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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Apparatus Measures Thicknesses Of Ice On Bars

Semiautomated apparatus measures diameters, at selected lengthwise positions, of nine vertical ice-coated bars in icing-research wind tunnel. Includes measuring head that travels on rails parallel to bar, driven by ball screw actuated by stepping motor. Position of measuring head along bar measured by string potentiometer, providing position feedback for closed-loop control circuit. Circuit provides for smooth motion of measuring head, and used to select various programmed sequences of motions and measurements. Measurements needed to determine degree of uniformity of icing conditions for experiments on aircraft models.

Gibson, Theresa L.↗
NASA NTRS2003

Life Cycle Testing of Viscoelastic Material for Hubble Space Telescope Solar Array 3 Damper

During the March 2002 Servicing Mission by Space Shuttle (STS 109), the Hubble Space Telescope (HST) was refurbished with two new solar arrays that now provide all of its power. These arrays were built with viscoelastic/titanium dampers, integral to the supporting masts, which reduce the interaction of the wing bending modes with the Telescope. Damping of over 3% of critical was achieved. To assess the damper s ability to maintain nominal performance over the 10-year on-orbit design goal, material specimens were subjected to an accelerated life test. The test matrix consisted of scheduled events to expose the specimens to pre-determined combinations of temperatures, frequencies, displacement levels, and numbers of cycles. These exposure events were designed to replicate the life environment of the damper from fabrication through testing to launch and life on-orbit. To determine whether material degradation occurred during the exposure sequence, material performance was evaluated before and after the accelerated aging with complex stiffness measurements. Based on comparison of pre- and post-life-cycle measurements, the material is expected to maintain nominal performance through end of life on-orbit. Recent telemetry from the Telescope indicates that the dampers are performing nominally.

Maly, Joseph R.↗
NASA NTRS1997

Finding Fault with Faults: A Case Study

We describe our effort in extending this work beyond the initial software contruction. Our area of focus is determining the rate of fault injection over a sequence of successive builds, first observing that software faults may be seen to fall into two distinct classes some faults are incorporated during the initial coding effort, while others are added in successive software builds.

Software Systems Software faults↗
NASA NTRS1981

Applications of digital image acquisition in anthropometry

A description is given of a video kinesimeter, a device for the automatic real-time collection of kinematic and dynamic data. Based on the detection of a single bright spot by three TV cameras, the system provides automatic real-time recording of three-dimensional position and force data. It comprises three cameras, two incandescent lights, a voltage comparator circuit, a central control unit, and a mass storage device. The control unit determines the signal threshold for each camera before testing, sequences the lights, synchronizes and analyzes the scan voltages from the three cameras, digitizes force from a dynamometer, and codes the data for transmission to a floppy disk for recording. Two of the three cameras face each other along the 'X' axis; the third camera, which faces the center of the line between the first two, defines the 'Y' axis. An image from the 'Y' camera and either 'X' camera is necessary for determining the three-dimensional coordinates of the point.

Woolford, B.↗
NASA NTRS1977

The petrology of the Apollo 12 ilmenite basalt suite

Mineral chemistry data and petrographic interpretations as well as fractionation modeling determined independently indicate that the bulk chemical variations in the ilmenite suite can be reconciled with differentiation within a single cooling unit. Olivine porphyritic basalts, medium-grained basalts with evolved compositions, and coarse-grained olivine cumulates are found in the suite. It is suggested that most of the chemical variation within the suite could result from fractionation of olivine equivalent to the composition of phenocrysts in vitrophyre 12008 which serves well as a parental magma for the other textural-chemical variants. The relative cooling rate sequence within all three textural-chemical subgroups was determined, and systematic correlations between the degree of olivine addition or subtraction and the relative cooling rate is indicated.

Dungan, M. A.↗
NASA NTRS1979

Loran-C flight data base

Loran-C time-difference data were collected on January 9, 1979 during a flight from Athens, Ohio to Madison VOR in Connecticut, thence to Millville VOR in New Jersey, and a landing at Atlantic City NAFEC. Portions of the return trip to Athens, Ohio were also recorded. Loran-C GRI data frames were recorded using the 99600 U. S. Northeast Loran chain stations Seneca/Nantucket (TDA) and Seneca/Carolina Beach (TDB). The GRI sequence number TDA and TDB were recorded as integer numbers, with the TD's in integer microseconds. Actual time-of-day can be determined from the data start time, plus the time per GRI and the sequence number. The low cost Loran-C receiver was used to obtain the time-difference data for each GRI. Data was recorded on digital magnetic tape and post-processed into latitude and longitude using an IBM system/370 computer.

