Search NASA⌕ Search

SEARCH · Search NASA

Results for “view factor”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1943

Antispin-Tail-Parachute Installations

Although antispin tail parachutes have been used successfully in spin demonstrations for some time, very little published information is available concerning the size of parachute, the bridle-line length, and the type and location of pack to use for particular airplane. The present paper is an attempt to supply data relating to these factors. The paper is in two parts. The first part reviews the principles of operation of the antispin parachutes, views the principles of operation of the antispin parachutes, summarized available information on actual installations, and discusses parachute loads and pack locations. The second part of the paper reports on systematic tests in the NACA-15-foot and 20-foot free-spinning tunnels at the Langley memorial Aeronautical Laboratory to determine the minimum size and the optimum bridle-line lengths for antispin tail parachutes for current military airplanes. It is concluded that airplanes weighing between 7500 and 14,000 pounds require parachutes 8 feet in diameter and bridle-line lengths between 20 and 50 feet. A positive-ejection mechanism is desirable to throw the parachute clear of the tail and to assure rapid opening. The pack and attachment point must be so located that the equipment will not foul the tail surfaces.

Seidman, Oscar↗
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 NTRS1982

Ultraheavy cosmic rays - HEAO-3 results

The instrumentation and results from the Heavy Nuclei experiment on the HEAO 3 satellite are described. Six independently analyzed dual-gap ionization chambers measured the energy loss of the cosmic rays while a Cerenkov counter with 8 independently analyzed photomultipliers viewed two sheets of Pilot 425 plastic in a white box. Trajectories of the cosmic ray nuclei were determined in multiwire ionization hodoscopes. Variations in abundances were observed to be imperfectly ordered in terms of the first ionization potential, and volatility was also ruled out as the controlling factor. A predicted drop in abundance after Ba-56 was found, along with another sharp fall above Pb-82. Only one actinide-type event was detected during the 14 mos of viewing, a result consistent with other findings but which testifies against r-process formation.

Israel, M. H.↗
NASA NTRS2001

Where to look? Automating attending behaviors of virtual human characters

This research proposes a computational framework for generating visual attending behavior in an embodied simulated human agent. Such behaviors directly control eye and head motions, and guide other actions such as locomotion and reach. The implementation of these concepts, referred to as the AVA, draws on empirical and qualitative observations known from psychology, human factors and computer vision. Deliberate behaviors, the analogs of scanpaths in visual psychology, compete with involuntary attention capture and lapses into idling or free viewing. Insights provided by implementing this framework are: a defined set of parameters that impact the observable effects of attention, a defined vocabulary of looking behaviors for certain motor and cognitive activity, a defined hierarchy of three levels of eye behavior (endogenous, exogenous and idling) and a proposed method of how these types interact.

NASA Discipline Space Human Factors↗
NASA NTRS2008

Seeking Augmented Information Content Concerning Diurnal Precipitation Achieved by Combining TRMM-PR and CloudSat-CPR Radar Data Sets

The CloudSat satellite's Cloud Profiling Radar (CPR) is a highly sensitive 94 GHz (W-band) nadir viewing radar system flown in retrograde sun synchronous orbit useful for determining the vertical structure of cloud hydrometeors down to sensitivity of approx. -30 dBZ reflectivity factor. Given this sensitivity, it is possible to unambiguously measure precipitation rates in clouds over a spectrum extending from approx. 0.08 - 3.0 mm hr (sup -1) down to altitudes of 0.5 km with approx.0.25 km vertical binning. This enables an effective means to measure a great deal of the drizzle and light rain spectrum. However, because of its near-polar sunsynchronous orbit, CloudSat cannot sample the diurnal cycle of precipitation, nor with its nadir-only CPR view can it obtain a high duty cycle in sampling precipitation at fixed local times over fixed positions. On the other hand, the TRMM satellite, which is flown in a non-sunsynchronous 35-degree inclined orbit carrying the 13.8 GHz KU-band Precipitation Radar (PR) scanning through nadir over an approx. 225 km swath, can sample both the diurnal cycle and with a much improved duty cycle relative to CloudSat. Moreover, the PR and CPR have the same 0.25 km vertical binning capability. The PR's greatest shortcoming is its approx. +17 dBZ sensitivity, which eliminates the possibility of measuring rain rates below -0.3-0.5 mm hr(sup -1), which can involve rainfall accumulations of up to 50% of the total over some regions. This begs the question of whether by combining CPR and PR data sets, whether it is possible to obtain an augmented measurement of the diurnal precipitation cycle. By collecting complimentary datasets during CloudSat and TRMM satellite orbit crossings within a delta t = 45-min proximity window, it is possible to demonstrate that whenever TRMM detects a precipitation signal, the correlations along the vertical axis between the reflectivities acquired from the CPR and PR are in inverse proportion to the magnitude of the delta t proximity window. By taking advantage of these underlying correlations, it is possible to develop a functional which can be used to broaden the reflectivity spectrum, concomitantly the rain rate spectrum, of the PR measurements based on the inherently broader reflectivity spectrum of the CPR at the lower reflectivity end of the spectrum, concomitantly at lighter rain rates. With the functional in place, it is then possible to produce synthetic CloudSat precipitation imagery over the PR track and thus over the diurnal time period. These augmented data are then used to study the spectral-vertical diurnal properties of precipitation over oceanic regions observed by TRMM.

