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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Electronic Structure, Bonding and Reactivity in f-Element Chemistry (Final Technical Report)

The proposed research aims to further develop and apply advanced inorganic spectroscopic methods to f-element systems, including well-defined compounds, in-situ generated complexes (including potentially complex mixtures) and transient species. Our long term goal is to develop and apply advanced inorganic spectroscopic methods in f-element chemistry in order to advance our understanding of electronic structure, bonding and reactivity in f-element systems up to the level currently available for d-block systems. A further goal of our program is the training and development of graduate students in the application of advanced inorganic spectroscopic methods for the study of f-element systems, which is critically underdeveloped at US academic institutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Flow Sensor Test Article (F-STAr) - Assembly and Water Testing Report

The Flow Sensor Test Article (F-STAr) is a new test article under development for the Mechanisms Engineering Test Loop (METL) facility at Argonne National Laboratory. F-STAr’s purpose is to provide sodium submersible, high flowrate testing capabilities for the development of sensors, components, fluid studies and more. This report will provide a status update on the assembly and initial qualification testing of F-STAr. All components have been manufactured and received. Some modifications to these components were made to support minor changes in the test article design. Additionally, the power distribution, and data acquisition and control enclosures were designed, completed, and tested along with the control system software. Furthermore, initial qualification testing was completed in water. Finally, the F-STAr submersible Electromagnetic Flowmeter (EMFM) was completed and calibrated in flowing sodium.

42 ENGINEERING↗
DOE OSTI2021

Improving the W Coating Uniformity by a COMSOL Model-Based CVD Parameter Study for Denser W f /W Composites

Tungsten (W) has the unique combination of excellent thermal properties, low sputter yield, low hydrogen retention, and acceptable activation. Therefore, W is presently the main candidate for the first wall and armor material for future fusion devices. However, its intrinsic brittleness and its embrittlement during operation bears the risk of a sudden and catastrophic component failure. As a countermeasure, tungsten fiber-reinforced tungsten (W f /W) composites exhibiting extrinsic toughening are being developed. A possible W f /W production route is chemical vapor deposition (CVD) by reducing WF 6 with H 2 on heated W fabrics. The challenge here is that the growing CVD-W can seal gaseous domains leading to strength reducing pores. In previous work, CVD models for W f /W synthesis were developed with COMSOL Multiphysics and validated experimentally. In the present article, these models were applied to conduct a parameter study to optimize the coating uniformity, the relative density, the WF 6 demand, and the process time. A low temperature and a low total pressure increase the process time, but in return lead to very uniform W layers at the micro and macro scales and thus to an optimized relative density of the W f /W composite. High H 2 and low WF 6 gas flow rates lead to a slightly shorter process time and an improved coating uniformity as long as WF 6 is not depleted, which can be avoided by applying the presented reactor model.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Energetic particle flux experiment (IMP-F and G)

The technical aspects of the University of California IMP-F experiment aboard the Explorer-34 and the University of California IMP-G (S1) and (S2) experiments aboard the Explorer-41. The experiment detectors and electronics are discussed for each experiment as well as the fabrication, preflight and post-flight history. A description of the ground support equipment is also given for each experiment. These three experiments were essentially all different. The IMP-G experiment was essentially the IMP-F experiment with the addition of four Geiger-Mueller detectors. The IMP-G (S-2) was a supplementary experiment and differed completely from the IMP-F and IMP-G experiments. It was concluded that the ground support equipment approach used for the IMP-F and IMP-G experiments where emphasis was placed on a thorough exercise and monitoring of the experiment operation during various testing phases provided a high degree of confidence and reliability in these experiments. No known electronic failures have occurred during the spacecraft lifetime although some detector problems were experienced.

Anderson, K. A.↗
NASA NTRS1973

Large ion concentration gradients below the equatorial F peak.

