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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

OSSE observations of the Crab pulsar

We present results of the Compton Gamma-Ray Observatory (CGRO) Oriented Scintillation Spectrometer Experiment (OSSE) observations of the Crab pulsar, made during MJD 48373-48406 (1991 April 27 - 1991 May 30) and MJD 48798-48804 (1992 June 25 - 1992 July 1). Pulsar light curves and spectra over the approximately 0.05 to 10 MeV range are presented. The arrival time of the gamma-ray peak and the radio peak agree to within 30 microsec which is better than the approximately 300 microsec accuracy of the measurements. The overall pulse phase averaged spectrum in the 0.1 - 10 MeV range is well-fit by a power law of the form 0.05 x (E/0.13 MeV)exp(-(1.99 +/- 0.03)) photons/sq cm/s. The outer-gap model (with gap parameter equal to 0.46) provided to us by Ho agrees with the data to better than 20%. The spectra of the bridge and second peak are slightly harder than the first peak as measured by the hardness ratio (approximately 110 - 220 keV)/(approximately 50 - 105 keV): P1 = 0.54 +/- 0.01, P2 = 0.63 +/- 0.01, bridge = 0.68 +/- 0.03. The phase of the two peaks in the light curve is constant over the 50 - 550 keV range to within the accuracy of the measurements (better than 0.02 in phase). No evidence was found for variability of the light curve on timescales from 2 minutes (less than a factor of 1.8) to 1 year (less than a factor of 1.06), where these are 3 sigma upper limits. However, when we examine the historical database, we find, in agreement with Nolan et al. (1993), that there is evidence for a 13 year variation in the ratio of the intensity of peak 2 to peak 1. We show that if this is interpreted as being due to precession (which changes the relative view of the intrinsic gamma-ray pulse as seen on earth), the variation is consistent with models of neutron star structure. The optical data may be in conflict with the interpretation however. We found no statistically significant lines in the 50 - 550 keV range in the spectrum. The average 3 sigma upper limits in 10(exp -3) photons/sq cm/s for lines at 0.073, 0.078, 0.4, 0.44, 0.511, and 0.545 MeV are 0.3, 0.5, 0.6, 0.5, and 0.1.

Ulmer, M. P.↗
NASA NTRS2010

Human Factors Research for Space Exploration: Measurement, Modeling, and Mitigation

As part of NASA's Human Research Program, the Space Human Factors Engineering Project serves as the bridge between Human Factors research and Human Spaceflight applications. Our goal is to be responsive to the operational community while addressing issues at a sufficient level of abstraction to ensure that our tools and solutions generalize beyond the point design. In this panel, representatives from four of our research domains will discuss the challenges they face in solving current problems while also enabling future capabilities. Historically, engineering-dominated organizations have tended to view good Human Factors (HF) as a desire rather than a requirement in system design and development. Our field has made significant gains in the past decade, however; the Department of Defense, for example, now recognizes Human-System Integration (HSI), of which HF is a component, as an integral part of their divisions hardware acquisition processes. And our own agency was far more accepting of HF/HSI requirements during the most recent vehicle systems definition than in any prior cycle. Nonetheless, HF subject matter experts at NASA often find themselves in catch up mode... coping with legacy systems (hardware and software) and procedures that were designed with little regard for the human element, and too often with an attitude of we can deal with any operator issues during training. Our challenge, then, is to segregate the true knowledge gaps in Space Human Factors from the prior failures to incorporate best (or even good) HF design principles. Further, we strive to extract the overarching core HF issues from the point-design-specific concerns that capture the operators (and managers) attention. Generally, our approach embraces a 3M approach to Human Factors: Measurement, Modeling, and Mitigation. Our first step is to measure human performance, to move from subjective anecdotes to objective, quantified data. Next we model the phenomenon, using appropriate methods in our field, modifying them to suit the unique aspects of the space environment. Finally, we develop technologies, tools, and procedures to mitigate the decrements in human performance and capabilities that occur in space environments. When successful, we decrease risks to crew safety and to mission success. When extremely successful (or lucky), we devise generalizable solutions that advance the state of our practice. Our panel is composed of researchers from diverse domains of our project... from different boxes, if you will, of the Human Factors Analysis and Classification System (HFACS).

