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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Optimal microgravity vibration isolation - An algebraic introduction

Certain experiments contemplated for space platforms must be isolated from the accelerations of the platforms. An optimal active control is developed for microgravity vibration isolation, using constant state feedback gains (identical to those obtained from the Linear Quadratic Regulator (LQR) approach) along with constant feedforward (preview) gains. The quadratic cost function for this control algorithm effectively weights external accelerations of the platform disturbances by a factor proportional to (1/omega) (exp 4). Low frequency accelerations (less than 50 Hz) are attenuated by greater than two orders of magnitude. The control relies on the absolute position and velocity feedback of the experiment and the absolute position and velocity feedforward of the platform, and generally derives the stability robustness characteristics quaranteed by the LQR approach to optimality. The method as derived is extendable to the case in which only the relative positions and velocities and the absolute accelerations of the experiment and space platform are available.

Hampton, R. D.↗
NASA NTRS1992

A PC-based collapse factor analysis for high pressure cryogenic systems

A collapse factor simulation computer program, suitable for use on personal computers, for supercritical cryogen system pressurization is examined. The available literature is previewed, individual component models are developed, and the overall simulation program logic is examined. Extensive use is made of existing thermodynamic and transport property evaluation packages. Heat transfer is estimated using natural convection correlations, and transient wall heat conduction is considered. Examples of the simulation are demonstrated for two facilities. Partial validation is achieved by comparing the simulation output with data from an existing test facility. Preliminary results indicate that the collapse factors will seldom exceed 1.15 during supercritical operation of high-pressure cryogenic systems. Recommendations for improvements in the component models and the simulation are made.

Hodge, B. K.↗
NASA NTRS1992

Development status of SINDA/FLUINT and SINAPS

SINDA/FLUINT (Systems Improved Numerical Differencing Analyzer/Fluid Integrator, formerly SINDA '85) is a computer code used to analyze thermal/fluid systems that can be represented in lumped parameter form. In addition to conduction and radiation heat transfer, the code is capable of modeling both single- and two-phase flow networks, their associated hardware, and their heat transfer processes. In this paper, recent improvements to SINDA/FLUINT are described, as are those in progress that will be available in the fall of 1992 in Version 2.5. Also, a preview of planned enhancements is provided. This paper also introduces SINAPS (SINDA Application Programming System), a powerful graphical pre- and postprocessor that will also be available in the fall of 1992.

Cullimore, Brent A.↗
NASA NTRS1993

The Magellan volcanic and magmatic feature catalog

A catalog summarizing the location and characteristics of 1663 volcanic and magmatic centers identified in Magellan radar images of the surface of Venus is in final preparation to be submitted as a Geological Society of America Special Paper. The following is a brief summary preview of the contents and methods used in assembling the final data set, the organization of the catalog, and other notes of interest to potential users.

Crumpler, L. S.↗
NASA NTRS1993

Analysis of hyper-spectral AVIRIS image data over a mixed-conifer forest in Maine

An introduction to some of the potential uses of hyperspectral data for ecosystem analysis is presented. The examples given are derived from a digital dataset acquired over a sub-boreal forest in central Maine in 1990 by the NASA-JPL Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) instrument gathers data from 400 to 2500 nm in 224 channels at bandwidths of approximately 10 nm. As a preview to the uses of the hyperspectral data, several products from this dataset were extracted. They range from the traditional false color composite made from simulated Thematic Mapper bands and the well known normalized difference vegetation index to much more exotic products such as fractions of vegetation, soil and shade based on linear spectral mixing models and estimates of the leaf water content at the landscape level derived using spectrum-matching techniques. Our research and that of many others indicates that the hyperspectral datasets carry much important information which is only beginning to be understood. This analysis gives an initial indication of the utility of hyperspectral data. Much work still remains to be done in algorithm development and in understanding the physics behind the complex information signal carried in the hyperspectral datasets. This work must be carried out to provide the fullest science support for high spectral resolution data to be acquired by many of the instruments to be launched as part of the Earth Observing System program in the mid-1990's.

Lawrence, William T.↗
NASA NTRS1992

A distributed clients/distributed servers model for STARCAT

STARCAT, the Space Telescope ARchive and CATalogue user interface has been along for a number of years already. During this time it has been enhanced and augmented in a number of different fields. This time, we would like to dwell on a new capability allowing geographically distributed user interfaces to connect to geographically distributed data servers. This new concept permits users anywhere on the internet running STARCAT on their local hardware to access e.g., whichever of the 3 existing HST archive sites is available, or get information on the CFHT archive through a transparent connection to the CADC in BC or to get the La Silla weather by connecting to the ESO database in Munich during the same session. Similarly PreView (or quick look) images and spectra will also flow directly to the user from wherever it is available. Moving towards an 'X'-based STARCAT is another goal being pursued: a graphic/image server and a help/doc server are currently being added to it. They should further enhance the user independence and access transparency.

