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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Analysis of the 0.511 MeV radiation at the OSO-7 satellite

Observations of the 0.511 MeV positron annihilation, gamma ray on the OSO-7 satellite are presented. Variables which affect the counting rate are discussed. An upper limit flux of .0076 photons/sq cm/sec is obtained for the quiet sun and a positive solar flux of .063(+ or - .0002) photons/sq cm/sec is obtained for the 3B flare of 4 August 1972. The width of this annihilation line gives an upper limit temperature for the annihilation region of approximately 6 million K. An analysis of the line width and position also shows that the contribution to the line from positronium annihilation is less than 100% at the 99% confidence level. An upper limit is also found for an isotropic cosmic flux.

Dunphy, P. P.↗
NASA NTRS1974

The definition and specification of the near earth environmental criteria for spacecraft thermal design

The variation of the earth's thermal and albedo radiation received by a near-earth orbiting space vehicle or space payload as a result of temporal variation of the earth atmosphere is discussed. A statistical study of current satellite data for determining probability distributions is proposed. With these distributions the thermal designer can define confidence levels on predicted temperature ranges which are compatible with engineering models for use in design, failure probabilities, and spacecraft cost estimates. Use of the distributions in environmental criteria guidelines is also considered.

Gary, G. A.↗
NASA NTRS1974

Agriculture, forestry, range resources

In the area of crop specie identification, it has been found that temporal data analysis, preliminary stratification, and unequal probability analysis were several of the factors that contributed to high identification accuracies. Single data set accuracies on fields of greater than 80,000 sq m (20 acres) are in the 70- to 90-percent range; however, with the use of temporal data, accuracies of 95 percent have been reported. Identification accuracy drops off significantly on areas of less than 80,000 sq m (20 acres) as does measurement accuracy. Forest stratification into coniferous and deciduous areas has been accomplished to a 90- to 95-percent accuracy level. Using multistage sampling techniques, the timber volume of a national forest district has been estimated to a confidence level and standard deviation acceptable to the Forest Service at a very favorable cost-benefit time ratio. Range specie/plant community vegetation mapping has been accomplished at various levels of success (69- to 90-percent accuracy). However, several investigators have obtained encouraging initial results in range biomass (forage production) estimation and range readiness predictions. Soil association map correction and soil association mapping in new area appear to have been proven feasible on large areas; however, testing in a complex soil area should be undertaken.

Crea, W. J.↗
NASA NTRS1973

Landing performance by low-time private pilots after the sudden loss of binocular vision - Cyclops II

Study of low-time general aviation pilots, who, in a series of spot landings, were suddenly deprived of binocular vision by patching either eye on the downwind leg of a standard, closed traffic pattern. Data collected during these landings were compared with control data from landings flown with normal vision during the same flight. The sequence of patching and the mix of control and monocular landings were randomized to minimize the effect of learning. No decrease in performance was observed during landings with vision restricted to one eye, in fact, performance improved. This observation is reported at a high level of confidence (p less than 0.001). These findings confirm the previous work of Lewis and Krier and have important implications with regard to aeromedical certification standards.

Lewis, C. E., Jr.↗
NASA NTRS1973

Service evaluation of aircraft composite structural components

The advantages of the use of composite materials in structural applications have been identified in numerous engineering studies. Technology development programs are underway to correct known deficiencies and to provide needed improvements. However, in the final analysis, flight service programs are necessary to develop broader acceptance of, and confidence in, any new class of materials such as composites. Such flight programs, initiated by NASA Langley Research Center, will be reviewed in the proposed paper. These programs, which include the selectively reinforced metal and the all-composite concepts applied to both secondary and primary aircraft structural components, will be described and current status will be indicated.

Brooks, W. A., Jr.↗
NASA NTRS1973

Composite materials in space structures

The use of composite materials in space vehicle structures offers significant advantages in reduction of structural weight fractions and in obtaining improved dynamic characteristics. Recent studies and developments include inertial booms for scientific satellites, structural components for future space shuttle applications, and pressurized tanks. Future applications could include major portions of vehicle primary structures as well as many secondary structural components. A number of problems still exist regarding achievement of the objectives, including development of sufficient environmental data, reliable design techniques, and general user confidence. These will be attacked in future R&D programs.

Mayer, N. J.↗
NASA NTRS1973

Estimation of proportions of objects and determination of training sample-size in a remote sensing application

A multichannel scanning device may fail to observe objects because of obstructions blocking the view, or different categories of objects may make up a resolution element giving rise to a single observation. Ground truth will be required on any such categories of objects in order to estimate their expected proportions associated with various classes represented in the remote sensing data. Considering the classes to be distributed as multivariate normal with different mean vectors and common covariance, maximum likelihood estimates are given for the expected proportions of objects associated with different classes, using the Bayes procedure for classification of individuals obtained from these classes. An approximate solution for simultaneous confidence intervals on these proportions is given, and thereby a sample-size needed to achieve a desired amount of accuracy for the estimates is determined.

Chhikara, R. S.↗
NASA NTRS1974

Statistical analysis of close pairs of QSOs

The observation of close pairs of QSOs with very different redshifts has been suggested by some as evidence in support of the noncosmological redshift hypothesis. A method is described for determining the statistical significance of such pairs. As an example, it is shown that the statistical significance of the pair 1548+115a,b is not well defined and ranges from approximately 99% confidence to about 60%. If statistical methods are to be used in such cases, they must not be argued a posteriori.

