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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 541 records · Page 30

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NASA NTRS1976

Report of the Joint Scientific Mission Definition Team for an infrared astronomical satellite

The joint effort is reported of scientists and engineers from the Netherlands, the United Kingdom, and the United States working as a team for the purpose of exploring the possibility of a cooperative venture. The proposed mission builds upon experience gained from the successful Astronomical Netherlands Satellite (ANS). This satellite will be in a polar orbit at an altitude of 900 km. It will carry an 0.6 m diameter telescope cooled with helium to a temperature near 10K. An array of approximately 100 detectors will be used to measure the infrared flux in four wavelength bands centered at 10, 20, 50, and 100 microns. Sources will be located on the sky with positional accuracy of 1/2 arcminute. The instrument should be able to investigate the structure of extended sources with angular scales up to 1.0 deg. The entire sky will be surveyed and the full lifetime of the mission of about one year will be necessary to complete the survey. Special observational programs will also be incorporated into the mission.

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NASA NTRS1978

Switchboard in the sky

Geostationary parking orbits for the present generation of communications satellites, e.g., Intelsat, Westar, Molniya, Navsat, etc., are becoming crowded. It is noted that the C-band over North America will in future be subject to still less attenuation with the introduction of smaller (4.5 m) antennas for earth-bound receive-only applications. It is suggested, at least for the present, that more bands be added, e.g., K-, Ku-, and S-bands. To handle the potential market for communications satellite services during the years after 1985, much larger facilities will be needed. The fabrication of large platforms using the STS is discussed as the most practical solution, stressing that virtually every geosynchronous communications antenna for U.S. domestic use can be assembled on one platform positioned at an especially favorable location.

Fordyce, S. W.↗

NASA NTRS1978

NGC 2110 - An X-ray/radio galaxy with elliptical morphology

The detection of X-ray emission from NGC 2110, a narrow-emission-line galaxy of apparently elliptical morphology, is reported. A relatively hard 2-11-keV energy spectrum with an index of 0.1 + or - 0.3 is obtained, and the X-ray luminosity in this energy band is shown to be 1.2 x 10 to the 43rd erg/s for the redshift distance of 43 Mpc. Optical and radio observations are discussed which indicate a galactocentric redshift of approximately 0.0071, a resolved nonstellar optical nucleus about 4 arcsec in extent, Seyfert type 2 emission lines from the nucleus, and a nonthermal radio source located 3.0 arcsec from the position of the optical nucleus. No evidence is found for X-ray source variability in NGC 2110. It is suggested that the four to seven known X-ray-emitting high-excitation narrow-emission-line galaxies appear to be nearby examples of the Seyfert type 2 phenomenon and that the elliptical morphology of NGC 2110, if confirmed, may be unique among known Seyfert galaxies.

Bradt, H. V.↗

NASA NTRS1979

A method of mapping compact structure in radio sources using VLBI observations

A two-part technique is described for determining the angular structure of the compact components of radio sources from VLBI observations. With this technique, the source structure is first approximated, using both amplitudes and closure phases, by a model consisting of circularly symmetric Gaussian components located on a grid of positions on the sky. The second part begins by employing this model to predict the visibility phase corresponding to each observed visibility amplitude; these estimated visibility phases are then adjusted to agree with the observed closure phases. The resulting estimates of the visibility phases and the observed visibility amplitudes are then combined in a direct Fourier transform to produce a 'dirty' source map that is deconvolved via the CLEAN procedure on the basis of the point-source response. Some examples based on data generated from test models are provided.

Cotton, W. D.↗

NASA NTRS1979

Shuttle orbiter radar cross-sectional analysis

Theoretical and model simulation studies on signal to noise levels and shuttle radar cross section are described. Pre-mission system calibrations, system configuration, and postmission system calibration of the tracking radars are described. Conversion of target range, azimuth, and elevation into radar centered east north vertical position coordinates are evaluated. The location of the impinging rf energy with respect to the target vehicles body axis triad is calculated. Cross section correlation between the two radars is presented.

Cooper, D. W.↗

NASA NTRS1979

Study of a stereo electro-optical tracker system for the measurement of model deformations at the national transonic facility

An electro-optical method to measure the aeroelastic deformations of wind tunnel models is examined. The multitarget tracking performance of one of the two electronic cameras comprising the stereo pair is modeled and measured. The properties of the targets at the model, the camera optics, target illumination, number of targets, acquisition time, target velocities, and tracker performance are considered. The electronic camera system is shown to be capable of locating, measuring, and following the positions of 5 to 50 targets attached to the model at measuring rates up to 5000 targets per second.

