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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 NTRS1991

An evaluation of strategic behaviors in a high fidelity simulated flight task - Comparing primary performance to a figure of merit

The usual method of evaluating flight performance during a simulation is to collect as many primary performance measurements as possible. Then analyze all the measurements to find one sensitive to the manipulations imposed on the pilot during the scenario. Although this method can be useful, it is usually unreliable from one study to another. A simulation was conducted to test an integrated figure of merit (FOM) constructed using a standardized procedure. Pilots flew two full-mission scenarios in an instrument trainer with three degrees of motion freedom. The primary performance measurements selected assessed the pilot's performance in accuracy, smoothness, and activity. The results suggest that the integrated FOMs performed comparably to the primary performance measurements in determining which flight imposed the higher demands on the pilot. The standardized construction process allow adjustments to the FOM, so it can be used in different applications.

Bortolussi, Michael R.↗
NASA NTRS1991

Surface control techniques for the segmented primary mirror in the large lunar telescope

The large lunar telescope is a proposed moon-based telescope which incorporates a sixteen-meter segmented primary mirror. An error budget is developed for the active control system of the primary mirror. A control methodology for the primary mirror is then described which utilizes piston sensors for measuring the relative piston error between adjacent segments as well as a separate sensor which measures the tilt of each segment with respect to the pointing direction of the telescope. A trade study is conducted in which the following types of tilt sensors are examined to determine their applicability to this program: stellar wavefront sensors, such as a Hartmann-Shack or a shearing interferometer; holographic optical elements; interferometers; scanning systems; and some nonoptical systems which electronically measure the relative tilt between adjacent segments. In addition, two independent methods of quantitatively verifying the performance of the telescope using either a phase retrieval algorithm or an image sharpening technique, both of which are based on the quality of a stellar image, are presented.

Gleckler, Anthony D.↗
NASA NTRS1992

Thermal design optimization of a segmented GFRP primary reflector for a submillimeter telescope

Results are presented of a thermal design optimization study of the segmented GFRP primary reflector of the earth-orbiting Submillimeter Imager and Line Survey telescope. The paper examines the thermal requirements of the primary reflector and the thermal environment of the telescope and describes the thermal design of the primary reflector. Particular attention is given to the geometric math model and the thermal math model of the telescope. A summary for the steady-state thermal performance of the optimized design is presented, showing that the optimized design has reduced, by an order of magnitude, structural spatial temperature gradients, which were earlier shown to be the most significant obstacle in maintaining the required telescope figure accuracy.

Tsuyuki, Glenn T.↗
NASA NTRS1954

Experimental Investigation of Effects of Primary Jet Flow and Secondary Flow Through a Zero-length Ejector on Base and Boattail Pressures of a Body of Revolution at Free-stream Mach Numbers of 1.62, 1.93, and 2.41

An investigation was made at free-stream Mach numbers of 1.62, 1.93, and 2.41 to determine the effects of a primary jet and secondary air flow on the base pressure and pressures acting over the boattailsurface of a body of revolution for two secondary discharge areas. The Mach numbers of the primary nozzles were 1 and 3.23 with the secondary mass flow being varied from 0 to 10 percent of the primary mass flow. The ratio of jet stagnation temperature to tunnel stagnation temperature was about 0.96. The Reynolds number range of the investigation was from 2.1 x 10(6) to 2.9 x 10(6)based on body length. All testing was conducted with a turbulent boundary layer along the model. This report presents results obtained with zero-length ejector and covers jet static-pressure ratios from the jet-off condition to a maximum of about 128 for the sonic nozzle and to a maximum of about 9 for the supersonic nozzle.

O'Donnell, Robert M↗
NASA NTRS1992

Development of stitched/RTM composite primary structures

The goal of the NASA Advanced Composites Technology (ACT) Program is to provide the technology required to gain the full benefit of weight savings and performance offered by composite primary structures. Achieving the goal is dependent on developing composite materials and structures which are damage tolerant and economical to manufacture. Researchers at NASA LaRC and Douglas Aircraft Company are investigating stitching reinforcement combined with resin transfer molding (RTM) to create structures meeting the ACT program goals. The Douglas work is being performed under a NASA contract entitled Innovative Composites Aircraft Primary Structures (ICAPS). The research is aimed at materials, processes and structural concepts for application in both transport wings and fuselages. Empirical guidelines are being established for stitching reinforcement in primary structures. New data are presented in this paper for evaluation tests of thick (90-ply) and thin (16-ply) stitched laminates, and from selection tests of RTM composite resins. Tension strength, compression strength and post-impact compression strength data are reported. Elements of a NASA LaRC program to expand the science base for stitched/RTM composites are discussed.

