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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 271 records · Page 15

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NASA NTRS1991

Monitoring and control technologies for bioregenerative life support systems/CELSS

The development of a controlled Ecological Life Support System (CELSS) will require NASA to develop innovative monitoring and control technologies to operate the different components of the system. Primary effort over the past three to four years has been directed toward the development of technologies to operate a biomass production module. Computer hardware and software required to operate, collect, and summarize environmental data for a large plant growth chamber facility were developed and refined. Sensors and controls required to collect information on such physical parameters as relative humidity, temperature, irradiance, pressure, and gases in the atmosphere; and PH, dissolved oxygen, fluid flow rates, and electrical conductivity in the nutrient solutions are being developed and tested. Technologies required to produce high artificial irradiance for plant growth and those required to collect and transport natural light into a plant growth chamber are also being evaluated. Significant effort was directed towards the development and testing of a membrane nutrient delivery system required to manipulate, seed, and harvest crops, and to determine plant health prior to stress impacting plant productivity are also being researched. Tissue culture technologies are being developed for use in management and propagation of crop plants. Though previous efforts have focussed on development of technologies required to operate a biomass production module for a CELSS, current efforts are expanding to include technologies required to operate modules such as food preparation, biomass processing, and resource (waste) recovery which are integral parts of the CELSS.

Knott, William M.↗

NASA NTRS1991

High resolution gamma-ray astronomy - Observations and predictions of line shapes

The shapes of gamma-ray lines carry unique information about the physical processes and conditions in astrophysical sites. Galactic center and SN 1987A lines have been observationally resolved allowing their shapes to be studied. There are also significant new theoretical results concerning line shapes from Type I supernovae, supernova remnants and the interstellar medium. New work is presented on a simple treatment of line profiles for rotating disks and spherical shells.

Bhattacharya, Dipen↗

NASA NTRS1991

Flow visualization and flow field measurements of a 1/12 scale tilt rotor aircraft in hover

The results are given of flow visualization studies and inflow velocity field measurements performed on a 1/12 scale model of the XV-15 tilt rotor aircraft in the hover mode. The complex recirculating flow due to the rotor-wake-body interactions characteristic of tilt rotors was studied visually using neutrally buoyant soap bubbles and quantitatively using hot wire anemometry. Still and video photography were used to record the flow patterns. Analysis of the photos and video provided information on the physical dimensions of the recirculating fountain flow and on details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Recirculating flows were also observed along the length of the fuselage. Hot wire anemometry results indicate that the wing under the rotor acts to obstruct the inflow causing a deficit in the inflow velocities over the inboard region of the model. Hot wire anemometry also shows that the turbulence intensities in the inflow are much higher in the recirculating fountain reingestion zone.

Coffen, Charles D.↗

NASA NTRS1991

Palomar Planet-Crossing Asteroid Survey (PCAS) January 1990 - February 1991

Several of our near-Earth asteroid (NEA) discoveries made relatively close approaches to the Earth allowing successful radar observations to be made. Detection of echoes from these asteroids provides otherwise unavailable information about their physical properties. Also, our role in alerting radar astronomers about new candidate asteroids makes it possible for them to acquire critical astrometry which improves the orbital elements of the new discovery.

Helin, Eleanor F.↗

NASA NTRS1993

Planetary protection issues for the MESUR mission: Probability of growth (Pg)

The purpose of the workshop was to re-evaluate the existing guidelines for the probability of growth of terrestrial organisms on Mars that were established by the National Academy of Sciences following the Viking Mission. A panel of specialists in microbiology and allied fields reviewed this issue in the light of current information about the physical and chemical environments expected on Mars. Their deliberations resulted in the virtually unanimous conclusion that the existing Pg guidelines were either appropriate or that the values for Pg should be further reduced. Individual assessments of this problem by each of the participants, together with those of additional invited experts are included.

