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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Ride quality assessment. III - Questionnaire results of a second flight programme

A questionnaire was completed by 861 passengers on regularly-scheduled flights of four commuter airlines. Four types of aircraft were involved. Questions assessed major demographic variables, attitudes toward flying, frequency of flying, experience of airsickness, and passenger perceptions of detailed aspects of the physical environment. Passengers also rated their overall comfort level and their willingness to fly again. Passengers perceive motion, noise, and seat factors as the primary determinants of their comfort. Rated comfort is strongly related to willingness to fly again. Incidence of airsickness was low. Sex differences in reactions to aspects of the environment were found.

Richards, L. G.↗
NASA NTRS1977

The correlation function for density perturbations in an expanding universe. I - Linear theory

The evolution of the two-point correlation function for adiabatic density perturbations in the early universe is studied. Analytical solutions are obtained for the evolution of linearized spherically symmetric adiabatic density perturbations and the two-point correlation function for these perturbations in the radiation-dominated portion of the early universe. The results are then extended to the regime after decoupling. It is found that: (1) adiabatic spherically symmetric perturbations comparable in scale with the maximum Jeans length would survive the radiation-dominated regime; (2) irregular fluctuations are smoothed out up to the scale of the maximum Jeans length in the radiation era, but regular fluctuations might survive on smaller scales; (3) in general, the only surviving structures for irregularly shaped adiabatic density perturbations of arbitrary but finite scale in the radiation regime are the size of or larger than the maximum Jeans length in that regime; (4) infinite plane waves with a wavelength smaller than the maximum Jeans length but larger than the critical dissipative damping scale could survive the radiation regime; and (5) black holes would also survive the radiation regime and might accrete sufficient mass after decoupling to nucleate the formation of galaxies.

Mcclelland, J.↗
NASA NTRS1977

Nevada Test Site craters used for astronaut training

Craters produced by chemical and nuclear explosives at the Nevada Test Site were used to train astronauts before their lunar missions. The craters have characteristics suitable for reconnaissance-type field investigations. The Schooner test produced a crater about 300 m across and excavated more than 72 m of stratigraphic section deposited in a fairly regular fashion so that systematic observations yield systematic results. Other features common on the moon, such as secondary craters and glass-coated rocks, are present at Schooner crater. Smaller explosive tests on Buckboard Mesa excavated rocks from three horizontal alteration zones within basalt flows so that the original sequence of the zones could be determined. One crater illustrated the characteristics of craters formed across vertical boundaries between rock units. Although the exercises at the Nevada Test Site were only a small part of the training of the astronauts, voice transcripts of Apollo missions 14, 16, and 17 show that the exercises contributed to astronaut performance on the moon.

Moore, H. J.↗
NASA NTRS1977

The Voyager mission photopolarimeter experiment

A general purpose filter photometer/polarimeter capable of measuring the intensity and linear polarization of scattered light at eight wavelengths in the 2350-7500 A spectral region has been adopted for the Voyager mission photopolarimeter experiment. Objectives of the experiment include determination of the vertical atmospheric aerosol distributions for Jupiter, Saturn and Titan, definition of cloud micro- and macro-structures, and identification of any regular crystalline particles in the clouds. In addition, the density of the satellite atmospheres will be assessed, and the sodium vapor distributions near Io and in the Jovian magnetosphere will be mapped. Particle size and optical depth of Saturn's rings will also be investigated.

Lillie, C. F.↗
NASA NTRS1978

A relation between the Lagrangian and Eulerian turbulent velocity autocorrelations

Direct computation of the Lagrangian autocorrelation is not feasible since generally one cannot measure the turbulent velocity of each fluid particle. A model whereby the Lagrangian autocorrelation is determined in terms of a domain integral of a set of regular Eulerian autocorrelations is advanced. The Eulerian autocorrelations are to be acquired concurrently at all positions in the flow field. Three novel averaging procedures are utilized for obtaining the relationship between the Lagrangian and Eulerian autocorrelations. This relationship is not constrained to either homogeneous or isotropic turbulence.

Koper, C. A., Jr.↗
NASA NTRS1977

Stabilization of Kepler's problem

A regularization of Kepler's problem due to Moser (1970) is used to stabilize the equations of motion. In other words, a particular solution of Kepler's problem is imbedded in a Liapunov stable system. Perturbations can be introduced into the stabilized equations.

Stokes, A.↗
NASA NTRS1978

A double shooting scheme for certain unstable and singular boundary value problems

A scheme is presented to obtain the unique bounded solution for an exponentially unstable linear system. The scheme consists of choosing random data at large initial values and integrating forwards and backwards until accurate regular boundary values are obtained. Proofs of convergence are given for the case that the homogeneous equation has an exponential dichotomy. Applications to other types of problems are discussed and numerical results are presented.

Bayliss, A.↗
NASA NTRS1977

Recursive analytical solution describing artificial satellite motion perturbed by an arbitrary number of zonal terms

An analytical first order solution has been developed which describes the motion of an artificial satellite perturbed by an arbitrary number of zonal harmonics of the geopotential. A set of recursive relations for the solution, which was deduced from recursive relations of the geopotential, was derived. The method of solution is based on Von-Zeipel's technique applied to a canonical set of two-body elements in the extended phase space which incorporates the true anomaly as a canonical element. The elements are of Poincare type, that is, they are regular for vanishing eccentricities and inclinations. Numerical results show that this solution is accurate to within a few meters after 500 revolutions.

Mueller, A. C.↗
NASA NTRS1978

Rotation period of comet Donati

Consideration is given to the rotation period of comet Donati (1858 VI) whose haloes were approximate parabolic envelopes having foci near the apparent nucleus and vertices toward the sun forward from the tail axis. The regularity and sharpness of the halves suggest that they represent the repetitive ejection of material from an active area which is exposed to solar radiation as the cometary nucleus rotates. Bobrovnikov's results (1954) are used to evaluate the linear expansion velocity of such haloes. This calculation is applied to the comet and a linear correction is used to assess the results.

