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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Method of forming shrink-fit compression seal

A method for making a glass-to-metal seal is described. A domed metal enclosure having a machined seal ring is fitted to a glass post machined to a slight taper and to a desired surface finish. The metal part is then heated by induction in a vacuum. As the metal part heats and expands relative to the glass post, the metal seal ring, possessing a higher coefficient of expansion than the glass post, slides down the tapered post. Upon cooling, the seal ring crushes against the glass post forming the seal. The method results in a glass-to-metal seal possessing extremely good leak resistance, while the parts are kept clean and free of the contaminants.

Podgorski, T. J.↗
NASA NTRS1977

Relation of morphology of electrodeposited zinc to ion concentration profile

The morphology of electrodeposited zinc was studied with special attention to the ion concentration profile. The initial concentrations were 9M hydroxide ion and 1.21M zincate. Current densities were 6.4 to 64 mA/sq cm. Experiments were run with a horizontal cathode which was observed in situ using a microscope. The morphology of the zinc deposit was found to be a function of time as well as current density; roughly, the log of the transition time from mossy to large crystalline type deposit is inversely proportional to current density. Probe electrodes indicated that the electrolyte in the cathode chamber was mixed by self inducted convection. However, relatively large concentration gradients of the involved species existed across the boundary layer of the cathode. Analysis of the data suggests that the morphology converts from mossy to large crystalline when the hydroxide activity on the cathode surface exceeds about 12 M. Other experiments show that the pulse discharge technique had no effect on the morphology in the system where the bulk concentration of the electrolyte was kept homogeneous via self induced convection.

May, C. E.↗
NASA NTRS1977

Proving the correctness of the flight director program EADIFD, volume 1

EADIFD is written in symbolic assembly language for execution on the C4000 airborne computer. It is a subprogram of an aircraft navigation and guidance program and is used to generate pitch and roll command signals for use in terminal airspace. The proof of EADIFD was carried out by an inductive assertion method consisting of two parts, a verification condition generator and a source language independent proof checker. With the specifications provided by NASA, EADIFD was proved correct. The termination of the program is guaranteed and the program contains no instructions that can modify it under any conditions.

Lee, F. J.↗
NASA NTRS1976

Thermionic topping for central station power plants

This paper describes recent results of the second phase of system analyses on the thermionic topping cycle. A comparison is made among various thermionic heat-exchanger (THX) geometries. Two methods of transferring electric power are considered. In the first, power is provided at relatively high voltages by coupling it out inductively via transformers built into the THX modules. In the second method, converter cells are series-connected within a THX module and external power conditioning is used. The results show that the use of a thermionic topping cycle can result in significant improvements in overall system efficiency.

Britt, E. J.↗
NASA NTRS1976

Measurements of Sc I gf-values

Absolute gf-values were obtained for 98 transitions in neutral scandium by the hook method using an inductively coupled heat-pipe oven. Of the 98 lines, 51 are classified, 33 are unclassified lines that occur in pairs with the lower energy level identified, and 14 are unclassified but are believed to originate from one of the two lower levels of the ground state. The results are compared with semiempirical and other measurement results in the literature.

Parkinson, W. H.↗
NASA NTRS1976

A theoretical study of the acoustic impedance of orifices in the presence of a steady grazing flow

Oscillatory fluid flow in the vicinity of a circular orifice with a steady grazing flow is analyzed. A simplified system of partial differential equations is obtained by starting with the momentum and continuity equations and by assuming that the flow can be represented as an oscillatory motion superimposed on the (known) steady flow. It is found that the equations are linear in the region where grazing-flow effects dominate; a solution and the resultant orifice impedance are given for this region. It is tentatively concluded that orifice resistance is directly proportional to grazing-flow velocity and that the orifice inductive end correction is not a function of grazing flow.