Klein, Harold P.↗

NASA NTRS1991

Quasars and galaxy formation

Observations of high redshift quasars provide direct information on the physical state of the universe at early epochs. The available data suggest well advanced structure formation even at the highest known quasar redshifts and are most easily understood in scenarios in which galaxies primarily formed at redshifts well above 5. Ten separate lines of argument supporting this general conclusion are summarized.

Turner, Edwin L.↗

NASA NTRS1991

Flow visualization and flow field measurements of a 1/12 scale tilt rotor aircraft in hover

Coffen, Charles D.↗

NASA NTRS1991

Wave interactions with continuous fractal layers

Many natural structures possess self-similar multiscales which can be characterized by power law spectra. Under appropriate conditions, knowledge of the strength of these scale sizes provides information on the physical processes which formed these objects. In this paper, we investigate wave interactions with continuous fractal layers which model geological and variegated structures. Since fractal characteristics of the layers are embedded in the scattered field, they can be retrieved under appropriate conditions. This inversion can be performed in either the frequency or the time domain as desired.

Kim, Y.↗

NASA NTRS1993

Core formation in the Moon: The mystery of the excess depletion of Mo, W and P

We have evaluated siderophile element depletion models for the Moon in light of our improved statistical treatment of siderophile element abundance data and new information on the physics of core formation. If core formation occurred in the Moon at the large degrees of partial melting necessary for metal segregation, according to recent estimates, then a significant inconsistency (not seen in the eucrite parent body) exists in the depletion of the incompatible siderophile elements Mo, W, and P, compared to other siderophile elements in the Moon. The siderophile data, with the exception of Mo, are most consistent with terrestrial initial siderophile abundances and segregation of a very small core in the Moon. Our improved abundance estimates and possible explanations for these discrepancies are discussed.

Newsom, H. E.↗

NASA NTRS1995

Properties of plasma sprayed bond coats

Increasing bond coat oxidation resistance has been clearly linked to increasing durability of the ceramic layer of TBC's. However, recent studies have shown that significant differences in TBC life can be achieved for different bond coats that have little or no difference in oxidation behavior. These results suggest bond coat properties other than oxidation resistance can also influence TBC life. A determination of which properties affect TBC life and an understanding of how these properties affect TBC life could be valuable in designing new, more durable TBC's. Unfortunately, there is little existing information on the physical and mechanical properties of bond coat materials and there are fewer comparative studies that can be used to determine which properties are important to TBC life. This paper compares the properties of three bond coat compositions that have similar oxidation behavior but different TBC lives. Analysis of the properties indicates that the coefficient of thermal expansion and stress relaxation (creep) behavior of the three alloys are strongly correlated to the observed differences in TBC life.

Brindley, W. J.↗

NASA NTRS1995

Wireless Infrared Data Link

Infrared transmitter and receiver designed for wireless transmission of information on measured physical quantity (for example, temperature) from transducer device to remote-acquisition system. In transmitter, output of transducer amplified and shifted with respect to bias or reference level, then fed to voltage-to-frequency converter to control frequency of repetition of current pulses applied to infrared-light-emitting diode. In receiver, frequency of repetition of pulses converted back into voltage indicative of temperature or other measured quantity. Potential applications include logging data while drilling for oil, transmitting measurements from rotors in machines without using slip rings, remote monitoring of temperatures and pressures in hazardous locations, and remote continuous monitoring of temperatures and blood pressures in medical patients, who thus remain mobile.