Hertel, R. J.↗

NASA NTRS1979

Altitude response of several airplanes during landing approach

The response in altitude and pitching velocity of the shuttle and of four other airplanes during the landing approach is compared. The effects of airplane type, pitch damping, center-of-gravity location, lift coefficient, and cockpit position are presented. The reasons for the differences observed and the effects of these differences on control characteristics are discussed.

Phillips, W. H.↗

NASA NTRS1983

NASA News

The launch of NOAA E, an advanced TIROS N (ATN) environmental monitoring satellite, carrying special search and rescue instrumentation is announced. NOAA E carries instrumentation for a demonstration to search and rescue (SAR) mission agencies for evaluation of a satellite aided SAR system that may lead to the establishment of an operational capability. The ability of a spaceborne system to acquire, track and locate existing Emergency Locator Transmitters (ELTs) and Emergency Position Indicating Radio Beacons (EPIRBs) that are being used aboard general aviation and other aircraft, and ships, and are operating on 121.5 and 243 Megahertz frequencies is demonstrated.

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NASA NTRS1984

A manned-machine space station construction concept

A design concept for the construction of a permanent manned space station is developed and discussed. The main considerations examined in developing the design concept are: (1) the support structure of the station be stiff enough to preclude the need for an elaborate on-orbit system to control structural response, (2) the station support structure and solar power system be compatible with existing technology, and (3) the station be capable of growing in a systematic modular fashion. The concept is developed around the assembly of truss platforms by pressure-suited astronauts operating in extravehicular activity (EVA), assisted by a machine (Assembly and Transport Vehicle, ATV) to position the astronauts at joint locations where they latch truss members in place. The ATV is a mobile platform that is attached to and moves on the station support structure using pegs attached to each truss joint. The operation of the ATV is described and a number of conceptual configurations for potential space stations are developed.

Mikulas, M. M., Jr.↗

NASA NTRS1984

Construction concept for erecting an offset-fed antenna

A design concept for the construction of an offset-fed antenna is discussed. Antennas of this type are of interest for space applications because the configuration eliminates the effects of feed and feed-support blockage. The proposed construction concept is developed around the assembly of a stiff truss substructure by pressure-suited astronauts operating in extravehicular activity (EVA) assisted by a mobile platform that moves along the structure to position the astronauts at joint locations where they can latch members in place. Construction can be accomplished from the shuttle cargo bay in the course of a normal flight or from a space station platform. The concepts demonstrates the versatility of machine assisted manned assembly and is only one of many potential applications.

Rhodes, M. D.↗

NASA NTRS1983

Measurement of heavy cosmic rays above 20 GeV/n in passive detectors - Preliminary results from JACEE-3

It is pointed out that the JACEE-3 experiment combined electronic counters and an emulsion chamber to study nucleus-nucleus interactions between 20 and 100 GeV/n. In the present paper, a description is given of the use of the passive detector stack. The electronic position detectors facilitate the event location, taking into account a determination of the incident angles. CR-39 plastic plates were placed just below the proportional counters to enhance tracking accuracy. The JACEE-3 emulsion chamber consists of three parts, including the charge module, the target module, and the calorimeter module. The charge module is mainly used in track identification. The obtained results are also discussed, giving attention to event number and tracking efficiency, interaction measurements, and the inelasticity distribution.

Burnett, T. H.↗

NASA NTRS1985

Pitch change thresholds as influenced by angular rate and duration of the apparent horizon's displacement

The displacement threshold (DT) during voluntary visual tracking of a line and during fixation of a stable spot located at the initial stimulus position was determined to help in the modeling pilot manual dynamics during the nose-up 'flare' maneuver. Forty-six observers made paired comparison, forced choice judgments of the maximal downward displacements of a horizontal line moving at various speeds for the durations of 0.25, 0.50, and 1.00 sec. The results indicated that the DT is significantly lower, the confidence is higher, and the number of errors and guesses is smaller when a fixation dot is present; moreover, increasing both the stimulus velocity and duration significantly improves the accuracy of displacement discrimination and increases mean confidence.

Haines, R. F.↗

NASA NTRS1987

Evaluation of a takeoff performance monitoring system

A takeoff performance monitoring system (TOPMS) has been developed to provide the pilot with graphic/numeric information pertinent to his decision to continue or abort a takeoff. The TOPMS instrument display consists primarily of a runway graphic overlaid with symbolic status, predictive, and advisory information including: (1) current position and airspeed, (2) predicted locations for reaching decision speed and rotation speed, (3) groundroll limit for reaching the rotation speed, (4) predicted stop point for an aborted takeoff from current conditions, (5) engine-failure flags, and (6) an overall situation advisory flag which recommends continuation or rejection of the takeoff. In this study, over 30 experienced multiengine pilots evaluated the TOPMS display on the Langley B-737 real-time research simulator. The display was judged to be easy to monitor and comprehend.

