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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Development of termination and utilization concepts for flat conductor cables. Volume 3: Cost study comparison, flat versus round conductor cable

A cost study comparing flat conductor cable (FCC) with small-gage wire (SGW) and conventional round conductor cable (RCC) is presented. This study was based on a vehicle wiring system consisting of 110,000 ft of conventional RCC equally divided between AWG sizes 20,22, and 24 using MIL-W-81044-type wire and MIL-C-26500 circular connectors. Basic cost data were developed on a similar-sized commercial jet airplane wiring system on a previous company R&D program in which advanced wiring techniques were carried through equivalent installations on an airplane mockup; and on data developed on typical average bundles during this program. Various cost elements included were engineering labor, operations (manufacturing) labor, material costs, and cost impact on payload. Engineering labor includes design, wiring system integration, wiring diagrams and cable assembly drawings, wire installations, and other related supporting functions such as the electronic data processing for the wiring. Operations labor includes mockup, tooling and production planning, fabrication, assembly, installation, and quality control cost impact on payload is the conversion of wiring system weight variations through use of different wiring concepts to program payload benefits in terms of dollars.

Source record↗
NASA NTRS1968

Preparation of alkali metal dispersions

A method is described for producing alkali metal dispersions of high purity. The dispersions are prepared by varying the equilibrium solubility of the alkali metal in a suitable organic solvent in the presence of aromatic hydrocarbons. The equilibrium variation is produced by temperature change. The size of the particles is controlled by controlling the rate of temperature change.

Rembaum, A.↗
NASA NTRS1978

Low frequency spectra of type III solar radio bursts

Flux density spectra have been determined for 91 simple type III solar bursts observed by the Goddard Space Flight Center radio astronomy experiment on the IMP-6 spacecraft during 1971 and 1972. Spectral peaks were found to occur at frequencies ranging from 44 kHz up to 2500 kHz. Half of the bursts peaked between 250 kHz and 900 kHz, corresponding to emission at solar distances of about 0.3 to 0.1 AU. Maximum burst flux density sometimes exceeds 10 to the -14th W/sq m/Hz. The primary factor controlling the spectral peak frequency of these bursts appears to be a variation in intrinsic power radiated by the source as the exciter moves outward from the sun, rather than radio propagation effects between the source and IMP-6. Thus, a burst spectrum strongly reflects the evolution of the properties of the exciting electron beam, and according to current theory, beam deceleration could help account for the observations.

Weber, R. R.↗
NASA NTRS1980

Preliminary calculations concerning the maintenance of the zonal mean ozone distribution in the Northern Hemisphere

Results from a three-dimensional photochemical-dynamical model of ozone are presented and a qualitative description of the maintenance of the ozone distribution and its seasonal variations below 1 mb is given. The transition between photochemical and transport control of the ozone distribution is emphasized. Between 1 and 10 mb, transport by the eddies seems to play only a minor role at mid-latitudes in producing the observed ozone distribution despite the zero correlation between ozone and temperature which occurs in that region. In the lower stratosphere, mean and eddy contributions to ozone change generally strongly offset one another. The buildup and decay of the springtime ozone maximum is discussed. Emphasis is given to the mechanism of ozone transport by the mid-latitude eddies, which play an important role in the springtime accumulation of ozone.

Cunnold, D. M.↗
NASA NTRS1982

The seasonal and global behavior of water vapor in the Mars atmosphere - Complete global results of the Viking atmospheric water detector experiment

A key question regarding the evolution of Mars is related to the behavior of its volatiles. The present investigation is concerned with the global and seasonal abundances of water vapor in the Mars atmosphere as mapped by the Viking Mars Atmospheric Water Detector (MAWD) instrument for almost 1-1/2 Martian years from June 1976 to April 1979. Attention is given to the implications of the observed variations for determining the relative importance of those processes which may be controlling the vapor cycle on a seasonal basis. The processes considered include buffering of the atmosphere water by a surface or subsurface reservior of ground ice, physically adsorbed water, or chemically bound water. Other processes are related to the supply of water from the residual or seasonal north polar ice cap, the redistribution of the vapor resulting from atmospheric circulation, and control of the vapor holding capacity of the atmosphere by the local atmospheric temperatures.

