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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Notes on Soviet space astronomy

Soviet space programs intended for making astronomical observations are reviewed. The Cosmos, Intercosmos, and Prognoz satellites designed for astronomical measurements are identified, and unmanned lunar and planetary missions are discussed, including the Luna, Lunokhod, Mars, and Venera programs. The Salyut 4 space station is described in detail along with the following major astronomical instruments: the Orbiting Solar Telescope 1, the infrared telescope spectrometer, the two solar spectrometers, the light-nuclei mass spectrometer, and the Filin and RT-4 X-ray telescopes. The future of Soviet space astronomy is assessed, particularly the tasks of the Salyut 5 station and the scheduled launch of Salyut 6.

Oberg, J. E.↗
NASA NTRS1976

Thermal-stress fatigue behavior of twenty-six superalloys

The comparative thermal-stress fatigue resistances of 26 nickeland cobalt-base alloys were determined by fluidized bed tests. Cycles to cracking differed by almost three orders of magnitude for these materials, with directional solidification and surface protection showing definite benefit. The alloy-coating combination with the highest thermal-stress fatigue resistance was directionally solidified NASA TAZ-8A with an RT-SP coating. Its oxidation resistance was also excellent, showing approximately a 1/2 percent weight loss after 14,000 fluidized bed cycles.

Bizon, P. T.↗
NASA NTRS1977

Development of Si3N4 and SiC of improved toughness

The application of energy absorbing surface layers to Si3N4 and SiC was investigated. Among the layers studied were microcracked materials such as iron titanate and a silica-zircon mixture and porous materials such as reaction sintered Si3N4. Energy absorption due to microcrack extension upon impact was found not to be an important mechanism. Instead, the fivefold improvement in Charpy and ballistic impact at elevated temperature (1250 C and 1370 C) found for Fe2TiO5 was due to plastic deformation while similar improvement found for silica-zircon mixtures at RT was due to crushing of the porous material. Due to thermal expansion mismatch, these two materials could not withstand thermal cycling when used as energy absorbing surface layers on Si3N4. Reaction sintered Si3N4 layers on dense Si3N4 were found to give up to a sevenfold increase in ballistic impact resistance due to crushing of the layer upon impact. High porosity (45%), large particle size R.S. Si3N4 layers fabricated from -100, +200 mesh Si powder gave better impact improvement than less porous (30%), small particle size layers fabricated from -325 mesh Si powder.

Brennan, J. J.↗
NASA NTRS1978

New silicon monoxide masers

Seven Mira variable stars with silicon monoxide maser emission have been found. All are later than M4 and heavily reddened. Two were observed near maximum light. One, Y Cas, seems to bear out the correlation of 43-GHz SiO maser luminosity and mean spectral type at maximum light. RT Aql, however, falls about 1 mag below the expected brightness. A catalog of SiO maser stars is given.

Dickinson, D. F.↗
NASA NTRS1978

New High Temperature Cross Linking Monomers

This report describes the results of a one-year program designed to synthesize new, nonvolatile crosslinking monomers and to prove their feasibility in the development of lower temperature curing PMR-polyimide resins with high temperature capability. The objective of this program is to develop PMR-polyimide resins capable of being processed at a maximum temperature of 232C to 288C (450F to 500F) without sacrifice of the high temperature 316C (600F) capability of the state-of-the-art PMR-15 polyimide resin. Four monomethyl esters were synthesized and characterized for use in the crosslinking studies. It was found that all four crosslinkers were capable of entering into a crosslinking reaction to produce polymer specimens which were strong, dense and free of voids. The infrared and DSC studies of each crosslinker with monomers 4,4'-methylenedianiline (MDA) and the dimethyl ester of 3,3',4,4'-benzophenonetetracarboxylic acid (BTDE) comprising the resin systems, crosslinker/MDA/BTDE suggested that curing could be accomplished at 288C (550F). However, fabrication of dense, void free polymer specimens required a temperature of 316C (600F) and a pressure of 0.69 MPa (100 psi). The crosslinkers, monomethyl ester of 2,5-bicyclo[2.2.1]heptadiene-2,3-dicarboxylic acid (NDE) and monomethyl ester of maleic acid (MAE) were selected for evaluation in Celion 6000/PMR polyimide composites. These composites were characterized at RT, 288C (550F) and 316C (600F) initially and after isothermal aging at 288C (550F) and 316C (600F) for several hundred hours. The results of the isothermal aging studies suggested that both PMR systems NDE-MDA-BTDE and MAE-MDA-BTDE are promising candidates as matrices for addition type polyimide composites. These studies demonstrated that alternate crosslinkers to NE/MDA/BTDE are feasible, but mechanisms to lower the crosslinking temperature must be developed to provide lower temperature processing PMR-type polyimides.

