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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 937 records · Page 52

All sources NASA NTRS DOE OSTI

NASA NTRS1981

Study of methods for applying and enhancing transfer film coatings of polytetrafluoroethylene (PTEE) to Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbo Pump (HPOTP) bearings

Machines were constructed and evaluated for burnishing polytetrafluoroethylene on balls for use in the high pressure oxygen turbopump (HPOTP). The most positive performance was obtained with single-ball burnishing, but one technique for burnishing three balls simultaneously holds promise. Evaluations of the coatings in a HPOTP bearing of earlier design (employed smaller diameter balls) showed very little life enhancement before high torque and ball and race wear initiated. Other coating techniques, such as molybdenum disulfide combined with PTFE transfer films, hold promise for providing the more durable quantities of solid lubricant needed for the bearings.

Kannel, J. W.↗

NASA NTRS1982

Ion beam surface modification

The essential details of a study on the practical applications and mechanisms of polymer sputtering via Argon ion impact are summarized. The potential to modify the properties of polymer surfaces to improve their adherence, durability, biocompatibility, or other desirable properties by ion beam sputtering was emphasized. Ion beam milling can be of benefit as an analytical tool to obtain composition versus depth information. Ion impact from a directed ion gun source specifically etches polymer structures according to their morphologies, therefore this technique may be useful to study unknown or new morphological features. Factors addressed were related to: (1) the texture that arises on a polymer target after ion impact; (2) the chemistry of the top surface after ion impact; (3) the chemistry of sputtered films of polymeric material deposited on substrates placed adjacent to targets during ion impact; and (4) practical properties of textured polymer targets, specifically the wettability and adhesive bonding properties.

Dwight, D. W.↗

NASA NTRS1982

JT9D ceramic outer air seal system refinement program

The abradability and durability characteristics of the plasma sprayed system were improved by refinement and optimization of the plasma spray process and the metal substrate design. The acceptability of the final seal system for engine testing was demonstrated by an extensive rig test program which included thermal shock tolerance, thermal gradient, thermal cycle, erosion, and abradability tests. An interim seal system design was also subjected to 2500 endurance test cycles in a JT9D-7 engine.

Gaffin, W. O.↗

NASA NTRS1981

Tailored plasma sprayed MCrAlY coatings for aircraft gas turbine applications

Eighteen plasma sprayed coating systems, nine based on the NiCoCrAly chemistry and nine based on the CoCrAly composition, were evaluated to identify coating systems which provide equivalent or superior life to that shown by the electron beam physical vapor deposited NiCoCrAly and CoCrAly coatings respectively. NiCoCrAly type coatings were examined on a single crystal alloy and the CoCrAly based coatings were optimized on the B1900+ Hf alloy. Cyclic burner rig oxidation and hot corrosion and tensile ductility tests used to evaluate the various coating candidates. For the single crystal alloy, a low pressure chamber plasma sprayed NiCoCrAly + Si coating exhibited a 2x oxidation life improvement at 1394 K (2050 F) over the vapor deposited NiCoCrAly material while showing equivalent tensile ductility. A silicon modified low pressure chamber plasma sprayed CoCrAly coating was found to be more durable than the baseline vapor deposited CoCrAly coating on the B1900+ Hf alloy.

Pennisi, F. J.↗

NASA NTRS1981

Phosphoric Acid Fuel Cell Technology Status

A review of the current phosphoric acid fuel cell system technology development efforts is presented both for multimegawatt systems for electric utility applications and for multikilowatt systems for on-site integrated energy system applications. Improving fuel cell performance, reducing cost, and increasing durability are the technology drivers at this time. Electrodes, matrices, intercell cooling, bipolar/separator plates, electrolyte management, and fuel selection are discussed.

Simons, S. N.↗

NASA NTRS1982

Recent developments in the NSWC composite electrode

A characterization of the physical parameters and life cycle data on nickel composite electrodes was conducted. Attempts to improve the nickel composite electrodes with respect to longevity, light weight, and low cost were made. The physical characteristics of a group of electrodes were examined with emphasis on the porosity of the plaques, the thickness of the electrodes, and the potential presence of electrolytes contamination. It was concluded that the nickel composite electrodes exhibit good life cycle characteristics and that their fabrication seems to present real possibilities for the future as a method of making electrodes that are durable, lightweight, and low cost.

