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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Low LBNP tolerance in men is associated with attenuated activation of the renin-angiotensin system

Plasma vasoactive hormone concentrations [epinephrine (p(Epi)), norepinephrine (p(NE)), ANG II (p(ANG II)), vasopressin (p(VP)), endothelin-1 (p(ET-1))] and plasma renin activity (p(RA)) were measured periodically and compared during lower body negative pressure (LBNP) to test the hypothesis that responsiveness of the renin-angiotensin system, the latter being one of the most powerful vasoconstrictors in the body, is of major importance for LBNP tolerance. Healthy men on a controlled diet (2,822 cal/day, 2 mmol. kg(-1). day(-1) Na(+)) were exposed to 30 min of LBNP from -15 to -50 mmHg. LBNP was uneventful for seven men [25 +/- 2 yr, high-tolerance (HiTol) group], but eight men (26 +/- 3 yr) reached presyncope after 11 +/- 1 min [P < 0.001, low-tolerance (LoTol) group]. Mean arterial pressure (MAP) did not change measurably, but central venous pressure and left atrial diameter decreased similarly in both groups (5-6 mmHg, by approximately 30%, P < 0.05). Control (0 mmHg LBNP) hormone concentrations were similar between groups, however, p(RA) differed between them (LoTol 0.6 +/- 0.1, HiTol 1.2 +/- 0.1 ng ANG I. ml(-1). h(-1), P < 0.05). LBNP increased (P < 0. 05) p(RA) and p(ANG II), respectively, more in the HiTol group (9.9 +/- 2.2 ng ANG I. ml(-1). h(-1) and 58 +/- 12 pg/ml) than in LoTol subjects (4.3 +/- 0.9 ng ANG I. ml(-1). h(-1) and 28 +/- 6 pg/ml). In contrast, the increase in p(VP) was higher (P < 0.05) in the LoTol than in the HiTol group. The increases (P < 0.05) for p(NE) were nonsignificant between groups, and p(ET-1) remained unchanged. Thus there may be a causal relationship between attenuated activation of p(RA) and p(ANG II) and presyncope, with p(VP) being a possible cofactor. Measurement of resting p(RA) may be of predictive value for those with lower hypotensive tolerance.

NASA Center ARC↗
DOE OSTI2025

Oxide Dispersion Strengthened Ferritic Steel Wire Feedstock Development for Larger Format Additive Manufacturing (CRADA Final Report)

This CRADA project funded through DOE’s INFUSE program sought to demonstrate the viability of fabricating large, complex parts from oxide dispersion strengthened (ODS) steel with advanced manufacturing. Exhibiting excellent radiation tolerance and high mechanical performance at elevated temperatures, ODS steel is a promising structural material candidate for near-plasma components in fusion energy systems. Its use, however, has been limited by a lack of manufacturability. This project sought to produce ODS steel wire through a solid-state shear assisted extrusion process and then demonstrate that the wire can undergo controlled local melting while being welded with the final part sufficiently retaining the beneficial properties of ODS steel. This would allow the use of wire-arc additive manufacturing (WAAM) to manufacture large-scale ODS parts, even though ODS is currently only available as a powder. WAAM is a promising technique for producing components like the replaceable ARC vacuum vessel in CFS’ fusion reactor design. Meanwhile, this project will also expand PNNL’s capability in producing custom wire feedstock with friction extrusion, enabling downstream large-scale manufacturing with WAAM and solid-state based additive manufacturing. The project achieved its goals of developing tooling and fixturing to produce ODS wire at smaller diameters than previous projects. Several small lengths of wire of 1.5 mm and 2.5 mm diameter in the range of 2.5-30 mm long were produced at tool temperatures that are known to cause ODS particle coarsening (~1200 °C). Fixtures and tooling for longer (>1 m) wires were developed but further process development is needed reduce tool temperature during extrusions and to increase wire length needed for WAAM testing and development.

36 MATERIALS SCIENCE↗
NASA NTRS1980

Voyager spacecraft electrostatic discharge testing

The program of environmental testing undergone by the Voyager spacecraft in order to simulate the transient voltage effects of electrostatic discharges expected in the energetic plasma environment of Jupiter is reported. The testing consists of studies of the electrostatic discharge characteristics of spacecraft dielectrics in a vacuum-chamber-electron beam facility, brief piece part sensitivity tests on such items as a MOSFET multiplexer and the grounding of the thermal blanket, and assembly tests of the magnetometer boom and the science boom. In addition, testing of a complete spacecraft was performed using two arc sources to simulate long and short duration discharge sources for successive spacecraft shielding and grounding improvements. Due to the testing program, both Voyager 1 and Voyager 2 experienced tolerable electrostatic discharge-caused transient anomalies in science and engineering subsystems, however, a closer duplication of the spacecraft environment is necessary to predict and design actual spacecraft responses more accurately.

