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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

LEADER - An integrated engine behavior and design analyses based real-time fault diagnostic expert system for Space Shuttle Main Engine (SSME)

The LEADER expert system has been developed for automatic learning tasks encompassing real-time detection, identification, verification, and correction of anomalous propulsion system operations, using a set of sensors to monitor engine component performance to ascertain anomalies in engine dynamics and behavior. Two diagnostic approaches are embodied in LEADER's architecture: (1) learning and identifying engine behavior patterns to generate novel hypotheses about possible abnormalities, and (2) the direction of engine sensor data processing to perform resoning based on engine design and functional knowledge, as well as the principles of the relevant mechanics and physics.

Gupta, U. K.↗
NASA NTRS1990

Diagnostic evaluations of microwave generated helium and nitrogen plasma mixtures

The goal of this work is to continue the development to fundamentally understand the plasma processes as applied to spacecraft propulsion. The diagnostic experiments used are calorimetric, dimensional, and spectroscopic measurements using the TM 011 and TM 012 modes in the resonance cavity. These experimental techniques are highly important in furthering the understanding of plasma phenomena and of designing rocket thrusters. Several experimental results are included using nitrogen and helium gas mixtures.

Haraburda, Scott S.↗
NASA NTRS1990

Optical property measurements as a diagnostic tool for control of materials processing in space and on Earth

A new method is described, including results, to measure, control, and follow containerless processing in ground based levitators. This technique enables instantaneous optical property measurements from a transient solid or liquid surface concurrent with true temperature measurement. This was used successfully as a diagnostic tool to follow processing of Al, Si, and Ti during electromagnetic levitation. Experiments on Al show the disappearance of the oxide (emittance 0.33) at ca. 1300 C leaving a liquid surface with an emittance of 0.06. Electromagnetic levitation of silicon shows a liquid with a constant emittance (0.2) but with a solid whose emittance decreases very rapidly with increasing temperature. Consequently, the processing of materials at high temperatures can be controlled quite well through the control of surface optical properties.

Krishnan, Shankar↗
NASA NTRS1990

Photovoltaic array space power plus diagnostics experiment

The objective is to summarize the five years of hardware development and fabrication represented by the Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) Instrument. The original PASP Experiment requirements and background is presented along with the modifications which were requested to transform the PASP Experiment into the PASP Plus Instrument. The PASP Plus hardware and software is described. Test results for components and subsystems are given as well as final system tests. Also included are appendices which describe the major subsystems and present supporting documentation such as block diagrams, schematics, circuit board artwork, drawings, test procedures and test reports.

Burger, D. R.↗
NASA NTRS1991

Interpretation of plasma diagnostics package results in terms of large space structure plasma interactions

The Plasma Diagnostics Package (PDP) is a spacecraft which was designed and built at The University of Iowa and which contained several scientific instruments. These instruments were used for measuring Space Shuttle Orbiter environmental parameters and plasma parameters. The PDP flew on two Space Shuttle flights. The first flight of the PDP was on Space Shuttle Mission STS-3 and was a part of the NASA/Office of Space Science payload (OSS-1). The second flight of the PDP was on Space Shuttle Mission STS/51F and was a part of Spacelab 2. The interpretation of both the OSS-1 and Spacelab 2 PDP results in terms of large space structure plasma interactions is emphasized.

Kurth, William S.↗
NASA NTRS1991

Optical diagnostic investigation of low Reynolds number nozzle flows

The objectives are to obtain temperature, density and velocity profile measurements in the expansion region of low Reynolds number nozzles through the use of optical diagnostics. An LIF system will be used to probe the expansion of a microwave-heated expansion in the Center vacuum facility. The experimental measurements made in this program will be compared to numerical predictions obtained by Drs. Charles Merkle and Lyle Long.

Micci, Michael M.↗
NASA NTRS1990

A new age diagnostic applied to the globular clusters NGC 288 and NGC 362

A new age diagnostic for globular clusters is described which uses the difference between the turnoff and the base of the giant branch as the age indicator. As a first application, it is shown that there is a difference in age of 3.1 + or - 0.9 Gyr between the classic 'second parameter' pair NGC 288 and NGC 362. The existence of this age difference is independent of metal abundance differences between the two clusters of up to 0.5 dex. This age difference is corrected for various combinations of relative oxygen enhancement, and it is concluded that the difference in age remains significant for all plausible scenarios.

Sarajedini, Ata↗
NASA NTRS1991

Laser diagnostics on a hypersonic combustor

NASA-Langley has implemented a laser-based multipoint/multiparameter diagnostics system at its hypersonic direct-connect combustor, in order to measure both temperature and majority species densities in two dimensions, using spatially-scanned CARS; in addition, line-imaged measurements of radical densities are simultaneously generated by LIF at any of several planes downstream of the fuel injector. Initial experimental trials have demonstrated successful detection of one-dimensional images of OH density, as well as CARS N2-temperature measurements, in the turbulent reaction zone of the hypersonic combustor.

Taylor, David J.↗
NASA NTRS1990

Signal processing of spectroscopic data for engine diagnostic applications

A description is given of research based on a series of spectra taken from the Diagnostic Test Facility (DTF) plume at NASA-Stennis Space Center. The DTF was designed to obtain spectra scaling approximately to that of the SSME, yet allow full control of dopant and thruster conditions. DTF spectra were used in this research to develop a technique for quantitative identification of an alloy. A mathematically based identification technique was tried, with reasonable sucess for one-element alloys, and only fair success for a two-element alloy. This approach was found to have the simplicity required for DSP implementation, thus allowing real-time diagnosis as a possibility. Spreadsheets were organized to handle the proliferation of development equations required, which number about 50,000. The identification work reinforced the presence of nonlinearity to dopant level.

