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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 325 records · Page 18
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NASA NTRS1974

Analytical model for liquid rocket propellant feedline dynamics

A generalized analytical model and computer program have been developed to predict the frequency response of arbitrary liquid propellant feedline designs. The analytical model is based on an extension of an existing distributed parameter representation of a viscous fluid transmission line with laminar flow which was modified to include the effects of a turbulent mean flow. The effects of dissolved ullage gases, wall elasticity, localized gas or vapor bubbles, bellows, forced changes in length due to structural excitation, complex side branches, and structural mounting stiffness are also included. Each line component is written as a four-terminal, pressure-flow relationship in matrix form in the Laplace domain; the transfer function relating the pressure response at the line terminal (inducer inlet) to the external excitation is obtained in the computer program by sequential matrix substitution.

Holster, J. L.↗
NASA NTRS1974

Analytic variational calculation of the ground-state binding energy of hydrogen in intermediate and intense magnetic fields

The present work investigates analytically the effect of an intermediate or intense magnetic field, such as probably exist in white dwarfs and near pulsars, on the binding energy of the hydrogen ground state. A wave-function 'prescription' is given for an analytic variational calculation of the binding energy. The calculation still gives a smooth transition between intermediate and intense fields. An explicit calculation of the ground-state binding energy as B goes to infinity is provided for the Yafet et al. (1956) trial function.

Wilson, L. W.↗
NASA NTRS1974

Analytical satellite theories based on a new set of canonical elements

A new analytical satellite theory is presented. Instead of the 6 classical elements of Delaunay, a set of 8 canonical elements is used. Whereas the time is the independent variable in classical theory, the true anomaly is the independent variable in the new theory. The new approach has four features: (1) The amount of formulas in the solution is reduced considerably. (2) The first order results are almost as accurate as second order results in classical theory. (3) The theory is easier to understand from a didactical point of view. (4) The problems connected with the inaccuracy of the mean motion that are typical for classical satellite theory are no longer present. The new elements are applied to analytical solutions of the zonal oblateness problem and to the problem of the 24 hour satellite.

Scheifele, G.↗
NASA NTRS1974

Analytic pulsar models

An analytical procedure is given for solving the Einstein equations of a rotating fluid body. It is demonstrated that an analytic model of uniform denisty, representing a slowly rotating neutron star, can describe both differentially and uniformly rotating stars.

Adams, R. C.↗
NASA NTRS1975

Experimental and analytical sonic nozzle discharge coefficients for Reynolds numbers up to 8 x 10 to the 6th power

Sonic discharge coefficients are obtained for two different geometry flow nozzles using high-pressure nitrogen gas (100 atm) with significant real-gas flow corrections. Throat Reynolds number range extended up to 8 million. Discharge coefficients for both nozzles monotonically increase in value at the high throat Reynolds numbers. The 95-percent confidence band for each nozzle is shown. Analytical discharge coefficients for the continuous and finite radius of curvature nozzle are presented. These analytical results for the laminar and turbulent boundary-layer cases are compared to experimental values for sonic flow. Experimental values are also compared to values calculated from the best empirical curve fit equation for subsonic flow.

Szaniszlo, A. J.↗
NASA NTRS1975

An analytical evaluation of airfoil sections for helicopter rotor applications

An analytical technique was used to evaluate airfoils for helicopter rotor application. This technique permits assessment of the influences of airfoil geometric variations on drag divergence Mach number at lift coefficients from near zero to near maximum lift. Analytical results presented in this paper indicate the compromises in drag divergence Mach number which result from changes in (1) thickness ratio, (2) location of maximum thickness, (3) leading-edge radius, (4) camber addition, and (5) location of maximum camber of NACA four- and five-digit-series airfoils and some 6-series airfoils of potential interest for helicopters. Examples of airfoil sections which combine several of the geometric changes favorable to both advancing and retreating section performance have been presented.