Kullerd, Susan M.↗
NASA NTRS1996

Macrosegregation During Dendritic Arrayed Growth of Hypoeutectic Pb-Sn Alloys: Influence of Primary Arm Spacing and Mushy Zone Length

Thermosolutal convection in the dendritic mushy zone occurs during directional solidification of hypoeutectic lead tin alloys in a positive thermal gradient, with the melt on the top and the solid below. This results in macrosegregation along the length of the solidified samples. The extent of macrosegregation increases with increasing primary dendrite spacings for constant mushy zone length. For constant primary spacings, the macrosegregation increases with decreasing mushy zone length. Presence of convection reduces the primary dendrite spacings. However, convection in the interdendritic melt has significantly more influence on the spacings as compared with that in the overlying melt, which is caused by the solutal buildup at the dendrite tips.

Tewari, S. N.↗
NASA NTRS1996

Impact of Chromophoric Dissolved Organic Matter on UV Inhibition of Primary Productivity in the Sea

A model was developed to assess the impact of chromophoric dissolved organic matter (CDOM) on phytoplankton production within the euphotic zone. The rate of depth-integrated daily gross primary productivity within the euphotic zone was evaluated as a function of date, latitude, CDONI absorption characteristics, chlorophyll a (chl a) concentration, vertical stratification, and phytoplankton sensitivity to UV radiation (UVR). Results demonstrated that primary production was enhanced in the upper 30 m of the water column by the presence of CDOM, where predicted increases in production due to the removal of damaging UVR more than offset its reduction resulting from the absorption of photosynthetically usable radiation. At greater depths, where little UVR remained, primary production was always reduced due to removal by CDOM of photosynthetically usable radiation. When CDOM was distributed homogeneously within the euphotic zone, the integral over z [(GPP)(sub ez)], was reduced under most bio-optical (i.e. solar zenith angle, and CDOM absorption, and ozone concentration) and photophysiological production at depth was greater than the enhancement of production at the surface.

Arrigo, Kevin R.↗
NASA NTRS1997

Upwelling-Induced Primary Productivity in Coastal Waters of the Black Sea: Impact on Algorithms for Remote Sensing

This research program was a collaborative effort to investigate the impact of rapid changes in the water column during coastal upwelling, on biological and optical properties. These properties are important for constructing region or event-specific algorithms for remote sensing of pigment concentration and primary productivity and for comparing these algorithms with those used for the development of large scale maps from ocean color. We successfully achieved the primary objective of this research project which was to study in situ the dynamics of rapid spatial and temporal changes in properties of the water column during, coastal upwelling off the Crimean Coast in the Black Sea. The work was a collaborative effort between a group of biological and physical oceanographers from the Woods Hole Oceanographic Institution and from two oceanographic research institutions in the Crimea, Ukraine, located near the study site, the Marine Hydrophysical Institute (MHI) and the Institute of Biology of the Southern Seas (IBSS). The site was an ideal experimental model, both from a technical and economic standpoint, because of the predictable summer upwelling that occurs in the region and because of the availability of both a ship on call and laboratory and remote sensing facilities at the nearby marine institutes. We used a combination of shipboard measurements and remote sensing to investigate the physical evolution of rapid upwelling events and their impact on photoplankton and water column optical properties. The field work involved a two day cruise for mooring, deployment and a three day baseline survey cruise, followed by an eleven day primary cruise during, a summer upwelling event (anticipated by monitoring local winds and tracked by remote sensing imaging). An MHI ship was outfitted and used for these purposes.