Very large vertical and longitudinal gradients in the ion concentrations are observed below the F peak near the magnetic equator with the retarding potential analyzer on Ogo 6. Ion concentration 'bite outs' of up to a factor of 1000 are observed above 400 km. They appear to be associated with the bottomside of the nighttime F layer. The ion composition in the minima may contain large fractions of ions heavier than O(+) (e.g., NO(+) and Fe(+)). It is suggested that convective electric fields associated with spread F steepen the bottomside of the F layer and also introduce longitudinal irregularities in the vertical ion concentration profiles.

Hanson, W. B.↗
NASA NTRS1974

Experimental transient vane temperatures in a cascade for gas stream temperature cycling between 922 and 1644 K (1200 and 2500 F)

Experimental transient turbine vane metal temperatures were obtained from tests conducted on air-cooled vanes installed in a four-vane cascade for a gas temperature cycled between 922 and 1644 K (1200 and 2500 F). Transient data were recorded by a high-speed data acquisition system. Temperatures at the same phase of each transient cycle were repeatable between cycles to within 11 kelvins (20 F), simulated cruise and idle steady-state readings were repeated by the cruise and idle readings taken from the ends of a transient half-cycle at low pressure to within 17 kelvins (30 F). The tests were conducted at pressure levels of 31 and 83 N-sq cm (45 and 120 psia) with coolant temperatures of 811 and 589 K (1000 and 600 F), respectively.

Gauntner, D. J.↗
NASA NTRS1976

Single-stage experimental evaluation of low aspect ratio, highly loaded blading for compressors. Part 9: Stage F and stage G, volume 1

Two single-stage, 0.77 hub/tip ratio axial-flow compressors were tested to evaluate the effectiveness of low aspect ratio blading as a means of obtaining higher stage loadings. One compressor, designated Stage F, was comprised of circular arc blading with an aspect ratio of 0.9 for both the rotor and stator. This compressor was tested with uniform inlet flow, hub radial, tip radial, and 180 deg arc circumferential inlet distortion. The second compressor, designated Stage G, was comprised of multiple circular arc blading with an aspect ratio of 1.0 for both the rotor and stator. This compressor was tested with uniform inlet flow only. Design rotor tip speeds for Rotor F and Rotor G were 285 m/sec (934 ft/sec) and 327 m/sec (1,074 ft/sec) respectively. Both stages operated at high loading levels with adequate efficiency and operating range. The peak efficiencies and corresponding average stage diffusion factors for Stages F and G at design rotor speed were 86.4% and 84.1% and 0.59 and 0.55 respectively. The surge margin at peak efficiency for Stage F was 12.6% and the corresponding value for Stage G was 16.5%. Both stages experienced a loss in efficiency with increasing rotor speed; however, the multiple circular arc rotor delayed the characteristic loss in efficiency within increasing Mach number to higher Mach number.

Cheatham, J. G.↗
NASA NTRS1978

E region coupling effects on the Perkins spread F instability

The Perkins instability theory for mid-latitude spread F is generalized to include the effects of the E region on growth rates. A three-layer model, representing the E region, the F region, and a resistive layer of low Pedersen conductivity which separates them, is developed. The E region Pedersen current has a stabilizing effect on the perturbed F region, thereby reducing the growth rate of the instability. For spread F onset on September 17, 1974, the maximum growth rate is found to be only one third of the Perkins growth rate. The resistive layer reduces the electric field perturbation in the E region for short wavelengths but has little effect for long wavelengths.

Klevans, E. H.↗
NASA NTRS1978

Ionospheric modification - An initial report on artificially created equatorial Spread F

A numerical simulation code for investigating equatorial Spread F in the collisional Rayleigh-Taylor regime is utilized to follow the evolution of artificial plasma density depletions injected into the bottomside nighttime equatorial F region. The 70 km diameter hole rapidly rises and steepens, forming plasma density enhancements at altitudes below the rising hole. The distribution of enhancements and depletions is similar to natural equatorial Spread F phenomena, except it occurs on a much faster time scale. These predictions warrant carrying out artificial injection experiments in the nighttime equatorial F region.