Whittlesey, A.↗
DOE OSTI2019

Elemental Characterization of Neutron-Irradiated Tungsten Using the GD-OES Technique

In reactor-relevant fusion divertor conditions, tungsten (W) will be used as an armor material due to its excellent thermal properties. It will be exposed to impurities from numerous sources, including ion implantation and mixing, neutron transmutation, low-Z plasma-facing-component (PFC) redeposition and codeposition of deuterium and tritium fuel, and trapped helium bubbles. The impurity plasma material–interaction effects are a concern because they can cause gradual degradation of the material and of plasma performance due to dust formation, fuel retention, and even changes to the thermal and mechanical properties of the W armor. It is crucial to measure the amount of impurities in W, and the glow discharge–optical emission spectroscopy (GD-OES) technique is exceptionally well suited for analysis of irradiated samples. GD-OES can measure a sample’s elemental composition by sputtering the surface of the sample, ionizing the eroded material, and measuring the optical emission of the excited atoms. In order for the GD-OES technique to be applied to neutron-irradiated tungsten samples, a mounting system for miniature samples was designed. The sample mounting and centering procedure was successful in measuring the depth distribution of control W and W alloy sample elemental concentrations. These control depth spectra will be used as elemental references for postirradiated samples. The residence time of surface layers was measured, a comparison of signals from different anodes was completed, and the influence of initial surface roughness or nonuniformity was understood. The depth distribution of an arc-welded W-0.4% rhenium (Re) alloy was measured to have a stable Re signal that was distributed evenly in the W matrix. Here, the methods developed here will allow for quantification of impurities and transmutation amounts in neutron-irradiated W. GD-OES is a powerful tool but requires calibration and careful optimization of the parameters to obtain meaningful results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

MOLECULAR ENVIRONMENT AND AN X-RAY SPECTROSCOPY OF SUPERNOVA REMNANT KESTEVEN 78

We investigate the molecular environment of the Galactic supernova remnant (SNR) Kesteven 78 and perform an XMM-Newton X-ray spectroscopic study for the northeastern edge of the remnant. SNR Kes 78 is found to interact with the molecular clouds (MCs) at a systemic local standard of rest velocity of 81 km s{sup -1}. At around this velocity, the SNR appears to contact a long molecular strip in the northeast and a large cloud in the east as revealed in the {sup 13}CO line, which may be responsible for the radio brightness peak and the OH maser, respectively. The {sup 12}CO-line bright region morphologically matches the eastern bright radio shell in general, and the SNR is consistent in extent with a CO cavity. Broadened {sup 12}CO-line profiles discerned in the eastern maser region and the western clumpy molecular arc and the elevated {sup 12}CO (J = 2-1)/(J = 1-0) ratios along the SNR boundary may be signatures of shock perturbation in the molecular gas. The SNR-MC association places the SNR at a kinematic distance of 4.8 kpc. The X-rays arising from the northeastern radio shell are emitted by underionized hot ({approx}1.5 keV), low-density ({approx}0.1 cm{sup -3}) plasma with solar abundance, and the plasma may be of intercloud origin. The age of the remnant is inferred to be about 6 kyr. The size of the molecular cavity in Kes 78 implies an initial mass around 22 M{sub Sun} for the progenitor.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Oxide Dispersion Strengthened Ferritic Steel Wire Feedstock Development for Large Format Additive Manufacturing - CRADA 620 (Abstract)

This CRADA project funded through DOE’s INFUSE program seeks to demonstrate the viability of fabricating large, complex parts from oxide dispersion strengthened (ODS) steel with advanced manufacturing. Exhibiting excellent radiation tolerance and high mechanical performance at elevated temperatures, ODS steel is a promising structural material candidate for near-plasma components in fusion energy systems. Its use, however, has been limited by a lack of manufacturability. This project will seek to produce ODS steel wire through a solid-state shear assisted extrusion process and then demonstrate that the wire can undergo controlled local melting while being welded with the final part sufficiently retaining the beneficial properties of ODS steel. This would allow the use of wire-arc additive manufacturing (WAAM) to manufacture large-scale ODS parts, even though ODS is currently only available as a powder. WAAM is a promising technique for producing components like the replaceable ARC vacuum vessel in CFS’ fusion reactor design. Meanwhile, this project will also expand PNNL’s capability in producing custom wire feedstock with friction extrusion, enabling downstream large-scale manufacturing with WAAM and solid-state based additive manufacturing.

