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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Rapid measurements of areal sensitivity and areal spectral response of photodetectors

A flying spot scanning system was used to obtain areal sensitivity and areal spectral response data for nineteen photomultipliers. The efficiency of the electron optics was shown to be dependent upon the type of dynode structure used in the several photomultipliers. From areal sensitivity measurements it was found that the relative spectral response per unit area can vary over the face of a photomultiplier.

Youngbluth, O., Jr.↗
NASA NTRS1974

Environment-sensitive manipulator control

Environment-sensitive manipulator control (control systems capable of controlling manipulator motion based on real-time response to sensor data obtained during the attempt to perform a requested task) is described, and experiments on (1) proximity control in manipulation and (2) application of an articulated and adaptively controlled hand-to-environment-sensitive manipulator control are reported. The efficiency of such systems is determined by the separation of control and data processing functions between operator and computer.

Bejczy, A. K.↗
NASA NTRS1975

Deformation characteristics and time-dependent notch sensitivity of Udimet 700 at intermediate temperatures

Time-dependent notch sensitivity of Udimet 700 sheet, bar, and investment castings was observed between 1000 and 1400 F (538-760 C) but not at 1600 F (871 C). As was the case for Modified Waspaloy, Waspaloy, Rene 41, Inconel 718, and TD-NiCr, it occurred when notched specimens were loaded below the yield strength and when creep deformation was localized. For each gamma-prime strengthened alloy and notched specimen geometry, a stress-average particle size zone can be defined to characterize the notch-sensitive behavior.

Wilson, D. J.↗
NASA NTRS1975

A sensitivity analysis of regional and small watershed hydrologic models

Continuous simulation models of the hydrologic behavior of watersheds are important tools in several practical applications such as hydroelectric power planning, navigation, and flood control. Several recent studies have addressed the feasibility of using remote earth observations as sources of input data for hydrologic models. The objective of the study reported here was to determine how accurately remotely sensed measurements must be to provide inputs to hydrologic models of watersheds, within the tolerances needed for acceptably accurate synthesis of streamflow by the models. The study objective was achieved by performing a series of sensitivity analyses using continuous simulation models of three watersheds. The sensitivity analysis showed quantitatively how variations in each of 46 model inputs and parameters affect simulation accuracy with respect to five different performance indices.

Ambaruch, R.↗
NASA NTRS1976

Differential absorption and scattering sensitivity predictions

A set of general equations for evaluating the sensitivity of the Differential Absorption and Scattering (DAS) technique based upon a conventional analysis of statistical errors is derived. The equations are put in a proper form for evaluating total column density and range resolved concentration measurements of a variety of atmospheric species. The derived equation are subsequently used to analyze the sensitivity of DAS in three specific applications assuming realistic parameters for the optical and electronic components of proposed DAS systems. The three DAS applications evaluated are: (1) measurement of nitrogen at ground levels over a horizontal path; (2) measurement of atmospheric ozone depletion in the wake of a jet engine at 20 km altitude; and (3) measurements of the ozone distribution in the atmosphere from an orbiting space platform, in a downward viewing mode. The results of this study have shown that with reasonable laser energy and telescope receiver dimensions, DAS is capable of meeting requirements for performing these measurements.

Thompson, R. T., Jr.↗
NASA NTRS1976

Computation and sensitivity considerations of the Ricatti equation in spacecraft CMG steering laws

The steady-state matrix Ricatti equation is studied with respect to sensitivity and computational burden for a linear regulator controller in spacecraft. The class of systems studied use control moment gyros (CMGs) as the torque driver, assuming that the CMGs are free of gimbal stops. Different solution techniques are evaluated relative to computation time and accuracy to determine which solution method is most acceptable with respect to the prescribed requirements. It is shown that it is not feasible to eliminate off-diagonal Ricatti equation terms in the relevent updata equation due to their high sensitivity, that Potter's algebraic technique requires the least computation time of the methods studied, and that the simple Euler method yields the best results when accuracy and computation time are equally weighted. If an optimal linear regulator formulation is employed, a full Ricatti equation solution of n(n + 1)2 elements of the symmetric positive definite gain matrix which is the solution to the matrix Ricatti equation must be computed at each update cycle.

Colburn, B. K.↗
NASA NTRS1976

Sensitivity limits of an infrared heterodyne spectrometer for astrophysical applications

A discussion and an evaluation of the degradation in sensitivity are given for a heterodyne spectrometer employing a HgCdTe photodiode mixer and tunable diode lasers. The minimum detectable source brightness is considered as a function of the mixer parameters, transmission coefficient of the beam splitter, and local oscillator emission powers. The degradation in the minimum detectable line source brightness that results from the bandwidth being a fraction of the line width is evaluated and plotted as a function of the wavelength and bandwidth for various temperature to mass ratios. It is shown that the minimum achievable degradation in the sensitivity of a practical astronomical heterodyne spectrometer is about 30. Estimates of SNRs with which IR line emission from astronomical sources of interest may be detected are given.

Abbas, M. M.↗
NASA NTRS1976

Sensitivity of an astronomical infrared heterodyne spectrometer

The factors determining the sensitivity of a real astronomical heterodyne spectrometer are described. The deviation from the ideal heterodyne system for line detection is described in terms of a series of degradation factors. A discussion of degradation due to a low local oscillator power and to line profile detection is presented. Representative values for the degradation factors are given. Even with a total degradation of not less than 30, the heterodyne spectrometer is still found to be a highly sensitive tool in IR astronomy.

