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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Ultra-Compact Motor Controller

This invention is an electronically commutated brushless motor contro ller that incorporates Hall-array sensing in a small, 42-gram packag e that provides 4096 absolute counts per motor revolution position s ensing. The unit is the size of a miniature hockey puck, and is a 44 -pin male connector that provides many I/O channels, including CANbus , RS-232 communications, general-purpose analog and digital I/O (GPI O), analog and digital Hall inputs, DC power input (18-90 VDC, 0-l0 A), three-phase motor outputs, and a strain gauge amplifier.

Townsend, William T.↗
DOE OSTI2020

Protonic solid-state electrochemical synapse for physical neural networks

Physical neural networks made of analog resistive switching processors are promising platforms for analog computing. State-of-the-art resistive switches rely on either conductive filament formation or phase change. These processes suffer from poor reproducibility or high energy consumption, respectively. Herein, we demonstrate the behavior of an alternative synapse design that relies on a deterministic charge-controlled mechanism, modulated electrochemically in solid-state. The device operates by shuffling the smallest cation, the proton, in a three-terminal configuration. It has a channel of active material, WO 3 . A solid proton reservoir layer, PdH x , also serves as the gate terminal. A proton conducting solid electrolyte separates the channel and the reservoir. By protonation/deprotonation, we modulate the electronic conductivity of the channel over seven orders of magnitude, obtaining a continuum of resistance states. Proton intercalation increases the electronic conductivity of WO 3 by increasing both the carrier density and mobility. This switching mechanism offers low energy dissipation, good reversibility, and high symmetry in programming.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A hybrid coupler for directing quantum light emission with high radiative Purcell enhancement to a dielectric metasurface lens

Quantum photonic technologies such as quantum sensing, metrology, and simulation could be transformatively enabled by the availability of integrated single photon sources with high radiative rates and photon collection efficiencies. We address these challenges for quantum emitters formed from color center defect sites such as those in hexagonal boron nitride, which are promising candidates as single photon sources due to their bright, stable, polarized, and room temperature emission. We report design of a nanophotonic coupler from color center quantum emitters to a dielectric metasurface lens. The coupler is comprised of a hybrid plasmonic–dielectric resonator that achieves a large radiative Purcell enhancement and partial control of far-field radiation. We report radiative Purcell factors up to 285 and photon collection efficiencies up to 89% for a lossless metasurface, applying a continuous hyperboloidal phase-front. Our hybrid plasmonic–dielectric coupler interfacing two nanophotonic elements is a compound optical element, analogous to those found in microscope objective lenses, which combine multiple optical functions into a single component for improved performance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Interaction Effects on the Dynamical Anderson Metal-Insulator Transition Using Kicked Quantum Gases

Understanding the interplay of interaction and disorder in quantum transport poses long-standing scientific challenges for theory and experiment. While highly controlled ultracold atomic platforms combining atomic interactions with spatially disordered lattices have led to remarkable advances, the extension of such controlled studies to phenomena in high-dimensional disordered systems, such as the three-dimensional Anderson metal-insulator transition has been limited. Kicked quantum gases provide an alternate experimental platform that captures the Anderson model in momentum space and features dynamical localization as the analog of Anderson localization. Here, we utilize a momentum space lattice platform using quasiperiodically kicked ultracold atomic gases to experimentally investigate interaction effects on the three-dimensional dynamical Anderson metal-insulator transition. Here, we observe interaction-driven subdiffusion and a divergence of delocalization onset time on approaching the phase boundary. Mean-field numerical simulations show qualitative agreement with experimental observations, but with significant quantitative deviations.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Putting a spin on metamaterials: Mechanical incompatibility as magnetic frustration

Mechanical metamaterials present a promising platform for seemingly impossible mechanics. They often require incompatibility of their elementary building blocks, yet a comprehensive understanding of its role remains elusive. Relying on an analogy to ferromagnetic and antiferromagnetic binary spin interactions, we present a general approach to identify and analyze topological mechanical defects for arbitrary building blocks. We underline differences between two- and three-dimensional metamaterials, and show how topological defects can steer stresses and strains in a controlled and non-trivial manner and can inspire the design of materials with hitherto unknown complex mechanical response.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1977

Life sciences Spacelab Mission Development test 3 (SMD 3) data management report

Development of a permanent data system for SMD tests was studied that would simulate all elements of the shuttle onboard, telemetry, and ground data systems that are involved with spacelab operations. The onboard data system (ODS) and the ground data system (GDS) were utilized. The air-to-ground link was simulated by a hardwired computer-to-computer interface. A patch board system was used on board to select experiment inputs, and the downlink configuration from the ODS was changed by a crew keyboard entry to support each experiment. The ODS provided a CRT display of experiment parameters to enable the crew to monitor experiment performance. An onboard analog system, with recording capability, was installed to handle high rate data and to provide a backup to the digital system. The GDS accomplished engineering unit conversion and limit sensing, and provided realtime parameter display on CRT's in the science monitoring area and the test control area.