Kaiser, Mary K.↗
NASA NTRS2010

Modeling and Simulation of the ARES UPPER STAGE Transportation, Lifting, Stacking and Mating Operations Within the Vehicle Assembly Building at KSC

This viewgraph presentation describes the modeling and simulation of the Ares Upper Stage Transportation, lifting, stacking, and mating operations within the Vehicle Assembly Building (VAB) at Kennedy Space Center (KSC). An aerial view of KSC Launch Shuttle Complex, two views of the Delmia process control layout, and an upper stage move subroutine and breakdown are shown. An overhead image of the VAB and the turning basin along with the Pegasus barge at the turning basin are also shown. This viewgraph presentation also shows the actual design and the removal of the mid-section spring tensioners, the removal of the AFT rear and forward tensioners tie downs, and removing the AFT hold down post and mount. US leaving the Pegasus Barge, the upper stage arriving at transfer aisle, upper stage receiving/inspection in transfer aisle, and an overhead view of upper stage receiving/inspection in transfer aisle are depicted. Five views of the actual connection of the cabling to the upper stage aft lifting hardware are shown. The upper stage transporter forward connector, two views of the rotation horizontal to vertical, the disconnection of the rear bolt ring cabling, the lowering of the upper stage to the inspection stand, disconnection of the rear bolt ring from the upper stage, the lifting of the upper stage and inspection of AFT fange, and the transfer of upper stage in an integrated stack are shown. Six views of the mating of the upper stage to the first stage are depicted. The preparation, inspection, and removal of the forward dome are shown. The upper stage mated on the integrated stack and crawler is also shown. This presentation concludes with A Rapid Upper Limb Assessment (RULA) utilizing male and female models for assessing risk factors to the upper extremities of human beings in an actual physical environment.

Kromis, Phillip A.↗
NASA NTRS2018

Optimization of Thin-Film Solar Cells for Lunar Surface Operations

Thin-film solar cells have been in production for decades, but technology has only recently advanced enough to allow for comparable efficiencies to traditional rigid cells. Some of the benefits of thin-films, such as lighter weight and being foldable, are particularly advantageous to space applications since mass and volume are key considerations of any flight project. Using these thin-film cells in space, however, is outside of their ground-based design criteria. This requires special care to be taken in designing the power generation system of a spacecraft around a thin-film solar cell, particularly in regards to thermal management. Without the diffusion of an atmosphere to mitigate solar load, the temperature of the panels can rapidly exceed their design specification. In this paper a design solution is presented that allows for thin-film solar cells to be used in a robotic lunar lander. Due to the low thermal mass and in-plane conductivity of thin films, it is difficult to remove waste heat by any other method than radiation. On the lunar surface this means angling the arrays to increase their view factor to space, which has the negative consequence of decreasing their power generation. An optimization was developed to balance the heat rejection and power generation of the cells, using constraints on the maximum cell temperature and minimum spacecraft power requirements. The resulting solar panel angle was then used as an input to the Thermal Desktop model to verify the final panel temperatures.

Breeding, Shawn↗
NASA NTRS2011

jasonSWIR Calibration of Spectralon Reflectance Factor

Satellite instruments operating in the reflective solar wavelength region require accurate and precise determination of the Bidirectional Reflectance Factor (BRF) of laboratory-based diffusers used in their pre-flight and on-orbit radiometric calibrations. BRF measurements are required throughout the reflected-solar spectrum from the ultraviolet through the shortwave infrared. Spectralon diffusers are commonly used as a reflectance standard for bidirectional and hemispherical geometries. The Diffuser Calibration Laboratory (DCaL) at NASA's Goddard Space Flight Center is a secondary calibration facility with reflectance measurements traceable to those made by the Spectral Tri-function Automated Reference Reflectometer (STARR) facility at the National Institute of Standards and Technology (NIST). For more than two decades, the DCaL has provided numerous NASA projects with BRF data in the ultraviolet (UV), visible (VIS) and the Near infraRed (NIR) spectral regions. Presented in this paper are measurements of BRF from 1475nm to 1625nm obtained using an indium gallium arsenide detector and a tunable coherent light source. The sample was a 2 inch diameter, 99% white Spectralon target. The BRF results are discussed and compared to empirically generated data from a model based on NIST certified values of 6deg directional/hemispherical spectral reflectance factors from 900nm to 2500nm. Employing a new NIST capability for measuring bidirectional reflectance using a cooled, extended InGaAs detector, BRF calibration measurements of the same sample were also made using NIST's STARR from 1475nm to 1625nm at an incident angle of 0deg and at viewing angles of 40deg, 45deg, and 50deg. The total combined uncertainty for BRF in this ShortWave Infrared (SWIR) range is less than 1%. This measurement capability will evolve into a BRF calibration service in SWIR region in support of NASA remote sensing missions. Keywords: BRF, BRDF, Calibration, Spectralon, Reflectance, Remote Sensing.