Kostiuk, T.↗
NASA NTRS1976

Convection sensitivity and thermal analyses for indium and indium-lead mixing experiment (74-18)

Sounding rocket Experiment 74-18 was designed to demonstrate the effects of the Black Brandt rocket acceleration levels (during the low-g coast phase of its flight) on the motion of a liquid metal system to assist in preflight design. Some post flight analyses were also conducted. Preflight studies consisted of heat transfer analysis and convection sensitivity and convection modeling analyses which aided in the: (1) final selection of fluid materials (indium-lead melts rather than paraffins); (2) design and timing of heater and quench system; and (3) preflight predictions of the degree of lead penetration into the pure indium segment of the fluid. Postflight studies involved: (1) updating the convection sensitivity calculations by utilizing actual flight gravity levels; and (2) modeling the mixing in the flight samples.

Bourgeois, S. V.↗
NASA NTRS1977

Spacecraft design sensitivity for a disaster warning satellite system

A disaster warning satellite (DWS) is described for warning the general public of impending natural catastrophes. The concept is responsive to NOAA requirements and maximizes the use of ATS-6 technology. Upon completion of concept development, the study was extended to establishing the sensitivity of the DWSS spacecraft power, weight, and cost to variations in both warning and conventional communications functions. The results of this sensitivity analysis are presented.

Maloy, J. E.↗
NASA NTRS1977

Space shuttle orbiter digital data processing system timing sensitivity analysis OFT ascent phase

Dynamic loads were investigated to provide simulation and analysis of the space shuttle orbiter digital data processing system (DDPS). Segments of the ascent test (OFT) configuration were modeled utilizing the information management system interpretive model (IMSIM) in a computerized simulation modeling of the OFT hardware and software workload. System requirements for simulation of the OFT configuration were defined, and sensitivity analyses determined areas of potential data flow problems in DDPS operation. Based on the defined system requirements and these sensitivity analyses, a test design was developed for adapting, parameterizing, and executing IMSIM, using varying load and stress conditions for model execution. Analyses of the computer simulation runs are documented, including results, conclusions, and recommendations for DDPS improvements.

Lagas, J. J.↗
NASA NTRS1976

An avionics sensitivity study. Volume 2: Evaluation of airborne navigation system performance during RNAV/MLS transition

A computer simulation was modified to generate a suitable data base for performance of an avionics sensitivity study during RNAV/MLS transition. The avionics sensitivity data provides information necessary to establish requirements for additional guidance law design during transition and to establish airspace requirements for maneuvering to null out any residual RNAV errors upon MLS transition. The data base is also beneficial as planning information for subsequent flight testing.

Heine, W.↗
NASA NTRS1976

Sensitivity of solar-cell performance to atmospheric variables. 2: Dissimilar cells at several locations

Several solar cells having dissimilar spectral response curves and cell construction were measured at various locations in the United States to determine sensitivity of cell performance to atmospheric water vapor and turbidity. The locations selected represent a broad range of summer atmospheric conditions, from clear and dry to turbid and humid. Cell short circuit current under direct normal incidence sunlight, the intensity, water vapor and turbidity were measured. Regression equations were developed from the limited data base in order to provide a single method of prediction of cell current sensitivity to the atmospheric variables.

Klucher, T. M.↗
NASA NTRS1976

Vulcanism, mercury-sensitized photo-reactions and abiogenetic synthesis - A theoretical treatment

Attention is called to the photodynamic and thermodynamic properties of Periodic Group IIb elements, most notably Hg, as they relate to ultra-violet sensitization in organic chemical reactions. The energy levels of 6 1P1 and 6 3P1 resonance states and the high vapor pressure (greater than 0.001 mm) of the metal at temperatures as low as 293 K bring Hg with the range of bond dissociation energies in most organic molecules and many inorganics. These capabilities considered together with recent evidence for Hg emission as a regular part of volcanic and geothermal processes provide the basis for a proposal that Hg-sensitized ultraviolet photo-reactions may have played a significant part in abiogenetic organic synthesis on the primative earth.

Siegel, S. M.↗
NASA NTRS1977

The interrelationship between observers and system sensitivity

System observer theory and system sensitivity theory have developed as two distinct bodies of research literature. In this study an interrelationship between the two problem classes is considered. It is shown that the observer and the sensitivity problems are duals of each other.

Porter, W. A.↗
NASA NTRS1977

Lunar magnetic permeability studies and magnetometer sensitivity

A regression of quiet magnetic field components simultaneously measured by the two Explorer 35 magnetometers reveals uncertainties in effective sensitivity factors of up to a few percent in one or both of these instruments. Given this, the validity of previous lunar permeability studies based on Explorer 35/ALSEP regressions, wherein inferences are drawn from regression line slopes differing from unity by the order of one percent, is called into question. We emphasize the need to critically address the question of small deviations in magnetometer sensitivity factors from nominal values as a part of any two-magnetometer lunar permeability study.

King, J. H.↗
NASA NTRS1979

SEM probe of IC radiation sensitivity

Scanning Electron Microscope (SEM) used to irradiate single integrated circuit (IC) subcomponent to test for radiation sensitivity can localize area of IC less than .03 by .03 mm for determination of exact location of radiation sensitive section.

Gauthier, M. K.↗