Moseley, E. C.↗
NASA NTRS1979

A fast-reacting and versatile optokinetic stimulus pattern by computer graphics with application examples

A computer graphics method for the generation of horizontally moving vertical stripes which serve as stimuli for optokinetic nystagmus is presented. The pattern is generated by the successive addition of a constant in a digital register, leading to its periodic overflow. Digital to analog conversion of the register contents results in a staircase waveform, which is converted into a pattern of vertical lines on a CRT. The addition of any number to the reference buffer shifts all lines uniformly, so that the group velocity of the pattern is easily controlled. The computer controlled display allows an accurate realization of a commanded velocity profile with practically no time delay and facilitates study under conditions of variable feedback. The display software can be easily modified to limit stimulation to a selected area of the moving retina, and the method has been used to simulate central scotomata. It is pointed out that the technique, while more accurate, versatile and responsive than a rotating drum device, may be less useful in experiments requiring a wide field display.

Yasui, S.↗
NASA NTRS1985

Antarctica - Lessons for a Mars exploration program

The history of exploration and the international system of control of Antarctica has often been cited as a paradigm for the exploration of space. The small isolated research stations have been used to model the psychological stresses of future space missions. In addition, the programmatic structure of the U.S. Antarctic Research Program provides several possible analogs to future Mars Programs presently under discussion. These are: (1) Continued presence; (2) Civilian, military and private sector involvement; (3) Scientific activities; (4) Risk assessment and logistical support; (5) Accessibility for non-specialists; (6) Political and strategic motivations; (7) International cooperation/competition. Survival in Antarctica is contingent on advanced technology and the active transport of supplies. The scientific exploration of this remote and barren expanse without, of course, the aid and guidance of indigenous people certainly provides one of the closest analogs available to future science activities on the Martian surface.

Mckay, C. P.↗
NASA NTRS1986

A Fourier transform telescope for sub-arcsecond imaging of X-rays and gamma rays

This paper describes a Fourier transform telescope designed to image solar flare X-rays and gamma rays at energies up to 1 MeV with arcsec resolution. The imaging technique makes use of a bigrid collimator divided into a number of smaller areas called subcollimators. The grids in each subcollimator consist of a set of linear apertures so configured that each subcollimator provides a measurement of a single Fourier component of the angular distribution of the source. The imaging concept is therefore a mathematical analog to aperture synthesis in radio astronomy. For X-ray and gamma-ray astronomy, this approach has significant advantages in terms of relaxed requirements for astronomy, this approach has significant advantages in terms of relaxed requirements for position sensitivity in the detector and for control of grid alignment in the large scale telescope structure. The concept of the Fourier transform telescope will be illustrated with numerical parameters of a version now under study for the Pinhole/Occulter Facility.

Crannell, C. J.↗
NASA NTRS1995

VLF waves in the foreshock

Plasma waves observed in the VLF range upstream of planetary bow shocks not only modify the particle distributions, but also provide important information about the acceleration processes that occur at the bow shock. Electron plasma oscillations observed near the tangent field line in the electron foreshock are generated by electrons reflected at the bow shock through a process that has been referred to as Fast Fermi acceleration. Fast Fermi acceleration is the same as shock-drift acceleration, which is one of the mechanisms by which ions are energized at the shock. We have generated maps of the VLF emissions upstream of the Venus bow shock, using these maps to infer properties of the shock energization processes. We find that the plasma oscillations extend along the field line up to a distance that appears to be controlled by the shock scale size, implying that shock curvature restricsts the flux and energy of reflected electrons. We also find that the ion acoustic waves are observed in the ion foreshock, but at Venus these emissions are not detected near the ULF forshock boundary. Through analogy with terrestrial ion observations, this implies that the ion acoustic waves are not generated by ion beams, but are instead generated by diffuse ion distributions found deep within the ion foreshock. However, since the shock is much smaller at Venus, and there is no magnetosphere, we might expect ion distributions within the ion foreshock to be different than at the Earth. Mapping studies of the terrestrial foreshock similar to those carried out at Venus appear to be necessary to determine if the inferences drawn from Venus data are applicable to other foreshocks.

