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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 541 records · Page 30
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NASA NTRS1972

A solar-wind model including proton thermal anisotropy.

A relatively simple model is proposed to study the magnetohydrodynamic expansion of the solar wind. The interplanetary space is divided into an 'inner region' and an 'outer region.' In the inner region the solar wind is one-fluid and thermally isotropic. The solar-wind protons are assumed to be completely collisionless in the outer region. Thus the solar wind is two-fluid in nature, and the protons are thermally anisotropic in the outer region. It is assumed that throughout the interplanetary space electrons are thermally isotropic due to collisions or other processes. The electron heat flux is supposed to obey the well-known relationships that the flux is parallel to the magnetic-field vector and is directly proportional to the spatial derivative of the electron temperature.

Whang, Y. C.↗
NASA NTRS1979

DUMAND Summer Workshop, University of California, La Jolla, Calif., July 24-September 2, 1978, Proceedings. Volume 2 - UHE interactions, neutrino astronomy

The volume covers categories on inelastic neutrino scattering and the W-boson, and other ultra-high-energy processes, on pulsars, quasars and galactic nuclei, as well as other point sources and constants from gamma ray astronomy. Individual subjects include weak intermediate vector bosons and DUMAND, the Monte Carlo simulation of inelastic neutrino scattering in DUMAND, and Higgs boson production by very high-energy neutrinos. The observability of the neutrino flux from the inner region of the galactic disk, the diffuse fluxes of high-energy neutrinos, as well as the significance of gamma ray observations for neutrino astronomy are also among the topics covered.

Roberts, A.↗
NASA NTRS1983

Attitude Control by Localized Outgassing

Attitude control of levitated object achieved by using laser to vaporize selectively sublimate coating. Laser heats material that will sublime or outgas. To obtain torque reaction force vector from subliming material must not pass through center-of-mass of object. Laser provides beam suitable for controlling objects in noncontact manufacturing processes in acoustic levitation chambers.

Elleman, D. D.↗
NASA NTRS1994

Remote Sensing as a Landscape Epidemiologic Tool to Identify Villages at High Risk for Malaria Transmission

A landscape approach using remote sensing and Geographic Information System (GIS) technologies was developed to discriminate between villages at high and low risk for malaria transmission, as defined by adult Anopheles albimanus abundance. Satellite data for an area in southern Chiapas, Mexico were digitally processed to generate a map of landscape elements. The GIS processes were used to determine the proportion of mapped landscape elements surrounding 40 villages where An. albimanus data had been collected. The relationships between vector abundance and landscape element proportions were investigated using stepwise discriminant analysis and stepwise linear regression. Both analyses indicated that the most important landscape elements in terms of explaining vector abundance were transitional swamp and unmanaged pasture. Discriminant functions generated for these two elements were able to correctly distinguish between villages with high ind low vector abundance, with an overall accuracy of 90%. Regression results found both transitional swamp and unmanaged pasture proportions to be predictive of vector abundance during the mid-to-late wet season. This approach, which integrates remotely sensed data and GIS capabilities to identify villages with high vector-human contact risk, provides a promising tool for malaria surveillance programs that depend on labor-intensive field techniques. This is particularly relevant in areas where the lack of accurate surveillance capabilities may result in no malaria control action when, in fact, directed action is necessary. In general, this landscape approach could be applied to other vector-borne diseases in areas where: 1. the landscape elements critical to vector survival are known and 2. these elements can be detected at remote sensing scales.

Beck, Louisa R.↗
NASA NTRS2002

Rotor Wake Vortex Definition: Initial Evaluation of 3-C PIV Results of the Hart-II Study

An initial evaluation is made of extensive three-component (3C) particle image velocimetry (PIV) measurements within the wake across a rotor disk plane. The model is a 40 percent scale BO-105 helicopter main rotor in forward flight simulation. This study is part of the HART II test program conducted in the German-Dutch Wind Tunnel (DNW). Included are wake vortex field measurements over the advancing and retreating sides of the rotor operating at a typical descent landing condition important for impulsive blade-vortex interaction (BVI) noise. Also included are advancing side results for rotor angle variations from climb to steep descent. Using detailed PIV vector maps of the vortex fields, methods of extracting key vortex parameters are examined and a new method was developed and evaluated. An objective processing method, involving a center-of-vorticity criterion and a vorticity 'disk' integration, was used to determine vortex core size, strength, core velocity distribution characteristics, and unsteadiness. These parameters are mapped over the rotor disk and offer unique physical insight for these parameters of importance for rotor noise and vibration prediction.

