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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Asteroid rotation. I - Tabulation and analysis of rates, pole positions and shapes. II - A theory for the collisional evolution of rotation rates

Rotation properties and shape data for 182 asteroids are compiled and analyzed, and a collisional model for the evolution of the mean rotation rate of asteroids is proposed. Tabulations of asteroid rotation rates, taxonomic types, pole positions, sizes and shapes and plots of rotation frequency and light curve amplitude against size indicate that asteroid rotational frequency increases with decreasing size for all asteroids except those of the C or S classes. Light curve data also indicate that small asteroids are more irregular in shape than large asteroids. The dispersion in rotation rates observed is well represented by a three dimensional Maxwellian distribution, suggestive of collisional encounters between asteroids. In the proposed model, the rotation rate is found to tend toward an equilibrium value, at which spin-up due to infrequent, large collisions is balanced by a drag due to the larger number of small collisions. The lower mean rotation rate of C-type asteroids is attributed to a lower means density of that class, and the increase in rotation rate with decreasing size is interpreted as indicative of a substantial population of strong asteroids.

Harris, A. W.↗
NASA NTRS1990

Effects of an unbalanced magnetron in a unique dual-cathode, high rate reactive sputtering system

Simple plasma and magnetic field measurements are presented to illustrate the opportunities afforded by using unbalanced magnetrons in a dual-cathode system. The system employs a pair of opposed cathodes, 38 cm x 13 cm, placed 27.5 cm apart, to coat specimens mounted on a rotational substrate holder. Comparisons are drawn between the original 'balanced' magnetron and several unbalanced configurations in terms of field strengths, deposition rates, etching characteristics, and substrate ion current densities for the growth of TiN films. The effects of 'unbalancing' on the nature of the plasma within the 3D geometry of the deposition chamber are elucidated via plasma probe and magnetic field studies performed under a variety of conditions. All the unbalanced configurations examined provided enhanced ion bombardment at the surface of the growing film. The closed-field or opposed magnet geometry resulted in a threefold or greater increase in current density when compared with that obtained using the corresponding mirrored geometry under the same conditions.

Rohde, S. L.↗
NASA NTRS2002

Ablative Laser Propulsion Using Multi-Layered Material Systems

Experimental investigations are ongoing to study the force imparted to materials when subjected to laser ablation. When a laser pulse of sufficient energy density impacts a material, a small amount of the material is ablated. A torsion balance is used to measure the momentum produced by the ablation process. The balance consists of a thin metal wire with a rotating pendulum suspended in the middle. The wire is fixed at both ends. Recently, multi-layered material systems were investigated. These multi-layered materials were composed of a transparent front surface and opaque sub surface. The laser pulse penetrates the transparent outer surface with minimum photon loss and vaporizes the underlying opaque layer.

Nehls, Mary↗
NASA NTRS1988

Surface tension and bubble shapes in a partially filled rotating cylinder under low gravity

A computer algorithm is developed to simulate the profile of a free liquid surface for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry. The equilibrium shape of the free surface is governed by a balance of capillary, centrifugal, and gravity forces. The results can be used to determine the profile of a bubble at various rotating speeds under the gravity environments from low gravity, microgravity to zero-gravity. The present paper discusses the further extension of the study of the determination of bubble shape in a higher rotating speed container developed by Hung and Leslie.

Hung, R. J.↗
NASA NTRS1984

Rotary balance data and analysis for the X-29A airplane for an angle-of-attack range of 0 deg to 90 deg

The rotational aerodynamic characteristics are discussed for a 1/8 scale model of the X-29A airplane. The effects of rotation on the aerodynamics of the basic model were determined, as well as the influence of airplane components, various control deflections, and several forebody modifications. These data were measured using a rotary balance, over an angle of attack range of 0 to 90 deg, for clockwise and counter clockwise rotations covering an omega b/2V range of 0 to 0.4.

Ralston, J. N.↗
NASA NTRS1992

A balanced submatrix merging algorithm for multiprocessor architectures

In this article, a parallel algorithm which applies Givens rotations to selectively annihilate k(k + 1)/2 nonzero elements from two k x n(k not more than n) upper trapezoidal submatrices is described. The new algorithm is suitable for implementation on either a pair of directly connected local-memory processors or two clusters of multiple tightly-coupled processors. Analyses show that in both cases the proposed algorithms achieve optimal speed-up by balancing the work load distribution and masking interprocessor or intercluster communication by computation if k is much small than n. In the context of solving large scale least squares problems, this submatrix merging step is repetitively needed during the entire computation and, furthermore, there are usually many pairs of such submatrices to be merged with each submatrix stored in the memory of a processor or a cluster of processors. The proposed algorithm can be applied to each pair of submatrices concurrently, and thus parallelizes an important step in solving the least squares problems.