Scola, Daniel A.↗
NASA NTRS1978

New cyanate and cyanamide resins as composite matrices

The synthesis, polymerization, and laminate properties of two dicyanates, copolymers thereof, and a dicyanamide were studied. The effect of humidity aging (322 K (49 C), 95% relative humidity) and also aging at 505 K (232 C) in circulating air on the RT and elevated temperature properties of HT-S and T-300 unidirectional laminates was determined.

Hergenrother, P. M.↗
NASA NTRS1979

Starspots as the cause of the intrinsic light variations in RS Canum Venaticorum type stars

A starspot model is proposed to interpret the light curves of three RS CVn type binary systems. Two of the systems are RS CVn and SZ Psc, which are detached, while the third system, RT Lac, is semidetached. Solar activity and the surface activity of the RS CVn type stars are compared. It is found that the spot model permits the detailed fitting of both the out-of-eclipse complications and the distorted shapes of the secondary eclipses in the light curves of these stars.

Eaton, J. A.↗
NASA NTRS1979

Development of silicon nitride of improved toughness

The application of reaction sintered Si2N4 energy absorbing surface layers to hot-pressed Si3N4 was investigated. The surface layer was formed by in-place nitridation of silicon powder. It was found that reaction sintered Si3N4 layers of 1 mm thickness, fabricated from either -100, +200, -200, or -325 mesh Si powder and nitrided in 96% N2/4% H2 so that approximately 20-25 vol % unnitrided Si remained in the layer, resulted in a sevenfold increase in ballistic impact resistance of a 0.64 cm thick hot-pressed SI3N4 substrate from RT 1370 C. Both NC-132 SI3N4, with MgO additive, and NCX-34 Si3N4, with Y2O3 additive, were evaluated as substrate material. The finer grain size -200 and -325 mesh nitrided Si layers were for their smoothness and relatively high density. It was found that nitriding in N2/H2 mixtures, rather than pure N2, resulted in a microstructure that did not substantially degrade the strength of the hot-pressed Si3N4 substrate. Thermal cycling tests on the RSSN/HPSN combinations from 200 C to 1370 C for 75 cycles in air did not degrade the impact resistance nor the interfacial bonding, although a large amount of internal silica formation occurred within the RSSN layer. Mach 0.8, 5 hr, hot gas erosion tests showed no surface recession of RSSN layers at 1200 C and slight surface recession at 1370 C.

Brennan, J. J.↗
NASA NTRS1980

LARC-13 adhesive development

A LARC-13 type adhesive system was developed and property data obtained that demonstrated improved thermomechanical properties superior to base LARC-13 adhesive. An improved adhesive for 589 K (600 F) use was developed by physical or chemical modification of LARC-13. The adhesive was optimized for titanium and composite bonding, and a compatible surface preparation for titanium and composite substrates was identified. The data obtained with the improved adhesive system indicated it would meet the 589 K (600 F) properties desired for application on space shuttle components. Average titanium lap shear data were: (1) 21.1 MPa (3355 psi) at RT, (2) 13.0 MPa (1881 psi) at 600 F, and (3) 16.4 MPa (2335) after aging 125 hours at 600 F and tested at 600 F.

Hill, S. G.↗
NASA NTRS1980

Si and GaAs photocapacitive MIS infrared detectors

Improvement of the previously reported photocapacitive MIS infrared detectors has led to the development of exceptional room-temperature devices. Unoptimized peak detectivities on the order of 10 to the 13th cm sq rt Hz/W, a value which exceeds the best obtainable from existing solid-state detectors, have now been consistently obtained in Si and GaAs devices using high-capacitance LaF3 or composite LaF3/native-oxide insulating layers. The measured spectral response of representative samples is presented and discussed in detail together with a simple theory which accounts for the observed behavior. The response of an ideal MIS photocapacitor is also contrasted with that of both a conventional photoconductor and a p-i-n photodiode, and reasons for the superior performance of the MIS detectors are given. Finally, fundamental studies on the electrical, optical, and noise characteristics of the MIS structures are analyzed and discussed in the context of infrared-detector applications.

Sher, A.↗
NASA NTRS1980

A molecular beam investigation of the oxidation of CO on Pt/9/111/x/100//

The CO oxidation on Pt/9(111)x(100)/ was studied by molecular beam relaxation spectroscopy (MBRS). The reaction proceeded via the reaction of adsorbed CO and adsorbed oxygen. No evidence for direct reactive collisions between gaseous CO and adsorbed atomic oxygen was seen. The second order rate constant was measured by linearizing the reaction system to be 10 to the -7th exp/-(9700 kcal/mole)RT/ per sq cm s. The relatively low pre-exponential factor was explained by transition state theory on the basis of a high partition function for adsorbed carbon monoxide obtained previously from studies of CO desorption on this surface.

