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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Preparation and analysis of standardized waste samples for Controlled Ecological Life Support Systems (CELSS)

The preparation and analysis of standardized waste samples for controlled ecological life support systems (CELSS) are considered. Analysis of samples from wet oxidation experiments, the development of ion chromatographic techniques utilizing conventional high pressure liquid chromatography (HPLC) equipment, and an investigation of techniques for interfacing an ion chromatograph (IC) with an inductively coupled plasma optical emission spectrometer (ICPOES) are discussed.

Carden, J. L.↗
NASA NTRS1981

Rheological behavior of progressively shear-thickening solutions

The rheological behavior of the recently developed polymer FM-9 in Jet A fuel and JP 8 fuel is reported. In aqueous solution, FM 9 is found to exhibit strong time-dependent shear thickening behavior. Induction time necessary for the onset of thickening is found to depend on shear rate, solvent, concentration, and molecular weight. Altering the nature of the solvent results in effects similar to those obtained by changing the concentration or molecular weight. A critical shear rate is derived, and is inversely proportional to the zero shear rate viscosity of the solution for the temperature and concentrations observed. The onset of shear thickening behavior appears to be related to the onset of viscoelastic response, and thus the time scale follows reduced variable behavior.

Peng, S. T. J.↗
NASA NTRS1981

High performance solar Stirling system

A full-scale Dish-Stirling system experiment, at a power level of 25 kWe, has been tested during 1981 on the Test Bed Concentrator No. 2 at the Parabolic Dish Test Site, Edwards, CA. Test components, designed and developed primarily by industrial contractors for the Department of Energy, include an advanced Stirling engine driving an induction alternator, a directly-coupled solar receiver with a natural gas combustor for hybrid operation and a breadboard control system based on a programmable controller and standard utility substation components. The experiment demonstrated practicality of the solar Stirling application and high system performance into a utility grid. This paper describes the design and its functions, and the test results obtained.

Stearns, J. W.↗
NASA NTRS1981

A PWM transistor inverter for an ac electric vehicle drive

A prototype system consisting of closely integrated motor, inverter, and transaxle has been built in order to demonstrate the feasibility of a three-phase ac transistorized inverter for electric vehicle applications. The microprocessor-controlled inverter employs monolithic power transistors to drive an oil-cooled, three-phase induction traction motor at a peak output power of 30 kW from a 144 V battery pack. Transistor safe switching requirements are discussed, and a circuit is presented for recovering trapped snubber inductor energy at transistor turn-off.

Slicker, J. M.↗
NASA NTRS1981

Eddy current probe response to open and closed surface flaws

A general analysis of eddy current response to certain types of open and closed surface flaws is presented for both standard low-frequency and ferromagnetic-resonance (FMR) probes. It is shown analytically that for two-dimensional and three-dimensional surface flaws interrogated by a uniform probe field, the crack opening sensitivity increases with the operating frequency of the probe, this behavior being due to the Faraday induction effect. Experiments with low-frequency probes operating at or below 1 MHz and with the FMR probe operating at approximately 1000 MHz confirm this increase of the crack mouth opening displacement for practical situations where the probe field is not uniform in the vicinity of the flaw.

Auld, B. A.↗
NASA NTRS1982

Impulsive plasma transport through the magnetopause

The considered investigation is concerned with a study of the process of localized plasma entry on the basis of first principles. Since the magnetopause often moves at high velocities, an induction electric field must be involved. Attention is given to the case in which the adjacent magnetopause is at rest. Occasionally, a frame moving with the magnetopause in the interaction region is also considered. The employed model is based on the observations provided by ISEE. The considered plasma irregularity, which is denominated a 'cloud', may not have to be a large enhancement in number density or velocity. An examination of the involved physical relations shows that the plasma will create its own electric field, via a polarization current, to make possible a penetration through the magnetopause by the cloud. At the magnetopause the polarization current creates a charge separation electric field which promotes (rather than inhibits) continued flow through the moving magnetopause.

