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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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A damaged porous refractory material coated with a glass coating is repaired by applying hydrolyzed tetraethyl orthosilicate to the damaged area and curing it. A pliable filler comprised of hydrolyzed tetraethyl orthosilicate and powdered refractory substrate is then applied to the area which is then heated.
Adhesion was studied with emphasis on the characterization of surface oxide layers, the analysis of fracture surfaces, and the interaction of matrices and fibers. A number of surface features of the fractured lap shear samples were noted in the SEM photomicrographs including the beta phase alloy of the Ti 6-4 adherend, the imprint of the adherend on the adhesive failure surface, increased void density for high temperature samples, and the alumina filler particles. Interfacial failure of some of the fractured lap shear samples is invariably characterized by the appearance of an ESCA oxygen photopeak at 530.3 eV assigned to the surface oxide layer of Ti 6-4 adherend. The effect of grit blasting on carbon fiber composites is evident in the SEM analysis. A high surface fluorine concentration on the composite surface is reduced some ten fold by grit blasting.
The selection of structural alloys, composite materials, solder alloys, and filler materials for use in cryogenic models is discussed. In particular, materials testing programs conducted at Langley are described.
Analytical methods used to investigate entry gap heating in the Shuttle orbiter thermal protection system are described. Analytical results are given for a fuselage lower-surface location and a wing lower-surface location. These are locations where excessive gap heating occurred on the first flight of the Shuttle. The results of a study to determine the effectiveness of a half-height ceramic fiber gap filler in preventing hot-gas flow in the tile gaps are also given.
A system for forming hollow spheres containing pressured gas is described which includes a cylinder device containing a molten solid material with a nozzle at its end. A second gas nozzle, lying slightly upstream from the tip of the first nozzle, is connected to a source that applies pressured filler gas that is to fill the hollow spheres. High pressure is applied to the molten metal, as by moving a piston within the cylinder device, to force the molten material out of the first nozzle. At the same time, pressured gas fills the center of the extruded hollow liquid pipe that breaks into hollow spheres. The environment outside the nozzles contains gas at a high pressure such as 100 atmospheres. Gas is supplied to the gas nozzle at a slightly higher pressure such as 101 atmospheres. The pressure applied to the molten material is at a still higher pressure such as 110 atmospheres.
Filler composed of resilient, heat-resistant materials. Thermal barrier nestles snugly in gap between two tiles with minimal protrusion beyond faces of surrounding tiles. When removed from gap, barrier springs back to nearly original shape. Developed for filling spaces between tiles on Space Shuttle, also used in furnaces and kilns.
Flame retardant, abrasion resistant elastomeric compositions are disclosed which are comprised of thermoplastic polyurethane polymer and flame retarding amounts of a filler selected from decabromodiphenyloxide and antimony oxide in a 3:1 weight ratio, and decabromodiphenyloxide, antimony oxide, and ammonium polyphosphate in a 3:1:3 weight ratio respectively. Heat sealable coated fabrics employing such elastomeric compositions as coating film are produced by dissolving the elastomeric composition to form a solution, casting the solution onto a release paper and drying it to form an elastomeric film. The film is then bonded to a woven, knitted, or felted fabric.
An analytical model for calculation of ascent steady state tile loading was developed and validated with wind tunnel data. The analytical model is described and results are given. Results are given for loading due to shocks and skin friction. The analysis included calculation of internal flow (porous media flow and channel flow) to obtain pressures and integration of the pressures to obtain forces and moments on an insulation tile. A heat transfer program was modified by using analogies between heat transfer and fluid flow so that it could be used for internal flow calculation. The type of insulation tile considered was undensified reusable surface insulation (RSI) without gap fillers, and the location studied was the lower surface of the orbiter. Force and moment results are reported for parameter variations on surface pressure distribution, gap sizes, insulation permeability, and tile thickness.
A nickel plaque which may be coated with a suitable metal or compound to make an electrode for a fuel cell or battery is fabricated by directing nickel sensitizer, catalyst and plating solutions through a porous plastic substrate in the order named and at prescribed temperatures and flow rates. A boride compound dissolved in the plating solution decreases the electrical resistance of the plaque. Certain substrates may require treatment in an alkali solution to dissolve filler materials thereby increasing porosity to a required 65%.
The various ways in which reductions in wear and/or friction can be achieved by the use of composite materials are reviewed. Reinforced plastics are emphasized and it is shown that fillers and fibers reduce wear via several mechanisms additional to their role of increasing overall mechanical strength, preferential transfer, counter face abrasion, preferential load support, or third-body formation on either the composite or its counterface. Examples are given from recent work on thin layer composites of the type widely used as dry bearings in aircraft flight control mechanisms. Developments in metal based composites and carbon-carbon composites for high energy brakes are discussed. The aspects which could benefit by increased fundamental understanding identified and the types of composites which appear to have greatest potential for further growth are indicated.
