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At least 1,153 records · Page 64

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NASA NTRS1972

Central Atlantic regional ecological test site: A prototype regional environment information system

The author has identified the following significant results. Prior to the actual testing of data from ERTS-1, the principal scientific results to date are the establishment of a model or design for a regional land use information system based on remote sensor data and a firm establishment of the RB-57 type high altitude aircraft data base as an important tool in land use mapping. Preliminary user evaluations of the resulting land use data have been favorable, and one of the states, Maryland, has adopted the USGS-GAP land use system as a first step towards mapping their entire state. The State is funding an extension (to the west) of the part of Maryland not covered by CARETS (Central Atlantic Regional Ecological Test Site), using the GAP land use classification and mapping procedures.

Alexander, R. H.↗

NASA NTRS1971

Piston manometer as an absolute standard for vacuum-gauge calibration.

Determination of total pressure in a calibration volume by measuring the force on a thin circular disk, of accurately-known area, that is freely suspended in a hole in the container wall, so that the disk is substantially flush with the wall. The disk almost fills the hole, so that there is a narrow annular gap. A continuous flow of calibrating gas, injected into the container in order to maintain a desired pressure, passes through the annular gap to a diffusion pump. The ratio of pressures on the two faces of the disk is on the order of 100:1, so that downstream pressure need be known only nominally in order to deduce the upstream pressure. Force on the disk is measured by a balance that is calibrated in situ with dead weights. In one arrangement, pressures in the range from 10 to 500 microtorr were measured with an estimated probable error of (1 microtorr + 1%).

Warshawsky, I.↗

NASA NTRS1972

Piston manometer as an absolute standard for vacuum-gauge calibration.

Determination of the total pressure in a calibration volume by measuring the force on a thin circular disk, of accurately known area, that is freely suspended in a hole in the container wall, so that the disk is substantially flush with the wall. The disk almost fills the hole, so that there is a narrow annular gap. A continuous flow of calibrating gas, injected into the container in order to maintain a desired pressure, passes through the annular gap to a diffusion pump. The ratio of pressures on the two faces of the disk is of the order of 100:1, so that downstream pressure need be known only nominally in order to deduce the upstream surface. Force on the disk is measured by a balance that is calibrated in situ with dead weights. In one arrangement, pressures in the range from 10 to 500 microtorr were measured with an estimated probable error of (1 microtorr + 1%).

Warshawsky, I.↗

NASA NTRS1972

Far UV camera/spectrograph

In March 1610, Galileo Galilei reported the first use of a telescope to view mountains and maria on the Moon. On April 21, 1972, the Apollo 16 commander pointed a somewhat more complex optical instrument at the Earth from the Moon and obtained several remarkable photographs showing atmospheric rather than surface features. The optical part of the far UV camera (aperture, 7.5 cm) was not much larger than Galileo's telescope. Like his, this instrument was also pointed at other celestial objects that Galileo viewed, including the Milky Way and Jupiter, and the Large Magellanic Cloud (LMC), which is not visible from Italy. More important, the far UV camera/spectrograph recorded light in the invisible band of wavelengths between 50 and 160 nm, approximately one-third the wavelength that can penetrate the atmosphere of the Earth to ground-based telescopes. As described in more detail in this section, these UV observations from the Moon allow study of the entire atmosphere of the Earth and the geocorona. The photographs show hydrogen and other gases in the solar wind and interplanetary media, and they provide new data on stars, nebulae, and galaxies much farther away. When used as a spectrograph, the instrument distributes the light it receives according to wavelength, and the resulting spectrum shows bright lines or gaps known to be characteristic of various gases, such as hydrogen (H), helium (He), oxygen (O), nitrogen (N), and neon (Ne). If a gas cloud is hot, the atoms are excited and the spectrum shows bright emission lines; if it is cool, the atoms absorb light, leaving gaps or absorption lines. The far UV camera is blind to ordinary visible light; for that reason, the photographs show very few of the stars mapped by ground-based telescopes. Only the very-high-temperature (blue) stars of spectral classes O, B, and possibly A (temperatures from 50000 ° down to 10000°K) are expected to be recorded. Image blackness or density on the negatives also depends on the brightness of the star, which astronomers measure in an inverted logarithmic scale of magnitudes. A star of 6 magnitudes (mag.) can barely be seen with the unaided eye. An 11-mag. star is 100 times fainter, and a 12-mag. star is 2.5 times fainter yet. The faintest star recorded by the far UV camera is at least 11 mag., which is called the limiting magnitude.

George R. Carruthers↗

NASA NTRS1973

Magnetic materials selection for static inverter and converter transformers

A program to study magnetic materials is described for use in spacecraft transformers used in static inverters, converters, and transformer-rectifier supplies. Different magnetic alloys best suited for high-frequency and high-efficiency applications were comparatively investigated together with an investigation of each alloy's inherent characteristics. The materials evaluated were the magnetic alloys: (1) 50% Ni, 50% Fe; (2) 79% Ni, 17% Fe, 4% Mo; (3) 48% Ni, 52% Fe; (4) 78% Ni, 17% Fe, 5% Mo; and (5) 3% Si, 97% Fe. Investigations led to the design of a transformer with a very low residual flux. Tests were performed to determine the dc and ac magnetic properties at 2400 Hz using square-wave excitation. These tests were performed on uncut cores, which were then cut for comparison of the gapped and ungapped magnetic properties. When the data of many transformers in many configurations were compiled the optimum transformer was found to be that with the lowest residual flux and a small amount of air gap in the magnetic material. The data obtained from these tests are described, and the potential uses for the materials are discussed.

