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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Flux-vector splitting and Runge-Kutta methods for the Euler equations

Runge-Kutta schemes have been used as a method of solving the Euler equations exterior to an airfoil. In the past this has been coupled with central differences and an artificial vesocity in space. In this study the Runge-Kutta time-stepping scheme is coupled with an upwinded space approximation based on flux-vector splitting. Several acceleration techniques are also considered including a local time step, residual smoothing and multigrid.

Turkel, E.↗
NASA NTRS1991

Rendezvous radar for the orbital maneuvering vehicle

This paper describes the development of the Rendezvous Radar Set (RRS) for the Orbital Maneuvering Vehicle (OMV) for the National Aeronautics and Space Administration (NASA). The RRS was to be used to locate, and then provide vectoring information to, target satellites (or Shuttle or Space Station) to aid the OMV in making a minimum-fuel-consumption approach and rendezvous. The RRS design is that of an X-Band, all solid-state, monopulse tracking, frequency hopping, pulse-Doppler radar system. The development of the radar was terminated when the OMV prime contract to TRW was terminated by NASA. At the time of the termination, the development was in the circuit design stage. The system design was virtually completed, the PDR had been held. The RRS design was based on Motorola's experiences, both in the design and production of radar systems for the US Army and in the design and production of hi-rel communications systems for NASA space programs. Experience in these fields was combined with the latest digital signal processor and micro-processor technology to design a light-weight, low-power, spaceborne radar. The antenna and antenna positioner (gimbals) technology developed for the RRS is now being used in the satellite-to-satellite communication link design for Motorola's Iridium telecommunications system.

Locke, John W.↗
NASA NTRS1992

NASA Marshall Space Flight Center Solar Observatory report, July - December 1991

A summary is given of the solar vector magnetic field, H-alpha, and white light observations made at the NASA/Marshall Space Flight Center (MSFC) Solar Observatory during its daily periods of observation. The MSFC Solar Observatory facilities consist of the Solar Magnetograph, an f-13, 30 cm Cassegrain system with a 3.5 cm image of the Sun housed on top of a 12.8 meter tower, a 12.5 cm Razdow H-alpha telescope housed at the base of the tower, an 18 cm Questar telescope with a full aperture white-light filter mounted at the base of the tower, a 30 cm Cassegrain telescope located in a second metal dome, and a 16.5 cm H-alpha telescope mounted on the side of the Solar Vector Magnetograph. A concrete block building provides office space, a darkroom for developing film and performing optical testing, a workshop, video displays, and a computer facility for data reduction.

Smith, James E.↗
NASA NTRS2023

In-Flight Validation of the Metis Visible-Light Polarimeter Coronagraph on Board Solar Orbiter

Context. The Metis coronagraph is one of the remote sensing instruments of the ESA-NASA Solar Orbiter mission. The goal for the instrument is to enable the study of the solar atmosphere and solar wind by simultaneously acquiring images of the solar corona at two different wavelengths: visible light (VL), within a band ranging from 580 nm to 640 nm, and ultraviolet light, in the HI Lyα 121.6 ± 10 nm. The visible-light channel of the coronagraph includes a polarimeter with electro-optically modulating liquid crystal variable retarders to measure the linearly polarized brightness of the K-corona and derive the electron density. Aims. In this paper, we present the first in-flight validation results of the Metis polarimetric channel together with a comparison to the on-ground calibrations. This paper seeks to validate the first use of an electro-optical device, the liquid crystal-based polarimeter, in deep space and within a hard radiation environment. Methods. We used the orientation of the K-corona’s linear polarization vector during the roll maneuvers of the Space Orbiter spacecraft for the in-flight calibration. Results. The Metis coronagraph on board the Solar Orbiter shows good agreement with the on-ground measurements. The in-flight validation confirms the expected performance of the visible-light channel polarimeter. Furthermore, a comparison between the first polarized brightness value obtained by Metis and the polarized brightness values obtained by the space-based coronagraph LASCO and the ground-based coronagraph K-Cor shows the consistency of the Metis calibrated results.