Chu, Eleanor↗
NASA NTRS1979

Experiments on multiplane balancing using a laser for material removal

The modifications of a flexible rotor system for two-plane laser balancing is described. Experimental testing of the laser material removal method for balancing through the first bending critical speed was demonstrated. The test rig, optical configuration, and a neodymium glass laser system were assembled and calibrated for static and rotating material removal rates. The laser control computer program was combined with the influence coefficient balancing process, resulting in a completely automated data acquisition, laser, and balancing system. The laser system rotor was balanced through the first bending critical speed using the laser material removal procedure to apply trial weights and correction weights without stopping the rotor.

Demuth, R. S.↗
NASA NTRS1980

The influence of wing, fuselage and tail design on rotational flow aerodynamics data obtained beyond maximum lift with general aviation configurations

The NASA Langley Research Center has initiated a broad general aviation stall/spin research program. A rotary balance system was developed to support this effort. Located in the Langley spin tunnel, this system makes it possible to identify an airplane's aerodynamic characteristics in a rotational flow environment, and thereby permits prediction of spins. This paper presents a brief description of the experimental set-up, testing technique, five model programs conducted to date, and an overview of the rotary balance results and their correlation with spin tunnel free-spinning model results. It is shown, for example, that there is a large, nonlinear dependency of the aerodynamic moments on rotational rate and that these moments are pronouncedly configuration-dependent. Fuselage shape, horizontal tail and, in some instances, wing location are shown to appreciably influence the yawing moment characteristics above an angle of attack of 45 deg.

Bihrle, W., Jr.↗
NASA NTRS1971

Film stability in a vertical rotating tube with a core-gas flow.

The linear hydrodynamic stability of a thin-liquid layer flowing along the inside wall of a vertical tube rotating about its axis in the presence of a core-gas flow is examined. The stability problem is formulated under the conditions that the liquid film is thin, the density and viscosity ratios of gas to liquid are small and the relative (axial) pressure gradient in the gas is of the same order as gravity. The resulting eigenvalue problem is first solved by a perturbation method appropriate to axisymmetric long-wave disturbances. The damped nature (to within the thin-film and other approximations made) of the nonaxisymmetric and short-wave disturbances is noted. In view of the limitations on a truncated perturbation solution when the disturbance wavenumber is not small, an initial value method using digital computer is presented. Stability characteristics of neutral, growing, and damped modes are presented showing the influences of rotation, surface tension, and the core-gas flow. Energy balance in a neutral mode is also illustrated.

Sarma, G. S. R.↗
NASA NTRS1974

Stability and control characteristics for the inner mold line configuration of the space shuttle orbiter (OA110)

Experimental aerodynamic investigations were conducted on a sting mounted 0.0405-scale representation of the -140A/B inner mold line (IML) space shuttle orbiter in 7.75 x 11 foot low speed wind tunnel, during the time period from 18 March 1974 to 20 March 1974. The primary test objectives were to establish basic longitudinal and lateral-directional stability and control characteristics for the IML orbiter. Additional configurations investigated were sealed elevon hingeline gaps, sealed rudder split line and hingeline gaps, larger radius leading edge on the vertical tail, and sealed speedbrake base. Aerodynamic force and moment data for the orbiter were measured in the body-axis system by an internally mounted, six-component strain gage balance. The model was sting mounted with the center of rotation located at approximately the wing trailing edge. The nominal angle of attack range was from -4 to +30 degrees. Yaw polars were recorded over a nominal yaw angle range from -14 to +14 degrees at constant angles of attack of 0, + or - 5, 10, 15 and 20 degrees.

Hughes, T.↗
NASA NTRS1974

Effect of ELEVON gap configurations on the longitudinal stability and control effectiveness of the 43-0 space shuttle orbiter (OA118)

Experimental aerodynamic investigations were conducted on a stingmounted 0.0405-scale representation of the 140A/B space shuttle orbiter in a 7.75 by 11-Foot low speed wind tunnel from April 24 to April 26, 1974. Differential inboard/outboard elevon panel deflections with the 6-inch gap were investigated to determine outboard panel aileron effectiveness. The elevons were deflected from +20 degrees to -40 degrees in various combinations. Aerodynamic force and moment data for the orbiter were measured in the body axis system by an internally mounted, six-component strain gage balance. The model was sting mounted with the center of rotation located at F.S. 60.172. The angle of attack range was from -10 degrees to +24 degrees.