Rice, E. J.↗
NASA NTRS1977

A high accuracy all-angle gyroscope readout using quantized flux

Means are described to use SQUID magnetometer flux counting and the London moment of a spherical superconducting gyroscope to read out the gyroscope spin axis direction to an accuracy of at least 23 bits per quadrant. The system is discussed in analogy to optical fringe counting as applied to distance measurement. Several methods of applying both analog and digital SQUID magnetometers to the readout problem are given, as well as limitations on each. Described are two methods of increasing the flux available for measurement: magnetizing the gyroscope with a trapped field, and optimizing readout circuit inductances. Finally, the same principle on which the gyroscope readout is based is applied to a description of a high accuracy, flux counting, digital angle encoder.

Anderson, J. T.↗
NASA NTRS1977

Studies of hydride formation and superconductivity in hydrides of alloys Th-M /M = La, Y, Ce, Zr and Bi/

In order to gain a better insight into both the unusual composition of ThH15 and its superconductivity, an experimental study was conducted to assess the influence of partial replacement of Th in Th4H15 by elements which allow for a systematic alteration of spatial and electronic effects. For this purpose, substituent elements with the same number of valence electrons (4) but of smaller size (Zr) as well as elements with a smaller number of valence electrons (3) and either larger (La) or smaller size (Y) were selected. A few data with Ce and Bi as substituent atoms are also included. The matrix alloys for hydriding were obtained by induction melting under Ar in water-cooled Cu boats. Superconducting transition temperatures are found to decrease on substitution for Th in Th4H15. Hydrides derived from LaH3 by substitution for La by Th do not become superconducting. It is suggested that superconductivity in Th4H15 is connected with a deviation from the exact stoichiometry of Th4H15. A model of unsatisfied valencies may be of more general validity in predicting superconductivity.

Oesterreicher, H.↗
NASA NTRS1976

New potentials for conventional aircraft when powered by hydrogen-enriched gasoline

Hydrogen enrichment for aircraft piston engines is under study in a new NASA program. The objective of the program is to determine the feasibility of inflight injection of hydrogen in general aviation aircraft engines to reduce fuel consumption and to lower emission levels. A catalytic hydrogen generator will be incorporated as part of the air induction system of a Lycoming turbocharged engine and will generate hydrogen by breaking down small amounts of the aviation gasoline used in the normal propulsion system. This hydrogen will then be mixed with gasoline and compressed air from the turbocharger before entering the engine combustion chamber. The paper summarizes the results of a systems analysis study. Calculations assuming a Beech Duke aircraft indicate that fuel savings on the order of 20% are possible. An estimate of the potential for the utilization of hydrogen enrichment to control exhaust emissions indicates that it may be possible to meet the 1979 Federal emission standards.

Menard, W. A.↗
NASA NTRS1977

An experimental and analytical study of acetylene and ethylene oxidation behind shock waves

An experimental and analytical study of the oxidation of acetylene and ethylene behind incident shock waves was carried out over the temperature range 1815-2365 K at reaction pressures between 1.1 and 1.7 atm. The oxidation process was monitored by measuring radiation from carbon dioxide, carbon monoxide, and the reaction O + CO yields CO2 + h nu. The recorded emission profiles were analyzed to obtain concentrations for carbon dioxide, carbon monoxide, and the product of oxygen atom and the carbon monoxide concentrations. On the basis of this data and induction time data reported in the literature, kinetic models for acetylene and ethylene oxidation were assembled.

Jachimowski, C. J.↗
NASA NTRS1977

Proving the correctness of a flight-director program for an airborne minicomputer

Program verification procedures are described and used to determine the correctness of a program written for an airborne computer. The basic method relies on the inductive assertion method of Floyd (1967), modified and extended for application to a machine-language situation. Correctness considerations in the flight director program include self-modification, system correctness, executable instructions, overflow, approximate calculations with fractional quantities, and fixed point scaling. An example proof of correctness, which proceeds by proving the correctness of a certain subroutine, is provided.