Ferrando, W. A.↗

NASA NTRS1981

Advanced Low-Emissions Catalytic-Combustor Program, phase 1

Six catalytic combustor concepts were defined, analyzed, and evaluated. Major design considerations included low emissions, performance, safety, durability, installations, operations and development. On the basis of these considerations the two most promising concepts were selected. Refined analysis and preliminary design work was conducted on these two concepts. The selected concepts were required to fit within the combustor chamber dimensions of the reference engine. This is achieved by using a dump diffuser discharging into a plenum chamber between the compressor discharge and the turbine inlet, with the combustors overlaying the prediffuser and the rear of the compressor. To enhance maintainability, the outer combustor case for each concept is designed to translate forward for accessibility to the catalytic reactor, liners and high pressure turbine area. The catalytic reactor is self-contained with air-cooled canning on a resilient mounting. Both selected concepts employed integrated engine-starting approaches to raise the catalytic reactor up to operating conditions. Advanced liner schemes are used to minimize required cooling air. The two selected concepts respectively employ fuel-rich initial thermal reaction followed by rapid quench and subsequent fuel-lean catalytic reaction of carbon monoxide, and, fuel-lean thermal reaction of some fuel in a continuously operating pilot combustor with fuel-lean catalytic reaction of remaining fuel in a radially-staged main combustor.

Sturgess, G. J.↗

NASA NTRS1982

Thin film temperature sensors, phase 3

A thin film thermocouple system installation suitable for engine test evaluation was designed, and an engine test plan was prepared. Film adherence, durability, accuracy, and drift characteristics were improved. Film thickness was increased to 14 microns, and drift was reduced to less than 0.02 percent of Fahrenheit temperature per hour on actual turbine blades at 1255 K.

Grant, H. P.↗

NASA NTRS1982

Experimental research on the Stirling engine

Experiments on Stirling engines of the 50 KW class were conducted to clarify the characteristics of the engine and its problems. The problems involve durability of the high temperature heat exchanger which is exposed to high flame temperatures above 1600 C, thermal distortion and high temperature corrosion of the devices near combustion, and of the preheater.

Ishizaki, Y.↗

NASA NTRS1982

Advanced turbine study

Experiments to determine the available increase in turbine horsepower achieved by increasing turbine inlet temperature over a range of 1800 to 2600 R, while applying current gas turbine airfoil cling technology are discussed. Four cases of rocket turbine operating conditions were investigated. Two of the cases used O2/H2 propellant, one with a fuel flowrate of 160 pps, the other 80 pps. Two cases used O2/CH4 propellant, each having different fuel flowrates, pressure ratios, and inlet pressures. Film cooling was found to be the required scheme for these rocket turbine applications because of the high heat flux environments. Conventional convective or impingement cooling, used in jet engines, is inadequate in a rocket turbine environment because of the resulting high temperature gradients in the airfoil wall, causing high strains and low cyclic life. The hydrogen-rich turbine environment experienced a loss, or no gain, in delivered horsepower as turbine inlet temperature was increased at constant airfoil life. The effects of film cooling with regard to reduced flow available for turbine work, dilution of mainstream gas temperature and cooling reentry losses, offset the relatively low specific work capability of hydrogen when increasing turbine inlet temperature over the 1800 to 2600 R range. However, the methane-rich environment experienced an increase in delivered horsepower as turbine inlet temperature was increased at constant airfoil life. The results of a materials survey and heat transfer and durability analysis are discussed.

Source record↗

NASA NTRS1982

An Assessment of Alternate Thermal Protection Systems for the Space Shuttle Orbiter: Executive Summary - Volume 1

Alternate thermal protection system (TPS) concepts to the Space Shuttle Orbiter were assessed. Metallic, ablator, and carbon-carbon concepts which are the result of some previous design, manufacturing and testing effort were considered. Emphasis was placed on improved TPS durability, which could potentially reduce life cycle costs and improve Orbiter operational characteristics. Integrated concept/orbiter point designs were generated and analyzed on the basis of Shuttle design environments and criteria. A merit function evaluation methodology based on mission impact, life cycle costs, and risk was developed to compare the candidate concepts and to identify the best alternate. Voids and deficiencies in the technology were identified, along with recommended activities to overcome them. Finally, programmatic plans, including ROM costs and schedules, were developed for all activities required to bring the selected alternate system up to operational readiness.

Hays, D.↗

NASA NTRS1982

Evaluation of left ventricular assist device pump bladders cast from ion-sputtered polytetrafluorethylene mandrels

A highly thromboresistant blood contacting interface for use in implanatable blood pump is investigated. Biomaterials mechanics, dynamics, durability, surface morphology, and chemistry are among the critical consideration pertinent to the choice of an appropriate blood pump bladder material. The use of transfer cast biopolymers from ion beam textured surfaces is investigated to detect subtle variations in blood pump surface morphology using Biomer as the biomaterial of choice. The efficacy of ion beam sputtering as an acceptable method of fabricating textured blood interfaces is evaluated. Aortic grafts and left ventricular assist devices were implanted in claves; the blood interfaces were fabricated by transfer casting methods from ion beam textured polytetrafluorethylene mandrels. The mandrels were textured by superimposing a 15 micron screen mesh; ion sputtering conditions were 300 volts beam energy, 40 to 50 mA beam, and a mandrel to source distance of 25 microns.