Strangeway, R. J.↗
NASA NTRS2011

Adaptation of the Electra Radio to Support Multiple Receive Channels

Proposed future Mars missions plan communication between multiple assets (rovers). This paper presents the results of a study carried out to assess the potential adaptation of the Electra radio to a multi-channel transceiver. The basic concept is a Frequency Division multiplexing (FDM) communications scheme wherein different receiver architectures are examined. Options considered include: (1) multiple IF slices, A/D and FPGAs each programmed with an Electra baseband modem; (2) common IF but multiple A/Ds and FPGAs and (3) common IF, single A/D and single or multiple FPGAs programmed to accommodate the FDM signals. These options represent the usual tradeoff between analog and digital complexity. Given the space application, a common IF is preferable; however, multiple users present dynamic range challenges (e.g., near-far constraints) that would favor multiple IF slices (Option 1). Vice versa, with a common IF and multiple A/Ds (Option 2), individual AGC control of the A/Ds would be an important consideration. Option 3 would require a common AGC control strategy and would entail multiple digital down conversion paths within the FPGA. In this paper, both FDM parameters as well as the different Electra design options will be examined. In particular, signal channel spacing as a function of user data rates and transmit powers will be evaluated. In addition, tradeoffs between the different Electra design options will be presented with the ultimate goal of defining an augmented Electra radio architecture for potential future missions.

Time Division multiplexing↗
NASA NTRSDate not supplied

Low Temperature Formation of Carbonaceous Grains from Hydrocarbons and PAHs with the COSmIC Facility

Complex carbon molecules and ions are ubiquitous in space and form the building blocks of the carbonaceous components of cosmic dust grains, ultimately contributing to the formation of planets. We report experimental investigations of the low temperature chemical pathways leading to the formation of cosmic grain analogs from gas phase molecular precursors to better understand the evolution of cosmic carbon. The study of the formation of dust is essential to understand and to quantify the budget of extraterrestrial organic molecules. Although dust plays an important role in the evolution of interstellar chemistry and in the formation of organic molecules, little is known on the formation and destruction processes of carbonaceous dust. The experiments were performed using the Cosmic Simulation Chamber (COSmIC) to generate and characterize solid grains formed from gas phase precursors under controlled conditions representative of astrophysical environments [1]. Using COSmIC, it is possible to investigate the evolution of cosmic carbon from the formation of neutral and ionized hydrocarbons and PAHs in the gas phase [2], to solid carbon grains [3, 4, 5]. This is achieved by using a pulsed slit discharge nozzle to produce an adiabatic jet expansion and cool down Ar-hydrocarbon and PAH gas mixtures to astrophysically relevant temperature before inducing chemistry by generating a plasma discharge in the stream of the expansion. This plasma induced chemistry results in the formation of complex molecules and solid particles, analogs of cosmic grains in situ in the plasma expansion (i.e., without wall effects) that are carried by the accelerated gas in the expansion, and collected on substrates placed a few centimeters downstream of the electrodes. The results of a preliminary solid phase ex-situ analysis of cosmic grain analogs produced from a series of gas mixtures including hydrocarbons such as CH4 and C2H2 [3] and PAHs [4, 5] found in circumstellar ejecta of late C stars will be discussed. SEM imaging was used to provide insight on the impact of the precursors on the morphology and growth structure of the grains produced [3]. Laser desorption mass spectrometry was used to identify the molecules making up the main structures within the condensed grains [4] while X-ray irradiation and X-ray photoemission spectroscopy were used to investigate the impact the impact of stellar X-rays on cosmic dust.

