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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Historical trend in the research and development of aircraft

Results are presented from a study of aircraft design trends undertaken to determine the relationship between research, development, test and evaluation and aircraft mission capability, requirements and objectives. It is shown that while in some cases a performance objective was the primary research driver, research was the driver in the formulation of objectives in others. Among the topics discussed are: (1) speed considerations such as compressibility, propulsion and test techniques; (2) airframe considerations such as swept, delta, trapezoidal and variable-sweep planforms and mission commonality; (3) research aircraft; (4) the recent impact of computer-aided design; (5) Soviet aircraft development approaches and (6) a comparison of Soviet and U.S. military aircraft design trends. Attention is given to experimental and prototype aircraft programs which, although cancelled, anticipated significant subsequent developments.

Spearman, M. L.↗
NASA NTRS1981

Ozone Trend Detectability

The detection of anthropogenic disturbances in the Earth's ozone layer was studied. Two topics were addressed: (1) the level at which a trend in total ozoning is detected by existing data sources; and (2) empirical evidence in the prediction of the depletion in total ozone. Error sources are identified. The predictability of climatological series, whether empirical models can be trusted, and how errors in the Dobson total ozone data impact trend detectability, are discussed.

Campbell, J. W.↗
NASA NTRS1981

Total ozone trend significance from space time variability of daily Dobson data

Estimates of standard errors of total ozone time and area means, as derived from ozone's natural temporal and spatial variability and autocorrelation in middle latitudes determined from daily Dobson data are presented. Assessing the significance of apparent total ozone trends is equivalent to assessing the standard error of the means. Standard errors of time averages depend on the temporal variability and correlation of the averaged parameter. Trend detectability is discussed, both for the present network and for satellite measurements.

Wilcox, R. W.↗
NASA NTRS1981

Trends in high temperature gas turbine materials

High performance - high technology materials are among the technologies that are required to allow the fruition of such improvements. Materials trends in hot section components are reviewed, and materials for future use are identified. For combustors, airfoils, and disks, a common trend of using multiple material construction to permit advances in technology is identified.

Grisaffe, S. J.↗
NASA NTRS1982

Recent trends in aviation turbine fuel properties

Plots and tables, compiled from Department of Energy (and predecessor agency) inspection reports from 1969 to 1980, present ranges, averages, extremes, and trends for most of the 22 properties of Jet A aviation turbine fuel. In recent years, average values of aromatics content, mercaptan sulfur content, distillation temperature of 10 percent recovered, smoke point, and freezing point show small but recognizable trends toward their specification limits. About 80 percent of the fuel samples had at least one property near specification, defined as within a standard band about the specification limit. By far the most common near-specification properties were aromatics content, smoke point, and freezing point.

Friedman, R.↗
NASA NTRS1983

Some historical trends in the research and development of aircraft

A survey of some trends in aircraft design was made in an effort to determine the relation between research, development, test, and evaluation (RDT and E) and aircraft mission capability, requirements, and objectives. Driving forces in the history of aircraft include the quest for speed which involved design concepts incorporating jet propulsion systems and low drag features. The study of high speed design concepts promoted new experimental and analytical research techniques. These research techniques, in turn, have lead to concepts offering new performance potential. Design trends were directed toward increased speed, efficiency, productivity, and safety. Generally speaking, the research and development effort has been evolutionary in nature and, with the exception of the transition to supersonic flight, little has occurred since the origin of flight that has drastically changed the basic design fundamentals of aircraft. However, this does not preclude the possibility of dramatic changes in the future since the products of research are frequently unpredictable. Advances should be expected and sought in improved aerodynamics (reduced drag, enhanced lift, flow field exploitation); propulsion (improved engine cycles, multimode engines, alternate fuels, alternate power sources); structures (new materials, manufacturing techniques); all with a view toward increased efficiency and utility.