Roth, Timothy E.↗

NASA NTRS1995

Ignition and combustion of bulk metals under elevated, normal and reduced gravity conditions

This research effort is aimed at providing further insight into this multi-variable dependent phenomena by looking at the effects of gravity on the ignition and combustion behavior of metals. Since spacecraft are subjected to higher-than-1g gravity loads during launch and reentry and to zero-gravity environments while in orbit, the study of ignition and combustion of bulk metals at different gravitational potentials is of great practical concern. From the scientific standpoint, studies conducted under microgravity conditions provide simplified boundary conditions since buoyancy is removed, and make possible the identification of fundamental ignition mechanisms. The effect of microgravity on the combustion of bulk metals has been investigated by Steinberg, et al. on a drop tower simulator. However, no detailed quantitative work has been done on ignition phenomena of bulk metals at lower or higher-than-normal gravitational fields or on the combustion characteristics of metals at elevated gravity. The primary objective of this investigation is the development of an experimental system capable of providing fundamental physical and chemical information on the ignition of bulk metals under different gravity levels. The metals used in the study, iron (Fe), titanium (Ti), zirconium (Zr), magnesium (Mg), zinc (Zn), and copper (Cu) were selected because of their importance as elements of structural metals and their simple chemical composition (pure metals instead of multi-component alloys to avoid complication in morphology and spectroscopic studies). These samples were also chosen to study the two different combustion modes experienced by metals: heterogeneous or surface oxidation, and homogeneous or gas-phase reaction. The experimental approach provides surface temperature profiles, spectroscopic measurements, surface morphology, x-ray spectrometry of metals specimens and their combustion products, and high-speed cinematography of the heating, ignition and combustion stages of the metal specimen. This paper summarizes the results obtained to date from experiments conducted under normal and high-gravity conditions.

Abbud-Madrid, Angel↗

NASA NTRS1995

Kilometric type 3 radio bursts observed from high southern ecliptic latitudes by Ulysses

The Ulysses URAP experiment has provided the first measurements of remote and in-situ wave phenomena from high southern latitudes. Remote sensing of type 3 solar radio bursts constitute an important component of the Ulysses observations. Type 3 radio emissions, which have never before been viewed from outside the ecplitic plane, have been observed by Ulysses to its maximum southern latitude (approximately 80 deg S), although their frequency of occurrence has generally diminished due to the declining phase of the solar cycle. In addition, the Ulysses radio receiver measures both the direction of arrival and the complete polarization state of incident radiation. These physical parameters provide information on the origin and nature of the radio emission. Preliminary analyses have indicated that kilometric type 3 radiation is often approximately 10-20% circularly polarized at the highest URAP frequencies. New directional information provides crucial information on the effects of beaming and scattering of the radiation in the interplanetary medium.

Reiner, M. J.↗

NASA NTRS1997

Broadband High-Energy Observations of the Superluminal Jet Source GRO J1655-40 During an Outburst

The X-ray/radio transient superluminal jet source GRO J1655-40 was recently suggested to contain a black hole from optical observations. Because it is a relatively close-by system (d approximately 3.2 kpc), it can likely provide us with rich information about the physics operating in both Galactic and extragalactic jet sources. We present the first simultaneous broadband high-energy observations of GRO J1655-40 during the 1995 July-August outburst by three instruments: ASCA, WATCH/Granat, and BATSE/CGRO, in the energy band from 1 keV to 2 MeV. Our observations strengthen the interpretation that GRO J1655-40 contains a black hole. We detected a two-component energy spectrum, commonly seen from other Galactic black hole binaries, but never detected from a neutron star system. Combining our results with the mass limits derived from optical radial velocity and orbital period measurements, we further constrain the mass of the central object to be between 3.3 and 5.8 solar mass, above the well-established mass upper limit of 3.2 solar mass for a neutron star (the optical mass function for GRO J1655-40 is 3.16 + 0.2 solar mass). This system is therefore the first Galactic superluminal jet source for which there is strong evidence that the system contains a stellar mass black hole. The inclination angle of the binary system is constrained to be between 76 deg and 87 deg, consistent with estimates obtained from optical light curves and radio jet kinematics.

