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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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Improving Building Construction Specifications in State and Local Governments

State and local governments can benefit from master specifications systems that centralize data on all types of building materials, products, and processes. Most of these systems are organized according to the MASTERFORMAT system, which, along with guide specifications that require the insertion or deletion of standardized information, resulted from the specific needs of users and providers. For jurisdictions preparing their own specifications, staff time and cost are reduced. For those subcontracting the preparation, master specifications provide a means of evaluating the specifications submitted. Current management specification systems described include SPECINTACT, OMSPEC, MASTERPEC, and the NAVFAC, Corps of Engineers, and GSA guide specifications.

Source record↗
NASA NTRS1983

The value of residential photovoltaic systems: A comprehensive assessment

Utility-interactive photovoltaic (PV) arrays on residential rooftops appear to be a potentially attractive, large-scale application of PV technology. Results of a comprehensive assessment of the value (i.e., break-even cost) of utility-grid connected residential photovoltaic power systems under a variety of technological and economic assumptions are presented. A wide range of allowable PV system costs are calculated for small (4.34 kW (p) sub ac) residential PV systems in various locales across the United States. Primary factor in this variation are differences in local weather conditions, utility-specific electric generation capacity, fuel types, and customer-load profiles that effect purchase and sell-back rates, and non-uniform state tax considerations. Additional results from this analysis are: locations having the highest insolation values are not necessary the most economically attractive sites; residential PV systems connected in parallel to the utility demonstrate high percentages of energy sold back to the grid, and owner financial and tax assumptions cause large variations in break-even costs. Significant cost reduction and aggressive resolution of potential institutional impediments (e.g., liability, standards, metering, and technical integration) are required for a residential PV marker to become a major electric-grid-connected energy-generation source.

Borden, C. S.↗
NASA NTRS1984

Error-trellis Syndrome Decoding Techniques for Convolutional Codes

An error-trellis syndrome decoding technique for convolutional codes is developed. This algorithm is then applied to the entire class of systematic convolutional codes and to the high-rate, Wyner-Ash convolutional codes. A special example of the one-error-correcting Wyner-Ash code, a rate 3/4 code, is treated. The error-trellis syndrome decoding method applied to this example shows in detail how much more efficient syndrome decoding is than Viterbi decoding if applied to the same problem. For standard Viterbi decoding, 64 states are required, whereas in the example only 7 states are needed. Also, within the 7 states required for decoding, many fewer transitions are needed between the states.

Reed, I. S.↗
NASA NTRS1985

Design of evaporator of spacelab refrigerator/freezer

An Evaporator has been designed for NASA-Johnson Space Center Life Sciences to conduct experiments in Spacelab mission SLS-1 using different samples such as blood, urine, human tissues etc. Two units will fly - one as a Refrigerator (4 C) and the other as a Freezer (-22 C). The evaporator tube is dip brazed on a grooved flat plate. Aluminum heat sink is dip brazed on the other side of the plate. Freon R5O2 is pumped through the tube and air is circulated over the finned surface to transfer heat. As freon 5O2 is considered toxic, the whole freon tube is covered with an evaporator cover to contain any freon leakage to avoid exposure to crew members. This containment is under vacuum and this pressure is monitored along with the freon pressure to determine freon leakage so that necessary steps can be taken to stop contamination of the spacelab air. An stress analysis has been done and it is found to have adequate safety margin to meet the requirements of NASA safety and reliability standards.

Hye, A.↗
NASA NTRS1985

Error-trellis syndrome decoding techniques for convolutional codes

An error-trellis syndrome decoding technique for convolutional codes is developed. This algorithm is then applied to the entire class of systematic convolutional codes and to the high-rate, Wyner-Ash convolutional codes. A special example of the one-error-correcting Wyner-Ash code, a rate 3/4 code, is treated. The error-trellis syndrome decoding method applied to this example shows in detail how much more efficient syndrome decordig is than Viterbi decoding if applied to the same problem. For standard Viterbi decoding, 64 states are required, whereas in the example only 7 states are needed. Also, within the 7 states required for decoding, many fewer transitions are needed between the states.

