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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

NASA Tech Briefs, October 2008

Topics covered include: Control Architecture for Robotic Agent Command and Sensing; Algorithm for Wavefront Sensing Using an Extended Scene; CO2 Sensors Based on Nanocrystalline SnO2 Doped with CuO; Improved Airborne System for Sensing Wildfires; VHF Wide-Band, Dual-Polarization Microstrip-Patch Antenna; Onboard Data Processor for Change-Detection Radar Imaging; Using LDPC Code Constraints to Aid Recovery of Symbol Timing; System for Measuring Flexing of a Large Spaceborne Structure; Integrated Formation Optical Communication and Estimation System; Making Superconducting Welds between Superconducting Wires; Method for Thermal Spraying of Coatings Using Resonant-Pulsed Combustion; Coating Reduces Ice Adhesion; Hybrid Multifoil Aerogel Thermal Insulation; SHINE Virtual Machine Model for In-flight Updates of Critical Mission Software; Mars Image Collection Mosaic Builder; Providing Internet Access to High-Resolution Mars Images; Providing Internet Access to High-Resolution Lunar Images; Expressions Module for the Satellite Orbit Analysis Program Virtual Satellite; Small-Body Extensions for the Satellite Orbit Analysis Program (SOAP); Scripting Module for the Satellite Orbit Analysis Program (SOAP); XML-Based SHINE Knowledge Base Interchange Language; Core Technical Capability Laboratory Management System; MRO SOW Daily Script; Tool for Inspecting Alignment of Twinaxial Connectors; An ATP System for Deep-Space Optical Communication; Polar Traverse Rover Instrument; Expert System Control of Plant Growth in an Enclosed Space; Detecting Phycocyanin-Pigmented Microbes in Reflected Light; DMAC and NMP as Electrolyte Additives for Li-Ion Cells; Mass Spectrometer Containing Multiple Fixed Collectors; Waveguide Harmonic Generator for the SIM; Whispering Gallery Mode Resonator with Orthogonally Reconfigurable Filter Function; Stable Calibration of Raman Lidar Water-Vapor Measurements; Bimaterial Thermal Compensators for WGM Resonators; Root Source Analysis/ValuStream[Trade Mark] - A Methodology for Identifying and Managing Risks; Ensemble: an Architecture for Mission-Operations Software; Object Recognition Using Feature-and Color-Based Methods; On-Orbit Multi-Field Wavefront Control with a Kalman Filter; and The Interplanetary Overlay Networking Protocol Accelerator.

Source record↗
NASA NTRS1987

Image processing system to analyze droplet distributions in sprays

An image processing system was developed which automatically analyzes the size distributions in fuel spray video images. Images are generated by using pulsed laser light to freeze droplet motion in the spray sample volume under study. This coherent illumination source produces images which contain droplet diffraction patterns representing the droplets degree of focus. The analysis is performed by extracting feature data describing droplet diffraction patterns in the images. This allows the system to select droplets from image anomalies and measure only those droplets considered in focus. Unique features of the system are the totally automated analysis and droplet feature measurement from the grayscale image. The feature extraction and image restoration algorithms used in the system are described. Preliminary performance data is also given for two experiments. One experiment gives a comparison between a synthesized distribution measured manually and automatically. The second experiment compares a real spray distribution measured using current methods against the automatic system.

Bertollini, Gary P.↗
NASA NTRS1983

Mass analysis of neutral particles and ions released during electrical breakdowns on spacecraft surfaces

A specialized spectrometer was designed and developed to measure the mass and velocity distributions of neutral particles (molecules and molecular clusters) released from metal-backed Teflon and Kapton films. Promising results were obtained with an insulation breakdown initiation system based on a moveable contact touching the insulated surfaces. A variable energy, high voltage pulse is applied to the contact. The resulting surface damage sites can be made similar in size and shape to those produced by a high voltage electron beam system operating at similar discharge energies. The point discharge apparatus was used for final development of several high speed recording systems and for measurements of the composition of the materials given off by the discharge. Results with this apparatus show evolution of large amounts of fluorocarbon fragments from discharge through Teflon FEP, while discharges through Kapton produce mainly very light hydrocarbon fragments at masses below about 80 a.m.u.

Kendall, B. R. F.↗
NASA NTRS1992

Time-resolved far-field analysis of a high power single emitter laser diode

A system was developed which is capable of measuring the time-resolved far-field radiation patterns from a high-power semiconductor laser under intensity modulated conditions. Angular steering of the fundamental spatial mode was observed, with pointing variations as large as 0.5 deg, or 7.5 percent of the beamwidth, during the time of the optical pulse. The variations in pointing angle were directly related to gradients in the transverse index profile of the laser, which may oscillate based on lateral spatial hole burning of the gain and carrier density.

