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At least 253 records · Page 14

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NASA NTRS1975

The generation of transition radiation by relativistic particles in plastic foam radiators

The design of large area transition radiation detectors for highly relativistic particles can be greatly simplified if plastic foam radiators are employed. Using electron beams with energies 1-9 GeV at the Cornell synchrotron, we have studied the properties of a large variety of transition radiators consisting of commercially available foam materials. In most cases, a measurable transition radiation signal has been observed, but only a few materials have been found to be suitable for practical purposes. The observed radiation yield is in these cases very similar to that of equivalent multifoil radiators. A detailed discussion is given of the particle detection efficiency that can be obtained with high yield foam radiators.

Prince, T. A.↗

NASA NTRS1977

Viscoelastic foam cushion

Foam is viscous and elastic with unusual and useful temperature, humidity, and compression responses. Applied weight and pressure distributed equally along entire interface with foam eliminates any pressure points. Flexible urethane foam is ideal for orthopedic and prosthetic devices, sports equipment, furniture, and crash protection.

Kubokawa, C. C.↗

NASA NTRS1976

The foaming of lavas

Foaming is of great practical and theoretical significance for volcanic processes on the earth, the moon, and perhaps the meteorite parent bodies. The theory of foams agrees with steelmaking experience to indicate that their presence depends on the existence of solutes in the lavas which reduce the surface tension, and are not saturated. These solutes concentrate at the surface, and are called surfactants. The surfactant responsible for the formation of volcanic ash was not identified; it appears to be related to the oxygen partial pressure above the lava. This fact may explain why lunar and meteoritic melts are not observed to foam. Experimental studies are needed to clarify the process.

Okeefe, J. A.↗

NASA NTRS1978

Fire-retardant foams

Family of polyimide resins are being developed as foams with exceptional fire-retardant properties. Foams are potentially useful for seat cushions in aircraft and ground vehicles and for applications such as home furnishings and building-construction materials. Basic formulations can be modified with reinforcing fibers or fillers to produce celular materials for variety of applications. By selecting reactants, polymer structure can be modified to give foams with properties ranging from high resiliency and flexibility to brittleness and rigidity.

Gagliani, J.↗

NASA NTRS1977

Cryogenic foam insulation: Abstracted publications

A group of documents were chosen and abstracted which contain information on the properties of foam materials and on the use of foams as thermal insulation at cryogenic temperatures. The properties include thermal properties, mechanical properties, and compatibility properties with oxygen and other cryogenic fluids. Uses of foams include applications as thermal insulation for spacecraft propellant tanks, and for liquefied natural gas storage tanks and pipelines.

Williamson, F. R.↗

NASA NTRS1978

Polymeric foams from cross-linkable poly-N-ary lenebenzimidazoles

Foamed cross-linked poly-N-arylenebinzimidazoles are prepared by mixing an organic tetraamine and an ortho substituted aromatic dicarboxylic acid anhydride in the presence of a blowing agent, and then heating the prepolymer to a temperature sufficient to complete polymerization and foaming of the reactants. In another embodiment of the process, the reactants are heated to form a prepolymer. The prepolymer is then cured at higher temperatures to complete foaming and polymerization.

Harrison, E. S.↗

NASA NTRS1979

Ambient curing fire resistant foams

The feasibility of development of an ambient curing foam is described. The thermal stability and flame spread index of the foams were found to be comparable to those of the high-temperature cured polyimide foams by Monsanto two-foot tunnel test and NASA T-3 Fire test. Adaptation of the material to spray in place applications is described

Hamermesh, C. L.↗

NASA NTRS1982

Sea foam reflectance and influence on optimum wavelength for remote sensing of ocean aerosols

According to previous investigations, sea foam is a major variable in the accurate determination of aerosol turbidity over the oceans with remote-sensing systems. As a result, tests have been conducted to measure sea foam reflectance at wavelengths from 0.55 micron to 2.8 microns. Data from the tests offer an improved knowledge of the effects of sea foam on radiation upwelled from the ocean surface at near-infrared wavelengths. Application of the new data suggests potential for a 40 percent improvement in signal to noise characteristics of aerosol measurements over the oceans if a 1.56 micron waveband is used instead of 0.75 micron.

Whitlock, C. H.↗

NASA NTRS1985

Investigation of foam flotation and phase partitioning techniques

The present status of foam flotation as a separation process is evaluated and limitations for cells and proteins are determined. Possible applications of foam flotation to separations in microgravity are discussed. Application of the fluid mechanical aspects of foam separation techniques is made to phase partitioning in order to investigate the viscous drag forces that may effect the partitioning of cells in a two phase poly(ethylene glycol) and dextran system.

Currin, B. L.↗

NASA NTRS1986

Repairing Foam Insulation

Large holes in polyurethane foam insulation repaired reliably by simple method. Little skill needed to apply method, used for overhead repairs as well as for those in other orientations. Plug positioned in hole to be filled and held in place with mounting fixture. Fresh liquid foam injected through plug to bond it in place. As foam cures and expands, it displaces plug outward. Protrusion later removed.

Corbin, J.↗

NASA NTRS1987

Thermosetting Fluoropolymer Foams

New process makes fluoropolymer foams with controllable amounts of inert-gas fillings in foam cells. Thermosetting fluoropolymers do not require foaming additives leaving undesirable residues and do not have to be molded and sintered at temperatures of about 240 to 400 degree C. Consequently, better for use with electronic or other parts sensitive to high temperatures or residues. Uses include coatings, electrical insulation, and structural parts.