Burley, Casey L.↗
NASA NTRS2003

Minimizing Segregation during the Controlled Directional Solidification of Dendric Alloys

Gravity-driven convection induced in the liquid by density gradients of temperature or composition disrupts uniform dendritic growth during controlled directional solidification and promotes severe macrosegregation. The solute-rich region about the dendrite tip appears to play a pivotal role in channel initiation. Allen and Hunt referred to this region as an "initial transient" or dynamic region constituting steep concentration gradients. Experimental investigation also point to the role the tip region plays in developing microstructure. Hellawell and co-workers showed that flow-through dendritic channels could be effectively disrupted, and segregation minimized, during the gradient freezing of bulk castings by rotating the melt through a slight angle with respect to Earth's gravity vector. Adapting this principle to controlled directional solidification, it has been shown" that segregation in dendritic alloys can be minimized, and properties improved, by processing the sample near horizontal in conjunction with a slow axial rotation of the crucible. It is postulated that the observed microstructural uniformity arises by maintaining the developing solute field about the dendrite tip. Solute rejected during vertical directional solidification will rise or sink parallel to the primary dendrite arms during axial rotation setting the stage for accumulation, instabilities, and segregation. In contrast, during horizontal growth, the rejected solute will sink or rise perpendicular to the primary dendrite. Now, in the presence of a slight axial rotation, solute that was initially sinking (or rising) will find itself above (or below) its parent dendrite, i.e., still about the tip region. The following is intended to experimentally demonstrate the viability of this concept in coordination with a model that gives predictive insight regarding solute distribution about growing dendrites. Alloys based on the lead-tin eutectic system were used in this study. The system is well characterized, the constituent metals are available in a very pure form, and the thermophysical properties are well known. During solidification of hypoeutectic alloys, e.g., 55 wt pct Pb, the primary dendrites reject the less dense tin, and for the hypereutectic alloys, e.g., 75 wt pct Sn, the primary dendrites reject denser lead. Alloys were prepared by melting appropriate amounts of lead and tin in a glass crucible after which the homogeneous liquid was sucked directly into 5-mm i.d. glass tubes. The sample tube, containing approximately 30 cm of alloy, was then mechanically driven into the directional solidification furnace assembly and positioned such that approx. 20 cm of the sample was remelted. Subsequently, directional solidification was initiated by withdrawing the sample through a water-cooled jacket at a constant growth velocity of 2 ,microns/s. After 5 to 6 cm of growth, the sample was quickly removed from the furnace and quenched in a water bath to preserve the solid-liquid interface. Samples were directionally solidified vertically upward, nearly horizontally, and some in conjunction with an applied axial rotation of the crucible. Temperature gradients at the solid-liquid interface were measured with an in-siru K-type thermocouple. Solidified samples were cut perpendicular and parallel to the growth direction and conventionally prepared for microscopic examination.

Grugel, Richard N.↗
NASA NTRS2000

Remote sensing and human health: new sensors and new opportunities

Since the launch of Landsat-1 28 years ago, remotely sensed data have been used to map features on the earth's surface. An increasing number of health studies have used remotely sensed data for monitoring, surveillance, or risk mapping, particularly of vector-borne diseases. Nearly all studies used data from Landsat, the French Systeme Pour l'Observation de la Terre, and the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer. New sensor systems are in orbit, or soon to be launched, whose data may prove useful for characterizing and monitoring the spatial and temporal patterns of infectious diseases. Increased computing power and spatial modeling capabilities of geographic information systems could extend the use of remote sensing beyond the research community into operational disease surveillance and control. This article illustrates how remotely sensed data have been used in health applications and assesses earth-observing satellites that could detect and map environmental variables related to the distribution of vector-borne and other diseases.

Satellite Communications↗
NASA NTRS2008

Multichannel Networked Phasemeter Readout and Analysis

Netmeter software reads a data stream from up to 250 networked phasemeters, synchronizes the data, saves the reduced data to disk (after applying a low-pass filter), and provides a Web server interface for remote control. Unlike older phasemeter software that requires a special, real-time operating system, this program can run on any general-purpose computer. It needs about five percent of the CPU (central processing unit) to process 20 channels because it adds built-in data logging and network-based GUIs (graphical user interfaces) that are implemented in Scalable Vector Graphics (SVG). Netmeter runs on Linux and Windows. It displays the instantaneous displacements measured by several phasemeters at a user-selectable rate, up to 1 kHz. The program monitors the measure and reference channel frequencies. For ease of use, levels of status in Netmeter are color coded: green for normal operation, yellow for network errors, and red for optical misalignment problems. Netmeter includes user-selectable filters up to 4 k samples, and user-selectable averaging windows (after filtering). Before filtering, the program saves raw data to disk using a burst-write technique.