Smith, Eric A.↗
DOE OSTI2024

A Three–Dimensional Nanoscale View of Electrocatalyst Degradation in Hydrogen Fuel Cells

The loss of platinum (Pt) electrochemically active surface area (ECSA) is a critical degradation mode that often becomes a limiting factor for heavy-duty proton exchange membrane fuel cell vehicles. High surface area carbon supports have been shown to improve Pt dispersion and limit detrimental ionomer-electrocatalyst interactions due to their large interior pore volume. Here, in this work, using automated scanning transmission electron tomography, the degradation of nanoparticles located on the interior versus exterior surfaces of the carbon support is compared following a catalyst-specific accelerated stress test (AST) of 90,000 voltage cycles between 0.6 V to 0.95 V. The results reveal a notable increase in median particle size for both interior and exterior Pt catalyst particles, with a slightly higher increase in particle size distribution and loss of specific surface area for the particles located on the exterior carbon surface. The fraction of Pt nanoparticles that reside within the interior of the carbon support also increased following the AST test, accompanied by evidence of an increase in average carbon mesopore size. Here, the results shed light on the degradation mechanisms affecting electrochemical properties and the enhanced particle accessibility at lower relative humidity.

08 HYDROGEN↗
NASA NTRS1991

The spectral relationships between NEA and the meteorites: An overview using principal components analysis

One of the primary reservoirs for meteorites is probably the planet-crossing Aten, Apollo, and Amor asteroids. Comparing the spectral characteristics of these two populations with each other and with the spectra of the main belt asteroids would provide insight into the dynamical processes that deliver meteorites to Earth. One method for obtaining an overview of general relationships in a large spectral data set is the statistical technique of principal components analysis. This technique quantifies general spectral similarities and reprojects the data in a plot of major axes of variation where distance is a measure of relative similarity. A major caveat should be kept in mind, however, spectra are sensitive to particle size and viewing geometry effects, and near Earth asteroids (NEA's) are probably significantly different from main belt asteroids in both these factors. The analysis was restricted to the spectral range of ECAS filters and included 116 meteorite spectra from the Gaffey (1976) survey and 417 asteroids from the Zellner et. al. (1985) survey of which 13 are planet-crossers. Although thirteen asteroids are not much of a sample on which to base conclusions, a few inferences can be drawn from this exercise. First, the NEA spectral characteristics are, on average, more consistent with the spectra of meteorites than are the main belt asteroids. Second, the S-type NEA's tend to be spectrally more similar to the ordinary chondrite meteorites than the main belt S-types. This suggests that the planet-crossing S-types do not represent the spectral range of the main belt S-type population and that the planet-crossing S-types are on average more like the ordinary chondrites than the main belt S-types. Third, the only direct asteroidal ordinary chondrite analog, the Q-type asteroid, 1862 Apollo, plots well within the field of the ordinary chondrite meteorites and represents the most common meteorite fall type. Finally, it is interesting that the planet-crossing asteroids occupy similar PCA space with the general trend of the meteorites while most of the main belt objects are offset from the meteorites in statistical space.