Spearman, M. L.↗
NASA NTRS1983

Advances and trends in structural and solid mechanics; Proceedings of the Symposium, Washington, DC, October 4-7, 1982

The mechanics of materials and material characterization are considered, taking into account micromechanics, the behavior of steel structures at elevated temperatures, and an anisotropic plasticity model for inelastic multiaxial cyclic deformation. Other topics explored are related to advances and trends in finite element technology, classical analytical techniques and their computer implementation, interactive computing and computational strategies for nonlinear problems, advances and trends in numerical analysis, database management systems and CAD/CAM, space structures and vehicle crashworthiness, beams, plates and fibrous composite structures, design-oriented analysis, artificial intelligence and optimization, contact problems, random waves, and lifetime prediction. Earthquake-resistant structures and other advanced structural applications are also discussed, giving attention to cumulative damage in steel structures subjected to earthquake ground motions, and a mixed domain analysis of nuclear containment structures using impulse functions.

Noor, A. K.↗
NASA NTRS1983

Spacecraft-borne long life cryogenic refrigeration: Status and trends

The status of cryogenic refrigerator development intended for, or possibly applicable to, long life spacecraft-borne application is reviewed. Based on these efforts, the general development trends are identified. Using currently projected technology needs, the various trends are compared and evaluated. The linear drive, non-contacting bearing Stirling cycle refrigerator concept appears to be the best current approach that will meet the technology projection requirements for spacecraft-borne cryogenic refrigerators. However, a multiply redundant set of lightweight, moderate life, moderate reliability Stirling cycle cryogenic refrigerators using high-speed linear drive and sliding contact bearings may possibly suffice.

Johnson, A. L.↗
NASA NTRS1985

Some fighter aircraft trends

Some basic trends in fighters are traced from the post World II era. Beginning with the first operational jet fighter, the P-80, the characteristics of subsequent fighter aircraft are examined for performance, mission capability, effectiveness, and cost. Characteristics presented include: power loading, wing loading, maximum speed, rate of climb, turn rate, weight and weight distribution, cost and cost distribution. The characteristics of some USSR aircraft are included for comparison. The trends indicate some of the rationale for certain fighter designs and some likely characteristics to be sought in future fighter aircraft designs.

Spearman, L.↗
NASA NTRS1985

Measurement Requirements for the Detection of Ozone Trends

The number of measurements and period of collection in order to detect a trend in the vertical distribution of ozone was studied. Specific issues considered include the impact of: (1) short term ozone variability over the measurement site, and (2) the precision of the measuring instrument on the ability to detect trends to a given confidence limit.

Frederick, J. E.↗
NASA NTRS1985

Trends in the Southern Hemisphere

The station data of monthly mean sea level pressure, surface air temperature as well as monthly mean upper air rawinsonde observations were used to study the trends in the southern winter (June, July and August) and summer (December, January and February). This study covers the period 1951 to 1981. Most of the surface data have continuous 31 year records, however, for some high latitude stations, both surface and upper air records started in 1957 or even later. The normalized anomaly for a given variable Z is defined as the departure from the 1951 to 1981 grand mean divided by the standard deviation during the same period. To eliminate the large fluctuations in the data, the 1-3-1 smoothing was applied to the time series of normalized anomalies. The trends of monthly mean temperatures and height from the surface to 200 mb level is documented.

Mo, K. C.↗
NASA NTRS1985

Trends in measurement of solar vector magnetic fields using the Zeeman effect

Trends in spectropolarimetry as applied to the problem of Zeeman effect measurement are discussed. The use of detector arrays to improve observing efficiency is obtained. Which required new polarization modulation schemes that match the time required to read detector arrays. Another significant trend is narrowband filters, to improve angular and temporal coverage, and to Fourier transform spectrometers, to improve spectral coverage and precision. Low-polarization designs and improved methods for compensating instrumental polarization were developed. A requirement for high angular resolution suggests using adaptive optical devices to subdue the effects of bad seeing. The ultimate strategy to beat the seeing is to loft the telescope above the atmosphere such as is planned with a 30-cm telescope in 1985 and a 1250-cm telescope in 1990.

Harvey, J. W.↗
NASA NTRS1984

Some fighter aircraft trends

Some basic trends in fighter aircraft are traced from the post World War II era. Beginning with the first operational jet fighter, the P-80, the characteristics of subsequent fighter aircraft are examined in terms of performance, mission capability, effectiveness, and cost. Characteristics presented include such items as power loading, wing loading, maximum speed, rate of climb, turn rate, weight and weight distribution, cost and cost distribution. In some cases, the characteristics of U.S.S.R. aircraft are included for comparison. The trends indicate some of the rationale for certain fighter designs and indicate some likely characteristics to be sought in future fighter aircraft designs.

