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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Characteristics of response factors of coaxial gaseous rocket injectors

The results of an experimental investigation undertaken to determine the frequency dependence of the response factors of various gaseous propellant rocket injectors subject to axial instabilities are presented. The injector response factors were determined, using the modified impedance-tube technique, under cold-flow conditions simulating those observed in unstable rocket motors. The tested injectors included a gaseous-fuel injector element, a gaseous-oxidizer injector element and a coaxial injector with both fuel and oxidizer elements. Emphasis was given to the determination of the dependence of the injector response factor upon the open-area ratio of the injector, the length of the injector orifice, and the pressure drop across the injector orifices. The measured data are shown to be in reasonable agreement with the corresponding injector response factor data predicted by the Feiler and Heidmann model.

Janardan, B. A.↗
NASA NTRS1975

A Theoretical Investigation of the Input Characteristics of a Rectangular Cavity-Backed Slot Antenna

Equations which represent the magnetic and electric stored energies are derived for an infinite section of rectangular waveguide and a rectangular cavity. These representations which are referred to as being physically observable are obtained by considering the difference in the volume integrals appearing in the complex Poynting theorem. It is shown that the physically observable stored energies are determined by the field components that vanish in a reference plane outside the aperture. These physically observable representations are used to compute the input admittance of a rectangular cavity-backed slot antenna in which a single propagating wave is assumed to exist in the cavity. The slot is excited by a voltage source connected across its center; a sinusoidal distribution is assumed in the slot. Input-admittance calculations are compared with measured data. In addition, input-admittance curves as a function of electrical slot length are presented for several size cavities. For the rectangular cavity backed slot antenna, the quality factor and relative bandwidth were computed independently by using these energy relationships. It is shown that the asymptotic relationship which is usually assumed to exist between the quality bandwidth and the reciprocal of relative bandwidth is equally valid for the rectangular cavity backed slot antenna.

Cockrell, C. R.↗
NASA NTRS1975

Engineering models of the Mars atmosphere

Engineering models of the Mars atmosphere are presented for use in spacecraft design and mission planning. The models are developed from (1) data measured by the U.S. Mariner 4, 6, 7, and 9 and USSR Mars 2 and 3 spacecraft, (2) earth-based measurements, and (3) theory which best satisfies the observations. The models include a nominal model for a clear atmosphere, a model for a dusty atmosphere, and models that encompass reasonable extremes of exospheric temperature. In addition to the basic engineering models, other atmospheric characteristics affecting the models are discussed including clouds, ionosphere and atmospheric dynamics.

Noll, R. B.↗
NASA NTRS1975

Instrumented personal exercise during long-duration space flights

The present work reports the results of instrumented personal exercise performed in flight by Skylab 3 and 4 crewmen. Inflight cycle ergometer data provide conclusive evidence that man can perform earthbound equivalent maximum levels of physical work while in the zero-G environment. Moreover, SL4 crewmen were able to improve their physical condition during 84 days of space flight relative to launch condition, due to rigorous personal exercise regimens. Biological data measured included oxygen consumption, CO2 production, minute volume, and heart rate.

Sawin, C. F.↗
NASA NTRS1975

Energy dependence of the Si/Fe ratio in the galactic cosmic rays

New measurements are reported of the Si/Fe ratio and the differential energy spectra of galactic cosmic-ray Si and Fe, taking into account the energy range from 35 MeV to 4 GeV per nucleon. The measured data were obtained with the aid of satellite and balloon-borne instrumentation. It is found that for the region below 1 GeV per nucleon the local interstellar spectra computed are consistent with previous galactic cosmic-ray propagation models obtained by Shapiro and Silberberg (1970) and Mason (1972).

Garcia-Munoz, M.↗
NASA NTRS1974

Autonomous target relative navigation

The present work outlines eight candidate navigation systems for autonomous target relative navigation near a comet, asteroid, or planet. An analytic model is developed for each system, showing how the solution of the relative state vector is obtained from measurement data.

