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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Self-synchronizing, bi-orthogonal coded PCM telemetry system

Communications and data handling system improves signal to noise ratio when transmission channel is perturbed by noise. Telemetry system consists of airborne source, Gaussian additive noise channel, and ground receiver unit. Advantages of system are given.

Miller, W.↗
NASA NTRS1972

A bi-stable optical device

Device was developed which produces short optical pulses of variable lengths with high peak power and without use of external modulators or independent light beams. Optical field intensity is built up inside cavity. At peak of its intensity, light is switched off.

Szoke, A.↗
NASA NTRS1972

Planetary resonances, bi-stable oscillation modes, and solar activity cycles

The natural resonance structure of the planets in the solar system yields resonance periods of 11.08 and 180 years. The 11.08 year period is due to resonance of the sidereal periods of the three inner planets. The 180-year period is due to synodic resonances of the four major planets. These periods are also observed in the sunspot time series. The 11-year sunspot cycles from 1 to 19 are separated into categories of positive and negative cycles, Mode 1 and Mode 2 cycles, and typical and anomalous cycles. Each category has a characteristic shape, magnitude, or duration, so that statistical prediction techniques are improved when a cycle can be classified in a given category. These categories provide evidence for bistable modes of solar oscillation. The next minimum is expected in 1977 and the next maximum in 1981 or later. These epoch values are 2.5 years later than those based on typical cycle characteristics.

Sleeper, H. P., Jr.↗
NASA NTRS1972

The design and development of a miniature bi-stable latching solenoid valve for low thrust resistojets

The design approach and development demonstration are presented for a flightweight, miniature, magnetic latching shutoff valve, suitable for use with the ruggedized H2 and NH3 resistojet and the biowaste resistojet. The design criteria established provided for compatibility with specified ruggedized resistojet propellants as well as the biowaste and other propulsion system propellants.

Lynch, R. A.↗
NASA NTRS1972

Determination of Optical Constants of in Bi from Reflectance Measurements

A fall in reflectance was noted from values obtained for a freshly cleaved sample to values obtained after periods of exposure of the surface to air. The decrease in reflectance with increased exposure time is attributed to formation of a surface layer insoluble in Freon or ethyl alcohol; it is assumed to be a tarnish layer. Computer processing was employed to calculate optical constants from reflectance data.

Martin, F. E.↗
NASA NTRS1976

Feasibility study of the design of Bi Ra Systems, Incorporated model 5301, 5101, and 3222 CAMAC modules for space use

Cost estimates are determined for redesigned modules. Consideration is given to incorporation of NASA approved components, component screening and documentation, as well as reduced power consumption. Results show that r designed modules will function reliably in a space environment of 50 C and withstand greater than 15 G's of random vibration between 40 Hz and 400 Hz.

Biswell, L.↗
NASA NTRS1977

Cyclical bi-directional rotary actuator

A thermally powered rotary actuator is disclosed which is used for positioning a shaft in first and second positions which are disposed 180 deg apart. A pair of heat extensible springs are attached to the shaft and to the frame of the rotary actuator for selectively rotating the shaft from one of its two positions to the other position upon the application of heat to one of the heat extensible springs. The heat extensible springs are preferably constructed from the alloy 55-Nitinol. In the preferred embodiment, a detent mechanism is provided for locking the rotatable shaft in its two rotary positions.

Stange, W. C.↗
NASA NTRS1976

New metal atom laser transitions in As, Bi, Ga, Ge, Hg, In, Pb, Sb, and Tl

A double discharge technique was used in the investigation. An initial discharge established between parallel arrays of tungsten pin electrodes was followed, after a variable time delay, by a high voltage (180 kV), short duration (50 nsec) secondary discharge between two aluminum main electrodes. Metal compounds, including metal alkyls, hydrides, and halides, were used to obtain the required metal atom concentrations. Twenty-four new laser transitions involving 9 different metal atoms were observed. The observed relations are shown in a number of partial energy-level diagrams.

Chou, M. S.↗
NASA NTRS1979

Bi-directional four quadrant (BDQ4) power converter development

The feasibility for implementation of a concept for direct ac/dc multikilowatt power conversion with bidirectional transfer of energy was investigated. A 10 kHz current carrier was derived directly from a common 60 Hz three phase power system. This carrier was modulated to remove the 360 Hz ripple, inherent in the three phase power supply and then demodulated and processed by a high frequency filter. The resulting dc power was then supplied to a load. The process was implemented without the use of low frequency transformers and filters. This power conversion processes was reversible and can operate in the four quadrants as viewed from any of the two of the converter's ports. Areas of application include: power systems on air and spacecraft; terrestrial traction; integration of solar and wind powered systems with utility networks; HVDC; asynchronous coupling of polyphase networks; heat treatment; industrial machine drives; and power supplies for any use including instrumentation.

Schwarz, F. C.↗
NASA NTRS1980

Grid and metric generation on the assembly of locally bi-quadratic coordinate transformations

The generation of metric coefficients of the coordinate transformation from a generally curved-sided domain boundary to the unit square (cube) is required for efficient solution algorithms in computational fluid mechanics. An algebraic procedure is presented for establishment of these data on the union of arbitrarily selected sub-domains of the global solution domain. A uniformly smooth progression of grid refinement is readily generated, including multiple specification of refined grids for a given macro-element domain discretization. The procedure is illustrated as generally applicable to non-simply connected domains in two and three dimensions.

Baker, A. J.↗
NASA NTRS1982

Dynamics of bi-periodic structures

In order to gain insight into the dynamics of biperiodic aerospace structures, a variety of one- and two-dimensional biperiodic structures are considered. It is shown that bands in which natural frequencies lie for periodic structures are further subdivided as a consequence of the biperiodicity. Analytical solutions for the modes and frequencies of finite-length one-dimensional biperiodic structures are obtained for general boundary conditions. A transmission method is developed to simplify the application of boundary conditions. Some modes are found to occur at frequencies outside the frequency bands predicted for biperiodic structures. Two-dimensional biperiodic crossed beam grillage and truss structures are considered in the present study.

Mcdaniel, T. J.↗