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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 649 records · Page 36
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NASA NTRS1978

User's manual: Subsonic/supersonic advanced panel pilot code

Sufficient instructions for running the subsonic/supersonic advanced panel pilot code were developed. This software was developed as a vehicle for numerical experimentation and it should not be construed to represent a finished production program. The pilot code is based on a higher order panel method using linearly varying source and quadratically varying doublet distributions for computing both linearized supersonic and subsonic flow over arbitrary wings and bodies. This user's manual contains complete input and output descriptions. A brief description of the method is given as well as practical instructions for proper configurations modeling. Computed results are also included to demonstrate some of the capabilities of the pilot code. The computer program is written in FORTRAN IV for the SCOPE 3.4.4 operations system of the Ames CDC 7600 computer. The program uses overlay structure and thirteen disk files, and it requires approximately 132000 (Octal) central memory words.

Moran, J.↗
NASA NTRS1986

BIOASPEN: System for technology development

The public version of ASPEN was installed in the VAX 11/750 computer. To examine the idea of BIOASPEN, a test example (the manufacture of acetone, butanol, and ethanol through a biological route) was chosen for simulation. Previous reports on the BIOASPEN project revealed the limitations of ASPEN in modeling this process. To overcome some of the difficulties, modules were written for the acid and enzyme hydrolyzers, the fermentor, and a sterilizer. Information required for these modules was obtained from the literature whenever possible. Additional support modules necessary for interfacing with ASPEN were also written. Some of ASPEN subroutines were themselves altered in order to ensure the correct running of the simulation program. After testing of these additions and charges was completed, the Acetone-Butanol-Ethanol (ABE) process was simulated. A release of ASPEN (which contained the Economic Subsystem) was obtained and installed. This subsection was tested and numerous charges were made in the FORTRAN code. Capital investment and operating cost studies were performed on the ABE process. Some alternatives in certain steps of the ABE simulation were investigated in order to elucidate their effects on the overall economics of the process.

Source record↗
NASA NTRS1973

Automated procedure for design of wing structures to satisfy strength and flutter requirements

A pilot computer program was developed for the design of minimum mass wing structures under flutter, strength, and minimum gage constraints. The wing structure is idealized by finite elements, and second-order piston theory aerodynamics is used in the flutter calculation. Mathematical programing methods are used for the optimization. Computation times during the design process are reduced by three techniques. First, iterative analysis methods used to reduce significantly reanalysis times. Second, the number of design variables is kept small by not using a one-to-one correspondence between finite elements and design variables. Third, a technique for using approximate second derivatives with Newton's method for the optimization is incorporated. The program output is compared witH previous published results. It is found that some flutter characteristics, such as the flutter speed, can display discontinous dependence on the design variables (which are the thicknesses of the structural elements). It is concluded that it is undesirable to use such quantities in the formulation of the flutter constraint.

Haftka, R. T.↗
NASA NTRS1973

Earth and Ocean Physics Applications Program /EOPAP/

Abbreviated description of the objectives, experiments, spacecraft, and required schedules of a proposed NASA program blending geophysics, oceanography, and space technology in order to facilitate the prediction of earthquakes, storm surges, tidal waves, and the condition of ocean surfaces. Relevant measurements from space will be carried out by LAGEOS, SAESATS-1, GEOPAUSE, GRAVSAT, and SEASATS-2 satellites contributing data on earth dynamics, sea surface states, satellite dynamics, and earth gravity. The development of suitable mathematical models for predicting events on earth on the basis of satellite data is considered.

Vonbun, F. O.↗
NASA NTRS1974

Square-root algorithm for evaluating mismodeled process noise

As the application of sequential filters has grown, the need has arisen to evaluate the sensitivity of these filters to mismodeling of the random process. A numerically reliable square-root algorithm is developed for calculating the covariances of estimates from a sequential filter which incorrectly models process noise. Mismodeling is restricted to the correlation time and standard deviation of a random process represented as a first-order Gauss-Markov sequence. Using a computer program which employs this algorithm, a sensitivity analysis was performed for several types of earth-based tracking data from an interplanetary spacecraft.

Thornton, C. L.↗
NASA NTRS1975

Radiation of cylindrical duct acoustic modes with flow mismatch

Calculations for the radiation of spinning acoustic modes, with or without a centerbody, and with or without flow temperature and velocity discontinuity, are presented. Solutions to the appropriate convected wave equations devised around Fourier transforms and Wiener-Hopf technique are presented. The decomposition of the asymmetric kernel, resulting from a flow and temperature mismatch, is carried out in part exactly and partially using the so-called Carrier-Koiter approximation procedure. The resulting solutions offer a good approximation to the radiation of both symmetric and asymmetric modes through a flow discontinuity represented as a plug flow jet issuing from a cylindrical duct. Besides the Koiter approximation, the major limitation on the calculation program is the difficulty of calculating the high order Bessel functions with sufficient accuracy.

