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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

The classical solution of a definite integral occurring in the satellite theory in the extended phase space

A method of integrating the functions defined by Scheifele and Graf (1974), arising in the elimination of time from the arguments of satellite theory using Delaunay elements in the extended phase space, is proposed. By repeated applications of an identity of Stiefel and Scheifele (1971), neglecting certain terms, and assuming a solution in the form of a product of Bessel functions, a solution expanded in the eccentricity is obtained.

Bond, V. R.↗
NASA NTRS1978

Contribution to solving the energy crisis - Simulating the prospects for low cost energy through silicon solar cells

PECAN (Photovoltaic Energy Conversion Analysis) is a highly interactive decision analysis and support system. It simulates the prospects for widespread use of solar cells for the generation of electrical power. PECAN consists of a set of integrated APL functions for evaluating the potential of terrestrial photovoltaics. Specifically, the system is a deterministic simulator, which translates present and future manufacturing technology into economic and financial terms, using the production unit concept. It guides solar cell development in three areas: tactical decision making, strategic planning, and the formulation of alternative options.

Kran, A.↗
NASA NTRS1979

Two-stream theory of reflectance of snow

Spectral reflectance of snow under diffuse illumination is studied using the two-stream approximation of the radiative transfer equation. The scattering and absorption parameters of the radiative transfer equation - the single scattering albedo, the optical depth, and the integrated phase function are obtained from the grain size and density of snow. Analytical expressions for the intensity within the snowpack, the reflectance, and the asymptotic flux extinction coefficient, are given. Good agreement is shown between the theory and available experimental data on visible and near-infrared reflectance, and the asymptotic flux extinction coefficient. The theory may also be used to explain the observed effect of aging on the snow reflectance.

Choudhury, B. J.↗
NASA NTRS1982

An accurate method for evaluating the kernel of the integral equation relating lift to downwash in unsteady potential flow

The method is capable of generating approximations of arbitrary accuracy. It is based on approximating the algebraic part of the nonelementary integrals in the kernel by exponential functions and then integrating termwise. The exponent spacing in the approximation is a geometric sequence. The coefficients and exponent multiplier of the exponential approximation are computed by least squares so the method is completely automated. Exponential approximates generated in this manner are two orders of magnitude more accurate than the exponential approximation that is currently most often used for this purpose. The method can be used to generate approximations to attain any desired trade-off between accuracy and computing cost.

Desmarais, R. N.↗
NASA NTRS1983

Interpretation of 2-probe turbulence measurements in an axisymmetric contraction

Simultaneous measurements of the streamwise and radial velocity components at two points, one on and one off the centerline with variable radial separation, were digitally recorded and processed at several stations along a four to one contraction with controlled upstream turbulence conditions. Various statistical quantities are presented including spectra and coherence functions. The integral L sub ux, L sub um, L sub vx, L sub vm were also estimated and their variation along the contraction is examined.

Marion-Moulin, C.↗
NASA NTRS1983

A theory of rotating stall of multistage axial compressors. III - Limit cycles

A theory of rotating stall, based on single parameters for blade-passage lag and external-flow lag and a given compressor characteristic yields limit cycles in velocity space. These limit cycles are governed by Lienard's equation with the characteristic playing the role of nonlinear damping function. Cyclic integrals of the solution determine stall propagation speed and the effect of rotating stall on average performance. Solution with various line-segment characteristics and various throttle settings are found and discussed. There is generally a limiting flow coefficient beyond which no solution is possible; this probably represents stall recovery. This recovery point is independent of internal compressor lag, but does depend on external lags and on the height-to-width ratio of the diagram. Tall diagrams and small external lags (inlet and diffusor) favor recovery. Suggestions for future theoretical and experimental research are discussed.

Moore, F. K.↗
NASA NTRS1984

Signal-to-noise ratio for the wide field-planetary camera of the Space Telescope

Signal-to-noise ratios for the Wide Field Camera and Planetary Camera of the Space Telescope were calculated as a function of integration time. Models of the optical systems and CCD detector arrays were used with a 27th visual magnitude point source and a 25th visual magnitude per arc-sq. second extended source. A 23rd visual magnitude per arc-sq. second background was assumed. The models predicted signal-to-noise ratios of 10 within 4 hours for the point source centered on a signal pixel. Signal-to-noise ratios approaching 10 are estimated for approximately 0.25 x 0.25 arc-second areas within the extended source after 10 hours integration.

Zissa, D. E.↗
NASA NTRS1984

The infrared properties of galaxy clusters - IRAS observations of the Hercules Cluster (Abell 2151)

A total of 41 sources have been detected at 60 microns to a level of 50 mJy in a 1.6 x 0.5 deg field centered on the rich galaxy cluster Abell 2151. Twenty-four of these sources can be identified with late-type spiral galaxies of estimated photographic magnitude 17 or brighter. Galaxies classified as E or S0 are notably absent in the infrared data. Within the field, eleven of the IRAS sources cannot be easily identified with galaxies in the Hercules Cluster. If the brightest 60 micron cluster source (NGC 6045) is neglected, the integral luminosity function in the far-infrared can be fitted well with two power laws of slope -1.1 and -2.5.

