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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The effects of acceleration stress on human workload and manual control

The effects of +Gz stress on operator task performance and workload were assessed. Subjects were presented a two dimensional maze and were required to solve it as rapidly as possible (by moving a light dot through it via a trim switch on a control stick) while under G-stress at levels from +1 Gz to +6 Gz. The G-stress was provided by a human centrifuge. The effects of this stress were assessed by two techniques; (1) objective performance measures on the primary maze-solving task, and (2) subjective workload measures obtained using the subjective workload assessment technique (SWAT). It was found that while neither moderate (+3 Gz) nor high (+5 Gz and +6 Gz) levels of G-stress affected maze solving performance, the high G levels did increase significantly the subjective workload of the maze task.

Gill, R. T.↗
NASA NTRS2011

Off-Body Boundary-Layer Measurement Techniques Development for Supersonic Low-Disturbance Flows

Investigations were performed to develop accurate boundary-layer measurement techniques in a Mach 3.5 laminar boundary layer on a 7 half-angle cone at 0 angle of attack. A discussion of the measurement challenges is presented as well as how each was addressed. A computational study was performed to minimize the probe aerodynamic interference effects resulting in improved pitot and hot-wire probe designs. Probe calibration and positioning processes were also developed with the goal of reducing the measurement uncertainties from 10% levels to less than 5% levels. Efforts were made to define the experimental boundary conditions for the cone flow so comparisons could be made with a set of companion computational simulations. The development status of the mean and dynamic boundary-layer flow measurements for a nominally sharp cone in a low-disturbance supersonic flow is presented.

Owens, Lewis R.↗
NASA NTRS1989

Temperature dependence of penetration depth in thin film niobium

A novel technique is presented which should allow precise determination of the temperature dependence of the inductance, and hence of the penetration depth, of superconducting niobium thin-film structures. Four niobium thin-film stripline inductors are arranged in a bridge configuration, and inductance differences are measured using a potentiometric technique with a SQUID (superconducting quantum interference device) as the null detector. Numerical simulations of the stripline inductances are presented which allow the performance of the measurement technique to be evaluated. The prediction of the two-fluid model for the penetration-depth temperature dependence is given for reduced temperatures of 0.3 to 0.9. The experimental apparatus and its resolution and accuracy are discussed.

More, N.↗
NASA NTRS2011

Spectroelectrochemical Instrument Measures TOC

A spectroelectrochemical instrument has been developed for measuring the total organic carbon (TOC) content of an aqueous solution. Measurements of TOC are frequently performed in environmental, clinical, and industrial settings. Until now, techniques for performing such measurements have included, various ly, the use of hazardous reagents, ultraviolet light, or ovens, to promote reactions in which the carbon contents are oxidized. The instrument now being developed is intended to be a safer, more economical means of oxidizing organic carbon and determining the TOC levels of aqueous solutions and for providing a low power/mass unit for use in planetary missions.

Kounaves, Sam↗
NASA NTRS1992

Performance measurement for information systems: Industry perspectives

Performance measurement has become a focal topic for information systems (IS) organizations. Historically, IS performance measures have dealt with the efficiency of the data processing function. Today, the function of most IS organizations goes beyond simple data processing. To understand how IS organizations have developed meaningful performance measures that reflect their objectives and activities, industry perspectives on IS performance measurement was studied. The objectives of the study were to understand the state of the practice in IS performance techniques for IS performance measurement; to gather approaches and measures of actual performance measures used in industry; and to report patterns, trends, and lessons learned about performance measurement to NASA/JSC. Examples of how some of the most forward looking companies are shaping their IS processes through measurement is provided. Thoughts on the presence of a life-cycle to performance measures development and a suggested taxonomy for performance measurements are included in the appendices.

