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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Analytical evaluation of ILM sensors. Volume 2: Appendices

The applicability of various sensing concepts to independent landing monitor systems was analyzed. Microwave landing system MLS accuracy requirements are presented along with a description of MLS airborne equipment. Computer programs developed during the analysis are described and include: a mathematical computer model for use in the performance assessment of reconnaissance sensor systems; a theoretical formulation of electromagnetic scattering to generate data at high incidence angles; atmospheric attenuation of microwaves; and microwave radiometry, programs

Kirk, R. J.↗
NASA NTRS1975

Ride quality of terminal-area flight maneuvers

Complex terminal-area flight maneuvers being considered for airline operations may not be acceptable to passengers. To provide technology in this area, a series of flight experiments was conducted by NASA using the U. S. Air Force Total In-Flight Simulator (TIFS) aircraft to obtain subjective responses of a significant number of passenger test subjects to closely controlled and repeatable flight maneuvers. Regression analysis of the data produced a mathematical model which closely predicts mean passenger ride-comfort rating as a function of the rms six-degree-of-freedom aircraft motions during the maneuver. This ride-comfort model was exercised to examine various synthesized flight maneuvers.

Schoonover, W. E., Jr.↗
NASA NTRS1978

A general panel sizing computer code and its application to composite structural panels

A computer code for obtaining the dimensions of optimum (least mass) stiffened composite structural panels is described. The procedure, which is based on nonlinear mathematical programming and a rigorous buckling analysis, is applicable to general cross sections under general loading conditions causing buckling. A simplified method of accounting for bow-type imperfections is also included. Design studies in the form of structural efficiency charts for axial compression loading are made with the code for blade and hat stiffened panels. The effects on panel mass of imperfections, material strength limitations, and panel stiffness requirements are also examined. Comparisons with previously published experimental data show that accounting for imperfections improves correlation between theory and experiment.

Anderson, M. S.↗
NASA NTRS1979

Design, processing and testing of LSI arrays: Hybrid microelectronics task

Mathematical cost factors were generated for both hybrid microcircuit and printed wiring board packaging methods. A mathematical cost model was created for analysis of microcircuit fabrication costs. The costing factors were refined and reduced to formulae for computerization. Efficient methods were investigated for low cost packaging of LSI devices as a function of density and reliability. Technical problem areas such as wafer bumping, inner/outer leading bonding, testing on tape, and tape processing, were investigated.

Himmel, R. P.↗
NASA NTRS1982

Optical communications research to demonstrate 2.5 bits/detected photon

The transmission of information by optical signals over a space channel with a power efficiency of 2.5 bits/detected photon markedly increases the amount of information that can be transmitted to satellites. An account is given of the research program at the Jet Propulsion Laboratory that is attempting to demonstrate that optical signals can be used to transmit information over a space channel with this power efficiency. It is noted, however, that the ability to attain 2.5 bits/detected photon (or higher) depends heavily on the validity of the mathematical models used in the performance analysis. Therefore, verification of the channel dark current noise models is a crucial first step. Another prerequisite is a high-brightness, single-spatial mode laser emitter. It is believed that single spatial model devices with power outputs of about 1W can be achieved by coherently combining a number of GaAs lasers in what effectively amounts to a phased array.

Lesh, J. R.↗
NASA NTRS1984

Economic impact of fuel properties on turbine powered business aircraft

The principal objective was to estimate the economic impact on the turbine-powered business aviation fleet of potential changes in the composition and properties of aviation fuel. Secondary objectives include estimation of the sensitivity of costs to specific fuel properties, and an assessment of the directions in which further research should be directed. The study was based on the published characteristics of typical and specific modern aircraft in three classes; heavy jet, light jet, and turboprop. Missions of these aircraft were simulated by computer methods for each aircraft for several range and payload combinations, and assumed atmospheric temperatures ranging from nominal to extremely cold. Five fuels were selected for comparison with the reference fuel, nominal Jet A. An overview of the data, the mathematic models, the data reduction and analysis procedure, and the results of the study are given. The direct operating costs of the study fuels are compared with that of the reference fuel in the 1990 time-frame, and the anticipated fleet costs and fuel break-even costs are estimated.

