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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

The response of smoke detectors to pyrolysis and combustion products from aircraft interior materials

The following projects were completed as part of the effort to develop and test economically feasible fire-resistant materials for interior furnishings of aircraft as well as detectors of incipient fires in passenger and cargo compartments: (1) determination of the sensitivity of various contemporary gas and smoke detectors to pyrolysis and combustion products from materials commonly used in aircraft interiors and from materials that may be used in the future, (2) assessment of the environmental limitations to detector sensitivity and reliability. The tests were conducted on three groups of materials by exposure to the following three sources of exposure: radiant and Meeker burner flame, heated coil, and radiant source only. The first test series used radiant heat and flame exposures on easily obtainable test materials. Next, four materials were selected from the first group and exposed to an incandescent coil to provide the conditions for smoldering combustion. Finally, radiant heat exposures were used on advanced materials that are not readily available.

Mckee, R. G.↗
NASA NTRS1975

Interior noise levels of two propeller driven light aircraft

A test program is described with the objective of determining the relationship between aircraft operating conditions and interior noise and of determining the degree to which ground testing can be used in lieu of flight testing for performing interior noise research. Measurements are presented for single and twin engine aircraft for 2 or 4 passengers. It was found that noise levels are strongly influenced by the rotational speed of the engine and propeller. Both the overall noise and low frequency spectra levels were observed to decrease with increasing high speed rpm operation during flight. Comparison of spectra obtained in flight with spectra obtained on the ground suggests that identification of frequency components and relative amplitude of propeller and engine noise sources may be evaluated on stationary aircraft.

Catherines, J. J.↗
NASA NTRS1976

On implementation of the extended interior penalty function

The extended interior penalty function formulation is implemented. A rational method for determining the transition between the interior and extended parts is set forth. The formulation includes a straightforward method for avoiding design points with some negative components, which are physically meaningless in structural analysis. The technique, when extended to problems involving parametric constraints, can facilitate closed form integration of the penalty terms over the most important parts of the parameter interval. The method lends itself well to the use of approximation concepts, such as design variable linking, constraint deletion and Taylor series expansions of response quantities in terms of design variables. Examples demonstrating the algorithm, in the context of planar orthogonal frames subjected to ground motion, are included.

Cassis, J. H.↗
NASA NTRS1976

An approach to the prediction of airplane interior noise

At present there is no well-proven method of calculating airplane interior noise associated with jet and boundary layer sources. In this presentation, statistical energy analysis is used to calculate fuselage skin vibration and interior noise levels, with the sidewall represented as a double-wall system. The results show that, in the case of an unpressurized fuselage, the acoustic transmission is dominated by the non-resonant response of the structure. Extension of the results to include pressurization effects and turbulent boundary layer excitation is discussed, particular emphasis being placed on aerodynamic coincidence.

Wilby, J. F.↗
NASA NTRS1976

Interior structure of Jupiter - Theory of gravity sounding

Using relatively simple interior models and a fourth-order theory of figures, it is found that there are basically two extremes of interior structure which agree with current gravity data. One extreme is a 'solar'-composition envelope with 10 to 15 earth masses of heavy material in a core; the other extreme has nearly uniform 'solar' composition but with approximately an additional 30 earth masses of heavy material distributed essentially uniformly. Thus, Jupiter is not of 'solar' composition. It is shown how additional gravity data and improvement in knowledge of the molecular hydrogen equation of state will permit a significant reduction in the number of possible models.

Hubbard, W. B.↗
NASA NTRS1976

Sources and characteristics of interior noise in general aviation aircraft

A field study has been conducted to examine the interior noise characteristics of a general aviation aircraft. The purposes of the study were to identify the major noise sources and their relative contribution and to establish the noise transmission paths and their relative importance. Tests were performed on an aircraft operating under stationary conditions on the ground. The results show that the interior noise level of light aircraft is dominated by broadband, low frequencies (below 1,000 Hz). Both the propeller and the engine are dominant sources; however, the contribution from the propeller is significantly more than the engine at its fundamental blade passage frequency. The data suggests that the airborne path is more dominant than the structure-borne path in the transmission of broadband, low-frequency noise which apparently results from the exhaust.

Catherines, J. J.↗
NASA NTRS1977

Interior noise analysis and control for light aircraft

This paper describes experimental and analytical studies of the interior noise of twin-engine, propeller-driven, light aircraft. Experimental results indicate that interior noise levels due to propeller noise can be reduced by reduction of engine rpm at constant airspeed (about 3 dB), by synchronization of the twin engines/propellers (up to 12 dB), and by increasing the distances from propeller tip to fuselage. The analytical model described uses modal methods and incorporates the flat-sided geometrical and skin-stringer structural features of light aircraft. Initial results show good agreement with measured noise transmitted into a rectangular box through a flat panel.