Bishop, Peter C.↗
NASA NTRS1993

The evaluation of several agility metrics for fighter aircraft using optimal trajectory analysis

Several functional agility metrics, including the combat cycle time metric, dynamic speed turn plots, and relative energy state metric, are used to compare turning performance for generic F-18, X-29, and X-31-type aircraft models. These three-degree-of-freedom models have characteristics similar to the real aircraft. The performance comparisons are made using data from optimal test trajectories to reduce sensitivities to different pilot input techniques and to reduce the effects of control system limiters. The turn performance for all three aircraft is calculated for simulated minimum time 180 deg heading captures from simulation data. Comparisons of the three aircraft give more insight into turn performance than would be available from traditional measures of performance. Using the optimal test technique yields significant performance improvements as measured by the metrics. These performance improvements were found without significant increases in turn radius.

Ryan, George W., III↗
NASA NTRS2001

ZBLAN Viscosity Instrumentation

The past year's contribution from Dr. Kaukler's experimental effort consists of these 5 parts: a) Construction and proof-of-concept testing of a novel shearing plate viscometer designed to produce small shear rates and operate at elevated temperatures; b) Preparing nonlinear polymeric materials to serve as standards of nonlinear Theological behavior; c) Measurements and evaluation of above materials for nonlinear rheometric behavior at room temperature using commercial spinning cone and plate viscometers available in the lab; d) Preparing specimens from various forms of pitch for quantitative comparative testing in a Dynamic Mechanical Analyzer, Thermal Mechanical Analyzer; and Archeological Analyzer; e) Arranging to have sets of pitch specimens tested using the various instruments listed above, from different manufacturers, to form a baseline of the viscosity variation with temperature using the different test modes offered by these instruments by compiling the data collected from the various test results. Our focus in this project is the shear thinning behavior of ZBLAN glass over a wide range of temperature. Experimentally, there are no standard techniques to perform such measurements on glasses, particularly at elevated temperatures. Literature reviews to date have shown that shear thinning in certain glasses appears to occur, but no data is available for ZBLAN glass. The best techniques to find shear thinning behavior require the application of very low rates of shear. In addition, because the onset of the thinning behavior occurs at an unknown elevated temperature, the instruments used in this study must provide controlled low rates of shear and do so for temperatures approaching 600 C. In this regard, a novel shearing parallel plate viscometer was designed and a prototype built and tested.

Kaukler, William↗
NASA NTRSDate not supplied

Development of an Apparatus and Process for Precision Measurement of Cryogenic Thermal Expansion of Materials

NASA frequently needs thermal contraction data for materials to be used in cryogenic space flight missions. To satisfy this need, we developed an apparatus and a high-precision technique for performing such measurements using a commercial fiber-optic-based position sensor. We describe the measurement process and its verification using a copper sample. We also present data for two materials which we characterized for potential NASA use.

Cryogenic↗
NASA NTRS1989

A laboratory investigation into microwave backscattering from sea ice

The sources of scattering of artificial sea ice were determined, backscatter measurements semi-quantitatively were compared with theoretical predictions, and inexpensive polarimetric radars were developed for sea ice backscatter studies. A brief review of the dielectric properties of sea ice and of commonly used surface and volume scattering theories is presented. A description is provided of the backscatter measurements performed and experimental techniques used. The development of inexpensive short-range polarimetric radars is discussed. The steps taken to add polarimetric capability to a simple FM-W radar are considered as are sample polarimetric phase measurements of the radar. Ice surface characterization data and techniques are discussed, including computation of surface rms height and correlation length and air bubble distribution statistics. A method is also presented of estimating the standard deviation of rms height and correlation length for cases of few data points. Comparisons were made of backscatter measurements and theory. It was determined that backscatter from an extremely smooth saline ice surface at C band cannot be attributed only to surface scatter. It was found that snow cover had a significant influence on backscatter from extremely smooth saline ice at C band.