Georgiev, Georgi T.↗
NASA NTRS2012

Water Detection Based on Color Variation

This software has been designed to detect water bodies that are out in the open on cross-country terrain at close range (out to 30 meters), using imagery acquired from a stereo pair of color cameras mounted on a terrestrial, unmanned ground vehicle (UGV). This detector exploits the fact that the color variation across water bodies is generally larger and more uniform than that of other naturally occurring types of terrain, such as soil and vegetation. Non-traversable water bodies, such as large puddles, ponds, and lakes, are detected based on color variation, image intensity variance, image intensity gradient, size, and shape. At ranges beyond 20 meters, water bodies out in the open can be indirectly detected by detecting reflections of the sky below the horizon in color imagery. But at closer range, the color coming out of a water body dominates sky reflections, and the water cue from sky reflections is of marginal use. Since there may be times during UGV autonomous navigation when a water body does not come into a perception system s field of view until it is at close range, the ability to detect water bodies at close range is critical. Factors that influence the perceived color of a water body at close range are the amount and type of sediment in the water, the water s depth, and the angle of incidence to the water body. Developing a single model of the mixture ratio of light reflected off the water surface (to the camera) to light coming out of the water body (to the camera) for all water bodies would be fairly difficult. Instead, this software detects close water bodies based on local terrain features and the natural, uniform change in color that occurs across the surface from the leading edge to the trailing edge.

Rankin, Arturo L.↗
NASA NTRS2019

Thermal Environment Modeling Practices for the Descent Trajectory of Lunar Landers

With the current push to send landers back to the moon, properly modeling the thermal environment for the descent is critical. Descent in this paper is described as: descending from low lunar orbit to touch down on surface. There are several challenges during this period, including: many electronics (such as battery, avionics, transponder, etc…) have higher heat loads due to higher power levels, a significant portion of the view factor to space has been blocked out by the moon making heat rejection less efficient, components that normally do not have direct line of sight to the sun may get exposure due to the lander rotating to align for descent, and thruster firing will dump more heat into the lander. All of these factors combine during the most critical phase of a lander mission make it essential that the thermal environment has been properly set up during design and analysis. This paper presents one method of setting up the thermal environment during descent in Thermal Desktop and will also include some tips and tricks.

Szerszen, Alexander↗
NASA NTRS1990

Canopy bidirectional reflectance dependence on leaf orientation

The dependence of the bidirectional reflectance (BR) on the inclination and azimuthal orientation of a leaf is analyzed, with the primary assumption that, in terms of both obscuration and shadowing, the entire canopy consists of the same leaves. The BR patterns of a dense canopy are examined as a function of canopy architecture. It is assumed that the leaves are opaque Lambertian reflectors, having identical orientation and relfecting properties throughout the canopy, and distributed randomly with respect to the the irradiation field and the viewing direction. Analytical expressions are presented and analyzed for the BR factor. It is noted that maximal BR occurs at large viewing zenith angles. A complex and often steep dependence of the BR on azimuthal location is reported, noting that the BR thus depends on the leaf azimuth as well as the zenith angle. It is concluded that the question of azimuthal distribution has to be addressed when conducting model inversions to infer canopy characteristics and architecture.