Mixson, J. S.↗
NASA NTRS1977

The interior structure of Jupiter (Consequences of Pioneer 10 data)

Models of the Jovian interiors based on theoretical equations of state of hydrogen and helium supported by a few experimental points and on observed parameters such as oblateness, gravitational coefficients, heat emission, magnetic fields, are discussed. The models fall into three categories: (1) those that assume a uniform and rather low H2/He ratio throughout the planet; (2) those in which this ratio is solar and thus higher; and (3) those that take into account the lack of complete miscibility of the two elements in the condensed state. It appears now also that within the limits of error the planet is in a hydrostatic equilibrium. The large heat emission and the need for an efficient source of internal heat are confirmed, but the results do not indicate which one of the various possible mechanisms is favored, although new evolutionary models suggest that the primordial heat may be insufficient. A new red spot has been discovered. Finally, the presence of a highly eccentric and inclined magnetic field poses new problems related to the pattern of internal convection and to the possibility of a north-south asymmetry of the interior. Further analysis of the available data may throw additional light on these questions.

Smoluchowski, R.↗
NASA NTRS1978

Possible flyby measurements of Galilean satellite interior structure

Flyby encounters of the Galilean satellites from a Jupiter orbiter spacecraft could yield information about the second-degree gravity harmonics of these satellites. The expected values of these harmonics have been calculated for a range of plausible interior models in hydrostatic equilibrium. Because the satellites respond to comparable perturbations from rotation and tides, an independent test of hydrostatic equilibrium is feasible. For Io and Ganymede, the expected measurement accuracy from a nominal encounter should make possible an excellent discrimination from the ensemble of interior models. For Europa, a qualitative distinction between near-uniform and centrally condensed models seems feasible. Only for Callisto is the proposed experiment of marginal value.

Hubbard, W. B.↗
NASA NTRS1978

Interior noise studies for general aviation types of aircraft. I - Field studies. II - Laboratory studies

Sources of the interior noise level of typical light aircraft are identified for stationary conditions on the ground and in flight. In addition, the relationship between the exterior near- and far-field noise around an aircraft and the interior noise field is examined. The sound transmission paths of a light aircraft fuselage are investigated, and the relative effectiveness of several components of the fuselage for sound attenuation is assessed. The fuselage furnishes an acoustic attenuation of about 20 dB; windows and metallic areas appear to transmit approximately equal amounts of sound energy.

Jha, S. K.↗
NASA NTRS1979

Shallow moonquakes - Depth, distribution and implications as to the present state of the lunar interior

The observed seismic amplitudes of HFT (high-frequency teleseismic) events do not vary with distance as expected for surface sources, but are consistent with sources in the upper mantle of the moon. Thus, the upper mantle of the moon is the only zone where tectonic stresses deriving from differential thermal contraction and expansion of the lunar interior are presently high enough to cause moonquakes. The distribution of shallow moonquake epicenters suggests a possible correlation with impact basins, implying a lasting tectonic influence of impact basins long after their formation. The finite depths now assigned to these shallow moonquakes necessitate further revision to the seismic structural model of the lunar interior.

Nakamura, Y.↗
NASA NTRS1980

Acceptance and control of aircraft interior noise and vibration

Ride quality criteria for noise, vibration, and their combination in the helicopter cabin environment are discussed. Results are presented of laboratory and field studies of passenger responses to interior noise and vibration during the performance of a listening task and during reverie, as well as to the interaction of noise with multi-frequency and multi-axis vibration. A study of means for reducing helicopter interior noise based on analytical, experimental and flight studies of the near-field noise source characteristics of the aircraft, the transmission of noise through aircraft structures and the attenuation of noise by various noise control treatments is then presented which has resulted in a reduction of 3 dB in helicopter cabin noise. Finally, a model under development to evaluate passenger acceptance of a helicopter noise and vibration environment is indicated which incorporates the observed noise and vibration effects on comfort and is expected to provide insights for more effective noise and vibration control.