Bredow, Jonathan W.↗
NASA NTRS1989

A laboratory investigation into microwave backscattering from sea ice

The purpose of the research reported here was to determine the sources of scattering of artificial sea ice, to compare backscatter measurements semi-quantitatively with theoretical predictions, and to develop inexpensive polarimetric radars for sea ice backscatter studies. A brief review of the dielectric properties of sea ice and of commonly used surface and volume scattering theories is presented. We provide a description of the backscatter measurements performed and experimental techniques used. The development of inexpensive short-range polarimetric radars is discussed. We discuss limitations of this system and the development of a radar that avoids the oscillator instability problems of continuously tunable oscillators by doing measurements at discrete frequencies, using a synthesized frequency source. We present results of simple test of copolar phase capability and a simple method of doing phase calibrations. We discuss ice surface characterization data and techniques. We also present a method of estimating the standard deviation of rms height and correlation length for cases of few data points.

Bredow, Jonathan W.↗
NASA NTRS2010

Simultaneous, Unsteady PIV and Photogrammetry Measurements of a Tension-Cone Decelerator in Subsonic Flow

This paper describes simultaneous, synchronized, high-frequency measurements of both unsteady flow in the wake of a tension-cone decelerator in subsonic flow (by PIV) and the unsteady shape of the decelerator (by photogrammetry). The purpose of these measurements was to develop the test techniques necessary to validate numerical methods for computing fluid-structure interactions of flexible decelerators. A critical need for this effort is to map fabric surfaces that have buckled or wrinkled so that code developers can accurately represent them. This paper describes a new photogrammetric technique that performs this measurement. The work was done in support of the Entry, Descent, and Landing discipline within the Supersonics Project of NASA s Fundamental Aeronautics Program.

Schairer, Edward T.↗
NASA NTRS1980

Optoacoustic measurement of vibrational-translational /V-T/ rates using a short pulse CO2 laser

A technique for measuring the V-T transfer rates of polyatomic species based on the optoacoustic effect discovered by Bell, Tyndall, and Rontgen (1881) is investigated experimentally. The technique makes use of a coincidental resonance between one of the molecules vibration rotation bands and a CO2 laser line. By this absorption, the molecules can be excited to a known vibrational mode. Since typical time constants for V-T transfer are about 0.00001 sec torr, this method can be used in the pressure region up to 1 torr. The results obtained for CH3F agree with the measurements performed by other techniques.

Lawandy, N. M.↗
NASA NTRS1977

Design of turbofan engine controls using output feedback regulator theory

A multivariable control design procedure based on output feedback regulator (OFR) theory is applied to the F100 turbofan engine. Results for the OFR design are compared to a design based on linear quadratic regulator (LQR) theory. The OFR feedback control is designed in the full order state space and thus eliminates any need for model reduction techniques. Using the performance measure and control structure of the LQR design, an equivalent OFR feedback control is obtained. The flexibility of the OFR as a control design procedure is demonstrated, and differing feedback control structures are evaluated.

Merrill, W. C.↗
NASA NTRS1978

Investigation of the jet-wake flow of a highly loaded centrifugal compressor impeller

Investigations, aimed at developing a better understanding of the complex flow field in high performance centrifugal compressors were performed. Newly developed measuring techniques for unsteady static and total pressures as well as flow directions, and a digital data analysis system for fluctuating signals were thoroughly tested. The loss-affected mixing process of the distorted impeller discharge flow was investigated in detail, in the absolute and relative system, at impeller tip speeds up to 380 m/s. A theoretical analysis proved good coincidence of the test results with the DEAN-SENOO theory, which was extended to compressible flows.

Eckardt, D.↗
NASA NTRS1977

Design of turbofan engine controls using output feedback regulator theory

A multivariable control design procedure based on output feedback regulator (OFR) theory is applied to the F100 turbofan engine. Results for the OFR design are compared to a design based on linear quadratic regulator (LQR) theory. This LQR design was obtained as part of the F100 Multivariable Control Synthesis (MVCS) program. In the MVCS program the LQR feedback control was designed in a reduced dimension state space and then applied to the original system. However, the OFR feedback control is designed in the full order state space and thus eliminates any need for model reduction techniques. Using the performance measure and control structure of the MVCS program LQR design, an equivalent OFR feedback control is obtained. The flexibility of the OFR as a control design procedure is demonstrated and differing feedback control structures are evaluated.

