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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 1,189 records · Page 66

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NASA NTRS1973

Infrared telescopes for a space observatory

A cryogenically cooled infrared telescope of 1 to 2 meter aperture is discussed. Advantages of the space environment are detailed, and design considerations for cooled telescopes are given, leading to a schematic and preliminary design of a telescope for the space shuttle. The advantages of the sortie mode to an infrared observatory are dealt with and possible use of an ambient temperature telescope is discussed. Costs of infrared telescope observation are indicated.

Witteborn, F. S.↗

NASA NTRS1974

Two-position dc pulse voltage stabilizer

The advantages of the dc pulse voltage stabilizers over the continuous action stabilizers are described. These advantages include higher efficiency, low sensitivity to the ambient temperature and insignificant size and weight. A comparison is made between the schematics of the known two position pulse stabilizer with a Schmitt trigger and that developed by the author. A characteristic feature of the improved system is the increased stabilization coefficient and the possibility of smooth regulation of the output voltage. A practical schematic is presented for the improved two position pulse stabilizer along with its parameters.

Osadchiy, V. I.↗

NASA NTRS1973

A mercury flow meter for ion thruster testing

The theory of operation of the thermal flow meter is presented, and a theoretical model is used to determine design parameters for a device capable of measuring mercury flows in the range of 0 to 5 gm/hr. Flow meter construction is described. Tests performed using a positive displacement mercury pump as well as those performed with the device in the feed line of an operating thruster are discussed. A flow meter response time of about a minute and a sensitivity of about 10 mv/gm/hr are demonstrated. Additional work to relieve a sensitivity of the device to variations in ambient temperature is indicated to improve its quantitative performance.

Wilbur, P. J.↗

NASA NTRS1973

Evaluation of several additional dry lubricants for spacecraft applications

Four transfer-film ball-bearing retainer materials were evaluated for their lubricating ability and wear capability under conditions of 120-gram radial load, 450-gram axial load, 3600-rpm unidirectional rotation, 23 C ambient temperature, and less than .1 microtorr pressure, using R-2 sized unshielded ball bearings. The 'stop-test' criterion was a total of one billion revolutions or a torque buildup greater than 18 gm-cm per bearing pair. A PTFE-fiberglass-MoS2 composite, a PTFE-bronze composite, and a tantalum-molybdenum-MoS2 composite operated for one billion revolutions without reaching the 18-gram torque limit. A p-oxybenzoyl polymer-MoS2 composite operated sixteen million revolutions before reaching the 18-gm cm stop-test torque. The first three materials are considered as suitable lubricants under the test conditions employed.

Vest, C. E.↗

NASA NTRS1974

NaK-nitrogen liquid metal MHD converter tests at 30 kw

The feasibility of electrical power generation with an ambient temperature liquid-metal MHD separator cycle is demonstrated by tests in which a NaK-nitrogen LM-MHD converter was operated at nozzle inlet pressures ranging from 100 to 165 N/sq cm, NaK flow rates from 46 to 72 kg/sec, and nitrogen flow rates from 2.4 to 3.8 kg/sec. The generator was operated as an eight-phase linear induction generator, with two of the eight phases providing magnetic field compensation to minimized electrical end losses at the generator channel inlet and exit.

Cerini, D. J.↗

NASA NTRS1974

Jet noise from coaxial nozzles over a wide range of geometric and flow parameters

Free field pure jet noise data were taken for a large range of coaxial nozzle configurations. The core nozzles were circular (1 to 4 in. diam.) and plug types. The fan to core area ratio varied from 0.7 to 43.5, while the velocity ratio typically varied from 0 to 1. For most cases the two nozzles were coplanar but large axial extensions of either nozzle were also tested. Correlation of the data resulted in a simple procedure for estimating ambient temperature subsonic coaxial jet noise spectra over a wide range of geometric and flow parameters.

Olsen, W.↗

NASA NTRS1973

Noise tests of a high-aspect-ratio slot nozzle with various V-gutter target thrust reversers

The results of experiments on the noise generated by a 1.33 x 91.4 cm slot nozzle with various V-gutter reversers are presented. The experiments were conducted with near-ambient temperature jets at nozzle pressure ratios of 1.25 to 3.0, yielding jet velocities of about 190 to 400 m/sec. At pressure ratios of 2 or less, the reversers, in addition to being noisier than the nozzle alone, also had a more uniform directional distribution and more high-frequency noise. At pressure ratios above 2, the nozzle alone generated enough shock noise that the levels were about the same as for the reversers. The maximum overall sound pressure level and the effective overall sound power level both varied with the sixth power of jet velocity over the range tested.

Stone, J. R.↗

NASA NTRS1974

Biological modulation of the earth's atmosphere

Review of the evidence that the earth's atmosphere is regulated by life on the surface so that the probability of growth of the entire biosphere is maximized. Acidity, gas composition including oxygen level, and ambient temperature are enormously important determinants for the distribution of life. The earth's atmosphere deviates greatly from that of the other terrestrial planets in particular with respect to acidity, composition, redox potential and temperature history as predicted from solar luminosity. These deviations from predicted steady state conditions have apparently persisted over millions of years. These anomalies may be evidence for a complex planet-wide homeostasis that is the product of natural selection. Possible homeostatic mechanisms that may be further investigated by both theoretical and experimental methods are suggested.

