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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 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Auroral vector electric field and particle comparisons. 1: Pre-midnight convection topology

Polar 3 was launched in northern Norway on January 27, 1974. Traversing nearly 3 deg latitude, the rocket crossed over a stable IBC II auroral arc in the positive bay region and continued north to a convection boundary which was identified as the Harang discontinuity. Measurement of the complete electric field vector, of energetic electrons and of the auroral N+2 and OI emissions were used to study the convection topology in the pre-magnetic-midnight region. A strong anticorrelation was observed between the electric field and the precipitating energetic electrons. The inverted V nature of the electron precipitations at the convection boundary, compared with the lack of such structure over the arc which was within the positive bay region, leads to the conclusion that auroral arcs are likely to be associated with inverted V type precipitation only at or poleward of convection boundaries and their eddy structures.

Maynard, N. C.↗
NASA NTRS1976

Ocean color spectra measured off the Oregon coast - Characteristic vectors

The ocean color spectrum is defined as the ratio of the spectrum of light upwelled from the sea to the spectrum of light incident on the sea surface. Ocean color spectra, observed from an airplane flown over waters off Oregon, are analyzed. The original spectra are resolved into fifty-five wavelength bands, each 5 nm wide. The shapes of these spectra are parameterized by, and shown to be accurately recoverable from, their first four principal components. These components are the scalar projections of each spectrum on the first four characteristic vectors of the sample covariance matrix. Regression equations are found with which phytoplankton pigment concentration and water transparency may be estimated as linear functions of the principal components. Pigment concentration estimates thus obtained are imprecise. The poor fit is at least partly due to the inappropriateness of the linear regression model and the neglect of other optically important substances typically present in sea water.

Mueller, J. L.↗
NASA NTRS1975

Hydrogen as an energy vector

The feasibility of utilizing hydrogen as an energy vector is considered, with special attention given to means of hydrogen production. The state-of-the-art in thermochemical processes is reviewed, and criteria for the technical and economic feasibility of large-scale thermochemical water splitting processes are presented. The production of hydrogen from coal and from photolysis of water is discussed.

Powers, W. D.↗
NASA NTRS1976

Approximate statistics of random vector magnitudes

Simple, rough approximations are presented for the mean and 99% values for random vectors of up to three independent elements. The accuracy of the provided approximate expressions has been investigated with the aid of Monte Carlo simulations involving 15 different combinations of the three statistical parameters. The results of this investigation are discussed.

Hagar, H., Jr.↗
NASA NTRS1976

Circularly polarized inertial wave vectors in rotating fluids

The Navier-Stokes equations for a rotating fluid are harmonically analyzed for planar motion in an infinite half-space. All solutions are shown to be a sum of two inertial wave vectors, one circularly polarized to the left (CPL) and the other circularly polarized to the right (CPR). These basic solutions are therefore presented in the same nomenclature and form as that found useful by experimentalists in analyzing flow data (called 'rotary spectra'). The CPL wave acts counter to the Coriolis force and consequently has a slower phase speed and larger damping than the CPR wave. At resonance (forcing frequency = Coriolis frequency) the CPR wave has an infinite phase speed and no damping and is the important component leading to the singular nature of the solutions for certain boundary conditions. All possible resonant singularities are explicitly shown. The unsteady development of these unbounded (limited space structure), cyclic (no time origin or structure) flows is presented to show that with time structure the resonant singularities evolve in a self-similar manner.

Cogley, A. C.↗
NASA NTRS1976

A vectored-engine-over-wing propulsive-lift concept

An experimental investigation has been conducted to evaluate a unique engine-over-wing propulsive-life scheme for providing maneuver improvement in the subsonic-transonic speed regime. The concept combines the benefits of vectored thrust for added circulation and spanwise blowing for leading-edge-vortex augmentation so as to provide full angle-of-attack aerodynamic improvements. Results of a series of wind tunnel tests employing a powered research model illustrate the propulsive/aerodynamic features of the concept.

Bradley, R. G.↗
NASA NTRS1976

Effects of upper-surface blowing and thrust vectoring on low speed aerodynamic characteristics of a large-scale supersonic transport model

Tests were conducted in a full scale tunnel to determine the low speed aerodynamic characteristics of a large scale arrow wing supersonic transport configured with engines mounted above the wing for upper surface blowing and conventional lower surface engines having provisions for thrust vectoring. Tests were conducted over an angle of attack range of -10 deg to 34 deg and for Reynolds numbers (based on the mean aerodynamic chord) of 5.17 x 1 million and 3.89 x 1 million. A limited number of tests were also conducted for the upper surface engine configuration in the high lift condition at an angle of sideslip of 10 deg in order to evaluate lateral directional characteristics and with the right engine inoperative in order to evaluate the engine out condition.

Coe, P. L., Jr.↗
NASA NTRS1977

Space shuttle engineering and operations support: Study of the effects of multiple ground updates on the accuracy of the onboard state vector with IMU only navigation

There are six cases considered: (1) no updates made during the flight, (2) one ground update in the vertical components only at the first practice separation minus 15 minutes, (3) one ground update in all components at the first practice separation minus 5 minutes, (4) updates 2 and 3 applied successively, (5) Case 4 plus an update in all components at the second separation attempt minus 3 minutes, and (6) one ground update at first separation attempt minus 5 minutes and a second update at second separation minus two minutes. The mission control simulation program, GROPER, was run using as radar input a tape containing radar derived state vectors for the trajectory.