Brock, H. I.↗
NASA NTRS1975

Production of CO /a3 Pi/ in a mercury discharge

The vibrational intensity distribution of CO (a3 Pi - X1 Sigma+) Cameron bands was measured. Data combined from the present and from previous experiments suggest that a3 Pi vibrational temperatures are more characteristic of the parent molecule than are the details of the excitation mechanism. The temperatures were obtained using Franck-Condon factors to deconvolute the bands at 194, 199, and 206 nm. The values were 4800 K for CO2 and 1900 K for CO.

Monahan, K. M.↗
NASA NTRS1974

The Space Shuttle and other atmospheric chlorine sources

The present work reviews the current state of knowledge regarding the contribution from all sources, both natural and anthropogenic, of HCl in the troposphere and in the stratosphere. Some recent estimates on the number of grams per year from each source are presented, and assumptions made in obtaining these figures are discussed. The present lack of measurement data regarding gaseous chlorine compounds in the atmosphere is pointed out.

R. J. Cicerone↗
NASA NTRS1974

A computational procedure to analyze metal matrix laminates with nonlinear lamination residual strains

An approximate computational procedure is described for the analysis of angleplied laminates with residual nonlinear strains. The procedure consists of a combination of linear composite mechanics and incremental linear laminate theory. The procedure accounts for initial nonlinear strains, unloading, and in-situ matrix orthrotropic nonlinear behavior. The results obtained in applying the procedure to boron/aluminum angleplied laminates show that this is a convenient means to accurately predict the initial tangent properties of angleplied laminates in which the matrix has been strained nonlinearly by the lamination residual stresses. The procedure predicted initial tangent properties results which were in good agreement with measured data obtained from boron/aluminum angleplied laminates.

Chamis, C. C.↗
NASA NTRS1975

Performance of a solar-thermal collector

Possible means of achieving the technology required for field application of solar thermal power systems are discussed. Simplifications in construction techniques as well as in measurement techniques for parabolic trough collectors are described. Actual measurement data is also given.

Higa, W. H.↗
NASA NTRS1975

Combined-load stress-strain relationship for advanced fiber composites

It was demonstrated experimentally that only one test specimen is required to determine the combined-load stress-strain relationships of a given fiber composite system. These relationships were determined using a thin angle-plied laminate tube and subjecting it to a number of combined-loading conditions. The measured data obtained are compared with theoretical predictions. Some important considerations associated with such a test are identified, and the significance of combined-load stress-strain relationships in certain practical designs are discussed.

Chamis, C. C.↗
NASA NTRS1975

STOL aircraft transient ground effects. Part 2: Experimental techniques feasibility study

Procedures for simulating transient effects associated with STOL aircraft landings and takeoffs were examined and a basis was developed for selection of an experimental approach based on consideration of simulation requirements, experimental techniques, facilities, and costs. The results are generally applicable to STOL aircraft employing any of the following powered lift systems: externally blown flap, upper surface blown flap, augmentor wing, or internally ducted jet flap. Scaling relationships were developed to apply the simulation requirements to model test situations. Procedures for the derivation of aerodynamic forces from the measured data were discussed. Various means of expressing the aerodynamic data in forms convenient for use in performance or stability and control applications were described. Five different experimental techniques were presented that depend on two different types of experimental facilities, wind tunnels and test tracks, and involving different types of model motion, and factors pertinent to selection were summarized.

Crowder, J. P.↗
NASA NTRS1976

Free vibrations of the ERDA-NASA 100 kW wind turbine

The ERDA-NASA wind turbine (windmill), which consists of a 93-foot truss tower, a bed plate that supports mechanical and electrical equipment, and two 62.5-foot long blades, was analyzed to determine its free vibrations using NASTRAN. The finite element representation of the system consisted of beam and plate elements. The free vibrations of the tower alone, the blades alone, and the complete system were determined experimentally in the field. These results were obtained by instrumenting the tower or blades with an accelerometer and impacting the components with an instrumented mass. The predicted results for natural frequencies and mode shapes were in excellent agreement with measured data.