Ossakow, S. L.↗
NASA NTRS1979

Precision controllability of the F-15 airplane

A flying qualities evaluation conducted on a preproduction F-15 airplane permitted an assessment to be made of its precision controllability in the high subsonic and low transonic flight regime over the allowable angle of attack range. Precision controllability, or gunsight tracking, studies were conducted in windup turn maneuvers with the gunsight in the caged pipper mode and depressed 70 mils. This evaluation showed the F-15 airplane to experience severe buffet and mild-to-moderate wing rock at the higher angles of attack. It showed the F-15 airplane radial tracking precision to vary from approximately 6 to 20 mils over the load factor range tested. Tracking in the presence of wing rock essentially doubled the radial tracking error generated at the lower angles of attack. The stability augmentation system affected the tracking precision of the F-15 airplane more than it did that of previous aircraft studied.

Sisk, T. R.↗
NASA NTRS1981

Development of an 1100 deg F capacitor

The feasibility of developing a high temperature capacitor for 1100 F operation which is as small and light as conventional capacitors for normal operating temperatures is discussed. Pyrolyic boron nitride (PBN) was selected for the dielectric. The PBN capacitors were made by slicing and lapping material from thick blocks and then sputtering thin film electrodes. These capacitors had breakdown strengths of 7,000 volts per mil and a dissipation factor of less than 0.001 at 1100 F. Additional processing improvements were made after testing a multi-layer or stacked PBN capacitor for 1,000 hours at 1100 F. Sputter etching the wafers before depositing electrodes resulted in a reduction in dissipation factor. A sputtered boron nitride film applied to the outer electrode surfaces produced a more stable capacitor. A design for a 0.1 mu F capacitor and a summary of PBN wafer fabrication costs are given.

Stapleton, R. E.↗
NASA NTRS1982

On the dust ring current of Saturn's F-ring

The thin F-ring of Saturn, which is well within the corotating portion of the Saturnian magnetosphere, has been shown by Voyager 1 and 2 observations to be largely composed of small dust grains. Mendis et al. (1982) have argued that with plausible values of the ambient plasma density and temperature near the F-ring, these grains will be charged to around -40 volts. Mendis et al. have shown that within the corotating portion of the magnetosphere such negatively charged grains can move in circular orbits in the equatorial plane. In connection with a relative motion between the negatively charged grains and the corotating positive ions, the F-ring constitutes a ring current. The present investigation has the objective to calculate this current and to show that it would significantly alter the magnetospheric dipole field in the vicinity of the ring. A current of approximately 12,0000 A is obtained. The change in the magnetic field produced by the current could be measured by a spacecraft approaching to within 100 km above or below the F-ring plane.

Hill, J. R.↗
NASA NTRS1982

The 371 deg C(700 deg F) properties of celion 6000/n-phenylnadimide modified PMR polyimide composites

The 371 C (700 F) properties of Celion 6000/N-phenylnadimide modified PMR-15 polyimide composites were investigated to determine the feasibility of using these materials at a 371 C (700 F) service temperature. The processing characteristics and physical and mechanical properties of the composite systems are presented. The results of the 371 C (700 F) thermo-oxidation stability study suggest that the composite materials can be considered for short term (at least 100 hours) application at 371 C (700 F).

Pater, R. H.↗
NASA NTRS1982

Equatorial plasma bubbles - Vertically elongated wedges from the bottomside F layer

The possible depletion of plasma bubbles associated with the equatorial spread-F phenomenon was examined in terms of plumes mapped with the ALTAIR radar and bubbles measured by ion-drift meter on board the Explorer E satellite. The meter measured the east-west spatial relationship of ion-density depletions. The plasma bubbles were found to be vertically elongated depletions extending downward from the bottom side of the F layer in the form of tilted wedges. The electrodynamics of the bubbles correspond with observations of large eastward drift velocities of plumes comparable to the F region drift measurements. It was also determined that the west wall of large scale altitude modulations of the bottomside F layer becomes structured and evolves with the generation of secondary plumes and bubbles.