Cornwell, Donald M., Jr.↗
NASA NTRS1984

Partial Reflection Spaced Antenna Wind Measurements

The nature of partially reflecting (PR) irregularities is briefly reviewed and the techniques used in the PR spaced antenna method are discussed. The radars addressed use frequencies in the 2 to 6 MHz range operate in a pulse mode at vertical incidence. Radar system parameters including receiver dynamic range, coherent and incoherent detection, and post detection filtering are examined. Finally, data system parameters and real time analysis techniques are discussed.

Fraser, G. J.↗
NASA NTRS2000

The Geoscience Laser Altimeter System (GLAS) for the ICESAT Mission

The Laser In space Technology Experiment, Shuttle Laser Altimeter and the Mars Observer Laser Altimeter have demonstrated accurate measurements of atmospheric backscatter and Surface heights from space. The recent MOLA measurements of the Mars surface have 40 cm vertical resolution and have reduced the global uncertainty in Mars topography from a few km to about 5 m. The Geoscience Laser Altimeter System (GLAS) is a next generation lidar for Earth orbit being developed as part of NASA's Icesat Mission. The GLAS design combines a 10 cm precision surface lidar with a sensitive dual wavelength cloud and aerosol lidar. GLAS will precisely measure the heights of the Earth's polar ice sheets, establish a grid of accurate height profiles of the Earth's land topography, and profile the vertical backscatter of clouds and aerosols on a global scale. GLAS is being developed to fly on a small dedicated spacecraft in a polar orbit with a 590 630 km altitude at inclination of 94 degrees. GLAS is scheduled to launch in the summer 2001 and to operate continuously for a minimum of 3 years with a goal of 5 years. The primary mission for GLAS is to measure the seasonal and annual changes in the heights of the Greenland and Antarctic ice sheets. GLAS will continuously measure the vertical distance from orbit to the Earth's surface with 1064 nm pulses from a ND:YAG laser at a 40 Hz rate. Each 5 nsec wide laser pulse is used to produce a single range measurement, and the laser spots have 66 m diameter and about 170 m center-center spacings. When over land GLAS will profile the heights of the topography and vegetation. The GLAS receiver uses a 1 m diameter telescope and a Si APD detector. The detector signal is sampled by an all digital receiver which records each surface echo waveform with I nsec resolution and a stored echo record lengths of either 200, 400, or 600 samples. Analysis of the echo waveforms within the instrument permits discrimination between cloud and surface echoes. Ground based echo analysis permits precise ranging, determining the roughness or slopes of the surface as well as the vertical distributions of vegetation illuminated by the laser. Accurate knowledge of the laser beam's pointing angle is needed to prevent height biases when over sloped surfaces. For surfaces with 2 deg. slopes, knowledge of pointing angle of the beam's centroid to about 8 urad is needed to achieve 10 cm height accuracy. GLAS uses a stellar reference system (SRS) to determine the pointing angle of each laser firing relative to inertial space. The SRS uses a high precision star camera oriented toward local zenith and a gyroscope to determine the inertial orientation of the SRS optical bench. The far field pattern of each laser is measured pulse relative to the star camera with a laser reference system (LRS). Optically measuring each laser far field pattern relative to the orientation of the star camera and gyroscope permits the precise pointing angle of each laser pulse to be determined. GLAS will also determine the vertical distributions of clouds and aerosols by measuring the vertical profile of laser energy backscattered by the atmosphere at both 1064 and 532 nm. The 1064 nm measurements use the Si APD detector and profile the height and vertical structure of thicker clouds. The measurements at 532 nm use new highly sensitive photon counting, detectors, and measure the height distributions of very thin Clouds and aerosol layers. With averaging these can be used to determine the height of the planetary boundary layer. The instrument design and expected performance will be discussed.

Abshire, James B.↗
NASA NTRS1971

Dynamic errors in strapdown inertial navigation systems

Motion-induced errors in strapdown inertial navigation systems are discussed. The errors generated in single-degree-of-freedom gyros and accelerometers are treated in great detail. These sensor errors are related to errors at the system level and common pulse rebalance techniques are compared. Since instrument single transmission characteristics are found to be important, describing function analysis is applied to nonlinear pulse torqued inertial sensor loops, and the results are compared with simulations. Two means for reducing motion-induced errors are explored: (1) selection of inertial sensor parameters, and (2) active error compensation by measuring the environment, computing the errors generated, and correcting for them.

Source record↗
NASA NTRS1978

Imaging Proportional X-ray Counter for HEAO

The HEAO-B Imaging Proportional Counter (IPC) is an X-ray imaging instrument designed for use in the High Energy Astronomy Observatory - Mission B (HEAO-B) X-ray Telescope. It measures the spatial location of individual X-ray photons by the risetime method and energy of photons by pulse height analysis. The IPC can locate photons in the energy range 0.2 to 4 keV to within 1 mm and provides 5 bits of energy level information. Each measured X-ray event is also time tagged with 7 bits of temporal data. The IPC also includes an in-flight-calibration source and uses a gas control system that maintains the counter gas density constant to an accuracy of 0.25 percent.

