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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

High frequency power distribution system

The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

Patel, Mikund R.↗
NASA NTRS1988

Mapping of auroral kilometric radiation sources to the aurora

Auroral kilometric radiation (AKR) and optical auroral emissions are observed simultaneously using plasma wave instrumentation and auroral imaging photometers carried on the DE 1 spacecraft. The DE 1 plasma wave instrument measures the relative phase of signals from orthogonal electric dipole antennas, and from these measurements, apparent source directions can be determined with a high degree of precision. Wave data are analyzed for several strong AKR events, and source directions are determined for several emission frequencies. By assuming that the AKR originates at cyclotron resonant altitudes, a candidate source field line is identified. When the selected source field line is traced down to auroral altitudes on the concurrent DE 1 auroral image, a striking correspondece between the AKR source field line and localized auroral features is produced. The magnetic mapping study provides strong evidence that AKR sources occur on field lines associated with discrete auroral arcs, and it provides confirmation that AKR is generated near the electron cyclotron frequency.

Huff, R. L.↗
NASA NTRS1993

C/O atomic ratios in micrometer-size crushed grains from Antarctic micrometeorites and two carbonaceous meteorites

Antarctic micrometeorites (AMM's) have similarities (but also differences) with primitive meteorites, such as unequilibrated mineral assemblages. To further assess such similarities, we have measured the carbon content of micrometeorites and meteorites (Orgueil and Murchison), as determined in a random selection of micrometer-size crushed grain, with an analytical transmission electron microscope. Such analyses yield the C/O atomic ratio, the major and minor elements contents, and the textural features of the grains on a scale of approx. equal to 100 nanometers. An important proportion of micrometeorites from both the 100-400 micron and the 50-100 micron size fractions contains much more carbon than CI chondrite Orgueil. The average C-content of all micrometeorites in these two size fractions amount to approximately 1.8 x CI, and approximately 0.8 x CI, respectively (CI refers to the bulk C-content of Orgueil, of about 3.5 percent by weight). Carbon is usually not homogeneously distributed in the micrometeorite but is concentrated in C-rich grains. So far, most of these grains are amorphous, and seem to be associated with an oxidized Fe-rich phase (possibly a variety of 'dirty' magnetite). About 5 percent of them have the composition of 'COPS', a phase additionally enriched in O, P, and S.

Perreau, M.↗
NASA NTRS1995

The Astro Edge solar array for the NASA SSTI Clark Spacecraft

The Astro Edge solar array is a new and innovative reflective low concentrator power generating system which has been selected for the CTA Incorporate/Lockheed Martin Clark spacecraft under the NASA Small Spacecraft Technology Initiative (SSTI) program. In support of this program, Astro Aerospace Corporation has produced one qualification and two flight solar array wings to support a July 1996 launch. The Astro Edge solar array was selected as a new technology to benefit future NASA, military and commercial missions by providing high specific power, high deployed stiffness, low stowed volume, low risk, and cost reduction features which meet the agency's 'better, faster, cheaper' goals. This novel array accounts for five of the thirty-six advanced technologies which the Clark spacecraft will demonstrate. A brief SSTI Astro Edge solar array program overview is presented. Completed qualification and acceptance testing is discussed. Finally, the major discriminators which make the Astro Edge solar array 'better, faster, cheaper' technology are provided.

Spence, B. R.↗
NASA NTRS2000

A New Look at Aerosol Optical Models in the MODIS/AERONET ERA

The MODerate resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra satellite will permit the first time operational satellite retrievals of atmospheric aerosols over land. The retrieval uses dynamic models of aerosol optical properties developed from ground-based sun/sky radiometer data at selected specific locations. Three recent developments argue for a reevaluation of these optical models. (1) The expansion of the AERONET sun/sky radiometer network into new geographical regions that possibly features aerosols with different properties. (2) The development of the Dubovik sky radiance inversion that now offers a more comprehensive retrieval of aerosol optical properties. (3) The launch of the Terra satellite and acquisition of MODIS data that will reveal exactly how well the models perform.

