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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Two-phase pressure drop of ammonia in small diameter horizontal tubes

Data for pressure drop in adiabatic two-phase ammonia flows in small diameter horizontal tubes are presented. The data has direct application to the sizing of the flow-through radiator tubes in the Space Station Freedom heat rejection system. The data are compared to existing correlations for pressure drop and are found to be significantly lower than the most commonly used correlations. However, several of the less commonly used correlations predict the data accurately. Alternate pressure drop prediction methods are explored and a recommendation is made for a method to accurately predict the pressure drop in two-phase ammonia flows in small horizontal tubes.

Ungar, Eugene K.↗
NASA NTRS1993

Analysis of the impact of Seasat scatterometer data and horizontal resolution on GLA model simulations of the QE II storm

The impact of the Seasat-A satellite scatterometer wind data and the increased horizontal resolution on the Goddard Laboratory for Atmospheres model predictions of the Queen Elizabeth II (QE II) storm of 9-11 September 1978 was evaluated for four different GLA model simulations of the QE II storm. It is shown that the largest impact on the simulation was caused by doubling the model's horizontal resolution from 4 deg x 5 deg to 2 deg x 2.5 deg. The increased resolution resulted in a storm track which was much closer to the one observed, with a much deeper surface development, a stronger mass circulation, stronger heating, and stronger increase of angular momentum.

Lenzen, Allen J.↗
NASA NTRS1993

Influence of horizontal inhomogeneity in the ionosphere on the reflection of Alfven waves

A study of the reflection of Alfven waves at a horizontally inhomogeneous ionosphere has been carried out. In this study, the Alfven speed above the ionosphere is assumed to be uniform and the ionosphere is treated as a height-integrated conducting slab. Analytical and numerical results indicate that the horizontal nonuniformity of the ionospheric conductivity can lead to a rotation of the reflected wave fields and cause field-aligned currents that originate in the ionosphere. A strong conductivity nonuniformity on the direction perpendicular to the incident wave field, large Hall to Pedersen conductivity ratios, and low conductivity values lead to a large rotation of the reflected wave field in the range from a few to 40 deg. The implications of the theoretical results for some ionospheric phenomena are presented, including comments on the Harang discontinuity and sun-aligned arcs.

Zhu, L.↗
NASA NTRS1955

Flight Measurements of Horizontal-Tail Loads on the Bell X-5 Research Airplane at a Sweep Angle of 58.7 Deg

A flight investigation was made at altitudes of 40,000, 25,000 and 15,000 feet to determine the horizontal-tail loads of the Bell X-5 research airplane at a sweep angle of 58.7 deg over the lift range of the airplane for Mach numbers from 0.61 to 1.00. The horizontal-tail loads were found to be nonlinear with lift throughout the lift ranges tested at all Mach numbers except at a Mach number of 1.00. The balancing tail loads reflected the changes which occur in the wing characteristics with increasing angle of attack. The nonlinearities were, in general, more pronounced at the higher angles of attack near the pitch-up where the balancing tail loads indicate that the wing-fuselage combination becomes unstable. No apparent effects of altitude on the balancing tail loads were evident over the comparable lift ranges of these tests at altitudes from 40,000 feet to 15,000 feet. Comparisons of balancing tail loads obtained from flight and windtunnel tests indicated discrepancies in absolute magnitudes, but the general trends of the data agree. Some differences in absolute magnitude may be accounted for by the tail load carried inboard of the strain-gage station and the load induced on the fuselage by the presence of the tail. These loads were not measured in flight.

Reed, Robert D↗
NASA NTRS1954

Wind-Tunnel Investigation at Low Speed of the Effects of Chordwise Wing Fences and Horizontal-Tail Position on the Static Longitudinal Stability Characteristics of an Airplane Model with a 35 Degree Sweptback Wing

Low-speed tests of a model with a wing swept back 35 degrees at the 0.33-chord line and a horizontal tail located well above the extended wing-chord plane indicated static longitudinal instability at moderate angles of attack for all configurations tested. An investigation therefore was made to determine whether the longitudinal stability could be improved by the use of chordwise wing fences, by lowering the horizontal tail, or by a combination of both. The results of the investigation showed that the longitudinal stability characteristics of the model with slats retracted could be improved at moderate angles of attack by placing chordwise wing fences at a spanwise station of about 73 percent of the wing semispan from the plane of symmetry provided the nose of the fence extended slightly beyond or around the wing leading edge.