Lilley, R. W.↗
NASA NTRS1993

Finite-size effects on long-range correlations: implications for analyzing DNA sequences

We analyze the fluctuations in the correlation exponents obtained for noncoding DNA sequences. We find prominent sample-to-sample variations as well as variations within a single sample in the scaling exponent. To determine if these fluctuations may result from finite system size, we generate correlated random sequences of comparable length and study the fluctuations in this control system. We find that the DNA exponent fluctuations are consistent with those obtained from the control sequences having long-range power-law correlations. Finally, we compare our exponents for the DNA sequences with the exponents obtained from power-spectrum analysis and correlation-function techniques, and demonstrate that the original "DNA-walk" method is intrinsically more accurate due to reduced noise.

NASA Discipline Cardiopulmonary↗
NASA NTRS1993

Preliminary Stratigraphic Basis for Geologic Mapping of Venus

The age relations between geologic formations have been studied at 36 1000x1000 km areas centered at the dark paraboloid craters. The geologic setting in all these sites could be characterized using only 16 types of features and terrains (units). These units form a basic stratigraphic sequence (from older to younger: (1) Tessera (Tt); (2-3) Densely fractured terrains associated with coronae (COdf) and in the form of remnants among plains (Pdf); (4) Fractured and ridged plains (Pfr); (5) Plains with wrinkle ridges (Pwr); (6-7) Smooth and lobate plains (Ps/Pl); and (8) Rift-associated fractures (Fra). The stratigraphic position of the other units is determined by their relation with the units of the basic sequence: (9) Ridge bells (RB), contemporary with Pfr; (10-11) Ridges of coronae and arachnoids annuli (COar/Aar), contemporary with wrinkle ridges of Pwr; (12) Fractures of coronae annuli (COaf) disrupt Pwr and Ps/Pl; (13) Fractures (F) disrupt Pwr or younger units; (14) Craters with associated dark paraboloids (Cdp), which are on top of all volcanic and tectonic units except the youngest episodes of rift-associated fracturing and volcanism; (15-16) Surficial streaks (Ss) and surficial patches (Sp) are approximately contemporary with Cdp. These units may be used as a tentative basis for the geologic mapping of Venus including VMAP. This mapping should test the stratigraphy and answer the question of whether this stratigraphic sequence corresponds to geologic events which were generally synchronous all around the planet or whether the sequence is simply a typical sequence of events which occurred in different places at diffferent times.

Basilevsky, A. T.↗
NASA NTRS2019

Methylation Pattern Detection in the Genome of Bacillus Pumilus Strain SAFR-032

Bacillus pumilus SAFR-032, an endospore-forming bacterial strain that was isolated from a spacecraft assembly facility (SAFR), was investigated to determine its methylation pattern (methylome) across the genome in comparison to the previously sequenced reference genome. In addition, a version of SAFR-032 that was flown as spores for 18 months on the International Space Station (ISS) was also investigated for possible genomic changes due to long-duration ISS-flight and to determine if methylation patterns may have changed. Both the genomics and methylomics were conducted using a Nanopore MinION sequencing device. In addition to the omics investigation, the two SAFR-032 strains, ISS flown and non-ISS flown, were compared phenotypically in chamber experiments testing individual environmental insults: ionizing radiation, UV exposure, and cold desiccation (i.e. freeze drying). Results from this study inform on Planetary Protection concerns and will reveal potential DNA damage associated with long-term spaceflight and how such damage may influence survivors after being transported to an extraterrestrial environment, such as Mars.