Sun: corona↗
NASA NTRS2009

Nozzle Side Load Testing and Analysis at Marshall Space Flight Center

Realistic estimates of nozzle side loads, the off-axis forces that develop during engine start and shutdown, are important in the design cycle of a rocket engine. The estimated magnitude of the nozzle side loads has a large impact on the design of the nozzle shell and the engine s thrust vector control system. In 2004 Marshall Space Flight Center (MSFC) began developing a capability to quantify the relative magnitude of side loads caused by different types of nozzle contours. The MSFC Nozzle Test Facility was modified to measure nozzle side loads during simulated nozzle start. Side load results from cold flow tests on two nozzle test articles, one with a truncated ideal contour and one with a parabolic contour are provided. The experimental approach, nozzle contour designs and wall static pressures are also discussed

Ruf, Joseph H.↗
NASA NTRS1980

SPAR and ASTP studies of plane-front solidification and magnetic properties of Bi/MnBi

Eutectic and off-eutectic Bi/MnBi compositions have been directionally solidified parallel, anti-parallel and perpendicular to the gravity vector in a one-g environment and in low-gravity during the ASTP flight. MnBi rod diameter and interparticle spacing distributions are similar for all gravity vector orientations when grown at high solidification rates in one-g. Previously reported ASTP results are explained by the existence of a metastable magnetic phase and off-eutectic solidification models.

Pirich, R. G.↗
NASA NTRS1980

Hyperstability in variable structure systems

A variable structure control law is a discontinuous feedback law whose coefficients switch on hypersurfaces defined in the state space. Feedback systems with variable structure control laws are often referred to as variable structure systems (VSS). The main feature of VSS is the sliding motion which can occur at the intersection of the switching surfaces. Demonstrating existence and reaching in the case of vector control in n-dimensional space is in general a problem in stability of nonlinear systems. The present investigation is concerned with the projection of motion on an m-dimensional subspace, taking into account aspects of the hyperstability concept in VSS design. The considered concepts are illustrated with the aid of an example.

Calise, A. J.↗
NASA NTRS1989

Creation of fully vectorized FORTRAN code for integrating the movement of dust grains in interplanetary environments

The main objective is to improve the performance of a specific FORTRAN computer code from the Planetary Sciences Division of NASA/Johnson Space Center when used on a modern vectorizing supercomputer. The code is used to calculate orbits of dust grains that separate from comets and asteroids. This code accounts for influences of the sun and 8 planets (neglecting Pluto), solar wind, and solar light pressure including Poynting-Robertson drag. Calculations allow one to study the motion of these particles as they are influenced by the Earth or one of the other planets. Some of these particles become trapped just beyond the Earth for long periods of time. These integer period resonances vary from 3 orbits of the Earth and 2 orbits of the particles to as high as 14 to 13.

Colquitt, Walter↗
NASA NTRS1991

NASA Marshall Space Flight Center solar observatory report, January - June 1991

Given here is a summary of the solar vector magnetic field, H-alpha, and white-light observations made at the NASA/Marshall Space Flight Center (MSFC) Solar Observatory during its daily periods of operation. The MSFC Solar Observatory facilities consist of the Solar Magnetograph, an f/13, 30-cm Cassegrain system with a 3.5-cm image of the Sun, housed on top of a 12.8-meter tower; a 12.5-cm Razdow H-alpha telescope housed at the base of the tower; an 18-cm Questar telescope with a full aperture white-light filter mounted at the base of the tower; a 30-cm Cassegrain telescope located in a second metal dome; and a 16.5-cm H-alpha telescope mounted on side of the Solar Vector Magnetograph. A concrete block building provides office space, a darkroom for developing film and performing optical testing, a workshop, video displays, and a computer facility for data reduction.