Humphrey, A.↗
NASA NTRS1975

Engineering studies of vectorcardiographs in blood pressure measuring systems

The following projects involving cardiovascular instrumentation were conducted: (1) the development and fabrication of a three-dimensional display measurement system for vectorcardiograms, (2) the development and fabrication of a cardiovascular monitoring system to noninvasively monitor beat-by-beat the blood pressure and heart rate using aortic pulse wave velocity, (3) the development of software for an interactive system to analyze systolic time interval data, and (4) the development of microprocessor-based physiologic instrumentation, focussing initially on EKG rhythm analysis. Brief descriptions of these projects were given.

Mark, R. G.↗
NASA NTRS1986

Orbital elements of the binary X-ray pulsar GX 301-2

X-ray outbursts from GX 301-2 were observed with Hakucho on two occasions during April and May 1982 and with Tenma in April 1984. Pulse arrival times measured with Hakucho were combined with those previously measured with Ariel 5 and SAS 3. The joint timing analysis of these data sets yields an orbital period of 41.5 days as the only acceptable solution; this is consistent with the period derived from the X-ray flaring events of the source. The orbital elements of the binary system, established from the joint timing analysis, are presented. The orbital solution suggests that all the peaks of X-ray flares observed during the past 10 yr occur at the orbital period, but consistently appear about 1.4 days before the time of periastron passage of the X-ray star.

Sato, N.↗
NASA NTRS1992

Ranging performance of satellite laser altimeters

Topographic mapping of the earth, moon and planets can be accomplished with high resolution and accuracy using satellite laser altimeters. These systems employ nanosecond laser pulses and microradian beam divergences to achieve submeter vertical range resolution from orbital altitudes of several hundred kilometers. Here, we develop detailed expressions for the range and pulse width measurement accuracies and use the results to evaluate the ranging performances of several satellite laser altimeters currently under development by NASA for launch during the next decade. Our analysis includes the effects of the target surface characteristics, spacecraft pointing jitter and waveform digitizer characteristics. The results show that ranging accuracy is critically dependent on the pointing accuracy and stability of the altimeter especially over high relief terrain where surface slopes are large. At typical orbital altitudes of several hundred kilometers, single-shot accuracies of a few centimeters can be achieved only when the pointing jitter is on the order of 10 mu rad or less.

Gardner, Chester S.↗
NASA NTRS2003

Optical and Probe Diagnostics Applied to Reacting Flows

We plan to explore three major threads during the fellowship period. The first interrogates the flame synthesis of carbon nanotubes using aerosol catalysts. Laser light scattering will reveal changes in particle size at various heights above the burner. Analysis of the flame gas by mass spectroscopy will reveal the chemical composition of the mixture. Finally, absorption measurements will map the nanotube concentration within the flow. The second thread explores soot oxidation kinetics. Cavity ring-down absorption measurements of the carbonaceous aerosol can provide a measure of the mass concentration with time and, hence, an oxidation rate. Spectroscopic and direct probe measurements will provide the temperature of the system needed for subsequent modeling. The third thread will explore the details of turbulent flame dynamics. Laser induced incandescence will be applied to measurements of soot volume fraction in a 2-d configuration. Analysis of seed tracer particles by planar laser light MIE scattering will reveal the elemental fuel mixture fraction in the flames. Cavity ring-down spectroscopy, a pulsed transient absorption method, will determine the instantaneous mass loading and its fluctuation. Finally, fluorescence measurements will investigate the formation of PAH's in these flames.

Ticich, Thomas M.↗
NASA NTRS1978

Doppler lidar processing for atmospheric turbulence measurements

A Doppler lidar is described, its processing methods are characterized, and two alternate techniques are considered. The described system uses a CO2 laser transmitting at 10.6 microns and a bank of narrow band filters for the spectrum analysis. Typical results obtained with this system are presented. The two alternate techniques involve computation of the discrete spectrum by use of the discrete Fourier transform. The first technique involves single-pulse processing and incoherent integration, while the second technique performs coherent processing on the train of received pulses.