Maurer, W. D.↗
NASA NTRS1978

Optical traffic-sensing concept

Scaled-up optical proximity detector is versatile traffic sensor that replaces or augments existing systems such as inductive loops. Photosensor which does not depend on ambient light has several features that protect it against spurious or ambiguous inputs. It could be implemented in several forms to cope with different roadway conditions.

Johnston, A. R.↗
NASA NTRS1979

High-Speed, high-power, switching transistor

Silicon transistor rate for 200 angstroms at 400 to 600 volts combines switching speed of transistors with ruggedness, power capacity of thyristor. Transistor introduces unique combination of increased power-handling capability, unusally low saturation and switching losses, and submicrosecond switching speeds. Potential applications include high power switching regulators, linear amplifiers, chopper controls for high frequency electrical vehicle drives, VLF transmitters, RF induction heaters, kitchen cooking ranges, and electronic scalpels for medical surgery.

Carnahan, D.↗
NASA NTRS1977

Sail GTS ground system analysis: Avionics system engineering

A comparison of two different concepts for the guidance, navigation and control test set signal ground system is presented. The first is a concept utilizing a ground plate to which crew station, avionics racks, electrical power distribution system, master electrical common connection assembly and marshall mated elements system grounds are connected by 4/0 welding cable. An alternate approach has an aluminum sheet interconnecting the signal ground reference points between the crew station and avionics racks. The comparison analysis quantifies the differences between the two concepts in terms of dc resistance, ac resistance and inductive reactance. These parameters are figures of merit for ground system conductors in that the system with the lowest impedance is the most effective in minimizing noise voltage. Although the welding cable system is probably adequate, the aluminum sheet system provides a higher probability of a successful system design.

Lawton, R. M.↗
NASA NTRS1977

Continuation of surge life of transient voltage suppressor

Efforts expended in testing, analyzing and the development of a meaningful definition of the mean number of peak pulses before failure (mp2bf) levels of a family of transient voltage suppressor devices were documented. Tests were done to determine the ability of the transient suppressor to effectively and reliably protect against severe short term, millisecond range, and transient voltages of the types resulting from inductive load switching and induced lightning. Existing pulse testing instrumentation was utilized, interfaced to an automatic sequencing test rack accommodating up to 50 devices. Tests were performed in step stress increments of 25% beginning at 25% and extending thru 100% rated I(pp) for each voltage category. The four voltage types test were the 6.8V, 33V, 91V, and 190V. Engineering efforts addressed the problem of improving the reliability of the 190V types.

Clark, O. M.↗
NASA NTRS1977

Calculation of the magnetic field in the active zone of a hysteresis clutch

The initial distribution of magnetic induction in the armature stationary was calculated relative to the polar system of a hysteresis clutch. Using several assumptions, the problem is reduced to calculating the static magnetic field in the ferromagnetic plate with finite and continuous magnetic permeability placed in the air gap between two identical, parallel semiconductors with rack fixed relative to the tooth or slot position.

Ermilov, M. A.↗
NASA NTRS1977

Relevance of microelectronic education to industrial needs

The relevance of microelectronic education to industrial needs was evaluated, and four categories were surveyed: (1) facts and rules; (2) skills; (3) personality; and (4) deductive-inductive reasoning. Examples of specific items in each category are given to illustrate their meaning and it was indicated as to which items in each category are strongly impacted by microelectronics courses and laboratories.

Prince, J. L.↗
NASA NTRS1978

Photovoltaic power system tests on an 8-kilowatt single-phase line-commutated inverter

Efficiency and power factor were measured as functions of solar array voltage and current. The effects of input shunt capacitance and series inductance were determined. Tests were conducted from 15 to 75 percent of the 8 kW rated inverter input power. Measured efficiencies ranged from 76 percent to 88 percent at about 50 percent of rated inverter input power. Power factor ranged from 36 percent to 72 percent.

Stover, J. B.↗