Powell, F. D.↗
NASA NTRS1984

Study on spectral/radiometric characteristics of the Thematic Mapper for land use applications

Progress under the LANDSAT-4 and 5 Image Data Quality Assessment program for the Thematic Mapper is described. An initial screening of LANDSAT-5 data is performed. Tools are developed to allow access to TIPS-format data. Analysis of scan direction related signal droop is resumed with detailed analysis of nighttime data. A new mathematical model is developed to describe the effect. Coherent noise of a lower frequency than previously reported is discovered and analyzed. Coincident LANDSAT-4 TM and MSS data are analyzed to improve understanding of radiometric relationships between similar wavebands in the two sensors.

Malila, W. A.↗
NASA NTRS1985

Computer simulation studies in fluid and calcium regulation and orthostatic intolerance

The systems analysis approach to physiological research uses mathematical models and computer simulation. Major areas of concern during prolonged space flight discussed include fluid and blood volume regulation; cardiovascular response during shuttle reentry; countermeasures for orthostatic intolerance; and calcium regulation and bone atrophy. Potential contributions of physiologic math models to future flight experiments are examined.

Source record↗
NASA NTRS1985

Study of one- and two-dimensional filtering and deconvolution algorithms for a streaming array computer

The development of vector processing computers of the streaming array architectures has made possible a dramatic decrease in the time required for the solution of problems, i.e., for those algorithms which readily lend themselves to sequential operations on long vectors. There has concurrently been rapid growth in the applications of the techniques generally known as mathematical digital filtering, also called signal analysis, digital signal processing, time series analysis, and digital image processing. The best known applications of these techniques is to seismic data and two-dimensional images, data types consisting of very large collections of numbers. A major limitation for these cases is the size and speed of the computer available. Therefore, a move to the streaming array architecture can result in marked improvement in the data analysis techniques which may be employed.

Ioup, G. E.↗
NASA NTRS1985

Experimental evaluation of damping of graphite fiber composites

An investigation is described that was conducted to measure the damping of graphite fiber composites such as are to be used on the Hubble Space Telescope. The measurements were made on a composite cylinder under normal atmospheric conditions and in a vacuum chamber with varying thermal conditions. Such composites can outgas under vacuum conditions and this emission of trapped gases may have some influence on the material damping. Some results are presented for the damping coefficient measured under normal atmospheric conditions for a graphite fiber composite. The experimental damping data thus obtained were compared with the least square estimate obtained through a statistical analysis. The statistical analysis was based on a linear mathematical model consisting of a spring in parallel with a dashpot. It is observed that the discrepancy in the damping ratio between logarithmic decrement result and the least square fit is less than 6 percent for all the different tests made on the composite cylinder. Signal-to-noise ratio was maintained to be greater than 10.

Rao, M. D.↗
NASA NTRS1987

Predicting Close Satellite Encounters

Method for predicting probabilities of collisions between nominally geosynchronous satellites gives results without large computer resources. Realistically assesses possibility of collision between expired, drifting satellite and active, station-keeping satellite. Mathematical techniques in paper useful in analysis of such terrestrial risks as floods and nuclear accidents.

Mccormick, B. R.↗
NASA NTRS1986

Orbital flight simulation utility software unit specifications

The HP PASCAL source code contained in pages 6 through 104 was developed for the Mission Planning and Analysis Division (MPAD) and takes the place of detailed flow charts defining the specifications for a Utility Software Unit designed to support orbital flight simulators such as MANHANDLE and GREAS (General Research and Engineering Analysis Simulator). Besides providing basic input/output, mathematical, vector, matrix, quaternion, and statistical routines for such simulators, one of the primary functions of the Utility Software Unit is to isolate all system-dependent code in one well-defined compartment, thereby facilitating transportation of the simulations from one computer to another. Directives to the PASCAL compilers of the HP-9000 Series 200 PASCAL 3.0 operating system and the HP-9000 Series 500 HP-UX 5.0 operations systems are also provided.

