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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 109 records · Page 6
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NASA NTRS1986

Liquid helium cooled Fabry-Perot spectrometers

An account is given of two successful efforts to construct cryogenic Fabry-Perot interferometers that are sufficiently compact and stable for such harsh conditions as those of balloon or space observations, as well as ground-based ones. Attention is given to the design features and performance of a Fabry-Perot interferometer incorporating an electromagnet actuator, the ISAS interferometer, a Fabry-Perot spectrometer with superconducting actuators, and the University of Arizona interferometer.

Okuda, H.↗
NASA NTRS1988

Planetary Geology: Goals, Future Directions, and Recommendations

Planetary exploration has provided a torrent of discoveries and a recognition that planets are not inert objects. This expanded view has led to the notion of comparative planetology, in which the differences and similarities among planetary objects are assessed. Solar system exploration is undergoing a change from an era of reconnaissance to one of intensive exploration and focused study. Analyses of planetary surfaces are playing a key role in this transition, especially as attention is focused on such exploration goals as returned samples from Mars. To assess how the science of planetary geology can best contribute to the goals of solar system exploration, a workshop was held at Arizona State University in January 1987. The participants discussed previous accomplishments of the planetary geology program, assessed the current studies in planetary geology, and considered the requirements to meet near-term and long-term exploration goals.

Source record↗
NASA NTRS1987

Near infrared spectroscopy of SN 1987A using the Kuiper Airborne Observatory

An IR spectrum (1.5-3.0 microns) of SN 1987A was obtained on UT April 16.3, 1987 with the University of Arizona Fourier-transform spectrometer on the NASA Kuiper Airborne Observatory. The dominant spectral features were a double-peaked P-alpha emission line and a sharp absorption edge in the continuum at 2.7 microns, both of which would have been obscured by strong telluric H2O absorptions at ground-based observatories. These IR features relate to models of the SN shell and to the role of dust in SN.

Larson, H. P.↗
NASA NTRS1989

Nonprincipal plane scattering of flat plates and pattern control of horn antennas

Using the geometrical theory of diffraction, the traditional method of high frequency scattering analysis, the prediction of the radar cross section of a perfectly conducting, flat, rectangular plate is limited to principal planes. Part A of this report predicts the radar cross section in nonprincipal planes using the method of equivalent currents. This technique is based on an asymptotic end-point reduction of the surface radiation integrals for an infinite wedge and enables nonprincipal plane prediction. The predicted radar cross sections for both horizontal and vertical polarizations are compared to moment method results and experimental data from Arizona State University's anechoic chamber. In part B, a variational calculus approach to the pattern control of the horn antenna is outlined. The approach starts with the optimization of the aperture field distribution so that the control of the radiation pattern in a range of directions can be realized. A control functional is thus formulated. Next, a spectral analysis method is introduced to solve for the eigenfunctions from the extremal condition of the formulated functional. Solutions to the optimized aperture field distribution are then obtained.

Balanis, Constantine A.↗
NASA NTRS1989

Crossflow-vortex instability and transition on a 45 deg swept wing

A crossflow vortex experiment on a 45 deg swept wing is currently being conducted in the Arizona State University Unsteady Wind Tunnel. The experimental apparatus is designed to produce crossflow-dominated transition by simulating infinite swept wing flow using contoured end liners in a closed throat wind tunnel. Stationary fixed-wavelength crossflow vortices are observed at several chord Reynolds numbers. The vortex wavelength which is fixed for a given Reynolds number varies with Reynolds number approximately as predicted by linear stability theory, but with the predicted wavelengths about 30 percent larger than the observed wavelengths. Travelling waves are observed both in the frequency range predicted by linear stability theory and at higher frequencies. These higher frequency waves may be harmonics of the primary crossflow waves generated by a nonlinear parametric resonance phenomena.

