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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Study and development of acoustic treatment for jet engine tailpipes

A study and development program was accomplished to attenuate turbine noise generated in the JT3D turbofan engine. Analytical studies were used to design an acoustic liner for the tailpipe. Engine ground tests defined the tailpipe environmental factors and laboratory tests were used to support the analytical studies. Furnace-brazed, stainless steel, perforated sheet acoustic liners were designed, fabricated, installed, and ground tested in the tailpipe of a JT3D engine. Test results showed the turbine tones were suppressed below the level of the jet exhaust for most far field polar angles.

Nelson, M. D.↗
NASA NTRS1972

Investigations of high power problems in space shuttle antenna designs

A study program is discussed which includes a survey of industry and government laboratories and was undertaken to determine the state of the art in dealing with problems of high power levels in reentry antenna design. A laboratory program to develop techniques for testing dielectric materials for effects on RF transmission is also considered, with emphasis on high power applications in space and reentry flights. The study program resulted in a set of guidelines for avoiding breakdown in antenna design. A discussion of temperature effects on dielectric breakdown is also given. From the laboratory program, a description is presented of techniques for (1) heating with a carbon arc image furnace, (2) temperature measurement (using thermocouples and an infrared pyrometer), (3) mass spectrometric monitoring of outgassing, (4) testing for RF breakdown in both heated dielectrics and the dielectric/air and dielectric/plasma interfaces. Data and observations are reported from technique development using candidate shuttle materials falling into three categories: (1) lightweight refractory foams, (2) dense RF window materials, and (3) ablative materials.

Taylor, W. C.↗
NASA NTRS1972

Some studies on the behavior of W-RE thermocouple materials at high temperatures

Bare 0.25 mm diameter W-Re alloy thermoelements (W, W-3% Re, W-5% Re and W-25%) and BeO-insulated W-3% Re and W-25% Re thermoelements were examined for metallurgical, chemical and thermal emf changes after testing for periods up to 1000 hours at temperatures principally in the range 2000 to 2400 K. Environments for the tests consisted of high purity argon, hydrogen, helium or nitrogen gases. Commercially obtained bare-wire thermoelements typically exhibited a shift in their emf-temperature relationship upon initial exposure. The shift was completed by thermally aging the W-3% Re thermoelement for 1 hour and the W-25% Re thermoelement for 2 minutes at 2400 K in argon or hydrogen. Aged thermoelements experienced no appreciable drift with subsequent exposure at 2400 K in the gaseous environments. The chemically doped W3% Re thermoelement retained a small-grained structure for exposure in excess of 50 hours at 2400 K. BeO-insulated thermoelement assemblies showed varied behavior that depended upon the method of exposure. However, when the assemblies were heated in a furnace, no serious material incompatibility problems were found if the materials were given prior thermal treatments. Thermocouples, assembled from aged W-3% Re and W-25% Re thermoelements and degassed sintered BeO insulators, exhibited a drift of only 2 to 3 K during exposure in argon at 2070 K for 1029 hours.

Burns, G. W.↗
NASA NTRS1972

Development of a high irradiance source

Irradiance levels up to 17.27 sq in/sec. with a nonuniformity ratio of 1.07 have been developed to simulate high heat flux loads on the surface of difference materials. This has been achieved by an arc image furnace utilizing a 50 kw xenon short arc lamp mounted within an elliptical collector.

Lunde, A. R.↗
NASA NTRS1972

Method for measuring static Young's modulus of tungsten to 1900 K

An instrument system was developed and tested to measure static Young's modulus of elasticity of refractory metals in tension at temperatures to 1900 K. The extensometer uses capacitance displacement sensors for measuring total elongation of a specimen and incorporates a unique high-resolution remote zero-adjusting mechanism. Details of a method for calibrating capacitance displacement sensors at temperatures to 800 K are included. The system was built to adapt to a vacuum furnace on a tensile machine and was tested on unalloyed tungsten rod specimens. The test results show that the system can measure the modulus of tungsten to 1900 K to within a precision of + or - 5 percent. The uncertainty of the measurement is estimated to be of the same order as the precision.

Harrigill, W. T., Jr.↗
NASA NTRS1972

Manufacture, assembly, and delivery of beryllium test panels

Details of the fabrication and assembly of two 99 cm by 99 cm (39 in. by 39 in.) beryllium heat shield test panels are presented. Each panel consists of two hat-stiffened, formed skins which overlap a transverse slip joint at the center of the panel; clips join the two skins at the slip joint, and continuous standoffs are provided at the ends of the panel. The hat-stiffeners are joined to the skin by furnace-brazing, using the braze alloy BAg 18. The parts are generally 0.051 cm (0.020 in.) thick. Tools used to form the detail parts are shown, together with the results of preliminary forming and brazing trials to verify processing techniques. Problems encountered in the manufacture of the panels are discussed.