Sound attenuation and total pressure drop of parallel duct baffles incorporating certain boattail geometries were measured in the NASA Ames Research Center 7- by 10-Foot Wind Tunnel. The baseline baffles were 1.56 m long and 20 cm thick, on 45-cm center-to-center spacings, and spanned the test section from floor to ceiling. Four different boattails were evaluated: a short, smooth (nonacoustic) boattail; a longer, smooth boattail; and two boattails with perforated surfaces and sound-absorbent filler. Acoustic measurements showed the acoustic boattails improved the sound attenuation of the baffles at approximately half the rate to be expected from constant-thickness sections of the same length; that is, 1.5 dB/n, where n is the ratio of acoustic treatment length to duct passage width between baffles. The aerodynamic total pressure loss was somewhat sensitive to tail geometry. Lengthening the tails to reduce the diffusion half-angle from 11 to 5 degrees reduced the total pressure loss approximately 9%. Perforating the boattails, which increased the surface roughness, did not have a large effect on the total pressure loss. Aerodynamic results are compared with a published empirical method for predicting baffle total pressure drop.
Centrifugal apparatus produces filled spherical shells for wide range of industrial and scientific applications. Rotating container has radially extending nozzle in which centrifugal force draws liquid shell material from container. Liquid shell material fed from outside container and automatically maintained at fixed level. Along axis of nozzle is tube that connects through rotating seal to source of gas or other filler material. Material-flow and rotation rates adjusted to change bubble size.
Since the introduction of silver-filled epoxy adhesives and silver-filled nitrocellulose lacquer as RFI control materials, a number of new materials have been introduced. The resin carriers have been changed in an effort to make the materials more usable or more EPA acceptable and the fillers have been varied in an effort to make the materials less costly. The corrosion-related properties of second-generation materials were assessed, including adhesives, caulks, and greases. Aluminum 2024 was used as the only substrate material. Ten days of salt fog was used as the corrosive environment. If a noble material such as silver, nickel, or carbon is sandwiched with aluminum an increase in dc resistance results given enough time. If this is unsatisfactory electrically it should either not be used or have all corrosive environments excluded.
The problems confronting the designer of models for cryogenic wind tunnel models are discussed with particular reference to the difficulties in obtaining appropriate data on the mechanical and physical properties of candidate materials and their fabrication technologies. The relationship between strength and toughness of alloys is discussed in the context of maximizing both and avoiding the problem of dimensional and microstructural instability. All major classes of materials used in model construction are considered in some detail and in the Appendix selected numerical data is given for the most relevant materials. The stepped-specimen program to investigate stress-induced dimensional changes in alloys is discussed in detail together with interpretation of the initial results. The methods used to bond model components are considered with particular reference to the selection of filler alloys and temperature cycles to avoid microstructural degradation and loss of mechanical properties.
Ceramic coating increases durability and heat resistance of flexible high-temperature insulation. Coating compatible with quartz-fabric insulation allowing it to remain flexible during and after repeated exposures to temperatures of 1,800 degree F (982 degree C). Prevents fabric from becoming brittle while increasing resistance to aerodynamic abrasion and loading. Coating consists of penetrating precoat and topcoat. Major ingredients high-purity colloidal silica binder and ground silica filler, which ensure stability and compatibility with fabric at high temperatures. Both precoat and topcoat cured at room temperature.
Nature, extent, and possible prevention of radiation damage discussed. Report summarizes likely effects of high-energy radiation in outer space on variety of commercially-available dielectric materials used in spacecraft. Effects reported on basis of recent Galileo tests, unpublished tests involving proton or electron irradiation, and published information. In general, organic materials with carbon or inorganic fillers most resistant to radiation.
High-temperature adhesive systems are evaluated for short and long-term stability at temperatures ranging from 232C to 427C. The resins selected for characterization include: NASA Langley developed polyphenylquinoxaline (PPQ), and commercially available polyimides (PI). The primary method of bond testing is single lap shear. The PPQ candidates are evaluated on 6A1-4V titanium adherends with chromic acid anodize and phosphate fluoride etch surface preparations. The remaining adhesives are evaluated on 15-5 PH stainless steel with a sulfuric acid anodize surface preparation. Preliminary data indicate that the PPQ adhesives tested have stability to 3000 hours at 450F with chromic acid anodize surface preparation. Additional studies are continuing to attempt to improve the PPQ's high-performance by formulating adhesive films with a boron filler and utilizing the phosphate fluoride surface preparation on titanium. Evaluation of the polyimide candidates on stainless-steel adherends indicates that the FM-35 (American Cyanamid), PMR-15 (U.S. Polymeric/Ferro), TRW partially fluorinated polyimide and NR 150B2S6X (DuPont) adhesives show sufficient promise to justify additional testing.
The problems confronting the designer of models for cryogenic wind tunnel models are discussed with particular reference to the difficulties in obtaining appropriate data on the mechanical and physical properties of candidate materials and their fabrication technologies. The relationship between strength and toughness of alloys is discussed in the context of maximizing both and avoiding the problem of dimensional and microstructural instability. All major classes of materials used in model construction are considered in some detail and in the Appendix selected numerical data is given for the most relevant materials. The stepped-specimen program to investigate stress-induced dimensional changes in alloys is discussed in detail together with interpretation of the initial results. The methods used to bond model components are considered with particular reference to the selection of filler alloys and temperature cycles to avoid microstructural degradation and loss of mechanical properties.