Lee, Sheng Yen↗

NASA NTRS1987

Biot theory and acoustical properties of high porosity fibrous materials and plastic foams

Experimental values of acoustic wave propagation constant and characteristic impedance in fibrous materials, and normal absorption for two plastic foams, were compared to theoretical predictions obtained with Biot's theory. The best agreement was observed for fibrous materials between Biot's theory and Delany and Bazley experiments for a nearly zero mass coupling parameter. For foams, the lambda/4 structure resonance effect on absorption was calculated by using four-pole modelling of the medium. A significant mass coupling parameter is then necessary for obtaining agreement between the behavior of the measured absorption coefficients and the theoretical predictions. It is shown how the formalism used for predicting foams absorption coefficients may be used for studying the acoustic behavior of multi-layered media.

Allard, J.↗

NASA NTRS1987

Strengthening of phosphate ceramic foam by silicon carbide whiskers

The influence of additions of SiC whiskers on the elastic modulus and flexural strength of phosphate ceramic foam is assessed. It is shown that the incorporation into the material composition of even small amounts (2.4 vol%) of SiC whiskers enhances the impact toughness and heat resistance of the ceramic foam. A 12.3 vol% of SiC whiskers leads to a more than threefold increase of the flexural strength. Strengthening of the phosphate ceramic foam is due to the fact that the whiskers hinder the propagation of matrix crack by increasing the work of matrix fracture. The whiskers reinforce only that volume of material which is occupied by solid matter, whereas they do not reinforce the pores.

Schetanov, B. V.↗

NASA NTRS1990

Foam formation in low gravity

An apparatus that produced the first polyurethane foam in low gravity has been described. The chemicals were mixed together in an apparatus designed for operation in low gravity. Mixing was by means of stirring the chemicals with an electric motor and propeller in a mixing chamber. The apparatus was flown on Consort 1, the first low-gravity materials payload launched by a commercial rocket launch team. The sounding rocket flight produced over 7 min of low gravity during which a polyurethane spheroidal foam of approximately 2300 cu cm was formed. Photographs of the formation of the foam during the flight show the development of the spheroidal form. This begins as a small sphere and grows to approximately a 17-cm-diam spheroid. The apparatus will be flown again on subsequent low-gravity flights.

Wessling, Francis C.↗

NASA NTRS1992

Bonded ceramic foams reinforced with fibers for high temperature use

High quality SiC ceramic foams, which have only recently become available, have for the first time made possible the construction of low density ceramic fiber-ceramic foam sandwiches for high temperature applications. This report describes the construction of some ceramic fiber-ceramic foam structures and the preliminary measurement of strength at elevated temperature.

Mcdonald, G.↗

NASA NTRS1992

Textural constraints on effusive silicic volcanism - Beyond the permeable foam model

The paper reports textural observations and presents isotopic evidence from active and recent silicic lava flows which show that at least some vesiculation occurs during surface advance of extrusions, after magma has reached the earth's surface. This view is in contrast to the widely promoted 'permeable foam' model, which states that all volatiles escape during ascent of the magma, and that all dense glassy material in lava flows forms from the collapse of pumiceous lava, i.e., that silicic lavas emerge as highly inflated foam flows. The permeable foam model also implies the unlikely requirement that explosive-to-effusive transitions be associated with an increase in the eruption rate. A more comprehensive model for the emplacement of silicic extrusions that allows for early gas loss during ascent, as well as late-stage vesiculation, is presented. The way in which the redistribution of volatiles during surface flow can increase explosive hazards from silicic lavas days, weeks, or months after the lava emerges from the event is discussed.

Fink, Jonathan H.↗

NASA NTRS1993

Plastic Foam Withstands Greater Temperatures And Pressures

Improved plastic foam suitable for use in foam-core laminated composite parts and in tooling for making fiber/matrix-composite parts. Stronger at high temperatures, more thermally and dimensionally stable, machinable, resistant to chemical degradation, and less expensive. Compatible with variety of matrix resins. Made of polyisocyanurate blown with carbon dioxide and has density of 12 to 15 pounds per cubic feet. Does not contibute to depletion of ozone from atmosphere. Improved foam used in cores of composite panels in such diverse products as aircraft, automobiles, railroad cars, boats, and sporting equipment like surfboards, skis, and skateboards. Also used in thermally stable flotation devices in submersible vehicles. Machined into mandrels upon which filaments wound to make shells.

Cranston, John A.↗

NASA NTRS1993

Cryogenic testing of a foam-multilayer insulation concept in a simulated orbit hold environment

Foam multilayer insulation (FMLI), a reusable thermal control system (TCS), was evaluated in a simulated orbit hold environment on a test tank of 3.0 ft diameter, 5.6 ft length, and 34.5 cu ft volume. The TCS consisted of a 0.44-inch thick foam and a 16-layer (17 sheet) MLI blanket attached to the tank barrel and lower bulkhead, with the upper bulkhead covered with a 2.7-inch foam and a 31-layer (32 sheets) MLI blanket. Average insulation heating rates during orbit hold simulations ranged from 10.5 to 28.1 Btu/hr for warm boundary temperatures from 300 to 460 R, respectively. These rates corresponded to liquid losses of 0.9 and 2.3 percent of the tank's volume per day. This liquid loss rate would be significantly reduced for full size vehicle tanks due to the decreased surface area-to-volume ratio as compared to the test tank.

Martin, James J.↗