Reed, I. S.↗
NASA NTRS1985

The isotopic composition of helium in the cosmic radiation above 11 gigavolts

The He-3/He-4 abundance ratio above 11 GV has been measured with a balloon-borne experiment that employs the geomagnetic method of isotope separation near earth's equator. Above a kinetic energy of approximately 6 GeV per nucleon, the He-3/He-4 ratio is measured to be 0.24 + or - 0.05 under the assumption that the helium spectrum at earth is a power law in rigidity of the form R to the -2.65th. The implied interstellar mean escape pathlength of about 15 g per sq cm, with this assumption, is considerably greater than values determined from observations of heavier elements. Propagation models more complex than the standard simple leaky box would be required to simultaneously understand the propagation of both the lighter and heavier components of cosmic rays.

Jordan, S. P.↗
NASA NTRS1983

Time-of-flight anemometer for hot section applications

The design, construction and testing of laser anemometer configurations for Hot Section velocity measurements is considered. Optimizing the laser anemometer system necessarily included the data processing algorithms used. It is felt that the requirements here are too demanding for standard laser anemometer systems.

Edwards, R. V.↗
NASA NTRS1988

Evapotranspiration from nonuniform surfaces - A first approach for short-term numerical weather prediction

Observations of surface heterogeneity of soil moisture from scales of meters to hundreds of kilometers are discussed, and a relationship between grid element size and soil moisture variability is presented. An evapotranspiration model is presented which accounts for the variability of soil moisture, standing surface water, and vegetation internal and stomatal resistance to moisture flow from the soil. The mean values and standard deviations of these parameters are required as input to the model. Tests of this model against field observations are reported, and extensive sensitivity tests are presented which explore the importance of including subgrid-scale variability in an evapotranspiration model.

Wetzel, Peter J.↗
NASA NTRS1988

Multimission modular spacecraft (MMS)

This paper discusses the design requirements for the low-cost standard spacecraft development which has come to be known as the Multimission Modular Spacecraft (MMS). The paper presents the wide range of launch configurations of the MMS users, the population of programs using the MMS, and the cost effectiveness of the MMS concept. The paper addresses the in-orbit serviceability of the design as demonstrated by the successful SMM repair, and the recent selection of MMS for the Explorer Platform, which features in-orbit payload exchanges.

Falkenhayn, Edward, Jr.↗
NASA NTRS1987

Development of an analytical model to assess fuel property effects on combustor performance

A generalized first-order computer model has been developed in order to analytically evaluate the potential effect of alternative fuels' effects on gas turbine combustors. The model assesses the size, configuration, combustion reliability, and durability of the combustors required to meet performance and emission standards while operating on a broad range of fuels. Predictions predicated on combustor flow-field determinations by the model indicate that fuel chemistry, as defined by hydrogen content, exerts a significant influence on flame retardation, liner wall temperature, and smoke emission.

Sutton, R. D.↗
NASA NTRS1992

Bacteriorhodopsin Film For Processing SAR Signals

"Instant" photographic film based on semisynthetic retinal pigment bacteriorhodopsin proposed for optical processing of synthetic-aperture-radar (SAR) signals. Input image recorded on film by laser operating at writing wavelength of bacteriorhodopsin, and output image recorded on computer by standard frame-grabber. Because it requires no chemical development, enables processing in nearly real time. Fast response and high resolution well suited for application. Film reusable, with concomitant reduction in cost of SAR processing.

Yu, Jeffrey W.↗
NASA NTRS1991

A planning language for activity scheduling

Mission planning and scheduling of spacecraft operations are becoming more complex at NASA. Described here are a mission planning process; a robust, flexible planning language for spacecraft and payload operations; and a software scheduling system that generates schedules based on planning language inputs. The mission planning process often involves many people and organizations. Consequently, a planning language is needed to facilitate communication, to provide a standard interface, and to represent flexible requirements. The software scheduling system interprets the planning language and uses the resource, time duration, constraint, and alternative plan flexibilities to resolve scheduling conflicts.

Zoch, David R.↗
NASA NTRS1992

NIST torsion oscillator viscometer response: Performance on the LeRC active vibration isolation platform

Critical point viscosity measurements are limited to their reduced temperature approach to T(sub c) in an Earth bound system, because of density gradients imposed by gravity. Therefore, these classes of experiments have been proposed as good candidates for 'microgravity' science experiments where this limitation is not present. The nature of these viscosity measurements dictate hardware that is sensitive to low frequency excitations. Because of the vibratory acceleration sensitivity of a torsion oscillator viscometer, used to acquire such measurements, a vibration isolation sensitivity test was performed on candidate 'microgravity' hardware to study the possibility of meeting the stringent oscillatory sensitivity requirements of a National Institute of Standards and Technology (NIST) torsion oscillator viscometer. A prototype six degree of freedom active magnetic isolation system, developed at NASA Lewis Research Center, was used as the isolation system. The ambient acceleration levels of the platform were reduced to the noise floor levels of its control sensors, about one microgravity in the 0.1 to 10 Hz bandwidth.

