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Results for “SHIELDING”

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 667 records · Page 37

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NASA NTRS1979

Development of an improved toughness hyperpure silica reflective heat shield

High purity three dimensionally woven silica-silica materials were evaluated for use as a tough reflective heat shield for planetary entry probes. A special weave design was selected to minimize light piping effects through the heat shield thickness. Various weave spacings were evaluated for densification efficiency with an 0.7 micron particle size high purity silica. Spectral hemispherical reflectance was measured from 0.2 to 2.5 microns at room temperature. Reflectance increases due to densification and purity of material were measured. Reflectance of 3D hyperpure silica was higher than 3D astroquartz silica for all wavelengths. Mechanical properties were measured in beam flexure and beam shear tests. Results indicated strengths lower than reported for slip cast fused silica. Low strengths were attributed to low densities achieved through vacuum impregnation.

Rusert, E. L.↗

NASA NTRS1981

Advanced radiative cooler with angled shields

Recent demands for spaceborne sensor temperatures below 90 K are exceeding the capabilities of present passive radiative cooler designs. To improve cooling performance, a novel technique was developed to radiatively and conductively isolate the radiating plate from the spacecraft using low-emittance, highly specular angled radiation shields. An experimental test of the new shield concept verified its effectiveness and enabled calibration of a detailed thermal model. Based on the concept test results, performance predictions show that the Advanced Radiator can achieve lower temperatures, deliver more cooling power and be smaller and lighter than the best state-of-the-art coolers.

Bard, S.↗

NASA NTRS1982

Reflective-Shield Radiative Cooler

Tests show radiative cooler consisting of several thin reflective shields with a slight angle between them redirects flow of heat very effectively. Shield can be used for deflecting virtually any level of thermal radiation can be deflected by technique; but it may be useful in construction reflecting baffles in front of ovens or furnaces.

Petrick, W.↗

NASA NTRS1983

Rod-Wall Sound Shield for Wind Tunnels

Test model is shielded from turbulence radiated from wind tunnel walls. Shield overcomes problems caused by leading-edge configuration and leading edge angle of inclination of previous designs. Has successfully maintained a laminar rather than turbulent boundary layer.

Creel, T. R. J.↗

NASA NTRS1982

Analytical study of twin-jet shielding

Progress in the refinement and evaluation of an analytical jet shielding model are summarized. The model consists of a point noise source impinging on a cylinder of heated flow in which the temperature and velocity are uniform across the cross section of the jet. The shielding jet is infinite in extent along the jet axis and the radius of the jet is constant. The analytical model was compared to experimental data for a point noise source impinging on an ambient temperature, subsonic jet and on a subsonic simulated hot jet using helium as the flow medium. Results of these comparisons are discussed.

Gerhold, C. H.↗

NASA NTRS1980

Analytical study of twin-jet shielding development of a 3-dimensional model

The solution for a point source impinging on a cylinder of heated flow is presented. The indefinite integral is solved approximately using a saddle of point method. Comparison of the three-dimensional model to a previously obtained two-dimensional model of twin jet noise indicate the the approximate solution of the integral is valid. The model was analyzed to differentiate among the mechanims of shielding. Zone in which diffraction and transmission dominate are identified. The model was found to compare to experimental shielding results.

Gerhold, C. H.↗

NASA NTRS1982

Magnetic shielding and vacuum test for passive hydrogen masers

Vibration tests on high permeability magnetic shields used in the SAO-NRL Advanced Development Model (ADM) hydrogen maser were made. Magnetic shielding factors were measured before and after vibration. Preliminary results indicate considerable (25%) degradation. Test results on the NRL designed vacuum pumping station for the ADM hydrogen maser are also discussed. This system employs sintered zirconium carbon getter pumps to pump hydrogen plus small ion pumps to pump the inert gases. In situ activation tests and pumping characteristics indicate that the system can meet design specifications.

Gubser, D. U.↗

NASA NTRS1982

A bismuth germanate-shielded mercuric iodide X-ray detector for space applications

The development of HgI2 for solid state X-ray detector applications over the past decade was carried out in connection with the ability of the crystal to operate as a detector at room temperature. In order to achieve the lowest background possible for HgI2 detectors in a space-like environment (balloon and/or satellite altitudes), attention was given to the design of a shielding system which actively vetoes nonaperture events such as gamma rays and charged particles that can mimic signal X-rays by partial deposition of energy in the main detector. The detector system consists of two HgI2 detectors mounted back to back and operated in anticoincidence. The two detectors are placed inside a bismuth germanate scintillating shield along with two hybrid charge-sensitive preamps. Monte Carlo simulations of detector performance are discussed.

Vallerga, J. V.↗

NASA NTRS1982

Hydrogen outgassing considerations for an orbiting aluminum molecular shield

A molecular shield and associated hardware made of pure aluminum is shown to have an outgassing rate sufficiently low so that operations in orbit would undergo less density contributions than that present from the upper atmospheric atomic hydrogen contribution. Measurements of the atomic hydrogen outgassing from baked-out 6061 aluminum cylindrical samples 3 mm thick are demonstrated to be less than 1/100 trillion l/sec per sq cm, comparable to that of austenitic stainless steels. Calculations of the density distribution with a hemispherical molecular shield are presented, and the elimination of porosity in the aluminum shells is recommended by means of vacuum melting.