Hughes, T.↗
NASA NTRS1985

Zonally averaged model of dynamics, chemistry and radiation for the atmosphere

A nongeostrophic theory of zonally averaged circulation is formulated using the nonlinear primitive equations on a sphere, taking advantage of the more direct relationship between the mean meridional circulation and diabatic heating rate which is available in isentropic coordinates. Possible differences between results of nongeostrophic theory and the commonly used geostrophic formulation are discussed concerning: (1) the role of eddy forcing of the diabatic circulation, and (2) the nonlinear nearly inviscid limit vs the geostrophic limit. Problems associated with the traditional Rossby number scaling in quasi-geostrophic formulations are pointed out and an alternate, more general scaling based on the smallness of mean meridional to zonal velocities for a rotating planet is suggested. Such a scaling recovers the geostrophic balanced wind relationship for the mean zonal flow but reveals that the mean meridional velocity is in general ageostrophic.

Tung, K. K.↗
NASA NTRS1991

The many faces of F stars - A rotational modulation study of Capella, Procyon, and Caph with the International Ultraviolet Explorer

Far-UV spectroscopy of the F stars Capella, Procyon, and Caph is reported. Although all three stars are regard as chromospherically 'active', none exhibited any sensible rotational modulations, indicating a smooth surface distribution of chromospheric emission. Balancing this nonsolar behavior are a variety of puzzling differences among the three stars. On the one hand, the C IV features of Procyon are narrow, while that of the Capella secondary and Caph are broad; differences in v sin i alone cannot explain the dichotomy. On the other hand, the high-excitation emissions of the Capella secondary and Procyon, but not Caph, exhibit statistically significant redshifts. The significance of these results is discussed in the light of the speculation by Simon and Drake (1989) that the X-ray deficient coronae of the early F dwarfs are produced by classical acoustic heating.

Ayres, Thomas R.↗
NASA NTRS1999

Physical Processes Governing Atmospheric Trace Constituents Measured from Aircraft in Pem-Tropics

The MIT group participated in seven publications in the 1999 issues of JGR with sections devoted in PEM-Tropics A, and had two papers which may be considered offshoots of these studies combined with commercial aircraft trace constituents data, one in Nature and one in EOS. In the meteorological overview we contributed a set of 1000 hPa divergent wind maps which we calculated from ECMWF data, meridional wind cross-sections, velocity potential and divergent wind maps, maps of stream function and rotational wind components, and vertical velocity profiles computed from mass balance, these all constituting part of the overall climatology. We also contributed material for the "stalactite" case observed from the DC-8 on September 3, 1996. This included a map of potential vorticity on 350 K, a cross-section of lidaro O3 a cross-section of potential vorticity along 140 deg W, and a map of specific humidity showing extreme dryness accompanying the high potential vorticity values and the high ozone values, all suggesting subsidence from the local stratosphere. In the paper on chemical characteristics we contributed 12 hour values of the 1000 hPa divergent wind component for the full period of PEM Tropics A; these were used by David Westberg to establish the air mass boundaries and in turn used by Gerry Gregory to set up a table of quantitative values of trace constituents and their ratios both sides of the boundaries.

Newell, Reginald E.↗
NASA NTRS2016

Rotary Balance Wind Tunnel Testing for the FASER Flight Research Aircraft

Flight dynamics research was conducted to collect and analyze rotary balance wind tunnel test data in order to improve the aerodynamic simulation and modeling of a low-cost small unmanned aircraft called FASER (Free-flying Aircraft for Sub-scale Experimental Research). The impetus for using FASER was to provide risk and cost reduction for flight testing of more expensive aircraft and assist in the improvement of wind tunnel and flight test techniques, and control laws. The FASER research aircraft has the benefit of allowing wind tunnel and flight tests to be conducted on the same model, improving correlation between wind tunnel, flight, and simulation data. Prior wind tunnel tests include a static force and moment test, including power effects, and a roll and yaw damping forced oscillation test. Rotary balance testing allows for the calculation of aircraft rotary derivatives and the prediction of steady-state spins. The rotary balance wind tunnel test was conducted in the NASA Langley Research Center (LaRC) 20-Foot Vertical Spin Tunnel (VST). Rotary balance testing includes runs for a set of given angular rotation rates at a range of angles of attack and sideslip angles in order to fully characterize the aircraft rotary dynamics. Tests were performed at angles of attack from 0 to 50 degrees, sideslip angles of -5 to 10 degrees, and non-dimensional spin rates from -0.5 to 0.5. The effects of pro-spin elevator and rudder deflection and pro- and anti-spin elevator, rudder, and aileron deflection were examined. The data are presented to illustrate the functional dependence of the forces and moments on angle of attack, sideslip angle, and angular rate for the rotary contributions to the forces and moments. Further investigation is necessary to fully characterize the control effectors. The data were also used with a steady state spin prediction tool that did not predict an equilibrium spin mode.