Zhang, S. N.↗

NASA NTRS1997

Demonstration of Wavelet Techniques in the Spectral Analysis of Bypass Transition Data

A number of wavelet-based techniques for the analysis of experimental data are developed and illustrated. A multiscale analysis based on the Mexican hat wavelet is demonstrated as a tool for acquiring physical and quantitative information not obtainable by standard signal analysis methods. Experimental data for the analysis came from simultaneous hot-wire velocity traces in a bypass transition of the boundary layer on a heated flat plate. A pair of traces (two components of velocity) at one location was excerpted. A number of ensemble and conditional statistics related to dominant time scales for energy and momentum transport were calculated. The analysis revealed a lack of energy-dominant time scales inside turbulent spots but identified transport-dominant scales inside spots that account for the largest part of the Reynolds stress. Momentum transport was much more intermittent than were energetic fluctuations. This work is the first step in a continuing study of the spatial evolution of these scale-related statistics, the goal being to apply the multiscale analysis results to improve the modeling of transitional and turbulent industrial flows.

Lewalle, Jacques↗

NASA NTRS1998

A Study of the Structure of the Source Region of the Solar Wind in Support of a Solar Probe Mission

Despite the richness of the information about the physical properties and the structure of the solar wind provided by the Ulysses and SOHO observations, fundamental questions regarding the nature of the coronal heating mechanisms, their source, and the manifestations of the fast and slow solar wind, still remain unanswered. The last unexplored frontier to establish the connection between the structure and dynamics of the solar atmosphere, its extension into interplanetary space, and the mechanisms responsible for the evolution of the solar wind, is the corona between 1 and 30 R(sub s). A Solar Probe mission offers an unprecedented opportunity to explore this frontier. The uniqueness of this mission stems from its trajectory in a plane perpendicular to the ecliptic which reaches within 9 R(sub s), of the solar surface over the poles and 3 - 9 R(sub s), at the equator. With a complement of simultaneous in situ and remote sensing observations, this mission is destined to have a significant impact on our understanding of the fundamental processes that heat the corona and drive the solar wind. The Solar Probe should be able to detect remnants and signatures of the processes which heat the corona and accelerate the solar wind. The primary objective of this proposal was to explore the structure of the different source regions of the solar wind through complementary observational and theoretical studies in support of a Solar Probe mission.

Habbal , Shadia R.↗

NASA NTRS1996

Correlative Studies of Solar Flares

In October 1992, post-doc Haimin Wang was awarded a Compton GRO Fellowship by NASA to study the flares observed simultaneously by BATSE (Burst and Transient Experiment), OVRO (Owens Valley Radio Observatory), Yohkoh, and BBSO (Big Bear Solar Observatory). During the past four years, a number of flares have been analyzed in detail. Substantial information on the physics of flares came out of these studies.

Zirin, Harold↗

NASA NTRS1998

Multipoint Measurements in an Axisymmetric Sudden Expansion

A flying wire system was utilized in conjunction with a rake of nine cross-wire probes to obtain simultaneous velocity measurements in an axisymmetric sudden expansion at a Reynolds number of 41,000. From these measurements, the correlation tensor could be calculated. Knowledge of the two-point correlation tensor reveals more in-depth information of the physical attributes of this flow. The two point correlation tensor allowed for calculation of the integrated length scales in both the radial and axial directions. This gives insight into the growth of structures with increasing downstream distance and at different radial locations through out the sudden expansion. The length scales were calculated by integrating the two-point correlation tensor in the radial direction from the centerline to the outer pipe wall and by integrating between several step heights for the axial direction. Calculated correlations at z/h = 8 and 9 at r/R = 0.46 showed a correlation length of 1/3 step height for the radial direction. It was found that length scales in the radial direction became larger with increasing radius with peaks at 0.70 e r/R c 0.81 but then decreased slightly towards the wall. Length scales in the axial direction yielded a recirculating bubble on the order of 3 step heights in the recirculating region. After the recirculating region, the length scales decreased to 1/4 of a step height.

Eaton, Erroll L.↗