Queijo, M J↗
NASA NTRS1954

Experimental investigation of the forces and moments due to sideslip of a series of triangular vertical and horizontal tail combinations at Mach numbers

An experimental investigation was made at Mach numbers of 1.62, 1.93, and 2.41 of a series of tail combinations consisting of triangular vertical tail attached symmetrically to a triangular horizontal tail to determine the lateral force, yawing moment, and rolling moment due to sideslip. The apex angles of both the vertical- and horizontal-tail surfaces were varied systematically in order to obtain results for an appreciable range of operating conditions. The results of the investigation indicated that, for tails having subsonic leading edges and supersonic trailing edges, the lateral-force derivative and the yawing-moment derivative were predicted satisfactorily by the method presented in NACA TN 3071 except when the leading edges approach a sonic condition. The theoretical rolling-moment derivative was in fair agreement with the experimental derivative. For the limited tests in which both the leading and trailing edges were supersonic, the prediction of the lateral-force derivative and the yawing-moment derivative obtained from NACA TN 2412 was in good agreement with the experimental derivatives, whereas the prediction of the rolling-moment derivative was fair.

Coletti, Donald E↗
NASA NTRS1950

Time histories of horizontal-tail loads, elevator loads, and deformations on a jet-powered bomber airplane during abrupt pitching maneuvers at approximately 20,000 feet

Time histories are presented of horizontal-tail loads, elevator loads, and deformations on a jet-powered bomber during abrupt pitching maneuvers at a pressure altitude of approximately 20,000 feet. The normal and pitching accelerations measured varied from -0.90b to 3.41g and from -0.73 to 0.80 radian per second per second (sic), respectively, with a Mach number variation of from 0.40 to o.75. The maximum horizontal-tail load measured was 17,250 pounds down. The maximum elevator load was 1900 pounds up. The stabilizer twisted a maximum of 0.76 degrees leading edge down at the tip. The greatest fuselage deflection at the tail was about 1.7 inches down.

Wiener, Bernard↗
NASA NTRS1992

NASA-ACEE/Boeing 737 graphite-epoxy horizontal stabilizer service

The 737 graphite-epoxy horizontal stabilizer was developed by Boeing as part of the NASA-ACEE (Aircraft Energy Efficiency) Advanced Composite Structures Program. NASA-ACEE programs challenged large-transport manufacturers to use graphite material in redesigning existing aircraft components. The goal of the program was to develop the necessary data and technology to achieve production commitments to advanced composites. Boeing designed, fabricated, and certified five shipsets of horizontal stabilizers for the 737-200 airframe. The program was initiated in July 1977 and certification was achieved in August 1982. Schedule highlights are shown. The work performed on this program is reported in NASA technical summaries and final reports. Boeing introduced the stabilizer into commercial operation in 1984, and has maintained surveillance for seven years of in-service evaluation. Outstanding performance was demonstrated with no service incidents attributed to the graphite-epoxy structure. Boeing will continue to monitor and support these aircraft, adding to the database of commercial composite experience.

Quinlivan, J. T.↗
NASA NTRS1994

A coronal magnetic field model with horizontal volume and sheet currents

When globally mapping the observed photospheric magnetic field into the corona, the interaction of the solar wind and magnetic field has been treated either by imposing source surface boundary conditions that tacitly require volume currents outside the source surface or by limiting the interaction to thin current sheets between oppositely directed field regions. Yet observations and numerical Magnetohydrodynamic (MHD) calculations suggest the presence of non-force-free volume currents throughout the corona as well as thin current sheets in the neighborhoods of the interfaces between closed and open field lines or between oppositely directed open field lines surrounding coronal helmet-streamer structures. This work presents a model including both horizontal volume currents and streamer sheet currents. The present model builds on the magnetostatic equilibria developed by Bogdan and Low and the current-sheet modeling technique developed by Schatten. The calculation uses synoptic charts of the line-of-sight component of the photospheric magnetic field measured at the Wilcox Solar Observatory. Comparison of an MHD model with the calculated model results for the case of a dipole field and comparison of eclipse observations with calculations for CR 1647 (near solar minimum) show that this horizontal current-current-sheet model reproduces polar plumes and axes of corona streamers better than the source-surface model and reproduces polar plumes and axes of corona streamers better than the source-surface model and reproduces coro nal helmet structures better than the current-sheet model.