Pirenne, B.↗
NASA NTRS1992

IRAF in the nineties

The Interactive Data Reduction and Analysis Facility (IRAF) data reduction and analysis system has been around since 1981. Today it is a mature system with hundreds of applications, and is supported on all the major platforms. Many institutions, projects, and individuals around the US and around the world have developed software for IRAF. Some of these packages are comparable in size to the IRAF core system itself. IRAF is both a data analysis system, and a programming environment. As a data analysis system it can be easily installed by a user at a remote site and immediately used to view and process data. As a programming environment IRAF contains a wealth of high and low level facilities for developing new applications for interactive and automated processing of astronomical or other data. As important as the applications programs and user interfaces are to the scientist using IRAF, the heart of the IRAF system is the programming environment. The programming environment determines to a large extent the types of applications which can be built within IRAF, what they will look like, and how they will interact with one another and with the user. While applications can be easily added to or removed from a software system, the programming environment must remain fairly stable, with carefully planned evolution and growth, over the lifetime of a system. The IRAF programming environment is the framework on which the rest of the IRAF system is built. The IRAF programming environment as it exists in 1992, and the work currently underway to enhance the environment are discussed. The structure of the programming environment as a class hierarchy is discussed, with emphasis on the work being done on the image data structures, graphics and image display interfaces, and user interfaces. The new technologies which we feel IRAF must deal with successfully over the coming years are discussed. Finally, a preview of what IRAF might look like to the user by the end of the decade is presented.

Tody, D.↗
NASA NTRS1993

Micro guidance and control technology overview

This paper gives an overview of micro-guidance and control technologies and in the process previews of the technology/user and systems issues presented in the guidance and control session at the workshop. We first present a discussion of the advantages of using micro-guidance and control components and then detail six micro-guidance and control thrusts that could have a revolutionary impact on space missions and systems. Specific technologies emerging in the micro-guidance and control field will be examined. These technologies fall into two broad categories: micro-attitude determination (inertial and celestial) and micro-actuation, control and sensing. Finally, the scope of the workshop's guidance and control panel are presented.

Kissel, Glen J.↗
NASA NTRS1994

HST archive primer, version 4.1

This version of the HST Archive Primer provides the basic information a user needs to know to access the HST archive via StarView the new user interface to the archive. Using StarView, users can search for observations interest, find calibration reference files, and retrieve data from the archive. Both the terminal version of StarView and the X-windows version feature a name resolver which simplifies searches of the HST archive based on target name. In addition, the X-windows version of StarView allows preview of all public HST data; compressed versions of public images are displayed via SAOIMAGE, while spectra are plotted using the public plotting package, XMGR. Finally, the version of StarView described here features screens designed for observers preparing Cycle 5 HST proposals.

Fruchter, A.↗
NASA NTRS1994

JPL space robotics: Present accomplishments and future thrusts

Complex missions require routine and unscheduled inspection for safe operation. The purpose of research in this task is to facilitate structural inspection of the planned Space Station while mitigating the need for extravehicular activity (EVA), and giving the operator supervisory control over detailed and somewhat mundane, but important tasks. The telerobotic system enables inspection relative to a given reference (e.g., the status of the facility at the time of the last inspection) and alerts the operator to potential anomalies for verification and action. There are two primary objectives of this project: (1) To develop technologies that enable well-integrated NASA ground-to-orbit telerobotics operations, and (2) to develop a prototype common architecture workstation which implements these capabilities for other NASA technology projects and planned NASA flight applications. This task develops and supports three telerobot control modes which are applicable to time delay operation: Preview teleoperation, teleprogramming, and supervised autonomy.

Weisbin, C. R.↗
NASA NTRS1994

Laser Light Scattering, from an Advanced Technology Development Program to Experiments in a Reduced Gravity Environment

Recent advancements in laser light scattering hardware are described. These include intelligent single card correlators; active quench/active reset avalanche photodiodes; laser diodes; and fiber optics which were used by or developed for a NASA advanced technology development program. A space shuttle experiment which will employ aspects of these hardware developments is previewed.

