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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Direct observations of passages of the distant neutral line (80-140 RE) following substorm onsets - ISEE-3

Specific events recorded by ISEE-3 passage through the earth magnetotail at 80-140 earth radii are discussed. The data were taken during March 20-28, 1983, when Kp ranged from +6 to -40, and included both plasma and magnetic field signatures. Magnetic field polar angle reversals from N-S flows were detected, along with alteration in the bulk plasma flow from tailward to stagnation. Tailward flow was associated with negative field values, while stagnation was mainly present with positive field values. The tail plasma at 100 radii exhibited changes shortly after a substorm event which featured particle ejection at 6.6 earth radii. The plasma sheet swept by the events could have a 25-50 radii length scale.

Baker, D. N.↗
NASA NTRS1984

Plasmasheet magnetic fields in the distant tail

Data from two deep passes of ISEE-3 through the earth's magnetotail are used to discuss the evolution of the plasmasheet magnetic field as a function of radial distance and geomagnetic activity (Kp). Attention is focused on plasmasheet intervals lasting at least 10 min as recorded during passes lasting 3 and 5 mos with apogees of 221 and 238 earth radii (ER). The dependencies of the By and Bz components on Kp were minimal, although Bz displayed a radial dependence. No relationship was observed between By and Bz. The Bz component changed from a northward orientation at 60-100 ER to a N-S dependence at 200-238 ER. Variations in field measurements indicated turbulence throughout the plasmasheet, also independent of Kp. The data support formation of a plasmoid during periods of high Kp, and can serve as limiting conditions for developing more accurate magnetotail models.

Tsurutani, B. T.↗
NASA NTRS1984

Performance capabilities of the 12-centimeter Xenon ion thruster

The 8- and 12-cm mercury ion thruster systems were developed primarily to provide N-S station keeping of satellites with masses up to about 1800 to 3600 kg respectively. The on-orbit propulsion requirements of recently proposed Large Space Systems (LSS) are beyond the thrust capabilities of the baseline 8- and 12-cm thruster systems. This paper presents a characterization of the performance capabilities of the 12-cm Xenon ion thruster to enable an evaluation of its application to LSS auxiliary propulsion requirements. With minor thruster modifications and simplifications the thrust was increased to 64 mN, a factor of six over the baseline 12-cm mercury thruster performance. The thruster was operated over a range of specific impulse of about 2000 to 4000 seconds and at total efficiencies up to 68.0 percent. The operating levels reached in this study were found to be close to the operating limits of the thruster design in terms of perveance, grid breakdown voltage and thruster component temperatures such as those of the magnets and cathode baffle.

Mantenieks, M.↗
NASA NTRS1985

Numerical simulation in three space dimensions of time-dependent thermal convection in a rotating fluid

Three-dimensional time-dependent convection in a plane layer of fluid, uniformly heated from below and subject to vertical shear and to rotation about an axis tilted from the vertical, was simulated by the numerical solution of the Boussinesq equations, including all Coriolis terms. Rotation about a vertical axis produces smaller convection cells with diminished heat fluxes and considerable vorticity. When the rotation axis is tilted from the vertical to represent tropical latitudes, the convection cells become elongated in a N-S direction. Imposed flows with constant vertical shear produce convective rolls aligned with the mean flow. When the rotation vector is tilted from the vertical, the competing effects due to rotation and shear can stabilize the convective motions.

Hathaway, D. H.↗
NASA NTRS1986

The Kolar Schist Belt: A possible Archaean suture zone

The Kolar Schist Belt represents a N-S trending discontinuity in the structures, lithologies, and emplacement and metamorphic ages of late Archean gneisses. The suggestion of a much older basement on the west side of the belt is not seen on the east. Within the schist belt amphibolites from each side have distinctly different chemical characteristics, suggesting different sources at similar mantle depths. These amphibolites were probably not part of a single volcanic sequence, but may have formed about the same time in two completely different settings. Could the amphibolites with depleted light REE patterns represent Archean ocean floor volcanics which are derived from a mantle source with a long term depletion of the light REE? Why are the amphibolites giving an age which may be older than the exposed gneisses immediately on either side of the belt? These results suggest that it is necessary to seriously consider whether the Kolar Schist Belt may be a suture between two late Archean continental terranes.