Remer, Lorraine↗
NASA NTRS2002

Analysis of High Order Difference Methods for Multiscale Complex Compressible Flows

Accurate numerical simulations of complex multiscale compressible viscous flows, especially high speed turbulence combustion and acoustics, demand high order schemes with adaptive numerical dissipation controls. Standard high resolution shock-capturing methods are too dissipative to capture the small scales and/or long-time wave propagations without extreme grid refinements and small time steps. An integrated approach for the control of numerical dissipation in high order schemes with incremental studies was initiated. Here we further refine the analysis on, and improve the understanding of the adaptive numerical dissipation control strategy. Basically, the development of these schemes focuses on high order nondissipative schemes and takes advantage of the progress that has been made for the last 30 years in numerical methods for conservation laws, such as techniques for imposing boundary conditions, techniques for stability at shock waves, and techniques for stable and accurate long-time integration. We concentrate on high order centered spatial discretizations and a fourth-order Runge-Kutta temporal discretizations as the base scheme. Near the bound-aries, the base scheme has stable boundary difference operators. To further enhance stability, the split form of the inviscid flux derivatives is frequently used for smooth flow problems. To enhance nonlinear stability, linear high order numerical dissipations are employed away from discontinuities, and nonlinear filters are employed after each time step in order to suppress spurious oscillations near discontinuities to minimize the smearing of turbulent fluctuations. Although these schemes are built from many components, each of which is well-known, it is not entirely obvious how the different components be best connected. For example, the nonlinear filter could instead have been built into the spatial discretization, so that it would have been activated at each stage in the Runge-Kutta time stepping. We could think of a mechanism that activates the split form of the equations only at some parts of the domain. Another issue is how to define good sensors for determining in which parts of the computational domain a certain feature should be filtered by the appropriate numerical dissipation. For the present study we employ a wavelet technique introduced in as sensors. Here, the method is briefly described with selected numerical experiments.

Sjoegreen, Bjoern↗
NASA NTRS2005

AIRS radiometric calibration validation for climate research

Climate research using data from satellite based radiometers makes extreme demands on the traceability and stability of the radiometric calibration. The selection of a cooled grating array spectrometer for the Atmospheric Infrared Sounder, AIRS, is key, but does not ensured that AIRS data will be of climate quality. Additional design features, plus additional pre-launch testing, and extensive on-orbit calibration subsystem monitoring beyond what would suffice for application of the data to weather forecasting were required to ensure the radiometric data quality required for climate research. Validation that climate data quality are being generated makes use of the sea surface skin temperatures (SST and (obs-calc).

calibration↗
NASA NTRSDate not supplied

Advancing Autonomy in Distributed Space Systems: Insights From on-Orbit Testing with the Starling 1.0 Mission

Autonomous decision-making is crucial for enhancing mission effectiveness in Distributed Space Systems (DSS), particularly in multi-spacecraft operations where communication constraints and mission complexity pose challenges. The Distributed Spacecraft Autonomy (DSA) team at NASA’s Ames Research Center is advancing autonomy in DSS through five key technical areas: distributed resource and task management, reactive operations, system modeling and simulation, human-swarm interaction, and ad hoc network communications. The DSA experiment onboard the Starling 1.0 Mission showcases collaborative resource allocation for multi-point science data collection with four small spacecraft. Autonomy in decision-making is highlighted as a crucial factor for multi-spacecraft missions, enabling spacecraft to operate independently, reducing reliance on ground control. This capability is particularly significant for future deep-space missions, where communication delays and limited data transmission capacity make traditional command and control approaches impractical. This demonstration focuses on a GPS Channel Selection Experiment, leveraging emergent capabilities like "shared sampling" and "simultaneous sampling" to optimize channel selection across the spacecraft swarm. The experiment aims to capture ionospheric phenomena such as the Equatorial Ionization Anomaly and Polar Patches. The DSA system's autonomous reconfiguration ability is showcased, emphasizing its adaptability to natural phenomena without significant integration efforts. The GPS Channel Selection Experiment utilizes a dual-band GPS receiver to estimate plasma density in the ionosphere. Explorative and exploitative channel selections are employed based on the nature of observed phenomena. The performance of DSA algorithms is evaluated in terms of optimal channel allocations and responsiveness to changes in observed features. The DSA Flight Software utilizes the Core Flight System (cFS) framework, ensuring compatibility with the Starling 1.0 flight mission software. DSA showcases results from RTI’s Connext DDS Micro communication middleware, enabling message routing over the Ad-Hoc Network of Starling 1.0. This paper provides a comprehensive overview of the DSA experiment's initial results, emphasizing the advancements in autonomy for Distributed Space Systems and the successful collaboration with the Starling 1.0 mission.