Zhao, Xuepu↗
NASA NTRS1994

The horizontal-branch stars in globular clusters. 2: The second parameter phenomenon

Using synthetic horizontal-branch models, we have investigated the origin of the systematic variation in horizontal-branch (HB) morphology with galactocentric distance (R(sub G)) among globular clusters. The variations in He abundance, CNO abundance, and core mass required separately to explain this effect are inconsistent with either the observed properties of the RR Lyrae variables or the observed main-sequence turnoffs in the clusters. There is also no clear evidence that the trend with R(sub G) is related to the central concentrations, central densities, or absolute magnitudes of the clusters. The variations in cluster age required to explain this effect are not in conflict with any observations. A detailed comparison of our synthetic HB calculations with pairs of clusters of very different HB morphology but similar (Fe/H) reveals reasonably good agreement between the age differences inferred from HB morphology and the main-sequence turnoff. The major source of uncertainty is the need for ad hoc hypotheses in the modeling of the HB morphologies of a few peculiar clusters (e.g., NGC 6752). Nonetheless, there is firm evidence for age variations of several gigayears (as much as approximately 5 Gyr) among the halo globular clusters. Our results support the hypothesis of Searle & Zinn that the inner halo is more uniform in age and is older in the mean than the outer halo, and we estimate this difference to be approximately 2 Gyr.

Lee, Young-Wook↗
NASA NTRS1994

Microwave radiative transfer through horizontally inhomogeneous precipitating clouds

Recent advances in cloud microphysical models have led to realistic three-dimensional distributions of cloud constituents. Radiative transfer schemes can make use of this detailed knowledge in order to study the effects of horizontal as well as vertical inhomogeneities within clouds. This study looks specifically at the differences between three-dimensional radiative transfer results and those obtained by plane parallel, independent pixel approximations in the microwave spectrum. A three-dimensional discrete ordinates method as well as a backward Monte Carlo method are used to calculate realistic radiances emerging from the cloud. Analyses between these models and independent pixel approximations reveal that plane parallel approximations introduce two distinct types of errors. The first error is physical in nature and is related to the fact that plane parallel approximations do not allow energy to leak out of dense areas into surrouding areas. In general, it was found that these errors are quite small for emission-dominated frequencies (37 GHz and lower) and that physical errors are highly pronounced only at scattering frequencies (85 GHz) where large deviations and biases up to 8 K averaged over the entire cloud were found. The second error is more geometric in nature and is related to the fact that plane parallel approximations cannot accommodate physical boundaries in the horizontal dimension for off-nadir viewing angles. The geometric errors were comparable in magnitude for all frequencies. Their magnitude, however, depends on a number of factors including the scheme used to deal with the edge, the nature of the surface, and the viewing angle.

Roberti, Laura↗
NASA NTRS1998

Low Cost Propulsion Technology Testing at the Stennis Space Center: Propulsion Test Article and the Horizontal Test Facility

The need for low cost access to space has initiated the development of low cost liquid rocket engine and propulsion system hardware at the Marshall Space Flight Center. This hardware will be tested at the Stennis Space Center's B-2 test stand. This stand has been reactivated for the testing of the Marshall designed Fastrac engine and the Propulsion Test Article. The RP-1 and LOX engine is a turbopump fed gas generator rocket with an ablative nozzle which has a thrust of 60,000 lbf. The Propulsion Test Article (PTA) is a test bed for low cost propulsion system hardware including a composite RP-I tank, flight feedlines and pressurization system, stacked in a booster configuration. The PTA is located near the center line of the B-2 test stand, firing vertically into the water cooled flame deflector. A new second position on the B-2 test stand has been designed and built for the horizontal testing of the Fastrac engine in direct support of the X-34 launch vehicle. The design and integration of these test facilities as well as the coordination which was required between the two Centers is described and lessons learned are provided. The construction of the horizontal test position is discussed in detail. The activation of these facilities is examined and the major test milestones are described.

Fisher, Mark F.↗
NASA NTRS1998

Remote Sensing Measurements of Vertical and Horizontal Moisture Variations from Aircraft Instruments

The research in this paper focuses on describing vertical and horizontal of water vapor variability using two remote sensing aircraft instruments. To achieve this goal we will compare precipitable water and upper level humidity estimates derived from the each of the instruments. The Multispectral Atmospheric Mapping Sensor (MAMS) is a visible and infrared radiometer with similar channels to that of the GOES imager. MAMS has flown aboard the NASA ER-2 numerous times. It has been used to validate features observed with the previous series of GOES satellites. MAMS data has been used to study precipitable water and upper level water vapor as well as other geophysical parameters. MAMS provides the opportunity to obtain water vapor Imagery at 6.7 mm. Upper tropospheric humidity can be computed using this channel in a similar fashion to that of Soden and Bretherton. In addition to the water vapor channel, MAMS records data In 3 other Infrared channels and 8 visible and near Infrared bands at high spatial resolution (I 00 Abstract: m). The 1 1 and 12 mm infrared channels allow for the application of a split technique to derive total precipitable water. The Udar Atmospheric Sensing Experiment (LASE) which uses the Differential Absorption Udar (DIAL) technique for obtaining simultaneous water vapor and aerosol profiles through the entire troposphere. LASE operates In the 81 5 nm wavelength region and uses a double pulsed Ti:sapphire laser that is locked onto a water vapor line. LASE has good horizontal (IO km) and excellent vertical (300 m) resolution. MAMS and LASE collected data simultaneously on several ER-2 flights in September 1995. LASE mixing ratio profiles will be Integrated for comparison with MAMS precipitable water estimates and the upper tropospheric humidity will be computed for the layer observed by the MAMS 6.7 mm channel for comparison for this time period. Results show a significant correlation between the measurements of the two Instruments. Regions of high/low upper tropospheric humidity are apparent In measurements from both instruments. Also changes in boundary layer moisture depicted by LASE are reflected in the total precipitable water measured by MAMS.