Whipple, F. L.↗
NASA NTRS1975

Size and modal analyses of fines and ultrafines from some Apollo 17 samples

Scanning electron and optical microscopy techniques have been used to determine the grain-size frequency distributions and morphology-based modal analyses of fine and ultrafine fractions of some Apollo 17 regolith samples. There are significant and large differences between the grain-size frequency distributions of the less than 10-micron size fraction of Apollo 17 samples, but there are no clear relations to the local geologic setting from which individual samples have been collected. This may be due to effective lateral mixing of regolith particles in this size range by micrometeoroid impacts. None of the properties of the frequency distributions support the idea of selective transport of any fine grain-size fraction, as has been proposed by other workers. All of the particle types found in the coarser size fractions also occur in the less than 10-micron particles. In the size range from 105 to 10 microns there is a strong tendency for the percentage of regularly shaped glass to increase as the graphic mean grain size of the less than 1-mm size fraction decreases, both probably being controlled by exposure age.

Greene, G. M.↗
NASA NTRS1978

Ride quality evaluation. IV - Models of subjective reaction to aircraft motion

The paper examines models of human reaction to the motions typically experienced on short-haul aircraft flights. Data are taken on the regularly scheduled flights of four commercial airlines - three airplanes and one helicopter. The data base consists of: (1) a series of motion recordings distributed over each flight, each including all six degrees of freedom of motion; temperature, pressure, and noise are also recorded; (2) ratings of perceived comfort and satisfaction from the passengers on each flight; (3) moment-by-moment comfort ratings from a test subject assigned to each airplane; and (4) overall comfort ratings for each flight from the test subjects. Regression models are obtained for prediction of rated comfort from rms values for six degrees of freedom of motion. It is shown that the model C = 2.1 + 17.1 T + 17.2 V (T = transverse acceleration, V = vertical acceleration) gives a good fit to the airplane data but is less acceptable for the helicopter data.

Jacobson, I. D.↗
NASA NTRS1980

A simple self-sealing plug

Inexpensive self-expanding plug makes convenient low-pressure seal. Simple elastomeric plug seals round ports and holes better than regular cork. Plug is inserted with plastic tool that squeezes it to diameter smaller than port opening. Once tool is removed, plug self-expands to its original shape, exerting stronger pressure to sealed surface than cork. Plug is less expensive to make than screw-on or cam-expanded seals.

Ruppe, E. P.↗
NASA NTRS1978

Significance of dual polarized long wavelength radar for terrain analysis

Long wavelength systems with improved penetration capability have been considered to have the potential for minimizing the vegetation contribution and enhancing the surface return variations. L-band imagery of the Arkansas geologic test site provides confirmatory evidence of this effect. However, the increased wavelength increases the sensitivity to larger scale structure at relatively small incidence angles. The regularity of agricultural and urban scenes provides large components in the low frequency-large scale portion of the roughness spectrum that are highly sensitive to orientation. The addition of a cross polarized channel is shown to enable the interpreter to distinguish vegetation and orientational perturbations in the surface return.

Macdonald, H. C.↗
NASA NTRS1977

Radiometric correction of LANDSAT data

The author has identified the following significant results. The six independent sensors of the multispectral band scanner are supposed to be identical; however, in actual practice, they may have different gain settings and offset factors, which result in the effect known as stripping (black lines at regular intervals) of the imagery. A simple two parameter method to correct the gain settings and offset factors of each of the sensors with respect to one sensor, taken as reference, was developed. This method assumes: (1) the response of a detector varies linearly with the radiance of radiation received, and (2) the means, as well as the standard deviations, of a reasonably large number of pixels, in a given wavelength band, are equal for each of the detectors for the radiometrically corrected data.

Dejesusparada, N.↗
NASA NTRS1978

Rocket ozone sounding network data

During the period December 1976 through February 1977, three regular monthly ozone profiles were measured at Wallops Flight Center, two special soundings were taken at Antigua, West Indies, and at the Churchill Research Range, monthly activities were initiated to establish stratospheric ozone climatology. This report presents the data results and flight profiles for the period covered.

Wright, D. U.↗
NASA NTRS1978

A singularity free analytical solution of artificial satellite motion with drag

An analytical satellite theory based on the regular, canonical Poincare-Similar (PS phi) elements is described along with an accurate density model which can be implemented into the drag theory. A computationally efficient manner in which to expand the equations of motion into a fourier series is discussed.

Mueller, A.↗
NASA NTRS1978

Specialized physiological studies in support of manned space flight

The effects of a diuretic (Lasix) induced dehydration on the cardiovascular and hematological responses to lower body negative pressure (LBNP) were analyzed and compared to previous observations on dehydration following exercise in the heat. During LBNP runs the subjects were monitored for changes in blood volume, heart rate, blood pressure, and variations in the volume of the left calf. It was concluded that Lasix dehydration produced a depletion of the body electrolytes at the expense of both the plasma and extravascular compartments. Striking differences were found between those subjects who were physically active (Runners: R) and those who did not engage in any regular physical activity (Non-runners: NR). Tolerance to LBNP (Torr x min) was significantly lower in the R's than the NR's before and after dehydration, however the R's lost more of their tolerance after dehydration with Lasix than after exercise in the heat for about the same fluid loss. The opposite was true for the NR's. Two factors appear to be responsible for the lower LBNP tolerance in R's: parasympathetic inhibition of cardiac activity during LBNP and a greater propensity to pool blood in the lower extremities.

Luft, U. C.↗