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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Continuous Tuning and Calibration of Vibratory Gyroscopes

A method of control and operation of an inertial reference unit (IRU) based on vibratory gyroscopes provides for continuously repeated cycles of tuning and calibration. The method is intended especially for application to an IRU containing vibratory gyroscopes that are integral parts of microelectromechanical systems (MEMS) and that have cloverleaf designs, as described in several previous NASA Tech Briefs articles. The method provides for minimization of several measures of spurious gyroscope output, including zero-rate offset (ZRO), angle random walk (ARW), and rate drift. These benefits are afforded both at startup and thereafter during continuing operation, in the presence of unknown rotation rates and changes in temperature. A vibratory gyroscope contains a precision mechanically resonant structure containing two normal modes of vibration nominally degenerate in frequency and strongly coupled via a Coriolis term. In the case of the cloverleaf design MEMS gyro, these normal modes of vibration are plate rocking modes. The rocking motion of the plate is described by giving two angles, theta(sub 1) and theta(sub 2). A proof mass consisting of a post orthogonal to the plate ensures a high degree of Coriolis coupling of vibratory energy from one mode into the other under inertial rotation. The plate is driven and sensed capacitively across a few-microns-wide gap, and the normal mode frequencies can be tuned electrostatically by DC voltages applied across this gap. In order to sense rotation, the resonator plate is caused to rock in the theta(sub 1) direction, then any small motions in the theta(sub 2) direction are sensed, rebalanced, and interpreted as inertial rotation. In this scenario, the "drive" has been assigned to the theta(sub 1) direction, and the "sense" has been assigned to the theta(sub 2) direction.

Hayworth, Ken↗
NASA NTRS1988

Effect of large amplitude pitching motions on the unsteady aerodynamic characteristics of flat-plate wings

Large-amplitude unsteady motion effects on the aerodynamic force and stability characteristics of flat-plate wings were investigated in a wind tunnel for the cases of two delta wings with respective leading edge sweeps of 70 and 45 deg, and a rectangular wing whose aspect ratio was equal to that of the 70-deg delta wing. Attention was given to the effects of reduced frequency and mean angle of attack. It is found that lags in vortex burst location and separation/reattachment of flow on the upper surface of the wing produced large overshoots and hysteresis loops in normal force and pitching moment coefficients that were a strong function of mean oscillation angle and reduced frequency.

Brandon, Jay M.↗
NASA NTRS1988

Comparison of GPS surveys with historical triangulation surveys in the southern California borderland

Global plate models predict about 56 mm/yr of motion between the North American and Pacific plates along the plate boundary in southern California, while geodetic and Holocene geological data suggest only 34 mm/yr on the San Andreas fault. Deformation in the Great Basin does not explain this discrepancy, and it has been suggested that faulting in the offshore of southern California could account for some of the discrepancy. Evidence of deformation in the offshore region of southern California is most abundant in the Santa Barbara Channel. Geological investigations of folding and faulting in this region, as well as earthquake investigations, indicate north-south shortening across the channel on the order of 10 to 20 mm/yr. The most rapid rates occur to the east of the channel in the Ventura Basin. South of the Santa Barbara Channel, though, evidence for deformation is limited to seismicity studies which are sparse. Seismic events are abundant in this area, but their implication for the amount of deformation in the offshore is unclear. GPS measurements made between June 1986 and May 1988 have been used to obtain vector positions for several stations at which historical first order triangulation observations were performed between the late 1800's and the mid 1900's between the coast of southern California and the nearby offshore islands. By comparing the spheroidal angles obtained from the GPS positions with the the previously observed triangulation data, shear strain rates can be calculated for the region using Frank's method. These results seem to suggest that shear strain deformation occurs in the offshore of southern California as a result of north to north-west shortening. That deformation is most active in the Santa Barbara Channel region and least active between Catalina and San Nicholas islands. Just how much of the missing plate motion can be accounted for by this deformation is not known at this time and will have to await further analysis.

Webb, Frank H.↗
NASA NTRS1990

Differential Radar Interferometry Maps Changes In Elevation

Differential radar interferometry uses data from synthetic-aperture radar (SAR). Three passes of SAR yield three amplitude-and-phase images, from which two interferograms (phase-difference images) made. Interferograms used to make third, "double-difference" interferogram indicating vertical motion of terrain between passes. Vertical earthquake motions as small as 1 cm detectable. Used to make extensive, accurate maps of such geophysical phenomena as heaving and buckling in fault zones, motions to tectonic plates, residual displacements from earthquakes, motions from prevolcanic swelling, motions of glaciers, tides, and thermal expansion of mountains from diurnal heating.

