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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

The elusive tradeoff - Speed vs accuracy in visual discrimination tasks.

Explicit payoffs were used to control pressures for speed and accuracy in experiments seeking tradeoffs for difficult visual discrimination tasks. The experiments involved stimuli on a cathode ray tube display controlled by a PDP-1 computer, with the subjects performing increasingly complex discrimination tasks and their earnings increasing with their performance. Models for discrimination under time pressure are proposed on the basis of the results.

Swensson, R. G.↗
NASA NTRS1973

Smithsonian Astrophysical Observatory's minicomputer vs. the laser

Review of some of the problems encountered in replacing a CDC 6400, that was used for supplying a network of laser tracking stations with predictions, by an 8K Data General 1200 minicomputer with a teletype for I/O. Before the replacement, the predictions were expensive to compute and to transmit, and were clumsy logistically. The achieved improvements are described, along with every step it took to accomplish them, and the incurred costs.

Cherniack, J. R.↗
NASA NTRS1974

Control of skin blood flow, sweating, and heart rate - Role of skin vs. core temperature

A study was conducted to generate quantitative expressions for the influence of core temperature, skin temperature, and the rate of change of skin temperature on sweat rate, skin blood flow, and heart rate. A second goal of the study was to determine whether the use of esophageal temperature rather than the right atrial temperature as a measure of core temperature would lead to different conclusions about the control of measured effector variables.

Wyss, C. R.↗
NASA NTRS1975

Lyman-band fluorescence intensity vs H2 pressure

The fluorescence intensity of the H2 Lyman bands excited by the argon 1066 A line is found to be a linear function of the H2 pressure. The fluorescence from naturally occurring HD is linearly dependent on the HD partial pressure. The experiments described show that these fluorescence intensities can be used to measure the H2 and HD densities below 10 trillion molecules per cu cm.

Inn, E. C. Y.↗
NASA NTRS1975

Computers vs. wind tunnels for aerodynamic flow simulations

It is pointed out that in other fields of computational physics, such as ballistics, celestial mechanics, and neutronics, computations have already displaced experiments as the principal means of obtaining dynamic simulations. In the case of aerodynamic investigations, the complexity of the computational work involved in solving the Navier-Stokes equations is the reason that such investigations rely currently mainly on wind-tunnel testing. However, because of inherent limitations of the wind-tunnel approach and economic considerations, it appears that at some time in the future aerodynamic studies will chiefly rely on computational flow data provided by the computer. Taking into account projected development trends, it is estimated that computers with the required capabilities for a solution of the complete viscous, time-dependent Navier-Stokes equations will be available in the mid-1980s.

Chapman, D. R.↗
NASA NTRS1975

Energetic solar proton vs terrestrially trapped proton fluxes

The relative importance of solar and trapped proton fluxes in the consideration of shielding requirements for geocentric space missions is analyzed. Using models of these particles, their fluences encountered by spacecraft in circular orbits are computed as functions of orbital altitude and inclination, mission duration, threshold energy (10 to 100 MeV), and risk factor (for solar protons only), and ratios of solar-to-trapped fluences are derived. It is shown that solar protons predominate for low-altitude polar and very high-altitude missions, while trapped protons predominate for missions at low and medium altitudes and low inclinations. It is recommended that if the ratio of solar-to-trapped protons falls between 0.1 and 10, both fluences should be considered in planning shielding systems.

King, J. H.↗
NASA NTRS1974

Human vs autonomous control of planetary roving vehicles

Supervisory or semiautonomous control has some compelling advantages over step-by-step human command and verification for the operation of roving vehicles on remote planetary surfaces. There are also disadvantages in relation to the complex system that must be mobilized and the chain of events that must be enacted to conduct a mission. Which of the two control methods is better on technical grounds may not be the deciding factor in its acceptance or rejection. Some of the issues that affect changes in spacecraft design and operation are summarized. To accelerate the movement toward more autonomous machines, it will be necessary to understand and to address the problems that such autonomy will create for other elements of the control system and for the control process.

Whitney, W. M.↗
NASA NTRS1975

Floating vs flying: A propulsion energy comparison

Floating craft are compared to those that fly. Drag/weight for floaters is shown to be proportional to v squared/L, while for flyers it is independent of size and speed. The transportation market will therefore assign airships to lower speeds than airplanes, and will favor large airship sizes. Drag of an airship is shown to be only 11 percent of submarine drag at equal displacement and speed, raising the possibility that airships can compete with some types of ships.

Marbury, F.↗
NASA NTRS1977

Analysis of vector wind change with respect to time for Cape Kennedy, Florida: Wind aloft profile change vs. time, phase 1

Wind vector change with respect to time at Cape Kennedy, Florida, is examined according to the theory of multivariate normality. The joint distribution of the four variables represented by the components of the wind vector at an initial time and after a specified elapsed time is hypothesized to be quadravariate normal; the fourteen statistics of this distribution, calculated from fifteen years of twice daily Rawinsonde data are presented by monthly reference periods for each month from 0 to 27 km. The hypotheses that the wind component changes with respect to time is univariate normal, the joint distribution of wind component changes is bivariate normal, and the modulus of vector wind change is Rayleigh, has been tested by comparison with observed distributions. Statistics of the conditional bivariate normal distributions of vector wind at a future time given the vector wind at an initial time are derived. Wind changes over time periods from one to five hours, calculated from Jimsphere data, are presented.

