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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

A study of redundancy management strategy for tetrad strap-down inertial systems

Algorithms were developed that attempt to identify which sensor in a tetrad configuration has experienced a step failure. An algorithm is also described that provides a measure of the confidence with which the correct identification was made. Experimental results are presented from real-time tests conducted on a three-axis motion facility utilizing an ortho-skew tetrad strapdown inertial sensor package. The effects of prediction errors and of quantization on correct failure identification are discussed as well as an algorithm for detecting second failures through prediction.

Hruby, R. J.↗
NASA NTRS1978

Large Area Crop Inventory Experiment (LACIE). Executive summary

The author has identified the following significant results. The Large Area Crop Inventory Experiment (LACIE), completed June 30, 1978, has met the USDA at-harvest goals (90% accuracy with a 90% confidence level) in the US Great Plains and U.S.S.R. for two consecutive years. In addition, in the U.S.S.R., LACIE indicated a shortfall in the '76-'77 wheat crop about two months prior to harvest, thus demonstrating the capability of LACIE to make accurate preharvest estimates.

Source record↗
NASA NTRS1979

Air breathing engine/rocket trajectory optimization

This research has focused on improving the mathematical models of the air-breathing propulsion systems, which can be mated with the rocket engine model and incorporated in trajectory optimization codes. Improved engine simulations provided accurate representation of the complex cycles proposed for advanced launch vehicles, thereby increasing the confidence in propellant use and payload calculations. The versatile QNEP (Quick Navy Engine Program) was modified to allow treatment of advanced turboaccelerator cycles using hydrogen or hydrocarbon fuels and operating in the vehicle flow field.

Smith, V. K., III↗
NASA NTRS1978

Nationwide forestry applications program. Ten-Ecosystem Study (TES) site 6, Fort Yukon, Alaska

The author has identified the following significant results. Analysis of the processing results has led to the following conclusions: (1) LANDSAT imagery was a reliable resource for the stratification of level 2 forest features (softwood, hardwood, tundra, and water). These features can be classified with an accuracy of 72.4 percent + or - 5.9 percent at the 90 percent confidence level. (2) Training fields selected for signature development from only 10 percent of the area did not adequately and efficiently cover the class variability for the entire area. (3) Derived regression transformations were ineffective in recovering the loss of level 1 forest proportions and level 2 softwood and hardwood proportions.

Ward, J. F.↗
NASA NTRS1979

Carbon Fiber Risk Analysis: Conclusions

It was concluded that preliminary estimates indicate that the public risk due to accidental release of carbon fiber from air transport aircraft is small. It was also concluded that further work is required to increase confidence in these estimates.

Huston, R. J.↗
NASA NTRS1978

Potential of laser for SPS power transmission

Research on the feasibility of using a laser subsystem as an additional option for the transmission of the satellite power system (STS) power is presented. Current laser work and predictions for future laser performance provide a level of confidence that the development of a laser power transmission system is technologically feasible in the time frame required to develop the SBS. There are significant economic advantages in lower ground distribution costs and a reduction of more than two orders of magnitude in real estate requirements for ground based receiving/conversion sites.

Bain, C. N.↗
NASA NTRS1979

The X-ray spectrum of 3C 273

An X-ray spectral measurement of the quasar 3C 273 with the HEAO-A2 experiment in June/July 1978 is reported. The best power law fit to the photon flux over the range 2-60 keV gives a slope of 1.41 + or - 0.02. However, structure is observed, indicating a slope of 1.52 between 2 keV and 9 keV and a slight flattening between 9 keV and 30 keV. Observations with the same experiment in December 1977 and OSO-8 in June 1976 allows confirmation of 40% intensity variability on the time scale of months, although within limits provided by the poorer statistical quality of the additional data no spectral change is discerned. Absorption from the source is found to be low, with the 1978 data yielding a 90% confidence upper limit to the hydrogen column density of 4.5 x 10 to the 21st power atoms/sq cm.

Worrall, D. M.↗
NASA NTRS1979

Nationwide forestry applications program. Ten-Ecosystem Study (TES) site 8, Grays Harbor County, Washington

The author has identified the following significant results. Level 2 forest features (softwood, hardwood, clear-cut, and water) can be classified with an overall accuracy of 71.6 percent plus or minus 6.7 percent at the 90 percent confidence level for the particular data and conditions existing at the time of the study. Signatures derived from training fields taken from only 10 percent of the site are not sufficient to adequately classify the site. The level 3 softwood age group classification appears reasonable, although no statistical evaluation was performed.

