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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

An algorithm and computer program to locate real zeros of real polynomials

A method for reliably extracting real zeros of real polynomials using an expanded two-point secant and bisection method is formed into an algorithm for a digital computer, and a computer program based on this algorithm is presented. The results obtained with the program show that the proposed method compares favorably with the Laguerre, Newton-Raphson, and Jenkins-Traub methods when the polynomial has all real zeros, and is more efficient when the polynomial has complex zeros.

Hedgley, D. R., Jr.↗
NASA NTRS1975

Some properties of extremal solutions of zero-sum differential games

Necessary conditions for infinite-time linear-quadratic two-player differential games with perfect state information are examined in the light of Willems' work on the algebraic Riccati equation. Necessary conditions for the nonzero-sum game do not always reduce precisely to those of the zero-sum game, when the weighting parameters of the cost index are taken as those of a zero-sum game. Formulation of zero-sum game problems in extended L2-spaces reveals the existence of nonstabilizing but infimal controls, and explicit frequency-domain conditions for existence of solutions and stabilizing solutions are established through the algebraic Riccati equation (ARE).

Johnson, T. L.↗
NASA NTRS1976

Zero-G flight test of a gauging system. Volume 1: Summary

The capability of a nucleonic gauging system to gauge the content of a reduced-scale storable liquid tank in a zero-g environment as provided by a KC-135 Zero-G Aircraft was demonstrated. Although the propellant-ullage interface never achieved the stable, zero-g equilibrium configuration, the gauging system gauged liquid quantity over all tank loadings to a total system accuracy the order of two percent. It was also determined that the gauging system presented no undue safety hazard to operating personnel in either ground and/or flight testing.

Source record↗
NASA NTRS1976

Effects of Mach number and afterbody length on aerodynamic side forces at zero sideslip on symmetric bodies at high angles of attack

Wind-tunnel measurements of side force over the Mach number range of 0.25 to 2 for pointed forebody-alone and for ogive-cylinder models of various fineness ratios up to 16, are presented. The angle of attack where side force first occurs (onset), where it returns to zero (upper limit), and its magnitude are examined. The onset angle depends only on body geometry, longer bodies having lower onset angles. The upper limit, which is about 80 deg at M = 0.25, decreases with Mach number. The maximum side forces decrease with increasing Mach number, approaching zero within the Mach number range of 0.8 to 1.2; within this range, the Mach number at which the forces approach zero varies directly with forebody slenderness.

Keener, E. R.↗
NASA NTRS1977

Apollo-Soyuz pamphlet no. 8: Zero-g technology

The behavior of liquids in zero gravity environments is discussed with emphasis on foams, wetting, and wicks. A multipurpose electric furnace (MA-010) for the high temperature processing of metals and salts in zero-g is described. Experiments discussed include: monolectic and synthetic alloys (MA-041); multiple material melting point (MA-150); zero-g processing of metals (MA-070); surface tension induced convection (MA-041); halide eutectic growth; interface markings in crystals (MA-060); crystal growth from the vapor phase (MA-085); and photography of crystal growth (MA-028).

Page, L. W.↗
NASA NTRS1977

Spectral interpolation - Zero fill or convolution

Zero fill, or augmentation by zeros, is a method used in conjunction with fast Fourier transforms to obtain spectral spacing at intervals closer than obtainable from the original input data set. In the present paper, an interpolation technique (interpolation by repetitive convolution) is proposed which yields values accurate enough for plotting purposes and which lie within the limits of calibration accuracies. The technique is shown to operate faster than zero fill, since fewer operations are required. The major advantages of interpolation by repetitive convolution are that efficient use of memory is possible (thus avoiding the difficulties encountered in decimation in time FFTs) and that is is easy to implement.