Britt, D. T.↗
NASA NTRS2008

Scripting Module for the Satellite Orbit Analysis Program (SOAP)

This add-on module to the SOAP software can perform changes to simulation objects based on the occurrence of specific conditions. This allows the software to encompass simulation response of scheduled or physical events. Users can manipulate objects in the simulation environment under programmatic control. Inputs to the scripting module are Actions, Conditions, and the Script. Actions are arbitrary modifications to constructs such as Platform Objects (i.e. satellites), Sensor Objects (representing instruments or communication links), or Analysis Objects (user-defined logical or numeric variables). Examples of actions include changes to a satellite orbit ( v), changing a sensor-pointing direction, and the manipulation of a numerical expression. Conditions represent the circumstances under which Actions are performed and can be couched in If-Then-Else logic, like performing v at specific times or adding to the spacecraft power only when it is being illuminated by the Sun. The SOAP script represents the entire set of conditions being considered over a specific time interval. The output of the scripting module is a series of events, which are changes to objects at specific times. As the SOAP simulation clock runs forward, the scheduled events are performed. If the user sets the clock back in time, the events within that interval are automatically undone. This script offers an interface for defining scripts where the user does not have to remember the vocabulary of various keywords. Actions can be captured by employing the same user interface that is used to define the objects themselves. Conditions can be set to invoke Actions by selecting them from pull-down lists. Users define the script by selecting from the pool of defined conditions. Many space systems have to react to arbitrary events that can occur from scheduling or from the environment. For example, an instrument may cease to draw power when the area that it is tasked to observe is not in view. The contingency of the planetary body blocking the line of sight is a condition upon which the power being drawn is set to zero. It remains at zero until the observation objective is again in view. Computing the total power drawn by the instrument over a period of days or weeks can now take such factors into consideration. What makes the architecture especially powerful is that the scripting module can look ahead and behind in simulation time, and this temporal versatility can be leveraged in displays such as x-y plots. For example, a plot of a satellite s altitude as a function of time can take changes to the orbit into account.

Carnright, Robert↗
NASA NTRS2010

Human Health and Performance Considerations for Exploration of Near-Earth Asteroids

This presentation will describe the human health and performance issues that are anticipated for the human exploration of near-Earth asteroids (NEA). Humans are considered a system in the design of any such deep-space exploration mission, and exploration of NEA presents unique challenges for the human system. Key factors that define the mission are those that are strongly affected by distance and duration. The most critical of these is deep-space radiation exposure without even the temporary shielding of a nearby large planetary body. The current space radiation permissible exposure limits (PEL) restrict mission duration to 3-10 months depending on age and gender of crewmembers and stage of the solar cycle. Factors that affect mission architecture include medical capability; countermeasures for bone, muscle, and cardiovascular atrophy during continuous weightlessness; restricted food supplies; and limited habitable volume. The design of a habitat that can maintain the physical and psychological health of the crew and support mission operations with limited intervention from Earth will require an integrated research and development effort by NASA s Human Research Program, engineering, and human factors groups. Limited abort and return options for an NEA mission are anticipated to have important effects on crew psychology as well as influence medical supplies and training requirements of the crew. Other important factors are those related to isolation, confinement, communication delays, autonomous operations, task design, small crew size, and even the unchanging view outside the windows for most of the mission. Geological properties of the NEA will influence design of sample handling and containment, and extravehicular activity capabilities including suit ports and tools. A robotic precursor mission that collects basic information on NEA surface properties would reduce uncertainty about these aspects of the mission as well as aid in design of mission architecture and exploration tasks.

Kundrot, Craig↗
NASA NTRS2011

The Role of Comets as Possible Contributors of Water and Prebiotic Organics to Terrestrial Planets

