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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Stimulation of cardiovascular adaptability during prolonged space exposure

The deconditioning effects of weightlessness on the cardiovascular system of astronauts are discussed. It is believed that man cannot tolerate indefinite exposure to weightlessness without considerable circulatory deterioration. Analyses of data collected from space flights to date substantiate these beliefs, and confirm the fact that some form of compensation must be provided to keep the cardiovascular system of space travelers properly conditioned. Sequential pulsatile devices were investigated to produce periodic hydrostatic pressure gradients in the venous system of eight subhuman primates. Intermittent venous pooling of blood in the extremities triggers and stimulates the vascular reflex mechanisms of the cardiovascular system that may have significant benefits in maintaining the circulatory system in proper tone under weightless conditions. Electrocardiograms, blood pressure measurements, cardiac output and stroke volume determinations were used to evaluate the efficiency of the described technique. Results were amazingly consistent to indicate an efficient system for intermittently exercising the heart within safe and medically acceptable limits.

Gorman, H. A.↗
NASA NTRS1970

User oriented data processing at the University of Michigan

The multispectral techniques have shown themselves capable of solving problems in a large number of user areas. The results obtained are in some instances quite impressive. In many instances, the multispectral detection of various phenomena is an empirical fact for which there is little physical explanation today. To date, most of the user applications that have been addressed are exploratory in nature. The closest approximation to an operational situation encountered so far is that of the survey of wetlands in North Dakota reported in this paper.

Thomson, F. J.↗
NASA NTRS1971

Some experimental observations on circulating currents in a crossed field plasma accelerator

Experiments on a thermally ionized argon plasma suggest that applying a Lorentz force by means of orthogonal electric and magnetic fields to an electrically conducting fluid flow imposes necessary but not sufficient conditions for acceleration. There are, in fact, many combinations of current and magnetic field which cause decelerations of the fluid. The deceleration arises from a retarding force which may be larger than the applied Lorentz force. The retarding force causing the deceleration is a consequence of currents circulating completely within the fluid. These currents arise from differences in velocity between the central and wall regions of the duct which interact with the imposed magnetic field to produce differences in induced voltages. The observed physical effects of the circulating currents cause a loss in velocity in the central region of the duct, an increase in thermal energy in the sidewall region, and little change in thermal energy near the electrode wall region. For similar velocity profiles, the adverse effects appear to be related to the product of electrical conductivity and velocity, and performance as an accelerator appears to be controlled by the Hoffman loading parameter (i.e., the ratio of the applied to the induced currents).

Jedlicka, J.↗
NASA NTRS1972

Planned development of the space shuttle vehicle

Information pertaining to the planned development of the space shuttle vehicle is presented. The package contains: (1) President's statement; (2) Dr. Fletcher's statement; (3) space shuttle fact sheet; (4) important reasons for the space shuttle.

Source record↗
NASA NTRS1971

Foundations for estimation by the method of least squares

Least squares estimation is discussed from the point of view of a statistician. Much of the emphasis is on problems encountered in application and, more specifically, on questions involving assumptions: what assumptions are needed, when are they needed, what happens if they are not valid, and if they are invalid, how that fact can be detected.

Hauck, W. W., Jr.↗
NASA NTRS1972

Space shuttle: News release

The space shuttle fact sheet is presented. Four important reasons for the program are considered to be: (1) It is the only meaningful new manned space program which can be accomplished on a modest budget. (2) It is needed to make space operations less complex and costly. (3) It is required for scientific applications in civilian and military activities. (4) It will encourage greater international participation in space flight. The space shuttle and orbiter configurations are discussed along with the missions. The scope of the study and the costs of each contract for the major contractor are listed.