Carbonaceous Grains↗
DOE OSTI2022

Shape‐Dependent Multi‐Weight Magnetic Artificial Synapses for Neuromorphic Computing

Abstract In neuromorphic computing, artificial synapses provide a multi‐weight (MW) conductance state that is set based on inputs from neurons, analogous to the brain. Herein, artificial synapses based on magnetic materials that use a magnetic tunnel junction (MTJ) and a magnetic domain wall (DW) are explored. By fabricating lithographic notches in a DW track underneath a single MTJ, 3–5 stable resistance states that can be repeatably controlled electrically using spin‐orbit torque are achieved. The effect of geometry on the synapse behavior is explored, showing that a trapezoidal device has asymmetric weight updates with high controllability, while a rectangular device has higher stochasticity, but with stable resistance levels. The device data is input into neuromorphic computing simulators to show the usefulness of application‐specific synaptic functions. Implementing an artificial neural network (NN) applied to streamed Fashion‐MNIST data, the trapezoidal magnetic synapse can be used as a metaplastic function for efficient online learning. Implementing a convolutional NN for CIFAR‐100 image recognition, the rectangular magnetic synapse achieves near‐ideal inference accuracy, due to the stability of its resistance levels. This work shows MW magnetic synapses are a feasible technology for neuromorphic computing and provides design guidelines for emerging artificial synapse technologies.

Leonard, Thomas↗
NASA NTRS1987

A computer controlled signal preprocessor for laser fringe anemometer applications

The operation of most commercially available laser fringe anemometer (LFA) counter-processors assumes that adjustments are made to the signal processing independent of the computer used for reducing the data acquired. Not only does the researcher desire a record of these parameters attached to the data acquired, but changes in flow conditions generally require that these settings be changed to improve data quality. Because of this limitation, on-line modification of the data acquisition parameters can be difficult and time consuming. A computer-controlled signal preprocessor has been developed which makes possible this optimization of the photomultiplier signal as a normal part of the data acquisition process. It allows computer control of the filter selection, signal gain, and photo-multiplier voltage. The raw signal from the photomultiplier tube is input to the preprocessor which, under the control of a digital computer, filters the signal and amplifies it to an acceptable level. The counter-processor used at Lewis Research Center generates the particle interarrival times, as well as the time-of-flight of the particle through the probe volume. The signal preprocessor allows computer control of the acquisition of these data.Through the preprocessor, the computer also can control the hand shaking signals for the interface between itself and the counter-processor. Finally, the signal preprocessor splits the pedestal from the signal before filtering, and monitors the photo-multiplier dc current, sends a signal proportional to this current to the computer through an analog to digital converter, and provides an alarm if the current exceeds a predefined maximum. Complete drawings and explanations are provided in the text as well as a sample interface program for use with the data acquisition software.

Oberle, Lawrence G.↗
NASA NTRS1998

Performance of the CELSS Antarctic Analog Project (CAAP) Crop Production System

Regenerative life support systems potentially offer a level of self-sufficiency and a concomitant decrease in logistics and associated costs in support of space exploration and habitation missions. Current state-of-the-art in plant based, regenerative life support requires resources in excess of resource allocations proposed for candidate mission scenarios. Feasibility thresholds have been identified for candidate exploration missions. The goal of this paper is to review recent advances in performance achieved in the CELSS Antarctic Analog Project (CAAP) in light of likely resource constraints. A prototype CAAP crop production chamber has been constructed and operated at the Ames Research Center. The chamber includes a number of unique hardware and software components focused on attempts to increase production efficiency, increase energy efficiency, and control the flow of energy and mass through the system to achieve enhanced performance efficiency. Both single crop, batch production, and continuous cultivation of mixed crops Product ion scenarios have been completed. The crop productivity as well as engineering performance of the chamber will be described. For each scenario, energy required and partitioned for lighting, cooling, pumps, fans, etc. is quantified. Crop production and the resulting lighting efficiency and energy conversion efficiencies are presented. In the mixed-crop scenario, with up to 25 different crops under cultivation, 17 sq m of crop area provided a mean of 515 g edible biomass per day (83% of the approximately 620 g required for one person). Lighting efficiency (moles on photons kWh-1) approached 4 and the conversion efficiency of light energy to biomass was greatly enhanced compared with conventional growing systems. Engineering and biological performance achieved place plant-based life support systems at the threshold of feasibility.