Dagenhart, J. Ray↗
NASA NTRS1989

Navier-Stokes simulation of the crossflow instability in swept-wing flows

The computational modeling of the transition process characteristic of flows over swept wings are described. Specifically, the crossflow instability and crossflow/T-S wave interactions are analyzed through the numerical solution of the full three-dimensional Navier-Stokes equations including unsteadiness, curvature, and sweep. This approach is chosen because of the complexity of the problem and because it appears that linear stability theory is insufficient to explain the discrepancies between different experiments and between theory and experiments. The leading edge region of a swept wing is considered in a three-dimensional spatial simulation with random disturbances as the initial conditions. The work has been closely coordinated with the experimental program of Professor William Saric, examining the same problem. Comparisons with NASA flight test data and the experiments at Arizona State University were a necessary and an important integral part of this work.

Reed, Helen L.↗
NASA NTRS1989

Coded-aperture imaging in nuclear medicine

Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

Smith, Warren E.↗
NASA NTRS1989

Ga:Ge array development

Work at the University of Arizona and at Lawrence Berkeley Laboratory on the development of a far infrared array camera for the Multiband Imaging Photometer on the Space Infrared Telescope Facility (SIRTF) is discussed. The camera design uses stacked linear arrays of Ge:Ga photoconductors to make a full two-dimensional array. Initial results from a 1 x 16 array using a thermally isolated J-FET readout are presented. Dark currents below 300 electrons s(exp -1) and readout noises of 60 electrons were attained. Operation of these types of detectors in an ionizing radiation environment are discussed. Results of radiation testing using both low energy gamma rays and protons are given. Work on advanced C-MOS cascode readouts that promise lower temperature operation and higher levels of performance than the current J-FET based devices is described.

Young, Erick T.↗
NASA NTRS1989

Initial findings from a telescopic search for small comets near earth

An analysis is provided for the capabilities of the Spacewatch Camera operated at Kitt Peak National Observatory by the University of Arizona for the detection of the large flux of small comets in the vicinity of earth that is proposed by Frank et al. (1986). The characteristics of this telescope are used to determine its optimum operational mode for the detection of these small comets. It is concluded that the Spacewatch Camera can detect these small comets near earth if the proposed large fluxes in prograde orbits are present. It is unlikely that previous optical telescope surveys would have detected these objects. A heretofore undetected, large flux of small objects was detected. The characteristics of these objects appear to be in general agreement with those of the comets proposed by Frank et al. (1986). No other known population of objects or other effects that could provide the observed optical signatures has been identified at this time. Because these initial results are of such great importance to our perception of the solar system, they should be conservatively treated as an initial result until confirmation is made with similar observations from other telescopes.

Yeates, C. M.↗
NASA NTRS1989

The development of crossflow vortices on a 45 degree swept wing

Three-dimensional boundary-layer experiments are currently being conducted on a 45 deg swept wing in the Arizona State University Unsteady Wind Tunnel. Crossflow-dominated transition is produced via a model with contoured end liners to simulate infinite swept-wing flow. Fixed-wavelength stationary and traveling crossflow vortex are observed. The stationary vortex wavelengths vary with Reynolds number as predicted by linear-stability theory, but with observed wavelengths which are about 25 percent smaller than theoretically predicted. The frequencies of the most-amplified moving waves are in agreement with linear-stability theory; traveling waves at higher frequencies than predicted are also observed. These higher-frequency waves may be harmonics of the primary crossflow waves generated by a parametric resonance phenomena. Boundary-layer profiles measured at several spanwise locations show streamwise disturbance profiles characteristic of the crossflow instability. Near the transition location, severe distortions of the laminar boundary-layer profiles are observed. Mean-profile measurements are compared to theoretical predictions.