Source record↗
NASA NTRS1972

The stability of motion of satellites with flexible appendages

The mathematical formulation associated with the problem of stability of motion of a satellite consisting of a main rigid body and three (or less) pairs of flexible rods is presented. The rods are capable of flexure in two orthogonal directions. Whereas the rotational motion of the body is described by generalized coordinates depending on time alone, the elastic displacements of the rods depend both on spatial position and time. Assuming no external torques, there exist motion integrals in the form of momentum integrals. These integrals can be regarded as constraint equations relating the system velocities, and used to reduce the number of variables describing the motion. The stability analysis has been carried out by means of an extension of the Liapunov direct method. Since the elastic vibrations result in energy dissipation, it is shown that the equilibrium position is asymptotically stable if the Hamiltonian is positive definite and unstable if it can take negative values in the neighborhood of the equilibrium. Determining the sign definiteness of the Hamiltonian is complicated by the fact that it contains spatial derivatives of the elastic displacements. Two methods are presented to cope with this problem. The first, the standard modal analysis in conjunction with series truncation, develops criteria in terms of infinite series associated with the natural modes and frequencies of the elastic rods. The second, the method of integral coordinates, yields closed-form stability criteria involving the system parameters, such as the body moments of inertia, the length and mass distribution of the rods, the lowest natural frequencies of the rods, and the satellite spin velocity.

Meirovitch, L.↗
NASA NTRS1972

Optimum performance of hovering rotors

A theory for the optimum performance of a rotor hovering out of ground effect is developed. The performance problem is formulated using general momentum theory for an infinitely bladed rotor, and the effect of a finite number of blades is estimated. The analysis takes advantage of the fact that a simple relation exists between the radial distributions of static pressure and angular velocity in the ultimate wake, far downstream of the rotor, since the radial velocity vanishes there. This relation permits the establishment of an optimum performance criterion in terms of the ultimate wake velocities by introducing a small local perturbation of the rotational velocity and requiring the resulting ratio of thrust and power changes to be independent of the radial location of the perturbation. This analysis fully accounts for the changes in static pressure distribution and axial velocity distribution throughout the wake as the result of the local perturbation of the rotational velocity component.

Wu, J. C.↗
NASA NTRS1972

Facilities and support systems for a 90-day test of a regenerative life support system

A 90-day test is reported of a regenerative life support system which was completed in a space station simulator. The long duration of the test and the fact that it was manned, imposed rigid reliability and safety requirements on the facility. Where adequate reliability could not be built into essential facility systems, either backup systems or components were provided. Awareness was intensified by: (1) placing signs on every piece of equipment that could affect the test, (2) painting switches on all breaker panels a bright contrasting color, (3) restricting access to the test control area, and (4) informing personnel in the facility (other than test personnel) of test activities. It is concluded that the basic facility is satisfactory for conducting long-duration manned tests, and it is recommended that all monitor and alarm functions be integrated into a single operation.

Malin, R. L.↗
NASA NTRS1972

Development of approach control system requirements with applications to a jet transport

The development of requirements for an approach control system and example applications to a jet transport aircraft are presented. The material is divided into a general discussion of approach control requirements, and a specific application resulting in the design of three alternative longitudinal controllers. The point of view taken is that the essential features of the system structure are the feedbacks themselves, their equalization, and their combinations to create control commands. Use is made of the fact that for sucessful systems the possible feedback structures are very limited. They derive primarily from guidance, control, and regulation demands; and secondarily from dynamic response characteristics desired by the pilot. From the systems view it is the satisfaction of these requirements that is important rather than the means automatic, manual, or hygrid manual/automatic approach systems.

Mcruer, D. T.↗
NASA NTRS1972

Selected volcanic features, part L

Volcanic features obtained from a preliminary examination of Apollo 15 orbital photographs are described. Of particular interest are the features photographed in the vicinity of the far-side crater basin Tsiolkovsky. The photographs indicate that smooth, plains-forming material is present in parts of the ejecta blanket southeast of the basin rim. A debris flow on the northwestern part of the rim is also depicted. The usefulness of near-terminator photography is evidenced by the fact that numerous flow fronts not seen in photographs taken at higher angles of illumination are clearly visible. It is concluded that the presence of so many fronts confirms the belief that multiple flows are responsible for the filling of lunar mare basins.

West, M. N.↗
NASA NTRS1972

Assessment information systems

The assessment process in contemporary society and the role of the expert are discussed. The development of technology is considered in two stages: the preintroduction stage in which the developer makes the tests and decisions, and the application stage in which the user applies the technology and makes tests with different criteria. The adverse effects of death, personal injury, and collective injury are described, and resulting public actions are mentioned. The role of the experts is identified as asking relevant questions and recording observations, communicating with each other, summarizing the findings, and indicating the significance of the findings to those capable of deciding upon action. It is pointed out that the experts often disagree on facts and economic values. The basic problem is felt to be one of identifying the social significance in an assessment situation.

