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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1966

System design and performance of earth/lunar horizon sensor BEC project 3744

An infrared horizon sensor system has been designed which is capable of searching over a wide field for the edges of a planet and, upon locating such edges, stations itself in a position which provides signals which identify the local vertical to the planet. In this fixed attitude it requires no continuous mechanical movement and operates with a minimum utilization of power. The system is thus capable of providing a high degree of accuracy when used for local vertical determination in orbits around the earth, the moon, or other planets. A detailed description of the design and operating features of the horizon scanner is given and the evaluation test data which have been completed are presented.

Schwarz, F. C.↗
NASA NTRS1973

The Hat Creek millimeter-wave interferometer.

A fixed-baseline millimeter-wave interferometer, operating initially at 13.5 mm, has been put into operation at the Hat Creek Observatory as the first step in the development of a two-element aperture synthesis telescope. The first system consists of a 3-m antenna and a 6-m antenna spaced 265 m apart. Large receiver bandwidths may be used at high frequencies, and this system employs an intermediate frequency bandwidth of about 400 MHz. The instrument has been used to derive accurate absolute positions of interstellar water vapor sources, to study Mercury, Venus, and Mars, and to make crude maps of a few complex continuum sources. The synthesis telescope, the next stage, has two 6-m antennas which can be located at various stations on a T-shaped track. The east-west leg is 300 m and the north-south leg is 200 m, permitting full synthesis for sources on the equator and at declinations as low as -30 deg as well as at high declinations.

Hills, R. E.↗
NASA NTRS1974

Recent field test results using OMEGA transmissions for clock synchronization

The results are presented of clock synchronization experiments using OMEGA transmissions from North Dakota on 13.10 kHz and 12.85 kHz. The OMEGA transmissions were monitored during April 1974 from NASA tracking sites located at Madrid, Spain; Canary Island; and Winkfield, England. The sites are located at distances between 6600 kilometers (22,100 microseconds) to 7300 kilometers (24,400 microseconds) from North Dakota. The data shows that cycle identification of the received signals was accomplished. There are, however, discrepancies between the measured and calculated propagation delay values which have not been explained, but seem to increase with distance between the receiver and the transmitter. The data also indicates that three strategically located OMEGA transmitting stations may be adequate to provide worldwide coverage for clock synchronization to within plus or minus two (2) microseconds.

Chi, A. R.↗
NASA NTRS1978

Compressor and fan wake characteristics

A triaxial probe and a rotating conventional probe, mounted on a traverse gear operated by two step motors were used to measure the mean velocities and turbulence quantities across a rotor wake at various radial locations and downstream stations. The data obtained was used in an analytical model developed to study how rotor flow and blade parameters and turbulence properties such as energy, velocity correlations, and length scale affect the rotor wake characteristics and its diffusion properties. The model, includes three dimensional attributes, can be used in predicting the discrete as well as broadband noise generated in a fan rotor, as well as in evaluating the aerodynamic losses, efficiency and optimum spacing between a rotor and stator in turbomachinery.

Reynolds, B.↗
NASA NTRS1978

Nodding feed antenna for communications with satellites in synchronous orbit

The design, fabrication, and performance of a parabolic, ground receiving antenna system with a feed that nods in one axis producing a maximum beam deviation 1.1 deg from boresight is described. The antenna design was: (1)to lower the weight (and the subsequent cost) of the supporting structure and the actuator motors for a tracking antenna by moving just the feed; (2) to use a manual tracking system eliminating the need for expensive electronic controls or computers; (3) to provide for several hours of unattended operation; and (4)to permit operation of the antenna by unskilled personnel. Also described are some physical and orbital phenomenon that effect the operation or design of the antenna. One is the motion of a nearly geostationary satellite due to gravitational forces from the sun, the moon, and other stellar bodies. Others are the rotation of the nodding axis and the feed polarization as a function of the location of the station on the earth. A comparison of per unit cost was made for one unit and a quantity of 100.

