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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Imaging Analysis of the Hard X-Ray Telescope ProtoEXIST2 and New Techniques for High-Resolution Coded-Aperture Telescopes

Wide-field (greater than or approximately equal to 100 degrees squared) hard X-ray coded-aperture telescopes with high angular resolution (greater than or approximately equal to 2 minutes) will enable a wide range of time domain astrophysics. For instance, transient sources such as gamma-ray bursts can be precisely localized without the assistance of secondary focusing X-ray telescopes to enable rapid followup studies. On the other hand, high angular resolution in coded-aperture imaging introduces a new challenge in handling the systematic uncertainty: the average photon count per pixel is often too small to establish a proper background pattern or model the systematic uncertainty in a timescale where the model remains invariant. We introduce two new techniques to improve detection sensitivity, which are designed for, but not limited to, a high-resolution coded-aperture system: a self-background modeling scheme which utilizes continuous scan or dithering operations, and a Poisson-statistics based probabilistic approach to evaluate the significance of source detection without subtraction in handling the background. We illustrate these new imaging analysis techniques in high resolution coded-aperture telescope using the data acquired by the wide-field hard X-ray telescope ProtoEXIST2 during a high-altitude balloon flight in fall 2012. We review the imaging sensitivity of ProtoEXIST2 during the flight, and demonstrate the performance of the new techniques using our balloon flight data in comparison with a simulated ideal Poisson background.

balloons - instrumentation: detectors - techniques↗
NASA NTRS2016

First-Principles Modeling of IAT-Driven Anomalous Resistivity in Hollow Cathode Discharges II: Numerical Simulations and Comparisons with Experiments

We present a model that quantifies the magnitude of the ion-acoustic turbulence (IAT) in the plume of hollow cathodes and its effect on the resistivity and ion heating. The model takes the form of a partial differential equation (PDE) that can be solved concurrently with the equations of motion for a partially ionized plasma already included in our numerical code for the simulation of the plasma discharge in hollow cathodes, OrCa2D. We also determine that self-induced magnetic fields are not negligible in hollow cathodes operating at large discharge currents and implement in our code Ampere’s law and modifications to Ohm’s law that account for this effect. Numerical simulations that employed these models show large improvements in our agreement with experimental measurements with respect to a previous model, which assumed complete saturation of the IAT and did not account for the growth stage of the waves. In particular, the model is able to accurately predict the location and magnitude of the maximum resitivity to the electron current along the cathode centerline.

Lopez Ortega, Alejandro↗
NASA NTRSDate not supplied

KNaCK-SLAM: Kinematic Navigation and Cartography Knapsack Velocity-aided LiDAR Inertial Simultaneous Localization and Mapping (SLAM)

As manned missions return to the Moon and continue on to Mars in the near future, surface navigation and mapping in extremely low solar illumination and unstructured environments without navigation aids like Global Navigation Satellite Systems (GNSS) becomes more important than even. This work explores the use of LiDAR-based Simultaneous Localization and Mapping (SLAM) to solve those problems. A LiDAR-based SLAM system be deployed as a self-contained instrument independent of external sensor inputs, and can operate in unlit environments where Vision-based SLAM system are inoperable. Furthermore, the advent of chip-scale frequency modulated continuous wave (FMCW) LiDAR technology provides Doppler-velocity information for each sensed point in the scene, which can be used to further constrain localization error in the SLAM front-end. Here we discuss the development of SLAM algorithm that makes use of the unique velocity and range sensing capabilities of FMCW-LiDAR based sensors for rover and kinematic (i.e. person-mounted) mobile navigation and terrain mapping applications for surface exploration and scientific investigations.

Kyle Miller↗
DOE OSTI2017

Toward biologically inspired self healing digital embedded devices: BIO-SymPle - 388

One of the more interesting concepts being postulated for next gen power plants, is the notion of highly resilient and survivable I and C systems. While resilience and survivability are 'cross system attributes', resilience and robustness will rely on highly robust and fault resilient devices as a foundation. This paper presents a new self-healing digital I and C architecture inspired by the operation of two biological concepts: human immune system and embryonic stem cells. The purpose of this research is look at different bio-inspired paradigms for organizing system functions so that they become inherently resilient due to device organization and behaviors. Our current proposed approach (called BIO-SymPle) is organized in two levels: critical service layer, which is providing the intended service of critical application, and healing layer, that supervises the operation of all repair mechanisms. To facilitate coordination, organized behavior among cells we employ network-based topology structures which is comprised of four active cells, four pre-generated redundant cells, and one embryonic stem cell. Collectively, the ensemble represents the building block that executes the local functionality based on the expression for DNA genetic codes stored inside each cell. The four bio-operational active cells are protected by their neighboring spare cells that imitate how white blood cells are distributed around the antigens in their locations. Ultimately, the proposed multi-layer architecture is able to cover a significant number of coincident faults and we believe architectures like BIO-SymPLe can positively impact the next generation digital I and C system. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

Blockchain-based decentralized computing

An exemplary blockchain-based decentralized computing system and method are disclosed for industrial analytics applications. The exemplary system and method leverage blockchain technology to deliver and execute privacy-preserving decentralized predictive analytics, machine learning, and optimization operations for various industrial applications using a set of self-contained analytics block smart contracts that can be readily utilized and in analytics applications to deploy across multiple sites.

