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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Study of hollow corner retroreflectors for use in a synchronous orbit

The performance of a hollow corner cube retroreflector made up of three mutually perpendicular optically flat mirrors when undergoing the thermal-mechanical strains induced by a spacecraft environment was studied. Of particular interest was a device of 200 square centimeter optical aperture used on a satellite in a synchronous orbit. It was assumed that the reflector always faces the earth. The effects of direct solar irradiance, earthshine, and albedo were considered. The results included the maximum mirror surface temperature during the orbit as well as the worst-case loss of optical performance due to thermally-induced mirror distortions. It was concluded that a device made of three suitably coated flat ULE mirrors, optically contacted to each other and supported mechanically in a nonrigid mount, would be expected to concentrate over 80 percent of the theoretical maximum energy in the central of the far field diffraction pattern. Continued development of the device through a detailed design, fabrication, and test phase was recommended.

Yoder, P. R., Jr.↗
NASA NTRS1982

Measurement accuracies in band-limited extrapolation

The problem of numerical instability associated with extrapolation algorithms is addressed. An attempt is made to estimate the bounds for the acceptable errors and to place a ceiling on the measurement accuracy and computational accuracy needed for the extrapolation. It is shown that in band limited (or visible angle limited) extrapolation the larger effective aperture L' that can be realized from a finite aperture L by over sampling is a function of the accuracy of measurements. It is shown that for sampling in the interval L/b absolute value of xL, b1 the signal must be known within an error e sub N given by e sub N squared approximately = 1/4(2kL') cubed (e/8b L/L')(2kL') where L is the physical aperture, L' is the extrapolated aperture, and k = 2pi lambda.

Kritikos, H. N.↗
NASA NTRS1982

Magnetic field studies by Voyager 2 - Preliminary results at Saturn

Results of Voyager 2 studies of the magnetosphere and planetary magnetic field of Saturn are presented. Magnetometer studies have confirmed the results obtained by Voyager 1, indicating the magnetic field to be that of a centered dipole of moment 0.21 gauss Saturn radii-cubed, tilted approximately 0.8 deg from the rotation axis and a maximum measured field intensity of 1187 nT at latitude 17.3 deg N just before periapsis. Voyager 2 observed multiple bow shock and magnetopause crossings during its inbound and outbound trajectories, which were complementary to those of Voyager 1, including magnetopause crossing at 18.5 Saturn radii on the inbound trajectory, and at 48.4-50.9 Saturn radii outbound indicative of magnetospheric expansion due to changing solar wind conditions. Throughout the outbound passage, the magnetospheric field was observed to be relatively steady and smooth, with no evidence for any azimuthal asymmetry or magnetic anomaly. Results thus are incapable of accounting for the observed periodic modulation of the Saturnian kilometric radio emissions.

Ness, N. F.↗
NASA NTRS1982

On the scaling of crater dimensions. II - Impact processes

Holsapple and Schmidt (1980) previously addressed the problem of the scaling of explosive cratering. Their analysis included results which show under which conditions the scaling can be bounded between quarter-root and cube-root rules. The present investigation is an extension of the earlier analysis and approaches the case of impact cratering. More restrictive bounds are found for impact cratering than for the explosive case. These stronger results come from considering the role of the impactor momentum as an independent variable for impact cratering. Attention is given to impact cratering variables, general scaling rules, the bounds on scaling rules, a generalization to more variables, and previous scaling rules and results.

Holsapple, K. A.↗
NASA NTRS1982

Fatigue and creep-fatigue deformation of several nickel-base superalloys at 650 C

Transmission electron microscopy has been used to study the bulk deformation characteristics of seven nickel-base superalloys tested in fatigue and creep-fatigue at 650 C. The alloys were Waspalloy, HIP Astroloy, H plus F Astroloy, H plus F Rene 95, IN 100, MERL 76, and NASA IIB-7. The amount of bulk deformation observed in all the alloys was low. In tests with inelastic strain amplitudes less than about 0.003, only some grains exhibited yielding and the majority of those had the 110 line near the tensile axis. Deformation occurred on octahedral systems for all of the alloys except MERL 76 which also showed abundant primary cube slip. Creep-fatigue cycling occasionally produced extended faults between partial dislocations, but otherwise deformation was much the same as for fatigue cycling.

Miner, R. V.↗
NASA NTRS1984

Imaging Fluid Flow

Electro-optical system allows simultaneous viewing of schlieren, shadowgraph and interferometric images of volume of fluid under test. In imaging system cube beam splitters replaced by plate-type beam splitters or pellicle beam splitters.