Smetana, J.↗
NASA NTRS1981

Nonducted coherent VLF waves and associated triggered emissions observed on the ISEE-1 satellite

A description is given of new observations of nonducted coherent VLF waves from ground-based transmitters and associated VLF emissions in the magnetosphere. The data reported were acquired by the Stanford University VLF Wave Injection Experiment on the ISEE-1 satellite. The experiment has four main components, including a broadband (1-32 kHz) VLF receiver on ISEE-1 connected to a long electric antenna, a broadband (1-20 kHz) controllable VLF transmitter located at Siple Station in the Antarctic, various VLF navigation and communications transmitters, and ground stations in the Antarctic and Canada. The main goal of the experiment is to acquire understanding of interactions between coherent VLF waves and energetic particles in the magnetosphere, in particular the whistler mode instability through which both natural and stimulated VLF emissions are produced.

Bell, T. F.↗
NASA NTRS1982

A history and analysis of hydrogen maser reliability

Hydrogen masers an integral part of the Deep Space Network, provide extremely accurate navigation about the outer planets, as well as precise location of tracking stations. Reliability of equipment over extended periods of time was considered. The Deep Space Network has a number of hydrogen masers deployed and in the test cycle, which enabled an analysis of reliability of several generations and breeds of construction. A history and analysis of hydrogen maser reliability over a three-year period was compiled several types of masers.

Curtright, J. B.↗
NASA NTRS1980

Separation of internal and external fields: A new technique of data screening

A method for eliminating transient variation from MAGSAT data is described. Instead of using the conventional Kp index, the Km index is used for the rejection of nonquiet data. To build the Km index, the surface of the Earth is divided in eight sectors. Each sector is defined by two or three magnetic observatories and its geographic limits. For each three hourly interval the MAGSAT tracks were drawn on a map showing the location of the station (the crosses), the limits of the sector, and the value of the mean K index inside each sector. No figure in a sector means that the activity level in this sector is lower than 5 nt; in a sector covered with number 1, the activity lies between 5 and 20 nt; 2 stands for any level greater than 20 nT.

Lemouel, J. L.↗
NASA NTRS1980

Telemetry Computer System at Wallops Flight Center

This paper describes the Telemetry Computer System in operation at NASA's Wallops Flight Center for real-time or off-line processing, storage, and display of telemetry data from rockets and aircraft. The system accepts one or two PCM data streams and one FM multiplex, converting each type of data into computer format and merging time-of-day information. A data compressor merges the active streams, and removes redundant data if desired. Dual minicomputers process data for display, while storing information on computer tape for further processing. Real-time displays are located at the station, at the rocket launch control center, and in the aircraft control tower. The system is set up and run by standard telemetry software under control of engineers and technicians. Expansion capability is built into the system to take care of possible future requirements.

Bell, H.↗
NASA NTRS1983

An experimental heat-transfer investigation of an advanced winged entry vehicle at Mach 10

Heat-transfer measurements have been made at Mach 10 in air on an instrumented 0.006-scale model of an advanced winged entry vehicle. Data were obtained at 83 thermocouple stations which include locations on the lower and upper surface centerlines, spanwise positions along the lower and upper surfaces of the wing, the lower surface of the body flap, and radial locations on the fuselage. Data were obtained for angles of attack ranging from 0 to 45 deg, sideslip angles of + or - 2 deg, Reynolds numbers of 0.5, 1.0 and 2.0 million per foot, and body-flap deflections of 0, 10, and 20 deg. The data generally indicate increased windward heating and decreased leeside heating with increased angle of attack, significantly increased body-flap heating with deflection angle, and minor variations in heating with sideslip, increasing in magnitude with angle of attack. Windward centerline data are shown to be in fair agreement with results of predictions based on an approximate engineering method.

