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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Plant Growth in Controlled Environments in Response to Characteristics of Nutrient Solutions

Emphasis was given to environmental factors that alter the flux of carbohydrate from the shoot to the root system to support the absorption of nitrogen and the subsequent interaction between nitrogen uptake and whole plant growth. Only the nitrate form of nitrogen was utilized in order to establish base line responses for evaluation of future studies utilizing both ammonium and nitrate.

Raper, C. D., Jr.↗
NASA NTRS1974

Engineering parameter determination from the radio astronomy explorer /RAE I/ satellite attitude data

An RAE-I satellite description is given, taking into account a dynamics experiment and the attitude sensing system. A computer program for analyzing flexible spacecraft attitude motions is considered, giving attention to the geometry of rod deformation. The characteristics of observed attitude data are discussed along with an analysis of the main boom root angle, the bending rigidity, and the damper plane angle.

Lawlor, E. A.↗
NASA NTRS1990

Performance of an optimized rotor blade at off-design flight conditions

An investigation is made of the dynamic and aerodynamic performance of a helicopter rotor previously optimized for minimum 4/rev vertical shear and blade weight subject to certain dynamic and structural constraints. The program CAMRAD which was used in designing the optimized blade is used for both dynamic and aerodynamic analaysis. The behavior of the optimized rotor is analyzed over a wide range of operating conditions and for a larger number of rotor characteristics than those considered in designing the blade. To assess the dynamic behavior, the blade root vibratory shears and moments that are transmitted to the rotor hub are calculated. The aerodynamic performance assessments are made based on the power required by the rotor for a given rotor task, the rotor lifting efficiencies, maximum rotor thrust envelopes and the control margins. Results are presented for the optimized blade and the control margins. Results are presented for the optimized blade and the reference blade, which was used as the baseline for the optimized blade, for two rotor tasks.

Chattopadhyay, Aditi↗
NASA NTRS1990

Performance of an optimized rotor blade at off-design flight conditions

An investigation is made of the dynamic and aerodynamic performance of a helicopter rotor previously optimized for minimum 4/rev vertical shear and blade weight subject to certain dynamic and structural constraints. The program CAMRAD which was used in designing the optimized blade is used for both dynamic and aerodynamic analysis. The behavior of the optimized rotor is analyzed over a wide range of operating conditions and for a larger number rotor characteristics than those considered in designing the blade. To assess the dynamic behavior, the blade root vibratory shears and moments that are transmitted to the rotor hub are calculated. The aerodynamic performance assessments are made based on the power required by the rotor for a given rotor task, the rotor lifting efficiencies, maximum rotor thrust envelopes and the control margins. Results are presented for the optimized blade and the reference blade which was used as the baseline for the optimized blade, for two rotor tasks.

Chattopadhyay, Aditi↗
NASA NTRS1985

Perturbation-iteration theory for analyzing microwave striplines

A perturbation-iteration technique is presented for determining the propagation constant and characteristic impedance of an unshielded microstrip transmission line. The method converges to the correct solution with a few iterations at each frequency and is equivalent to a full wave analysis. The perturbation-iteration method gives a direct solution for the propagation constant without having to find the roots of a transcendental dispersion equation. The theory is presented in detail along with numerical results for the effective dielectric constant and characteristic impedance for a wide range of substrate dielectric constants, stripline dimensions, and frequencies.

Kretch, B. E.↗
NASA NTRS1996

Calcium-Dependent Protein Kinase Genes in Corn Roots

Two cDNAs encoding Ca-2(+) - Dependent Protein Kinases (CDPKs), Corn Root Protein Kinase 1 and 2 (CRPK 1, CRPK 2) were isolated from the root tip library of corn (Zea mays L., cv. Merit) and their nucleotide sequences were determined. Deduced amino acid sequences of both the clones have features characteristic of plant CDPKS, including all 11 conserved serine/threonine kinase subdomains, a junction domain and a calmodulin-like domain with four Ca-2(+), -binding sites. Northern analysis revealed that CRPKI mRNA is preferentially expressed in roots, especially in the root tip; whereas, the expression of CRPK2 mRNA was very low in all the tissues tested. In situ hybridization experiments revealed that CRPKI mRNA is highly expressed in the root apex, as compared to other parts of the root. Partially purified CDPK from the root tip phosphorylates syntide-2, a common peptide substrate for plant CDPKs, and the phosphorylation was stimulated 7-fold by the addition of Ca-2(+). Our results show that two CDPK isoforms are expressed in corn roots and they may be involved in the Ca-2(+)-dependent signal transduction process.