36 MATERIALS SCIENCE↗
NASA NTRS1980

Particle flux decrease-increase events at synchronous orbit and the temporal sequence of aurora during substorms

A systematic temporal correlation has been found between the energetic particle intensity variations measured at 6.6 earth radii and the development of large scale auroral features. The intensification and equatorward drift of eastwest oriented stable discrete homogeneous auroral arc systems coincide with the decrease in energetic particle intensity at 6.6 earth radii as the nightside magnetosphere develops into a more tail-like configuration. The subsequent major breakup of the aurora coincides with the recovery in particle intensity as the field returns to a more dipolar configuration. Since this prominent decrease-increase sequence must be related to the intensification or inward convection of the tail current plasma sheet configuration followed by its diversion or dissipation, the auroral correlation documented here closely links the auroral particle precipitation to the plasma sheet and tail current dynamics.

Erickson, K. N.↗
NASA NTRS2000

Urinary excretion of LH and testosterone from male rats during exposure to increased gravity: post-spaceflight and centrifugation

A dissociation between plasma luteinizing hormone (LH) and testosterone (T) appears to exist during exposure to altered gravity. The pulsatile nature of LH release and the diurnal variability of T secretion may mask or bias the effects of altered gravity on the pituitary-gonadal axis when analyzing plasma concentrations. Therefore, we examined the relationship between the excretion of urinary LH and T in male Sprague-Dawley rats during exposure to increased gravity upon return to Earth following a 14-day spaceflight (n = 6) and by 12 days of centrifugation at 2g (n = 8). Excreted LH and T were elevated on the first 3 days postflight. Excreted T was elevated between Days 1 and 8 of centrifugation; however, excreted LH was reduced on Days 2 and 3 compared with control animals. Excreted LH and T were significantly correlated (R = 0.731 and 0.706, respectively) in postspaceflight and centrifuged animals. Correlation curves had similar slopes (0.0213 and 0.023, respectively), but different y-intercepts (-1.43 and 3.32, respectively). The sustained increase in excreted T during centrifugation suggests that the pituitary-gonadal axis in postspaceflight animals may adapt quicker to increased gravity. The upward shift in the correlation curve exhibited by the centrifuged animals suggests that the sensitivity of LH-induced T release is increased in these animals. The previous dissociation between plasma LH and T during altered gravity was not observed in the present study in which excreted LH and T were measured.

short duration↗
DOE OSTI2015

Multi-epoch study of the gamma-ray emission within the M87 magnetosphere model

M87 is a nearby radio galaxy that has been detected at energies ranging from radio to very high energy (VHE) gamma-rays. Its proximity and its jet, misaligned from the line of sight allow detailed morphological studies. The imaging atmospheric Cherenkov technique (from 100 GeV to 10 TeV) provides insufficient angular resolution (few arc-minutes) to resolve the M87 emission region. However, the short time scale variability observed by MAGIC, HESS and VERITAS suggests the TeV emission is coming from a very small region, most likely close to the core. We propose that the variable TeV emission may be produced in a pair-starved region of the central black hole (BH) magnetosphere, i.e. a region where the density of the electron-positron plasma is not sufficient to completely screen the accelerating electric field. The funnel, a low density and magnetically dominated region around the poles, appears as a favourable site of low-density where a Blandford-Znajek process may explain the main properties of the TeV γ-ray emission from M87. We produce a broadband spectral energy distribution (SED) of the resulting radiation and compare the model with the observed fluxes from the nucleus of M87, for both low and high γ-ray activities. We finish with a brief discussion on the connection between the accretion rate and the intermittence in the formation of gaps in the magnetosphere.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1992

Design of a precise and stable composite telescope structure for the Ultraviolet Coronagraph Spectrometer (UVCS)

The Ultraviolet Coronagraph Spectrometer is a state of the art instrument which will be flown aboard the ESA SOHO spacecraft in 1995. A major objective of the SOHO is to investigate the solar corona and the solar wind by measuring parameters of the plasma, both in the source and acceleration regions, and in interplanetary space. The UVCS will provide ultraviolet spectroscopic diagnostics of temperature, density, and outflow velocity for coronal ions located between the base of the solar corona and 10 solar radii. The requirements placed on the UVCS telescope structure by the science and the spacecraft are challenging. Obtaining this scientific data requires that the telescope maintain pointing stability within a few arc-seconds in a transient thermal environment and an imaging stability within a few microns. Strict mass allowances permit only 22 kg for the 2.5 meter long telescope structure out of a total instrument allotment of 124 kg. The instrument is required to have a high minimum natural frequency of 70 Hertz and withstand launch inertia loads in excess of 18-G's while kinematically supported.

