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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

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NASA NTRS1988

An estimate of the noise shielding on the fuselage resulting from installing a short duct around an advanced propeller

A simple barrier shielding model was used to estimate the amount of noise shielding on the fuselage that could result from installing a short duct around a wing-mounted advanced propeller. With the propeller located one-third of the duct length from the inlet, estimates for the maximum blade passing tone attenuation varied from 7 dB for a duct 0.25 propeller diameter long to 16.75 dB for a duct 1 diameter long. Attenuations for the higher harmonics would be even larger because of their shorter wavelengths relative to the duct length. These estimates show that the fuselage noise reduction potential of a ducted compared with an unducted propeller is significant. Even more reduction might occur if acoustic attenuation material were installed in the duct.

Dittmar, James H.↗

NASA NTRS1988

Rifts of deeply eroded Hawaiian basaltic shields: A structural analog for large Martian volcanoes

Recently derived morphologic evidence suggests that intrusive events have not only influenced the growth of young shield volcanoes on Mars but also the distribution of volatiles surrounding these volcanoes: in addition to rift zones and flank eruptions on Arsia Mons and Pavonis Mons, melt water channels were identified to the northwest of Hecates Tholus, to the south of Hadriaca Patera, and to the SE of Olympus Mons. Melt water release could be the surface expression of tectonic deformation of the region or, potentially, intrusive events associated with dike emplacement from each of these volcanoes. In this study the structural properties of Hawaiian shield volcanoes were studied where subaerial erosion has removed a sufficient amount of the surface to enable a direct investigation of the internal structure of the volcanoes. The field investigation of dike morphology and magma flow characteristics for several volcanoes in Hawaii is reported. A comprehensive investigation was made of the Koolau dike complex that passes through the summit caldera. A study of two other dissected Hawaiian volcanoes, namely Waianae and East Molokai, was commenced. The goal is not only to understand the emplacement process and magma flow within these terrestrial dikes, but also to explore the possible role that intrusive events may have played in volcano growth and the distribution of melt water release on Mars.

Knight, Michael D.↗

NASA NTRS1987

Effects of velocity profile on boundary-layer shielding

A simple uniform flow boundary-layer model is used to study the effects on the acoustic field at the aircraft fuselage of placing Large Eddy Break Up devices in the boundary layer. The introduction of velocity defects into the boundary layer is shown to enhance boundary-layer shielding. Furthermore, shielding improvements are found to occur by moving the velocity defect further from the wall, by increasing its extent within the boundary layer, and by decreasing the minimum velocity in the defect.

Mcaninch, Gerry L.↗

NASA NTRS1988

Tectonic evolution of the Western Australian Shield

Geological and geochronological studies in the Western Australian Shield were updated. This terrane bears many similarities to the Indian Shield since they were neighboring parts of Gondwanaland. Western Australia consists of two cratons (Pilbara and Yilgarn) and four orogenic belts (Capricorn, Pingarra, Albany-Fraser, and Patterson), as well as some relatively young (1.6 to 0.75 Ga) sedimentary rocks. The two cratonic blocks are both older than about 2.5 Ga, and the orogenic belts range in age from 2.0 to 0.65 Ga.

Myers, John S.↗

NASA NTRS1989

Large solar flare radiation shielding requirements for manned interplanetary missions

Estimates are given for the radiation shielding thicknesses required to protect astronauts on interplanetary missions from the effects of large solar flares, on the basis of the integral proton fluences for several past solar particle events. NASA-Langley's nucleon transport deterministic computer code, BRYNTRN, is used to transport primary protons and secondary protons and neutrons through any number of layers of target material of arbitrary thickness and composition. The results of each flare are presented as estimates of dose equivalents to the skin, eyes, and blood-forming organs behind various thicknesses of aluminum shielding.

Townsend, Lawrence W.↗

NASA NTRS1990

Prototype V-Groove Radiator Heat Shield

Report describes design, fabrication, and testing of heat radiator equipped with multi-V-groove radiator heat shield. Device compact, efficient structure which removes heat from infrared detectors, gamma-ray detectors, and similar instruments aboard Mars Observer spacecraft and radiates heat into outer space. Designed to maintain detector for gamma-ray spectrometer at temperature of 80 K in cold vacuum under heat load of 80 mW. Prototype made of aluminum, though production shields made of aluminized sheets of polyethylene terephthalate.