Forman, M. L.↗
NASA NTRS1976

Zero-G Workstation Design

Zero-g workstations were designed throughout manned spaceflight, based on different criteria and requirements for different programs. The history of design of these workstations is presented along with a thorough evaluation of selected Skylab workstations (the best zero-g experience available on the subject). The results were applied to on-going and future programs, with special emphasis on the correlation of neutral body posture in zero-g to workstation design. Where selected samples of shuttle orbiter workstations are shown as currently designed and compared to experience gained during prior programs in terms of man machine interface design, the evaluations were done in a generic sense to show the methods of applying evaluative techniques.

Gundersen, R. T.↗
NASA NTRS1979

Early cardiovascular adaptation to simulated zero gravity

A study was conducted on five normal male volunteers (23-29 yr), under controlled conditions, to evaluate early adaptive responses to zero gravity. Specific objectives are (1) to characterize the hemodynamic, renal and hormonal responses to a central fluid shift, and (2) to compare data obtained during and after head-down tilt with corresponding data from actual space flight to validate tilt as a physiological model for simulation of zero gravity. Zero gravity is simulated by a 24-hr period of head-down tilt at 5 deg. The results suggest that hemodynamic adaptation occurs rapidly and is essentially accomplished by 6 hr, and that adaptation includes diuresis and reduction in blood volume. The validity of head-down tilt at 5 deg as an experimental model is established by comparing the results obtained with data from Apollo and Skylab astronauts on body fluid distributions and postflight responses to orthostatic and exercise stress.

Nixon, J. V.↗
NASA NTRS1978

The behavior of superfluid helium in zero gravity

Studies of the behavior of superfluid helium in zero gravity including fluid distribution within the cryostat, thickness of superfluid films, and heat transfer in such films, were conducted in one gravity in the laboratory and in zero-g flights on aircraft and sounding rocket. The studies show that the bulk motions are sufficiently well damped to allow control of their effects on experiments and spacecraft attitude control systems, and that the superfluid films will be able to maintain the high degree of temperature uniformity found in laboratory superfluid helium cryostats. The presentation includes film clips of the motions on the superfluid in zero-g.

Mason, P.↗
NASA NTRS1980

Superfluid helium film in zero gravity

The behaviour of nearly-saturated superfluid helium films several hundred Angstroms thick was investigated under zero gravity conditions in a small cryostat carried on a 0.3 m diameter, 3 m long sounding rocket, using a quartz microbalance technique. The flight provided 30 s of high acceleration, about 5 min. of zero gravity, and 90 s of mg acceleration. The temperature of the experiment ranged from 1.67 to 2.15 K. In contrast to ground test results, thick films uniformly distributed on all surfaces were observed in zero gravity.

Yang, L. C.↗
NASA NTRS1981

Zero-gravity aerosol behavior

The feasibility and scientific benefits of a zero gravity aerosol study in an orbiting laboratory were examined. A macroscopic model was devised to deal with the simultaneous effects of diffusion and coagulation of particles in the confined aerosol. An analytical solution was found by treating the particle coagulation and diffusion constants as ensemble parameters and employing a transformation of variables. The solution was used to carry out simulated zero gravity aerosol decay experiments in a compact cylindrical chamber. The results demonstrate that the limitations of physical space and time imposed by the orbital situation are not prohibitive in terms of observing the history of an aerosol confined under zero gravity conditions. While the absence of convective effects would be a definite benefit for the experiment, the mathematical complexity of the problem is not greatly reduced when the gravitational term drops out of the equation. Since the model does not deal directly with the evolution of the particle size distribution, it may be desirable to develop more detailed models before undertaking an orbital experiment.

Edwards, H. W.↗
NASA NTRS1980

Assessment of zero gravity effects on space worker health and safety

One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the references Solar Power Satellites (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers either immediate or delayed due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiency in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five year career period. The proposed 90 day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five year career.