Kilpatrick, Mark C.↗
DOE OSTI2013

Epitaxial growth of AlN films via plasma-assisted atomic layer epitaxy

Thin AlN layers were grown at 200–650 °C by plasma assisted atomic layer epitaxy (PA-ALE) simultaneously on Si(111), sapphire (1120), and GaN/sapphire substrates. The AlN growth on Si(111) is self-limited for trimethyaluminum (TMA) pulse of length > 0.04 s, using a 10 s purge. However, the AlN nucleation on GaN/sapphire is non-uniform and has a bimodal island size distribution for TMA pulse of ≤0.03 s. The growth rate (GR) remains almost constant for T{sub g} between 300 and 400 °C indicating ALE mode at those temperatures. The GR is increased by 20% at T{sub g} = 500 °C. Spectroscopic ellipsometry (SE) measurement shows that the ALE AlN layers grown at T{sub g} ≤ 400 °C have no clear band edge related features, however, the theoretically estimated band gap of 6.2 eV was measured for AlN grown at T{sub g} ≥ 500 °C. X-ray diffraction measurements on 37 nm thick AlN films grown at optimized growth conditions (T{sub g} = 500 °C, 10 s purge, 0.06 s TMA pulse) reveal that the ALE AlN on GaN/sapphire is (0002) oriented with rocking curve full width at the half maximum (FWHM) of 670 arc sec. Epitaxial growth of crystalline AlN layers by PA-ALE at low temperatures broadens application of the material in the technologies that require large area conformal growth at low temperatures with thickness control at the atomic scale.

36 MATERIALS SCIENCE↗
NASA NTRS1982

Electric fields measured by ISEE-1 within and near the neutral sheet during quiet and active times

An understanding of the physical processes occurring in the magnetotail and plasmasheet during different interplanetary magnetic field orientations and differing levels of ground magnetic activity is crucial for the development of a theory of energy transfer from the solar wind to the particles which produce auroral arcs. In the present investigation, the first observations of electric fields during neutral sheet crossings are presented, taking into account the statistical correlations of the interplanetary magnetic field direction and ground activity with the character of the electric field. The electric field data used in the study were obtained from a double probe experiment on the ISEE-1 satellite. The observations suggest that turbulent electric and magnetic fields are intimately related to plasma acceleration in the neutral sheet and to the processes which create auroral particles.

Cattell, C. A.↗
NASA NTRS2003

The response of Dahl salt-sensitive and salt-resistant female rats to a space flight model

Vitamin D metabolism in the Dahl salt-sensitive (S) rat, a model of salt-induced hypertension, differs from that in the Dahl salt-resistant (R) rat. We have tested the hypothesis that differences in vitamin D metabolism would render the Dahl S rat more susceptible than the Dahl R rat to the effects of a space flight model. Dahl female rats were tail suspended (hind limb unloaded) for 28 days, while fed a low salt (3 g/kg sodium chloride) diet. Plasma 25-OHD concentrations of S rats were significantly lower than that of R rats. Plasma 1,25-(OH)2D concentration was 50% lower in unloaded than in loaded S rats, but was unaffected in unloaded R rats. The left soleus muscle weight and breaking strength of the left femur (torsion test) were 50% and 25% lower in unloaded than in loaded S and R rats. The mineral content of the left femur, however, was significantly lower (by 11%) only in unloaded S rats. We conclude that female S rats are more vulnerable than female R rats to decreases in plasma 1,25-(OH)2D concentration and femur mineral content during hind limb unloading, but equally vulnerable to muscle atrophy and reduced breaking strength of the femur.

NASA Program Biomedical Research and Countermeasur↗
NASA NTRS1978

Investigation of high voltage spacecraft system interactions with plasma environments

The exposure of high voltage spacecraft systems to the charged particle environment of space can produce interactions that will influence system operation. An experimental investigation of these interactions has been undertaken for insulator and conductor test surfaces biased up to plus or minus 1 kV in a simulated low earth orbit charged particle environment. It has been found that these interactions are controlled by the insulator surfaces surrounding the biased conductors. For positive applied voltages the electron current collection can be enhanced by the insulators. For negative applied voltages the insulator surface confines the voltage to the conductor region; this can cause arcing. Understanding these interactions and the technology to control their impact on system operation is essential to the design of solar cell arrays for ion drive propulsion applications that use direct drive power processing.