Goldman, Joel C.↗
NASA NTRS1999

Development of a 12-Thrust Chamber Kerosene /Oxygen Primary Rocket Sub-System for an Early (1964) Air-Augmented Rocket Ground-Test System

Airbreathing/Rocket combined-cycle, and specifically rocket-based combined- cycle (RBCC), propulsion systems, typically employ an internal engine flow-path installed primary rocket subsystem. To achieve acceptably short mixing lengths in effecting the "air augmentation" process, a large rocket-exhaust/air interfacial mixing surface is needed. This leads, in some engine design concepts, to a "cluster" of small rocket units, suitably arrayed in the flowpath. To support an early (1964) subscale ground-test of a specific RBCC concept, such a 12-rocket cluster was developed by NASA's Marshall Space Flight Center (MSFC). The small primary rockets used in the cluster assembly were modified versions of an existing small kerosene/oxygen water-cooled rocket engine unit routinely tested at MSFC. Following individual thrust-chamber tests and overall subsystem qualification testing, the cluster assembly was installed at the U. S. Air Force's Arnold Engineering Development Center (AEDC) for RBCC systems testing. (The results of the special air-augmented rocket testing are not covered here.) While this project was eventually successfully completed, a number of hardware integration problems were met, leading to catastrophic thrust chamber failures. The principal "lessons learned" in conducting this early primary rocket subsystem experimental effort are documented here as a basic knowledge-base contribution for the benefit of today's RBCC research and development community.

Pryor, D.↗
NASA NTRS2001

Observations of Ocean Primary Productivity Using MODIS

Measuring the magnitude and variability of oceanic net primary productivity (NPP) represents a key advancement toward our understanding of the dynamics of marine ecosystems and the role of the ocean in the global carbon cycle. MODIS observations make two new contributions in addition to continuing the bio-optical time series begun with Orbview-2's SeaWiFS sensor. First, MODIS provides weekly estimates of global ocean net primary productivity on weekly and annual time periods, and annual empirical estimates of carbon export production. Second, MODIS provides additional insight into the spatial and temporal variations in photosynthetic efficiency through the direct measurements of solar-stimulated chlorophyll fluorescence. The two different weekly productivity indexes (first developed by Behrenfeld & Falkowski and by Yoder, Ryan and Howard) are used to derive daily productivity as a function of chlorophyll biomass, incident daily surface irradiance, temperature, euphotic depth, and mixed layer depth. Comparisons between these two estimates using both SeaWiFS and MODIS data show significant model differences in spatial distribution after allowance for the different integration depths. Both estimates are strongly dependence on the accuracy of the chlorophyll determination. In addition, an empirical approach is taken on annual scales to estimate global NPP and export production. Estimates of solar stimulated fluorescence efficiency from chlorophyll have been shown to be inversely related to photosynthetic efficiency by Abbott and co-workers. MODIS provides the first global estimates of oceanic chlorophyll fluorescence, providing an important proof of concept. MODIS observations are revealing spatial patterns of fluorescence efficiency which show expected variations with phytoplankton photo-physiological parameters as measured during in-situ surveys. This has opened the way for research into utilizing this information to improve our understanding of oceanic NPP variability. Deriving the ocean bio-optical properties places severe demands on instrument performance (especially band to band precision) and atmospheric correction. Improvements in MODIS instrument characterization and calibration over the first 16 mission months have greatly improved the accuracy of the chlorophyll input fields and FLH, and therefore the estimates of NPP and fluorescence efficiency. Annual estimates now show the oceanic NPP accounts for 40-50% of the global total NPP, with significant interannual variations related to large scale ocean processes. Spatial variations in ocean NPP, and exported production, have significant effects on exchange of CO2 between the ocean and atmosphere. Further work is underway to improve both the primary productivity model functions, and to refine our understanding of the relationships between fluorescence efficiency and NPP estimates. We expect that the MODIS instruments will prove extremely useful in assessing the time dependencies of oceanic carbon uptake and effects of iron enrichment, within the global carbon cycle.

Esaias, Wayne E.↗
NASA NTRS2002

Primary Mirror Figure Maintenance of the Hobby-Eberly Telescope using the Segment Alignment Maintenance System

The Segment Alignment Maintenance System (SAMs) was installed on McDonald Observatory's Hobby-Eberly Telescope (HET) in August 2001. The SAMs became fully operational in October 2001. The SAMs uses a system of 480 inductive edge sensors to correct misalignments of the HET's 91 primary mirror segments when the segments are perturbed from their aligned reference positions. A special observer estimated and corrects for the global radius of curvature (GroC) mode, a mode unobservable by the edge sensors. The SAMs edge sensor system and (GroC) estimator are able to maintain HET's primary figure for much longer durations than previously had been observed. Telescope image quality has improved, and the amount of overhead time required from primary mirror alignment has been reduced. This paper gives a functional description of the SAMs control system and presents performance verification data. This paper also describes how the SAMs has improved the operational efficiency of the HET.