Brakke, Thomas W.↗
NASA NTRS1990

Validation of Earth Radiation Budget Experiment scanning radiometer data inversion procedures

Validation techniques were implemented in the inversion of scanner radiometer data to assess the accuracy of the top of atmosphere radiant fluxes. An evaluation of SW radiant flux standard deviations for the same scene type shows that they contribute about 6.0 W/sq m for viewing zenith angles less than 55 deg and can reach values of up to 17.6 W/sq m for larger zenith angles in the backward scanning position. Three-channel intercomparison results, presented as color graphic displays and histograms, effectively validate the radiance measurements and the spectral factors. Along-track data were used to validate limb-darkening models and showed good agreement with current ERBE models. These validation techniques were found to be very effective in assessing the quality of the radiant fluxes generated by the ERBE inversion algorithm.

Manalo, Natividad D.↗
NASA NTRS1979

Compensation for atmospheric effects in LANDSAT data

Preprocessing algorithms were developed to remove or reduce the variations in multispectral data caused by variations in Sun angle and by changes in the atmospheric aerosol and water vapor levels. The two most significant algorithms developed by using mathematical models to define interrelations between the required multiplicative and additive correction factors so that just a few statistical characteristics of a LANDSAT distribution model would be sufficient to drive the mathematical model and to calculate the preprocessing corrections are examined. These are the atmospheric correction (ATCOR) computer program and the XSTAR haze correction algorithm. Neither the ATCOR nor the XSTAR algorithm provides an explicit compensation for the effects of changing LANDSAT view angle. Development efforts are underway to address this aspect of the preprocessing problem.

Lambeck, P. F.↗
NASA NTRS1987

Preliminary design, analysis, and costing of a dynamic scale model of the NASA space station

The difficulty of testing the next generation of large flexible space structures on the ground places an emphasis on other means for validating predicted on-orbit dynamic behavior. Scale model technology represents one way of verifying analytical predictions with ground test data. This study investigates the preliminary design, scaling and cost trades for a Space Station dynamic scale model. The scaling of nonlinear joint behavior is studied from theoretical and practical points of view. Suspension system interaction trades are conducted for the ISS Dual Keel Configuration and Build-Up Stages suspended in the proposed NASA/LaRC Large Spacecraft Laboratory. Key issues addressed are scaling laws, replication vs. simulation of components, manufacturing, suspension interactions, joint behavior, damping, articulation capability, and cost. These issues are the subject of parametric trades versus the scale model factor. The results of these detailed analyses are used to recommend scale factors for four different scale model options, each with varying degrees of replication. Potential problems in constructing and testing the scale model are identified, and recommendations for further study are outlined.

Gronet, M. J.↗
NASA NTRS1986

Geometric-optical bidirectional reflectance modeling of a conifer forest canopy

A geometric-optical forest canopy model that treats conifers as cones casting shadows on a contrasting background explains the major anisotropies in bidirectional reflectance measurements of a conifer forest canopy. The model uses parallel-ray geometry to describe the illumination and viewing of conifers as three-dimensional cones. Both computer simulation and analytical closed-form expressions are implemented. The results show a good qualitative agreement with the directional reflectance measurements of the conifer stand, indicating that the three-dimensional nature of the canopy is a key factor in determining its directional reflectance.