Savkar, S. D.↗
NASA NTRS1975

Study of shuttle imaging microwave system antenna. Volume 1: Conceptual design

A detailed preliminary design and complete performance evaluation are presented of an 11-channel large aperture scanning radiometer antenna for the shuttle imaging microwave system (SIMS) program. Provisions for interfacing the antenna with the space shuttle orbiter are presented and discussed. A program plan for hardware development and a rough order of magnitude (ROM) cost are also included. The conceptual design of the antenna is presented. It consists of a four-meter diameter parabolic torus main reflector, which is a graphite/epoxy shell supported by a graphite/epoxy truss. A rotating feed wheel assembly supports six Gregorian subreflectors covering the upper eight frequency channels from 6.6 GHz through 118.7 GHz, and two three-channel prime forms feed assemblies for 0.6, 1.4, and 2.7 GHz. The feed wheel assembly also holds the radiometers and power supplies, and a drive system using a 400 Hz synchronous motor is described. The RF analysis of the antenna is performed using physical optics procedures for both the dual reflector Gregorian concept and the single reflector prime focus concept. A unique aberration correcting feed for 2.7 GHz is analyzed. A structural analysis is also included. The analyses indicate that the antenna will meet system requirements.

Wesley, R. W.↗
NASA NTRS1975

EMGAN: A computer program for time and frequency domain reduction of electromyographic data

An experiment in electromyography utilizing surface electrode techniques was developed for the Apollo-Soyuz test project. This report describes the computer program, EMGAN, which was written to provide first order data reduction for the experiment. EMG signals are produced by the membrane depolarization of muscle fibers during a muscle contraction. Surface electrodes detect a spatially summated signal from a large number of muscle fibers commonly called an interference pattern. An interference pattern is usually so complex that analysis through signal morphology is extremely difficult if not impossible. It has become common to process EMG interference patterns in the frequency domain. Muscle fatigue and certain myopathic conditions are recognized through changes in muscle frequency spectra.

Hursta, W. N.↗
NASA NTRS1978

Identification of the stability parameters of an aeroelastic airplane

Phase variable transformations are used to construct the mathematical model of an aeroelastic aircraft in a form that is amenable to partial or piecemeal acceptance of parameters estimated from flight data. The problem is one of parameter identification of large scale dynamic systems involving a system matrix characterized by about 200 elements. A mathematical model of the USAF Total In-Flight Simulator was computed using the FLEXSTAB program. As data became available during the progress of the flight test program, it was processed and substituted in the mathematical model for parameters obtained from the FLEXSTAB program. Results tend to show a progressive and orderly transition from an analytically defined mathematical model to one obtained from the flight tests of the actual aircraft.

Rynaski, E. G.↗
NASA NTRS1981

Application of constrained optimization to active control of aeroelastic response

Active control of aeroelastic response is a complex in which the designer usually tries to satisfy many criteria which are often conflicting. To further complicate the design problem, the state space equations describing this type of control problem are usually of high order, involving a large number of states to represent the flexible structure and unsteady aerodynamics. Control laws based on the standard Linear-Quadratic-Gaussian (LQG) method are of the same high order as the aeroelastic plant. To overcome this disadvantage of the LQG mode, an approach developed for designing low order optimal control laws which uses a nonlinear programming algorithm to search for the values of the control law variables that minimize a composite performance index, was extended to the constrained optimization problem. The method involves searching for the values of the control law variables that minimize a basic performance index while satisfying several inequality constraints that describe the design criteria. The method is applied to gust load alleviation of a drone aircraft.

Newsom, J. R.↗
NASA NTRS1980

Cardiovascular responses to static exercise in distance runners and weight lifters

Three groups of athletes including long-distance runners, competitive and amateur weight lifters, and age- and sex-matched control subjects have been studied by hemodynamic and echocardiographic methods in order to determine the effect of the training programs on the cardiovascular response to static exercise. Blood pressure, heart rate, and double product data at rest and at fatigue suggest that competitive endurance (dynamic exercise) training alters the cardiovascular response to static exercise. In contrast to endurance exercise, weight lifting (static exercise) training does not alter the cardiovascular response to static exercise: weight lifters responded to static exercise in a manner very similar to that of the control subjects.

Longhurst, J. C.↗
NASA NTRS1982

Linearized transfer between coplanar circular orbits using blow down propulsion system

A closed form solution is presented for the coplanar transfer between nearby circular orbits for spacecraft using their own blow down propulsion system. The decaying thrust is applied along the local horizontal and the linearized equation of motion in the orbital elements formulation are used to describe the transfer which consists of a thrust-coast-relight program. Sensitivity partials are also presented analytically in order to study the effect of maneuver execution errors and various other parameters affecting the blow down propulsion system characteristics on the transfer. This strategy is applied to study the transfer of the TOPEX spacecraft from the Shuttle parking orbit to its final operational orbit.