Outlaw, R. A.↗

NASA NTRS1982

Spallation of the Galileo probe heat shield

The Galileo probe heat shield will encounter severe radiative and convective heating during entry into Jupiter's atmosphere. The shield is made of two different carbon phenolic composites; one is chopped-molded, and the other is tape-wrapped, both of which tend to spall under intense heating conditions. To characterize this phenomenon, an experimental program, using a gasdynamic laser, was initiated. Tests were performed at a variety of radiation intensities, and both the total and spallation mass-loss rates were measured and correlated with intensity. These correlations were then applied to calculated flight heating conditions for two model atmospheres. Entry of a 310-kg probe into the nominal atmosphere would result in a spallation mass loss of 6.3 kg, or 7.4% of the expected thermochemical mass loss. Similarly, entry of that probe into the cool-dense atmosphere would result in 11.9 kg of spallation, or about 10% of the expected thermochemical mass loss.

Lundell, J. H.↗

NASA NTRS1982

Bidirectional reflectance distribution function of the Infrared Astronomical Satellite solar-shield material

The Infrared Astronomical Satellite (IRAS) telescope has an outer shield on it which is used to reduce the amount of thermal radiation that enters the telescope. The shield forms the first part of the baffle structure which reduces the photon incidence on the focal plane. It was, therefore, necessary to model this structure for scattering, and a required input for such modeling is the scattering characteristic of this surface. Attention is given to the measurement of the bidirectional reflectance distribution function (BRDF), the reflected radiance divided by the incident irradiance at 10.6 micrometers, 118 micrometers, and at several angles of incidence. Visual observation of the gold sample shows that there are striations which line up in a single direction. The data were, therefore, taken with the sample oriented in each of two directions.

Hubbs, J. E.↗

NASA NTRS1983

Improved Connector Shell for Cable Shields

Cable connector shell improves electrostatic and electromagnetic shielding by electrically connecting cable braid around entire circumference. Connector cable braid is slipped over ferrule and sleeve is slipped over braid, clamping it tightly to shell. Connector shell completely shields cable conductors.

Prisk, A. L.↗

NASA NTRS1983

Add-On Shielding for Unshielded Wire

Fabrication sequence used to produce compact shields slipped into place from free ends of wires already soldered into connectors at other ends. Single shields are formed into harnesses by connecting grounding jumpers. Technique is especially useful for small diameter wire attached to microminiature connectors.

Koenig, J. C.↗

NASA NTRS1984

Shielded Aluminum Flat-Conductor Cable

Thin wiring harness stores compactly. Flat aluminum conductors glued between layers of polyimide. Aluminum shield surrounds insulated conductors. Outer layer polyimide. Aluminum shield reduces flexibility of cable and cable withstand only limited number of repetitions of sharp bending at same spot.

Farina, S.↗

NASA NTRS1984

Shielding Electric Connectors From Lightning

Metallic shield for plastic-body electric power connectors, with provision for attaching cable shielding, prevents lightning-induced overvoltages from damaging sensitive electronic equipment.

Pierce, W. B.↗

NASA NTRS1982

Sound shield

An improved test section for a supersonic or hypersonic wind tunnel is disclosed wherein the model tested is shielded from the noise normally radiated by the turbulent tunnel wall boundary layer. A vacuum plenum surrounds spaced rod elements making up the test chamber to extract some of the boundary layer as formed along the rod elements during a test to thereby delay the tendency of the rod boundary layers to become turbulent. Novel rod construction involves bending each rod slightly prior to machining the bent area to provide a flat segment on each rod for connection with the flat entrance fairing. Rods and fairing are secured to provide a test chamber incline on the order of 1 deg outward from the noise shield centerline to produce up to 65% reduction of the root mean square (rms) pressure over previously employed wind tunnel test sections at equivalent Reynolds numbers.

Creel, T. R., Jr.↗

NASA NTRS1983

Molecular self-shielding in the outflows from late-type stars

It is proposed that molecules, especially CO and H2, in the circumstellar outflows from late-type stars can be self-shielded from ambient interstellar UV radiation. The theory of self-shielding in spherical, expanding envelopes is developed for the case in which the photodestruction is dominated by absorption in the Doppler cores of the relevant UV lines, and it is shown that this theory can account for the observations of IRC plus 10216. Also considered is the case in which photodestruction takes place in the damping wings of the UV lines as is appropriate for H2. It is found that most of the hydrogen remains molecular, although the amount of atomic hydrogen is not completely negligible.

Morris, M.↗

NASA NTRS1983

Lead isotope systematics of some igneous rocks from the Egyptian Shield

Lead isotope data on whole-rock samples and two feldspar separates for a variety of Pan-African (late Precambrian) igneous rocks for the Egyptian Shield are presented. It is pointed out that the eastern desert of Egypt is a Late Precambrian shield characterized by the widespread occurrence of granitic plutons. The lead isotope ratios may be used to delineate boundaries between Late Precambrian oceanic and continental environments in northeastern Africa. The samples belong to three groups. These groups are related to a younger plutonic sequence of granites and adamellites, a plutonic group consisting of older tonalites to granodiorites, and the Dokhan volcanic suite.

Gillespie, J. G.↗