Li, X.↗
NASA NTRS2016

High Precision Sunphotometer using Wide Dynamic Range (WDR) Camera Tracking

The NASA Ames Sun-photometer-Satellite Group, DOE, PNNL Atmospheric Sciences and Global Change Division, and NASA Goddards AERONET (AErosol RObotic NETwork) team recently collaborated on the development of a new airborne sunphotometry instrument that provides information on gases and aerosols extending far beyond what can be derived from discrete-channel direct-beam measurements, while preserving or enhancing many of the desirable AATS features (e.g., compactness, versatility, automation, reliability). The enhanced instrument combines the sun-tracking ability of the current 14-Channel NASA Ames AATS-14 with the sky-scanning ability of the ground-based AERONET Sunsky photometers, while extending both AATS-14 and AERONET capabilities by providing full spectral information from the UV (350 nm) to the SWIR (1,700 nm). Strengths of this measurement approach include many more wavelengths (isolated from gas absorption features) that may be used to characterize aerosols and detailed (oversampled) measurements of the absorption features of specific gas constituents. The Sky Scanning Sun Tracking Airborne Radiometer (3STAR) replicates the radiometer functionality of the AATS14 instrument but incorporates modern COTS technologies for all instruments subsystems. A 19-channel radiometer bundle design is borrowed from a commercial water column radiance instrument manufactured by Biospherical Instruments of San Diego California (ref, Morrow and Hooker)) and developed using NASA funds under the Small Business Innovative Research (SBIR) program. The 3STAR design also incorporates the latest in robotic motor technology embodied in Rotary actuators from Oriental motor Corp. having better than 15 arc seconds of positioning accuracy. Control system was designed, tested and simulated using a Hybrid-Dynamical modeling methodology. The design also replaces the classic quadrant detector tracking sensor with a wide dynamic range camera that provides a high precision solar position tracking signal as well as an image of the sky in the 45 field of view around the solar axis, which can be of great assistance in flagging data for cloud effects or other factors that might impact data quality.

aerosols↗
NASA NTRSDate not supplied

Hyperspectral Sounder Products: SiFSAP and ClimFiSP

Infrared hyperspectral sounders have demonstrated to provide very high value information for a range of weather and climate applications. Traditional retrieval algorithms of hyperspectral sounders use the ‘cloud clearing’ methodology in the retrieval process due to the lack of means to account for cloud scattering effect. The corresponding Level-2 data products are therefore limited by two major factors: the degradation of spatial resolution as compared with the native resolution of the instruments and the lack of ‘radiance closure’ that is critically needed for climate trend studies. The single field-of-view (FOV) sounder atmospheric products (SiFSAP) algorithm has been developed to supplement existing operational products. The SiFSAP algorithm uses the principal component based radiative transfer model (PCRTM) that is ultra-fast and has been extensively validated for the cloud scattering simulation capability. The cloud properties are physically retrieved along with profiles of temperature, moisture, and trace gases of interest, surface properties simultaneously by fitting single FOV spectral measurements. Therefore, SiFSAP ensure the radiometric consistency between the retrieved geophysical properties and the top-of-atmosphere (TOA) spectral measurements. This presentation provides a general introduction of SiFSAP and details about the physical retrieval algorithm. Also introduced here is a derivative data product of SiFSAP, the climate fingerprinting Sounder Products (ClimFiSP). ClimFiSP include the space-time averaged properties of key climate variables that are derived from the space-time averaged radiances via the spectral fingerprinting scheme. The spectral fingerprinting method allows a low latency data update on ClimFiSP following any potential calibration update on satellite measurements. ClimFiSP also include the rigorously defined uncertainty characterization for trends or anomalies of climate variables, being critical for the construction of long-term climate data record. Both SiFSAP and ClimFiSP will be available to users through NASA's Goddard Earth Sciences Data and Information Services Center (GES DISC).

Wan Wu↗
NASA NTRS1999

Effect of optical digitizer selection on the application accuracy of a surgical localization system-a quantitative comparison between the OPTOTRAK and flashpoint tracking systems

Application accuracy is a crucial factor for stereotactic surgical localization systems, in which space digitization camera systems are one of the most critical components. In this study we compared the effect of the OPTOTRAK 3020 space digitization system and the FlashPoint Model 3000 and 5000 3D digitizer systems on the application accuracy for interactive localization of intracranial lesions. A phantom was mounted with several implantable frameless markers which were randomly distributed on its surface. The target point was digitized and the coordinates were recorded and compared with reference points. The differences from the reference points represented the deviation from the "true point." The root mean square (RMS) was calculated to show the differences, and a paired t-test was used to analyze the results. The results with the phantom showed that, for 1-mm sections of CT scans, the RMS was 0.76 +/- 0. 54 mm for the OPTOTRAK system, 1.23 +/- 0.53 mm for the FlashPoint Model 3000 3D digitizer system, and 1.00 +/- 0.42 mm for the FlashPoint Model 5000 system. These preliminary results showed that there is no significant difference between the three tracking systems, and, from the quality point of view, they can all be used for image-guided surgery procedures. Copyright 1999 Wiley-Liss, Inc.