Chamis, C. C.↗
NASA NTRS1976

Blade row dynamic digital compressor program. Volume 1: J85 clean inlet flow and parallel compressor models

The results are presented of a one-dimensional dynamic digital blade row compressor model study of a J85-13 engine operating with uniform and with circumferentially distorted inlet flow. Details of the geometry and the derived blade row characteristics used to simulate the clean inlet performance are given. A stability criterion based upon the self developing unsteady internal flows near surge provided an accurate determination of the clean inlet surge line. The basic model was modified to include an arbitrary extent multi-sector parallel compressor configuration for investigating 180 deg 1/rev total pressure, total temperature, and combined total pressure and total temperature distortions. The combined distortions included opposed, coincident, and 90 deg overlapped patterns. The predicted losses in surge pressure ratio matched the measured data trends at all speeds and gave accurate predictions at high corrected speeds where the slope of the speed lines approached the vertical.

Tesch, W. A.↗
NASA NTRS1976

Analytical and experimental studies of an optimum multisegment phased liner noise suppression concept

Results are presented from detailed analytical studies made to define methods for obtaining improved multisegment lining performance by taking advantage of relative placement of each lining segment. Properly phased liner segments reflect and spatially redistribute the incident acoustic energy and thus provide additional attenuation. A mathematical model was developed for rectangular ducts with uniform mean flow. Segmented acoustic fields were represented by duct eigenfunction expansions, and mode-matching was used to ensure continuity of the total field. Parametric studies were performed to identify attenuation mechanisms and define preliminary liner configurations. An optimization procedure was used to determine optimum liner impedance values for a given total lining length, Mach number, and incident modal distribution. Optimal segmented liners are presented and it is shown that, provided the sound source is well-defined and flow environment is known, conventional infinite duct optimum attenuation rates can be improved. To confirm these results, an experimental program was conducted in a laboratory test facility. The measured data are presented in the form of analytical-experimental correlations. Excellent agreement between theory and experiment verifies and substantiates the analytical prediction techniques. The results indicate that phased liners may be of immediate benefit in the development of improved aircraft exhaust duct noise suppressors.

Sawdy, D. T.↗
NASA NTRS1976

Strain buildup and release, earthquake prediction and selection of VLB sites for the margins of the North Pacific

Microearthquake studies of the southern section of the San Andreas fault system were conducted in order to elucidate the role of known but little studied complications in the fault system which could affect the SAFE measurement. Data reduction from microearthquake studies in Baja California, Mexico, was completed. In addition, styles of deformation on the Alpine fault in New Zealand and on the San Andreas fault were compared. Sections of these faults with comparable physical characteristics seem to deform in a similar manner, indicating that deformation style is controlled by certain fundamental relations and will continue in the future. The geology of eastern New Guinea is also discussed. Deformation in the area is proposed to be related to collision of a series of island arcs with central New Guinea, which is part of the Australian continent. Among other unusual properties, eastern New Guinea contains the highest anomaly of the gravimetrically determined geoid based on GEM 6 and surface gravity data.

Scholz, C. H.↗
NASA NTRS1976

Development of modified vibration test criteria for qualifying space vehicle components

The results of the evaluation of two response prediction methods relating to the prediction of structural responses of stiffened shell structures with or without attached components, and subjected to broadband acoustic excitations are presented. The methods under evaluation were the constant mass attenuation method and the impedance ratio method. Example problems were used to illustrate the application procedures of these two methods and to compare their predicted results with the experimentally measured data. It is found that more realistic estimates of the structural response can be obtained by the impedance ratio method.

Chang, K. Y.↗
NASA NTRS1976

DSS 14 operating noise temperature during Helios 1 near-sun tracking

When spacecraft are tracked near the line-of-sight of the sun, the ground antenna sidelobes see the solar noise. The solar noise increases the ground system operating noise temperature and degrades the downlink RF reception performance. At specific antenna azimuthal angles relative to the sun, noise peaks and nulls occur periodically throughout a day's tracking pass due to the quadripod support leg-generated sidelobes. This article documents this effect while tracking Helios 1, illustrates the time of the peaks, and compares the predicted time of the noise temperature peaks with the measured data.

Stelzried, C. T.↗