Denham, Casey↗
NASA NTRSDate not supplied

Preliminary Results Using Galvanic Vestibular Reduction as a Non-Pharmaceutical Tool for Motion Sickness Mitigation

Introduction: Alterations in vestibular sensory processing following G-transitions lead to motion sickness and spatial disorientation upon return to Earth’s gravity. The use of non-pharmaceutical mitigation for motion sickness has several potential advantages over drug treatment options. The purpose of this study was to validate a non-pharmaceutical tool using galvanic vestibular reduction (GVR) to mitigate G-transitional induced motion sickness and spatial disorientation. Methods: Using a repeated measures counter-balanced design, motion sickness and perception are obtained during Coriolis cross-coupling stimuli on a rotating chair across three GVR treatment interventions: throughout stimulus testing (prevention), following symptom onset (rescue), and placebo control. Subjects perform up to 10 sets of pitch head movements during constant rotation. For each set, head movement is cued every 10 seconds, alternating between pitch forward (chin resting to chest) and pitch backward (head upright) for a total of 7 forward and backward movements. During each head movement, subjects are asked to use a joystick to record the magnitude of their perceived rotation along all three axes. During the 2-minute pause between sets, motion sickness symptom scoring was obtained using the Pensacola Diagnostic Index and subject discomfort (0-20) ratings. Performance on a sensorimotor and cognitive test battery is measured during a fourth session to map changes in GVR level with functional performance. Results: Fifteen of 30 subjects have completed testing to date. Preliminary findings suggest GVR may be more effective in reducing symptoms in subjects who self-report less susceptibility on a pre-test motion sickness susceptibility questionnaire. Based on the joystick measures, GVR significantly reduces both the magnitude (mean 22% - 34%) and duration (mean 42% - 49%) of perceived roll and pitch sensation with head movements during constant rotation. It is important to note that comparable levels of GVR (up to 2.5mA) does not impair performance on a functional test battery including mobility and balance tasks. Discussion: Our preliminary findings suggest GVR may be useful in reducing disorienting roll and pitch illusions associated with Coriolis cross-coupling stimuli. While transfer to post-flight treatment will need to be validated, the potential advantages of our non-pharmaceutical countermeasure approach would be to provide rapid therapeutic effect while allowing continuous titration of GVR amplitude during recovery to maintain operational performance.

Gaurav Pradhan↗
NASA NTRS1991

Balance Function Disorders

Researchers at the Balance Function Laboratory and Clinic at the Minneapolis (MN) Neuroscience Institute on the Abbot Northwestern Hospital Campus are using a rotational chair (technically a "sinusoidal harmonic acceleration system") originally developed by NASA to investigate vestibular (inner ear) function in weightlessness to diagnose and treat patients with balance function disorders. Manufactured by ICS Medical Corporation, Schaumberg, IL, the chair system turns a patient and monitors his or her responses to rotational stimulation.

Source record↗
NASA NTRS2001

Single and Double ITCZ in Aqua-Planet Models with Globally Uniform Sea Surface Temperature and Solar Insolation: An Interpretation

It has been known for more than a decade that an aqua-planet model with globally uniform sea surface temperature and solar insolation angle can generate ITCZ (intertropical convergence zone). Previous studies have shown that the ITCZ under such model settings can be changed between a single ITCZ over the equator and a double ITCZ straddling the equator through one of several measures. These measures include switching to a different cumulus parameterization scheme, changes within the cumulus parameterization scheme, and changes in other aspects of the model design such as horizontal resolution. In this paper an interpretation for these findings is offered. The latitudinal location of the ITCZ is the latitude where the balance of two types of attraction on the ITCZ, both due to earth's rotation, exists. The first type is equator-ward and is directly related to the earth's rotation and thus not sensitive to model design changes. The second type is poleward and is related to the convective circulation and thus is sensitive to model design changes. Due to the shape of the attractors, the balance of the two types of attractions is reached either at the equator or more than 10 degrees away from the equator. The former case results in a single ITCZ over the equator and the latter case a double ITCZ straddling the equator.

Chao, Winston C.↗