Stevens, N. J.↗
DOE OSTI2014

CARMA LARGE AREA STAR FORMATION SURVEY: OBSERVATIONAL ANALYSIS OF FILAMENTS IN THE SERPENS SOUTH MOLECULAR CLOUD

We present the N{sub 2}H{sup +} (J = 1 → 0) map of the Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey. The observations cover 250 arcmin{sup 2} and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km s{sup –1}, and they can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N{sub 2}H{sup +} emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N{sub 2}H{sup +} filaments comprise a single observed dust continuum filament. The difference between the dust and gas filament widths casts doubt on Herschel ability to resolve the Serpens South filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gradient along one of these filaments was previously postulated as evidence for mass infall toward the central cluster, but these kind of gradients can be interpreted as projection of large-scale turbulence.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

WE-E-BRE-02: BEST IN PHYSICS (THERAPY) - Stereotactic Radiotherapy for Renal Sympathetic Ablation for the Treatment of Refractory Hypertension

Purpose: To determine the safety and efficacy of stereotactic radiotherapy as a novel treatment for patients with refractory hypertension in a swine model. Uncontrolled hypertension is a significant contributor to morbidity and mortality, substantially increasing the risk of ischemic stroke, ischemic heart disease, and kidney failure. Methods: High-resolution computed tomography (CT) images of anesthetized pigs were acquired and treatment plans for each renal artery and nerve were developed using our clinically implemented treatment planning system. Stereotactic radiotherapy, 40Gy in single fraction was delivered bilaterally to the renal nerves using a state-of-the-art medical linear accelerator under image guidance utilizing dynamic conformal arcs. Dose to nearby critical organs was evaluated by dosevolume histogram analysis and correlated to toxicity data obtained through follow up pathology analysis. The animals were observed for six months with serial measurements of blood pressure, urine analysis, serum laboratories, and overall clinical and behavioral status. Results: All animals survived to the follow-up point without evidence of renal dysfunction (stable serum creatinine), skin changes, or behavioral changes that might suggest animal discomfort. Plasma norepinephrine levels (ng/ml) were followed monthly for 6 months. The average reduction observed was 63%, with the median reduction at 73.5%. Microscopic evaluation 4–6 weeks after treatment showed evidence of damage to the nerves around treated renal arteries. Considerable attenuation in pan neurofilament expression by immunohistochemistry was observed with some vacuolar changes indicative of injury. There was no histological or immunohistochemical evidence of damage to nearby spinal cord or spinal nerve root structures. Conclusion: Our preclinical studies have shown stereotactic radiotherapy to the renal sympathetic plexus to be safe and effective in reducing blood pressure, thus this approach holds great promise as a novel treatment modality for patients with refractory hypertension. This study was funded by the Stanford University Cardiovascular Institute. B. Loo and P. Maxim have received funding from RaySearch Laboratories.

60 APPLIED LIFE SCIENCES↗
NASA NTRS2004

Liquid-metal-fed Pulsed Plasma Thrusters for In-space Propulsion

Liquid metal propellants may provide a path toward more reliable and efficient pulsed plasma thrusters (PPTs). Conceptual thruster designs which eliminate the need for high current switches and propellant metering valves are described. Propellant loading techniques are suggested that show promise to increase thruster propellant utilization, dynamic, and electrical efficiency. Calibration results from a compact, electromagnetically-pumped propellant feed system are presented. Results for lithium and gallium propellants show capability to meter propellant at flow rates up to 10 +/- 0.1 mg/s. Experiments investigating the initiation of arc discharges using liquid metal droplets are presented. High speed photography and laser interferometry provide spatially and temporally resolved information on the decomposition of liquid metal droplets , and the evolution of the accelerating current channel.

Markusic, Thomas E.↗
DOE OSTI2024

Energy Transport and Conversion Above a Bright Discrete Auroral Arc

Magnetically connected observations of particle distributions and luminosity from the Reimei spacecraft are used to examine energy transport and conversion occurring above a discrete auroral arc. By combining imaging and in situ measurements it is shown how transverse electromagnetic and kinetic energy fluxes measured along the spacecraft trajectory converge across geomagnetic field-lines into the acceleration region. It is shown how cross-field energy transport is facilitated by the formation of vortices along the length of the arc. From an integration over the vertical extent of the acceleration region it is shown that the transverse and field-aligned flow of energy into the arc locally supports the dissipation needed to power the electron acceleration observed. Estimates of gradients in electromagnetic and kinetic energy flows show how field-aligned electron energization in the acceleration region is supported by the divergence of Poynting flux along and across the background magnetic field.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