Takezawa, D.↗
NASA NTRS1996

Monitoring the Photosynthetic Apparatus During Space Flight: Interspecific Variation in Chlorophyll Fluorescence Signatures Induced by Different Root Zone Stresses

Chlorophyll fluorescence has been used extensively as a tool to indicate stress to the photosynthetic apparatus in green plants. A rise in fluorescence has been attributed to the blockage of photosystem II photochemistry, and patterns of fluorescence decay (quenching) from dark adapted leaves can be related to specific photochemical and non-photochemical deexcitation pathways of light trapped by the photosynthetic apparatus and thus result in characteristically different fluorescence signatures. Four distantly related plant species, Hypocharis radicata (Asteraceae), Brassica rapa (Brassicaceae), Spinacea oleracea (Chenopodiaceae) and Triticum aestivum (Poaceae), were grown hydroponically for three weeks before the initiation of three different root zone stresses (10 mM Cu, 100 mM NaCl and nitrogen deficient nutrition). After 10 days, characteristic fluorescence signatures for each stress could be noted although the degree varied between species. Fast kinetics analysis showed a reduction in plastoquinone pool size for copper and nitrogen stress for all species but a more species specific result with NaCl stress. Photochemical quenching kinetics varied between species and stress treatments from no quenching in S. oleracea in copper treatments to increased photochemical quenching in NaCl treatments. Non-photochemical quenching kinetics demonstrated a distinct pattern between stresses for all species. Copper treatments characteristically exhibited a shallow, flat non-photochemical quenching profile suggesting a general blockage of electron transport whereas NaCl treatments exhibited a slow rising profile that suggested damage to thylakoid acidification kinetics and nitrogen deficiency exhibited a fast rising and declining profile that suggested an altered state 1-state 2 transition regulated by the phosphorylation of LHCII. These results demonstrate characteristic fluorescence signatures for specific plant stresses that may be applied to different, unrelated plant species. In addition, the potential use of chlorophyll fluorescence for both basic research and diagnostic physiology in space biology is presented.

Bubenheim, David L.↗
NASA NTRS1983

Effects of twin-vertical-tail parameters on twin-engine afterbody/nozzle aerodynamic characteristics

The Langley 16-foot transonic tunnel was used to determine the effects of several empennage and afterbody parameters on twin-engine aft-end aerodynamic characteristics. Model variables included twin-vertical-tail cant angle, toe angle, airfoil camber, and root-chord length and afterbody/engine interfairing shape. Tests were conducted over a Mach number range from 0.6 to 1.2 and over an angle-of-attack range from 2 deg to 10 deg. Nozzle pressure ratio was varied from 1.0 (jet off) to approximately 10.0.

Leavitt, L. D.↗
NASA NTRS1993

The formation and evolution of Alpha and Tellus tesserae on Venus

Although tesserae comprise at approximately 10 percent of the surface of Venus, the nature of their formation and evolution is not well understood. One important clue to elucidate this problem is tessera boundaries which are of two types: type 1 are generally embayed by plains; type 2 boundaries are characterized by being linear at the hundred kilometer scale and often associated with steep scarps or tectonic features. Previous study of a distinctive type 2 boundary at Alpha Regio was pursued in order to characterize and assess the implications for this style in general. A model of gravitational relaxation of the tessera block was presented to explain the specific style of type 2 feature seen at western Alpha; however, this model cannot account for the full range of interior structures of Alpha, namely widespread compressional features overprinted by extensional features and volcanism. In order to explain the features of Alpha, we have considered a three-stage model involving (1) mantle downwelling and compression of the lithosphere, (2) delamination of the thickened tessera root, and (3) gravitational relaxation and extension of the tessera plateau. We compare this to the characteristics of Tellus Regio in order to test its broader application.