Smith, James E.↗
NASA NTRS1993

An investigative study of multispectral data compression for remotely-sensed images using vector quantization and difference-mapped shift-coding

A study is conducted to investigate the effects and advantages of data compression techniques on multispectral imagery data acquired by NASA's airborne scanners at the Stennis Space Center. The first technique used was vector quantization. The vector is defined in the multispectral imagery context as an array of pixels from the same location from each channel. The error obtained in substituting the reconstructed images for the original set is compared for different compression ratios. Also, the eigenvalues of the covariance matrix obtained from the reconstructed data set are compared with the eigenvalues of the original set. The effects of varying the size of the vector codebook on the quality of the compression and on subsequent classification are also presented. The output data from the Vector Quantization algorithm was further compressed by a lossless technique called Difference-mapped Shift-extended Huffman coding. The overall compression for 7 channels of data acquired by the Calibrated Airborne Multispectral Scanner (CAMS), with an RMS error of 15.8 pixels was 195:1 (0.41 bpp) and with an RMS error of 3.6 pixels was 18:1 (.447 bpp). The algorithms were implemented in software and interfaced with the help of dedicated image processing boards to an 80386 PC compatible computer. Modules were developed for the task of image compression and image analysis. Also, supporting software to perform image processing for visual display and interpretation of the compressed/classified images was developed.

Jaggi, S.↗
NASA NTRS1992

A static investigation of the thrust vectoring system of the F/A-18 high-alpha research vehicle

A static (wind-off) test was conducted in the static test facility of the Langley 16-foot Transonic Tunnel to evaluate the vectoring capability and isolated nozzle performance of the proposed thrust vectoring system of the F/A-18 high alpha research vehicle (HARV). The thrust vectoring system consisted of three asymmetrically spaced vanes installed externally on a single test nozzle. Two nozzle configurations were tested: A maximum afterburner-power nozzle and a military-power nozzle. Vane size and vane actuation geometry were investigated, and an extensive matrix of vane deflection angles was tested. The nozzle pressure ratios ranged from two to six. The results indicate that the three vane system can successfully generate multiaxis (pitch and yaw) thrust vectoring. However, large resultant vector angles incurred large thrust losses. Resultant vector angles were always lower than the vane deflection angles. The maximum thrust vectoring angles achieved for the military-power nozzle were larger than the angles achieved for the maximum afterburner-power nozzle.

Mason, Mary L.↗
NASA NTRS1993

Optimizing interplanetary trajectories with deep space maneuvers

Analysis of interplanetary trajectories is a crucial area for both manned and unmanned missions of the Space Exploration Initiative. A deep space maneuver (DSM) can improve a trajectory in much the same way as a planetary swingby. However, instead of using a gravitational field to alter the trajectory, the on-board propulsion system of the spacecraft is used when the vehicle is not near a planet. The purpose is to develop an algorithm to determine where and when to use deep space maneuvers to reduce the cost of a trajectory. The approach taken to solve this problem uses primer vector theory in combination with a non-linear optimizing program to minimize Delta(V). A set of necessary conditions on the primer vector is shown to indicate whether a deep space maneuver will be beneficial. Deep space maneuvers are applied to a round trip mission to Mars to determine their effect on the launch opportunities. Other studies which were performed include cycler trajectories and Mars mission abort scenarios. It was found that the software developed was able to locate quickly DSM's which lower the total Delta(V) on these trajectories.

