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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 181 records · Page 10

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NASA NTRS1991

Flow visualization of a rocket injector spray using gelled propellant simulants

A study was conducted at NASA-Lewis to compare the atomization characteristics of gelled and nongelled propellant simulants. A gelled propellant simulant composed of water, sodium hydroxide, and an acrylic acid polymer resin (as the gelling agent) was used to simulate the viscosity of an aluminum/PR-1 metallized fuel gel. Water was used as a comparison fluid to isolate the rheological effects of the water-gel and to simulate nongelled RP-1. The water-gel was injected through the central orifice of a triplet injector element and the central post of a coaxial injector element. Nitrogen gas flowed through the outer orifices of the triplet injector element and through the annulus of the coaxial injector element and atomized the gelled and nongelled liquids. Photographs of the water-gel spray patterns at different operating conditions were compared with images obtained using water and nitrogen. A laser light was used for illumination of the sprays. The results of the testing showed that the water sprays produced a finer and more uniform atomization than the water-gel sprays. Rheological analysis of the water-gel showed poor atomization caused by high viscosity of water-gel delaying the transition to turbulence.

Green, James M.↗

NASA NTRS1991

Flow visualization of a rocket injector spray using gelled propellant simulants

Green, James M.↗

NASA NTRS1995

Calculated quantum yield of photosynthesis of phytoplankton in the Marine Light-Mixed Layers (59 deg N, 21 deg W)

The quantum yield of photosynthesis (mol C/mol photons) was calculated at six depths for the waters of the Marine Light-Mixed Layer (MLML) cruise of May 1991. As there were photosynthetically available radiation (PAR) but no spectral irradiance measurements for the primary production incubations, three ways are presented here for the calculation of the absorbed photons (AP) by phytoplankton for the purpose of calculating phi. The first is based on a simple, nonspectral model; the second is based on a nonlinear regression using measured PAR values with depth; and the third is derived through remote sensing measurements. We show that the results of phi calculated using the nonlinear regreesion method and those using remote sensing are in good agreement with each other, and are consistent with the reported values of other studies. In deep waters, however, the simple nonspectral model may cause quantum yield values much higher than theoretically possible.

Carder, K. L.↗

NASA NTRS2003

The Plant Research Unit: An International Space Station Habitat

The Plant Research Unit (PRU) is one of six life science habitats being developed as part of the Space Station Biological Research Program. The PRU is designed for experiments in microgravity and will utilize the ISS Centrifuge Facility to provide gravity levels between microgravity and 29. The PRU will provide and control all aspects of a plant s needs in a nearly closed system. In other words, the shoot and root environments will not be open to the astronaut s environment except for experiment maintenance such as planting, harvesting and plant sampling. This also means that all lighting, temperature and humidity control, "watering," and air filtering and cleaning .must be done within strict limitations of volume, weight, power, and crew time while at the same time providing a very high level of reliability and a service life in excess of 10 years. The PRU will contain two plant chambers 31.5 cm tall, each with independent control of temperature, humidity, light level and photoperiod, CO2 level, nutrient and water delivery, and video and data acquisition. The PRU is currently in the preliminary design phase and a number of subsystem components have been prototyped for testing, including the temperature and humidity control systems, the plant chambers, the LED lighting system, the atmospheric control system and a variety of nutrient delivery systems. The LED prototype provides independent feedback control of 5 separate spectral bands and variable output between 0 and 1000 micro-mol sq m/sec. The water and nutrient delivery system (WNDS) prototypes have been used to test particulate based, thin film, and gel-based WNDS configurations.