Heikkila, W. J.↗
NASA NTRS1982

Conditioned feeding suppression in rats produced by cross-coupled and simple motions

Results are presented of an experiment on the induction of motion sickness in rats by the use of cross-coupled accelerations of magnitudes similar to those used in human experiments. Accelerations were produced in a seesaw apparatus with rotating disks supporting the animal cages mounted on each seesaw arm, and motion sickness was assessed according to the consumption of a sweet food previously offered to the animals immediately before the motion treatment. During a 1-hour test session 72 h after motion treatment and after a 24-h fast, rats having undergone cross-coupled vertical sinusoidal and rotational motion are observed to consume less food than those having experienced either type of motion alone, or no motion. The ordering of the conditioned suppressive feeding effects is consistent with the amounts of vestibular stimulation produced by the respective motions. The results support the existence of motion sickness effects in rats, even though they are unable to vomit.

Fox, R. A.↗
NASA NTRS1982

The 22-year solar cycle - A heliospheric oscillation

A new mechanism is proposed for the origin of the 22-year solar cycle in which the solar cycle is caused by a large scale oscillation of the heliosphere. In its simplest terms the oscillation is directly analogous to an LC oscillator, with the heliospheric current system providing the inductance, and accumulated charge near the heliosphere boundary providing the capacitance. Estimates of the oscillation period using reasonable parameters are close to 22 years.

Gurnett, D. A.↗
NASA NTRS1982

Double layer formation during current sheet disruptions in a reconnection experiment

When the current density in the center of a neutral sheet is increased to a critical value spontaneous current disruptions are observed. The release of stored magnetic field energy results in a large inductive voltage pulse which drops off inside the plasma in the form of a potential double layer. Particles are energized, microinstabilities are generated, the plasma is thinned, and the current flow is redirected. These laboratory observations qualitatively support recent models of magnetic substorms and solar flares.

Stenzel, R. L.↗
NASA NTRS1981

Recent developments in mass drivers

In the past eight months a new mass driver concept has been explored through calculation and inductance model verification. It retains the linear synchronous principle and freedom from arcs, plasmas or physical contact between the accelerated bucket and accelerator. However, it discards passive magnetic flight and obtains transverse focussing from strong off-axis restoring forces produced by drive coils operating in a pull-only mode. This paper gives the reasoning on which the new concept is based, and applies the concept to a lunar catapult design.

Oneill, G. K.↗
NASA NTRS1982

Double layer formation

An investigation is conducted of the plasma processes which occur during the formation of a double layer in response to an applied initial electric field, when triggered by a current in the plasma. The important feature of the formation process was the creation of an ion-rich plasma-density cavity. The positive space charge of the cavity was shielded by induction of a negative space charge on the low potential side of the cavity, giving rise to the formation of a fully developed double layer. The shielding was complete only when the electron current from the low potential side exceeded the electron thermal current. It was found that during the formation of double layers counterstreaming electrons are generated. Moreover, transient double layers with reverse polarity also occur during this phase. Thus, the recurring formation of double layers can give rise to flickering double layers.

Singh, N.↗
NASA NTRS1982

The deep lunar electrical conductivity profile - Structural and thermal inferences

Simultaneous lunar surface and orbital magnetometer records are reexamined, to ascertain intervals which may be suitable for measuring lunar inductive response in the solar wind and terrestrial magnetosheath. Power spectral estimates of the response tangent to the lunar surface, defined in terms of transfer and gain functions, are obtained for the 0.0001-0.01 Hz frequency range. The maximum consistency of estimates from different time intervals is found when the initial analysis is limited to the tangential direction of maximum incident power, or that direction in which the ratio of signal to background noise is greatest. Spherically symmetric plasma confinement theory is used in the interpretation of transfer function data, by way of forward model calculations, under the assumption of continuous electrical conductivity increase with depth. Results are presented for internal electrical conductivity profile, metallic core radius, and selenotherm limits.

Hood, L. L.↗
NASA NTRS1982

Effect of physical training in cool and hot environments on +Gz acceleration tolerance in women

Acceleration tolerance, plasma volume, and maximal oxygen uptake were measured in 15 healthy women before and after submaximal isotonic exercise training periods in cool and hot environments. The women were divided on the basis of age, maximal oxygen uptake, and +Gz tolerance into three groups: a group that exercised in heat (40.6 C), a group that exercised at a lower temperature (18.7 C), and a sedentary control group that functioned in the cool environment. There was no significant change in the +Gz tolerance in any group after training, and terminal heart rates were similar within each group. It is concluded that induction of moderate acclimation responses without increases in sweat rate or resting plasma volume has no influence on +Gz acceleration tolerance in women.