Meyer, William V.↗
NASA NTRS1995

Improved reduced-resolution satellite imagery

The resolution of satellite imagery is often traded-off to satisfy transmission time and bandwidth, memory, and display limitations. Although there are many ways to achieve the same reduction in resolution, algorithms vary in their ability to preserve the visual quality of the original imagery. These issues are investigated in the context of the Landsat browse system, which permits the user to preview a reduced resolution version of a Landsat image. Wavelets-based techniques for resolution reduction are proposed as alternatives to subsampling used in the current system. Experts judged imagery generated by the wavelets-based methods visually superior, confirming initial quantitative results. In particular, compared to subsampling, the wavelets-based techniques were much less likely to obscure roads, transmission lines, and other linear features present in the original image, introduce artifacts and noise, and otherwise reduce the usefulness of the image. The wavelets-based techniques afford multiple levels of resolution reduction and computational speed. This study is applicable to a wide range of reduced resolution applications in satellite imaging systems, including low resolution display, spaceborne browse, emergency image transmission, and real-time video downlinking.

Ellison, James↗
NASA NTRS1994

Quasi-stereoscopic imaging of the solar X-ray corona

The first published three-dimensional images of the solar X-ray corona obtained by means of solar rotational parallax, are presented in stereographic form. Image pairs approximately 12 hours apart during times of stable coronal conditions were selected from the digitized images obtained with the Skylab X-ray Spectrographic Telescope. The image resolution limit is approximately 10 arc sec. Many coronal structures not visible in the separate images are clearly observed when the image pairs are viewed stereoscopically. This method gives a preview of the potential resources for solar research and forecasting of solar-geomagnetic interactions that could be provided by stereoscopic observations of the Sun using a small group of spacecraft. The method is also applicable to other X-ray, ultraviolet, or other wavebands in which the corona has extended, transparent structure.

Batchelor, David↗
NASA NTRS1995

Infrared studies of galaxies from space

The Kuiper Airborne Observatory has been a powerful instrument for the study of nearby galaxies, and SOFIA could probe still further into the local Universe. However, a comprehensive program of extragalactic exploration in the infrared - and in particular a study of galaxies at cosmological redshifts - requires the high sensitivity and complete wavelength coverage which is achievable only with a cryogenic telescope in space. This program was begun by IRAS and will be continued by the upcoming ISO (Infrared Space Observatory), WIRE (Wide field Infrared Explorer) and SIRTF (Space Infrared Telescope Facility) missions. This paper previews a set of extragalactic investigations which could be carried out by these missions.

Werner, Michael W.↗
NASA NTRS1995

Computational Virtual Reality (VR) as a human-computer interface in the operation of telerobotic systems

This presentation focuses on the application of computer graphics or 'virtual reality' (VR) techniques as a human-computer interface tool in the operation of telerobotic systems. VR techniques offer very valuable task realization aids for planning, previewing and predicting robotic actions, operator training, and for visual perception of non-visible events like contact forces in robotic tasks. The utility of computer graphics in telerobotic operation can be significantly enhanced by high-fidelity calibration of virtual reality images to actual TV camera images. This calibration will even permit the creation of artificial (synthetic) views of task scenes for which no TV camera views are available.

Bejczy, Antal K.↗
NASA NTRS1996

Virtual Reality Lab Assistant

Virtual Reality Lab Assistant (VRLA) demonstration model is aligned for engineering and material science experiments to be performed by undergraduate and graduate students in the course as a pre-lab simulation experience. This will help students to get a preview of how to use the lab equipment and run experiments without using the lab hardware/software equipment. The quality of the time available for laboratory experiments can be significantly improved through the use of virtual reality technology.

Saha, Hrishikesh↗
NASA NTRS1995

Electronic Verification at the Kennedy Space Center

This document reviews some current applications of Electronic Verification and the benefits such applications are providing the Kennedy Space Center (KSC). It also previews some new technologies, including statistics regarding performance and possible utilization of the technology.

Johnson, T. W.↗
NASA NTRS1997

Supplemental Control for Aircraft Riding Qualities

The concept of preview control has been applied and proven to be successful in the automotive vehicle. These same concepts are now applied to an aircraft under the assumption that exogenous inputs (wind gust, turbulence, etc. ) can be measured. A supplemental control law for surface deflection is designed to compensate for the loss in performance in the presence of atmospheric disturbances. Fuzzy logic control is employed to handle the nonlinear, time varying characteristics of the disturbance. A methodology to tune the outer loop control parameters is presented.

Williams, Rolanda S.↗