medium, the active medium functions as an optical waveguide, and there is established an alternating electric field, at a THz frequency, both in the active medium and emerging from the interstices. Spacing of adjacent segments is approximately half of a wavelength of the THz frequency in free space or an odd integral multiple thereof, so that the linear array has a coherence length greater than the length of the linear array.

Hu, Qing↗
NASA NTRS1981

Shuttle solid rocket motor nozzle alternate ablative evaluation

A series of subscale tests are shown to suggest that a lower-cost ablative material than the rayon-based carbon ablative currently used in the Space Shuttle Solid Rocket Motor (SRM) may be used as a substitute. Six such ablatives with outstanding performance characteristics, using spun PAN and continuous pitch and PAN fibers instead of the present, continuous rayon, were identified in the course of tests with HTPB/AL/AP solid propellant grains with a burn time of 12 sec. The test nozzle features an initial throat diameter of 2.2 in. and a 6.1 expansion ratio. In addition to nozzle structural feature drawings, extensive test data tables and propellant formulation and properties tables are provided.

Powers, L. B.↗
NASA NTRS2012

Next Generation Life Support Project: Development of Advanced Technologies for Human Exploration Missions

Next Generation Life Support (NGLS) is one of several technology development projects sponsored by the National Aeronautics and Space Administration s Game Changing Development Program. NGLS is developing life support technologies (including water recovery, and space suit life support technologies) needed for humans to live and work productively in space. NGLS has three project tasks: Variable Oxygen Regulator (VOR), Rapid Cycle Amine (RCA) swing bed, and Alternative Water Processing. The selected technologies within each of these areas are focused on increasing affordability, reliability, and vehicle self sufficiency while decreasing mass and enabling long duration exploration. The RCA and VOR tasks are directed at key technology needs for the Portable Life Support System (PLSS) for an Exploration Extravehicular Mobility Unit (EMU), with focus on prototyping and integrated testing. The focus of the Rapid Cycle Amine (RCA) swing-bed ventilation task is to provide integrated carbon dioxide removal and humidity control that can be regenerated in real time during an EVA. The Variable Oxygen Regulator technology will significantly increase the number of pressure settings available to the space suit. Current spacesuit pressure regulators are limited to only two settings while the adjustability of the advanced regulator will be nearly continuous. The Alternative Water Processor efforts will result in the development of a system capable of recycling wastewater from sources expected in future exploration missions, including hygiene and laundry water, based on natural biological processes and membrane-based post treatment. The technologies will support a capability-driven architecture for extending human presence beyond low Earth orbit to potential destinations such as the Moon, near Earth asteroids and Mars.

Barta, Daniel J.↗
NASA NTRS1996

Extrinsic germanium photoconductors for far-IR astronomy: Research results and works in progress

Some Ge:Ga and Ge:Sb photoconductor materials and detectors that are currently under development are reported. The best Ge:Ga devices exhibit dark currents of lower than 200 electrons/s, with a concurrent responsivity of 2 A/W and a detective quantum efficiency (DQE) of 5 percent. For higher backgrounds, an operating temperature of 3 K can be used. This increases the DQE to 7 percent and the responsivity to 4.5 A/W. Investigations were initiated into n-type Ge:Sb as an alternative photoconductive material. Two crystals of Ge:Sb were grown and a number of test detectors were fabricated and evaluated. At 2 K, the best device produced dark currents of less than 100 electrons/s with concurrent responsivity of 1 A/W and DQE of 4 percent, and at 3 K, produced currents of 10(exp 5) electrons/s with a DQE of 7 percent and a responsivity of 4 A/W. Using p-type Ge:Ga crystals, two dimensional monolithic photoconductor arrays are being constructed. Future work will focus on measuring pixel-to-pixel homogeneity, cross talk issues, overall sensitivity and suitability for photometric instruments.

Beeman, J. W.↗
NASA NTRS1975

Formation of the lunar crust - An electrical source of heating

A model for formation of the lunar crust based on heating by electrical induction is explored, while adherence is maintained to certain constraints associated with existing models of the solar system. The heating mechanism is based on eddy current induction from disordered magnetic fields swept outwards by an intense (T Tauri-like) plasma flow from the sun. The electrical theory is an alternative to intense short-period accretion as a source of heat for the evolution of lunar maria and highlands, provided that long-lived radioactives are not swept to the surface from too large a melt volume during the initial thermal episode. This formation of the lunar highlands does not intrinsically require rapid accretion, nor on this basis is the time of formation of the planets generally restricted to a very short time. The threshold temperature for eddy current heating is attained by either a solar nebula at 300-400 C during formation of the moon or a very low energy long-period accumulation of the moon, both leading to melting in ten to the fifth to ten to the seventh power years.

Sonett, C. P.↗
NASA NTRS1974

Hydrogen detection study

The effectiveness was assessed of a hydrogen (H2) detection concept for regenerative environmental control life support systems (EC/LSS). The concept evaluated was that utilized for the electrochemical depolarized concentrator (EDC) design, constructed, and tested for the EC/LSS space station prototype program. The EDC contains combustible gas detectors (CGDs) which were evaluated with H2. The CGDs were evaluated for linearity, position sensitivity, reproducibility, ambient effects, repeatability, speed of response, recovery time, and interchangeability. The effectiveness of CGDs located within the EDC for sensing H2 leaks at various line replaceable units in the subsystem was determined. The effects of H2 leak rate, H2 concentration of leaking gas and air currents in the vicinity of the EDC were determined. Proposed improvements for the H2 detection concept were documented and alternative H2 detection approaches were identified and analyzed.

Shumar, J. W.↗
NASA NTRS1976

Satellites for distress alerting and locating: Report by Interagency Committee for Search and Rescue Ad Hoc Working Group

The background behind the congressional legislation that led to the requirement for the Emergency Locator Transmitter (ELT) and the Emergency Position-Indicating Radio Beacon (EPIRB) to be installed on certain types of aircraft and inspected marine vessels respectively is discussed. The DAL problem is discussed for existing ELT and EPIRB equipped aircraft and ships. It is recognized that the DAL requirement for CONUS and Alaska and the maritime regions are not identical. In order to address the serious DAL problem which currently exists in CONUS and Alaska, a low orbiting satellite system evolves as the most viable and cost effective alternative that satisfies the overall SAR system design requirements. A satellite system designed to meet the needs of the maritime regions could be either low orbiting or geostationary. The conclusions drawn from this report support the recommendation to proceed with the implementation of a SAR orbiting satellite system.

Ehrlich, E.↗