Gabriel, Andrew K.↗
NASA NTRS1977

Global plate tectonics and the secular motion of the pole

Astronomical data compiled during the last 70 years by the international organizations providing the coordinates of the instantaneous pole clearly shows a persistent drift of the mean pole. The differential contributions to the earth's second-order tensor of inertia were obtained and applied, resulting in no significant displacement of the earth's principal axis. In view of the above, the effect that theoretical geophysical models for absolute plate velocities may have on an apparent displacement of the mean pole as a consequence of station drifting was analyzed. The investigation also reports new values for the crustal tensor of inertia (assuming an ellipsoidal earth) and the orientation of its axis of figure, reopening the old speculation of a possible sliding of the whole crustover the upper mantle, including the supporting geophysical and astronomic evidence.

Soler, T.↗
NASA NTRS1989

Rate of change of the Quincy-Monument Peak baseline from a translocation analysis of Lageos laser range data

Translocation studies of Lageos laser range data from Quincy and Monument Peak in California observed during 1984-1987 suggest that plate tectonic motion across the San Andreas fault system in the direction of the baseline between the two stations is uniform at a rate of -30(+ or - 3) mm/yr. Changes in the components of the baseline vector were inferred from repeat determinations using the solutions from successive 0.5-year intervals. The changes in the vertical and transverse components of the Quincy-Monument Peak baseline are -0.4(+ or - 5) mm/yr and +14(+ or -5) mm/yr, respectively. The vertical component determinations attest to the height stability of the laser ranging method. Lageos measurements made from Quincy and Monument Peak before 1984 are inaccurate enough to limit their usefulness for plate tectonic studies.

Stolz, A.↗
NASA NTRS1974

A summary of ERTS data applications in Alaska

ERTS has proven to be an exceedingly useful tool for the preparation of urgently needed resource surveys in Alaska. For this reason the wide utilization of ERTS data by federal, state and industrial agencies in Alaska is increasingly directed toward the solution of operational problems in resource inventories, environmental surveys, and land use planning. Examples of some applications are discussed in connection with surveys of potential agricultural lands; mapping of predicted archaeological sites; permafrost terrain and aufeis mapping; snow melt enhancement from Prudhoe Bay roads; geologic interpretations correlated ith possible new petroleum fields, with earthquake activity, and with plate tectonic motion along the Denali fault system; hydrology in monitoring surging glaciers and the break-up characteristics of the Chena River watershed; sea-ice morphology correlated with marine mammal distribution; and coastal sediment plume circulation patterns.

Miller, J. M.↗
NASA NTRS1978

Applications of Geodesy to Geodynamics, an International Symposium

Geodetic techniques in detecting and monitoring geodynamic phenomena are reviewed. Specific areas covered include: rotation of the earth and polar motion; tectonic plate movements and crustal deformations (space techniques); horizontal crustal movements (terrestrial techniques); vertical crustal movements (terrestrial techniques); gravity field, geoid, and ocean surface by space techniques; surface gravity and new techniques for the geophysical interpretation of gravity and geoid undulation; and earth tides and geodesy.

Mueller, I. I.↗
NASA NTRS1980

Radar, an optimum remote-sensing tool for detailed plate tectonic analysis and its application to hydrocarbon exploration (an example in Irian Jaya Indonesia)

Geometric, geomorphic, and structural information derived from the examination of radar imagery and combined with geologic and geophysical evidences strongly indicates that Salawati Island was attached to the Irian Jaya mainland during the time of Miocene lower Pliocene reef development, and that it was separated in middle Pliocene to Pleistocene time, opening the Sele Strait rift zone. The island moved 17.5 km southwestward after an initial counterclockwise rotation of 13 deg. The rift zone is subsequent to the creation of the large left lateral Sorong fault zone that is part of the transitional area separating the westward-moving Pacific plate from the relatively stable Australian plate. The motion was triggered during a widespread magmatic intrusion of the Sorong fault zone, when the basalt infiltrated a right lateral fault system in the area of the present Sele Strait.

Froidevaux, C. M.↗
NASA NTRS1982

The dryout region in frictionally heated sliding contacts

Some conditions under which boiling and two-phase flow can occur in or near a wet sliding contact are determined and illustrated. The experimental apparatus consisted of a tool pressed against an instrumented slider plate and motion picture sequences at 4000 frames/sec. The temperature and photographic data demonstrated surface conditions of boiling, drying, trapped gas evolution (solutions), and volatility of fluid mixture components. The theoretical modeling and analysis are in reasonable agreement with experimental data.

Hendricks, R. C.↗
NASA NTRS1982

The dryout region in frictionally heated sliding contacts

Some conditions under which boiling and two-phase flow can occur in or near a wet sliding contact are determined and illustrated. The experimental apparatus consisted of a tool pressed against an instrumented slider plate and motion picture sequences at 4000 frames/sec. The temperature and photographic data demonstated surface conditions of boiling, dry, trapped gas evolution (solutions), and volatility of fluid mixture components. The theoretical modeling and analysi are in reasonable agreement with experimental data. Previously announced in STAR as N82-28574

Hendricks, R. C.↗
NASA NTRS1984

Geodynamics

The status of space geodynamics is examined, major scientific questions that need to be addressed are identified, and program activities are recommended for the next decade. Progress made in measuring tectonic plates, polar motion, and coupling of fluid motion of the Earth's core to the mantle is reviewed.

