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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Qudit Gate Decomposition Dependence for Lattice Gauge Theories

In this work, we investigate the effect of decomposition basis on primitive qudit gates on superconducting radio-frequency cavity-based quantum computers with applications to lattice gauge theory. Three approaches are tested: SNAP & Displacement gates, ECD & single-qubit rotations $R(\theta,\phi)$, and optimal pulse control. For all three decompositions, implementing the necessary sequence of rotations concurrently rather then sequentially can reduce the primitive gate run time. The number of blocks required for the faster ECD &$R_p(\theta)$ is found to scale $\mathcal{O}(d^2)$, while slower SNAP & Displacement set scales at worst $\mathcal{O}(d)$. For qudits with $d<10$, the resulting gate times for the decompositions is similar, but strongly-dependent on experimental design choices. Optimal control can outperforms both decompositions for small $d$ by a factor of 2-12 at the cost of higher classical resources. Lastly, we find that SNAP & Displacement are slightly more robust to a simplified noise model.

Kürkçüoglu, Doga Murat↗
NASA NTRS2016

Novel Photon-Counting Detectors for Free-Space Communication

We present performance data for novel photon counting detectors for free space optical communication. NASA GSFC is testing the performance of three novel photon counting detectors 1) a 2x8 mercury cadmium telluride avalanche array made by DRS Inc. 2) a commercial 2880 silicon avalanche photodiode array and 3) a prototype resonant cavity silicon avalanche photodiode array. We will present and compare dark count, photon detection efficiency, wavelength response and communication performance data for these detectors. We discuss system wavelength trades and architectures for optimizing overall communication link sensitivity, data rate and cost performance. The HgCdTe APD array has photon detection efficiencies of greater than 50 were routinely demonstrated across 5 arrays, with one array reaching a maximum PDE of 70. High resolution pixel-surface spot scans were performed and the junction diameters of the diodes were measured. The junction diameter was decreased from 31 m to 25 m resulting in a 2x increase in e-APD gain from 470 on the 2010 array to 1100 on the array delivered to NASA GSFC. Mean single photon SNRs of over 12 were demonstrated at excess noise factors of 1.2-1.3.The commercial silicon APD array has a fast output with rise times of 300ps and pulse widths of 600ps. Received and filtered signals from the entire array are multiplexed onto this single fast output. The prototype resonant cavity silicon APD array is being developed for use at 1 micron wavelength.

Photons↗
NASA NTRS1976

Georgia Institute of Technology research on the Gas Core Actinide Transmutation Reactor (GCATR)

The program reviewed is a study of the feasibility, design, and optimization of the GCATR. The program is designed to take advantage of initial results and to continue work carried out on the Gas Core Breeder Reactor. The program complements NASA's program of developing UF6 fueled cavity reactors for power, nuclear pumped lasers, and other advanced technology applications. The program comprises: (1) General Studies--Parametric survey calculations performed to examine the effects of reactor spectrum and flux level on the actinide transmutation for GCATR conditions. The sensitivity of the results to neutron cross sections are to be assessed. Specifically, the parametric calculations of the actinide transmutation are to include the mass, isotope composition, fission and capture rates, reactivity effects, and neutron activity of recycled actinides. (2) GCATR Design Studies--This task is a major thrust of the proposed research program. Several subtasks are considered: optimization criteria studies of the blanket and fuel reprocessing, the actinide insertion and recirculation system, and the system integration. A brief review of the background of the GCATR and ongoing research is presented.

Clement, J. D.↗
NASA NTRS1973

Nuclear characteristics of a fissioning uranium plasma test reactor with light-water cooling

An analytical study was performed to determine a design configuration for a cavity test reactor. Test section criteria were that an average flux of 10 to the 15th power neutrons/sq cm/sec (E less than or equal to 0.12 eV) be supplied to a 61-cm-diameter spherical cavity at 200-atm pressure. Design objectives were to minimize required driver power, to use existing fuel-element technology, and to obtain fuel-element life of 10 to 100 full-power hours. Parameter calculations were made on moderator region size and material, driver fuel arrangement, control system, and structure in order to determine a feasible configuration. Although not optimized, a configuration was selected which would meet design criteria. The driver fuel region was a cylindrical annular region, one element thick, of 33 MTR-type H2O-cooled elements (Al-U fuel plate configuration), each 101 cm long. The region between the spherical test cavity and the cylindrical driver fuel region was Be (10 vol. % H2O coolant) with a midplane dimension of 8 cm. Exterior to the driver fuel, the 25-cm-thick cylindrical and axial reflectors were also Be with 10 vol. % H2O coolant. The entire reactor was contained in a 10-cm-thick steel pressure vessel, and the 200-atm cavity pressure was equalized throughout the driver reactor. Fuel-element life was 50 hr at the required driver power of 200 MW. Reactor control would be achieved with rotating poison drums located in the cylindrical reflector region. A control range of about 18 percent delta k/k was required for reactor operation.