Edmonds, Karina↗
NASA NTRS2011

Prominences: The Key to Understanding Solar Activity

Prominences are spectacular manifestations of both quiescent and eruptive solar activity. The largest examples can be seen with the naked eye during eclipses, making prominences among the first solar features to be described and catalogued. Steady improvements in temporal and spatial resolution from both ground- and space-based instruments have led us to recognize how complex and dynamic these majestic structures really are. Their distinguishing characteristics - cool knots and threads suspended in the hot corona, alignment along inversion lines in the photospheric magnetic field within highly sheared filament channels, and a tendency to disappear through eruption - offer vital clues as to their origin and dynamic evolution. Interpreting these clues has proven to be contentious, however, leading to fundamentally different models that address the basic questions: What is the magnetic structure supporting prominences, and how does so much cool, dense plasma appear in the corona? Despite centuries of increasingly detailed observations, the magnetic and plasma structures in prominences are poorly known. Routine measurements of the vector magnetic field in and around prominences have become possible only recently, while long-term monitoring of the underlying filament-channel formation process also remains scarce. The process responsible for prominence mass is equally difficult to establish, although we have long known that the chromosphere is the only plausible source. As I will discuss, however, the motions and locations of prominence material can be used to trace the coronal field, thus defining the magnetic origins of solar eruptions. A combination of observations, theory, and numerical modeling must be used to determine whether any of the competing theories accurately represents the physics of prominences. I will discuss the criteria for a successful prominence model, compare the leading models, and present in detail one promising, comprehensive scenario for prominence formation and evolution that could answer the two questions posed above.

Karpen, Judy T.↗
NASA NTRS2013

3D Radiative Transfer Effects in Multi-Angle/Multi-Spectral Radio-Polarimetric Signals from a Mixture of Clouds and Aerosols Viewed by a Non-Imaging Sensor

When observing a spatially complex mix of aerosols and clouds in a single relatively large field-of-view, nature entangles their signals non-linearly through polarized radiation transport processes that unfold in the 3D position and direction spaces. In contrast, any practical forward model in a retrieval algorithm will use only 1D vector radiative transfer (vRT) in a linear mixing technique. We assess the difference between the observed and predicted signals using synthetic data from a high-fidelity 3D vRT model with clouds generated using a Large Eddy Simulation model and an aerosol climatology. We find that this difference is signal--not noise--for the Aerosol Polarimetry Sensor (APS), an instrument developed by NASA. Moreover, the worst case scenario is also the most interesting case, namely, when the aerosol burden is large, hence hase the most impact on the cloud microphysics and dynamics. Based on our findings, we formulate a mitigation strategy for these unresolved cloud adjacency effects assuming that some spatial information is available about the structure of the clouds at higher resolution from "context" cameras, as was planned for NASA's ill-fated Glory mission that was to carry the APS but failed to reach orbit. Application to POLDER (POLarization and Directionality of Earth Reflectances) data from the period when PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) was in the A-train is briefly discussed.

APS↗
NASA NTRS1979

NASF transposition network: A computing network for unscrambling p-ordered vectors

The viewpoints of design, programming, and application of the transportation network (TN) is presented. The TN is a programmable combinational logic network that connects 521 memory modules to 512 processors. The unscrambling of p-ordered vectors to 1-ordered vectors in one cycle is described. The TN design is based upon the concept of cyclic groups from abstract algebra and primitive roots and indices from number theory. The programming of the TN is very simple, requiring only 20 bits: 10 bits for offset control and 10 bits for barrel switch shift control. This simple control is executed by the control unit (CU), not the processors. Any memory access by a processor must be coordinated with the CU and wait for all other processors to come to a synchronization point. These wait and synchronization events can be a degradation in performance to a computation. The TN application is for multidimensional data manipulation, matrix processing, and data sorting, and can also perform a perfect shuffle. Unlike other more complicated and powerful permutation networks, the TN cannot, if possible at all, unscramble non-p-ordered vectors in one cycle.