Bingham, G. J.↗
NASA NTRS1974

Analytical and experimental investigation of a 1/8-scale dynamic model of the shuttle orbiter. Volume 1: Summary report

A 1/8-scale structural dynamics model of the space shuttle orbiter was analyzed using the NASA Structural Analysis System (NASTRAN). Comparison of the calculated eigenvalues with preliminary test data for the unrestrained condition indicate that the analytical model was consistently stiffer, being about 20% higher in the first mode. The eigenvectors show reasonably good agreement with test data. A series of analytical and experimental investigations undertaken to resolve the discrepancy are described. Modifications in the NASTRAN model based upon these investigations resulted in close agreement for both eigenvalues and eigenvectors.

Mason, P. W.↗
NASA NTRS1975

Analytic and experimental evaluation of flowing air test conditions for selected metallics in a shuttle TPS application

A detailed experimental and analytical evaluation was performed to define the response of TD nickel chromium alloy (20 percent chromium) and coated columbium (R512E on CB-752 and VH-109 on WC129Y) to shuttle orbiter reentry heating. Flight conditions important to the response of these thermal protection system (TPS) materials were calculated, and test conditions appropriate to simulation of these flight conditions in flowing air ground test facilities were defined. The response characteristics of these metallics were then evaluated for the flight and representative ground test conditions by analytical techniques employing appropriate thermochemical and thermal response computer codes and by experimental techniques employing an arc heater flowing air test facility and flat face stagnation point and wedge test models. These results were analyzed to define the ground test requirements to obtain valid TPS response characteristics for application to flight. For both material types in the range of conditions appropriate to the shuttle application, the surface thermochemical response resulted in a small rate of change of mass and a negligible energy contribution. The thermal response in terms of surface temperature was controlled by the net heat flux to the surface; this net flux was influenced significantly by the surface catalycity and surface emissivity. The surface catalycity must be accounted for in defining simulation test conditions so that proper heat flux levels to, and therefore surface temperatures of, the test samples are achieved.

Schaefer, J. W.↗
NASA NTRS1975

An analytical and experimental evaluation of airfoil sections for helicopter rotor application

The influence of the more independent airfoil parameters such as thickness, thickness distribution, leading-edge radius, camber, and camber distribution on lift-Mach number characteristics is investigated at lift coefficients up to near-maximum lift. The analysis is based on the drag divergence Mach number (Md) prediction techniques, where Md is the free-stream Mach number at which the rate of increase of drag coefficient with Mach number equals 0.1. The analytical results obtained indicate the compromises in Md which result from changes in thickness ratio, location of maximum thickness, leading edge radius, camber addition, and location of maximum camber for four- and five-digit airfoils and some six-series airfoils of potential interest for helicopters. An example of airfoil sections which combines several of the favorable geometric changes is evaluated analytically and experimentally. A comparison of results shows that the relative effect of the geometric changes on the lift coefficient-Md relation is realistic, and that the methods of analysis employed can be effectively used during preliminary vehicle design and airfoil selection.

Bingham, G. J.↗
NASA NTRS1975

Analytical study of mixing and reacting three-dimensional supersonic combustor flow fields

An analytical investigation is presented of mixing and reacting hydrogen jets injected from multiple orifices transverse and parallel to a supersonic airstream. The COMOC computer program, based upon a finite-element solution algorithm, was developed to solve the governing equations for three-dimensional, turbulent, reacting, boundary-region, and confined flow fields. The computational results provide a three-dimensional description of the velocity, temperature, and species-concentration fields downstream of hydrogen injection. Detailed comparisons between cold-flow data and results of the computational analysis have established validity of the turbulent-mixing model based on the elementary mixing-length hypothesis. A method is established to initiate computations for reacting flow fields based upon cold-flow correlations and the appropriate experimental parameters of Mach number, injector spacing, and pressure ratio. Key analytical observations on mixing and combustion efficiency for reacting flows are presented and discussed.