Wurster, K. E.↗
NASA NTRS1984

An experimental investigation of surface pressure measurements on an advanced winged entry vehicle at Mach 10

Surface pressure measurements have been made at Mach 10 in air on an instrumented 0.006-scale model of an advanced (control configured) winged entry vehicle. The tests were conducted in the Langley Continuous Flow Hypersonic Tunnel. Data were obtained at 83 surface pressure stations, which include locations on the lower and upper surface centerlines, spanwise positions along the lower and upper surfaces of the wing, the lower surface of the body flap, and radial locations on the fuselage. Data were obtained for angles of attack ranging from zero to 40 deg, sideslip angles of -2 deg to +5 deg, Reynolds numbers of 0.5, 1.0, and 2.0 million per foot, and body-flap deflections of zero, 10, and 20 deg. Test conditions and orifice locations were chosen to correspond directly with those for the heat transfer measurements previously reported on the same configuration. Comparison of windward symmetry plane data with predictions based upon an approximate engineering method was found to yield reasonable agreement for angles of attack from 20 to 40 deg. The leeward surface pressure data were observed to be roughly an order of magnitude lower than the corresponding windward data. At low angles of attack, regions of high pressure were noted on the windward wing surface. The result is attributed to vortical action or shock impingement. High pressures were also measured on the deflected body flap, a critical region for this type of vehicle. Reynolds number effects were found to be insignificant.

Wurster, K. E.↗
NASA NTRS1987

Lightweight Monorail Transport System

Report proposes monorail transportation system for zero-gravity environment. System carries materials and parts between locations on space station. Includes tubular rails instead of open channels usually found in overhead conveyor systems. Since resistance to torque of closed tube greater than that of open channel for same amount of material, tubular monorail designed for higher loads or for greater spacing between support points.

Weir, Harold F.↗
NASA NTRS1986

PPM/NAR 8.4-GHz noise temperature statistics for DSN 64-meter antennas, 1982-1984

From August 1982 through November 1984, X-band downlink (8.4-GHz) system noise temperature measurements were made on the DSN 64-m antennas during tracking periods. Statistics of these noise temperature values are needed by the DSN and by spacecraft mission planners to assess antenna, receiving, and telemetry system needs, present performance, and future performance. These measurements were made using the DSN Mark III precision power monitor noise-adding radiometers located at each station. It is found that for DSS 43 and DSS 63, at the 90% cumulative distribution level, equivalent zenith noise temperature values fall between those presented in the earlier (1977) and present (1983) versions of DSN/Flight Project design documents. Noise temperatures measured for DSS 14 (Goldstone) are higher than those given in existing design documents and this disagreement will be investigated as a diagnostic of possible PPM or receiving system performance problems.

Slobin, S. D.↗
NASA NTRS1990

Applications of ISES for the atmospheric sciences

The proposed Information Sciences Experiment System (ISES) will offer the opportunity for real-time access to measurements acquired aboard the Earth Observation System (Eos) satellite. These measurements can then be transmitted to remotely located ground based stations. The application of such measurements to issues related to atmospheric science which was presented to a workshop convened to review possible application of the ISES in earth sciences is summarized. The proposed protocol for Eos instruments requires that measurement results be available in a central data archive within 72 hours of acquiring data. Such a turnaround of raw satellite data to the final product will clearly enhance the timeliness of the results. Compared to the time that results from many current satellite programs, the 72 hour turnaround may be considered real time. Examples are discussed showing how real-time measurements from one or more of the proposed Eos instruments could have been applied to the study of certain issues important to global atmospheric chemistry. Each of the examples discussed is based upon a field mission conducted during the past five years. Each of these examples will emphasize how real-time data could have been used to alter the course of a field experiment, thereby enhancing the scientific output. For the examples, brief overviews of the scientific rationale and objectives, the region of operation, the measurements aboard the aircraft, and finally how one or more of the proposed Eos instruments could have provided data to enhance the productivity of the mission are discussed.

Hoell, James M., Jr.↗
NASA NTRS1953

A low-speed experimental study of the directional characteristics of a sharp-nosed fuselage through a large angle-of-attack range at zero angle of sideslip

Static yawing moments and some instantaneous yawing moments are presented through a range of angle of attack at zero sideslip angle for a plain fuselage model having a sharp conical nose and for the fuselage with several nose modifications, one of which consisted of a ring located at different stations along the nose. Some circumferential pressure measurements at one station on the body at several angles of attack are also presented.