Middleton, David B.↗

NASA NTRS1988

Reducing Errors In Processing GPS Measurements

Paper presents analyses of techniques for minimization of errors in estimates based on Global Positioning System measurements at multiple locations. Presents fully-redundant double-differencing algorithm for generation of weighted, double-differenced regression system that yields minimum-variance estimates. Addresses two complications arisen in previous double-differencing approaches, namely: Rank-deficient double differencing, and nondiagonal covariance matrix.

Melbourne, W. G.↗

NASA NTRS1989

On principles, methods and recent advances in studies towards a GPS-based control system for geodesy and geodynamics

Although Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) are becoming increasingly important tools for geodynamic studies, their future role may well be fulfilled by using alternative techniques such as those utilizing the signals from the Global Positioning System (GPS). GPS, without the full implementation of the system, already offers a favorable combination of cost and accuracy and has consistently demonstrated the capability to provide high precision densification control in the regional and local areas of the VLBI and SLR networks. This report reviews VLBI and SLR vis-a-vis GPS and outlines the capabilities and limitations of each technique and how their complementary application can be of benefit to geodetic and geodynamic operations. It demonstrates, albeit with a limited data set, that dual-frequency GPS observations and interferometric type analysis techniques make possible the modelling of the GPS orbits for several days with an accuracy of a few meters. The use of VLBI or SLR sites as fiducial stations together with refinements in the orbit determination procedures can greatly reduce the systematic errors in the GPS satellite orbits used to compute the positions of non-fiducial locations. In general, repeatability and comparison with VLBI of the GPS determined locations are of the order of between 2 parts in 10 to the 7th power and 5 parts in 10 to the 8th power for baseline lengths less than 2000 km. This report is mainly a synthesis of problems, assumptions, methods and recent advances in the studies towards the establishment of a GPS-based system for geodesy and geodynamics and is one phase in the continuing effort for the development of such a system. To some, including the author, it seems reasonable to expect within the next few years that more evidence will show GPS to be as a powerful and reliable a tool as mobile VLBI and SLR are today, but largely more economical.

Delikaraoglou, Demitris↗

NASA NTRS1989

Simulator evaluation of a display for a Takeoff Performance Monitoring System

A Takeoff Performance Monitoring System (TOPMS) has been developed to provide the pilot with graphic and numeric information pertinent to his decision to continue or abort a takeoff. The TOPMS information display consists primarily of a runway graphic overlaid with symbolic status, situation, and advisory information including: (1) current position and airspeed; (2) predicted locations for reaching decision speed (V sub 1) and rotation speed (V sub R); (3) groundroll limit for reaching (V sub R); (4) predicted stop point for an aborted takeoff from current conditions; (5) engine-status flags; and (6) an overall situation advisory flag that recommends continuation or rejection of the takeoff. In this study, 32 experienced multi-engine pilots evaluated the TOPMS on the Langley B-737 real-time research simulator. They rated the system satisfactory - good and judged it to be suitable for implementation on an aircraft. The TOPMS, the TOPMS simulation, and the results of the simulator evaluation are described here. Appendices contain the pilot's prebriefing package (written explanation of the TOPMS--sent to the pilots prior to their visit), evaluation instructions, debriefing questions, and rating criteria (organized into a flow diagram similar to the Cooper-Harper diagram for evaluation of aircraft handling qualities).

Middleton, David B.↗

NASA NTRS1990

Tests Of A Differential Global Positioning System

Paper describes validation tests of global positioning system (GPS) for low-flying helicopters. Configured as differential GPS, in which components in both aircraft and ground station compute position errors relative to known location using satellite navigational data. Corrections computed from differences between computed and measured ranges to four satellites being tracked by receiver in both aircraft and ground systems. Tests conducted to determine whether equipment and computer programs of system operated correctly and consistently.

Edwards, F. G.↗

NASA NTRS1989

Phase and time-resolved measurements of unsteady heat transfer and pressure in a full-stage rotating turbine

This paper presents detailed phase-resolved heat-flux data obtained on rotor blades and a comparison of simultaneously obtained time-resolved heat-flux and static pressure data obtained on the stationary shroud of a Garrett TFE 731-2 HP full-stage rotating turbine. A shock tube is used to generate a short-duration source of heated and pressurized air and platinum thin-film gages are used to obtain heat-flux measurements. Blade results are presented at several selected blade locations. Shroud surface pressure and heat-flux time histories are presented for comparable locations relative to the blade position.

Dunn, M. G.↗