Whitmarsh, C. L., Jr.↗
NASA NTRS1992

CFD analysis to optimize a design modification of BSMT

The Bearings, Seals and Materials Tester (BSMT) is a test article being used at MSFC to evaluate the performance of conventional rolling contact bearings. Pressure differentials between the BSMT inlet and exit cavities are found to cause large parasitic axial loads on the bearing-carrier walls. These parasitic loads, besides being detrimental to the life of bearings, make the testing and evaluation of bearing performance very difficult, and need to be eliminated if at all possible. The objectives of this study are to estimate the hydrodynamic loads on the bearings and to recommend feasible design modifications for BSMT to eliminate the parasitic loads. Three-dimensional computational analyses of inlet and exit cavities in their baseline configuration were performed with REFLEQS which is an advanced finite-volume Navier-Stokes code. Computations were performed with and without a 1/4 inch diameter temperature probe included in each of the cavities. The results of the analyses indicate that the temperature probes substantially alter the flow field and reduce the pressure drop/rise in the cavities. The overall pressure drop across the tester compares quite well with the measurements.

Ratcliff, Mark↗
NASA NTRS1979

Application of a finite element method for computing grazing incidence wave structure in an impedance tube - Comparison with experiment

The acoustic performance of a liner specimen, in a grazing incidence impedance tube, is analyzed using a finite element method. The liner specimen was designed to be a locally reacting, two-degree-of-freedom type with the resistance and reactance provided by perforated facesheets and compartmented cavities. Measured and calculated wave structures are compared for both normal and grazing incidence from 0.3 to 1.2 kHz. A finite element algorithm was incorporated into an optimization loop in order to predict liner grazing incidence impedance from measured SWR and null position data. Results suggest that extended reaction effects may have been responsible for differences between normal and grazing incidence impedance estimates.

Lester, H. C.↗
NASA NTRS1995

Apparatus for diffusion controlled dialysis under microgravity conditions

Apparatus for implementing crystal growth by allowing mixing of solutions under microgravity conditions includes a housing within which a number of pairs of chambers are formed. The chambers of each pair are aligned and a rotary valve is positioned between the chambers of each pair. When the valve is in a first position one chamber of each pair may communicate with the other chamber. A separate valve is provided for each pair of chambers so that each pair of chambers may be activated independently of the others and sequentially at selected intervals. Protein solution may be located within a small cavity in a cap which closes one of the chambers of a pair, and the cavity in the cap is closed by a dialysis membrane. The length of certain pairs of chambers may differ from the length of other pairs of chambers to optimize conditions for various dialysis productions, and wicking material may be incorporated into selected chambers for controlling the critical approach to supersaturation.

Carter, Daniel C.↗
NASA NTRSDate not supplied

Engineered Interfaces in Extruded Polyphenylsulfone- Boron Nitride Composite Insulation

Improving matrix-filler interactions is critical for optimizing dielectric performance in composite insulation; however, the technique used to an introduce inorganic filler into organic matrices varies in its ability to satisfactorily reduce the size of cavities and interfaces. This study reports how sample rheology influenced the dielectric performance and thermal conductivity of extruded polyphenylsulfone (PPSU) – hexagonal boron nitride (BN) composite insulation through changing the BN incorporation strategy. Depending on the technique used to introduce BN into the host matrix, the low melt viscosity, torque, and melt viscosity temperature of the polymer were reduced, enabling better mixing, heat transfer, and smaller voids. This corresponded to an increase in dielectric strength compared to other formulations; however, the thermal conductivity shifted further away from the thermal conductivity target of 1 W/m·K target, which was an indication of a larger separation distance between the particles in samples with smaller interfaces. A trade-off between dielectric strength and thermal conductivity may exist when maximizing thermal conduction without sacrificing dielectric strength.

polyphenylsulfone↗
NASA NTRSDate not supplied

Engineered Interfaces in Extruded Polyphenylsulfone-Boron Nitride Composite Insulation

Improving matrix-filler interactions is critical for optimizing dielectric performance in composite insulation; however, the technique used to introduce inorganic fillers into an organic matrix varies in its ability to satisfactorily reduce the size of cavities and interfaces. This study reports effects from changing the filler incorporation strategy on the rheology, dielectric performance and thermal conductivity of extruded polyphenylsulfone (PPSU) – hexagonal boron nitride (hBN) composite insulation. Depending on the technique used to introduce BN into the host matrix, the viscosity, torque, and melt viscosity temperature of the polymer were reduced, enabling better mixing, heat transfer, and smaller voids. This corresponded to an increase in dielectric strength compared to other formulations at either a similar or lower filler loading. On the other hand, the thermal conductivity in these specimens shifted further away from the thermal conductivity target of 1 W/m·K, which was an indication of a larger separation distance between the particles in samples with smaller interfaces. A trade-off between dielectric strength and thermal conductivity may exist when maximizing thermal conduction without sacrificing dielectric strength.

