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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 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

The detection of long-term changes in stratospheric ozone Scientific requirements and current results from satellite-based measurement systems

The ability to detect subtle trends in upper stratospheric ozone places strict requirements on satellite-based Solar Backscatter Ultraviolet (SBUV) sensors intended for this purpose. Simulation of the long-term change in backscattered radiance indicates trends in the range 1.0-1.6 percent per decade depending on wavelength for an ozone depletion scenario based on chlorofluorocarbon (CFC) chemistry. The maximum percentage change in the measured quantity, as would be sensed by the Nimbus-7 SBUV experiment and future similar instruments, is roughly a factor of two less than the maximum percentage change in ozone, the quantity of geophysical interest. Furthermore, interannual variations, whose magnitude can be estimated from the SBUV data set, could obscure a CFC-related trend in radiance when viewed over a period less than a decade. Even when such atmospheric noise and possible solar cycle variations are neglected, the detection of an ozone trend of the magnitude predicted for CFC-related chemistry requires a set of radiance measurements that are internally consistent to 1 percent or better over a time span of a decade.

Frederick, J. E.↗
NASA NTRS1995

Results of the 1995 JPL balloon flight solar cell calibration program

The Jet Propulsion Laboratory (JPL) solar cell calibration program was conceived to produce reference standards for the purpose of accurately setting solar simulator intensities. The concept was to fly solar cells on a high-altitude balloon, to measure their output at altitudes near 120,000 ft (36.6 km), to recover the cells, and to use them as reference standards. The procedure is simple. The reference cell is placed in the simulator beam, and the beam intensity is adjusted until the reference cell reads the same as it read on the balloon. As long as the reference cell has the same spectral response as the cells or panels to be measured, this is a very accurate method of setting the intensity. But as solar cell technology changes, the spectral response of the solar cells changes also, and reference standards using the new technology must be built and calibrated. Until the summer of 1985, there had always been a question as to how much the atmosphere above the balloon modified the solar spectrum. If the modification was significant, the reference cells might not have the required accuracy. Solar cells made in recent years have increasingly higher blue responses, and if the atmosphere has any effect at all, it would be expected to modify the calibration of these newer blue cells much more so than for cells made in the past. JPL has been flying calibration standards on high-altitude balloons since 1963 and continues to organize a calibration balloon flight at least once a year. The 1995 flight was the 48th flight in this series. The 1995 flight incorporated 46 solar cell modules from 7 different participants. The payload included Si, amorphous Si, GaAs, GaAs/Ge, dual junction cells, top and bottom sections of dual junction cells, and a triple junction cell. A new data acquisition system was built for the balloon flights and flown for the first time on the 1995 flight. This system allows the measurement of current-voltage (I-V) curves for 20 modules in addition to measurement of modules with fixed loads as had been done in the past.

Anspaugh, B. E.↗
NASA NTRS1996

SAMPIE Measurements of the Space Station Plasma Current Analyzed

In March of 1994, STS-62 carried the NASA Lewis Research Center's Solar Array Module Plasma Interactions Experiment (SAMPIE) into orbit, where it investigated the plasma current collected and the arcs from solar arrays and other space power materials immersed in the low-Earth-orbit space plasma. One of the important experiments conducted was the plasma current collected by a four-cell coupon sample of solar array cells for the international space station. The importance of this experiment dates back to the 1990 and 1991 meetings of the Space Station Electrical Grounding Tiger Team. The Tiger Team determined that unless the electrical potentials on the space station structure were actively controlled via a plasma contactor, the space station structure would arc into the plasma at a rate that would destroy the thermal properties of its surface coatings in only a few years of operation. The space station plasma contactor will control its potentials by emitting electrons into the surrounding low-Earth-orbit plasma at the same rate that they are collected by the solar arrays. Thus, the level at which the space station solar arrays can collect current is very important in verifying that the plasma contactor design can do its job.

Source record↗
NASA NTRS2006

Polarization Effects Aboard the Space Interferometry Mission

For precision displacement measurements, laser metrology is currently one of the most accurate measurements. Often, the measurement is located some distance away from the laser source, and as a result, stringent requirements are placed on the laser delivery system with respect to the state of polarization. Such is the case with the fiber distribution assembly (FDA) that is slated to fly aboard the Space Interferometry Mission (SIM) next decade. This system utilizes a concatenated array of couplers, polarizers and lengthy runs of polarization-maintaining (PM) fiber to distribute linearly-polarized light from a single laser to fourteen different optical metrology measurement points throughout the spacecraft. Optical power fluctuations at the point of measurement can be traced back to the polarization extinction ration (PER) of the concatenated components, in conjunction with the rate of change in phase difference of the light along the slow and fast axes of the PM fiber.