Spearman, M. L.↗
NASA NTRS1985

Analysis of segregation trends observed in iron meteorites using measured distribution coefficients

Fe-Ni alloys of meteoritic composition were solidified by a plane front solidification technique. Distribution coefficients of Ni, P, Ir, Ge, and Cu were determined from the composition data of the plane front solidified alloys. Equations that describe the distribution coefficients (P, Ni, Ir, Ge, and Cu) as a function of S and P content as well as S to P ratio were used to calculate solute partitioning between solid and liquid during the solidification of IIAB, IIIAB, and IVA parent bodies. The calculated P versus Ni, Ir versus Ni, Ge versus Ni, and Cu versus Ni trends are in good agreement with the observed meteorite data for each chemical group. It is concluded that each chemical group formed as a single molten pool in a parent body and that solute partitioning that occurred during solidification is responsible for the observed compositional trends within a single meteorite group.

Sellamuthu, R.↗
NASA NTRS1986

An assessment of the status and trends in satellite communications 1986-2000: An information document prepared for the Communications Subcommittee of the Space Applications Advisory Committee

This is a response to a Space Applications Advisory Committee (SAAC) request for information about the status and trends in satellite communications, to be used to support efforts to conceive and recommend long range goals for NASA communications activities. Included in this document are assessments of: (1) the outlook for satellite communications, including current applications, potential future applications, and impact of the changing environment such as optical fiber networks, the Integrated Services Digital Network (ISDN) standard, and the rapidly growing market for Very Small Aperture Terminals (VSAT); (2) the restrictions imposed by our limited spectrum resource; and (3) technology needs indicated by future trends. Potential future systems discussed include: large powerful satellites for providing personal communications; VSAT compatible satellites with onboard switching and having voice capability; large satellites which offer a pervasive T1 network service (primarily for video-phone); and large geostationary communications facilities which support common use by several carriers. Also, discussion is included of NASA particular needs and possible future systems. Based on the mentioned system concepts, specific technology recommendations are provided for the time frames of now - 1993, 1994 - 2000, and 2000 - 2010.

Poley, W. A.↗
NASA NTRS1986

October Antarctic temperature and total ozone trends from 1979-1985

The morphology of temperature trends in the south polar stratosphere from 1979-1985 is detailed. A significant cooling has occurred in the stratosphere over this period. South polar October mean temperatures have declined 18 K at 24 km over the seven-year period. A large fraction of this decline occurs as a result of including 1979 temperatures in the trend. The years 1979 and 1982 differ from other years in that they include large mid-October wave events which produce significantly warmer polar temperatures. Nevertheless, a significant temperature decline has still occurred in the stratosphere even when the dynamically active years are not included. Comparing two relatively dynamically quiet years, 1980 and 1985, the largest temperature decrease in the 30 mb temperature field occurs not at the pole but in the subpolar temperature maximum centered near 60 deg S. The changes in temperature of both the maximum and the polar low regions correlate fairly well with total ozone changes observed by the Total Ozone Mapping Spectrophotometer.

Newman, Paul A.↗
NASA NTRS1988

Trends In Satellite Communication

Report assesses trends in satellite communication from present to year 2010. Examines restrictions imposed by limited spectrum resource and technology needs created by trends. Personal communications, orbiting switchboards, and videophones foreseen.

Poley, William A.↗
NASA NTRS1988

Trends in atmospheric ozone - Conflicts between models and SBUV data

Results obtained from simple models for the long-term change in ozone and its seasonal amplitude as a function of atmospheric pressure in the region from 3.0-0.1 mbar are compared with ozone measurements obtained with the Solar Backscatter Ultraviolet Instrument (SBUV). The SBUV data show secular trends in ozone which are negative and larger than the largest model trends by a factor of two or more. It is suggested that temperature-correlated variations in photochemistry should be included in the model.

Rusch, D. W.↗