Young, E.↗
NASA NTRS1985

Airborne lidar measurements of El Chichon stratospheric aerosols, October 1982 to November 1982

A coordinated flight mission to determine the spatial distribution and aerosol characteristics of the El Chichon produced stratospheric aerosol was flown in October to November 1982. The mission covered 46 deg N to 46 deg S and included rendezvous between balloon-, airplane-, and satellite-borne sensors. The lidar data from the flight mission are presented. Representative profiles of lidar backscatter ratio, plots of the integrated backscattering function versus latitude, and contours of backscatter mixing ratio versus altitude and latitude are given. In addition, tables containing numerical values of the backscatter ratio and backscattering functions versus altitude are supplied for each profile. The bulk of the material produced by the El Chichon eruptions of late March 10 to early April 1982 resided between latitudes from 5 to 7 deg S to 35 to 37 deg N and was concentrated above 21 km in a layer that peaked at 23 to 25 km. In this latitude region, peak scattering ratios at a wavelength of 0.6943 micron were approximately 24. The results of this mission are presented in a ready-to-use format for atmospheric and climatic studies.

Mccormick, M. P.↗
NASA NTRS1985

SPAR improved structural-fluid dynamic analysis capability

The results of a study whose objective was to improve the operation of the SPAR computer code by improving efficiency, user features, and documentation is presented. Additional capability was added to the SPAR arithmetic utility system, including trigonometric functions, numerical integration, interpolation, and matrix combinations. Improvements were made in the EIG processor. A processor was created to compute and store principal stresses in table-format data sets. An additional capability was developed and incorporated into the plot processor which permits plotting directly from table-format data sets. Documentation of all these features is provided in the form of updates to the SPAR users manual.

Pearson, M. L.↗
NASA NTRS1985

Airborne lidar measurements of El Chichon stratospheric aerosols

A NASA Electra airplane, outfitted with a lidar system, was flown in January to February 1983 between the latitudes of 27 deg N and 76 deg N. One of the primary purposes of this mission was to determine the spatial distribution and aerosol characteristics of the El Chichon-produced stratospheric material. This report presents the lidar data from that flight mission. Representative profiles of lidar backscatter ratio, plots of the integrated backscattering function versus latitude, and contours of backscatter mixing ratio versus altitude and latitude are given. It addition, tables containing numerical values of the backscatter ratio and backscattering function versus altitude are supplied for each profile. The largest amount of material produced by the El Chichon eruptions of late March to early April 1982, which was measured by this flight, resided between 35 deg N and 52 deg N. Peak backscatter ratios at a wavelength of 0.6943 micro m decreased from 8 to 10 at the lower latitudes to 3 at the higher latitudes. Backscatter ratio profiles taken while crossing the polar vortex show that the high-altitude material from El Chichon arrived at the north polar region sometime after the winter polar vortex was established. This report presents the results of this mission in a ready-to-use format for atmospheric and climatic studies.

Mccormick, M. P.↗
NASA NTRS1986

Airborne lidar measurements of El Chichon stratospheric aerosols, May 1983

An experimental survey flight to determine the spatial distribution and aerosol characteristics of the El Chichon-produced stratospheric aerosol was conducted in May 1983. The mission included several different sensors flown abroad the NASA Convair 990 at latitudes between 72 deg. and 56 deg. S. This report presents the lidar data from that flight mission. Representative profiles of lidar backscatter ratio, plots of integrated backscattering function versus latitude, and contours of backscatter mixing ratio versus altitude and latitude are given. In addition, tables containing numerical values of the backscatter ratio and backscattering function versus altitude are supplied for each profile. By May 1983, material produced by the El Chichon eruptions of late March-early April 1982 had spread throughout the latitudes covered by this mission. However, the most massive portion of the material resided north of 33 deg. N and was concentrared below 21 km. In this latitude region (33 deg. N to 72 deg. N), peak backscatter ratios at a wavelength of 0.6943 microns varied between 3.5 and 4.5, and the peak integratred backscattering function was about 18 X 10 to the -4 power/sr, corresponding to a peak optical depth calculated to be approximately 0.08. This report presents the results of this mission in a ready-to-use format for atmospheric and climatic studies.