Jakosky, B. M.↗
NASA NTRS1981

Moisture sounding at millimeter wavelengths /94/183 GHz/ at high altitudes

A moisture sounding radiometer at millimeter wavelengths has been developed for high altitude measurements onboard NASA's WB-57F aircraft. Three channels about the 183.3 GHz water vapor line permit measurement of the atmospheric water vapor profile. A single window channel at 94 GHz provides correction for clouds over the ocean and for surface emissivity variations over land. The instrument is an imaging radiometer operating under microprocessor control throughout each data flight. The system is contained within two packages integrated into the WB-57F pallet. A ground support system was used to perform a quick-look analysis of the data collected immediately following each flight.

Gagliano, J. A.↗
NASA NTRS1983

Ambiguities in spaceborne synthetic aperture radar systems

An examination of aspects of spaceborne SAR time delay and Doppler ambiguities has led to the formulation of an accurate method for the evaluation of the ratio of ambiguity intensities to that of the signal, which has been applied to the nominal SAR system on Seasat. After discussing the variation of this ratio as a function of orbital latitude and attitude control error, it is shown that the detailed range migration-azimuth phase history of an ambiguity is different from that of a signal, so that the images of ambiguities are dispersed. Seasat SAR dispersed images are presented, and their dispersions are eliminated through an adjustment of the processing parameters. A method is also presented which uses a set of multiple pulse repetition sequences to determine the Doppler centroid frequency absolute values for SARs with high carrier frequencies and poor attitude measurements.

Li, F. K.↗
NASA NTRS1984

Advanced laser stratospheric monitoring systems analyses

This report describes the software support supplied by Systems and Applied Sciences Corporation for the study of Advanced Laser Stratospheric Monitoring Systems Analyses under contract No. NAS1-15806. This report discusses improvements to the Langley spectroscopic data base, development of LHS instrument control software and data analyses and validation software. The effect of diurnal variations on the retrieved concentrations of NO, NO2 and C L O from a space and balloon borne measurement platform are discussed along with the selection of optimum IF channels for sensing stratospheric species from space.

Larsen, J. C.↗
NASA NTRS1986

A new design concept for indraft wind-tunnel inlets with application to the National Full-Scale Aerodynamics Complex

The present inlet design concept for an indraft wind tunnel, which is especially suited to applications for which a specific test section flwo quality is required with minimum inlet size, employs a cascade or 'vaneset' to control flow at the inlet plane, so that test section total pressure variation is minimized. Potential flow panel methods, together with empirical pressure loss predictions, are used to predict inlet cascade performance. This concept has been used to develop an alternative inlet design for the 80 x 120-ft wind tunnel at NASA Ames Research Center. Experimental results show that a short length/diameter ratio wind tunnel inlet furnishing atmospheric wind isolation and uniform test section flow can be designed.

Ross, J. C.↗
NASA NTRS1987

Flight investigation of the effect of tail configuration on stall, spin, and recovery characteristics of a low-wing general aviation research airplane

Flight tests were performed to investigate the stall, spin, and recovery characteristics of a low-wing, single-engine, light airplane with four interchangeable tail configurations. The four tail configurations were evaluated for effects of varying mass distribution, center-of-gravity position, and control inputs. The airplane tended to roll-off at the stall. Variations in tail configuration produced spins ranging from 40 deg to 60 deg angle of attack and turn rates of about 145 to 208 deg/sec. Some unrecoverable flat spins were encountered which required use of the airplane spin chute for recovery. For recoverable spins, antispin rudder followed by forward wheel with ailerons centered provided the quickest spin recovery. The moderate spin modes agreed very well with those predicted from spin-tunnel model tests, however, the flat spin was at a lower angle of attack and a slower rotation rate than indicated by the model tests.

Stough, H. Paul, III↗
NASA NTRS1986

A new design concept for indraft wind-tunnel inlets with application to the national full-scale aerodynamic complex

The present inlet design concept for an indraft wind tunnel, which is especially suited to applications for which a specific test section flow quality is required with minimum inlet size, employs a cascade or vaneset to control flow at the inlet plane, so that test section total pressure variation is minimized. Potential flow panel methods, together with empirical pressure loss predictions, are used to predict inlet cascade performance. This concept has been used to develop an alternative inlet design for the 80 x 120-ft wind tunnel at NASA Ames Research Center. Experimental results show that a short length/diameter ratio wind tunnel inlet furnishing atmospheric wind isolation and uniform test section flow can be designed.

Ross, James C.↗
NASA NTRS1990

Robust, High-Performance Control For Robotic Manipulators

Improved control scheme for robotic manipulators results from alternative approach to use of both model-based and performance-based control techniques. Includes feedforward controller and separate feedback controller. Feedforward controller model-based and contains any known part of dynamics of manipulator used to produce nominal control signal. Feedback controller performance-based; compensates for any unknown dynamics and uncertainties or variations in parameters of manipulator and/or payload.