Ramanan, Paritosh P.↗
NASA NTRS1973

A study of the dynamic tire properties over a range of tire constructions

The dynamic properties of four model aircraft tires of various construction were evaluated experimentally and compared with available theory. The experimental investigation consisted of measuring the cornering force and the self-aligning torque developed by the tires undergoing sinusoidal steering inputs while operating on a small scale, road-wheel tire testing apparatus. The force and moment data from the different tires are compared with both finite- and point-contact patch string theory predictions. In general, agreement between finite contact patch theory and experimental observation is good. A modified string theory is also presented in which coefficients for cornering force and self-aligning torque are determined separately. This theory improves the correspondence between the experimental and analytical data, particularly on tires with relatively high self-aligning torques.

Nybakken, G. H.↗
DOE OSTI2017

Quantum critical point revisited by dynamical mean-field theory

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1994

State-space self-tuner for on-line adaptive control

Dynamic systems, such as flight vehicles, satellites and space stations, operating in real environments, constantly face parameter and/or structural variations owing to nonlinear behavior of actuators, failure of sensors, changes in operating conditions, disturbances acting on the system, etc. In the past three decades, adaptive control has been shown to be effective in dealing with dynamic systems in the presence of parameter uncertainties, structural perturbations, random disturbances and environmental variations. Among the existing adaptive control methodologies, the state-space self-tuning control methods, initially proposed by us, are shown to be effective in designing advanced adaptive controllers for multivariable systems. In our approaches, we have embedded the standard Kalman state-estimation algorithm into an online parameter estimation algorithm. Thus, the advanced state-feedback controllers can be easily established for digital adaptive control of continuous-time stochastic multivariable systems. A state-space self-tuner for a general multivariable stochastic system has been developed and successfully applied to the space station for on-line adaptive control. Also, a technique for multistage design of an optimal momentum management controller for the space station has been developed and reported in. Moreover, we have successfully developed various digital redesign techniques which can convert a continuous-time controller to an equivalent digital controller. As a result, the expensive and unreliable continuous-time controller can be implemented using low-cost and high performance microprocessors. Recently, we have developed a new hybrid state-space self tuner using a new dual-rate sampling scheme for on-line adaptive control of continuous-time uncertain systems.

Shieh, L. S.↗
NASA NTRS2011

Lightweight Magnetic Cooler With a Reversible Circulator

A design of a highly efficient and lightweight space magnetic cooler has been developed that can continuously provide remote/distributed cooling at temperatures in the range of 2 K with a heat sink at about 15 K. The innovative design uses a cryogenic circulator that enables the cooler to operate at a high cycle frequency to achieve a large cooling capacity. The ability to provide remote/distributed cooling not only allows flexible integration with a payload and spacecraft, but also reduces the mass of the magnetic shields needed. The active magnetic regenerative refrigerator (AMRR) system is shown in the figure. This design mainly consists of two identical magnetic regenerators surrounded by their superconducting magnets and a reversible circulator. Each regenerator also has a heat exchanger at its warm end to reject the magnetization heat to the heat sink, and the two regenerators share a cold-end heat exchanger to absorb heat from a cooling target. The circulator controls the flow direction, which cycles in concert with the magnetic fields, to facilitate heat transfer. Helium enters the hot end of the demagnetized column, is cooled by the refrigerant, and passes into the cold-end heat exchanger to absorb heat. The helium then enters the cold end of the magnetized column, absorbing heat from the refrigerant, and enters the hot-end heat exchanger to reject the magnetization heat. The efficient heat transfer in the AMRR allows the system to operate at a relatively short cycle period to achieve a large cooling power. The key mechanical components in the magnetic cooler are the reversible circulator and the magnetic regenerators. The circulator uses non-contacting, self-acting gas bearings and clearance seals to achieve long life and vibration- free operation. There are no valves or mechanical wear in this circulator, so the reliability is predicted to be very high. The magnetic regenerator employs a structured bed configuration. The core consists of a stack of thin GGG disks alternating with thin polymer insulating films. The structured bed reduces flow resistance in the regenerator and therefore the pumping work by the cryogenic circulator. This magnetic cooler will enable cryogenic detectors for sensing infrared, x-ray, gamma-ray, and submillimeter radiation in future science satellites, as well as the detector systems in the Constellation-X (Con-X) and the Single Aperture Far-Infrared observatory (SAFIR). Scientific ap p - lica tions for this innovation include cooling for x-ray micro calorimeter spectrometers used for microanalysis, cryogenic particle detectors, and superconducting tunnel junction de tectors for biomolecule mass spectrometry. The cooler can be scaled to provide very large cooling capacities at very low temperatures, ideal for liquid helium and liquid hydrogen productions.