Morrow, Robert↗

NASA NTRS2002

Coastal Research Imaging Spectrometer

The Coastal Research Imaging Spectrometer (CRIS) is an airborne remote-sensing system designed specifically for research on the physical, chemical, and biological characteristics of coastal waters. The CRIS includes a visible-light hyperspectral imaging subsystem for measuring the color of water, which contains information on the biota, sediment, and nutrient contents of the water. The CRIS also includes an infrared imaging subsystem, which provides information on the temperature of the water. The combination of measurements enables investigation of biological effects of both natural and artificial flows of water from land into the ocean, including diffuse and point-source flows that may contain biological and/or chemical pollutants. Temperature is an important element of such measurements because temperature contrasts can often be used to distinguish among flows from different sources: for example, a sewage outflow could manifest itself in spectral images as a local high-temperature anomaly.anomaly. Both the visible and infrared subsystems scan in "pushbroom" mode: that is, an aircraft carrying the system moves along a ground track, the system is aimed downward, and image data are acquired in acrosstrack linear arrays of pixels. Both subsystems operate at a frame rate of 30 Hz. The infrared and visible-light optics are adjusted so that both subsystems are aimed at the same moving swath, which has across-track angular width of 15. Data from the infrared and visible imaging subsystems are stored in the same file along with aircraft-position data acquired by a Global Positioning System receiver. The combination of the three sets of data is used to construct infrared and hyperspectral maps of scanned areas shown.

Source record↗

NASA NTRS2004

Coastal Research Imaging Spectrometer

The Coastal Research Imaging Spectrometer (CRIS) is an airborne remote sensing system designed specifically for research on the physical, chemical, and biological characteristics of coastal waters. The CRIS includes a visible-light hyperspectral imaging subsystem for measuring the color of water, which contains information on the biota, sediment, and nutrient contents of the water. The CRIS also includes an infrared imaging subsystem, which provides information on the temperature of the water. The combination of measurements enables investigation of biological effects of both natural and artificial flows of water from land into the ocean, including diffuse and point-source flows that may contain biological and/or chemical pollutants. Temperature is an important element of such measurements because temperature contrasts can often be used to distinguish among flows from different sources: for example, a sewage outflow could manifest itself in spectral images as a local high-temperature anomaly. Both the visible and infrared subsystems scan in pushbroom mode: that is, an aircraft carrying the system moves along a ground track, the system is aimed downward, and image data are acquired in across-track linear arrays of pixels. Both subsystems operate at a frame rate of 30 Hz. The infrared and visible-light optics are adjusted so that both subsystems are aimed at the same moving swath, which has across-track angular width of 15 . Data from the infrared and visible imaging subsystems are stored in the same file along with aircraft- position data acquired by a Global Positioning System receiver. The combination of the three sets of data is used to construct infrared and hyperspectral maps of scanned areas (see figure). The visible subsystem is based on a grating spectrograph and a rapid-readout charge-coupled-device camera. Images of the swatch are acquired in 256 spectral bands at wavelengths from 400 to 800 nm. The infrared subsystem, which is sensitive in a single wavelength band of 8 to 10 m, is based on a focal-plane array of HgCdTe photodetectors that are cooled to an operating temperature of 77 K by use of a closed-Stirling-cycle mechanical cooler. The nonuniformities of the HgCdTe photodetector array are small enough that the raw pixel data from the infrared subsystem can be used to recognize temperature differences on the order of 1 C. By use of a built-in blackbody calibration source that can be switched into the field of view, one can obtain bias and gain offset terms for individual pixels, making it possible to offset the effects of nonuniformities sufficiently to enable the measurement of temperature differences as small as 0.1 C.

Lucey, Paul G.↗

NASA NTRS1975

Airborne laser bathymeter

A description is given of a program concerned with the development and the evaluation of techniques for the measurement of water depth with a pulsed laser. Airborne laser bathymetry makes use of a light pulse which is sent downward. Information concerning the water depth is provided by the time interval observed between the arrival of the light pulse reflected from the water surface and the arrival of the pulse coming from the ocean floor. Details concerning the instrumentation used for the developed measurement method are discussed. Attention is also given to field experiments and aspects of system performance.