Petrick, S. Walter↗

NASA NTRS1990

Crash-Resistant Shield

Impact-resistant shield designed to consist of aluminum honeycomb structure sandwiched between inner and outer aluminum skins. Intended to protect radioisotope thermoelectric generator of spacecraft from impact with ground or water after free fall from upper atmosphere. Designed to absorb impact energy by buckling, while inner and outer skins designed to protect against shrapnel, overpressure, and impact loads. Concept of shield applicable to crashproof compartments for ground vehicles and aircraft.

Bixler, Charles H.↗

NASA NTRS1989

Volcanism on Venus: Large shields and major accumulations of small domes

The outer layers of the Venusian lithosphere appear to dissipate heat from the interior through mantle-driven thermal anomalies (hot spots, swells). As a result, Venus exhibits diverse forms of thin-skin tectonism and magmatic transfer to and extrusion from countless numbers of volcanic centers (e.g., shields, paterae, domes) and volcano-tectonic complexes (e.g., coronae, arachnoids). What is known about the distribution and morphologies of major Venusian shields is summarized, and the evidence for possible structural control of major accumulations as long as 5000 km of small volcanic domes is described.

Schaber, Gerald G.↗

NASA NTRS1989

Space radiation shielding analysis and dosimetry for the Space Shuttle program

Active and passive radiation dosimeters have been flown on every Space Shuttle mission to measure the naturally-occurring, background Van Allen and galactic cosmic radiation doses that astronauts and radiation-sensitive experiments and payloads receive. A review of the various models utilized at the NASA/Johnson Space Center, Radiation Analysis and Dosimetry is presented. An analytical shielding model of the Shuttle was developed as an engineering tool to aid in making premission radiation dose calculations and is discussed in detail. The anatomical man models are also discussed. A comparison between the onboard dosimeter measurements for the 24 Shuttle missions to date and the dose calculations using the radiation environment and shielding models is presented.

Atwell, William↗

NASA NTRS1990

Advanced meteoroid and debris shielding concepts

The results of the shielding screening and optimization work conducted at the NASA Johnson Space Center Hypervelocity Impact Research Laboratory (HIRL) are described. The impact tests to investigate and optimize certain aspects of the aluminum mesh double-bumper concept, which was considered the best performer in the screening test, are analyzed. Preliminary results indicate that the aluminum mesh double-bumper concept shows a 30 to 40 percent weight reduction compared to an aluminum Whipple shield in the velocity range study, besides such advantages as an increased resistance to penetration and the fact that the aluminum mesh does not produce damaging secondary ejecta particles. It is suggested that the ballistic protection can be improved even more if an intermediate layer of a high-strength cloth is attached near the rear wall.

Christiansen, Eric L.↗

NASA NTRS1990

Small domes on Venus - Probable analogs of Icelandic lava shields

On the basis of observed shapes and volumetric estimates, small, dome-like features on radar images of Venus are interpreted to be analogs of Icelandic lava-shield volcanoes. Morphometric data for Venusian domes in Aubele and Slyuta as well as measurements of representative dome volumes and areas from Tethus Regio are used to demonstrate that the characteristic aspect ratios and flank slopes of these features are consistent with a subclass of low Icelandic lava-shield volcanoes (LILS).

Garvin, James B.↗

NASA NTRS1990

Prospects for using carbon-carbon composites for EMI shielding

Since pyrolyzed carbon has a higher electrical conductivity than most polymers, carbon-carbon composites would be expected to have higher electromagnetic interference (EMI) shielding ability than polymeric resin composites. A rule of mixtures model of composite conductivity was used to calculate the effect on EMI shielding of substituting a pyrolyzed carbon matrix for a polymeric matrix. It was found that the improvements were small, no more than about 2 percent for the lowest conductivity fibers (ex-rayon) and less than 0.2 percent for the highest conductivity fibers (vapor grown carbon fibers). The structure of the rule of mixtures is such that the matrix conductivity would only be important in those cases where it is much higher than the fiber conductivity, as in metal matrix composites.

