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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Secure Mass Measurements From Transit Timing: 10 Kepler Exoplanets Between 3 and 8 M⊕ With Diverse Densities and Incident Fluxes

We infer dynamical masses in eight multiplanet systems using transit times measured from Keplerʼs complete data set, including short-cadence data where available. Of the 18 dynamical masses that we infer, 10 pass multiple tests for robustness. These are in systems Kepler-26 (KOI-250), Kepler-29 (KOI-738), Kepler-60 (KOI-2086), Kepler-105 (KOI-115), and Kepler-307 (KOI-1576). Kepler-105 c has a radius of 1.3 R(sub ⨁) and a density consistent with an Earth-like composition. Strong transit timing variation (TTV) signals were detected from additional planets, but their inferred masses were sensitive to outliers or consistent solutions could not be found with independently measured transit times, including planets orbiting Kepler-49 (KOI-248), Kepler-57 (KOI-1270), Kepler-105 (KOI-115), and Kepler-177 (KOI-523). Nonetheless, strong upper limits on the mass of Kepler-177 c imply an extremely low density of ∽0.1 g cm(exp −3). In most cases, individual orbital eccentricities were poorly constrained owing to degeneracies in TTV inversion. For five planet pairs in our sample, strong secular interactions imply a moderate to high likelihood of apsidal alignment over a wide range of possible eccentricities. We also find solutions for the three planets known to orbit Kepler-60 in a Laplace-like resonance chain. However, nonlibrating solutions also match the transit timing data. For six systems, we calculate more precise stellar parameters than previously known, enabling useful constraints on planetary densities where we have secure mass measurements. Placing these exoplanets on the mass–radius diagram, we find that a wide range of densities is observed among sub-Neptune-mass planets and that the range in observed densities is anticorrelated with incident flux.

Individual stars↗
NASA NTRS1997

Radiation dosimetry measurements with real time radiation monitoring device (RRMD)-II in Space Shuttle STS-79

The real-time measurement of radiation environment was made with an improved real-time radiation monitoring device (RRMD)-II onboard Space Shuttle STS-79 (S/MM#4: 4th Shuttle MIR Mission, at an inclination angle of 51.6 degrees and an altitude of 250-400km) for 199 h during 17-25 September, 1996. The observation of the detector covered the linear energy transfer (LET) range of 3.5-6000 keV/micrometer. The Shuttle orbital profile in this mission was equivalent to that of the currently planned Space Station, and provided an opportunity to investigate variations in count rate and dose equivalent rate depending on altitude, longitude, and latitude in detail. Particle count rate and dose equivalent rate were mapped geographically during the mission. Based on the map of count rate, an analysis was made by dividing whole region into three regions: South Atlantic Anomaly (SAA) region, high latitude region and other regions. The averaged absorbed dose rate during the mission was 39.3 microGy/day for a LET range of 3.5-6000 keV/micrometer. The corresponding average dose equivalent rates during the mission are estimated to be 293 microSv/day with quality factors from International Commission on Radiological Protection (ICRP)-Pub. 60 and 270 microSv/day with quality factors from ICRP-Pub. 26. The effective quality factors for ICRP-Pub. 60 and 26 are 7.45 and 6.88, respectively. From the present data for particles of LET > 3.5keV/micrometer, we conclude that the average dose equivalent rate is dominated by the contribution of galactic cosmic ray (GCR) particles. The dose-detector depth dependence was also investigated.

manned↗
NASA NTRS1976

Thermocouple time constant measurement by cross power spectra

A method of measuring thermocouple time constants is outlined which requires Fourier signal processing. In this method, two thermocouples of differing time constants are placed in a gas flow as closely as possible to one another, and the time constant of the first thermocouple is determined directly from the extremum of the imaginary part of the ratio of the ensemble averaged cross-power spectrum to the ensemble averaged auto-power spectrum of that thermocouple. A coherence function is given for assuring the quality of the data, and results are presented for an experimental test of the method. Some problems with the method are briefly noted.

Strahle, W. C.↗
NASA NTRS1972

Measures of time in astronomy.

Astronomically-important measures of time are discussed with their definitions, their intended purposes, and areas of viability or obsolescence. Several different kinds of year are defined. Earth rotation time is described in terms of sidereal and solar time and in terms of universal time (UT) for which four different levels are defined corresponding to different approximations of 'uniform' time. The formal definition of ephemeris time, consisting of a defined rate and epoch, is discussed and some unorthodox criticisms are presented. Uses of broadcast time are noted. In the discussion of what measure of time should be used in astronomical applications, it is stated that, at present, all dynamical applications should use a measure of time based on atomic clock time.