Source record↗
NASA NTRS1981

Penetrating transmission zeros in the design of robust servomechanism systems

In the design of a robust servomechanism system, it is well known that the system cannot track a reference signal whose frequency coincides with the transmission zeros of the system. This paper proposes a new design method for overcoming this difficulty. The controller to be used employs a sampler and holding device with exponential decay. It is shown that the transmission zeros of the discretized system can be shifted by changing the rate of the exponential decay of the holding device. Thus, it is possible to design a robust controller for the discretized system to track any reference signal of given frequency, even if the given frequency coincides with the transmission zeros of the original continuous-time system.

Wang, S. H.↗
NASA NTRS1985

Behavior of the lean methane-air flame at zero-gravity

A special rig was designed and constructed to be compatible with the NASA Lewis Research Center Airborne Research Laboratory to allow the study of the effect of gravity on the behavior of lean limit in a standard 50.4 mm (2 in.) internal diameter tube when the mixtures are ignited at the open end and propagate towards the closed end of the tube. The lean limit at zero gravity was found to be 5.10% methane and the flame was found to extenguish in a manner previously observed for downward propagating flames at one g. It was observed that g-jitter could be maintained at less than + or 0.04 g on most zero g trajectories. All of propagating lean limit flames were found to be sporadically cellularly unstable at zero g. There was no observable correlation between the occurrence of g-jitter and the lean limit, average propagation speed of the flame through the tube or the occurrence of cellular instability.

Noe, K. A.↗
NASA NTRS1984

A study of Sabatier reactor operation in zero 'G'

The results of zero-g computer model simulation of the operation of a Sabatier reactor, which relies on the effects of buoyant forces, are presented. The reactor was also operated in an experiment with inlet flow rates of carbon dioxide that correspond to continuous operation of the reactor at three, five, eight, and ten-man loading conditions; the three and five-man conditions are noted to be within the design capabilities of the reactor. The loss of carbon dioxide conversion predicted by the model for zero-g environment is noted to be substantial, ranging from 12 to 18.2 percent for five-man to ten-man loading. The simulated normal-gravity values are within 0.9 percent of the experimental conversions. Finally, the results indicate a much hotter operation of the reactor in zero-g due to the loss of natural convective cooling effect.

Forsythe, R. K.↗
NASA NTRS1985

A Study of Blood Flow and of Aggregation of Blood Cells Under Conditions of Zero Gravity: Its Relevance to the Occlusive Diseases and Cancer

The objectives of this program are: (1) to determine whether the size of red cell aggregates, kinetics and morphology of these aggregates are influenced by near-zero gravity; (2) whether viscosity, especially at low shear rate, is afflicted by near-zero gravity (the latter preventing sedimentation of red cells); (3) whether the actual shape of red cells changes; and (4) whether blood samples obtained from different donors (normal and patients suffering from different disorders) react in the same manner to near-zero gravity.

Dintenfass, L.↗
NASA NTRS1991

Overpressurized zero pressure balloon system

Typical zero pressure scientific balloon systems experiencing diurnal cycles require on board expendable ballast to maintain design float altitude. In the past, pressurized balloon systems have been employed to overcome the need for ballast while maintaining small diurnal altitude excursions. However, requirements on material characteristics and manufacturing methods have enforced limitations on balloon size and therefore payload and altitude capabilities. This effort was aimed at considering the use of current (or slightly modified) zero pressure balloon systems (design, manufacturing and materials) as candidates for pressurized vehicles. Data gathered through performance analysis, structural analysis and flight testing has shown that the use of current zero pressure designs can be expanded to enhance balloon performance.

Simpson, Joel M.↗
NASA NTRS1992

Transmission zeros of non-collocated flexible structures - Finite-dimensional effects

This paper studies the properties of the transmission zeros of flexible structures with non-collocated sensors and actuators. These properties are shown to be considerably more complicated than for the case of collocated structures. In particular, a finite-dimensional non-collocated structure can have zeros which are general complex numbers, rather than purely real or imaginary quantities. Furthermore, the convergence of these zeros to the true values as the order of the model is increased is typically quite complicated.

Williams, Trevor↗