Mousseux, Marc C.↗
NASA NTRS1990

A balloon-borne 102-cm telescope for far-infrared astronomy

In the early 1970's, the Smithsonian Astrophysical Observatory and the University of Arizona engaged in a cooperative program to develop a balloon-borne 102-cm telescope capable of carrying out far infrared (40 to 250 micron) observations of astronomical interest above the earth's atmosphere. Since 1972, the telescope has flown and successfully recovered a total of nineteen times. Thirteen of the flights produced high-quality astronomical data, resulting in more than 92.5 hours of photometric and spectroscopic observations of numerous objects, such as H 2 regions, dark clouds, molecular clouds, a planetary nebula, a galaxy, the galactic center, the planets, and an asteroid. From the launch site in Palestine, Texas, sources as far south as -50 degrees declination were observed. The balloon-borne telescope was one of the most sensitive instruments ever used for observation in the far infrared region of the spectrum. It was most productive in producing high resolution maps of large areas (typically square degrees) centered on known H 2 regions, molecular clouds, and dark cloud complexes. In many cases, these scans produced the first far infrared maps of these regions, and many new sources were discovered. The results have led to a better understanding of the distribution of gas and dust in these regions, the evolution of H 2 regions, and the processes of star formation in giant molecular clouds. The following topics are presented: (1) the focal plane instrumentation; (2) the history and flight record; (3) scientific results and publications; (4) eduational aspects; and (5) future planes.

Fazio, Giovanni G.↗
NASA NTRS1990

A composition comparison between comets P/Halley and P/Brorsen-Metcalf

The appearance of comet Brorsen-Metcalf in 1989 following only a few years on the heels of comet Halley in 1986 gave an unusual opportunity to compare two comets of similar orbital elements but potentially different physical and chemical characteristics. Photometric spectral data were acquired for Brorsen-Metcalf on two dates: 13 July 1989 and 2 August 1989. The observations were performed with the 154 cm Catalina Telescope of the University of Arizona Observatories. The spectrum for 13 July 1989 is compared to a Halley spectrum. The general appearance of the spectra is very similar, both comets showing emission due to C2, NH2, OI(D-1), and CN. Neither displays any emission features that are exclusive to only one of the two. Since water is now reasonably well established as the major driving force in the activity of a comet, the H2O production rate for comet Brorsen-Metcalf was calculated. The relative ratios between the production rates of the various species obtained from the data are presented. Results are summarized in tabular form. All species are compared to the H2O production rate of the two comets. The results indicate that C2 originates from an extended source of dust particles or small polymers in addition to parent molecules. The lower production rates of C2 and CN in Brorsen-Metcalf correlate well with both the lower dust production and their smaller increase as the comet approaches the sun. Even without a mode, the spectroscopic observations of Brorsen-Metcalf allowed significant compositional conclusions to be drawn. The NH2 abundance is lower by about a factor of three which appears to be independent of heliocentric distance. Both C2 and CN are less abundant in Brorsen-Metcalf than in Halley and do not seem to participate as much in the strong increase as the comet approaches the sun. The lower H2O production rate implies that the active surface area of the comet Brorsen-Metcalf is much smaller, or equivalently the comet as a whole is much smaller. The substantially lower continuum level for Brorsen-Metcalf cannot readily be explained by smaller or larger active surface area, and must be intrinsic to the comet's embedded dust-to-ice ratio, or to an overall smaller-sized dust grain population.

Disanti, Michael A.↗
NASA NTRS1990

NASA Space Engineering Research Center for utilization of local planetary resources

The University of Arizona and NASA have joined to form the UA/NASA Space Engineering Research Center. The purpose of the Center is to discover, characterize, extract, process, and fabricate useful products from the extraterrestrial resources available in the inner solar system (the moon, Mars, and nearby asteroids). Individual progress reports covering the center's research projects are presented and emphasis is placed on the following topics: propellant production, oxygen production, ilmenite, lunar resources, asteroid resources, Mars resources, space-based materials processing, extraterrestrial construction materials processing, resource discovery and characterization, mission planning, and resource utilization.

Ramohalli, Kumar↗
NASA NTRS1990

Energy management analysis of lunar oxygen production

Energy load models in the process of hydrogen reduction of ilmenite for lunar oxygen production are being developed. The load models will be used as a first step to ultimately determine the optimal energy system needed to supply the power requirements for the process. The goal is to determine the energy requirements in the process of hydrogen reduction of ilmenite to produce oxygen. The general approach is shown, and the objectives are to determine the energy loads of the processes in the system. Subsequent energy management studies will be made to minimize the system losses (irreversibilities) and to design optimal energy system power requirements. A number of processes are being proposed as possible candidates for lunar application and some detailed experimental efforts are being conducted within this project at the University of Arizona. Priorities are directed toward developing the energy models for each of the proposed processes being considered. The immediate goals are to identify the variables that would impact energy requirements and energy sources of supply.