The question of exogenous delivery of organics and water to Earth and other young planets is of critical importance for understanding the origin of Earth's water, and for assessing the prospects for existence of Earth-like exo-planets. Viewed from a cosmic perspective, Earth is a dry planet yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen. Can comets have delivered Earth's water? The deuterium content of comets is key to ,assessing their role as contributors of water to Earth. Icy bodies today reside in two distinct reservoirs, the Oort Cloud and the Kuiper Disk (divided into the classical disk, the scattered disk, and the detached or extended disk populations). Orbital parameters can indicate the cosmic storage reservoir for a given comet. Knowledge of the diversity of comets within a reservoir assists in assessing their possible contribution to early Earth, but requires quantitative knowledge of their components - dust and ice. Strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical dispersion of an outer disk of icy planetesimals, imply that comets from KD and OC reservoirs should have diverse composition. The primary volatiles (native to the nucleus) provide the preferred metric for building a taxonomy for comets, and the number of comets so quantified is growing rapidly. Taxonomies based on native species (primary volatiles) are now beginning to emerge [1, 2, 3]. The measurement of cosmic parameters such as the nuclear spin temperatures for H2O, NH3 and CH4, and of enrichment factors for isotopologues (D/H in water and hydrogen cyanide, N-14/N-15 in CN and hydrogen cyanide) provide additional tests of the origin of cometary material. I will provide an overview of these aspects, and implications for the origin of Earth's water and prebiotic organics.

Mumma, Michael J.↗
NASA NTRS2011

Messengers from the Early Solar System - Comets as Carriers of Cosmic Information

Viewed from a cosmic perspective, Earth is a dry planet yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen. Can comets have delivered Earth s water? The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth s water, and for assessing the possible existence of exo-planets similar to Earth. Strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models, imply that comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition. The primary volatiles in comets (ices native to the nucleus) provide the preferred metric, and taxonomies based on them are now beginning to emerge [1, 2, 3]. The measurement of cosmic parameters such as the nuclear spin temperatures for H2O, NH3, and CH4, and of enrichment factors for isotopologues (D/H in water and hydrogen cyanide, N-14/N-15 in CN and hydrogen cyanide) provide additional important tests for the origin of cometary material.

Mumma, Michael J.↗
NASA NTRS2012

Messengers from the Early Solar System - The Similarity and Diversity of Comets

Viewed from a cosmic perspective, Earth is a dry planet yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen. Can comets have delivered Earth's water? The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth's water, and for assessing the possible existence of exo-planets similar to Earth. Strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models, imply that comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition. The primary volatiles in comets (ices native to the nucleus) provide the preferred metric, and taxonomies based on them are now beginning to emerge [1,2,3]. The measurement of cosmic parameters such as the nuclear spin temperatures for H2O, NH3, and CH4, and of enrichment factors for isotopologues (D/H in water and hydrogen cyanide, N-14/N-15 in CN and hydrogen cyanide provide additional important tests for the origin of cometary material. I will provide an overview of these aspects, and their implications for the origin of Earth's water and prebiotic organics.

Mumma, Michael J.↗
NASA NTRS2011

Dual Electron Spectrometer for Magnetospheric Multiscale Mission: Results of the Comprehensive Tests of the Engineering Test Unit

The Magnetospheric Multiscale mission (MMS) is designed to study fundamental phenomena in space plasma physics such as a magnetic reconnection. The mission consists of four spacecraft, equipped with identical scientific payloads, allowing for the first measurements of fast dynamics in the critical electron diffusion region where magnetic reconnection occurs and charged particles are demagnetized. The MMS orbit is optimized to ensure the spacecraft spend extended periods of time in locations where reconnection is known to occur: at the dayside magnetopause and in the magnetotail. In order to resolve fine structures of the three dimensional electron distributions in the diffusion region (reconnection site), the Fast Plasma Investigation's (FPI) Dual Electron Spectrometer (DES) is designed to measure three dimensional electron velocity distributions with an extremely high time resolution of 30 ms. In order to achieve this unprecedented sampling rate, four dual spectrometers, each sampling 180 x 45 degree sections of the sky, are installed on each spacecraft. We present results of the comprehensive tests performed on the DES Engineering & Test Unit (ETU). This includes main parameters of the spectrometer such as energy resolution, angular acceptance, and geometric factor along with their variations over the 16 pixels spanning the 180-degree tophat Electro Static Analyzer (ESA) field of view and over the energy of the test beam. A newly developed method for precisely defining the operational space of the instrument is presented as well. This allows optimization of the trade-off between pixel to pixel crosstalk and uniformity of the main spectrometer parameters.