Wilson, S. W.↗
NASA NTRS1986

Orbital flight simulation utility software unit specifications, revision 1

The HP PASCAL source code defines the specifications for a Utility Software Unit (USU) designed to support orbital flight simulators such as MANHANDLE and GREAS (General Research and Engineering Analysis Simulator). Besides providing basic input/output, mathematical, matrix, quaternion, and statistical routines for such simulators, one of the primary functions of the USU is to isolate all system-dependent codes in one well-defined compartment, thereby facilitating transportation of the simulations from one computer to another. Directives are given for the PASCAL compilers of the HP-9000 Series 200 Pascal 3.0 and the HP-9000 Series 500 HP-UX 5.0 operating systems that produce a single file of relocatable code from four separate files of source code. Three of the source code files are common to both operating systems. The fourth source code file (utilspif.I) contains all of the system-dependent PASCAL code for the USU. A fifth file of source code written in C is required to interface utilspif.I with the HP-UX I/O package. The Pascal 3.0 compiler directives and the driver source code for a unit rest program and counterparts for the HP-UX 5.0 operating system are given. The major portion of the unit test program source code is common to both operating systems. Unit test results from the Pascal 3.0 operating system and results from the HP-UX operating system are given.

Wilson, S. W.↗
NASA NTRS1988

Non-isothermal elastoviscoplastic analysis of planar curved beams

The development of a general mathematical model and solution methodologies, to examine the behavior of thin structural elements such as beams, rings, and arches, subjected to large nonisothermal elastoviscoplastic deformations is presented. Thus, geometric as well as material type nonlinearities of higher order are present in the analysis. For this purpose a complete true abinito rate theory of kinematics and kinetics for thin bodies, without any restriction on the magnitude of the transformation is presented. A previously formulated elasto-thermo-viscoplastic material constitutive law is employed in the analysis. The methodology is demonstrated through three different straight and curved beams problems.

Simitses, G. J.↗
NASA NTRS1987

Development of a generic combustion stability code for liquid propellant rocket engines

The mathematical framework for a combustion stability analysis code is outlined. The goal for the code is to be general enough in problem treatment so that its validity and accuracy extend over a wide range of problem applications and that it lends the convenience for any future model improvement if necessary. An approach for modeling the combustion dynamics is devised to meet both requirements. An open-loop numerical procedure is also developed to mechanistically model various combustion processes for determining the stability parameters.

Fang, J. J.↗
NASA NTRS1988

Large Deployable Reflector (LDR) thermal characteristics

The thermal support group, which is part of the lightweight composite reflector panel program, developed thermal test and analysis evaluation tools necessary to support the integrated interdisciplinary analysis (IIDA) capability. A detailed thermal mathematical model and a simplified spacecraft thermal math model were written. These models determine the orbital temperature level and variation, and the thermally induced gradients through and across a panel, for inclusion in the IIDA.

Miyake, R. N.↗
NASA NTRS1991

Constraints on the physical properties of optical bullets in SS 433

The present study discusses possible mechanisms for continuously heating the H-alpha emitting bullets of SS 433 out to distances of 5 x 10 to the 14th cm and for turning off this emission at 10 to the 15th. Various observational contraints are used to establish bounds on permissible solutions in terms of the two key bullet parameters, mass, and angular radius seen from the central source. The analysis is carried out for the mathematically simplest case of uniform spherical bullets. For radiative heat of such bullets by starlight, solutions are found to exist only for the very massive bullets with about 0.03 radians, which are highly implausible on the grounds of the large implied mean kinetic luminosity of about 10 to the 41st ergs/s. It is concluded that collisional interaction is the most likely mechanism for heating the optical bullets of SS 433. The effects of these constraints being fragmented rather than uniform, and being elongated rather than spherical are discussed.

Brown, John C.↗