Prill, J. C.↗
NASA NTRS1979

Large Area Crop Inventory Experiment (LACIE). An overview of the Large Area Crop Inventory Experiment and the outlook for a satellite crop inventory

The author has identified the following significant results. The most important LACIE finding was that the technology worked very well in estimating wheat production in important geographic locations. Based on working through the many successes and shortcomings of LACIE, it can be stated with confidence that: (1) the current technology can successfully monitor what production in regions having similar characteristics to those of the U.S.S.R. wheat areas and the U.S. hard red winter wheat areas; (2) with additional applied research, significant improvements in capabilities to monitor wheat in these and other important production regions can be expected in the near future; (3) the remote sensing and weather effects modeling technology approached used by LACIE is generally applicable to other major crops and crop-producing regions of the world; and (4) with suitable effort, this technology can now advance rapidly and could be widespread use in the late 1980's.

Erb, R. B.↗
NASA NTRS1978

Statistical considerations in design of spacelab experiments

After making an analysis of experimental error sources, statistical models were developed for the design and analysis of potential Space Shuttle experiments. Guidelines for statistical significance and/or confidence limits of expected results were also included. The models were then tested out on the following proposed Space Shuttle biomedical experiments: (1) bone density by computer tomography; (2) basal metabolism; and (3) total body water. Analysis of those results and therefore of the models proved inconclusive due to the lack of previous research data and statistical values. However, the models were seen as possible guides to making some predictions and decisions.

Robinson, J.↗
NASA NTRS1979

A comparison of simulated and experimental wave spectra in the nearshore region

The results of comparing the experimental spectra measured over the shelf with spectra measured in deepwater conditions indicated that statistically significant changes occurred over the shelf region that could be attributed to shoaling and refraction effects. The comparison of the simulated spectra with the experimental agreed well at the 80% confidence level for all but the most inshore data segment. The total energy also showed similar agreement. However, the theoretical frequency at which peak spectral density occurred did not follow the decreasing trend seen in the experimental data. Guidelines are proposed for determining the type wavefield to which the modeling technique can best be applied, and caution is given on the selection of the digitization rate necessary to ensure sufficient detail for analysis of wave data.

Morris, W. D.↗
NASA NTRS1978

A search for far-ultraviolet emission from Sirius B

A rocket observation of Sirius in the far-UV region from 912 to 1240 A is reported. It is found that only a few counts were detected which can possibly be attributed to the hydrogen-rich white dwarf Sirius B. An upper limit of 2.0 by 10 to the -10th power erg/sq cm per sec/A on the Sirius B flux in the range from 1000 to 1080 A is established with 99.3% confidence. This upper limit is shown to constrain the model-dependent effective temperature of Sirius B to be less than or approximately 27,000 K. It is concluded that the observed X-ray flux from Sirius cannot be emitted by the photosphere of Sirius B.

Brune, W. H.↗
NASA NTRS1978

Contribution of intermediate luminosity X-ray galaxies to the background - Anon 0945-30

Evidence that the galaxy A0945-30 is a new extragalactic X-ray source was found from an analysis of rotating modulation collimator quick-look data collected from the SAS 3 X-ray observatory. A strong piece of evidence was the hydrogen column density of 3 plus or minus 1 times 10 to the 22nd power per sq cm for a power law spectrum extending to about 35 keV inferred from HEAO 1 data. Observations indicate that the galaxy is an early type spiral with a bright nucleus. A faint star alongside the galaxy within the 90% confidence X-ray source error circle is an F dwarf with no indication of emission features. Spectra of the galaxy in the red and blue show sharp, intermediate strength emission lines of forbidden O III, forbidden N II, and H-alpha together with strong Mg, Fe, Ca absorption features characteristic of a normal stellar continuum in the galactic nucleus.