Gaier, James R.↗

NASA NTRS1990

High-temperature metal purification using a compact, portable rf heating and levitation system on the wake shield

The potential use of a compact, battery-operated rf levitator and heating system to purify high-temperature melting materials in space is described. The wake shield now being fabricated for the Space Vacuum Epitaxy Center will provide an Ultra-high vacuum (10(exp -14) Torr hydrogen, 10(exp -14) Torr helium, 10(exp -30) Torr oxygen). The use of the wake shield to purify Nb, Ti, W, Ir, and other metals to a purity level not achievable on earth is described.

Hahs, C. A.↗

NASA NTRS1991

Unified aeroacoustics analysis for high speed turboprop aerodynamics and noise. Volume 2: Development of theory for wing shielding

A unified theory for aerodynamics and noise of advanced turboprops is presented. The theory and a computer code developed for evaluation at the shielding benefits that might be expected by an aircraft wing in a wing-mounted propeller installation are presented. Several computed directivity patterns are presented to demonstrate the theory. Recently with the advent of the concept of using the wing of an aircraft for noise shielding, the case of diffraction by a surface in a flow has been given attention. The present analysis is based on the case of diffraction of no flow. By combining a Galilean and a Lorentz transform, the wave equation with a mean flow can be reduced to the ordinary equation. Allowance is also made in the analysis for the case of a swept wing. The same combination of Galilean and Lorentz transforms lead to a problem with no flow but a different sweep. The solution procedures for the cases of leading and trailing edges are basically the same. Two normalizations of the solution are given by the computer program. FORTRAN computer programs are presented with detailed documentation. The output from these programs compares favorably with the results of other investigators.

Amiet, R. K.↗

NASA NTRS1991

Space shuttle holddown post blast shield

The original and subsequent designs of the Solid Rocket Booster/Holddown Post blast shield assemblies and their associated hardware are described. It presents the major problems encountered during their early use in the Space Shuttle Program, during the Return-to-Flight Modification Phase, and during their fabrication and validation testing phases. The actions taken to correct the problems are discussed, along with the various concepts now being considered to increase the useful life of the blast shield.

Larracas, F. B.↗

NASA NTRS1991

A deployable high temperature superconducting coil (DHTSC) - A novel concept for producing magnetic shields against both solar flare and Galactic radiation during manned interplanetary missions

The discovery of materials which are superconducting above 100 K makes possible the use of superconducting coils deployed beyong the hull of an interplanetary spacecraft to produce a magnetic shield capable of giving protection not only against solar flare radiation, but also even against Galactic radiation. Such deployed coils can be of very large size and can thus achieve the great magnetic moments required using only relatively low currents. Deployable high-temperature-superconducting coil magnetic shields appear to offer very substantial reductions in mass and energy compared to other concepts and could readily provide the radiation protection needed for a Mars mission or space colonies.

Cocks, F. Hadley↗

NASA NTRS1990

Grounding, bonding and shielding for safety and signal interference control

Aircraft models and other aerodynamic tests are conducted at the NASA Ames Research Center National Full Scale Aerodynamics Complex (NFAC). The models, tested in NFAC's wind tunnels, are sometimes heavily instrumented and are connected to a data acquisition system. Besides recording data for evaluation, certain critical information must be monitored to be sure the model is within operational limits. The signals for these parameters are for the most part low-level signals that require good instrumentation amplification. These amplifiers need to be grounded and shielded for common mode rejection and noise reduction. The instrumentation also needs to be grounded to prevent electrical shock hazards. The purpose of this paper is to present an understanding of the principles and purpose of grounding, bonding, and shielding.

Forsyth, T. J.↗

NASA NTRS1992

Lightweight Shield Against Space Debris

Report presents concept for lightweight, deployable shield protecting orbiting spacecraft against meteoroids and debris, and functions as barrier to conductive and radiative losses of heat. Shield made in four segments providing 360 degree coverage of cylindrical space-station module.

Redmon, John W., Jr.↗