Berg, Robert F.↗
NASA NTRS1991

Recent technology products from Space Human Factors research

The goals of the NASA Space Human Factors program and the research carried out concerning human factors are discussed with emphasis given to the development of human performance models, data, and tools. The major products from this program are described, which include the Laser Anthropometric Mapping System; a model of the human body for evaluating the kinematics and dynamics of human motion and strength in microgravity environment; an operational experience data base for verifying and validating the data repository of manned space flights; the Operational Experience Database Taxonomy; and a human-computer interaction laboratory whose products are the display softaware and requirements and the guideline documents and standards for applications on human-computer interaction. Special attention is given to the 'Convoltron', a prototype version of a signal processor for synthesizing the head-related transfer functions.

Jenkins, James P.↗
NASA NTRS1992

Simulation of automatic rotorcraft nap-of-the-earth flight in graphics workstation environment

This paper describes a three-dimensional (3D) helicopter flight simulation system. The simulation is designed to be a readily available tool for concept verification and tuning of automatic obstacle-avoidance guidance algorithms. The system has been implemented on networked workstations capable of interactive 3D graphics simulation. The simulation uses realistic terrain and obstacle models. The dynamics of the rotorcraft and the functional capabilities of the range sensors are simulated to provide all the components required to evaluate the guidance function. Standard graphics hardware available on the workstation is utilized to accelerate the range-data calculations for sensor simulation at the guidance rate. An example is given to demonstrate the performance of the obstacle-avoidance capability.

Lam, T.↗
NASA NTRS1993

Spurious changes in the ISCCP dataset

The International Satellite Cloud Climatology Project (ISCCP) data set for July 1983-December 1990 exhibits a long term decrease in mean cloud optical depth and mean cloudtop temperature which is large compared to the mean for this period. It is here suggested that this decrease is an artifact of incomplete normalization of the visible channel on successive polar orbiters employed as the ISCCP's calibration standard; more accurate calibration techniques are required for the establishment of long-term climate trends.

Klein, Stephen A.↗
NASA NTRS1993

ROSAT observations of pulsed soft X-ray emission from PSR 1055-52

Utilizing the position-sensitive proportional counter and the high-resolution imager aboard the orbiting X-ray observatory ROSAT, we have detected pulsations at the radio period from the pulsar PSR 1055-52. The pulse shapes are energy-dependent and show a transition at about 0.5 keV where the phase angle of the pulse peak changes by about -120 deg and the pulsed fraction increases from 11 percent to 63 percent toward larger energies. Simple spectral models are found to be unsatisfactory, while multicomponent models, such as a soft blackbody and hard power-law tail, yield better fits to the pulse-height data. The hard power-law tail is consistent with the extension of the recently reported EGRET results and may indicate a common emission mechanism for the X-ray through GeV gamma-ray regime. The soft blackbody component with T(infinity) = (7.5 +/- 0.6) x 10 exp 5 K, if interpreted as the initial cooling of a neutron star, is consistent with standard cooling models and does not require the presence of exotic components.

Oegelman, Hakki↗
NASA NTRS1922

Comparative performance with direct and geared engines

Comprehensive tests were made to compare the performance of the F-5-L Boat Seaplane fitted with direct drive and Liberty engines. Details are given on the test conditions. The conclusions of the comparison tests follow. 1) An F-5-L with geared engines takes off in approximately 90 percent of the time required for the same airplane with standard direct drive engines. An F-5-L with geared engines climbs in 20 minutes to an altitude approximately 20 percent greater than that obtained with the standard direct drive on the same airplane. 3) There is a large difference between the climbs of the two airplanes of the same type. This difference will always be more pronounced when the climb is normally slow. In the case of the F-5-L airplanes under construction, it is of the order of a 10 percent difference in altitude on a 20 minute climb. 4) The maximum speed of an F-5-L with geared engines is about 3.5 percent greater than the maximum speed of the same airplane with standard direct drive engines (at the same engine r.p.m.). 5) The fuel consumption is probably less effected by the type of drive than by inherent differences in the performance of different airplanes.

Diehl, W S↗