Serda, Bianca M.↗
NASA NTRS1997

Improvements in Block-Krylov Ritz Vectors and the Boundary Flexibility Method of Component Synthesis

A method of dynamic substructuring is presented which utilizes a set of static Ritz vectors as a replacement for normal eigenvectors in component mode synthesis. This set of Ritz vectors is generated in a recurrence relationship, proposed by Wilson, which has the form of a block-Krylov subspace. The initial seed to the recurrence algorithm is based upon the boundary flexibility vectors of the component. Improvements have been made in the formulation of the initial seed to the Krylov sequence, through the use of block-filtering. A method to shift the Krylov sequence to create Ritz vectors that will represent the dynamic behavior of the component at target frequencies, the target frequency being determined by the applied forcing functions, has been developed. A method to terminate the Krylov sequence has also been developed. Various orthonormalization schemes have been developed and evaluated, including the Cholesky/QR method. Several auxiliary theorems and proofs which illustrate issues in component mode synthesis and loss of orthogonality in the Krylov sequence have also been presented. The resulting methodology is applicable to both fixed and free- interface boundary components, and results in a general component model appropriate for any type of dynamic analysis. The accuracy is found to be comparable to that of component synthesis based upon normal modes, using fewer generalized coordinates. In addition, the block-Krylov recurrence algorithm is a series of static solutions and so requires significantly less computation than solving the normal eigenspace problem. The requirement for less vectors to form the component, coupled with the lower computational expense of calculating these Ritz vectors, combine to create a method more efficient than traditional component mode synthesis.

Carney, Kelly Scott↗
NASA NTRS2001

Axial and Torsional Load-Type Sequencing in Cumulative Fatigue: Low Amplitude Followed by High Amplitude Loading

The experiments described herein were performed to determine whether damage imposed by axial loading interacts with damage imposed by torsional loading. This paper is a follow on to a study that investigated effects of load-type sequencing on the cumulative fatigue behavior of a cobalt base superalloy, Haynes 188 at 538 C Both the current and the previous study were used to test the applicability of cumulative fatigue damage models to conditions where damage is imposed by different loading modes. In the previous study, axial and torsional two load level cumulative fatigue experiments were conducted, in varied combinations, with the low-cycle fatigue (high amplitude loading) applied first. In present study, the high-cycle fatigue (low amplitude loading) is applied initially. As in the previous study, four sequences (axial/axial, torsion/torsion, axial/torsion, and torsion/axial) of two load level cumulative fatigue experiments were performed. The amount of fatigue damage contributed by each of the imposed loads was estimated by both the Palmgren-Miner linear damage rule (LDR) and the non-linear damage curve approach (DCA). Life predictions for the various cumulative loading combinations are compared with experimental results.

Bonacuse, Peter J.↗
NASA NTRS1982

Serial data correlator/code translator

A system for analyzing asynchronous signals containing bits of information for ensuring the validity of said signals, by sampling each bit of information a plurality of times, and feeding the sampled pieces of bits of information into a sequence controlled is described. The sequence controller has a plurality of maps or programs through which the sampled pieces of bits are stepped so as to identify the particular bit of information and determine the validity and phase of the bit. The step in which the sequence controller is clocked is controlled by a storage register. A data decoder decodes the information fed out of the storage register and feeds such information to shift registers for storage.

Morgan, L. E.↗
NASA NTRS2019

Does Seed Sanitization Affect the Plant Rhizosphere Microbiome and Its Ability to Compete with the Human Associated Pathogen, E. coli on Salad Crops?

Cultivation of crops in controlled environmental agricultural systems may limit microbial colonization and reduce diversity of the microbial communities. Practices like seed and growth medium sanitization may further impact microbial communities in the mature plant and the plant’s capacity to limit the growth of pathogens through competition. As humans expand their travels to space, understanding plant growth, health, and development in closed environments will be critical to the success of producing a safe, supplemental food source for astronauts. To determine the persistence of a potential human pathogen in plant growth and development, sanitized and unsanitized seeds from, mizuna (Brassica rapa var japonica) and red romaine lettuce (Lactuca sativa cultivar ‘Outredgeous’), were inoculated with Escherichia coli, ATCC 21445, germinated under simulated International Space Station (ISS) environmental conditions and harvested every 7 days until maturity. The persistence of E. coli in the rhizosphere was determined by plating on selective media, real time PCR (Polymerase Chain Reaction) and community sequencing of the rhizosphere communities. E. coli was detected in the crops’ roots and leaves for several weeks post germination. At day 28, plants from sanitized seeds had significantly higher counts of E. coli on the roots than those from unsanitized seeds. E. coli was also detected on a few uninoculated plants indicating airborne cross contamination among plants in the same growth chamber and suggesting an influence of the natural microbiome on human pathogen survival and persistence in leafy greens. Sequencing analysis revealed variations in composition and diversity between the communities. Understanding the microbial community of the rhizospheric microbiome is only the first step in determining the relationships between plants. Additional studies to include genotypic and phenotypic variations in the plants should be considered to determine if the natural microbes in the rhizosphere may contribute to the health and therefore, safety of the edible plants.