Witherow, W. K.↗
NASA NTRS1984

Microyield Stress in Composite Materials

New interferometric method for measuring microyield stress faster and more accurate than previous strain-gage method. Multiple laser beams reflected from corner-cube reflectors arranged in triangular patterns yielding data sufficient to separate length changes from rigid-body motion and bending.

Mcmahan, L.↗
NASA NTRS1980

The effect of yaw on horizontal axis wind turbine loading and performance

The Mod-0 100 kW experimental wind turbine was tested to determine the effects of yaw on rotor power, blade loads and teeter response. The wind turbine was operated for extended periods at yaw angles up to 49 deg to define average or mean response to yaw. It was determined that the effect of yaw on rotor power can be approximated by the cube of the velocity normal to the rotor disc as long as the yaw angle is less than 30 deg. Blade bending loads were relatively unaffected by yaw, but teeter angle increased with wind speed as the magnitude of the yaw angle exceeded 30 deg indicating a potential for teeter stop impacts at large yaw angles. No other adverse effects due to yaw were noted during the tests.

Glasgow, J. C.↗
NASA NTRS1982

Low concentration ratio solar array for low Earth orbit multi-100 kW application

An ongoing preliminary design effort directed toward a low-concentration-ratio photovoltaic array system based on 1984 technology and capable of delivering multi-hundred kilowatts (300 kW to 1000 kW range) in low earth orbit is described. The array system consists of two or more array modules each capable of delivering between 80 kW to 172 kW using silicon solar cells or gallium arsenide solar cells respectively. The array module deployed area is 1320 square meters and consists of 4356 pryamidal concentrator elements. The module, when stowed in the Space Shuttle's payload bay, has a stowage volume of a cube with 3.24 meters on a side. The concentrator elements are sized for a geometric concentration ratio (GCR) of six with an aperture area of 0.5 meters x 0.5 meters. The structural analysis and design trades leading to the baseline design are discussed. The configuration, as well as optical, thermal and electrical performance analyses that support the design and overall performance estimates for the array are described.

Nalbandian, S. J.↗
NASA NTRS1983

Box truss development and applications

The development and applications of a box truss design for large space antennas are discussed. A kinematic model with a mesh reflector was constructed. A prototype cube is described. Details of fabrication are given.

Coyner, J. V., Jr.↗
NASA NTRS1982

The 15-meter diameter mechanically scanned deployable antenna

A preliminary design with structural model data and thermal-performance estimates of a 15-meter mechanically scanned deployable antenna (MSDA) that could be launched onboard a Shuttle Orbiter to provide radiometric brightness temperature maps of the Earth and oceans in selected bands over a frequency range from 1.4 to 11 GHz is provided. The study objectives were met through the design of a unique, integrated, offset feed mast and reflector design that uses the deployable box-truss structure as a building block. The performance of this system is summarized. The all graphite-epoxy, 4.57-meter prototype cube that was completed in 1981 and is proposed for this reflector and feed mast design is presented.

Coyner, J. V.↗
NASA NTRS1982

Low concentration ratio solar array for low Earth orbit multi-100kW application. Volume 2: Drawings

A preliminary design effort directed toward a low concentration ratio photovoltaic array system based on 1984 technology and capable of delivering multi-hundred kilowatts (300 kW to 100 kW range) in low Earth orbit. The array system consists of two or more array modules each capable of delivering between 113 kW to 175 kW using silicon solar cells or gallium arsenide solar cells, respectively. The array module deployed area is 1320 square meters and consists of 4356 pyramidal concentrator elements. The module, when stowed in the Space Shuttle's payload bay, has a stowage volume of a cube with 3.24 meters on a side. The concentrator elements are sized for a geometric concentration ratio (GCR) of six with an aperture area of 0.5 meters x 0.5 meters. Drawings for the preliminary design configuration and for the test hardware that was fabricated for design evaluation and test are provided.

Nalbandian, S. J.↗
NASA NTRS1983

Low concentration ratio solar array for low Earth orbit multi-100 kW application. Volume 1: Design, analysis and development tests

A preliminary design effort directed toward a low concentration ratio photovoltaic array system capable of delivering multihundred kilowatts (300 kW to 1000 kW range) in low earth orbit is described. The array system consists of two or more array modules each capable of delivering between 113 kW to 175 kW using silicon solar cells or gallium arsenide solar cells, respectively. The array module deployed area is 1320 square meters and consists of 4356 pyramidal concentrator elements. The module, when stowed in the Space Shuttle's payload bay, has a stowage volume of a cube with 3.24 meters on a side. The concentrator elements are sized for a geometric concentration ratio (GCR) of six with an aperture area of .25 sq. m. The structural analysis and design trades leading to the baseline design are discussed. It describes the configuration, as well as optical, thermal and electrical performance analyses that support the design and overall performance estimates for the array are described.