Non-NASA Center↗
NASA NTRS1987

Spacelab experiments on space motion sickness

Recent research results from ground and flight experiments on motion sickness and space sickness conducted by the Man Vehicle Laboratory are reviewed. New tools developed include a mathematical model for motion sickness, a method for quantitative measurements of skin pallor and blush in ambulatory subjects, and a magnitude estimation technique for ratio scaling of nausea or discomfort. These have been used to experimentally study the time course of skin pallor and subjective symptoms in laboratory motion sickness. In prolonged sickness, subjects become hypersensitive to nauseogenic stimuli. Results of a Spacelab-1 flight experiment are described in which four observers documented the stimulus factors for and the symptoms/signs of space sickness. The clinical character of space sickness differs somewhat from acute laboratory motion sickness. However SL-1 findings support the view that space sickness is fundamentally a motion sickness. Symptoms were subjectively alleviated by head movement restriction, maintenance of a familiar orientation with respect to the visual environment, and wedging between or strapping onto surfaces which provided broad contact cues confirming the absence of body motion.

Flight Experiment↗
NASA NTRS1987

Electromagnetic jets from compact objects

The possibility that at least some astrophysical jets are initially electromagnetic in origin is examined. Subsequent pick-up of ionization would convert such electromagnetic jets into hydrodynamic jets. In such a model, relativistic outflow is formed into highly collimated beams simply through the interaction with the surrounding medium. Forming jets under such general circumstances is encouraging in view of the range of scales that appear to be involved. The overall properties of such jets are largely determined by a single dimensionless parameter: the characteristic electrostatic potential drop rewritten as a particle Lorentz factor. Consequently, the determination of any one observable, such as the total power output, also determines the particle energy scale, the electromagnetic field strengths, etc.

Michel, F. Curtis↗
NASA NTRS1944

An Experimental Investigation of the Flow of Air in a Flat Broadening Channel

The wide use of diffusers, in various fields of technology, has resulted in several experimental projects to study the action and design of diffusers. Most of the projects dealt with steam (steam turbine nozzles). But diffusers have other applications - that is, ventilators, smoke ducts, air coolers, refrigeration, drying, and so forth. At present there is another application for diffusers in wind-tunnel design. Because of higher requirements and increased power of such installations more attention must be paid to the correctness of work and the decrease in losses due to every section of the tunnel. A diffuser, being one of the component parts of a tunnel , can in the event of faulty construction introduce considerable losses. Therefore, in the design of the new CAHI wind tunnel, it was suggested that an experimental study of diffusers be made, with a view to applying the results to wind tunnels. The experiments conducted by K. K. Baulin in the laboratories of CAHI upon models of diffusers of different cross sections, lengths, and angles of divergence, were a valuable source of experimental data. They were of no help, however, in reaching any conclusion regarding the optimum shape because of the complexity and diversity of the factors which all appeared simultaneously, thereby precluding the.study of the effects of any one factor separately. On the suggestion of the director of the CAHI,Prof. B. N. Ureff, it was decided to experiment on a two-dimensional diffuser model and determine the effect, of the angle of divergence. The author is acquainted with two experimental projects of like nature: the first was conducted with water, the other with air. The first of these works, although containing a wealth of experimental data, does not indicate the nature of flow or its relation to the angle of divergence. The second work is limited to four angles - that is, 12 deg, 24 deg, 45 deg, 90 deg. The study of this diffuser did not supply any information about the effect of smaller angles which, because of their advantages, are more commonly used, The author was able to acquaint himself with the second work only after the experiments were started. For these reasons, as well as because on the basis of those works no conclusion can be reached regarding the nature of flow distribution, of eddies, and so forth, experimental work was continued. The need for determining flow patterns follows from the fact that from them are determined methods of measurement - that is, the determination of velocities by means of the pitot tube, which, as is well known, gives correct indications only when placed with its axis parallel to the axis of flow. The data contained in this report were obtained from experiments conducted by the Aerodynamical Laboratories of the CAHI. The solutions to some. of the mathematical problems connected with the experiments are due to Prof. S. A, Chapligin.

Vedernikoff, A. N.↗