Source record↗
NASA NTRS1970

Preliminary terrestrial based experiments on gravity-affected crystal growth

Tin was melted in a heating assembly secured to the arm of a centrifuge. The furnace was allowed to pivot and reach its equilibrium angle of swing for the gravity force being experienced. The crucible was cooled during rotation to allow the growth of single crystals. The crystals were etched for the purpose of observing the growth striations. Slices were removed from some of the crystals to permit observation of the striations in the interior. Visual analyses were made with a scanning electron microscope. Preliminary conclusions relating the appearance of the striations to gravity forces and the affected growth mechanisms are presented. Further experiments that will verify these conclusions and determine other gravity effects are proposed.

Johnston, M. H.↗
NASA NTRS1970

Test of airborne fluorometer over land surfaces and geologic materials

Response of an experimental Fraunhofer line discriminator to a wide range of surficial deposits common in deserts and semideserts was tested in the laboratory and from an H-19 helicopter. No signals attributable to fluorescence were recorded during 540 miles of aerial traverses over southeastern California and west-central Arizona. It was concluded that exposed surfaces of target materials throughout the traverses were either nonluminescent at 5890 A or not sufficiently so to be detectable. It cannot be ruled out that the lack of fluorescence is partly attributable to surficial coatings of nonluminescent weathered material. The principal route surveyed from the air was from Needles, California to Furnace Creek Ranch, Death Valley and return, via the Amargosa River valley, Silurian Lake (dry), Silver Lake (dry), and Soda Lake (dry). Principal targets traversed were unconsolidated clastic sediments ranging from silty clay to cobbles, and a wide range of evaporite deposits.

Stoertz, G. E.↗
NASA NTRS1972

Oxidation resistant porous material for transpiration cooled vanes

Porous metal sheet with controlled permeability was made by space winding and diffusion bonding fine wire. Two iron-chromium-aluminum alloys and three-chromium alloys were used: GE 1541 (Fe-Cr-Al-Y), H 875 (Fe-Cr-Al-Si), TD Ni Cr, DH 245 (Ni-Cr-Al-Si) and DH 242 (Ni-Cr-Si-Cb). GE 1541 and H 875 were shown in initial tests to have greater oxidation resistance than the other candidate alloys and were therefore tested more extensively. These two materials were cyclic furnace oxidation tested in air at 1800 and 2000 F for accumulated exposure times of 4, 16, 64, 100, 200, 300, 400, 500, and and 600 hours. Oxidation weight gain, permeability change and mechanical properties were determined after exposure. Metallographic examination was performed to determine effects of exposure on the porous metal and electron beam weld joints of porous sheet to IN 100 strut material. Hundred hour stress rupture life and tensile tests were performed at 1800 F. Both alloys had excellent oxidation resistance and retention of mechanical properties and appear suitable for use as transpiration cooling materials in high temperature gas turbine engines.

Madsen, P.↗
NASA NTRS1972

Production of fibers by a floating zone fiber drawing technique

A CO2 laser heated, floating zone fiber growth process was developed. The resulting Al2O3 fibers exhibited the high room temperature strengths for large diameter fibers as well as high specific creep rupture strengths observed at 1093 C and 1316 C (2000 F and 2400 F). Single crystal fibers of TiC and Y2O3 were also grown. An optical system was developed to focus four CO2 laser beams onto the surface of a feed rod permitting the formation of highly controllable molten zones. The optical system permitted energy densities and angle of incidence of the beams to be adjusted over wide ranges. This optical system was incorporated into a controlled atmosphere, fiber growth furnace. The two principal advantages of a CO2 laser heat source are that ambient atmospheres may be freely selected to optimize fiber properties and the laser has no inherent temperature limit, so extremely high melting point materials can be melted. Both advantages were demonstrated.

Haggerty, J. S.↗
NASA NTRS1972

Improving the efficiency of GaP LED's which emit green light

A study of techniques for preparing n-type material and junctions which yield the most consistent high diode efficiency values high lighted the role that Ga vacancies and/or associated defects play in reducing the green luminescent efficiency of n-type GaP. A useful method for obtaining good quality material was developed. It is shown that junction formation at high temperatures in a process where the n to p transition occurs without removing the substrate from the furnace yields devices superior to those obtained by diffusion or double epitaxy in the conventional manner previously used for GaP junction formation.

Ladany, I.↗
NASA NTRS1971

Practical field repair of fused slurry silicide coating for space shuttle t.p.s.