Danhof, C. H.↗
NASA NTRS1972

Technology assessment and the Congress

The legislative branch is considered as the major focus for technology assessment, and the functions of the Congressional Research Service in supplying Congressmen with scientific and technological development is outlined, and the need for Congress to control, assess, and integrate the various and conflicting elements for the benefit of both technology and society is stressed. The organization of the Science Policy Research Division is mentioned, and its duties in gathering facts for the increased understanding by the members of Congress are indicated. Technology assessment aspects associated with congressional committees and hearings, adequacy of advice, trends in engineering education, and the public interest are also discussed.

Carpenter, R. A.↗
NASA NTRS1972

Effects of incomplete adaption and disturbance in adaptive control

This investigation focused attention on the fact that the synthesis of adaptive control systems has often been discussed in the framework of idealizations which may represent over simplifications. A condition for boundedness of the tracking error has been derived for the case in which incomplete adaption and disturbance are present. When using Parks' design it is shown that instability of the adaptive gains can result due to the presence of disturbance. The theory has been applied to a nontrivial example in order to illustrate the concepts involved.

Lindorff, D. P.↗
NASA NTRS1972

Cross flow in a starved EHD contact

An analysis of lubrication cross flow effects under starved elastohydrodynamic conditions is presented. Starvation is defined as any operating condition such that an increase in oil available to the contact will result in an increase in film thickness. Starved EHD behavior is considered in several situations: (1) when no new oil enters the contact, and (2) when a step change in one of the rolling parameters is introduced at an equilibrium contact. Based on the fact that important oil flow within the Hertz zone is across the rolling contact direction, it is possible to formulate a simple theory which explains quantitatively some aspects of starved ball bearing behavior.

Kingsburg, E. P.↗
NASA NTRS1972

Analysis of fatigue crack propagation

The correlation between fatigue crack propagation and stress intensity factor is analyzed. When determining fatigue crack propagation rate, a crack increment, delta a, and its corresponding increment in load cycles, delta N, are measured. Fatigue crack propagation must be caused by a shear and/or a normal separation mode. Both of these two processes are discrete if one looks at the atomic level. If the average deformation and fracture properties over the crack increments, delta a, can be considered as homogeneous, if the characteristic discrete lengths of sigma a, if the plastic zone size is small, and if a plate is thick enough to insure a plane strain case, da/dN is proportional to delta K squared. Any deviation of empirical data from this relation must be caused by the fact that one or more of these conditions are not satisfied. The effects of plate thickness and material inhomogeneity are discussed in detail. A shear separation mode of fatigue crack propagation is described and is used to illustrate the effects of material inhomogeneity.

Liu, H. W.↗
NASA NTRS1972

High altitude color photography as a tool for regional analysis: As demonstrated for southeastern Florida

High altitude color and color infrared photography of the tri-county region of southeast Florida made it feasible to evaluate its potential for quantifying the dimensions of regional change. Attention was focused upon three main aspects of change in the region, which in fact overlap. These were; (1) the transformation of the southeast Florida wetlands; (2) the expansion of agriculture; and (3) the growth of the urbanized area. The development analyzed covered the period of thirteen years from 1956 to 1969. Results using this new 18 km photography were superior because of the degree of resolution, the combined power of color and color infrared interpretation, and the large area covered by each frame. The greatest advantage of high altitude imagery is the time-saving element, since it is possible to delineate and identify major geographic patterns over thousands of sq km very rapidly.

Eyre, L. A.↗
NASA NTRS1972

Homing orientation in salamanders: A mechanism involving chemical cues

A detailed description is given of experiments made to determine the senses and chemical cues used by salamanders for homing orientation. Sensory impairment and cue manipulative techniques were used in the investigation. All experiments were carried out at night. Results show that sense impaired animals did not home as readily as those who were blind but retained their sensory mechanism. This fact suggests that the olfactory mechanism is necessary for homing in the salamander. It was determined that after the impaired salamander regenerated its sensory mechanism it too returned home. It was concluded that homing ability in salamanders is direction independent, distant dependent, and vision independent.

Madison, D. M.↗