Gilmore, M. S.↗
NASA NTRS1983

An experimental study of changes in the structure of a turbulent boundary layer due to surface geometry changes

This investigation attempts to observe changes in the flow structure of a nominally zero pressure gradient turbulent boundary layer by altering the surface of a smooth plate with small triangular riblets oriented in the direction of flow and protruding just above the viscous sublayer. Hot-wire measurements show a reduction in the local skin friction over the riblet valleys by about 40% compared to the smooth surface near the end of the plate. Local skin friction increases by about 10% over the riblet peaks. Results showing the effects of the riblets on the mean, root-mean-square and skewness factor distributions of the streamwise velocity are presented. The mean profile displays characteristics similar to those of drag reducing additives; the streamwise turbulence intensity is reduced by approximately 10-15% near the surface by the riblets; the skewness factor distribution is virtually unchanged. A comparison of results from an application of the VITA 'burst' detection technique to smooth and riblet surface data is also presented although the results are rather inconclusive. Flow visualization of 'bursting' over both surfaces, while dramatically revealing the structure, reveals little difference resulting from the presence of the riblet.

Source record↗
NASA NTRS1980

Results of design studies and wind tunnel tests of high-aspect-ratio supercritical wings for an energy efficient transport

These basic characteristics of critical wings included wing area, aspect ratio, average thickness, and sweep as well as practical constraints on the planform and thickness near the wing root to allow for the landing gear. Within these constraints, a large matrix of wing designs was studied with spanwise variations in the types of airfoils and distribution of lift as well as some small planform changes. The criteria by which the five candidate wings were chosen for testing were the cruise and buffet characteristics in the transonic regime and the compatibility of the design with low speed (high-lift) requirements. Five wing-wide-body configurations were tested in the NASA Ames 11-foot transonic wind tunnel. Nacelles and pylons, flap support fairings, tail surfaces, and an outboard aileron were also tested on selected configurations.

Steckel, D. K.↗
NASA NTRS1994

Associations of Methanotrophs With the Roots and Rhizomes of Aquatic Vegetation

Results of an in vitro assay revealed that root-associated methane consumption was a common attribute or diverse emergent wetland macrophytes from a variety of habitats. Maximum potential uptake rates (V(sub maxp)) varied between about 1 and 10 micro mol g/ (dry weight) h, with no obvious correlation between rate and gross morphological characteristics of the plants. The V(sub maxp) corresponded to about 2 x 10(exp 18) to 2 x 10(exp 9) methanotrophs g/ (dry weight), assuming that root-associated methanotrophs have cell-specific activities comparable to those of known isolates. V(sub maxp) varied seasonally for an aquatic grass, Calamogrostis canadensis, and for the cattail, Typha latifolia, with highest rates in late summer. V(sub maxp) was well correlated with ambient temperature for C. canadensis but weakly correlated for T. Wifolia. The seasonal changes in V(sub maxp), as well as inferences from apparent half-saturation constants for methane uptake (K(sub app); generally 3 to 6 micro M), indicated that oxygen availability might be more important than methane as a rate determinant. In addition, roots incubated under anoxic conditions showed little or no postanoxia aerobic methane consumption, indicating that root-associated metbanotrophic populations might not tolerate variable oxygen availability. Hybridization of oligodeoxynucleotide probes specific for group 1 or group 2 methylotrophs also varied seasonally. The group 2-specific probe consistently hybridized to a greater extent than the group 1 probe, and the relative amount of group 2 probe hybridization to C. canadensis root extracts was positively correlated with V(sub maxp).

King, Gary M.↗
NASA NTRS1974

Effects of turbulence in the atmosphere of Venus on Pioneer Venus radio, phase 2

Two problems related to the effects of turbulence in the atmosphere of Venus on the Pioneer entry probe radio link were studied. In the first problem, the cross correlation between the log amplitude and phase fluctuations of the Pioneer Venus communications link is examined. Data show that for fluctuation frequencies above approximately 1 Hz there is little or no correlation. For frequencies below this region the correlation is weak and the square root of the coherence has a peak value close to 0.65. The second problem consists of interferring turbulence characteristics of the Venus atmosphere from the Mariner 5 phase fluctuations. Data show that with the data processing techniques developed and currently available, the phase error due to oscillator drift, assumed trajectory delay, and spline curve fit exceed the turbulence induced fluctuations. Results show that it is not possible to interfere with the turbulence characteristics from Mariner 5 phase fluctuations.