Schnopper, H. W.↗
NASA NTRS1978

Performance characteristics of the electrochemical concentration cell ozonesonde

A large number of electrochemical concentration cell (ECC) ozonesondes were calibrated in relation to a UV photometric absorption ozone instrument prior to using the ozonesondes in atmospheric soundings. The two methods of measuring ozone were in reasonable agreement on the average, but there was considerable variation from one ozonesonde to another. Averaging the individual linear regressions gives an ECC ozone concentration equal to 0 + or - 8 nbar plus (0.96 + or - 0.10) times the concentration determined with the UV instrument, where uncertainties represent 90% confidence limits. Applying individual calibration corrections to atmospheric sounding data reduced the mean difference between Dobson spectrophotometric measurements of total ozone overburdens and corresponding values obtained from ozonesonde data from -8.5 + or - 8.2 to -1.4 + or - 7.3% for a series of measurements carried out in 1977. Corresponding uncorrected and corrected differences averaged 3.2 + or - 9.7 and 1.9 + or - 10.6%, respectively, for soundings carried out in 1976.

Torres, A. L.↗
NASA NTRS1978

Performance analysis of a filtered wide field-of-view radiometer for earth radiation budget measurements

The proposed Earth Radiation Budget Satellite System (ERBSS) of the 1980's will include a wide field-of-view (WFOV) fixed axes earth radiator discriminator consisting of a shortwave channel and a total (unfiltered) channel. The broadband spectral isolation required for the shortwave channel is achieved by use of a hemispherical fused silica (Suprasil W) dome filter placed in front of a wire wound thermopile radiation detector. A description is presented of the thermal response of the single-fused silica dome filter in the ERBSS WFOV shortwave channel conceptual design and the impact of that response on the channel measurement. Results from design definition and performance analysis studies are included. Problems associated with achieving the desired levels of confidence in a high accuracy filtered, WFOV radiometer are discussed. Design approaches, ground calibration, and data reduction techniques which minimize measurement uncertainties are explained.

Cooper, J. E.↗
NASA NTRS1979

X-rays from the Orion Trapezium

Observations of the Orion Nebula region and the associated X-ray source 4U 0531-05 with the SAS 3 rotation modulation collimators are presented which yield a precise position for a small component of the X-ray source and limit the source to the immediate region of the Trapezium. The reported weighted position has an error radius of 35 arcsec (90% confidence) and lies 9 arcsec from Theta-1 Ori. A 2-11-keV X-ray luminosity of approximately 0.7 x 10 to the 33rd erg/s is inferred for a distance of 460 pc, along with a component diameter of less than 0.3 pc. The existence of an extended component with a diameter of 0.8 to 1.6 pc and a flux density about twice that of the small component is also suggested. Possible sources of the X-ray emission are considered for both components. It is concluded that the two components may be ramifications of the stellar winds emanating from the Trapezium stars and that the small component may simply be a cusp in the larger distribution rather than an independent source.

Bradt, H. V.↗
NASA NTRS1979

Wave propagation in ducts using the finite element method

The paper outlines a comparative study designed to assess and compare the accuracy of the finite element method (FEM) for linear and quadratic elements as applied to problems in duct acoustics. The acoustic disturbances are assumed to be irrotational and isentropic so that the problem can be formulated in terms of the acoustic velocity potential. It is shown that for the case of plane wave propagation in a hard-walled annular cylinder, the accuracy of the FEM solution can be increased at higher frequencies by using quadratic triangular elements instead of linear triangular elements. Evidence is presented to enhance the confidence in applying the developed FEM by comparing results with those obtained by other independently developed numerical approaches such as an integral equation technique and a finite difference method.

Majjigi, R. K.↗
NASA NTRS1979

Simultaneous radio and X-ray observations of the X-ray burst source MXB 1636-53

On June 17, 1977, the X-ray burst source MXB 1636-53 was simultaneously monitored for about 4 hr with the Parkes 64-m radio telescope at a frequency of 14.7 GHz and the SAS 3 X-ray satellite (1.3-12 keV). One X-ray burst was observed; an upper limit (2 sigmas) of 200 mJy is reported for any radio burst coincident with the X-ray event. During the X-ray burst the radio/X-ray time-integrated flux ratio was no more than 375 with a 90 percent confidence. An upper limit (2 sigmas) of 22 mJy was determined for any steady 14.7-GHz source coincident with the X-ray position.

Thomas, R. M.↗