Nail, Bert↗
NASA NTRS1991

Plasma diagnostic capabilities of the Soft X-ray Telescope on Solar-A

The predicted response of the Solar-A Soft X-ray Telescope (SXT) to various solar targets is presented. It is found that the SXT is very sensitive and should be able to observe active regions and flares at its nominal cadence with exposure times ranging from 0.0001 to 1 s. The SXT temperature diagnostic capabilities are presented for various combinations of the X-ray filters.

Strong, K. T.↗
NASA NTRS1991

Multi-Spectral Solar Telescope Array. V - Temperature diagnostic response to the optically thin solar plasma

The compact soft X-ray/EUV/FUV multilayer coated telescopes developed for solar chromosphere, corona, and corona/solar-wind interface studies permit the use of conventional (Cassegrain, Herschelian, etc.) configurations. The multilayer coatings also allow a narrow-wavelength band to be selected for imaging. NASA's Multi-Spectral Solar Telescope Array is composed of 17 of these compact telescopes; attention is given to their ability to obtain temperature-diagnostic information concerning the solar plasma.

Deforest, Craig E.↗
NASA NTRS1991

Stennis Space Center's approach to liquid rocket engine health monitoring using exhaust plume diagnostics

Details are presented of the approach used in a comprehensive program to utilize exhaust plume diagnostics for rocket engine health-and-condition monitoring and assessing SSME component wear and degradation. This approach incorporates both spectral and video monitoring of the exhaust plume. Video monitoring provides qualitative data for certain types of component wear while spectral monitoring allows both quantitative and qualitative information. Consideration is given to spectral identification of SSME materials and baseline plume emissions.

Gardner, D. G.↗
NASA NTRS1991

Diagnostic reasoning techniques for selective monitoring

An architecture for using diagnostic reasoning techniques in selective monitoring is presented. Given the sensor readings and a model of the physical system, a number of assertions are generated and expressed as Boolean equations. The resulting system of Boolean equations is solved symbolically. Using a priori probabilities of component failure and Bayes' rule, revised probabilities of failure can be computed. These will indicate what components have failed or are the most likely to have failed. This approach is suitable for systems that are well understood and for which the correctness of the assertions can be guaranteed. Also, the system must be such that changes are slow enough to allow the computation.

Homem-De-mello, L. S.↗
NASA NTRS1992

Compton backscattered annihilation line emission: A new diagnostic of accreting compact sources

It is shown that Compton scattering of 511 keV electron-positron annihilation radiation produces a line like feature at approx. 170 keV from backscattered photons. Assuming a simple model of an accretion disk around a compact source, the spectrum is explored of the spectrum of Compton scattered annihilation line emission for a range of conditions. It is further shown that such Compton baskscattering of annihilation line emission from the inner edge of an accretion disk could account for the previously unidentified 170 keV line emission and high energy continuum observed from a variable, compact source, or sources, of annihilation radiation near the Galactic Center. Identification of the observed 170 keV line as an annihilation line reflection feature provides strong new evidence that the source of the emission is an accreting compact object. Further study of these features in existing spectra and in forthcoming GRO observation of these and other sources can provide unique new diagnostics of the innermost regions of accretion disks around compact objects.

Lingenfelter, Richard E.↗
NASA NTRS1992

A fiber optic sensor for ophthalmic refractive diagnostics

This paper demonstrates the application of a lensless fiber optic spectrometer (sensor) to study the onset of cataracts. This new miniaturized and rugged fiber optic probe is based upon dynamic light scattering (DLS) principles. It has no moving parts, no apertures, and requires no optical alignment. It is flexible and easy to use. Results are presented for cold-induced cataract in excised bovine eye lenses, and aging effects in excised human eye lenses. The device can be easily incorporated into a slit-lamp apparatus (ophthalmoscope) for complete eye diagnostics.

Ansari, Rafat R.↗
NASA NTRS1992

Plasma erosion rate diagnostics using laser-induced fluorescence

An optical technique for measuring the sputtering rate of a molybdenum surface immersed in a xenon plasma has been developed and demonstrated. This approach, which may be useful in real-time wear diagnostics for ion thrusters, relies on laser-induced fluorescence to determine the density of sputtered molybdenum atoms.

Gaeta, C. J.↗
NASA NTRS1991

The theory and diagnostic promise of supernova gamma-rays

The diagnostic power of gamma-ray and X-ray observations of supernovae of all types is reviewed. The basic features of supernova gamma-ray emission and the beginnings of a program to characterize the entire family of supernovae in gamma light are outlined.

Burrows, Adam↗
NASA NTRS1992

The potential for plasma diagnostics from stellar extreme-ultraviolet observations

A description of the lines from the most abundant ions in the EUV spectrum in the range 50-500 A that have special diagnostic significance is presented. These lines are from plasmas in the temperature range from 10 exp 5 to 10 exp 7 K. Their utility for determining temperature, density, and abundances is demonstrated. An objective grating spectrometer, based on the Skylab slitless spectrograph, for making celestial observations in the EUV spectral region with high spectral resolution is also described. Such an instrument, if equipped with a multilayer grating, can achieve efficiencies over limited EUV wavelength ranges that rival much larger telescope-spectrometer instruments for the observation of stars and other celestial objects.

Feldman, U.↗