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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Ablation and radiation coupled viscous hypersonic shock layers.

Coupled ablator shock layer solutions for the stagnation point are presented for typical hyperbolic entry atmospheric flight conditions. These solutions were obtained by numerically solving the stagnation line shock layer equations and quasi-steady ablator equations. These equations included ablation and radiation coupling within the viscous shock layer, line and continuum radiation for both air and phenolic-nylon ablation species and local thermodynamic equilibrium throughout. The results presented provide a sound basis for understanding many of the processes characteristic of hypersonic shock layer heating.-

Engel, C. D.↗
NASA NTRS1974

Mechanical coupling for high cyclic loading

One-piece cylindrical coupling with ""necked-down'' regions at each end form flexures allowing small misalignments between actuator and load. Coupling has zero backlash, low mass, close spacing between actuator and load, high stiffness in direction of motion, and allowance for misalignments and deflections without causing high side loading on components.

Dustin, M. O.↗
NASA NTRS1974

Design criteria monograph on turbopump shafts and couplings

Monograph reviews and assesses current design practices, and considers all aspects of turbopump system shaft dynamics peculiar to and necessary to shaft and coupling design. Associated components (bearings, housing, etc.) that influence shaft or coupling design are treated to extent necessary to define that influence.

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NASA NTRS1973

Charge-coupled device image sensor study

The design specifications and predicted performance characteristics of a Charge-Coupled Device Area Imager and a Charge-Coupled Device Linear Imager are presented. The Imagers recommended are intended for use in space-borne imaging systems and therefore would meet the requirements for the intended application. A unique overlapping metal electrode structure and a buried channel structure are described. Reasons for the particular imager designs are discussed.

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NASA NTRS1973

Image recording using charge-coupled devices

The principle of charge coupling is reviewed and some performance limitations are discussed. The practicality of a two-dimensional charge-coupled area-imaging device is examined. Of several possible design approaches, a frame transfer approach was chosen for detailed consideration because it has a very simple resolution cell. The results obtained in utilizing the proposed approach are given along with some of the problems detected.

Sequin, C.↗
NASA NTRS1973

Effects of visual reference on adaptation to motion sickness and subjective responses evoked by graded cross-coupled angular accelerations

Three groups of 10 subjects each were exposed to stepwise increments of cross coupled angular accelerations in three visual modes: internal visual reference (IVR), external visual reference (EVR), and vision absent (VA). The subjects in the IVR condition required significantly greater amounts of stimulus exposure to neutralize their illusory subjective reactions. They also suffered a greater loss of well-being and a more marked incidence of motion sickness than did subjects in the EVR and VA conditions. The same 30 subjects were reexposed to the same graded cross coupled stimulation 1 week later. This time, however, all the subjects were tested under only the IVR condition. All three groups showed some positive transfer of adaptation, but only the IVR-IVR combination required significantly fewer head motions to achieve the same level of adaptation on the second occasion. Taken overall, however, the most efficient and least disturbing route to adaptation at the completion of the second test was via the VA-IVR combination.

Reason, J. T.↗
NASA NTRS1974

Some problems in coupling solar activity to meteorological phenomena

The development of a theory of coupling of solar activity to meteorological phenomena has to date foundered on the two difficulties of (1) devising a mechanism that can modify the behavior of the troposphere while employing only a negligible amount of energy compared with the energy necessary to drive the normal meteorological system; and (2) determining how such a mechanism can effectively couple some relevant magnetospheric process into the troposphere in such a way as to influence the weather. A clue to the nature of the interaction between the weather and solar activity might be provided by the fact that most solar activity undergoes a definite 11-year cycle, while meteorological phenomena undergo either no closely correlated variation, or an 11-year variation, or a 22-year variation.

Dessler, A. J.↗
NASA NTRS1974

Mutual coupling in a finite planar array of circular apertures

Equations are presented for the calculation of the interelement mutual coupling in a finite-size planar array of waveguide-fed apertures in an infinite flat conductor. The general mutual admittance expression is evaluated for circular apertures, and the mutual coupling calculations are verified experimentally for two Te-(11) mode excited apertures. Qualitative agreement between calculations for a 183-element array and an infinite array establishes the validity of the finite-array theoretical model.

Bailey, M. C.↗
NASA NTRS1974

Active mode-coupling phenomena in pulsed and continuous lasers

An optical modulator inside a laser cavity, if driven at the cavity c/2L frequency or a harmonic, will produce a variety of mode-coupled short-pulse and FM-laser phenomena. This paper reviews the kinds of CW and transient mode-coupling phenomena that can occur in CW lasers and in selected lower-power pulsed lasers using either an active optical modulator or in some cases passive saturable absorbers.