Hanson, G. N.↗
NASA NTRS1986

A study of hard X-ray associated meter-decameter bursts observed on December 19, 1979

The results of a study of the relationship of a complex meter-decameter wavelength radio burst observed with the Clark Lake E-W and N-S interferometers, with a hard X-ray burst observed with the X-ray spectrometer aboard ISEE-3 are presented. The radio burst consisted of several type III's, reverse drift type III's, a U burst, and type II and type IV bursts. The X-ray emission was also complex. The radio as well as hard X-ray emissions were observed before the flash phase of the flare; they were not always associated and it is conjectured that this may constitute evidence for acceleration of electrons high in the corona. On the other hand, all components of the reverse drift burst were associated with hard X-ray subpeaks, indicating multiple injection of electron beams along field lines with different density gradients. While the type II burst appeared to be related to the hard X-ray burst, a detailed correspondence between individual features of the radio and hard X-ray burst emissions could not be found. The type IV burst started after all hard X-ray emissions ceased. Its source appeared to be a magnetic arch, presumably containing energetic electrons reponsible for the gyrosynchrotron radiation of type IV.

Kundu, M. R.↗
NASA NTRS1986

Simultaneous fine structure observation of wind and temperature profiles by the Arecibo 430-MHz radar and in situ measurements

A simultaneous campaign of balloon and radar measurements took place on March 14 to 16, 1984, above the Arecibo 430-MHz radar. This radar was operating with a vertical resolution of 150 m following two antenna beam directions: 15 deg. from the zenith, respectively, in the N-S and E-W directions. The main results concerning the comparison between the flight and simultaneous radar measurements obtained on March 15, 1984 are analyzed. The radar return power profile (S/N ratio in dB) exhibits maxima which are generally well correlated with step-like structures in the potential temperature profile. These structures are generally considered as the consequence of the mixing processes induced by the turbulence. A good correlation appears in the altitude range 12.5 to 19 km between wind shears induced by a wave structure observed in the meridional wind and the radar echo power maxima. This wave structure is characterized by a vertical wavelength of about 2.5 km, and a period in the range 30 to 40 hours. These characteristics are deduced from the twice daily rawinsonde data launched from the San Juan Airport by the National Weather Service. These results pointed out an example of the interaction between wave and turbulence in the upper troposphere and lower stratosphere. Turbulent layers are observed at locations where wind shears related to an internal inertia-gravity wave are maxima.

Thomas, D.↗
NASA NTRS1986

Horizontal wind perturbations and their relation to transient internal gravity waves

Horizontal winds as measured with the Saskatoon MF radar exhibit wind fluctuations which have preferred directions toward north or south in the period range 0 to 60 min at heights between about 60 and 110 km. Longer period perturbations (approx 1-6 h) tend to have an additional maximum of direction frequencies in the E-W sector.The polarization effect analyzed for more than 6 years shows regular changes with season. The main features of the seasonal variations of the direction distributions can be explained by directional filtering of vertically propagating nonstationary gravity waves and appropriate changes of the wave source strength and position in the troposphere. The N-S polarization of the gravity-wave field appears to result in meridional wind reversals with height above the mesopause.

Ebel, A.↗
NASA NTRS1986

Comparison of medium frequency pulsed radar interferometer and correlation analysis winds, part 2

In order to test whether the chosen Doppler peaks represent localized scatters in motion, as opposed to some sort of integrated composite, an attempt was made to determine the change in position of single scatterers over a series of sequential records. A four-antenna system was employed which had 1 degree of freedom in phase. Due to limitations N-S linear transmission and E-W linear reception were used. The Doppler frequency peak selection criteria were that at least two of the four power spectra should have a local peak, and that normalized phase discrepancy, should be less than 0.3. The lack of success in tracking individual scatters seems to suggest a short lifetime. If this is the case, then the present experiment is not able to resolve the difference found between the correlation analysis true velocity and the interferometer value. On the other hand, it appears that the interferometer may be of some use in tracking waves.