Polyphenylsulfone↗
NASA NTRS2009

2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed in NASA Langley Research Center. This laser system is capable of making a vertical profiling of CO2 from ground and column measurement of CO2 from air and space-borne platform. The transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of ~50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. A Ho:YLF laser operating in the range of 2.05 micrometers can be tuned over several characteristic lines of CO2 absorption. Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of CO2 with a repetition rate of 5 Hz and pulse energy of 75 mJ. For coherent detection, high repetition rate is required for speckle averaging to obtain highly precise measurements. However, a diode pumped Ho:Tm:YLF laser can not operate in high repetition rate due to the large heat loading and up-conversion. A Tm:fiber laser pumped Ho:YLF laser with low heat loading can operate in high repetition rate. A theoretical model has been established to simulate the performance of Tm:fiber laser pumped Ho:YLF lasers. For continuous wave (CW) operation, high pump intensity with small beam size is suitable for high efficiency. For Q-switched operation, the optimal energy extraction relies on the pump intensity, pump volume, and pump duration which is inversely proportion to the repetition rate. CW and Q-switched Ho:YLF lasers with different linear cavity configurations have been designed and demonstrated for a 30 W Tm:fiber pump laser. The CW Ho laser slope efficiency and optical-to-optical efficiencies reach 65% and 55%, respectively. The pulsed laser efficiency depends on the repetition rate. For 1 kHz operation, the optical-to-optical efficiency is 39% when the pump power is 14.5W. Currently, the injection seeding success rate is between 99.4% and 99.95%. After a ten thousand pulses, the standard deviation of the laser frequency jitter is about 3 MHz. It meets the requirements of highly precise CO2 concentration measurement. In conclusion, an injection seeded, high repetition rate, Q-switched Ho:YLF laser has been developed for a coherent CO2 differential absorption lidar. This master-slave laser system has high optical-to-optical efficiency and seeding success rate. It can potentially meet the requirements of the coherent detection of CO2 concentration by a differential absorption lidar technique.

Singh, Upendra N.↗
DOE OSTI2024

Explosively driven Richtmyer–Meshkov instability jet suppression and enhancement via coupling machine learning and additive manufacturing

The ability to control the behavior of fluid instabilities at material interfaces, such as the shock-driven Richtmyer–Meshkov instability, is a grand technological challenge with a broad number of applications ranging from inertial confinement fusion experiments to explosively driven shaped charges. In this work, we use a linear-geometry shaped charge as a means of studying methods for controlling material jetting that results from the Richtmyer–Meshkov instability. A shaped charge produces a high-velocity jet by focusing the energy from the detonation of high explosives. The interaction of the resulting detonation wave with a hollowed cavity lined with a thin metal layer produces the unstable jetting effect. By modifying the characteristics of the detonation wave prior to striking the lined cavity, the kinetic energy of the jet can be enhanced or reduced. Modifying the geometry of the liner material can also be used to alter jetting properties. We apply optimization methods to investigate several design parameterizations for both enhancing or suppressing the shaped-charge jet. This is accomplished using 2D and 3D hydrodynamic simulations to investigate the design space that we consider. We also apply new additive manufacturing methods for producing the shaped-charge assemblies, which allow for the experimental testing of complicated design geometries obtained through computational optimization. We present a direct comparison of our optimized designs with experimental results carried out at the High Explosives Application Facility at Lawrence Livermore National Laboratory.

36 MATERIALS SCIENCE↗
NASA NTRS1983

Study of noise transmission through double wall aircraft windows

Analytical and experimental procedures were used to predict the noise transmitted through double wall windows into the cabin of a twin-engine G/A aircraft. The analytical model was applied to optimize cabin noise through parametric variation of the structural and acoustic parameters. The parametric study includes mass addition, increase in plexiglass thickness, decrease in window size, increase in window cavity depth, depressurization of the space between the two window plates, replacement of the air cavity with a transparent viscoelastic material, change in stiffness of the plexiglass material, and different absorptive materials for the interior walls of the cabin. It was found that increasing the exterior plexiglass thickness and/or decreasing the total window size could achieve the proper amount of noise reduction for this aircraft. The total added weight to the aircraft is then about 25 lbs.