Bubenheim, David L.↗
NASA NTRS2005

Faster Evolution of More Multifunctional Logic Circuits

A modification in a method of automated evolutionary synthesis of voltage-controlled multifunctional logic circuits makes it possible to synthesize more circuits in less time. Prior to the modification, the computations for synthesizing a four-function logic circuit by this method took about 10 hours. Using the method as modified, it is possible to synthesize a six-function circuit in less than half an hour. The concepts of automated evolutionary synthesis and voltage-controlled multifunctional logic circuits were described in a number of prior NASA Tech Briefs articles. To recapitulate: A circuit is designed to perform one of several different logic functions, depending on the value of an applied control voltage. The circuit design is synthesized following an automated evolutionary approach that is so named because it is modeled partly after the repetitive trial-and-error process of biological evolution. In this process, random populations of integer strings that encode electronic circuits play a role analogous to that of chromosomes. An evolved circuit is tested by computational simulation (prior to testing in real hardware to verify a final design). Then, in a fitness-evaluation step, responses of the circuit are compared with specifications of target responses and circuits are ranked according to how close they come to satisfying specifications. The results of the evaluation provide guidance for refining designs through further iteration.

Stoica, Adrian↗
NASA NTRSDate not supplied

ISAAC: An Integrated System for Autonomous and Adaptive Caretaking

The Integrated System for Autonomous and Adaptive Caretaking (ISAAC) project is developing technology for autonomous caretaking of spacecraft, primarily during uncrewed mission phases. ISAAC aims to integrate autonomous intra-vehicular robots (IVR) with spacecraft infrastructure (power, life support, etc.) and ground control. It focuses on capabilities required for NASA’s Gateway cis-lunar outpost that also apply to human missions to Mars and beyond. Its development strategy is to test using existing IVR on the ISS (the Astrobee free-flyer and Robonaut dextrous manipulator) as an analog for future IVR on Gateway.

Trey Smith↗
NASA NTRS2011

Microgravity-Enhanced Stem Cell Selection

Stem cells, both embryonic and adult, promise to revolutionize the practice of medicine in the future. In order to realize this potential, a number of hurdles must be overcome. Most importantly, the signaling mechanisms necessary to control the differentiation of stem cells into tissues of interest remain to be elucidated, and much of the present research on stem cells is focused on this goal. Nevertheless, it will also be essential to achieve large-scale expansion and, in many cases, assemble cells in 3D as transplantable tissues. To this end, microgravity analog bioreactors can play a significant role. Microgravity bioreactors were originally conceived as a tool to study the cellular responses to microgravity. However, the technology can address some of the shortcomings of conventional cell culture systems; namely, the deficiency of mass transport in static culture and high mechanical shear forces in stirred systems. Unexpectedly, the conditions created in the vessel were ideal for 3D cell culture. Recently, investigators have demonstrated the capability of the microgravity bioreactors to expand hematopoietic stem cells compared to static culture, and facilitate the differentiation of umbilical cord stem cells into 3D liver aggregates. Stem cells are capable of differentiating into functional cells. However, there are no reliable methods to induce the stem cells to form specific cells or to gain enough cells for transplantation, which limits their application in clinical therapy. The aim of this study is to select the best experimental setup to reach high proliferation levels by culturing these cells in a microgravity-based bioreactor. In typical cell culture, the cells sediment to the bottom surface of their container and propagate as a one-cell-layer sheet. Prevention of such sedimentation affords the freedom for self-assembly and the propagation of 3D tissue arrays. Suspension of cells is easily achievable using stirred technologies. Unfortunately, in conventional bioreactors, stirring invokes deleterious forces that disrupt cell aggregation and results in cell death. First-generation rotating bioreactors provided rotation on the horizontal axis, which resulted in the suspension of cells without stirring, thus providing a suitable environment to propagate cells without sedimentation to a surface. The rotating wall bioreactors did not provide a way to remove air bubbles that were causing shear and disrupting 3D cultures. Johnson Space Center successfully engineered the hydrofocusing bioreactor (HFB) that resolved the problem of removing the air bubbles from the fluid medium of NASA's rotating-wall space bioreactors. The HFB uses the principle of hydrodynamic focusing that simultaneously produces a low-shear fluid culture environment and a variable hydrofocusing force that can control the movement, location, and removal of suspended cells, tissues, and air bubbles from the bioreactor. The HFB is a rotating, domeshaped cell culture vessel with a centrally located sampling port and an internal viscous spinner. The vessel and spinner can rotate at different speeds either in the same or opposite directions. Rotation of the vessel and viscous interaction at the spinner generate a hydrofocusing force. Adjusting the differential rotation rate between vessel and spinner controls the magnitude of the force.

Claudio, Pier Paolo↗