Mulholland, J. D.↗
NASA NTRS1989

Measuring Fracture Times Of Ceramics

Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

Shlichta, Paul J.↗
NASA NTRS1976

Comparison of seven performance measures in a time-delayed manipulation task

Real-time performance data was collected during a pick-up task carried out with a Rancho master-slave manipulator using a minicomputer-based data taker. In addition to the usual task-time measurements, computer algorithms to integrate the energy consumed and to count and time the number of moves were implemented. In addition to these measures, several derived measures such as the fraction of time moving (MRATIO) and mean time per move (MBAR) were obtained in an off-line analysis. Preliminary results of the time delay experiment indicate that two new measures, MRATIO and MBAR, are almost an order of magnitude more sensitive than task time, the conventional measure, in determining performance changes with transmission delays in the range from 0.0 to 1.0s.

Hill, J. W.↗
NASA NTRS1988

Measuring Time-Averaged Blood Pressure

Device measures time-averaged component of absolute blood pressure in artery. Includes compliant cuff around artery and external monitoring unit. Ceramic construction in monitoring unit suppresses ebb and flow of pressure-transmitting fluid in sensor chamber. Transducer measures only static component of blood pressure.

Rothman, Neil S.↗
NASA NTRS2011

Time delay and distance measurement

A method for measuring time delay and distance may include providing an electromagnetic radiation carrier frequency and modulating one or more of amplitude, phase, frequency, polarization, and pointing angle of the carrier frequency with a return to zero (RZ) pseudo random noise (PN) code. The RZ PN code may have a constant bit period and a pulse duration that is less than the bit period. A receiver may detect the electromagnetic radiation and calculate the scattering profile versus time (or range) by computing a cross correlation function between the recorded received signal and a three-state RZ PN code kernel in the receiver. The method also may be used for pulse delay time (i.e., PPM) communications.

Abshire, James B.↗
NASA NTRS2003

Time-Resolved Measurements in Optoelectronic Microbioanalysis

A report presents discussion of time-resolved measurements in optoelectronic microbioanalysis. Proposed microbioanalytical laboratory-on-a-chip devices for detection of microbes and toxic chemicals would include optoelectronic sensors and associated electronic circuits that would look for fluorescence or phosphorescence signatures of multiple hazardous biomolecules in order to detect which ones were present in a given situation. The emphasis in the instant report is on gating an active-pixel sensor in the time domain, instead of filtering light in the wavelength domain, to prevent the sensor from responding to a laser pulse used to excite fluorescence or phosphorescence while enabling the sensor to respond to the decaying fluorescence or phosphorescence signal that follows the laser pulse. The active-pixel sensor would be turned on after the laser pulse and would be used to either integrate the fluorescence or phosphorescence signal over several lifetimes and many excitation pulses or else take time-resolved measurements of the fluorescence or phosphorescence. The report also discusses issues of multiplexing and of using time-resolved measurements of fluorophores with known different fluorescence lifetimes to distinguish among them.

Bearman, Gregory↗
NASA NTRS1993

Adaptive median filtering for preprocessing of time series measurements

A median (L1-norm) filtering program using polynomials was developed. This program was used in automatic recycling data screening. Additionally, a special adaptive program to work with asymmetric distributions was developed. Examples of adaptive median filtering of satellite laser range observations and TV satellite time measurements are given. The program proved to be versatile and time saving in data screening of time series measurements.

Paunonen, Matti↗
NASA NTRS2004

Time-Average Measurement of Velocity, Density, Temperature, and Turbulence Using Molecular Rayleigh Scattering