Seraji, Homayoun↗
NASA NTRS1991

Nonlinear compensation techniques for magnetic suspension systems

In aerospace applications, magnetic suspension systems may be required to operate over large variations in air-gap. Thus the nonlinearities inherent in most types of suspensions have a significant effect. Specifically, large variations in operating point may make it difficult to design a linear controller which gives satisfactory stability and performance over a large range of operating points. One way to address this problem is through the use of nonlinear compensation techniques such as feedback linearization. Nonlinear compensators have received limited attention in the magnetic suspension literature. In recent years, progress has been made in the theory of nonlinear control systems, and in the sub-area of feedback linearization. The idea is demonstrated of feedback linearization using a second order suspension system. In the context of the second order suspension, sampling rate issues in the implementation of feedback linearization are examined through simulation.

Trumper, David L.↗
NASA NTRS1986

Process for detecting the likelihood of ice formation, ice warning system for carrying out the process, and utilization thereof

An ice warning system comprising a diaphragm set into vibration at one of its frequencies of resonance by a piezoelectric cell. The diaphragm is coupled thermally to a metallic plate alternately cooled and heated respectively below and above the ambient temperature by Peltier elements connected to a reversible DC current generator. A microprocessor measures any variation of the resonance frequency caused by a deposit of ice on the diaphragm during the cooling or heating periods and delivers an alarm signal if this variation of frequency reaches and/ or exceeds a predetermined value. The microprocessor controls the period, intensity and direction of the current delivered by the DC current generator as a function of the ambient temperature and the temperature of the diaphragm. The ice warning system is preferably utilized in the aeronautical field for indicating the likelihood of natural ice formation on the engines and the wings of aircraft.

Martin Lustenberger↗
NASA NTRS1989

Squint mode SAR processing algorithms

The unique characteristics of a spaceborne SAR (synthetic aperture radar) operating in a squint mode include large range walk and large variation in the Doppler centroid as a function of range. A pointing control technique to reduce the Doppler drift and a new processing algorithm to accommodate large range walk are presented. Simulations of the new algorithm for squint angles up to 20 deg and look angles up to 44 deg for the Earth Observing System (Eos) L-band SAR configuration demonstrate that it is capable of maintaining the resolution broadening within 20 percent and the ISLR within a fraction of a decibel of the theoretical value.

Chang, C. Y.↗
NASA NTRS1990

The seasonality of AVHRR data of temperate coniferous forests - Relationship with leaf area index

The relationship between the advanced very high resolution radiometer (AVHRR) normalized difference vegetation index (NDVI) and coniferous forest leaf area index (LAI) over the western United States is examined. AVHRR data from the NOAA-9 satellite were acquired of the western U.S. from March 1986 to November 1987 and monthly maximum value composites of AVHRR NDVI were calculated for 19 coniferous forest stands in Oregon, Washington, Montana, and California. It is concluded that the relationships under investigation vary according to seasonal changes in surface reflectance based on key biotic and abiotic controls including phenological changes in LAI caused by seasonal temperature and precipitation variations, the proportions of surface cover types contributing to the overall reflectance, and effects resulting from large variations in the solar zenith angle.

Spanner, Michael A.↗
NASA NTRS1991

Advanced air revitalization for optimized crew and plant environments

The Hybrid Air Revitalization System (HARS) closed ecosystem concept presented encompasses electrochemical CO2 and O2 separators, in conjunction with a mechanical condenser/separator for maintaining CO2, O2, and humidity levels in crew and plant habitats at optimal conditions. HARS requires no expendables, and allows flexible process control on the bases of electrochemical cell current, temperature, and airflow rate variations. HARS capacity can be easily increased through the incorporation of additional chemical cells. Detailed system flowcharts are provided.

Lee, M. G.↗
NASA NTRS1992

Medium-frequency impulsive-thrust-excited slosh waves during propellant reorientation with a geyser

Slosh wave excitation induced by a resettling flowfield activated by 1.0-Hz impulsive thrust during the course of liquid reorientation with the initiation of geyser for liquid-fill levels of 30, 50, 65, 70, and 80 percent has been studied. Characteristics of slosh waves of various frequencies excited by the resettling flowfield are discussed. Slosh wave excitations shift the fluid mass distribution in the container which imposes time-dependent variations in spacecraft moment of inertia. This information is important for spacecraft control during the course of liquid reorientation.

Hung, R. J.↗