Source record↗

NASA NTRS1982

Assessment of a 40-kilowatt stirling engine for underground mining applications

An assessment of alternative power souces for underground mining applications was performed. A 40-kW Stirling research engine was tested to evaluate its performance and emission characteristics when operated with helium working gas and diesel fuel. The engine, the test facility, and the test procedures are described. Performance and emission data for the engine operating with helium working gas and diesel fuel are reported and compared with data obtained with hydrogen working gas and unleaded gasoline fuel. Helium diesel test results are compared with the characteristics of current diesel engines and other Stirling engines. External surface temperature data are also presented. Emission and temperature results are compared with the Federal requirements for diesel underground mine engines. The durability potential of Stirling engines is discussed on the basis of the experience gaind during the engine tests.

Cairelli, J. E.↗

NASA NTRS1982

Photovoltaic module encapsulation design and materials selection, volume 1

Encapsulation material system requirements, material selection criteria, and the status and properties of encapsulation materials and processes available are presented. Technical and economic goals established for photovoltaic modules and encapsulation systems and their status are described. Available encapsulation technology and data are presented to facilitate design and material selection for silicon flat plate photovoltaic modules, using the best materials available and processes optimized for specific power applications and geographic sites. The operational and environmental loads that encapsulation system functional requirements and candidate design concepts and materials that are identified to have the best potential to meet the cost and performance goals for the flat plate solar array project are described. Available data on encapsulant material properties, fabrication processing, and module life and durability characteristics are presented.

Cuddihy, E.↗

NASA NTRS1981

Development of an advanced Sabatier CO2 reduction subsystem

A preprototype Sabatier CO2 reduction subsystem was successfully designed, fabricated and tested. The lightweight, quick starting (less than 5 minutes) reactor utlizes a highly active and physically durable methanation catalyst composed of ruthenium on alumina. The use of this improved catalyst permits a simple, passively controlled reactor design with an average lean component H2/CO2 conversion efficiency of over 99% over a range of H2/CO2 molar ratios of 1.8 to 5 while operating with process flows equivalent to a crew size of up to five persons. The subsystem requires no heater operation after start-up even during simulated 55 minute lightside/39 minute darkside orbital operation.

Kleiner, G. N.↗

NASA NTRS1981

Physical aging of linear and network epoxy resins

Network and linear epoxy resins principally based on the diglycidyl ether of bisphenol-A and its oligomers are prepared and studied using diamine and anhydride crosslinking agents. Rubber modified epoxies and a carbon fiber reinforced composite are also investigated. All materials display time-dependent changes when stored at temperatures below the glass transition temperature after quenching (sub-T/g/ annealing). Solvent sorption experiments initiated after different sub-T(g) annealing times demonstrate that the rate of solvent uptake can be indirectly related to the free volume of the epoxy resins. Residual thermal stresses and water are found to have little effect on the physical aging process, which affects the sub-T(g) properties of uniaxial carbon fiber reinforced epoxy material. Finally, the importance of the recovery phenomenon which affects the durability of epoxy glasses is considered.

Kong, E. S.-W.↗

NASA NTRS1980

Evaluation of the hot corrosion behavior of thermal barrier coatings

Calcium silicate and yttria-stabilized ZrO2/(M-Cr-Al-Y) thermal barrier coating systems on air-cooled specimens were exposed to sodium- plus vanadium-doped Mach 0.3 combustion gases. The thermal barrier coating endurance was determined to be a strong inverse function of the ceramic coating thickness. Coating system durability was increased through the use of Ni-Cr-Al-Y and Co-Cr-Al-Y bond coatings with high chromium and aluminum contents. Chemical and electron microprobe analyses supported the predictions of condensate compositions and the determination of their roles in causing spalling of the ceramic coatings.

Hodge, P. E.↗

NASA NTRS1982

Development and operating characteristics of an advanced two-stage combustor

Results are presented from an experimental program aimed at optimizing the features of an advanced two-stage combustor that currently is being developed as part of the National Aeronautics and Space Administration/Pratt & Whitney Aircraft Energy Efficient Engine program. The combustor is designed to meet stringent goals for performance, emissions, durability and operational characteristics. An overview of the design selection process in light of these goals is discussed. Combustor rig test results, which highlight the techniques used to reduce emissions, development of the pilot and main power zone fuel injection systems, and methods of achieving efficient fuel staging, are presented.

Greene, W.↗