Woo, R. T.↗
NASA NTRS1976

Surface photometry of Virgo cluster galaxies - Barred galaxies

Photographic surface photometry in B and V is presented for three barred galaxies in the Virgo cluster: N4548, N4596, and N4608. Intercomparisons of luminosity and color profiles and standard photometric parameters indicate that for these galaxies: (1) the nuclear component follows the fourth-root-of-radius luminosity law for both B and V, (2) the luminosity profiles along the bar show a characteristic shoulder with a slight fall in B-V color profile at the brightest point in the bar, the strength of the effect declining from N4548 to N4608, (3) the integrated bar component is slightly bluer than the nucleus, and (4) as the disk, arm, and ring components contribute less to the total luminosity of the system, the contribution of the bar increases as does the equivalent gradient.

Benedict, G. F.↗
NASA NTRS1984

Issues in Developing a Normative Descriptive Model for Dyadic Decision Making

Most research in modelling human information processing and decision making has been devoted to the case of the single human operator. In the present effort, concepts from the fields of organizational behavior, engineering psychology, team theory and mathematical modelling are merged in an attempt to consider first the case of two cooperating decisionmakers (the Dyad) in a multi-task environment. Rooted in the well-known Dynamic Decision Model (DDM), the normative descriptive approach brings basic cognitive and psychophysical characteristics inherent to human behavior into a team theoretic analytic framework. An experimental paradigm, involving teams in dynamic decision making tasks, is designed to produce the data with which to build the theoretical model.

Serfaty, D.↗
NASA NTRS1959

A Buffet Investigation at High Subsonic Speeds of Wing-Fuselage-Tail Combinations having Sweptback Wings with NACA Four-Digit Thickness Distributions, Fences, and Body Contouring

An investigation has been made to determine the effect of wing fences, fuselage contouring, varying wing sweepback angle from 40 deg. to 45 deg., mounting the horizontal tail on an outboard boom) and wing thickness distribution upon the buffeting response of typical airplane configurations employing sweptback wings of high aspect ratio. The tests were conducted through an angle-of-attack range at Mach numbers varying from 0.60 to 0.92 at a Reynolds number of 2 million. For the combinations with 40 deg. of sweepback, the addition of multiple wing fences usually decreased the buffeting at moderate and high lift coefficients and reduced the erratic variation of buffet intensities with increasing lift coefficient and Mach number. Fuselage contouring also reduced buffeting but was not as effective as the wing fences. At most Mach numbers, buffeting occurred at higher lift coefficients for the combination with the NACA 64A thickness distributions than for the combination with the NACA four-digit thickness distributions. At high subsonic speeds, heavy buffeting was usually indicated at lift coefficients which were lower than the lift coefficients for static-longitudinal instability. The addition of wing fences improved the pitching-moment characteristics but had little effect on the onset of buffeting. For most test conditions and model configurations, the root-mean- square and the maximum values measured for relative buffeting indicated similar effects and trends; however, the maximum buffeting loads were usually two to three times the root-mean-square intensities.

Sutton, Fred B.↗
NASA NTRS2003

Transonic Unsteady Aerodynamics of the F/A-18E at Conditions Promoting Abrupt Wing Stall

A transonic wind tunnel test of an 8% F/A-18E model was conducted in the NASA Langley Research Center (LaRC) 16-Foot Transonic Tunnel (16-Ft TT) to investigate the Abrupt Wing Stall (AWS) characteristics of this aircraft. During this test, both steady and unsteady measurements of balance loads, wing surface pressures, wing root bending moments, and outer wing accelerations were performed. The test was conducted with a wide range of model configurations and test conditions in an attempt to reproduce behavior indicative of the AWS phenomenon experienced on full-scale aircraft during flight tests. This paper focuses on the analysis of the unsteady data acquired during this test. Though the test apparatus was designed to be effectively rigid. model motions due to sting and balance flexibility were observed during the testing, particularly when the model was operating in the AWS flight regime. Correlation between observed aerodynamic frequencies and model structural frequencies are analyzed and presented. Significant shock motion and separated flow is observed as the aircraft pitches through the AWS region. A shock tracking strategy has been formulated to observe this phenomenon. Using this technique, the range of shock motion is readily determined as the aircraft encounters AWS conditions. Spectral analysis of the shock motion shows the frequencies at which the shock oscillates in the AWS region, and probability density function analysis of the shock location shows the propensity of the shock to take on a bi-stable and even tri-stable character in the AWS flight regime.

Schuster, David M.↗