Khodadad, Christina L. M.↗
NASA NTRS1974

A fast-initializing digital equalizer with on-line tracking for data communications

A theory is developed for a digital equalizer for use in reducing intersymbol interference (ISI) on high speed data communications channels. The equalizer is initialized with a single isolated transmitter pulse, provided the signal-to-noise ratio (SNR) is not unusually low, then switches to a decision directed, on-line mode of operation that allows tracking of channel variations. Conditions for optimal tap-gain settings are obtained first for a transversal equalizer structure by using a mean squared error (MSE) criterion, a first order gradient algorithm to determine the adjustable equalizer tap-gains, and a sequence of isolated initializing pulses. Since the rate of tap-gain convergence depends on the eigenvalues of a channel output correlation matrix, convergence can be improved by making a linear transformation on to obtain a new correlation matrix.

Houts, R. C.↗
NASA NTRS1975

Numerical solution of quadratic matrix equations for free vibration analysis of structures

This paper is concerned with the efficient and accurate solution of the eigenvalue problem represented by quadratic matrix equations. Such matrix forms are obtained in connection with the free vibration analysis of structures, discretized by finite 'dynamic' elements, resulting in frequency-dependent stiffness and inertia matrices. The paper presents a new numerical solution procedure of the quadratic matrix equations, based on a combined Sturm sequence and inverse iteration technique enabling economical and accurate determination of a few required eigenvalues and associated vectors. An alternative procedure based on a simultaneous iteration procedure is also described when only the first few modes are the usual requirement. The employment of finite dynamic elements in conjunction with the presently developed eigenvalue routines results in a most significant economy in the dynamic analysis of structures.

Gupta, K. K.↗
NASA NTRS1977

Exploratory investigation of the incipient spinning characteristics of a typical light general aviation airplane

The incipient spinning characteristics of general aviation airplanes were studied. Angular rates in pitch, yaw, and roll were measured through the stall during the incipient spin and throughout the recovery along with control positions, angle of attack, and angle of sideslip. The characteristic incipient spinning motion was determined from a given set of entry conditions. The sequence of recovery controls were varied at two distinct points during the incipient spin, and the effect on recovery characteristics was examined. Aerodynamic phenomena associated with flow over the aft portion of the fuselage, vertical stabilizer, and rubber are described.

Ranaudo, R. J.↗
NASA NTRS1979

One atmosphere melting experiments on ilmenite basalt 12008

An evaluation of a crystal-fractionation model for Apollo 12 ilmenite basalts with melting experiments under controlled oxygen fugacities is reported. The crystallization sequence including olivine, chromium spinel, and pigeonite phases was determined, showing that the changes in melt composition are dominated by olivine crystallization and the decrease in MgO with a corresponding increase in CaO, Al2O3, and TiO2. It is concluded that the bulk composition of the ilmenite basalts was established by crystallization of olivine and minor spinel prior to the onset of pyroxene and plagioclase.

Rhodes, J. M.↗
NASA NTRS1980

Graphical measurement of Saturn's oblateness and the radius of the Encke gap

The geometric distortions attendant to spin-scan imaging were extraordinarily manifest in the Pioneer encounter with Saturn. By overlapping graphical predictions of these distortions with raster scans of the raw intensity data, both displayed to the same scale on a Versatec printer-plotter, it is possible to determine the precise geometry of a data-taking sequence. The predictions are quite sensitive to the assumed dimensions of Saturn and its rings. It is accordingly concluded that the ratio of polar to equatorial radius is 0.91 and that the Encke gap is 133,500 km from Saturn's center.

Burke, J. J.↗