Margulis, L.↗

NASA NTRS1974

The resistance of selected high strength alloys to embrittlement by a hydrogen environment

Selected high strength iron base and cobalt base alloys with yield strengths in the range from 1233 to 2129 MN per sq m (179 to 309 KSI) were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced epsilon prime-hcp martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level to a maximum of 2129 MN per sq m (309 KSI). High-strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.

Benson, R. B., Jr.↗

NASA NTRS1974

Influence of gaseous hydrogen on Inconel 718

The embrittlement of Inconel 718 by exposure to 34.5 MN/sq m hydrogen at ambient temperature was found to be a function of both forming operation and heat treatment. The embrittlement, as measured by reduction of notch strength in hydrogen as compared to helium, was decreased by a fine-grain size and was most severe for coarse-grained structures containing a continuous or nearly continuous precipitate tentatively identified as Ni3Cb. Tests performed on unnotched specimens showed that the strain at which surface cracks initiate in 34.5 MN/sq m hydrogen was approximately 3% and was independent of prior forming operation or heat treatment.

Walter, R. J.↗

NASA NTRS1975

Investigations of multiple jets in a crossflow

Study was conducted to determine penetration and mixing characteristics of multiple jets of ambient temperature air injected perpendicularly into ducted mainstream of hot combustion gases.

Walker, R. E.↗

NASA NTRS1974

The resistance of selected high strength alloys to embrittlement by a hydrogen environment

Selected high strength iron base and cobalt base alloys were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level. High strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.

Benson, R. B., Jr.↗

NASA NTRS1974

The resistance to embrittlement by a hydrogen environment of selected high strength iron-manganese base alloys

Fe-16Mn and Fe-25Mn base alloys, which had been cold worked to yield strength levels of 201 and 178 KSI, were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature under the loading conditions employed in this investigation. Transmission electron microscopy established that bands of epsilon phase martensite and fcc mechanical twins were formed throughout the fcc matrix when these alloys were cold worked. In the cold worked alloys a high density of crystal defects were observed associated with both types of strain induced structures, which should contribute significantly to the strengthening of these alloys. High strength iron base alloys can be produced which appear to have some resistance to degradation of mechanical properties in a hydrogen environment under certain conditions.

Benson, R. B., Jr.↗

NASA NTRS1975

Variable combustor geometry for improving the altitude relight capability of a double annular combustor

A test program was conducted to evaluate several ways of improving the altitude relight capability of a double annular ram-induction combustor designed for Mach 3.0 cruise operation. Using various techniques including two modes of simulated combustor variable geometry, altitude relights were obtained down to a pressure of 3.6 newtons per square centimeter against 7.05 newtons per square centimeter for the unmodified combustor. This was at a test condition of 0.05 reference Mach number using ambient temperature inlet air and fuel.

Schultz, D. F.↗

NASA NTRS1975

Experimental evaluation of the tensor polynomial failure criterion for the design of composite structures

The experimental measures and techniques are described which are used to obtain the strength tensor components, including cubic terms. Based on a considerable number of biaxial pressure tests together with specimens subjected to a constant torque and internal pressure, a modified form of the plane stress tensor polynomial failure equation was obtained that was capable of predicting ultimate strength results well. Preliminary data were obtained to determine the effect of varying post cure times and ambient temperatures (-80 F to 250 F) on the change in two tensor strength terms, F sub 2 and F sub 22. Other laminate configurations yield corresponding variations for the remaining strength parameters.

Tennyson, R. C.↗

NASA NTRS1975

Outdoor flat-plate collector performance prediction from solar simulator test data

Solar collector performance data obtained from tests with a simulator was modified for real-life conditions. The data obtained with the simulator was corrected for the variable conditions of ambient temperature, wind, incident angle, flow rate, etc., that are encountered outdoors. Modification of simulator data was accomplished by combining experiment with theory. The technique was demonstrated by application to a spectrally selective and a nonselective type of collector. This kind of modified simulator collector performance data should be valuable in solar systems analysis and for collector performance ranking based on all-day calculated conditions.

Simon, F. F.↗

NASA NTRS1975

Friction and wear of tin and tin alloys from minus 100 C to 150 C

Sliding friction experiments were conducted with an iron (110) single-crystal pin sliding on single and polycrystalline tin and tin alloys. Specimens were examined at various ambient temperatures from -100 to 150 C. Applied loads varied from 1 to 50 grams, and sliding velocity was constant at 0.7 mm/min. Results indicate that the crystal transformation of tin influences the friction coefficient. Friction was higher for the diamond structure (gray tin) than it was for the body-centered tetragonal structure (white tin). Bismuth arrested the crystal transformation, which resulted in constant friction over the temperature range -100 to 150 C. Both copper and aluminum enhanced the kinetics of transformation, with aluminum producing a nearly twofold change in friction with the crystal transformation.

Buckley, D. H.↗

NASA NTRS1975

Space shuttle/food system study. Volume 1: Technical volume, oven study

The baseline space shuttle galley was designed to utilize lightweight rehydratable foods, to be prepared for consumption by rehydration with chilled or hot water. The impact is examined of an extension of food types to include thermostabilized food, at ambient temperature, and frozen foods on the baseline design of the shuttle galley. Weight, volume, and power penalities associated with heating thermostabilized and frozen foods by means of a hot air convection heating system and a conduction heating system are determined along with the impact on crew/galley interface and meal preparation.

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