Walter, L. S.↗
NASA NTRS1988

A physical model for earthquakes. I - Fluctuations and interactions. II - Application to southern California

The idea that earthquakes represent a fluctuation about the long-term motion of plates is expressed mathematically through the fluctuation hypothesis, under which all physical quantities which pertain to the occurance of earthquakes are required to depend on the difference between the present state of slip on the fault and its long-term average. It is shown that under certain circumstances the model fault dynamics undergo a sudden transition from a spatially ordered, temporally disordered state to a spatially disordered, temporally ordered state, and that the latter stages are stable for long intervals of time. For long enough faults, the dynamics are evidently chaotic. The methods developed are then used to construct a detailed model for earthquake dynamics in southern California. The result is a set of slip-time histories for all the major faults, which are similar to data obtained by geological trenching studies. Although there is an element of periodicity to the events, the patterns shift, change and evolve with time. Time scales for pattern evolution seem to be of the order of a thousand years for average recurring intervals of about a hundred years.

Rundle, John B.↗
NASA NTRS1991

The evolution of volcanism, tectonics, and volatiles on Mars - An overview of recent progress

Significant results of the 'Mars: Evolution of Volcanism, Tectonics, and Volatiles' (MEVTV) project are presented. The data for the project are based on geological mapping from the Viking images, petrologic and chemical analyses of SNC meteorites, and both mapping and temporal grouping of major fault systems. The origin of the planet's crustal dichotomy is examined in detail, the kinematics and formation of wrinkle ridges are discussed, and some new theories are set forth. Because the SNC meteorites vary petrologically and isotopically, the sources of the parental Martian magma are heterogeneous. Transcurrent faulting coupled with the extensional strains that form Valles Marineris suggest early horizontal movement of lithospheric blocks. A theory which connects the formation of the crustal dichotomy to the Tharsis region associates the horizontal motions with plate tectonics that generated a new lithosphere.

Zimbelman, James R.↗
NASA NTRS1994

GPS Measurements of the Baseline Between Quincy and Platform Harvest

As part of TOPEX altimeter verification, the Global Positioning System has been used to measure the baseline between the verification site at oil platform Harvest and a GPS antenna collocated with the satellite laser ranging site at Quincy, California.

GPS measurements geodesy tectonic plate motion↗
NASA NTRS2012

Plate Margin Deformation and Active Tectonics Along the Northern Edge of the Yakutat Terrane in the Saint Elias Orogen, Alaska and Yukon, Canada

The northwest directed motion of the Pacific plate is accompanied by migration and collision of the Yakutat terrane into the cusp of southern Alaska. The nature and magnitude of accretion and translation on upper crustal faults and folds is poorly constrained, however, due to pervasive glaciation. In this study we used high-resolution topography, geodetic imaging, seismic, and geologic data to advance understanding of the transition from strike-slip motion on the Fairweather fault to plate margin deformation on the Bagley fault, which cuts through the upper plate of the collisional suture above the subduction megathrust. The Fairweather fault terminates by oblique-extensional splay faulting within a structural syntaxis, allowing rapid tectonic upwelling of rocks driven by thrust faulting and crustal contraction. Plate motion is partly transferred from the Fairweather to the Bagley fault, which extends 125 km farther west as a dextral shear zone that is partly reactivated by reverse faulting. The Bagley fault dips steeply through the upper plate to intersect the subduction megathrust at depth, forming a narrow fault-bounded crustal sliver in the obliquely convergent plate margin. Since . 20 Ma the Bagley fault has accommodated more than 50 km of dextral shearing and several kilometers of reverse motion along its southern flank during terrane accretion. The fault is considered capable of generating earthquakes because it is linked to faults that generated large historic earthquakes, suitably oriented for reactivation in the contemporary stress field, and locally marked by seismicity. The fault may generate earthquakes of Mw <= 7.5.

Bruhn, Ronald L.↗
NASA NTRS1992

Global tectonics and space geodesy

Much of the success of plate tectonics can be attributed to the near rigidity of tectonic plates and the availability of data that describe the rates and directions of motion across narrow plate boundaries of about 1 to 60 kilometers. Nonetheless, many plate boundaries in both continental and oceanic lithosphere are not narrow but are hundreds to thousands of kilometers wide. Wide plate boundary zones cover approximately 15 percent of earth's surface area. Space geodesy, which includes very long baseline radio interferometry, satellite laser ranging, and the global positioning system, provides the accurate long-distance measurements needed to estimate the present motion across and within wide plate boundary zones. Space geodetic data show that plate velocities averaged over years are remarkably similar to velocities avaraged over millions of years.

Gordon, Richard G.↗