Mclyman, W. T.↗

NASA NTRS1973

A modified Monte Carlo model for the ionospheric heating rates.

A Monte Carlo method is adopted as a basis for the derivation of the photoelectron-heat input into the ionospheric plasma. Since a great number of Monte Carlo runs are required normally for the computation of the heating rates, this approach is modified in an attempt to minimize the computation time. The heat-input distributions are computed for arbitrarily small source elements that are spaced apart at distances corresponding to the photoelectron dissipation range. By means of a nonlinear interpolation procedure their individual heating-rate distributions are utilized to produce synthetic ones that fill the gaps between the Monte Carlo generated distributions. By varying these gaps and the corresponding number of Monte Carlo runs the accuracy of the results is tested to verify the validity of this procedure. It is concluded that this model can reduce the computation time by as much as an order of magnitude, thus improving the feasibility of including Monte Carlo calculations in self-consistent ionosphere models.

Mayr, H. G.↗

NASA NTRS1973

A visual study of radial inward choked flow of liquid nitrogen.

Data and high speed movies were acquired on pressurized subcooled liquid nitrogen flowing radially inward through a 0.0076 cm gap. The stagnation pressure ranged from 0.7 to 4 MN/sq m. Steady radial inward choked flow appears equivalent to steady choked flow through axisymmetric nozzles. Transient choked flows through the radial gap are not uniform and the discharge pattern appears as nonuniform impinging jets. The critical mass flow rate data for the transient case appear different from those for the steady case. On the mass flow rate vs pressure map, the slope and separation of the isotherms appear to be less for transient than for steady radial choked flow.

Hendricks, R. C.↗

NASA NTRS1973

Asteroidal source of meteorites.

An effective mechanism for the placement of asteroidal fragments into earth-crossing orbits is discussed. It is pointed out that an asteroid in an orbit with a semimajor axis of about 3.27 AU, corresponding to the most apparent Kirkwood Gap, has a period almost exactly half that of Jupiter and will experience strong resonant perturbations by Jupiter. In the proposed mechanism, fragments 10 to 500 m in diameter resulting from collisions between asteroids located just outside the region in which libration due to the perturbations takes place are injected into the Kirkwood Gap.

Zimmerman, P. D.↗

NASA NTRS1974

Efficiency increased in new solar cell: A Concept

Graded band-gap cell should be able to convert solar radiation into electrical energy more efficiently than any solar cell currently available. Thickness of band-gap region should be chosen to maximize both quantity of light absorbed in region and fraction of photogenerated charge carriers collect at junction.

Hutchby, J. A.↗

NASA NTRS1973

Aerodynamic and noise measurements on a quasi-two dimensional augmentor wing model with lobe-type nozzles

An investigation was made of the static, wind-on aerodynamic and static noise characteristics of an augmentor wing having lobe type nozzles. The study was made in the Ames 7-by 10-Foot No. 1 Wind Tunnel using a small-scale, quasi-two-dimensional model. Several configurations of lobe nozzles as well as a normal slot nozzle were tested. Results indicate that lobe nozzles offer improved static and wind-on aerodynamics and reduced static noise relative to slot nozzles. Best wind-on performance was obtained when the tertiary gap was closed even though the static thrust augmentation was maximum with the gap open. Static thrust augmentation, wind-on lift and drag, and static noise directivity are presented as well as typical static and wind-on exit velocity profiles, surface pressure distributions and noise spectrums. The data are presented with limited discussion.

Aiken, T. N.↗

NASA NTRS1974

Banded transformer cores

A banded transformer core formed by positioning a pair of mated, similar core halves on a supporting pedestal. The core halves are encircled with a strap, selectively applying tension whereby a compressive force is applied to the core edge for reducing the innate air gap. A dc magnetic field is employed in supporting the core halves during initial phases of the banding operation, while an ac magnetic field subsequently is employed for detecting dimension changes occurring in the air gaps as tension is applied to the strap.

Mclyman, C. W. T.↗

NASA NTRS1973

Interchance and cooperation with user agencies

It is apparent that the rate of remote sensing technique development is increasing at a much faster pace than is the rate at which these same techniques are being put to practical use by earth resource managers and inventory specialists. It has become increasingly important to bridge this widening gap between remote sensing specialists and potential users. Members of the University of California project on remote sensing of earth resources have been actively participating in efforts to overcome this gap by maintaining library facilities, disseminating research findings, training remote sensing specialists, and interacting with resource managers.