Mccormick, M. P.↗
NASA NTRS1986

JPL pyro shock test approaches and results

This paper presents the overall approach at JPL in performing spacecraft pyrotechnic shock qualification testing. Initially, the assembly shock requirements are developed early in the program based on previous spacecraft test experience and data. Pyrotechnic device development testing firings and spacecraft Development Test Model (DTM) pyro firings are then conducted to verify the adequacy of the assembly shock requirements and to determine the subsystem test firing and the subsequent system level test firing requirements. The electro-dynamic shaker, through shock synthesis techniques, is utilized to qualify the shock sensitive flight equipment with margins applied. Actual pyrotechnic device firings on spacecraft equipment or science instruments are performed when the influence of the pyros is localized and can be ignored at the system level. Full spacecraft system level shock tests, which include multiple firings of certain critical pyro devices, are conducted to verify the spacecraft design structural integrity and functions as well as to qualify hardware items which have not been previously qualified. These tests also provide a source of data from which assembly level requirements can be evaluated and compared. For example, during the Galileo program, the results demonstrated that good agreement between predicted and measured shock environments and adequate qualification of the flight spacecraft was achieved.

Chang, Kurng Y.↗
NASA NTRS1987

Inflight microbial analysis technology

This paper provides an assessment of functional characteristics needed in the microbial water analysis system being developed for Space Station. Available technology is reviewed with respect to performing microbial monitoring, isolation, or identification functions. An integrated system composed of three different technologies is presented.

Pierson, Duane L.↗
NASA NTRS1988

Transformational derivation of programs using the Focus system

A program derivation support system called Focus is being constructed. It will formally derive programs using the paradigm of program transformation. The following issues are discussed: (1) the integration of validation and program derivation activities in the Focus system; (2) its tree-based user interface; (3) the control of search spaces in program derivation; and (4) the structure and organization of program derivation records. The inference procedures of the system are based on the integration of functional and logic programming principles. This brings about a synthesis of paradigms that were heretofore considered far apart, such as logical and executable specifications and constructive and transformational approaches to program derivation. A great emphasis has been placed, in the design of Focus, on achieving small search spaces during program derivation. The program manipulation operations such as expansion, simplification and rewriting were designed with this objective. The role of operations that are expensive in search spaces, such as folding, has been reduced. Program derivations are documented in Focus in a way that the high level descriptions of derivations are expressed only using program level information. All the meta-level information, together with dependencies between derivations of program components, is automatically recorded by the system at a lower level of description for its own use in replay.

Reddy, Uday S.↗
NASA NTRS1989

Bio-regenerative life support

The basis for and the potential uses of bio-regenerative life support are examined. Bio-regenerative life support systems are an alternative to physical-chemical regeneration techniques for use when resupply of a crew in space is expensive, or when the logistics of resupply are difficult. Many of the scientific studies required for bio-regenerative life support systems have been completed and preliminary development of some components will begin within the next 12 to 18 months. The focus of the work that lies ahead will be efficient power and mass use, long-term system stability, component function, systems integration, and extensive testing in the space environment. Because of the advantages of bio-regeneration, it is anticipated that human life support for long-term space missions will evolve to include increasingly large amounts of biologically-based regeneration.

Macelroy, Robert D.↗
NASA NTRS1989

Vortex paradigm for shock-accelerated density-stratified interfaces

Numerical simulations are reported that capture the observations of Haas and Sturtevant (1985) when a planar shock accelerates an inclined planar interface between two media. A vortex paradigm is presented for interpreting the evolution of shock-accelerated density-stratified interfaces beyond early times. The simulations illustrate the paradigm and are in good agreement with the results of Haas and Sturtevant. Color images of space-time diagrams of the one-space integrated vorticity function are given to show the primary and secondary features of the emerging vortex structures.

Hawley, John F.↗
NASA NTRS1989

A system architecture for a planetary rover

Each planetary mission requires a complex space vehicle which integrates several functions to accomplish the mission and science objectives. A Mars Rover is one of these vehicles, and extends the normal spacecraft functionality with two additional functions: surface mobility and sample acquisition. All functions are assembled into a hierarchical and structured format to understand the complexities of interactions between functions during different mission times. It can graphically show data flow between functions, and most importantly, the necessary control flow to avoid unambiguous results. Diagrams are presented organizing the functions into a structured, block format where each block represents a major function at the system level. As such, there are six blocks representing telecomm, power, thermal, science, mobility and sampling under a supervisory block called Data Management/Executive. Each block is a simple collection of state machines arranged into a hierarchical order very close to the NASREM model for Telerobotics. Each layer within a block represents a level of control for a set of state machines that do the three primary interface functions: command, telemetry, and fault protection. This latter function is expanded to include automatic reactions to the environment as well as internal faults. Lastly, diagrams are presented that trace the system operations involved in moving from site to site after site selection. The diagrams clearly illustrate both the data and control flows. They also illustrate inter-block data transfers and a hierarchical approach to fault protection. This systems architecture can be used to determine functional requirements, interface specifications and be used as a mechanism for grouping subsystems (i.e., collecting groups of machines, or blocks consistent with good and testable implementations).

Smith, D. B.↗