Fazzolari, R.↗
NASA NTRS1991

Mining the air - Resources of other worlds may reduce mission costs

It is proposed that the mining of resources on another planet to support operations there and also to provide a means for the return trip to earth provides a less expensive way to send humans beyond low earth orbit to live on the moon and to explore Mars. Since a large fraction of any chemical propellant combination is the oxidizer that burns with the fuel to generate the rocket jet, and for life support, the generation of oxygen from any of its atmospheric or mineral compounds is a valuable capability. Such materials include the lunar minerals ilmenite and anorthite, Martian permafrost, water ice at the Martian poles, and atmospheric carbon dioxide on Mars. The possibilities of developing such technologies are discussed and the prospects of developing building materials for such facilities from local resources are considered. The role of the Space Engineering Research Center at the University of Arizona in exploring the use of local planetary resources is noted.

Ramohalli, Kumar↗
NASA NTRS1991

Physical studies of small asteroids. I - Lightcurves and taxonomy of 10 asteroids

Photometric observations of 10 small asteroids (10 km or less in diameter), obtained using the 1.5-m Mt. Lemmon and 2.3-m Kitt Peak telescopes of the University of Arizona during 1986-1987, are reported. The instrumentation and data-reduction techniques employed are described, and the results are presented in tables and light-curve plots and briefly characterized.

Wisniewski, W. Z.↗
NASA NTRS1990

Experiments on swept-wing boundary layers

Three-dimensional boundary-layer experiments are currently being conducted on a 45-deg swept wing in the Arizona State University Unsteady Wind Tunnel. Crossflow-dominated transition is produced via a model with contoured end liners to simulate infinite swept-wing flow. Fixed-wavelength stationary and traveling crossflow vortices are observed. The stationary vortex wavelengths vary with Reynolds number as predicted by linear-stability theory, but with observed wavelengths which are about 25 percent smaller than theoretically predicted. The frequencies of the most amplified moving waves are in agreement with linear stability theory; however, traveling waves at higher frequencies than predicted are also observed. These higher-frequency waves may be harmonics of the primary crossflow waves generated by a parametric resonance phenomena. Boundary-layer profiles measured at several spanwise locations show streamwise disturbance profiles characteristic of the crossflow instability.

Dagenhart, J. R.↗
NASA NTRS1992

What can we learn about impact mechanics from large craters on Venus?

More than 50 unequivocal peak-ring craters and multiringed impact basins have been identified on Venus from Earth-based Arecibo, Venera 15/16, and Magellan radar images. These ringed craters are relatively pristine, and so serve as an important new dataset that will further understanding of the structural and rheological properties of the venusian surface and of impact mechanics in general. They are also the most direct analogues for craters formed on the Earth in Phanerozoic time. Finite-element simulations of basin collapse and ring formation were undertaken in collaboration with V. J. Hillgren (University of Arizona). These calculations used an axisymmetric version of the viscoelastic finite element code TECTON, modeled structures on the scale of Klenova or Meitner, and demonstrated two major points. First, viscous flow and ring formation are possible on the timescale of crater collapse for the sizes of multiringed basins seen on Venus and heat flows appropriate to the plant. Second, an elastic lithosphere overlying a Newtonian viscous asthenosphere results mainly in uplift beneath the crater. Inward asthenospheric flow mainly occurs at deeper levels. Lithospheric response is dominantly vertical and flexural. Tensional stress maxima occur and ring formation by normal faulting is predicted in some cases, but these predicted rings occur too far out to explain observed ring spacings on Venus (or on the Moon). Overall, these estimates and models suggest that multiringed basin formation is indeed possible at the scales observed on Venus. Furthermore, due to the strong inverse dependence of solid-state viscosity on stress, the absence of Cordilleran-style ring faulting in craters smaller than Meitner or Klenova makes sense. The apparent increase in viscosity of shock-fluidized rock with crater diameter, greater interior temperatures accessed by larger, deeper craters, and decreased non-Newtonian viscosity associated with larger craters may conspire to make the transition with diameter from peak-ring crater to Orientale-type multiringed basin rather abrupt.

Mckinnon, William B.↗