Kechichian, J. A.↗
NASA NTRS1983

Planar dynamics of a uniform beam with rigid bodies affixed to the ends

The planar dynamics of a uniform elastic beam subject to a variety of geometric and natural boundary conditions and external excitations were analyzed. The beams are inextensible and capable of small transverse bending deformations only. Classical beam vibration eigenvalue problems for a cantilever with tip mass, a cantilever with tip body and an unconstrained beam with rigid bodies at each are examined. The characteristic equations, eigenfunctions and orthogonality relations for each are derived. The forced vibration of a cantilever with tip body subject to base acceleration is analyzed. The exact solution of the governing nonhomogeneous partial differential equation with time dependent boundary conditions is presented and compared with a Rayleigh-Ritz approximate solution. The arbitrary planar motion of an elastic beam with rigid bodies at the ends is addressed. Equations of motion are derived for two modal expansions of the beam deflection. The motion equations are cast in a first order form suitable for numerical integration. Selected FORTRAN programs are provided.

Storch, J.↗
NASA NTRS1986

Supercomputer implementation of finite element algorithms for high speed compressible flows

Prediction of compressible flow phenomena using the finite element method is of recent origin and considerable interest. Two shock capturing finite element formulations for high speed compressible flows are described. A Taylor-Galerkin formulation uses a Taylor series expansion in time coupled with a Galerkin weighted residual statement. The Taylor-Galerkin algorithms use explicit artificial dissipation, and the performance of three dissipation models are compared. A Petrov-Galerkin algorithm has as its basis the concepts of streamline upwinding. Vectorization strategies are developed to implement the finite element formulations on the NASA Langley VPS-32. The vectorization scheme results in finite element programs that use vectors of length of the order of the number of nodes or elements. The use of the vectorization procedure speeds up processing rates by over two orders of magnitude. The Taylor-Galerkin and Petrov-Galerkin algorithms are evaluated for 2D inviscid flows on criteria such as solution accuracy, shock resolution, computational speed and storage requirements. The convergence rates for both algorithms are enhanced by local time-stepping schemes. Extension of the vectorization procedure for predicting 2D viscous and 3D inviscid flows are demonstrated. Conclusions are drawn regarding the applicability of the finite element procedures for realistic problems that require hundreds of thousands of nodes.

Thornton, E. A.↗
NASA NTRS1985

Space Shuttle navigation validation

The validation of the guidance, navigation, and control system of the Space Shuttle is explained. The functions of the ascent, on-board, and entry mission phases software of the navigation system are described. The common facility testing, which evaluates the simulations to be used in the navigation validation, is examined. The standard preflight analysis of the operational modes of the navigation software and the post-flight navigation analysis are explained. The conversion of the data into a useful reference frame and the use of orbit parameters in the analysis of the data are discussed. Upon entry the data received are converted to flags, ratios, and residuals in order to evaluate performance and detect errors. Various programs developed to support navigation validation are explained. A number of events that occurred with the Space Shuttle's navigation system are described.

Ragsdale, A.↗
NASA NTRS1985

Scientific requirements for a Moderate-Resolution Imaging Spectrometer (MODIS) for EOS

The MODIS is an instrument planned for the sun-synchronous polar orbiting segment of the Space Station system. The radiometer is required to have 1 km resolution in terrestrial remote sensing applications. The monitoring program is targeted to last 10 yr in order to provide a sufficient database for discerning trends as opposed to natural variations. The study areas of interest include tropical deforestation, regrowth and areal distributions, acid rain effects on northern forests, desertification rates and locations, snow cover/albedo relationships and total biomass. MODIS will have 192 channels with 30 m spatial resolution and cover seven bands in the 3.5-12 microns interval for land viewing. Ocean studies will be carried out in 17 bands from 0.4-1.0 micron, and atmospheric scans will be performed over the land and ocean intervals at narrowband wavelengths (1.2 nm). Si detector arrays will be used and will be accompanied by an expected 600:1 SNR and produce data at a rate of 1.4-9.1 Mb/sec.

Barnes, W. L.↗
NASA NTRS1986

Development testing of large volume water sprays for warm fog dispersal

A new brute-force method of warm fog dispersal is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray induced air flow. Fog droplets are removed by coalescence/rainout. The efficiency of the technique depends upon the drop size spectra in the spray, the height to which the spray can be projected, the efficiency with which fog laden air is processed through the curtain of spray, and the rate at which new fog may be formed due to temperature differences between the air and spray water. Results of a field test program, implemented to develop the data base necessary to assess the proposed method, are presented. Analytical calculations based upon the field test results indicate that this proposed method of warm fog dispersal is feasible. Even more convincingly, the technique was successfully demonstrated in the one natural fog event which occurred during the test program. Energy requirements for this technique are an order of magnitude less than those to operate a thermokinetic system. An important side benefit is the considerable emergency fire extinguishing capability it provides along the runway.

Keller, V. W.↗
NASA NTRS1989

The filters for the Extreme Ultraviolet Explorer - Calibration and lifetesting results

The results of the transmission calibrations of the seven sets of flight integration filters for the Extreme Ultraviolet Explorer (EUVE) satellite are presented. The Berkely EUV Calibration Facility was used to determine absolute transmissions over six orders of magnitue at 28 wavelengths. A lifetesting program designed to monitor changes in the transmission and mechanical properties of the EUVE filters over the lifetime of the mission is described.

Vedder, P. W.↗