PROTUBERANCES-BODIES↗
NASA NTRS1934

Pressure-Distribution Measurements on the Hull and Fins of a 1/40-Scale Model of the U. S. Airship "Akron."

This report presents the results of measurements of pressure distribution conducted in the propeller-research wind tunnel of the National Advisory Committee for Aeronautics on a 1/40-scale model of the U. S. Airship "Akron" (ZRS-4). The pressures, which were measured simultaneously at nearly 400 orifices located at 26 stations along one side of the hull, were recorded by two photographic multiple manometers placed inside the model. The hull pressures were measured both with and without the tail surfaces and the control car for eight angles of pitch varying from 0 degree to 20 degrees and at air speeds of approximately 70 and 100 miles per hour. The pressures were also measured at approximately 160 orifices on one horizontal fin for the above speeds and pitch angles and for nine elevator angles.

Freeman, Hugh B↗
NASA NTRS1994

On the relation between SMMR 37-GHz polarization difference and the rainfall over Africa and Australia

A major difficulty in interpreting coarse resolution satellite data in terms of land surface characteristics is unavailability of spatially and temporally representative ground observations. Under certain conditions rainfall has been found to provide a proxy measure for surface characteristics, and thus a relation between satellite observations and rainfall might provide an indirect approach for relating satellite data to these characteristics. Relationship between rainfall over Africa and Australia and 7-year average (1979-1985) polarization difference (PD) at 37 GHz from scanning multichannel microwave radiometer (SMMR) on board the Nimbus-7 satellite is studied in this paper. Quantitative methods have been used to screen (accept or reject) PD data considering antenna pattern, geolocation uncertainty, water contamination, surface roughness, and adverse effect of drought on the relation between rainfall and surface characteristics. The rainfall data used in the present analysis are climatologic averages and also 1979-1985 averages, and no screening has been applied to this data. The PD data has been screened considering only the location of rainfall stations, without any regard to rainfall amounts. The present analysis confirms a non-linear relation between rainfall and PD published previously.

Choudhury, Bhaskar J.↗
NASA NTRS1994

Four years of ground-based total ozone measurements by visible spectrometry in Antarctica

Visible spectrometers SAOZ have been developed at Service d'Aeronomie for permanent ground-based ozone monitoring at all latitudes up to the polar circle in winter. Observations are made by looking at the sunlight scattered at zenith in the visible range, twice a day, at sunrise and sunset. Compared to ozone observations in the UV generally in use, visible observations in the small Chappuis bands at twilight have the advantages of being independent of stratospheric temperature, little contaminated by tropospheric ozone and multiple scattering, and of permitting observations even in winter at the polar circle. SAOZ instruments have been installed since 1988 at several stations in the Antarctic and the Arctic. More than four years data at Dumont d'Urville in Terre Adelie (67 deg S) are now available. The station is generally located at the edge of the vortex in spring and therefore the ozone hole is seen there only occasionally. The lowest values (140 DU) were reported in early October 1991. According to these first regular observations throughout the whole winter ozone seems to increase in late autumn and winter. Its decay does not start before the end of August. Although of smaller amplitude than with the previous version five data, the ratio between the groundbased and satellite/TOMS measurements displays a systematic seasonal variation correlated partly to the sun zenith angle of observations from orbit and partly to the temperature of the stratosphere. Since ground-based measurements are always made at 90 deg SZA, the SZA dependence must come from the satellite data interpretation (TOMS observations are between 43 to 88 deg SZA). The temperature dependence could be partly due to variations of ozone absorption cross-sections in the ultraviolet used by the satellite spectrometer, and partly to a systematic seasonal cycle of the air mass factor use in the interpretation of the ground based observations. However, the last contribution appears to be too small to compensate the ozone increase in winter reported by SAOZ, which is then real.

Goutail, F.↗