Rakoczy, John↗
NASA NTRS2003

Ocean Primary Production Estimates from Terra MODIS and Their Dependency on Satellite Chlorophyll Alpha Algorithms

Simplistic models relating global satellite ocean color, temperature, and light to ocean net primary production (ONPP) are sensitive to the accuracy and limitations of the satellite estimate of chlorophyll and other input fields, as well as the primary productivity model. The standard MODIS ONPP product uses the new semi-analytic chlorophyll algorithm as its input for two ONPP indexes. The three primary MODIS chlorophyll Q estimates from MODIS, as well as the SeaWiFS 4 chlorophyll product, were used to assess global and regional performance in estimating ONPP for the full mission, but concentrating on 2001. The two standard ONPP algorithms were examined with 8-day and 39 kilometer resolution to quantify chlorophyll algorithm dependency of ONPP. Ancillary data (MLD from FNMOC, MODIS SSTD1, and PAR from the GSFC DAO) were identical. The standard MODIS ONPP estimates for annual production in 2001 was 59 and 58 GT C for the two ONPP algorithms. Differences in ONPP using alternate chlorophylls were on the order of 10% for global annual ONPP, but ranged to 100% regionally. On all scales the differences in ONPP were smaller between MODIS and SeaWiFS than between ONPP models, or among chlorophyll algorithms within MODIS. Largest regional ONPP differences were found in the Southern Ocean (SO). In the SO, application of the semi-analytic chlorophyll resulted in not only a magnitude difference in ONPP (2x), but also a temporal shift in the time of maximum production compared to empirical algorithms when summed over standard oceanic areas. The resulting increase in global ONPP (6-7 GT) is supported by better performance of the semi-analytic chlorophyll in the SO and other high chlorophyll regions. The differences are significant in terms of understanding regional differences and dynamics of ocean carbon transformations.

Essias, Wayne E.↗
NASA NTRS1952

Preliminary Air-Flow and Thrust Calibrations of Several Conical Cooling-Air Ejectors with a Primary to Secondary Temperature Ratio of 1.0: Diameter Ratios of 1.06 and 1.40 - 2

An investigation was made of the performance of nine conical cooling-air ejectors at primary jet pressure ratios from 1 to 10, secondary pressure ratios to 4.0, and a temperature ratio of unity. This phase of the investigation was limited to conical ejectors having shroud exit to primary nozzle exit diameter ratios of 1.06 and 1.40, with several spacing ratios for each. The experimental results indicated that the pumping range and amount of cooling-air flow obtained with a 1.06 diameter ratio ejector were relatively small for cooling purposes but that the maximum possible thrust loss, which occurred with no secondary flow, was only 7 percent of convergent nozzle thrust. The 1.40 diameter ratio ejector produced a large cooling air flow and showed a possible thrust loss of 29.5 percent with no cooling air flow. Thrust gains were attained with ejectors of both diameter ratios at secondary pressure ratios greater than 1.0. The limiting primary pressure ratio below which an ejector can operate at a specific secondary pressure ratio (cut-off point) may be estimated for various flight conditions from data contained herein.

Greathouse, W. K.↗
NASA NTRS1989

The post-Paleozoic chronology and mechanism of 13C depletion in primary marine organic matter

Carbon-isotopic compositions of geoporphyrins have been measured from marine sediments of Mesozoic and Cenozoic age in order to elucidate the timing and extent of depletion of 13C in marine primary producers. These results indicate that the difference in isotopic composition of coeval marine carbonates and marine primary photosynthate was approximately 5 to 7 permil greater during the Mesozoic and early Cenozoic than at present. In contrast to the isotopic record of marine primary producers, isotopic compositions of terrestrial organic materials have remained approximately constant for this same interval of time. This difference in the isotopic records of marine and terrestrial organic matter is considered in terms of the mechanisms controlling the isotopic fractionation associated with photosynthetic fixation of carbon. We show that the decreased isotopic fractionation between marine carbonates and organic matter from the Early to mid-Cenozoic may record variations in the abundance of atmospheric CO2.