Atkinson, R. J.↗
NASA NTRS1999

Physical Parameters of Hot Horizontal-Branch Stars in NGC 6752: Deep Mixing and Radiative Levitation

Atmospheric parameters (T(sub eff), log g and log n(sub He)/n(sub H-dot)) are derived for 42 hot horizontal branch (HB) stars in the globular cluster NGC 6752. For 19 stars Mg II and Fe II lines are detected indicating an iron enrichment by a factor 50 on average with respect to the cluster abundance whereas the magnesium abundances are consistent with the cluster metallicity. This finding adds to the growing evidence that radiative levitation plays a significant role in determining the physical parameters of blue HB stars. Indeed, we find that iron enrichment can explain part, but not all, of the problem of anomalously low gravities along the blue HB. Thus the physical parameters of horizontal branch stars hotter than about 11,500 K in NGC 6752, as derived in this paper, are best explained by a combination of helium mixing and radiative levitation effects.

Moehler, S.↗
NASA NTRS1999

Predicted Variations in Flow Patterns in a Horizontal CVD Reactor

Expressions in terms of common reactor operating parameters were derived for the ratio of the Grashof number to the Reynolds number, Gr/Re, the ratio of the Grashof to the square of 2 the Reynolds number, Gr/Re(exp 2), and the Rayleigh number, Ra. Values for these numbers were computed for an example horizontal CVD reactor and compared to numerical simulations to gauge their effectiveness as predictors of the presence or absence of transverse and longitudinal rolls in the reactor. Comparisons were made for both argon and hydrogen carrier gases over the pressure range 2- 101 kPa. Reasonable agreement was achieved in most cases when using Gr/Re to predict the presence of transverse rolls and Ra to predict the presence of longitudinal rolls. The ratio Gr/Re(exp 2) did not yield useful predictions regarding the presence of transverse rolls. This comparison showed that the ratio of the Grashof number to the Reynolds number, as well as the Rayleigh number, can be used to predict the presence or absence of transverse and longitudinal rolls in a horizontal CVD reactor for a given set of reactor conditions. These predictions are approximate, and care must be exercised when making predictions near transition regions.

Kuczmarski, Maria A.↗
NASA NTRS1999

On Relationships Between Horizontal Velocity Structure and Thermal Ion Upwellings at High Latitudes

Recent studies indicate that the vertical velocity of F region ion upwellings cannot be explained by frictional heating in the horizontal plane alone but requires additional energization sources. Processes involving velocity shear have recently been put forward as alternate mechanisms that can provide the energization in regions of smaller convection speeds. Studies show that structured flows can also give rise to significant upwelling of ions by seeding plasma waves that can potentially cause ion heating while Joule heating is relatively small. We provide a statistical analysis of the Dynamics Explorer 2 vertical and horizontal ion drift measurements that show further evidence for the significance of plasma wave energization process in regions of varying levels of Joule heating.

Kivanc, O.↗
NASA NTRS2001

Horizontal Wind Measurements using the HARLIE Holographic Lidar

We report the results of three campaigns in which the horizontal wind vector at cloud altitudes was measured using the holographic, conical-scan lidar HARLIE in its nadir-viewing mode. Measurements were made during the HOLO-1 and -2 tests in Utah and New Hampshire in March and June 1999, respectively, and at the DoE-ARM site in Oklahoma in September/October 2000. A novel algorithm facilitates the wind vector analysis of the HARLIE data. Observed wind velocity and direction were compared with radiosonde records and with other data obtained from video cloud imagery and independent lidar ranging. The results demonstrate good agreement between HARLIE data and the results of other methods. The conically scanning holographic lidar opens up new possibilities for obtaining the vertical profile of horizontal winds.

Wilkerson, Thomas↗