fiber distribution↗
NASA NTRS2005

Measurements of Breakdown Field and Forward Current Stability in 3C-SiC P-N Junction Diodes Grown on Step-Free 4H-SiC

This paper reports on initial fabrication and electrical characterization of 3C-SiC p-n junction diodes grown on step-free 4H-SiC mesas. Diodes with n-blocking-layer doping ranging from approx. 2 x 10(exp 16)/cu cm to approx.. 5 x 10(exp 17)/cu cm were fabricated and tested. No optimization of junction edge termination or ohmic contacts was employed. Room temperature reverse characteristics of the best devices show excellent low-leakage behavior, below previous 3C-SiC devices produced by other growth techniques, until the onset of a sharp breakdown knee. The resulting estimated breakdown field of 3C-SiC is at least twice the breakdown field of silicon, but is only around half the breakdown field of <0001> 4H-SiC for the doping range studied. Initial high current stressing of 3C diodes at 100 A/sq cm for more than 20 hours resulted in less than 50 mV change in approx. 3 V forward voltage. 3C-SiC, pn junction, p+n diode, rectifier, reverse breakdown, breakdown field,heteroepitaxy, epitaxial growth, electroluminescence, mesa, bipolar diode

Neudeck, Philip G.↗
DOE OSTI2024

Summary of Alloy 617 and Alloy 709 Elevated Temperature Crack Growth Test Results from the Planned FY24 Crack Growth Test Activities

This report covers the results from crack growth rate testing performed at Idaho National Laboratory in the fiscal year 2024. It includes two creep crack growth rate tests and two creep-fatigue crack growth rate tests. Results are shown for each of these tests, included crack growth measured during the test using direct current potential drop, and measurements based off of the fracture surface. Load line displacement, as well as load, were also collected during the tests. Detailed analysis of the results will continue into the next fiscal year, however, a number of potential improvements to the equipment and testing procedures were identified that will increase testing reliability and throughput, as well as decrease complications with the analysis.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2000

Measurement of the Heat Capacity of He-II Under a Heat Current Near the Lambda Transition

We present preliminary measurements of the heat capacity of superfluid helium-4 under an applied heat current near the lambda transition. The calorimeter is a standard cylindrical thermal conductivity cell with a 0.6 mm gap between two copper endplates. The sidewall is made of stainless steel. A heat current density in the range of 1 to 4 microW/sq cm is applied through the helium sample while a pulse method is used to measure the heat capacity. Temperature changes are recorded with high-resolution thermometers (HRTs) located on the top and bottom endplates. Corrections are made to the readings of the HRTs to account for the Kapitza boundary resistance and the anomalous Kapitza boundary resistance. After the corrections, both the top and the bottom HRTs. give the same heat capacity values. The heat capacity is found to be much larger than the prediction of recent theories. We also plotted our data on a scaled plot to test the prediction of scaling by the theories. The result and its interpretation will be presented. The cell height was deliberately made to be thin to reduce the effects of gravity. Nonetheless, gravity is expected to have significant effects on the heat capacity data in the temperature range of our measurement. A space experiment would remove this unwanted gravity effect and allow the true physics to be examined. Moreover, in the absence of gravity, a deeper cell can be used allowing HRTs to be mounted on to the sidewall providing direct measurements of the helium temperature, unaffected by the anomalous Kapitza boundary resistance.

Harter, Alexa W.↗
NASA NTRS2003

Ground Tests of High-Voltage Solar Arrays Immersed in a Low Density Plasma

Five different types of solar arrays have been tested in large vacuum chamber. Arc inception voltages, arc rates, and current collections are measured for samples with different coverglass materials and thickness, interconnect designs, and cell sizes. It is shown that the array with wrapthrough interconnects have the highest arc threshold and the lowest current collection. Coverglass design with overhang results in decrease of current collection and increase of arc threshold. Doubling coverglass thickness does not improve measured array parameters. Both arc inception voltage and current collection increase significantly with increasing a sample temperature to 80 C. Sustained discharges are initiated between adjacent cells with potential differences of 40 V for the sample with 300 pm coverglass thickness and 60 V for the sample with 150 urn coverglass thickness.