Lim, R. S.↗
NASA NTRS2018

Orion Optical Navigation Progress Toward Exploration: Mission 1

Optical navigation of human spacecraft was proposed on Gemini and implemented successfully on Apollo as a means of autonomously operating the vehicle in the event of lost communication with controllers on Earth. It shares a history with the "method of lunar distances" that was used in the 18th century and gained some notoriety after its use by Captain James Cook during his 1768 Pacific voyage of the HMS Endeavor. The Orion emergency return system utilizing optical navigation has matured in design over the last several years, and is currently undergoing the final implementation and test phase in preparation for Exploration Mission 1 (EM-1) in 2019. The software development is being worked as a Government Furnished Equipment (GFE) project delivered as an application within the Core Flight Software of the Orion camera controller module. The mathematical formulation behind the initial ellipse fit in the image processing is detailed in Christian. The non-linear least squares refinement then follows the technique of Mortari as an estimation process of the planetary limb using the sigmoid function. The Orion optical navigation system uses a body fixed camera, a decision that was driven by mass and mechanism constraints. The general concept of operations involves a 2-hour pass once every 24 hours, with passes specifically placed before all maneuvers to supply accurate navigation information to guidance and targeting. The pass lengths are limited by thermal constraints on the vehicle since the OpNav attitude generally deviates from the thermally stable tail-to-sun attitude maintained during the rest of the orbit coast phase. Calibration is scheduled prior to every pass due to the unknown nature of thermal effects on the lens distortion and the mounting platform deformations between the camera and star trackers. The calibration technique is described in detail by Christian, et al. and simultaneously estimates the Brown-Conrady coefficients and the Star Tracker/Camera interlock angles. Accurate attitude information is provided by the star trackers during each pass. Figure 1 shows the various phases of lunar return navigation when the vehicle is in autonomous operation with lost ground communication. The midcourse maneuvers are placed to control the entry interface conditions to the desired corridor for safe landing. The general form of optical navigation on Orion is where still images of the Moon or Earth are processed to find the apparent angular diameter and centroid in the camera focal plane. This raw data is transformed into range and bearing angle measurements using planetary data and precise star tracker inertial attitude. The measurements are then sent to the main flight computer's Kalman filter to update the onboard state vector. The images are, of course, collected over an arc to converge the state and estimate velocity. The same basic technique was used by Apollo to satisfy loss-of-comm, but Apollo used manual crew sightings with a vehicle-integral sextant instead of autonomously processing optical imagery. The software development is past its Critical Design Review, and is progressing through test and certification for human rating. In support of this, a hardware-in-the-loop test rig was developed in the Johnson Space Center Electro-Optics Lab to exercise the OpNav system prior to integrated testing on the Orion vehicle. Figure 2 shows the rig, which the test team has dubbed OCILOT (Orion Camera In the Loop Optical Testbed). Analysis performed to date shows a delivery that satisfies an allowable entry corridor as shown in Figure 3.

Holt, Greg N.↗
NASA NTRS1992

Development of a residual acceleration data reduction and dissemination plan

A major obstacle in evaluating the residual acceleration environment in an orbiting space laboratory is the amount of data collected during a given mission: gigabytes of data will be available as SAMS units begin to fly regularly. Investigators taking advantage of the reduced gravity conditions of space should not be overwhelmed by the accelerometer data which describe these conditions. We are therefore developing a data reduction and analysis plan that will allow principal investigators of low-g experiments to create experiment-specific residual acceleration data bases for post-flight analysis. The basic aspects of the plan can also be used to characterize the acceleration environment of earth orbiting laboratories. Our development of the reduction plan is based on the following program of research: the identification of experiment sensitivities by order of magnitude estimates and numerical modelling; evaluation of various signal processing techniques appropriate for the reduction, supplementation, and dissemination of residual acceleration data; and testing and implementation of the plan on existing acceleration data bases. The orientation of the residual acceleration vector with respect to some set of coordinate axes is important for experiments with known directional sensitivity. Orientation information can be obtained from the evaluation of direction cosines. Fourier analysis is commonly used to transform time history data into the frequency domain. Common spectral representations are the amplitude spectrum which gives the average of the components of the time series at each frequency and the power spectral density which indicates the power or energy present in the series per unit frequency interval. The data reduction and analysis scheme developed involves a two tiered structure to: (1) identify experiment characteristics and mission events that can be used to limit the amount of accelerator data an investigator should be interested in; and (2) process the data in a way that will be meaningful to the experiment objectives. A general outline of the plan is given.

Rogers, Melissa J. B.↗
NASA NTRS1980

Local distributed estimation

Based on partial differential equations of motion the closed form solution for the optimal estimation of a spatially continuous state vector is derived, using a continuously distributed sensor. Local control is shown to be the feedback that minimizes a quadratic performance index of sensor and process disturbances. A detailed example of the control of a string in tension is presented.