Cervenka, P. O.↗

NASA NTRS1975

Water quality indicators obtainable from aircraft and Landsat images and their use in classifying lakes

Equations describing the interaction of sunlight and skylight with the surface of a lake, particles in the water to the depth where light is extinguished, and lake bottom are presented, and the use of aircraft and Landsat images to derive water quality indicators on the basis of these interactions is discussed. A very clear, deep lake with a backscatter signal similar to that of distilled water is used as a reference standard. The degree of turbidity of other target lakes is determined by comparing their residual radiance with the clear lake standard and with the residual radiance of a lake whose turbidity has been determined from water samples. The relative and absolute strengths of residual radiance are used to determine the type and concentration of suspended material, respectively. Oil slicks are characterized by an increased specular reflectance component, decreased signal from the underlying water, and added backscatter signal from the oil volume.

Scherz, J. P.↗

NASA NTRS2004

Tropical Tropopause Structure and Processes as Observed with GPS Radio Occultation

The vertical temperature structure of the tropical atmosphere has been explained as controlled by the combined effect of three green house gases: water vapor, carbon dioxide, and ozone. Absorption by water vapor of the light reflected off the Earth's surface would determine the temperature lapse rate in the lower troposphere up to the bottom of the Tropical Transition Layer (TTL); radiative absorption by carbon dioxide would dominate the temperature lapse rate between the bottom of the TTL and the coldest point in the upper-troposphere, the cold point tropopause (CPT), and; absorption of incoming solar radiation by ozone would control the temperature above the CPT. The TTL region can thus be very sensitive to changes in the relative abundances of these greenhouse gases. In this contribution we describe the seasonal evolution of temperature profiles in the TTL and their longitudinal structure using GPS radio occultation.

global positioning system (GPS)↗

NASA NTRS1992

Purification system

A system for prolonging the life of a granulated activated charcoal (GAC) water treatment device is disclosed in which an ultraviolet light transparent material is used to constrain water to flow over carbon surfaces. It is configured to receive maximum flux from a UV radiation source for the purpose of preventing microbial proliferation on the carbon surfaces; oxidizing organic contaminants adsorbed from the water onto the carbon surfaces and from biodegradation of adsorbed microbial forms; disinfecting water; and oxidizing organic contaminants in the water.

Flanagan, David T.↗

NASA NTRS2002

Coastal Research Imaging Spectrometer

Lucey, Paul G.↗

NASA NTRS1999

An Evaluation of Oceanographic Optical Instruments and Deployment Methodologies

The primary objective of the Sea-viewing, Wide Field-of-view Sensor (SeaWiFS) Project is to produce water- leaving radiances with an uncertainty of 5% in clear-water regions and chlorophyll a concentrations within +/- 35% over the range of 0.05-50 mg/cu m. Any global mission, like SeaWiFS, requires validation data be submitted from a wide variety of investigators which places a significant challenge on quantifying the total uncertainty associated with the in situ measurements, because each investigator follows slightly different practices when it comes to implementing all of the steps associated with collecting field data, even those with a prescribed set of protocols. This study uses data from multiple cruises to quantify the uncertainties associated with implementing data collection procedures while utilizing differing in-water optical instruments and deployment methods. A comprehensive approach is undertaken and includes: (1) the use of a portable light source and in-water intercomparisons to monitor the stability of the field radiometers, (2) alternative methods for acquiring reference measurements, and (3) different techniques for making in-water profiles. The only system to meet the 5% radiometric objective of the SeaWiFS Project was a free-fall profiler using (relatively inexpensive) modular components, although a more sophisticated (and comparatively expensive) profiler using integral components was very close and only 1% higher. A relatively inexpensive system deployed with a winch and crane was also close, but the ship shadow contamination problem increased the total uncertainty to approximately 6.5%.

Hooker, Stanford B.↗

NASA NTRS2001

SIMBIOS Normalized Water-Leaving Radiance Calibration and Validation: Sensor Response, Atmospheric Corrections, Stray Light and Sun Glint

This Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) contract supports acquisition of match up radiometric and bio-optical data for validation of Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) and other ocean color satellites, and evaluation of uncertainty budgets and protocols for in situ measurements of normalized water leaving radiances.