Vayner, Boris↗
NASA NTRS2011

A Rocket-Base Study of Auroral Electrodynamics Within the Current Closure Ionosphere

The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission, in conjunction with the PFISR Radar, was designed to observe the three-dimensional current system of a stable auroral arc system. ACES utilized two well instrumented payloads flown along very similar magnetic field footprints, at various altitudes with small temporal separation between both payloads. ACES High, the higher altitude payload (apogee 360 km), took in-situ measurements of the plasma parameters above the current closure region to provide the input signature into the lower ionosphere. ACES Low, the low-altitude payload (apogee 130 km), took similar observations within the current closure region, where cross-field currents can flow. We present results comparing observations of the electric fields, magnetic fields, electron flux, and the electron temperature at similar magnetic footpoints between both payloads. We further present data from all-sky imagers and PFISR detailing the evolution of the auroral event as the payloads traversed regions connected by similar magnetic footpoints. Current measurements derived from the magnetometers on both payloads are further compared. We examine data from both PFISR and observations on the high-altitude payload which we interpreted as a signature of electron acceleration by means of Alfv n waves. We further examine all measurements to understand ionospheric conductivity and how energy is being deposited into the ionosphere through Joule heating. Data from ACES is compared against models of Joule heating to make inferences regarding the effect of collisions at various altitudes.

Kaeppler, Stephen R.↗
NASA NTRS2011

Current Closure in the Auroral Ionosphere: Results from the Auroral Current and Electrodynamics Structure Rocket Mission

The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission was designed to observe electrodynamic and plasma parameters above and within the current closure region of the auroral ionosphere. Two well instrumented payloads were flown along very similar magnetic field footprints, at different altitudes, with small temporal separation between both payloads. The higher altitude payload (apogee 360 km), obtained in-situ measurements of electrodynamic and plasma parameters above the current closure region to determine the input signature. The low altitude payload (apogee 130 km), made similar observations within the current closure region. Results are presented comparing observations of the electric fields, magnetic components, and the differential electron energy flux at magnetic footpoints common to both payloads. In situ data is compared to the ground based all-sky imager data, which presents the evolution of the auroral event as the payloads traversed through magnetically similar regions. Current measurements derived from the magnetometers on the high altitude payload observed upward and downward field-aligned currents. The effect of collisions with the neutral atmosphere is investigated to determine it is a significant mechanism to explain discrepancies in the low energy electron flux. The high altitude payload also observed time-dispersed arrivals in the electron flux and perturbations in the electric and magnetic field components, which are indicative of Alfven waves.

Kaeppler, S. R.↗
NASA NTRS2012

Current Closure in the Auroral Ionosphere: Results from the Auroral Current and Electrodynamics Structure Rocket Mission

The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission was designed to observe electrodynamic and plasma parameters above and within the current closure region of the auroral ionosphere. Two well instrumented payloads were flown along very similar magnetic field footprints, at different altitudes, with small temporal separation between both payloads. The higher altitude payload (apogee 360 km), obtained in-situ measurements of electrodynamic and plasma parameters above the current closure region to determine the input signature. The low altitude payload (apogee 130 km), made similar observations within the current closure region. Results are presented comparing observations of the electric fields, magnetic components, and the differential electron energy flux at magnetic footpoints common to both payloads. In situ data is compared to the ground based all-sky imager data, which presents the evolution of the auroral event as the payloads traversed through magnetically similar regions. Current measurements derived from the magnetometers on the high altitude payload observed upward and downward field-aligned currents. The effect of collisions with the neutral atmosphere is investigated to determine if it is a significant mechanism to explain discrepancies in the low energy electron flux. The high altitude payload also observed time-dispersed arrivals in the electron flux and perturbations in the electric and magnetic field components, which are indicative of Alfven waves.

Kaeppler, S. R.↗
NASA NTRS2008

Preliminary Development and Testing of a Self-Injecting Gallium MPD Thruster

Discharge current and terminal voltage measurements were performed on a gallium electromagnetic thruster at discharge currents in the range of 20-54 kA. It was found that the arc impedance has a value of 6-7 m(Omega) at peak current. The absence of high-frequency oscillations in the terminal voltage trace indicates lack of the "onset" condition often seen in MPD arcs, suggesting that a sufficient number of charge carriers are present for current conduction. The mass ablated per pulse was not measured experimentally; however the mass flow rate was calculated using an ion current assumption and an anode power balance. Measurement of arc impedance predicts a temperature of 3.5 eV which from Saha equilibrium corresponds to Z = 2.0 - 3.5, and assuming Z = 2 yields an Isp of 3000 s and thrust efficiency of 50%.

Thomas, Robert E.↗
NASA NTRS1992

The 1992 NASA Langley Measurement Technology Conference: Measurement Technology for Aerospace Applications in High-Temperature Environments

An intensive 2-day conference to discuss the current status of measurement technology in the areas of temperature/heat flux, stress/strain, pressure, and flowfield diagnostics for high temperature aerospace applications was held at Langley Research Center, Hampton, Virginia, on April 22 and 23, 1993. Complete texts of the papers presented at the Conference are included in these proceedings.