Schaechter, D. B.↗
NASA NTRS1982

Application of a recursive distortion estimator to the geodetic correction of thematic mapper imagery

It is pointed out that the higher resolution provided by the Thematic Mapper increases the demands on the accuracy needed by the ground processing in correcting for geodetic errors deriving from internal misalignments and uncertainties in the knowledge of spacecraft ephemeris and attitude. In addition, the Thematic Mapper will also process longer imagery intervals than previous missions. The recursive distortion estimator to be used is a Kalman filter. Here, a minimum variance spacecraft state error vector is estimated for known initial covariance of the elements of that vector and known image noise. Tests of the recursive distortion estimator with various spacecraft models carried out using a simulation of real world state vector dynamics are described. A determination is made of the density of control points needed to meet specified geometric correction requirements; it is expressed as a function of imagery interval length and control point measurement error.

Arnold, P.↗
NASA NTRS1984

Automated mesoscale wind fields derived from GOES satellite imagery

A new multispectral image-processing system for extracting mesoscale wind fields automatically from sequences of GOES imagery is described. This system can produce equivalent or superior cloud-wind estimates compared to the time-consuming manual methods used on various interactive meteorological processing systems. Analysis of automated mesoscale cloud winds yield an estimated random error value of less than 1 m/s and produces both regional and mesoscale vector wind-field structure and divergence patterns that are consistent in time and highly correlated with subsequent severe thunderstorm development. As an example, the system is here applied to SMS II five-minute imagery from April 24, 1975 and the results are compared with manually obtained ones.

Wilson, G. S.↗
NASA NTRS1989

Investigation of active regions at high resolution by balloon flights of the Solar Optical Universal Polarimeter (SOUP)

SOUP is a versatile, visible-light solar observatory, built for space or balloon flight. It is designed to study magnetic and velocity fields in the solar atmosphere with high spatial resolution and temporal uniformity, which cannot be achieved from the surface of the earth. The SOUP investigation is carried out by the Lockheed Palo Alto Research Laboratory, under contract to NASA's Marshall Space Flight Center. Co-investigators include staff members at a dozen observatories and universities in the U.S. and Europe. The primary objectives of the SOUP experiment are: to measure vector magnetic and velocity fields in the solar atmosphere with much better spatial resolution than can be achieved from the ground; to study the physical processes that store magnetic energy in active regions and the conditions that trigger its release; and to understand how magnetic flux emerges, evolves, combines, and disappears on spatial scales of 400 to 100,000 km. SOUP is designed to study intensity, magnetic, and velocity fields in the photosphere and low chromosphere with 0.5 arcsec resolution, free of atmospheric disturbances. The instrument includes: a 30 cm Cassegrain telescope; an active mirror for image stabilization; broadband film and TV cameras; a birefringent filter, tunable over 5100 to 6600 A with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera behind the filter; and a high-speed digital image processor.

Tarbell, T.↗
NASA NTRS1994

Radio-planetary from tie from Phobos-2 VLBI data

In an ongoing effort to improve the knowledge of the relative orientation (the 'frame tie') of the planetary ephemeris reference frame used in deep navigation and a second reference frame that is defined by the coordinates of a set of extragalactic radio sources, VLBI observations of the Soviet Phobos-2 spacecraft and nearby (in angle) radio sources were obtained at two epochs in 1989, shortly after the spacecraft entered orbit about Mars. The frame tie is an important systematic error source affecting both interplanetary navigation and the process of improving the theory of the Earth's orientation. The data from a single Phobos-2 VLBI session measure one component of the direction vector from Earth to Mars in the frame of the extragalactic radio sources (the 'radio frame'). The radio frame has been shown to be stable and internally consistent with an accuracy of 5 nrad. The planetary ephemeris reference frame has an internal consistency of approximately 15 nrad. The planetary and radio source reference frames were aligned prior to 1989 and measurements of occulations of the radio source 3C273 by the Moon. The Phobos-2 VLBI measurements provide improvement in the accuracy of two of the three angles describing a general rotation between the planetary and radio reference frames. A complete set of measurements is not available because data acquisition was terminated prematurely by loss of spacecraft. The analysis of the two Phobos-2 VLBI data sets indicates that, in the directions of the two rotation components determined by these data, the JPL planetary ephemeris DE200 is aligned with the radio frame as adopted by the International Earth Rotation Service within an accuracy of 20-40 nrad, depending on direction. The limiting errors in the solutions for these offsets are spacecraft trajectory (20 nrad), instrumental biases (19 nrad), and dependence of quasar coordinates on observing frequency (24 nrad).

Hildebrand, C. E.↗