Killen, R.↗
NASA NTRS1977

Three-dimensional vector modeling and restoration of flat finite wave tank radiometric measurements

The three-dimensional vector interaction between a microwave radiometer and a wave tank was modeled. Computer programs for predicting the response of the radiometer to the brightness temperature characteristics of the surroundings were developed along with a computer program that can invert (restore) the radiometer measurements. It is shown that the computer programs can be used to simulate the viewing of large bodies of water, and is applicable to radiometer measurements received from satellites monitoring the ocean. The water temperature, salinity, and wind speed can be determined.

Truman, W. M.↗
NASA NTRS1976

An analysis of satellite state vector observability using SST tracking data

Observability of satellite state vectors, using only SST tracking data was investigated by covariance analysis under a variety of satellite and station configurations. These results indicate very precarious observability in most short arc cases. The consequences of this are large variances on many state components, such as the downrange component of the relay satellite position. To illustrate the impact of observability problems, an example is given of two distinct satellite orbit pairs generating essentially the same data arc. The physical bases for unobservability are outlined and related to proposed TDRSS configurations. Results are relevant to any mission depending upon TDRSS to determine satellite state. The required mathematical analysis and the software used is described.

Englar, T. S., Jr.↗
NASA NTRS1977

Vectorization of linear discrete filtering algorithms

Linear filters, including the conventional Kalman filter and versions of square root filters devised by Potter and Carlson, are studied for potential application on streaming computers. The square root filters are known to maintain a positive definite covariance matrix in cases in which the Kalman filter diverges due to ill-conditioning of the matrix. Vectorization of the filters is discussed, and comparisons are made of the number of operations and storage locations required by each filter. The Carlson filter is shown to be the most efficient of the filters on the Control Data STAR-100 computer.

Schiess, J. R.↗
NASA NTRS1977

Asymptotic behavior of vector recurrences with applications

An investigation is conducted of the behavior of a vector recurrence relation under very weak assumptions. The obtained results are used in an analysis of the iterations for nonlinear equations and a study concerning the composition of such iterations. The results can be employed in studies of one-point iterations involving the use of memory elements. Iterations for solving nonlinear equations on parallel computers can be investigated.

Feldstein, A.↗
NASA NTRS1977

Auroral vector electric field and particle comparisons. I - Preliminary convection topology

Data obtained by Polar 3, launched from northern Norway January 27, 1974, are interpreted. The rocket, which traversed nearly 3 deg of latitude, crossed over a stable IBC II auroral arc in the positive bay region and continued north to a convection boundary which has been identified as the Harang discontinuity. Measurements of the complete electric field vector, of energetic electrons, and of auroral emissions were used to study the convection topology in the premagnetic midnight region. The inverted V nature of the electron precipitations at the convection boundary, compared with the lack of such structure over the arc which was within the positive bay region, is thought to indicate that auroral arcs are likely to be associated with inverted V type precipitation only at or poleward of convection boundaries and their eddy structures.

Maynard, N. C.↗
NASA NTRS1977

Auroral vector electric field and particle comparisons. II - Electrodynamics of an arc

The paper reports the results of energetic auroral electron and vector electric field measurements taken near and above a discrete auroral form and discusses their electrodynamic implications. Height-integrated Hall and Pedersen conductivities are computed in a quantitative fashion along the rocket payload trajectory. These conductivities, together with the electric fields, are used to describe the local auroral electrojet current system and to demonstrate an inverse relationship between the local electric field intensity and the height-integrated Pedersen conductivity. An analysis is presented of the divergence of both the electric field and the horizontal current as an effort to infer space charge densities and magnetic-field-aligned electrical currents near an auroral arc.

Evans, D. S.↗
NASA NTRS1977

A procedure for accurate calibration of the orientation of the three sensors in a vector magnetometer

Procedures are described for the calibration of a vector magnetometer of high absolute accuracy. It is assumed that the calibration will be performed in the magnetic test facility of Goddard Space Flight Center (GSFC). The first main section of the report describes the test equipment and facility calibrations required. The second presents procedures for calibrating individual sensors. The third discusses the calibration of the sensor assembly. In a final section recommendations are made to GSFC for modification of the test facility required to carry out the calibration procedures.

Mcpherron, R. L.↗
NASA NTRS1977

Concepts for the design of a completely active helicopter isolation system using output vector feedback

The theory of output vector feedback (a few measured quantities) is used to derive completely active oscillation isolation functions for helicopters. These feedback controller concepts are tested with various versions of the BO 105 helicopter and their performance is demonstrated. A compensation of the vibrational excitations from the rotor and harmonics of the number of blades are considered. There is also a fast and automatic trim function for maneuvers.

Schulz, G.↗
NASA NTRS1977

Performance of twin two-dimensional wedge nozzles including thrust vectoring and reversing effects at speeds up to Mach 2.20

Transonic tunnel and supersonic pressure tunnel tests were reformed to determine the performance characteristics of twin nonaxisymmetric or two-dimensional nozzles with fixed shrouds and variable-geometry wedges. The effects of thrust vectoring, reversing, and installation of various tails were also studied. The investigation was conducted statically and at flight speeds up to a Mach number of 2.20. The total pressure ratio of the simulated jet exhaust was varied up to approximately 26 depending on Mach number. The Reynolds number per meter varied up to 13.20 x 1 million. An analytical study was made to determine the effect on calculated wave drag by varying the mathematical model used to simulate nozzle jet-exhaust plume.

Capone, F. J.↗