Brock, P. J.↗
NASA NTRS1982

A new rat model for studies of hypokinesia and antiorthostasis

A new rat model (suspension and immobilization) is described for induction of hypokinesia and orthostatic manipulations. Hypokinetic responses were comparable to those in prolonged bed rest and weightlessness in humans, body or limb casted and small cage restrained animals. Responses to antiorthostasis (15 to 20 deg head down tilt) in rats were similar to those in neutral bouyancy tests in humans and animals and to those in prolonged bed rest in humans. During seven days of hypokinesia there was an atrophy of the gastrocnemius and increased excretion of urinary nitrogeneous end products. The antiorthostatic (AOH) 15 to 20 deg head down tilt resulted in diuresis, natriuresis and kaliuresis. No comparable responses were observed in orthostatic hypokinetic (OH) rats. Readaptation from AOH and OH occurred during one week recovery in metabolic cage conditions.

Musacchia, X. J.↗
NASA NTRS1982

Suppression of osteoblast differentiation during weightlessness

It is pointed out that associated with weightlessness is a marked depression or arrest of bone formation. Although the mechanism of this effect is unknown, it probably involves a failure of osteogenic induction. The present study's objective is to determine if weightlessness alters osteoblast differentiation, as evidenced by a change in relative distribution of large to small nuclei in rat moral periodontal ligament of the maxilla. In conjunction with the U.S./USSR Biological Satellite Program, male Wistar rats were flown aboard a modified Soviet Vostok spacecraft (Cosmos 1129). The results of the study are discussed. Morphometric investigations suggest that depleted numbers of preosteoblasts may be an important factor in the inhibition of bone formation during weightlessness.

Roberts, W. E.↗
NASA NTRS1984

Band-Pass Amplifier Without Discrete Reactance Elements

Inherent or "natural" device capacitance exploited. Band-Pass Circuit has input impedance of equivalent circuit at frequencies much greater than operational-amplifier rolloff frequency. Apparent inductance and capacitance arise from combined effects of feedback and reactive component of amplifier gain in frequency range.

Kleinberg, L.↗
NASA NTRS1982

Preparation of low strategic metal content superalloys

The properties of modified NIMONIC 115 and UDIMET 720 with reduced levels of cobalt were evaluated. Vacuum induction melted and vacuum arc remelted ingots were hot rolled to 3/4 inch diameter bar. Hot workability was evaluated in terms of the ingot rolling behavior and the hot ductility of the as-rolled bar. Variations in workability and bar ductility were correlated to variations in incipient melting temperature and gamma prime solvus, both of which varied with cobalt content. Heat treatments were defined to yield, as far as possible, similar structures from alloy to alloy. At the lowest cobalt levels N-115 workability was severely limited and the alloys could not be worked to bar. It is suggested that incipient melting in combination with heavy grain boundary carbide precipitation reduced ingot workability. Final heat treatment of modified alloys was difficult in the situation where the gamma prime solvus temperature was close to the incipient melting point, indicating that it may not be feasible to fully solution low cobalt alloys to obtain the large grain size required for optimum creep resistance.

Sczerzenie, F. E.↗
NASA NTRS1982

Advances in core loss calculations for magnetic materials

A new analytical technique which predicts the basic magnetic properties under various operating conditions encountered in state-of-the-art dc-ac/dc converters is discussed. Using a new flux-controlled core excitation circuit, magnetic core characteristics were developed for constant values of ramp flux (square wave voltage excitation) and frequency. From this empirical data, a mathematical loss characteristics equation is developed to analytically predict the specific core loss of several magnetic materials under various waveform excitation conditions. In addition, these characteristics show the circuit designer for the first time the direct functional relatonships between induction level and specific core loss as a function of the two key dc-dc converter operating parameters of input voltage and duty cycle.

Triner, J. E.↗