Siegman, A. E.↗
NASA NTRS1974

Mutual coupling in a finite planar array of circular apertures

Equations are presented for the calculation of the interelement mutual coupling in a finite size planar array of wave-guide-fed apertures in an infinite flat conductor. The general mutual admittance expression is evaluated for circular apertures and the mutual coupling calculations are verified experimentally for two TE11 mode excited apertures. Qualitative agreement between calculations for a 183 element array and an infinite array establishes the validity of the finite array theoretical model.

Bailey, M. C.↗
NASA NTRS1974

Radiation-gas dynamic shock layer coupling

The present work considers theoretically the problem of radiation losses on the shock layer during hypersonic flight, and in particular, results are presented for the stagnation line shock layer for a wide variety of flight conditions, providing a new overview of radiation-gas dynamic coupling within a shock layer. The present results are based on a previous model (Engel, Farmer, et al., 1973) of a viscous radiating shock layer. An important result is that the radiation-gas dynamic coupling effect on the radiative heating can be related to a single parameter, namely, the radiative cooling parameter, whereas the effect on the shock layer thickness is not a simple function of this parameter.

Engel, C. D.↗
NASA NTRS1974

Effect of resonance-oblateness coupling on a satellite orbit

Second order effects of the coupling between geopotential resonance and oblateness on a satellite orbit are calculated. Results show that: (1) these effects arise from the interaction of resonance with the secular changes of the orbit's node, perigee, and mean anomaly; (2) they have the same period and phase as first order resonance perturbations; and (3) their amplitudes are proportional to the square of the period and dominate the first order effects as the orbit becomes commensurate. A striking example of this coupling is seen in the 18 day resonance variation of the node of the orbit of the first earth resources technology satellite. Analysis of this one arc second (31m) variation yielded a strong 14th order constraint to the geopotential for odd degree terms. This constraint is poorly predicted by current models.

Wagner, C. A.↗
NASA NTRS1975

Determination of coupling coefficients at various zenith angles of the basis of the cosmic ray azimuth effect

The value of EW asymmetry and coupling coefficients at different zenith angles were measured by means of a double coincidence crossed telescope which gives an opportunity to measure simultaneously the intensity of the cosmic ray hard component at zenith angles from 0 to 84 deg in opposite azimuths. The advantages of determining the coupling coefficients by the cosmic ray azimuth effect as compared to their measurement by the latitudinal effect are discussed.

Belskiy, S. A.↗
NASA NTRS1975

Digital computer program DF1758 fully coupled natural frequencies and mode shapes of a helicopter rotor blade

The analytical techniques and computer program developed in the fully-coupled rotor vibration study are described. The rotor blade natural frequency and mode shape analysis was implemented in a digital computer program designated DF1758. The program computes collective, cyclic, and scissor modes for a single blade within a specified range of frequency for specified values of rotor RPM and collective angle. The analysis includes effects of blade twist, cg offset from reference axis, and shear center offset from reference axis. Coupled inplane, out-of-plane, and torsional vibrations are considered. Normalized displacements, shear forces and moments may be printed out and Calcomp plots of natural frequencies as a function of rotor RPM may be produced.

Bennett, R. L.↗
NASA NTRS1975

Some problems in coupling solar activity to meteorological phenomena

The development of a theory of coupling of solar activity to meteorological phenomena is hindered by the difficulties of devising a mechanism that can modify the behavior of the troposphere while employing only a negligible amount of energy compared with the energy necessary to drive the normal meteorological system, and determining how such a mechanism can effectively couple some relevant magnetospheric process into the troposphere in such a way as to influence the weather. A clue to the nature of the interaction between the weather and solar activity might be provided by the fact that most solar activity undergoes a definite 11-yr cycle, and meteorological phenomena undergo either no closely correlated variation, an 11-yr variation, or a 22-yr variation.

Dessler, A. J.↗
NASA NTRS1976

Coupled base motion response analysis of payload structural systems

Coupled base motion response analysis of payload structural systems is discussed. A systems analysis program is described which by component analysis structural transient response analyses can be completed. The program presents a proven technique, used initially on the Skylab program, which is designed to reduce cost and schedule time on detail structural analyses of structural payload systems. Base motion procedures are employed where critical segments of complex structural systems or components may be analyzed for various load conditions without having to re-establish the entire structural system coupled model properties. The transient response characteristics of a complex structural system are used as a basis for evaluating the transient response of a similar system.

Devers, A. D.↗
NASA NTRS1976

Long period coupling terms for Lagrange's equations

A generalization of that portion of the work of Berger, which deals with the long period coupling effect of certain pairs of zonal harmonics. Long period terms arising from the short short period coupling of zonal harmonics are derived for Lagrange's equations. The formulation is general so that the results are valid for any pairs of zonal harmonics. Formulas are given to generate the various functions and integrals needed for the results given. Checks have been made against the work of Kozai.

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