Polge, R. J.↗
NASA NTRS2010

Experimental Investigation and Analysis of an Annular Pogo Accumulator

An experimental investigation was conducted on a scaled annular pogo accumulator for the Ares I Upper Stage. The test article was representative of the LO2 feedline and preliminary accumulator design, and included multiple designs of a perforated ring connecting the accumulator to the core feedline flow. The system was pulse tested in water over a range of pulse frequency and flow rates. Time dependent measurements of pressure at various locations in the test article were used to extract system compliance, inertance, and resistance. Results indicate a significant deviation from standard orifice flow theory and suggest a strong dependence on feedline average velocity. In addition, several CFD analyses were conducted to investigate the details of the time variant flow field. Both two-dimensional and three-dimensional simulations were performed with time varying boundary conditions used to represent system pulsing. The CFD results compared well with the sub-scale results and demonstrated the influence of feedline average velocity on the flow into and out of the accumulator

Peugeot, John↗
NASA NTRS2011

Experimental Investigation and Analysis of an Annular Pogo Accumulator

An experimental investigation was conducted on a scaled annular pogo accumulator for the Ares I Upper Stage. The test article was representative of the LO2 feedline and preliminary accumulator design, and included multiple designs of a perforated ring connecting the accumulator to the core feedline flow. The system was pulse tested in water over a range of pulse frequency and flow rates. Time dependent measurements of pressure at various locations in the test article were used to extract system compliance, inertance, and resistance. Preliminary results indicated a significant deviation from standard orifice flow theory and suggest a strong dependence on feedline average velocity. In addition, several CFD analyses were conducted to investigate the details of the time variant flow field. Both two-dimensional and three-dimensional simulations were performed with time varying boundary conditions used to represent system pulsing. The CFD results compared well with the sub-scale results and demonstrated the influence of feedline average velocity on the flow into and out of the accumulator. This paper presents updated results of the investigation including a parametric design space for determining resistance characteristics. Using the updated experimental results a new scaling relationship has been defined for shear flow over a cavity. A comparison of sub-scale and full scale CFD simulations provided early verification of the scaling of the fluid flowfield and resistance characteristics.

Peugeot, John↗
NASA NTRS1991

A C-band scatterometer for remote sensing the air-sea interface

An airborne C-band scatterometer system (C-Scat) has been developed to remotely sense ocean surface winds and improve upon the present understanding of the relationship between normalized radar cross section (NRCS) and ocean surface roughness influences such as wind speed and direction, wave height and slope, and the air-sea temperature difference. The scatterometer utilizes a unique frequency-steered microstrip array antenna that is installed beneath the fuselage of an airplane. The antenna is electronically scanned in elevation, from 20 deg to 50 deg off-nadir, and mechanically spins in azimuth. The system is capable of measuring ocean surface NRCS from altitudes as high as 25,000 ft. The transmitter and receiver operate from 4.98 to 5.7 GHz. System parameters such as transmitter pulse width, pulse repetition frequency, output power level, and receiver bandwidth are programmable. Received signals can be averaged and displayed in real time and are stored on a Winchester disk drive for post-flight analysis. Preliminary flight data that demonstrates the instrument's performance is presented.

Mclaughlin, David J.↗
NASA NTRS1993

Three-body effects in the PSR 1257+12 planetary system

A detailed theoretical analysis of the three-body effects in the putative planetary system of PSR 1257+12 is presented. Ways in which these effects are manifested in the pattern of pulse arrival times are discussed; the dominant perturbation is described as a modulation of the phases of the near-sinusoidal signals of the two planetary companions. Explicit formulas for the time dependence of the oscillating orbital elements that are needed for an improved timing model for this system are provided. If a timing model with fixed, independent Keplerian orbits continues to be used for the timing analysis, and if two planets are indeed orbiting this pulsar, then the three-body effects should become detectable by means of a growth in the postfit residuals as more observations are accumulated. If the typical error in the pulse arrival time measurements is about 10 microsec, the amplitude of the postfit residuals will increase beyond this level with three to five years of timing observations.

Malhotra, Renu↗
NASA NTRS1985

Evidence for long-term variability in the ultra high energy photon flux from Cygnus X-3

A time-correlation analysis of atmospheric Cerenkov pulses by a wide-angle photomultiplier system was previously shown to have present in it a nonrandom component which seemed associated with the Right Ascension (RA) range approx. 20+or-04h. A recent examination of multi-muon events recorded by a photon-decay detector shows a similar time-dependent effect, closely matching the previous results, supporting the suggestion that the effect is of cosmic origin. However, even though Cyg. X-3 lies well inside the region of peak intensity, it does not seem possible to ascribe to it the whole effect, for the implied photon flux appears too large to be reconciled to various gamma-ray measurements of Cyg. X-3. The original data were subjected to a phase-histogram analysis and it as found that only 2.5% of overall recorded data are compatible with a phase-dependent emission from Cyg. X-3. Assuming these events to be gamma rays yields a detected flux of (2.6 + or - 0.3) x 10 to the minus 12th power gamma cm -2s-1 above 5 x 10 to the 14th power eV. Comparing this value with more recent ultra high energy (UHE) photon data from the same source, it is suggested that the available data generally favor a long-term reduction in the Cyg. X-3 inferred luminosity ( 10 to the 13th power eV) by a factor of (1.8 + or - 0.3) per year.

Bhat, C. L.↗