Avanov, Levon A.↗
NASA NTRS2012

Comets as Messengers from the Early Solar System - Emerging Insights on Delivery of Water, Nitriles, and Organics to Earth

The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth's volatiles, and for assessing the possible existence of exo-planets similar to Earth. Viewed from a cosmic perspective, Earth is a dry planet, yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen and analogous isotopic enrichments in atmospheric nitrogen and noble gases are also seen. Why is this so? What are the implications for Mars? For icy Worlds in our Planetary System? For the existence of Earth-like exoplanets? An exogenous (vs. outgassed) origin for Earth's atmosphere is implied, and intense debate on the relative contributions of comets and asteroids continues - renewed by fresh models for dynamical transport in the protoplanetary disk, by revelations on the nature and diversity of volatile and rocky material within comets, and by the discovery of ocean-like water in a comet from the Kuiper Belt (cf., Mumma & Charnley 2011). Assessing the creation of conditions favorable to the emergence and sustenance of life depends critically on knowledge of the nature of the impacting bodies. Active comets have long been grouped according to their orbital properties, and this has proven useful for identifying the reservoir from which a given comet emerged (OC, KB) (Levison 1996). However, it is now clear that icy bodies were scattered into each reservoir from a range of nebular distances, and the comet populations in today's reservoirs thus share origins that are (in part) common. Comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition, resulting from strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models of early radial transport and mixing with later dispersion of the final cometary nuclei into the long-term storage reservoirs. The inclusion of material from the natal interstellar cloud is probable, for comets formed in the outer solar system.

Mumma, Michael J.↗
NASA NTRS1979

Atmospheric scattering corrections to solar radiometry

Whenever a solar radiometer is used to measure direct solar radiation, some diffuse sky radiation invariably enters the detector's field of view along with the direct beam. Therefore, the atmospheric optical depth obtained by the use of Bouguer's transmission law (also called Beer-Lambert's law), that is valid only for direct radiation, needs to be corrected by taking account of the scattered radiation. This paper discusses the correction factors needed to account for the diffuse (i,e., singly and multiply scattered) radiation and the algorithms developed for retrieving aerosol size distribution from such measurements. For a radiometer with a small field of view (half-cone angle of less than 5 deg) and relatively clear skies (optical depths less than 0.4), it is shown that the total diffuse contribution represents approximately 1% of the total intensity.

Box, M. A.↗
NASA NTRS1972

Thermal design verification testing for the ATS-F and -G spacecraft.

There is a wide fluctuation in the internal power dissipation from the components within the earth viewing module (EVM). The electronic component functional reliability required for a two-to-five year mission is the most significant factor for the thermal design criteria. A mathematical thermal model of the EVM and the orbital environment is used to predict the performance of the thermal control system. Comparisons of the results obtained in chamber thermal balance tests with the data computed on the basis of the theoretical model provide the means for validating the thermal design.

Coyle, M.↗
NASA NTRS1984

Fundamental and harmonic emission in interplanetary type 2 radio bursts

Three interplanetary type II radio bursts which show two prominent and long duration bands in their dynamic spectra were analyzed in detail and compared to similar bands in meter wavelength type II events. These bands, which differ by a factor of about two in frequency, were interpreted in terms of fundamental and harmonic emission. The fundamental component has a greater average intensity than the harmonic, due largely to short intense brightenings. The fundamental spectral profile is more narrow than that of the harmonic, with harmonic band typically exhibiting a larger bandwidth to frequency ratio than the fundamental by a factor of two. The fundamental has a larger source size than the harmonic, 160 degrees versus 110 degrees, on average, as viewed from the Sun. Two of the events have source positions which correlate well with the associated flare positions.

Lengyel-Frey, D.↗
NASA NTRS1984

Observations of the high latitude far ultraviolet background in the 1040-1080 A band

Observations of the far ultraviolet background at high galactic latitudes in a band from 1040-1080 A were carried out with a rocket-borne 1 meter telescope and a 0.23 square degree field of view photometer. The photometer had a sharp cutoff shortward of 1040 A and a sensitivity at hydrogen Lyman alpha of a factor of 0.0001 below its sensitivity at 1060 A. A second photometer monitored geocoronal hydrogen Lyman alpha emission enabling an accurate evaluation of counts due to this background. The hydrogen Lyman alpha flux contributed only 17 percent of the total counts detected in the cosmic background detector. An upper limit to the emission in the 1040-1080 A band of 9700 photons per sq cm-s-sr-A is obtained. This upper limit is compared with previous measurements and theoretical predictions.

Bixler, J.↗