Lauer, D. T.↗

NASA NTRS1974

Immiscible materials and alloys

Only immiscible materials which involve a fluid phase have a potential advantage when considered for space processing. Processing of such systems at low gravity can lead to a material which is very homogeneous and contains a finely dispersed mixture of phases. Materials with such structures may exhibit potentially useful properties for such applications as superconductors, dispersion-strengthened materials, superplastic materials, permanent magnets, etc. These conclusions have resulted from review of past efforts in the field of low-g processing of materials containing a liquid phase miscibility gap and from present efforts dealing with such systems. These studies have concentrated on precipitation of liquid droplets in a host liquid during cooling through the miscibility gap. This effort has been to study the agglomeration of the droplets both experimentally and through computer simulation in order to understand the mechansism involved and to deduce the effect of gravity on the droplet distribution and resulting structure of the solidified material. The agglomeration mechanisms treated in detail are those due to diffusional growth and collision processes caused by Stokes on convection current-induced droplet migration.

Markworth, A. J.↗

NASA NTRS1974

Stability and control characteristics for the inner mold line configuration of the space shuttle orbiter (OA110)

Experimental aerodynamic investigations were conducted on a sting mounted 0.0405-scale representation of the -140A/B inner mold line (IML) space shuttle orbiter in 7.75 x 11 foot low speed wind tunnel, during the time period from 18 March 1974 to 20 March 1974. The primary test objectives were to establish basic longitudinal and lateral-directional stability and control characteristics for the IML orbiter. Additional configurations investigated were sealed elevon hingeline gaps, sealed rudder split line and hingeline gaps, larger radius leading edge on the vertical tail, and sealed speedbrake base. Aerodynamic force and moment data for the orbiter were measured in the body-axis system by an internally mounted, six-component strain gage balance. The model was sting mounted with the center of rotation located at approximately the wing trailing edge. The nominal angle of attack range was from -4 to +30 degrees. Yaw polars were recorded over a nominal yaw angle range from -14 to +14 degrees at constant angles of attack of 0, + or - 5, 10, 15 and 20 degrees.

Hughes, T.↗

NASA NTRS1974

Investigation of space shuttle orbiter subsonic stability and control characteristics and determination of control surface hinge moments in the Rockwell International low speed wind tunnel (OA37)

Experimental aerodynamic investigations were conducted on a string-mounted 0.030 scale representation of the 140A/B space shuttle orbiter in the 7.75- by 11-foot low speed wind tunnel. The primary test objectives were to establish basic longitudinal and lateral directional stability and control characteristics for the basic configuration plus control surface hinge moments. Aerodynamic force and moment data were measured in the body axis system by an internally mounted, six-component strain gage balance. Additional configurations investigated were sealed rudder hingeline gaps, sealed elevon gaps and compartmentized speedbrakes.

Hughes, T.↗

NASA NTRS1973

Research study on materials processing in space experiment number M512

Adhesion of the melted metals to the adjacent solid metals, and cohesion of the liquid metal to itself appeared to be equally as strong in zero gravity as on earth. Similar cut edge bead periodicity in cut thin plate, and similar periodic chevron patterns in full penetration welds were seen. The most significant practical result is that the design of braze joints for near zero gravity can be very tolerant of dimensional gaps in the joint. This conclusion is based on a comparison of narrow, wide and variable gap widths. Brazing is very practical as a joining or repairing technique for metal structures at zero gravity. The operation of the hardware developed to locate successive small (0.6 cm) diameter cylinders in the focus of the battery powered EB unit, melt the various metal specimens and deploy some liquid metal drops to drift in space, was generally successful. However, the sphericity and surface roughness were far from those of ball bearings.

Tobin, J. M.↗

NASA NTRS1975

Phase change paint tests to investigate effects of TPS tiles on heating rates of the Rockwell space shuttle orbiter (test OH4C, model 21-0)

Information and data from wind tunnel tests conducted on 0.0175-scale models of the space shuttle orbiter are presented. The primary objective of the tests was to evaluate aerodynamic heating effects of the tiles in the thermal protection system (TPS). Tile gap depth and flow orientation effects on the TPS were investigated. Tile patterns were cut into the undersides of the orbiter models to simulate the gaps. One model was left smooth for comparison.

Quan, M.↗

NASA NTRS1975

Results of an investigation elevon hinge moments and dual panel elevon effectiveness using an .0405-scale model (16-0) of the configuration 140C space shuttle orbiter in the Rockwell International NAAL low speed wind tunnel (OA119B)

Experimental aerodynamic investigations were conducted on a sting mounted .0405-scale representation of the 140C outer mold line space shuttle orbiter in a 7.75 x 11.00 foot low speed wind tunnel during the time period from August 22, 1974 to September 6, 1974. The primary test objectives were to define dual panel elevon/aileron effectiveness and to investigate elevon hinge-moments for the 140C orbiter configuration with wing/elevon upper hingeline sealing flapper doors. The elevon parametric variations, consisting of the basic elevons with 6 inch gaps and flapper doors, elevons with no flapper doors and completely open upper hingeline gap, and an entirely sealed solid elevon, were tested with elevon deflections from +20 to -35 deg at various aileron deflections. Aerodynamic force and moment data were measured in the body axis system by a 2.5 inch task type internal strain gage balance.

Mennell, R. C.↗