Tsunoda, R. T.↗
NASA NTRS1986

Activity in warm stars: IUE observations of early F dwarfs

Deep low dispersion, short wavelength IUE observations of 69 F dwarfs were studied by overexposing the long wavelength end of the SWP camera by up to 100 times in order to bring up the weak chromospheric and transition region (TR) emission lines. All but one of the stars observed shows evidence for stellar activity, as defined by the presence of large C II and C IV surface fluxes, with fluxes greater than 100,000 ergs/sqcm/sec. There is no correlation between surface flux and the stellar rotation rate in the early F dwarfs. The TR surface fluxes increase systematically with decreasing B-V color, with no evidence for any decrease in the activity as the convection zones become very small. It is argued that there is a fundamental difference in the atmospheric heating mechanisms between early F dwarfs and solar-like stars. The heating of the TR in the early F dwarfs may be dominated by acoustic heating.

Walter, Frederick M.↗
NASA NTRS1986

Benchmark full configuration-interaction calculations on H2O, F, and

Full configuration-interaction calculations are reported, and compared to other methods, for H2O at its equilibrium geometry and at two geometries with the H-O bonds stretched. Since the percentage of the self-consistent field (SCF) reference in the full configuration-interaction (FCI) wave function decreases greatly with the bond elongation, the accuracy of techniques based on a single reference do not compare well with the FCI results. However, the results from a complete active space SCF/multireference configuration-interaction (CASSCF/MRCI) treatment are in good agreement with the FCI. Correlation effects in F compared to Ne are far more similar than for Fcompared to Ne, despite F- and Ne being isoelectronic. Since the importance of higher than double excitations is more important for F- than F, a very high percentage of the correlation must be obtained to accurately compute the electron affinity. In a CASSCF/MRCI treatment the higher than quadruple excitations contribute 0.02 eV to the electron affinity (EA), even for modest basis sets.

Bauschlicher, C. W., Jr.↗
NASA NTRS1987

The onset of chromospheric activity among the A- and F- type stars

IUE observations of C II lambda1335 and C IV lambda1549 and ground-based observations of He I lambda5876 have previously discovered intense levels of chromospheric activity among early F type stars. Virtually all F dwarfs show stronger chromospheric and transition region emission than do the cooler and more deeply convective dwarf stars like the Sun. The IUE spectra and those of He lambda5876 place the onset of stellar activity along the main sequence near a color B - V = 0.28, which corresponds approximately to spectral type FO and an effective temperature of 7300 K. However, existing X-ray observations of A and F stars suggest that coronal activity may reach a peak blueward of this high temperature boundary at B - V = 0.28 before vanishing among the early and mid A-type stars. Discussed are preliminary results of a new effort to refine the location of the high temperature boundary to chromospheric activity among A- and F- type stars, making use of low dispersion short-wavelength spectra from the IUE archives from which the strengths of C IV, C II, and Lyman alpha emission have been measured.

Simon, Theodore↗
NASA NTRS1988

Transition region fluxes in A-F Dwarfs: Basal fluxes and dynamo activity

The transition region spectra of 87 late A and early F dwarfs and subgiants were analyzed. The emission line fluxes are uniformly strong in the early F stars, and drop off rapidly among the late A stars. The basal flux level in the F stars is consistent with an extrapolation of that observed among the G stars, while the magnetic component displays the same flux-flux relations seen among solar-like stars. Despite the steep decrease in transition region emission flux for B-V less than 0.28, C II emission is detected in alpha Aql (B-V = 0.22). The dropoff in emission is inconsistent with models of the mechanically generated acoustic flux available. It is concluded that, although the nonmagnetic basal heating is an increasingly important source of atmospheric heating among the early F stars, magnetic heating occurs in any star which has a sufficiently thick convective zone to generate acoustic heating.

Walter, Frederick M.↗