Stephens, D. G.↗
NASA NTRS1982

Analytical prediction of the interior noise for cylindrical models of aircraft fuselages for prescribed exterior noise fields. Phase 2: Models for sidewall trim, stiffened structures and cabin acoustics with floor partition

An airplane interior noise prediction model is developed to determine the important parameters associated with sound transmission into the interiors of airplanes, and to identify apropriate noise control methods. Models for stiffened structures, and cabin acoustics with floor partition are developed. Validation studies are undertaken using three test articles: a ring stringer stiffened cylinder, an unstiffened cylinder with floor partition, and ring stringer stiffened cylinder with floor partition and sidewall trim. The noise reductions of the three test articles are computed using the heoretical models and compared to measured values. A statistical analysis of the comparison data indicates that there is no bias in the predictions although a substantial random error exists so that a discrepancy of more than five or six dB can be expected for about one out of three predictions.

Pope, L. D.↗
NASA NTRS1981

Constraints on the origin and interior structure of the major planets

Fitting models to the external gravity field of the major planets (Uranus, Neptune, Jupiter, and Saturn), it is found that certain interior characteristics may be common to all four. For Uranus and Neptune, a model with a central iron-silicate core of approximately four earth masses, an 'ice' layer of H2O, CH4, and NH3 in solar proportions of about 10 earth masses, and an H2-He atmosphere of about 1-2 earth masses gives a good fit to available constraints, including heat flow measurements. Models of Jupiter and Saturn have cores very similar to those of Uranus and Neptune; the H2-He layer, however, is markedly more extensive. Modes of origin that are consistent with these features are discussed. Models of this type predict a considerable enrichment of deuterium relative to primordial solar abundances in Uranus and Neptune. Such enrichment is not observed in Uranus; implications are discussed for interior structure and origin.

Hubbard, W. B.↗
NASA NTRS1980

Predictions of mineral assemblages in planetary interiors

It is shown that mineral compatibilities in the model system CaO-MgO-Al2O3-SiO2 can be applied to deduce the mineral assemblages expected in planetary interiors and their variation with depth. In general, the available estimates of bulk composition of the terrestrial planets suggest that the terrestrial planets can be divided into two groups based on their predicted mineral assemblages. The terrestrial, Venusian, and lunar bulk compositions are expected to display the following sequence of mineral assemblages with increasing pressure: plagioclase lherzolite, spinel lherzolite, and garnet lherzolite. The sequences expected in Martian and Mercurian are different: spinel-plagioclase wehrlite, spinel lherzolite, and spinel-garnet wehrlite. These assemblages have a major influence on the compositions of liquids produced by melting of these planetary interiors, on the solidus temperatures, and thus on the nature of planetary differentiation and the types of magmas extruded at planetary surfaces.

Stolper, E.↗
NASA NTRS1982

Development and validation of preliminary analytical models for aircraft interior noise prediction

Predictions are made of the transmission of sound into an unpressurized and unstiffened cylinder under random and harmonic excitations, in order to validate the preliminary version of an airplane interior noise prediction model which is based on an analysis of the power flow type. The predictions are compared to experimental results, and statistically significant differences between predictions and measurements are found to be primarily due to input data deficiencies. Because the model requires only the value of a simple integral for determining interior spatial coupling, and resonance frequencies to determine frequency coupling, the known dynamics of the fuselage can be utilized without difficulty.

Pope, L. D.↗
NASA NTRS1983

The interiors of the giant planets - 1983

It is noted the even though the current model of Jupiter is still based on certain somewhat vexatious approximations, it appears to satisfy the main observational constraints. Saturn's interior is much better understood today than heretofore, although the quantitative aspects of the role of the miscibility gap in the hydrogen-helium system have not yet been entirely resolved. Considerable attention has been given to the interiors of Uranus and Neptune, and the outstanding question appears to be the location and amount of ice and methane present in their outer layers. It is noted that both the two- and three-layer models are moderately successful. Serious difficulties follow from the considerable uncertainties concerning the rotational periods of both planets. In addition, the estimates of the internal heat fluxes and of the magnetic fields of both planets are not sufficiently certain.

Smoluchowski, R.↗
NASA NTRS1984

Evaluation of ride quality prediction methods for helicopter interior noise and vibration environments

The results of a simulator study conducted to compare and validate various ride quality prediction methods for use in assessing passenger/crew ride comfort within helicopters are presented. Included are results quantifying 35 helicopter pilots discomfort responses to helicopter interior noise and vibration typical of routine flights, assessment of various ride quality metrics including the NASA ride comfort model, and examination of possible criteria approaches. Results of the study indicated that crew discomfort results from a complex interaction between vibration and interior noise. Overall measures such as weighted or unweighted root-mean-square acceleration level and A-weighted noise level were not good predictors of discomfort. Accurate prediction required a metric incorporating the interactive effects of both noise and vibration. The best metric for predicting crew comfort to the combined noise and vibration environment was the NASA discomfort index.

Leatherwood, J. D.↗