Source record↗
NASA NTRS1981

The application of space technology to geodynamics - An overview

The application of various space technologies to the study of the earth is discussed. The main problems that this technology can study are crustal movement and deformation, and earth structure and rotational dynamics. Laser and VLBI systems are used as fixed observatories and as mobile stations which can move between locations separated by 200 to 500 km. Requirements for more frequency and more densely spaced measurements can be met by the use of geodetic receivers which process signals from the Global Positioning System, and an airborne laser which ranges simultaneously to an array of passive cube corner retroreflectors. A Gravity Field Satellite is expected to survey the earth's field to a resolution of 1000 km and accuracies of one milligal. Data from the Magnetic Field Satellite are being used to develop models of the main field for the 1980 Epoch and maps of crustal anomalies.

Fischetti, T. L.↗
NASA NTRS1981

Microwave remote sensing measurements of oil pollution on the ocean

Microwave and optical remote sensors were flown over fresh and weathered crude oil released from a surface research vessel and also over a slick formed on the sea by frozen oleyl alcohol cubes released from a helicopter. For the crude oil experiments, microwave radiometric measurements at 1.43, 2.65, 22, and 31 GHz are reported, along with the variable incidence angle scattering measurements at 13.9 GHz. For these experiments, unusual depressions in the L-band brightness temperature were observed, possibly related to dispersants applied to the crude oil. Similar depressions, but with much larger values, were observed over the oleyl alcohol monomolecular slicks. Images obtained at 31 and 22 GHz were used to infer oil volume, yielding values which bound the known amounts spilled. Ku band measurements obtained in repeated passes over crude oil slicks are also discussed.

Croswell, W. F.↗
NASA NTRS1983

Upper limits on the isotropic gravitational radiation background from pulsar timing analysis

A pulsar and the earth may be thought of as end masses of a free-mass gravitational wave antenna in which the relative motion of the masses is monitored by observing the Doppler shift of the pulse arrival times. Using timing residuals from PSR 1133 + 16, 1237 + 25, 1604-00, and 2045-16, an upper limit to the spectrum of the isotropic gravitational radiation background has been derived in the frequency band 4 x 10 to the -9th to 10 to the -7th Hz. This limit is found to be S(E) = 10 to the 21st f-cubed ergs/cu cm Hz, where S(E) is the energy density spectrum and f is the frequency in Hz. This would limit the energy density at frequencies below 10 to the -8th Hz to be 0.00014 times the critical density.

Hellings, R. W.↗
NASA NTRS1983

Weight trends for a fully reusable advanced single-stage Shuttle

The rate at which subsystem weights grow with vehicle gross weight is assessed and is shown to be critical to the efficiency of large earth-to-orbit transports. Some subsystems grow as the square of vehicle size, others grow as the cube of vehicle size, and still others remain nearly constant irrespective of vehicle size. The overall trend, however, is a reduction in the inerts as a percentage of gross as the vehicle size is increased. For this reason, the larger the vehicle, the greater the payload weight delivered per pound of vehicle manufactured. Other critical issues addressed include the effects of wing loading and wing size on wing weight, the effect of entry planform loading on thermal protection system weight, the impact of power demand on cooling system and prime power weight, and tank fineness ratio on insulation weight. The effects of body shape and various internal packaging arrangements on weight and balance are also discussed. Of greatest impact on overall vehicle weight is body shape and internal packaging and could account for weight savings of up to 30 percent in body structure. Other subsystems are important but the savings are much smaller in relation to overall vehicle weight - individually less than one percent.

Macconochie, I. O.↗
NASA NTRS1983

DE 102 - A numerically integrated ephemeris of the moon and planets spanning forty-four centuries

It is pointed out that the 1960's were the turning point for the generation of lunar and planetary ephemerides. All previous measurements of the positions of solar system bodies were optical angular measurements. New technological improvements leading to immense changes in observational accuracy are related to developments concerning radar, Viking landers on Mars, and laser ranges to lunar corner cube retroreflectors. Suitable numerical integration techniques and more comprehensive physical models were developed to match the accuracy of the modern data types. The present investigation is concerned with the first integrated ephemeris, DE 102, which covers the entire span of the historical astronomical observations of usable accuracy which are known. The fit is made to modern data. The integration spans the time period from 1411 BC to 3002 AD.

Newhall, X. X.↗