Caleb Ashmore Adams↗
NASA NTRSDate not supplied

NASA GeneLab Multi-study Visualization Portal

NASA GeneLab has helped advance the field of Space Biology by providing a public repository where researchers can store, share, analyze and visualize the results of space flight related omics experiments. The GeneLab data visualization portal allows any user, regardless of bioinformatics knowledge or access to computational resources, to interact with the experimental data, draw their own conclusions, and gain insights about the effects of space on living systems. These tools help democratize scientific research and foster the NASA Open Science initiative. The new multi-study feature of the GeneLab visualization platform allows users to mine study metadata from RNA sequencing (RNA-seq) experiments to identify samples of interest by filtering datasets based on organism, tissue, assay technology type, and/or factor. Once samples are selected from multiple datasets, users can combine and normalize the sample data, then utilize the visualization displays, including Principal Component Analysis (PCA) plots, to assess sample distributions. Finally, users can perform differential gene expression analysis on the combined data and visualize the results through PCA plots, Volcano plots, Pair plots, Heatmap, Ideogram and Gene Set Enrichment Analysis. All user-generated results and visualizations will be available for download. Here, we present a biological study using samples from multiple GeneLab RNA-seq datasets and analyzed using the multi-study visualization platform to demonstrate inter- and intra-study variability, as well as commonly differentially expressed genes between spaceflight and ground control conditions across datasets. This new feature opens a wide range of possibilities and opportunities for further development including combining other assay technology types and integration with batch effect correction techniques and machine learning applications. Overall, this tool allows users to increase the statistical power of individual experiments, validate hypothesis, identify patterns, and opens the door to new and exciting research.

space biology↗
NASA NTRS1975

Airborne remote sensors applied to engineering geology and civil works design investigations

The usefulness of various airborne remote sensing systems in the detection and identification of regional and specific geologic structural features that may affect the design and location of engineering structures on major civil works projects is evaluated. The Butler Valley Dam and Blue Lake Project in northern California was selected as a demonstration site. Findings derived from the interpretation of various kinds of imagery used are given.

Gelnett, R. H.↗
NASA NTRS1977

Load and stability measurements on a soft-inplane rotor system incorporating elastomeric lead-lag dampers

An experimental investigation was conducted of the dynamic response and inplane stability associated with a new soft-inplane helicopter rotor. The unique feature of this rotor was the use of an internal elastomeric damper to restrain the blade inplane motion about the lead-lag hinge. The properties of the elastomer were selected to provide both a nominal first inplane frequency ratio of 0.65 and sufficient damping to eliminate the need for additional external damping sources to prevent ground resonance on a typical fuselage structure. For this investigation a 1/5-scale aeroelastic model was used to represent the rotor. The four-blade model had a diameter of 3.05 m (10 ft) and a solidity of 0.103. The first out-of-plane frequency ratio was 1.06. The model was tested in hover and in forward flight up to an advance ratio of 0.45. At each forward speed the rotor lift was varied up to simulated maneuver conditions. The measured rotor loads and response were within acceptable limits, and no adverse response qualities were observed. Moderate out-of-plane hub moments were measured, even for zero lift, to indicate the beneficial control power available for this design. Blade inplane stability testing indicated that the rotor system damping remained at moderate levels throughout the operating envelope.

Weller, W. H.↗
NASA NTRS1981

Exploration for fractured petroleum reservoirs using radar/Landsat merge combinations

Since fractures are commonly propagated upward and reflected at the earth's surface as subtle linears, detection of these surface features is extremely important in many phases of petroleum exploration and development. To document the usefulness of microwave analysis for petroleum exploration, the Arkansas part of the Arkoma basin is selected as a prime test site. The research plan involves comparing the aircraft microwave imagery and Landsat imagery in an area where significant subsurface borehole geophysical data are available. In the northern Arkoma basin, a positive correlation between the number of linears in a given area and production from cherty carbonate strata is found. In the southern part of the basin, little relationship is discernible between surface structure and gas production, and no correlation is found between gas productivity and linear proximity or linear density as determined from remote sensor data.

Macdonald, H.↗
NASA NTRS1984

A study of the variability of ocean currents in the northwestern Atlantic using satellite altimetry

Altimeter data obtained from GEOS-3 during the three year period 1975-78 for a region of the western North Atlantic which includes a portion of the Gulf Stream system and part of the open ocean area of the subtropical gyre are analyzed by a new technique which utilizes all the points along the satellite tracks. The physical phenomenon studied are the time-variable but almost geostrophic currents, or mesoscale eddies, so that geoid errors contaminate the scientific signal minimally and the dynamical interpretation is direct. Results presented include the spatial distribution of geostrophic eddy kinetic energy and examples of a synoptic map of the eddy field (April 1977) and of a time series at a point. These results are compared to and synthesized with a diverse and select set of existing measurements and observations obtained in situ by a variety of instrumental techniques. The agreement is generally good, and the altimeter data analyzed provides new information on features in the map of mean eddy kinetic energy. The implications are that satellite altimetry will serve as a powerful quantitative tool in eddy current research and that even presently archived data contains further useful scientific information.