Chen, Weibo↗
NASA NTRS1994

RoboLab and virtual environments

A useful adjunct to the manned space station would be a self-contained free-flying laboratory (RoboLab). This laboratory would have a robot operated under telepresence from the space station or ground. Long duration experiments aboard RoboLab could be performed by astronauts or scientists using telepresence to operate equipment and perform experiments. Operating the lab by telepresence would eliminate the need for life support such as food, water and air. The robot would be capable of motion in three dimensions, have binocular vision TV cameras, and two arms with manipulators to simulate hands. The robot would move along a two-dimensional grid and have a rotating, telescoping periscope section for extension in the third dimension. The remote operator would wear a virtual reality type headset to allow the superposition of computer displays over the real-time video of the lab. The operators would wear exoskeleton type arms to facilitate the movement of objects and equipment operation. The combination of video displays, motion, and the exoskeleton arms would provide a high degree of telepresence, especially for novice users such as scientists doing short-term experiments. The RoboLab could be resupplied and samples removed on other space shuttle flights. A self-contained RoboLab module would be designed to fit within the cargo bay of the space shuttle. Different modules could be designed for specific applications, i.e., crystal-growing, medicine, life sciences, chemistry, etc. This paper describes a RoboLab simulation using virtual reality (VR). VR provides an ideal simulation of telepresence before the actual robot and laboratory modules are constructed. The easy simulation of different telepresence designs will produce a highly optimum design before construction rather than the more expensive and time consuming hardware changes afterwards.

Giarratano, Joseph C.↗
NASA NTRS1972

Self-consistent Pauli corrections in Brueckner-Hartree-Fock calculations

A scheme is introduced which makes it feasible to make completely self-consistent Brueckner-Hartree-Fock (BHF) and renormalized BHF calculations for spherical, closed-shell and axially-symmetric deformed nuclei. The usual requirement or orbital self-consistency has been imposed, as well as self-consistency in the starting energies and occupation probabilities. Previously, only approximate forms were used for the Pauli operator. This approximation is removed and a method for making the necessary Pauli corrections to the reaction matrix during the approach to self-consistency is presented. A discussion of the symmetries which reduce the problem to one of manageable proportions is included.

Braley, R. C.↗
NASA NTRS1978

An investigation for the development of an integrated optical data preprocessor

The successful fabrication and demonstration of an integrated optical circuit designed to perform a parallel processing operation by utilizing holographic subtraction to simultaneously compare N analog signal voltages with N predetermined reference voltages is summarized. The device alleviates transmission, storage and processing loads of satellite data systems by performing, at the sensor site, some preprocessing of data taken by remote sensors. Major accomplishments in the fabrication of integrated optics components include: (1) fabrication of the first LiNbO3 waveguide geodesic lens; (2) development of techniques for polishing TIR mirrors on LiNbO3 waveguides; (3) fabrication of high efficiency metal-over-photoresist gratings for waveguide beam splitters; (4) demonstration of high S/N holographic subtraction using waveguide holograms; and (5) development of alignment techniques for fabrication of integrated optics circuits. Important developments made in integrated optics are the discovery and suggested use of holographic self-subtraction in LiNbO3, development of a mathematical description of the operating modes of the preprocessor, and the development of theories for diffraction efficiency and beam quality of two dimensional beam defined gratings.

Verber, C. M.↗
DOE OSTI2017

The effect of fuel staging on the structure and instability characteristics of swirl-stabilized flames in a lean premixed multi-nozzle can combustor

Fuel staging is a commonly used strategy in the operation of gas turbine engines. In multinozzle combustor configurations, this is achieved by varying fuel flow rate to different nozzles. The effect of fuel staging on flame structure and self-excited instabilities is investigated in a research can combustor employing five swirl-stabilized, lean-premixed nozzles. At an operating condition where all nozzles are fueled equally and the combustor undergoes a self-excited instability, fuel staging successfully suppresses the instability: both when overall equivalence ratio is increased by staging as well as when overall equivalence ratio is kept constant while staging. Increased fuel staging changes the distribution of time-averaged heat release rate in the regions where adjacent flames interact and reduces the amplitudes of heat release rate fluctuations in those regions. Increased fuel staging also causes a breakup in the monotonic phase behavior that is characteristic of convective disturbances that travel along a flame. In particular, heat release rate fluctuations in the middle flame and flame–flame interaction region are out-of-phase with those in the outer flames, resulting in a cancelation of the global heat release rate oscillations. The Rayleigh integral distribution within the combustor shows that during a self-excited instability, the regions of highest heat release rate fluctuation are in phase-with the combustor pressure fluctuation. In conclusion, when staging fuel is introduced, these regions fluctuate out-of-phase with the pressure fluctuation, further illustrating that fuel staging suppresses instabilities through a phase cancelation mechanism.