Fair, J. A.↗
NASA NTRS1980

Internal coating of air-cooled gas turbine blades

Four modified aluminide coatings were developed for IN-792 + Hf alloy using a powder pack method applicable to internal surfaces of air-cooled blades. The coating compositions are Ni-19Al-1Cb, Ni-19Al-3Cb, Ni-17Al-20Cr, and Ni-12Al-20Cr. Cyclic burner rig hot corrosion (900 C) and oxidation (1050 C) tests indicated that Ni-Al-Cb coatings provided better overall resistance than Ni-Al-Cr coatings. Tensile properties of Ni-19Al-1Cb and Ni-12Al-20Cr coated test bars were fully retained at room temperature and 649 C. Stress rupture results exhibited wide scatter around uncoated IN-792 baseline, especially at high stress levels. High cycle fatigue lives of Ni-19Al-1Cb and Ni-12Al-20Cr coated bars (as well as RT-22B coated IN-792) suffered approximately 30 percent decrease at 649 C. Since all test bars were fully heat treated after coating, the effects of coating/processing on IN-792 alloy were not recoverable. Internally coated Ni-19Al-1Cb, Ni-19Al-3Cb, and Ni-12Al-20Cr blades were included in 500-hour endurance engine test and the results were similar to those obtained in burner rig oxidation testing.

Hsu, L. L.↗
NASA NTRS1981

High sensitivity operation of discrete solid state detectors of 4 K

Techniques are described to allow operation of discrete solid state detectors at 4 K with optimized junction field effect transistor (JFET) amplifiers. Three detector types cover the 0.6-4 micron spectral range with a noise equivalent power (NEP) of approximately 10 to the -16th per sq rt Hz for two of the types and potential improvement to this performance for the third. Lower NEPs can be anticipated at longer IR wavelengths.

Rieke, G. H.↗
NASA NTRS1982

Stratospheric CCN sampling program

Two one liter grab samples of stratospheric aerosol were returned from each of six U-2 sampling missions. Cloud condensation nuclei (CCN) spectra from each sample were obtained. Interest was centered on the effects of volcanic activity. Spurious particle generation was found to be a serious problem in container 9 LFT and a much smaller problem in container 9 RT. Initial studies of an option for improved sample containers and values were completed. A CCN spectrometer, able to operate at an internal pressure of 300 mb, was designed.

Rogers, C. F.↗
NASA NTRS1981

Development of CdO-graphite-Ag coatings for gas bearings to 427 C

Graphite is one of the most commonly known lubricants. Its effectiveness in a range between room temperature (RT) and 540 C is reportedly improved by adding cadmium oxide. CdO-graphite powder in a gas carrier has been used in numerous applications that rely on dry lubrication. A coating of this composition was developed and successfully tested in foil air bearings for long periods up to a temperature of 427 C and at a normal contacting load (during starting and stopping) of 14 kPa based on bearing projected area. The addition of ultra-fine silver to the CdO-graphite has improved the coating endurance. At 427 C, the CdO-graphite-Ag coating performed better than CdO-graphite without silver, both for extended periods at 14 kPa loading and for limited periods at 35 kPa. At 288 C, the coating was tested for an extended period up to 28 kPa and has also successfully completed high-speed shock tests to an acceleration level of 100g.

Bhushan, B.↗
NASA NTRS1982

Solution of the equation of radiative transfer for remote sensing over nonuniform surface reflectivity

An understanding of radiative transfer in the earth's atmosphere is a necessity for the remote sensing of surface reflectivity from satellites and aircraft. The range of the adjacency effect, which represents the effect of bright areas on the radiance above dark areas, is the main parameter that distinguishes atmospheric radiative transfer over a nonuniform surface from that over a uniform one. A radiative transfer model which expresses this range correctly is, therefore, critical for developing remote sensing methods for the case of an atmosphere over a nonuniform surface. The present investigation is concerned with the development of a new approximate solution of the radiative transfer (RT) equation. The solution is not limited to nonabsorbing atmospheres, but it will still be limited to nadir observations. The results compare favorably with Monte Carlo simulations.

Kaufman, Y. J.↗
NASA NTRS1982

Self-heated thermocouples for far-infrared detection

A novel self-heated Bi-Sb thermocouple for far-infrared detection has been developed. The detector is suitable for integration with monolithic antennas and imaging arrays. The device is fabricated in a single photolithography masking step using a photoresist-bridge technique. This bridge technique has also been used to make microbolometers with lower 1/f noise than those made by two conventional masking steps. The thermocouples have a noise equivalent power of 7 x 10 to the -10th W/sq rt of Hz and a 3-dB frequency response of 150 kHz.

Neikirk, D. P.↗
NASA NTRS1982

Mechanical properties of adhesive systems at cryogenic and other temperatures

This paper presents a summary of the National Transonic Facility (NTF) fan blade adhesive characterization tests. Data was obtained at -300 F, room temperature (RT) and 200 F. The adhesive characterization data was acquired using specimens fabricated from materials orientated to simulate the lay up of the fan blades. Specimen fabrication, characterization tests, test equipment, test data, results and concluding remarks are reported. Adhesive test results are presented for specimens of the following types: lap shear, double lap shear, butt, short beam shear, flexure, and differential strain.

Staton, W. L.↗