Navagh, John↗
NASA NTRS2000

Polarimetric Ku-Band Scatterometer for High Accuracy, Large Swath Global Wind Vector Measurements

In the past, wind measurements from space using fan-beam antennas, such as Seasat Scatterometer (SASS-1), ERS-1 &2, and NASA scatterometer (NSCAT), required up to six large stick-like antennas and suffered a nadir gap of up to 400 km. In the near future, a spinning pencil-beam scatterometer system is to be used for the SeaWinds scatterometer on QuikSCAT (QSCAT) and on ADEOS-2 (SeaWinds). This scatterometer, though offering wind measurements in the nadir region, still suffers from degraded performance in the nadir and outer swath. The purpose of this paper is to present an advanced polarimetric spinning pencil-beam scatterometer system, which can significantly improve the wind performance across the entire swath. The polarimetric scatterometer simultaneously measures co-polarized backscatter and the polarimetric correlation of co- and cross-polarized radar returns from the ocean surface. The advantage over the conventional scatterometer system is that, while the co-polarization radar returns are even function of the wind direction, the polarimetric correlation is an odd function of wind direction due to the reflection symmetry of the wind roughened surface. Therefore, this polarimetric scatterometer system can provide additional, equivalent measurements at azimuth angle 45degree away from the corresponding co-polarization measurements. The combined co-polarization and correlation measurements enable good wind performance across the whole swath to be obtained. In this paper, we will first present the theoretical formulation of all of the key components required for designing a polarimetric scatterometer. Then, we show that good wind performance can be achieved by a slight improvement in the signal-to-noise ratio of the current QSCAT/SeaWinds design. We then present the predicated wind performance using computer simulation based on a model function for the co-polarized backscatter obtained from actual spaceborne scatterometer data and an estimated model function for the polarimetric correlation based on the asymmetry observed in backscatter data. Finally, we will show that, aside from ocean applications, this polarimetric scatterometer can also be used for ice and land applications.

Tsai, Wu-Yang↗
NASA NTRS2018

Symmetric Equations on the Surface of a Sphere as Used by Model GISS:IB

Standard vector calculus formulas of Cartesian three space are projected onto the surface of a sphere. This produces symmetric equations with three nonindependent horizontal velocity components. Each orthogonal axis has a velocity component that rotates around its axis (eastward velocity rotates around the north–south axis) and a specific angular momentum component that is the product of the velocity component multiplied by the cosine of axis’ latitude. Angular momentum components align with the fixed axes and simplify several formulas, whereas the rotating velocity components are not orthogonal and vary with location. Three symmetric coordinates allow vector resolution and calculus operations continuously over the whole spherical surface, which is not possible with only two coordinates. The symmetric equations are applied to one-layer shallow water models on cubed-sphere and icosahedral grids, the latter being computationally simple and applicable to an ocean domain. Model results are presented for three different initial conditions and five different resolutions.

Icosahedral grid↗
NASA NTRS2002

HI-STAR. Health Improvements Through Space Technologies and Resources: Final Report

The purpose of this document is to describe a global strategy to integrate the use of space technology in the fight against malaria. Given the well-documented relationship between the vector and its environment, and the ability of existing space technologies to monitor environmental factors, malaria is a strong candidate for the application of space technology. The concept of a malaria early warning system has been proposed in the past' and pilot studies have been conducted. The HI-STAR project (Health Improvement through Space Technologies and Resources) seeks to build on this concept and enhance the space elements of the suggested framework. As such, the mission statement for this International Space University design project has been defined as follows: "Our mission is to develop and promote a global strategy to help combat malaria using space technology". A general overview of malaria, aspects of how space technology can be useful, and an outline of the HI-STAR strategy is presented.

Finarelli, Margaret G.↗
NASA NTRS1979

Solving the current element problem over lossy half-space without Sommerfeld integrals

An approach is presented for efficient computation of the vector potentials arising in the problem of a current element radiating over a lossy half-space. The present approach departs from the conventional ones in that it works primarily with the transform domain representations rather than with the Sommerfeld integrals which are the corresponding spatial domain counterparts. The key step in the present method is to approximate the transforms using a suitable approximation which is valid for a wide range of parameters of practical interest. The approximated transforms can be inverted in a closed form for the horizontal component of the vector potentials and can be expressed in a computationally efficient form for the vertical component. Numerical results illustrating the accuracy of the method are presented and some estimates of comparative computational times are also included.

Mittra, R.↗