Non-NASA Center↗
NASA NTRS1985

A morphometric analysis of cellular differentiation in caps of primary and lateral roots of Helianthus annuus

In order to determine if patterns of cell differentiation are similar in primary and lateral roots, I performed a morphometric analysis of the ultrastructure of calyptrogen, columella, and peripheral cells in primary and lateral roots of Helianthus annuus. Each cell type is characterized by a unique ultrastructure, and the ultrastructural changes characteristic of cellular differentiation in root caps are organelle specific. No major structural differences exist in the structures of the composite cell types, or in patterns of cell differentiation in caps of primary vs. lateral roots.

Non-NASA Center↗
NASA NTRS1994

Comparative assessment of the polypeptide profiles from lateral and primary roots of Phaseolus vulgaris L

In Phaseolus vulgaris, primary roots show gravitational sensitivity soon after emerging from the seed. In contrast, lateral roots are agravitropic during early development, and become gravitropic after several cm growth. Primary and lateral root tissues were examined by polyacrylamide gel electrophoresis, coupled with western blotting techniques, to compare proteins which may contribute to the acquisition of gravitational sensitivity. Root tips and zones of cell elongation were compared for each root type, using immunological probes for calmodulin, alpha-actin, alpha-tubulin, and proteins of the plastid envelope. Lateral roots contained qualitatively less calmodulin, and showed a slightly different pattern of actin-related epitope proteins, than did primary root tissues, suggesting that polypeptide differences may contribute to the gravitational sensitivity which these root types express.

Non-NASA Center↗
NASA NTRS1985

Growth and graviresponsiveness of primary roots of Zea mays seedlings deficient in abscisic acid and gibberellic acid

The objective of this research was to determine if gibberellic acid (GA) and/or abscisic acid (ABA) are necessary for graviresponsiveness by primary roots of Zea mays. To accomplish this objective we measured the growth and graviresponsiveness of primary roots of seedlings in which the synthesis of ABA and GA was inhibited collectively and individually by genetic and chemical means. Roots of seedlings treated with Fluridone (an inhibitor of ABA biosynthesis) and Ancymidol (an inhibitor of GA biosynthesis) were characterized by slower growth rates but not significantly different gravicultures as compared to untreated controls. Gravicurvatures of primary roots of d-5 mutants (having undetectable levels of GA) and vp-9 mutants (having undectable levels of ABA) were not significantly different from those of wild-type seedlings. Roots of seedlings in which the biosynthesis of ABA and GA was collectively inhibited were characterized by gravicurvatures not significantly different for those of controls. These results (1) indicate that drastic reductions in the amount of ABA and GA in Z. mays seedlings do not significantly alter root graviresponsiveness, (2) suggest that neither ABA nor GA is necessary for root gravicurvature, and (3) indicate that root gravicurvature is not necessarily proportional to root elongation.

Zea mays/drug effects/growth & development/metabol↗
NASA NTRS2005

Spherical Primary Optical Telescope (SPOT): An Architecture Demonstration for Cost-effective Large Space Telescopes

This paper summarizes efforts underway at the Goddard Space Flight Center to demonstrate a new type of space telescope architecture that builds on the rigid, segmented telescope heritage of the James Webb Space Telescope but that solves several key challenges for future space telescopes. The architecture is based on a cost-effective segmented spherical primary mirror combined with a unique wavefront sensing and control system that allows for continuous phasing of the primary mirror. The segmented spherical primary allows for cost-effective 3-meter class (eg, Midex and Discovery) missions as well as enables 30-meter telescope solutions that can be manufactured in a reasonable amount of time and for a reasonable amount of money. The continuous wavefront sensing and control architecture enables missions in low-earth-orbit and missions that do not require expensive stable structures and thermal control systems. For the 30-meter class applications, the paper discusses considerations for assembling and testing the telescopes in space. The paper also summarizes the scientific and technological roadmap for the architecture and also gives an overview of technology development, design studies, and testbed activities underway to demonstrate it s feasibility.

Feinberg, Lee↗