Mueller, James L.↗

NASA NTRS1968

Atmospheric neutral points over water.

Positions of skylight neutral points for model of Rayleigh atmosphere and smooth water surface specularly reflecting light according to Fresnel law

Fraser, R. S.↗

NASA NTRS1983

Origin and evolution of the atmosphere of Venus

Implications for the origin and evolution of the terrestrial planets are drawn from a comparison of the Venus, earth and Mars atmosphere volatile inventories. Attention is given to the possible loss of an appreciable amount of water from Venus, in light of recent evidence for a 100-fold deuterium enrichment. Ar-40 and He-4 abundances suggest that outgassing has been inefficient for much of Venus's lifetime, in keeping with evidence for a lower level of tectonic activity on Venus than on the earth. Attention is also given to Venus's CO2 geochemistry. The picture now emerging is that of a Venus that began to evolve along a path similar to that of the earth, but suffered a catastrophic, runaway greenhouse effect early in its lifetime. How early the castastrophe occurred may be suggested by the presently low inventories of radiogenic argon and helium in its atmosphere.

Donahue, T. M.↗

NASA NTRS1985

Planetary surface processes: A review

The Earth's surface was shaped by a variety of processes, including volcanism, tectonism, impact cratering, and gradation. Solar System exploration and geological mapping showed that these processes operate on all the terrestrial planets. Gradation is a complex process that begins with weathering and erosion, continues with transport of weathered debris, and ends with deposition. Gradation works through the agents of gravity, wind, and water, and can shed light on planetary surface evolution. Rates of surface erosion vary with planet and must be considered in assessing ages of surface units based on impact crater frequency distributions. The products of gradation may substantially influence remote sensing signatures for determination of composition and must be taken into account in interpreting such data.

Greeley, R.↗

NASA NTRS1992

Testing the Li-Strahler four-component canopy reflectance model in the HAPEX-Sahel shrub savanna sites using ground reflectance data

The rate at which a light field decays in water is characterized by the diffuse attenuation coefficient k. The Li-Strahler discrete-object canopy reflectance model was tested in two sites, a shrub grass savanna and a degraded shrub savanna on bare soil, in the proposed HAPEX (Hydrologic Atmospheric Pilot Experiment) II/Sahel study area in Niger, West Africa. Average site reflectance was predicted for each site from the reflectances and cover proportions of four components: shrub canopy, background (soil or grass and soil), shaded canopy, and shaded background. Component reflectances were sampled in the SPOT wavebands using a hand-held radiometer. Predicted reflectance was compared to average site reflectance measured using the same radiometer mounted on a backpack with measurements recorded every 5 m along two 1-km transects, also in the SPOT (Systeme Probatoire d'Observation de la Terre) bands. Measurements and predictions were made for each of the three days during the summer growing season, approximately two weeks apart. Red, near infrared reflectance, and the NDVI (normalized difference vegetation index) were all predicted with a high degree of accuracy for the shrub/grass site and with reasonable accuracy for the degraded shrub site.

Franklin, J.↗

NASA NTRS1996

Leaf Area Influence on Surface Layer in a Deciduous Forest: Site Description - Part I

A study over a deciduous forest located in middle Massachusetts (USA) has been performed to examine the role of leaves in the forest-atmosphere interaction. Due to the seasonal presence of leaves, a deciduous forest is a 'good laboratory' to study this interaction. In this first part, a description of a 30 m micrometeorological tower as well a qualitative description of some meteorological parameters are presented. The presence of leaves affects the forest in several ways. There is a decrease of upward PAR (Photosynthetically Active Radiation) due to absorption of visible light in the canopy. Water vapor concentration increases, and the CO2 concentration decreases in the surface layer as the canopy starts to be foliated. The physical presence of the leaves is felt in other quantities such as the global albedo and the subcanopy environment.

Sakai, Ricardo K.↗