20 FOSSIL-FUELED POWER PLANTS↗
NASA NTRS1999

A Self-Tuning Kalman Filter for Autonomous Navigation using the Global Positioning System (GPS)

Most navigation systems currently operated by NASA are ground-based, and require extensive support to produce accurate results. Recently developed systems that use Kalman filter and GPS data for orbit determination greatly reduce dependency on ground support, and have potential to provide significant economies for NASA spacecraft navigation. These systems, however, still rely on manual tuning from analysts. A sophisticated neuro-fuzzy component fully integrated with the flight navigation system can perform the self-tuning capability for the Kalman filter and help the navigation system recover from estimation errors in real time.

Truong, S. H.↗
NASA NTRS1999

A Self-Tuning Kalman Filter for Autonomous Navigation Using the Global Positioning System (GPS)

Most navigation systems currently operated by NASA are ground-based, and require extensive support to produce accurate results. Recently developed systems that use Kalman filter and GPS (Global Positioning Systems) data for orbit determination greatly reduce dependency on ground support, and have potential to provide significant economies for NASA spacecraft navigation. These systems, however, still rely on manual tuning from analysts. A sophisticated neuro-fuzzy component fully integrated with the flight navigation system can perform the self-tuning capability for the Kalman filter and help the navigation system recover from estimation errors in real time.

Truong, Son H.↗
DOE OSTI2020

A Novel Technique for Pulsed Operation of Magnetrons without Modulation of Cathode Voltage

Modern pulsed superconducting accelerators of megawatt beams require efficient RF sources controllable in phase and power. For each Superconducting RF (SRF) cavity is desirable a separate RF source with power up to hundreds of kW with pulse duration in the millisecond range. The efficiency of the traditional RF sources (klystrons, IOTs, solid-state amplifiers) is lower than that of the magnetrons, while the cost of a unit of RF power is much higher. Therefore the magnetron-based RF sources would significantly reduce the capital and operation costs in comparison with the traditional RF sources. A recently developed an innovative technique makes possible the pulsed generation of magnetrons powered below the self-excitation threshold voltage. This technique does not require pulse modulators to form RF pulses. The magnetron operation in this regime is stable, low noise, controllable in phase and power, and provides higher efficiency than other types of RF power sources. It allows operation in pulsed modes with large duty factor. The developed technique and its experimental verification are considered and discussed.

43 PARTICLE ACCELERATORS↗
NASA NTRSDate not supplied

Data-Centric Operational Design Domain Characterization for Machine Learning-Based Aeronautical Products

We give for Machine Learning (ML)-based aeronautical products, a first rigorous characterization of Operational Design Domains (ODDs). Unlike in other application sectors (such as self-driving road vehicles) where ODD development is scenario-based, our approach is data-centric: we propose the dimensions along which the parameters that define an ODD can be explicitly captured, using a top-down approach starting from system specifications, and a bottom-up approach starting from detailed ML Model (MLM) designs. Then we give a categorization of the data that ML-based applications can encounter in operation, identifying their system-level relevance and impact. Specifically, we discuss how those data categories are useful to determine: (1) the requirements necessary to drive the design of MLMs; (2) the potential effects on the MLM and higher levels of the system hierarchy; (3) the learning assurance processes that may be needed, and (4) system architectural considerations. We illustrate the underlying concepts with an example of an aircraft flight envelope. The approach in this paper is one of the cornerstones of a future process guidance for development and certification/approval of safety-related aeronautical products implementing Artificial Intelligence (AI), currently being developed through aviation industry-based consensus, jointly by the SAE G-34 Committee for AI in aviation, and EUROCAE WG-114 for AI.

Aeronautical products↗
NASA NTRS2011

Self-regulating control of parasitic loads in a fuel cell power system

A fuel cell power system comprises an internal or self-regulating control of a system or device requiring a parasitic load. The internal or self-regulating control utilizes certain components and an interconnection scheme to produce a desirable, variable voltage potential (i.e., power) to a system or device requiring parasitic load in response to varying operating conditions or requirements of an external load that is connected to a primary fuel cell stack of the system. Other embodiments comprise a method of designing such a self-regulated control scheme and a method of operating such a fuel cell power system.

Vasquez, Arturo↗