Meek, C. E.↗
NASA NTRS1986

The conductance of auroral magnetic field lines

DE-1 high-resolution double-probe electric-field data and simultaneous magnetic-field measurements are reported for two 1981 events with large electric fields which reversed over short distances. The data are presented graphically and analyzed in detail. A field-line conductance of about 1 nmho/sq m is determined for both upward and downward currents, and the ionospheric conductivity is shown, in the short-wavelength limit, to have little effect on the relationship between the (N-S) electric and (E-W) magnetic fields above the potential drop parallel to the magnetic-field lines. The results are found to be consistent with a linear relationship between the field-aligned current density and the parallel potential drop.

Weimer, D. R.↗
NASA NTRS1986

Multitasking the code ARC3D

The CRAY multitasking system was developed in order to utilize all four processors and sharply reduce the wall clock run time. This paper describes the techniques used to modify the computational fluid dynamics code ARC3D for this run and analyzes the achieved speedup. The ARC3D code solves either the Euler or thin-layer N-S equations using an implicit approximate factorization scheme. Results indicate that multitask processing can be used to achieve wall clock speedup factors of over three times, depending on the nature of the program code being used. Multitasking appears to be particularly advantageous for large-memory problems running on multiple CPU computers.

Barton, John T.↗
NASA NTRS1990

FIRE aircraft observations of horizontal and vertical transport in marine stratocumulus

A major goal of research on marine stratocumulus is to try to understand the processes that generate and dissipate them. One approach to studying this problem is to investigate the boundary layer structure in the vicinity of a transition from a cloudy to a cloud-free region to document the differences in structure on each side of the transition. Since stratiform clouds have a major impact on the radiation divergence in the boundary layer, the transition from a cloudy to a clear boundary layer is a region of large horizontal inhomogeneity in air temperature and turbulence intensity. This leads to a considerable difference in horizontal and vertical transports between the cloudy and cloud-free regions. Measurements are used from the NCAR Electra aircraft during flights 5 (7 July 1987) and 10 (18 July 1987) of FIRE for this purpose. Flight 5 coincided with a LANDSAT overflight, and was designed to investigate the transition across a well-defined N-S cloud boundary, since the LANDSAT image can document the cloud cover in considerable detail. Turbulence legs were flown about 60 km on both sides of the cloud boundary. Flight 10 was flown at night in an area of scattered small cumuli and broken cloud patches.

Paluch, Ilga R.↗
NASA NTRS1990

Spatial variability of rain rate and slant path attenuation distributions at 28 GHz in the mid-Atlantic coast region of the United States

Rain rate and corresponding estimated slant-path attenuation distributions derived from two years of measurements are presented for a network of nine rain-gage sites located in a region with extent 70 km N-S and 47 km E-W in the mid-Atlantic coast of the U.S. near the NASA Wallops Flight Facility, VA. The network average rain-rate distribution was compared with a previously measured 6-year average at one of the site locations. Agreement in rain rates was found to be within approximately 1 mm/h over the percentage range of 1-0.01 percent of the year, signifying the constancy of the rain-rate climatology for the region, and implying an ergodic rainfall process. Slant-path attenuation statistics were estimated at 28.56 GHz by interfacing the measured rain-rate distributions at each of nine site locations with Crane's (1980) global model.

Goldhirsh, Julius↗
NASA NTRS1991

Experimental investigation of a unique airbreathing pulsed laser propulsion concept

Investigations were conducted into unique methods of converting pulsed laser energy into propulsive thrust across a flat impulse surface under atmospheric conditions. The propulsion experiments were performed with a 1-micron neodymium-glass laser at the Space Plasma Branch of the Naval Research Laboratory. Laser-induced impulse was measured dynamically by ballistic pendulums and statically using piezoelectric pressure transducers on a stationary impulse surface. The principal goal was to explore methods for increasing the impulse coupling performance of airbreathing laser-propulsion engines. A magnetohydrodynamic thrust augmentation effect was discovered when a tesla-level magnetic field was applied perpendicular to the impulse surface. The impulse coupling coefficient performance doubled and continued to improve with increasing laser-pulse energies. The resultant performance of 180 to 200 N-s/MJ was found to be comparable to that of the earliest afterburning turbojets.