Adelfang, S. I.↗
NASA NTRS1977

Lateral equilibrium of asymmetrical swept wings - Aileron control vs geometric twist

A static aeroelastic phenomenon unique to an aircraft with asymmetrically swept wings is discussed. A simple formula is derived from the analysis of a highly idealized model. The validity of this formula is examined through the use of a more sophisticated numerical analysis. Among the results of this analysis are the following: aileron settings of a few degrees are sufficient to trim such aircraft in roll-for-g-flight; the use of built-in twist in the form of initial negative dihedral provides an efficient alternative to aileron trim; if the wing is elastically tailored in a proper fashion, it may be possible to design a wing whose elastic deformation under airloads provides a form of self-trim in roll at the cruise q of the aircraft.

Weisshaar, T. A.↗
NASA NTRS1976

Optical vs. electronic enhancement of remote sensing imagery

Basic aspects of remote sensing are considered and a description is provided of the methods which are employed in connection with the optical or electronic enhancement of remote sensing imagery. The advantages and limitations of various image enhancement methods and techniques are evaluated. It is pointed out that optical enhancement methods and techniques are currently superior to electronic ones with respect to spatial resolution and equipment cost considerations. Advantages of electronic procedures, on the other hand, are related to a greater flexibility regarding the presentation of the information as an aid for the interpretation by the image analyst.

Colwell, R. N.↗
NASA NTRS1977

Comparative orthostatic responses - Standing vs. head-up tilt

In both physiologic and clinical studies, standing is often loosely equated with head-up tilt (HUT) although the cardiovascular effects of these variants of orthostasis have not been formally compared, except for heart rate. The effects of HUT and standing were measured noninvasively in male volunteers satisfying identical criteria for age and normal status. In both postures, there were significant increases in heart rate, pre-ejection period, isovolumic contraction time, and the ratio of pre-ejection to ejection period, and significant decreases in ejection period and ejection time index. All of these changes were greater for standing than for tilt. Pulse transmission time changed significantly (-14%) only with tilt. We conclude that head-up tilt and standing are rather comparable but not physiologically identical forms of orthostasis.

Spodick, D. H.↗
NASA NTRS1977

Satellite power system LEO vs GEO assembly issues

A strawman crystal-silicon 5-GW Satellite Power System (SPS) concept formed the basis of a study of construction concepts for building a complete SPS in low earth orbit (LEO) or geosynchronous orbit (GEO). Construction scenarios were evolved, including factory-in-space concepts and operations. Design implications imposed on the SPS satellite as a consequence of in-orbit assembly operations, and related attitude control requirements during assembly in LEO or GEO environments, were also evaluated. Results are presented indicating that complete assembly of an operational SPS in LEO, followed by transport to GEO, does not appear technically desirable. The best mix, however, of LEO versus GEO construction activity remains to be resolved.

Mockovciak, J., Jr.↗
NASA NTRS1978

Evaluation of LANDSAT MSS vs TM simulated data for distinguishing hydrothermal alteration

The LANDSAT Follow-On (LFO) data was simulated to demonstrate the mineral exploration capability of this system for segregating different types of hydrothermal alteration and to compare this capability with that of the existing LANDSAT system. Multispectral data were acquired for several test sites with the Bendix 24-channel MSDS scanner. Contrast enhancements, band ratioing, and principal component transformations were used to process the simulated LFO data for analysis. For Red Mountain, Arizona, the LFO data allowed identification of silicified areas, not identifiable with LANDSAT 1 and 2 data. The improved LFO resolution allowed detection of small silicic outcrops and of a narrow silicified dike. For Cuprite - Ralston, Nevada, the LFO spectral bands allowed discrimination of argillic and opalized altered areas; these could not be spectrally discriminated using LANDSAT 1 and 2 data. Addition of data from the 1.3- and 2.2- micrometer regions allowed better discriminations of hydrothermal alteration types.

Abrams, M. J.↗
NASA NTRS1977

Matrix glass vs. intruded glass in lunar breccia 15286

The viscous flow and crystallization behavior of the matrix composition of breccia 15286 have been determined in the 1159-1307 C and 644-770 C temperature ranges. The Shaw (1972) model and, to a slightly lesser extent, the semiempirical Bottinga and Weill (1972) model describe the variation of viscosity with temperature. The crystal growth rate has been determined over the temperature range 821-1185 C. Time-temperature-transformation, logarithmic cooling, and continuous cooling curves were constructed; a nucleation barrier of 60 kT at a relative undercooling of 0.2 is assumed. It is estimated that the matrix of 15286 breccia cooled at a rate greater than 80 K/min through the glass transition region. The increase in density that occurs when the matrix glass is annealed suggests that the breccia was formed by cooling from the molten state rather than by direct shock-induced transition from crystal to glass. Viscous sintering under continuous cooling and logarithmic cooling conditions is analyzed.

Handwerker, C. A.↗
NASA NTRS1977

A comparison of time-shared vs. batch development of space software

In connection with a study regarding the ground support software development for the Space Shuttle, an investigation was conducted concerning the most suitable software development techniques to be employed. A time-sharing 'trial period' was used to determine whether or not time-sharing would be a cost-effective software development technique for the Ground Based Shuttle system. It was found that time-sharing substantially improved job turnaround and programmer access to the computer for the representative group of ground support programmers. Moreover, this improvement resulted in an estimated saving of over fifty programmer days during the trial period.

Forthofer, M.↗