Burbidge, E. M.↗
NASA NTRS1974

Short-range interaction between hydrogen molecules

Recent calculations of the ground state energy of a system of four hydrogen atoms are reviewed with the aim of discerning the short-range repulsive part of the interaction potential between two hydrogen molecules. Extended-basis CI calculations which include a diffuse 2p orbital appear to be capable of determining the total interaction energy between to hydrogen molecules for any separation. Consistent results of such calculations suggest that the potential for intermolecular separations in the region from 1 to 2.5 A can now be specified to better than 10% with considerable confidence. Analytic fits to spherical averages of these results are presented.

Mcmahan, A. K.↗
NASA NTRS1974

OSO-7 observations of a high-latitude X-ray source associated with Abell cluster A2052

An X-ray source with a flux of 1.6 times 10 to the -10th power ergs per sec/sq cm (2-10 keV) has been observed at high galactic latitude by the MIT X-ray detectors on the OSO-7 satellite. Designated GX 8+50, its position is 15 hr 14.2 min right ascension, 6 deg 51 min declination, with a 90 percent confidence error circle of area 0.5 sq deg. The data are consistent with a power-law spectrum with an exponent 1.2 (plus or minus 0.2) or a thermal-bremsstrahlung spectrum with kT = 4 plus or minus 1 keV. A likely identification is the Abell cluster A2052, whose center coincides with the radio source 3C 317.

Heinz, C. J.↗
NASA NTRS1974

Are 2-micron absorptions and 11-micron emissions of M stars related

Three properties of M stars are compared: (1) /3.5/ - /11/ colors, (2) two measures of 2.3-micron band absorption, and (3) two measures of 1.9-micron band absorption. We find that the 2.3-micron bands of 21 M giants and supergiants correlate with /3.5/ - /11/ colors at better than 99 per cent confidence. A comparable relation exists between the mean 1.9-micron bands and /3.5/ - /11/ colors of 23 M giants and Miras. The sum of the 1.9-micron + 2.3-micron band intensities correlates with /3.5/ - /11/ color at better than the 99.8 per cent level for 31 M stars. These relations are consistent with both CO and H2O cooling of M star boundaries. Binaries and Ia supergiants appear to depart from these relations.

Fay, T. D., Jr.↗
NASA NTRS1974

Pulsar observations and neutron star models

Information about the physical parameters of neutron stars is obtained from pulsar observations. The energy balance of the Crab Nebula and the Vela X remnant allows one to derive limits for the masses of the Crab and Vela pulsars. Glitch observations provide further clues on the masses of these two pulsars. The degree of confidence with which one should believe the derived numbers is pointed out. The possibility of observing neutron stars in binary systems as pulsating X-ray sources is discussed. Finally, the importance of observing redshifted gamma ray lines from the surface of neutron stars, and thus directly measuring either individual or statistical properties of these objects, is pointed out.

Boerner, G.↗
NASA NTRS1974

Cost optimization of spacecraft test levels

Common to all nondestructive type testing of hardware that provides the necessary confidence in the design is the question regarding the proper magnitude of the test level. The objective of this investigation was to study the possibility of establishing cost optimized test levels of a rather general nature. This investigation was based on studying the influence of test level on a cost of error cost model that reflects the adverse effects of 'undertesting' and 'overtesting'. For the assumed conditions of normal distribution for the random variables and a protoflight spacecraft case, the results indicated that the limits for an optimum test factor can range between slightly less than 1.0 to slightly more than 1.5.

Young, J. P.↗
NASA NTRS1974

Theory of photoelectron production, transport and energy loss

Current understanding of the theory of ionospheric photoelectron production, transport and energy loss is summarized. The various approaches used in the theoretical calculations of photoelectron fluxes appear to be self consistent and sound; improved values for a number of input parameters are needed now in order to achieve significant improvements and more confidence in the results. The major remaining problem in the present day theory of photoelectron transport and energy loss is centered around the calculations of photoelectron transit through the protonosphere.

Nagy, A. F.↗
NASA NTRS1974

Mathematical estimation of the level of microbial contamination on spacecraft surfaces by volumetric air sampling

Microbiological sampling methods presently used for enumeration of microorganisms on spacecraft surfaces require contact with easily damaged components. Estimation of viable particles on surfaces using air sampling methods in conjunction with a mathematical model would be desirable. Parameters necessary for the mathematical model are the effect of angled surfaces on viable particle collection and the number of viable cells per viable particle. Deposition of viable particles on angled surfaces closely followed a cosine function, and the number of viable cells per viable particle was consistent with a Poisson distribution. Other parameters considered by the mathematical model included deposition rate and fractional removal per unit time. A close nonlinear correlation between volumetric air sampling and airborne fallout on surfaces was established with all fallout data points falling within the 95% confidence limits as determined by the mathematical model.

Oxborrow, G. S.↗
NASA NTRS1975

Design criteria monograph for metal tanks and tank components

Significant elements in detail tank design are wall and end structures, weld joints at bulkhead and attachment junctures, and ports and access openings. Additional design considerations are influence and effect of fabrication processes on tank component design, and finally, testing and inspection that are required to establish confidence in tank design.

Source record↗
NASA NTRS1975

Experimental and analytical sonic nozzle discharge coefficients for Reynolds numbers up to 8 x 10 to the 6th power

Sonic discharge coefficients are obtained for two different geometry flow nozzles using high-pressure nitrogen gas (100 atm) with significant real-gas flow corrections. Throat Reynolds number range extended up to 8 million. Discharge coefficients for both nozzles monotonically increase in value at the high throat Reynolds numbers. The 95-percent confidence band for each nozzle is shown. Analytical discharge coefficients for the continuous and finite radius of curvature nozzle are presented. These analytical results for the laminar and turbulent boundary-layer cases are compared to experimental values for sonic flow. Experimental values are also compared to values calculated from the best empirical curve fit equation for subsonic flow.

Szaniszlo, A. J.↗