Study of short-time high-temperature diffusion treatments as part of a program of development of methods of reapplying fused slurry silicide coating in the field. The metallographic structure and oxidation behavior of R512E applied to Cb-752 coated under simulated field repair conditions was determined. Oxidation testing in reduced pressure environment has shown that performance equivalent to furnace-processed specimens can be obtained in a two-minute diffusion at 2700 F.

Reznik, B. D.↗
NASA NTRS1971

A program in refractory metal thermocouple research.

Description of a refractory metal thermocouple research program, directed towards establishing the parameters that are necessary to achieve reliable, long term, high temperature thermocouple performance. A description of special apparatus for exposing bare-wire thermoelements to high temperatures in vacuum and in high purity gaseous environments is given, and the design and performance of an ultra-high-vacuum, high-temperature furnace system are described. Bare-wire W-3 per cent Re and W-25 per cent Re thermoelements were exposed at 2400 K in argon, hydrogen, or vacuum, and experienced a shift in their emf-temperature relationship upon initial exposure. After the initial shift, the thermoelements exposed in the gaseous environments experienced no significant further change in their emf-temperature relationship for periods up to 1000 hrs. The thermoelements exposed in vacuum continually drifted in their emf-temperature relationship as a result of the preferential loss of Re by evaporation.

Burns, G. W.↗
NASA NTRS1972

Practical method for diffusion welding of steel plate in air.

Description of a simple and easily applied method of diffusion welding steel plate in air which does not require a vacuum furnace or hot press. The novel feature of the proposed welding method is that diffusion welds are made in air with deadweight loading. In addition, the use of an autogenous (self-generated) surface-cleaning principle (termed 'auto-vac cleaning') to reduce the effects of surface oxides that normally hinder diffusion welding is examined. A series of nine butt joints were diffusion welded in thick sections of AISI 1020 steel plate. Diffusion welds were attempted at three welding temperatures (1200, 1090, and 980 C) using a deadweight pressure of 34,500 N/sq m (5 psi) and a two-hour hold time at temperature. Auto-vac cleaning operations prior to welding were also studied for the same three temperatures. Results indicate that sound welds were produced at the two higher temperatures when the joints were previously fusion seal welded completely around the periphery. Also, auto-vac cleaning at 1200 C for 2-1/2 hours prior to diffusion welding was highly beneficial, particularly when subsequent welding was accomplished at 1090 C.

Moore, T. J.↗
NASA NTRS1972

Brazing of refractory, superalloy, and composite materials for Space Shuttle applications.

Research work concerning the metallic portion of the shuttle-orbiter heat shield (expected to experience temperatures up to 2500 F) is described. The five metals being evaluated are TD-Ni-Cr, Cb-C129Y, Cb752, Hayes 188, and Inconel 625. Brazing techniques whereby pairs of these materials are joined into thin-membered assemblies for heat shield applications are described. Results obtained with the vacuum-furnace brazing process are examined. In addition, the use of brazed aluminum-boron metal-matrix-contoured composite structures for heat shield applications is evaluated.

Beuyukian, C. S.↗
NASA NTRS1971

Compressibility measurements of gases using externally heated pressure vessels.

Most of the data collected under conditions of high temperature and pressure have been determined using a thick-walled bomb of carefully measured and fixed volume which is externally heated by an electric furnace or a thermostatically controlled bath. There are numerous variations on the basic method depending on the pressure-temperature range of interest, and the particular gas or gas mixture being studied. The construction and calibration of the apparatus is discussed, giving attention to the pressure vessel, the volume of the bomb, the measurement of pressure, the control and measurement of temperature, and the measurement of the amount and composition of gas in the bomb.

Presnall, D. C.↗
NASA NTRS1972

Silica reinforcement and char reactions in the Apollo heat shield.

Reactions of the silica reinforcement fiber and ablation char of the Apollo heat shield have been investigated by laboratory tests in an arc image furnace (at temperature levels up to 5000 R, pressures up to 0.7 atm, and heat flux similar to reentry) and by an actual reentry test. Microchemical analyses and X-ray diffraction studies have been made to determine the presence of SiC formation in the char. Experimental data and analytical predictions of thermal and density profiles have been compared for the ablation of virgin heat shield and precharred materials to determine the effects of SiC formation on ablation performance. In all analyses, general agreement was found between chemical composition and the thermal predictions for laboratory tests and reentry materials. In all ablated materials, SiC was formed in the front surface of the char. The highest SiC content found was 58% by weight and found in a high-pressure environment. The SiC formed was found to act as a heat sink in the ablation process and can lower the front surface temperature by 300 R.

Cagliostro, D. E.↗