Vaicaitis, R.↗
NASA NTRS2006

Heat Transfer of Thermocapillary Convection in a Two-Layered Fluid System Under the Influence of Magnetic Field

Heat transfer of a two-layer fluid system has been of great importance in a variety of industrial applications. For example, the phenomena of immiscible fluids can be found in materials processing and heat exchangers. Typically in solidification from a melt, the convective motion is the dominant factor that affects the uniformity of material properties. In the layered flow, thermocapillary forces can come into an important play, which was first emphasized by a previous investigator in 1958. Under extraterrestrial environments without gravity, thermocapillary effects can be a more dominant factor, which alters material properties in processing. Control and optimization of heat transfer in an immiscible fluid system need complete understanding of the flow phenomena that can be induced by surface tension at a fluid interface. The present work is focused on understanding of the magnetic field effects on thermocapillary convection, in order to optimize material processing. That is, it involves the study of the complicated phenomena to alter the flow motion in crystal growth. In this effort, the Marangoni convection in a cavity with differentially heated sidewalls is investigated with and without the influence of a magnetic field. As a first step, numerical analyses are performed, by thoroughly investigating influences of all pertinent physical parameters. Experiments are then conducted, with preliminary results, for comparison with the numerical analyses.

Ramachandran, N.↗
NASA NTRS1994

SOFIA: Aircraft system, aft telescope cavity configuration, phase 2. Volume 1: Executive summary

This volume summarizes the tasks performed by E-Systems during Phase 2 of a study evaluating the structural modifications required to install the Stratospheric Observatory for Infrared Astronomy, SOFIA in the Boeing 747 airplane. An optimal structural modification concept for installation of the Infrared telescope is identified, and the concept is validated by analysis of the static and dynamic characteristics of the modified structure.

Source record↗
DOE OSTI2024

Formalism for Local Correction of Vertical Crabbing in Hadron Storage Ring

The Electron-Ion Collider (EIC) incorporates crab cavities in both the Electron Storage Ring (ESR) and the Hadron Storage Ring (HSR) to achieve unprecedented luminosity goals. This technical note presents a formalism for the local correction of vertical crabbing in the HSR, addressing the complexities introduced by the integration of crab cavities and the interplay between betatron coupling and crabbing dispersion. Various strategies, including the use of skew quadrupoles and adjustments of Twiss functions, are explored to compensate vertical crabbing to achieve optimal beam-beam performance. The derived theoretical formulas offer practical guidance for minimizing the required vertical crabbing corrections, and will be implemented in the HSR lattice design.

43 PARTICLE ACCELERATORS↗
NASA NTRS1972

Analysis of signal to noise enhancement using a highly selective modulation tracking filter

Experiments are reported which utilize photodielectric effects in semiconductor loaded superconducting resonant circuits for suppressing noise in RF communication systems. The superconducting tunable cavity acts as a narrow band tracking filter for detecting conventional RF signals. Analytical techniques were developed which lead to prediction of signal-to-noise improvements. Progress is reported in optimization of the experimental variables. These include improved Q, new semiconductors, improved optics, and simplification of the electronics. Information bearing signals were passed through the system, and noise was introduced into the computer model.

Haden, C. R.↗
NASA NTRS2000

A Reduced Order Model of the Linearized Incompressible Navier-Strokes Equations for the Sensor/Actuator Placement Problem

A reduced order modeling approach of the Navier-Stokes equations is presented for the design of a distributed optimal feedback kernel. This approach is based oil a Krylov subspace method where significant modes of the flow are captured in the model This model is then used in all optimal feedback control design where sensing and actuation is performed oil tile entire flow field. This control design approach yields all optimal feedback kernel which provides insight into the placement of sensors and actuators in the flow field. As all evaluation of this approach, a two-dimensional shear layer and driven cavity flow are investigated.

Allan, Brian G.↗
DOE OSTI2026

Scaling considerations for supercritical carbon dioxide cycles including turbomachinery loss models

A modeling framework for the supercritical carbon dioxide recompressed closed Brayton cycle was developed. Unlike typical models, this effort incorporated generalized empirical turbomachinery loss models. Aerodynamic, windage, and leakage losses were considered in order to address the limitations of conventional constant-efficiency turbomachinery assumptions without relying on machine-specific or computationally expensive simulations. The model enables system-level exploration of optimal cycle design across a range of power scales, including smaller scales that are relevant to microreactors and extraterrestrial power applications. Parametric studies and multi-objective optimizations are used to evaluate the trade-offs between thermal efficiency and system compactness based on an analytical heat exchanger scaling model, yielding Pareto-optimal fronts across a range of operating pressures. Results reveal that at small power scales, the Pareto-optimal compressor inlet pressure becomes subcritical due to the increasing influence of density-dependent turbomachinery losses. Here, the relative contributions of each loss mechanism are quantified, and design recommendations are provided for key parameters such as recompression split ratio and generator cavity pressure across varying power scales.

Multi-objective optimization↗