Singh, Jag J.↗
DOE OSTI2024

Evaluation of Radiography for TRISO Buffer Layer Density Measurement

Tristructural isotropic (TRISO) fuel particles consist of a central uranium-bearing kernel and a series of coating layers designed to retain fission products and to ensure fuel performance. Several parameters such as thickness and density must be measured for these coating layers to show that they conform with fuel specifications. Current methods for measuring the density of pyrolytic carbon and silicon carbide layers (liquid gradient density column) and the buffer layer (mercury porosimetry) generate Resource Conservation and Recovery Act (RCRA) radiological-mixed waste. In addition, measurement of buffer and inner pyrolytic carbon layer densities require hot sampling or interrupted coating runs and the mercury porosimetry method used for buffer density measurement only measures the mean buffer density, not the interparticle distribution. A new approach has been evaluated to measure the density of coating layers in TRISO particles based on the dependence of x-ray attenuation in radiographs on material density. This method does not generate RCRA mixed waste, measures density on a particle-by-particle basis, and in principle is capable of measuring the density of all coating layers in a single process. Initial results using thinned TRISO particle sections to evaluate radiography measurement of density as a quality control characterization method are reported herein. In this work, the primary focus is on measurement of the density of the buffer layer; however, with appropriate calibration the method should be applicable to other coating layers. Improvements to the initial method and a full demonstration of the method on the remaining coating layers may be pursued as a future effort.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1978

Cross sections relevant to gamma ray astronomy

Gamma-ray production cross sections were measured for protons and alpha particles incident on targets consisting of nuclei of high cosmic abundance: C-12, N-14, O-16, Ne-20, Mg-24, Si-28 and Fe-56. Solid or gaseous targets were bombarded by monoenergetic beams of protons and alpha particles, and gamma rays were detected by two Ge(Li) detectors. The proton energy for each target was varied from threshold to about 24 MeV (lab); for alphas the range was from threshold to about 27 MeV. For most transitions, it was possible to measure the total cross section by placing the detectors at 30.5 deg and 109.9 deg where the fourth-order Legendre polynomial is zero. For the case of the 16O (E sub gamma = 6.13 MeV, multipolarity E3) cross sections, yields were measured at four angles. Absolute cross sections were obtained by integrating the beam current and by measuring target thicknesses and detector efficiencies. The Ge(Li) detector resolution was a few keV (although the peak widths were greater, due to Doppler broadening).

Dyer, P.↗
NASA NTRS2003

New Measurements of the Li, Be, and B Isotopes as a Test of Cosmic Ray Transport Models

Precise measurements of predominantly secondary cosmic-ray Li, Be, and B together with current well-measured production cross-sections for these isotopes help to improve our understanding of galactic cosmic ray propagation models. The Cosmic Ray Isotope Spectrometer (CRIS) on ACE has been measuring isotopic composition of cosmic rays since 1997 with high statistical precision. We present the isotopic abundances from CRIS and discuss these observations in the context of cosmic-ray transport models and previous cosmic-ray measurements.

deNolfo, Georgia A.↗
NASA NTRS2004

Evaluating the Emergency Notification Systems of the NASA White Sands Test

The problem was that the NASA Fire and Emergency Services did not know if the current emergency notification systems on the NASA White Sands Test Facility were appropriate for alerting the employees of an emergency. The purpose of this Applied Research Project was to determine if the current emergency notification systems of the White Sands Test Facility are appropriate for alerting the employees of an emergency. This was a descriptive research project. The research questions were: 1) What are similar facilities using to alert the employees of an emergency?; 2) Are the current emergency notification systems suitable for the community hazards on the NASA White Sands Test Facility?; 3) What is the NASA Fire and Emergency Services currently using to measure the effectiveness of the emergency notification systems?; and 4) What are the current training methods used to train personnel to the emergency notification systems at the NASA White Sands Test Facility? The procedures involved were to research other established facilities, research published material from credible sources, survey the facility to determine the facility perception of the emergency notification systems, and evaluate the operating elements of the established emergency notification systems for the facility. The results were that the current systems are suitable for the type of hazards the facility may endure. The emergency notification systems are tested frequently to ensure effectiveness in the event of an emergency. Personnel are trained and participate in a yearly drill to make certain personnel are educated on the established systems. The recommendations based on the results were to operationally improve the existing systems by developing and implementing one system that can overall notify the facility of a hazard. Existing procedures and training should also be improved to ensure that all personnel are educated on what to do when the emergency notification systems are activated.

Chavez, Alfred Paul↗