Myrabo, L. N.↗
NASA NTRS1992

Heat transfer and pressure measurements and comparison with prediction for the SSME two-stage turbine

Time averaged Stanton number and surface pressure distributions are reported for the first stage vane row, the first stage blade row, and the second stage vane row of the Rocketdyne Space Shuttle Main Engine (SSME) two-stage fuel-side turbine. Unsteady pressure envelope measurements for the first blade are also reported. These measurements were made at 10 percent, 50 percent, and 90 percent span on both the pressure and suction surfaces of the first stage components. Additional Stanton number measurements were made on the first stage blade platform, blade tip, and shroud, and at 50 percent span on the second vane. A shock tube was used as a short duration source of heated and pressurized air to which the turbine was subjected. Platinum thin film heat flux gages were used to obtain the heat flux measurements, while miniature silicon diaphragm flush-mounted pressure transducers were used to obtain the pressure measurements. The first stage vane Stanton number distributions are compared with predictions obtained using a version of STAN5 and quasi-3D Navier-Stokes solution. This same quasi-3D N-S code was also used to obtain predictions for the first blade and the second vane.

Dunn, M. G.↗
NASA NTRS1993

Lithology and chronology of ice-sheet fluctuations (magnetic susceptibility of cores from the western Ross Sea)

The goals of the marine geology part of WAIS include reconstructing the chronology and areal extent of ice-sheet fluctuations and understanding the climatic and oceanographic influences on ice-sheet history. As an initial step toward attaining these goals, down-core volume magnetic susceptibility (MS) logs of piston cores from three N-S transects in the western Ross Sea are compared. The core transects are within separate petrographic provinces based on analyses of till composition. The provinces are thought to reflect the previous locations of ice streams on the shelf during the last glaciation. Magnetic susceptibility is a function of magnetic mineral composition, sediment texture, and sediment density. It is applied in the western Ross Sea for two purposes: (1) to determine whether MS data differentiates the three transects (i.e., flow lines), and thus can be used to make paleodrainage reconstructions of the late Wisconsinan ice sheet; and (2) to determine whether the MS data can aid in distinguishing basal till diamictons from diamictons of glacial-marine origin and thus, aid paleoenvironmental interpretations. A comparison of the combined data of cores in each transect is presented.

Jennings, Anne E.↗
NASA NTRS1992

Time-averaged heat transfer and pressure measurements and comparison with prediction for a two-stage turbine

Time-averaged Stanton number and surface-pressure distributions are reported for the first-stage vane row and the first-stage blade row of the Rocketdyne Space Shuttle Main Engine two-stage fuel-side turbine. These measurements were made at 10 percent, 50 percent, and 90 percent span on both the pressure and suction surfaces of the component. Stanton-number distributions are also reported for the second-stage vane at 50 percent span. A shock tube is used as a short-duration source of heated and pressurized air to which the turbine is subjected. Platinum thin-film gages are used to obtain the heat-flux measurements and miniature silicone-diaphragm pressure transducers are used to obtain the surface pressure measurements. The first-stage vane Stanton number distributions are compared with predictions obtained using a quasi-3D Navier-Stokes solution and a version of STAN5. This same N-S technique was also used to obtain predictions for the first blade and the second vane.

Dunn, M. G.↗
NASA NTRS1993

Tectonics on Triton

Tectonic features on Triton have been mapped as part of a larger study of the geology of Triton. Few purely tectonic structures are found on Triton: some grabens and possibly some compressive ridges. However, most of the other structures seen (primarily cryovolcanic in origin) exhibit tectonic control. A regional tectonic network has the following dominant orientations: N-S, E-W, NE-SW, and NW-SE. Most of the orientations are consistent with tidal deformations related to Triton's decreasing orbital radius. Localized quasi-concentric patterns may be due to interior processes such as mantle plumes.

Croft, Steven K.↗