Merrill, W. C.↗
NASA NTRS1990

Human performance measurement: Validation procedures applicable to advanced manned telescience systems

As telescience systems become more and more complex, autonomous, and opaque to their operators it becomes increasingly difficult to determine whether the total system is performing as it should. Some of the complex and interrelated human performance measurement issues are addressed as they relate to total system validation. The assumption is made that human interaction with the automated system will be required well into the Space Station Freedom era. Candidate human performance measurement-validation techniques are discussed for selected ground-to-space-to-ground and space-to-space situations. Most of these measures may be used in conjunction with an information throughput model presented elsewhere (Haines, 1990). Teleoperations, teleanalysis, teleplanning, teledesign, and teledocumentation are considered, as are selected illustrative examples of space related telescience activities.

Haines, Richard F.↗
NASA NTRS1991

Evolution of the large Deep Space Network antennas

The evolution of the largest antenna of the US NASA Deep Space Network (DSN) is described. The design, performance analysis, and measurement techniques, beginning with its initial 64-m operation at S-band (2295 MHz) in 1966 and continuing through the present ka-band (32-GHz) operation at 70 m, is described. Although their diameters and mountings differ, these parabolic antennas all employ a Cassegrainian feed system, and each antenna dish surface is constructed of precision-shaped perforated-aluminum panels that are secured to an open steel framework

Imbriale, William A.↗
NASA NTRS1992

Nucleation and growth of rolling contact failure of 440C bearing steel

A 'two-body' elasto-plastic finite element model of 2-dimensional rolling and rolling-plus-sliding was developed to treat the effect of surface irregularities. The model consists of a smooth cylinder in contact with a semi-infinite half-space that is either smooth or fitted with one of 0.4 microns deep or 7 microns deep groove, or a 0.4 microns high ridge-like asperity. The model incorporates elastic-linear-kinematic hardening-plastic (ELKP) and non-linear-kinematic hardening-plastic (NLKP) material constitutive relations appropriate for hardened bearing steel and the 440C grade. The calculated contact pressure distribution is Hertzian for smooth body contact, and it displays intense, stationary, pressure spikes superposed on the Hertzian pressure for contact with the grooved and ridged surface. The results obtained for the 0.4 microns deep groove compare well with those reported by Elsharkawy and Hamrock for an EHD lubricated contact. The effect of translating the counterface on the half space as opposed to indenting the half space with the counter face with no translation is studied. The stress and strain values near the surface are found to be similar for the two cases, whereas they are significantly different in the subsurface. It is seen that when tiny shoulders are introduced at the edge of the groove in the finite element model, the incremental plasticity and residual stresses are significantly higher in the vicinity of the right shoulder (rolling direction is from left to right) than at the left shoulder. This may explain the experimental observation that the spall nucleation occurs at the exit end of the artificially planted indents. Pure rolling calculations are compared with rolling + sliding calculations. For a coefficient of friction, mu = 0.1, the effect of friction is found to be small. Efforts were made to identify the material constitutive relations which best describe the deformation characteristics of the bearing steels in the initial few cycles. Elastic-linear-kinematic hardening-plastic (ELKP) material constitutive relations produce less net plastic deformation in the initial stages for a given stress, than seen in experiments. A new set of constitutive relations: non-linear-kinematic hardening-plastic (NLKP) was used. This material model produces more plasticity than the ELKP model and shows promise for treating the net distortions in the early stages. Techniques for performing experimental measurements that can be compared with the finite element calculations were devised. The measurements are being performed on 9mm-diameter, 440C steel cylindrical rolling elements in contact with 12.5 mm-diameter, 52100 steel balls in a 3-ball-rod fatigue test machine operating at 3600 RPM. Artificial, 7 microns deep, indents were inserted on the running track of the cylindrical rolling elements and profilometer measurements of these indents made, before and after the rolling. These preliminary measurements show that the indents are substantially deformed plastically in the process of rolling. The deformations of the groove calculated with the finite element model are comparable to those measured experimentally.

Gupta, V.↗