Measurement of time-averaged velocity, density, temperature, and turbulence in gas flows using a nonintrusive, point-wise measurement technique based on molecular Rayleigh scattering is discussed. Subsonic and supersonic flows in a 25.4-mm diameter free jet facility were studied. The developed instrumentation utilizes a Fabry-Perot interferometer to spectrally resolve molecularly scattered light from a laser beam passed through a gas flow. The spectrum of the scattered light contains information about velocity, density, and temperature of the gas. The technique uses a slow scan, low noise 16-bit depth CCD camera to record images of the fringes formed by Rayleigh scattered light passing through the interferometer. A kinetic theory model of the Rayleigh scattered light is used in a nonlinear least squares fitting routine to estimate the unknown parameters from the fringe images. The ability to extract turbulence information from the fringe image data proved to be a challenge since the fringe is broadened by not only turbulence, but also thermal fluctuations and aperture effects from collecting light over a range of scattering angles. Figure 1 illustrates broadening of a Rayleigh spectrum typical of flow conditions observed in this work due to aperture effects and turbulence for a scattering angle, chi(sub s), of 90 degrees, f/3.67 collection optics, mean flow velocity, u(sub k), of 300 m/s, and turbulent velocity fluctuations, sigma (sub uk), of 55 m/s. The greatest difficulty in processing the image data was decoupling the thermal and turbulence broadening in the spectrum. To aid in this endeavor, it was necessary to seed the ambient air with smoke and dust particulates; taking advantage of the turbulence broadening in the Mie scattering component of the spectrum of the collected light (not shown in the figure). The primary jet flow was not seeded due to the difficulty of the task. For measurement points lacking particles, velocity, density, and temperature information could reliably be recovered, however the turbulence estimates contained significant uncertainty. Resulting flow parameter estimates are presented for surveys of Mach 0.6, 0.95, and 1.4 jet flows. Velocity, density, and temperature were determined with accuracies of 5 m/s, 1.5%, and 1%, respectively, in flows with no particles present, and with accuracies of 5 m/s, 1-4%, and 2% in flows with particles. Comparison with hotwire data for the Mach 0.6 condition demonstrated turbulence estimates with accuracies of about 5 m/s outside the jet core where Mie scattering from dust/smoke particulates aided in the estimation of turbulence. Turbulence estimates could not be recovered with any significant accuracy for measurement points where no particles were present.

Mielke, Amy F.↗
DOE OSTI2025

PickerXL, A Large Deep Learning Model to Measure Arrival Times from Noisy Seismic Signals

Precisely measuring seismic arrival times is a labor-intensive task but is critical for both earthquake monitoring and subsurface imaging. Recently published deep learning models have demonstrated superior performance compared to traditional automatic approaches for picking arrival times. Although existing deep learning models have shown promising results, further advancements are necessary as their performance is not yet satisfactory especially when applied to new regions and station networks. Increasing model size has led to improved performance in other machine learning applications. Here, we aimed to investigate whether enlarging deep learning models can increase performance on accepted benchmarks. We trained three models of varying sizes, small (1X), medium (4X), and large (16X), using globally distributed local and regional earthquake signals and background noise waveforms from a benchmark dataset, Stanford Earthquake Dataset. Our results indicate that the largest model (PickerXL) outperforms both the smaller models and Seisbench implementation of the PhaseNet model, which has the same number of parameters as our small model. The PickerXL model’s enhanced capacity to extract complex patterns from seismograms contributes to its superior arrival picking abilities compared to the smaller model.

Chai, Chengping [Oak Ridge National Laboratory (OR↗
NASA NTRS1994

Real-time thickness measurement of MCC ablator material

One of the most favorable characteristics of the Space Shuttle Program is the reusability of two of its primary components: the orbiter itself and the Solid Rocket Boosters (SRB). The SRB's provide the primary source of propulsion for the Space Shuttle during take-off after which they are recovered for refurbishment and reuse. During refurbishment, the SRB's are stripped of all remaining ablative (heat resistant) coating. A new layer is applied to the appropriate sections (nose cone, frustum, forward skirt, and aft skirt). It is the process of applying the ablative coating which provided the impetus for this project. The thickness of this protective layer is considered to be of primary importance to the level of thermal protection provided. The objectives of this effort are to investigate possible techniques for measuring the thickness of MCC, and if possible to test the specific capabilities of those considered good candidates for implementation. The system would be able to take measurements in real-time as close to the spray gun as possible. This will allow the information to be used in the control of the process without an inordinate time delay between a measurement and its appropriate response. The thickness of the deposited material is to be measured with less than 0.100 in if uncertainty. This is the defined tolerance window for the ablator thickness. Finally, it must operate within the confines of the chamber which encloses the turntable, robot, and spray system, and therefore is required to be insensitive to, or at least maintainable in, that environment.

Greenway, R. Bryan, Jr.↗