Robinson, A. R.↗
NASA NTRS1987

Modified independent modal space control method for active control of flexible systems

A modified independent modal space control (MIMSC) method is developed for designing active vibration control systems for large flexible structures. The method accounts for the interaction between the controlled and residual modes. It incorporates also optimal placement procedures for selecting the optimal locations of the actuators in the structure in order to minimize the structural vibrations as well as the actuation energy. The MIMSC method relies on an important feature which is based on time sharing of a small number of actuators, in the modal space, to control effectively a large number of modes. Numerical examples are presented to illustrate the application of the method to generic flexible systems. The results obtained suggest the potential of the devised method in designing efficient active control systems for large flexible structures.

Baz, A.↗
NASA NTRS1985

Creep-fatigue behavior of NiCoCrAlY coated PWA 1480

This study of high-temperature fatigue and creep-fatigue behavior is part of a program to identify the basic features of the effects of temperature, creep, fatigue, and environment on the behavior of a single crystal superalloy, a bulk coating alloy, and a coated alloy system. A system was selected which has had considerable production experience: the Ni-base superalloy, PWA 1480, and the NiCoCrAlY coating, PWA 276. Isothermal behavior was studied first. A series of fatigue and creep fatigue tests of the types commonly designated as pp, cp, pc and cc were conducted. These tests were conducted at various constant total strain ranges. The creep-fatigue cycles employed constant stress dwells at the maximum and/or minimum load. Test results are given.

Miner, R. V.↗
NASA NTRS1987

Long term orbital storage of cryogenic propellants for advanced space transportation missions

A comprehensive study has developed the major features of a large capacity orbital propellant depot for the space-based, cryogenic OTV. The study has treated both the Dual-Keel Space Station and co-orbiting platforms as the accommodations base for the propellant storage facilities, and trades have examined both tethered and hard-docked options. Five tank set concepts were developed for storing the propellants, and along with layout options for the station and platform, were evaluated from the standpoints of servicing, propellant delivery, boiloff, micrometeoroid/debris shielding, development requirements, and cost. These trades led to the recommendation that an all-passive storage concept be considered for the platform and an actively refrigerated concept providing for reliquefaction of all boiloff be considered for the Space Station. The tank sets are modular, each storing up to 45,400 kg of LO2/LH2, and employ many advanced features to provide for microgravity fluid management and to limit boiloff. The features include such technologies as zero-gravity mass gauging, total communication capillary liquid acquisition devices, autogenous pressurization, thermodynamic vent systems, thick multilayer insulation, vapor-cooled shields, solar-selective coatings, advanced micrometeoroid/debris protection systems, and long-lived cryogenic refrigeration systems.

Schuster, John R.↗
NASA NTRS1988

Modified independent modal space control method for active control of flexible systems

A modified independent modal space control (MIMSC) method is developed for designing active vibration control systems for large flexible structures. The method accounts for the interaction between the controlled and residual modes. It incorporates also optimal placement procedures for selecting the optimal locations of the actuators in the structure in order to minimize the structural vibrations as well as the actuation energy. The MIMSC method relies on an important feature which is based on time sharing of a small number of actuators, in the modal space, to control effectively a large number of modes. Numerical examples are presented to illustrate the application of the method to generic flexible systems. The results obtained suggest the potential of the devised method in designing efficient active control systems for large flexible structures.

Baz, A.↗
NASA NTRS1989

Modified independent modal space control method for active control of flexible systems

A modified independent modal space control (MIMSC) method is developed for designing active vibration control systems for large flexible structures. The method accounts for the interaction between the controlled and residual modes. It incorporates also optimal placement procedures for selecting the optimal locations of the actuators in the structure in order to minimize the structural vibrations as well as the actuation energy. The MIMSC method relies on an important feature which is based on time sharing of a small number of actuators, in the modal space, to control effectively a large number of modes. Numerical examples are presented to illustrate the application of the method to generic flexible systems. The results obtained suggest the potential of the devised method in designing efficient active control systems for large flexible structures.

Baz, A.↗