Baker, A. J.↗
NASA NTRS1975

Dynamic analysis of a flexible spacecraft with rotating components. Volume 1: Analytical developments

Analytical procedures and digital computer code are presented for the dynamic analysis of a flexible spacecraft with rotating components. Topics, considered include: (1) nonlinear response in the time domain, and (2) linear response in the frequency domain. The spacecraft is assumed to consist of an assembly of connected rigid or flexible subassemblies. The total system is not restricted to a topological connection arrangement and may be acting under the influence of passive or active control systems and external environments. The analytics and associated digital code provide the user with the capability to establish spacecraft system nonlinear total response for specified initial conditions, linear perturbation response about a calculated or specified nominal motion, general frequency response and graphical display, and spacecraft system stability analysis.

Bodley, C. S.↗
NASA NTRS1975

Asymptotic analytical methods in fluid mechanics related to drag prediction

Some recent theoretical work of a purely analytical nature is described which promises to provide engineering predictions for the important drag-related phenomena of flow in the stall regime. This analytical work deals with rigorous asymptotic studies of the complete Navier-Stokes equations that govern the viscous flow around any aerodynamic body under conditions where boundary layer separation takes place from the body surface.

Inger, G. R.↗
NASA NTRS1976

Assessment of analytical and experimental techniques utilized in conducting plume technology tests 575 and 593

Since exhaust plumes affect vehicle base environment (pressure and heat loads) and the orbiter vehicle aerodynamic control surface effectiveness, an intensive program involving detailed analytical and experimental investigations of the exhaust plume/vehicle interaction was undertaken as a pertinent part of the overall space shuttle development program. The program, called the Plume Technology program, has as its objective the determination of the criteria for simulating rocket engine (in particular, space shuttle propulsion system) plume-induced aerodynamic effects in a wind tunnel environment. The comprehensive experimental program was conducted using test facilities at NASA's Marshall Space Flight Center and Ames Research Center. A post-test examination of some of the experimental results obtained from NASA-MSFC's 14 x 14-inch trisonic wind tunnel is presented. A description is given of the test facility, simulant gas supply system, nozzle hardware, test procedure and test matrix. Analysis of exhaust plume flow fields and comparison of analytical and experimental exhaust plume data are presented.

Baker, L. R.↗
NASA NTRS1976

The VORCOM. Part 1: Analytical considerations

The analytical considerations which support the computation of (1) two components of the velocity vector from an X-array and (2) the transverse vorticity from the X-array and an adjacent parallel wire pair are presented. The electronic circuit which will execute these computations at a 50 khz rate is also described. The factors limiting the accuracy of the measurements are identified and quantitative estimates are given for a typical x-probe. An extensive analysis of the factors which effect the output and which are unknown (or unknowable) during the measurements is presented. Quantitative estimates of these effects are developed in the form of an uncertainty analysis. Numerical values, calculated using the analytical structure of the response equations, are tabulated; other estimates which require special experiments are described.

Foss, J. F.↗
NASA NTRS1976

Analytical display design for flight tasks conducted under instrument meteorological conditions

Paramount to proper utilization of electronic displays is a method for determining pilot-centered display requirements. Display design should be viewed fundamentally as a guidance and control problem which has interactions with the designer's knowledge of human psychomotor activity. From this standpoint, reliable analytical models of human pilots as information processors and controllers can provide valuable insight into the display design process. A relatively straightforward, nearly algorithmic procedure for deriving model-based, pilot-centered display requirements was developed and is presented. The optimal or control theoretic pilot model serves as the backbone of the design methodology, which is specifically directed toward the synthesis of head-down, electronic, cockpit display formats. Some novel applications of the optimal pilot model are discussed. An analytical design example is offered which defines a format for the electronic display to be used in a UH-1H helicopter in a landing approach task involving longitudinal and lateral degrees of freedom.

Hess, R. A.↗
NASA NTRS1975

Tunable lasers and their application in analytical chemistry

The impact that laser techniques might have in chemical analysis is examined. Absorption, scattering, and heterodyne detection is considered. Particular emphasis is placed on the advantages of using frequency-tunable sources, and dye solution lasers are regarded as the outstanding example of this type of laser. Types of spectroscopy that can be carried out with lasers are discussed along with the ultimate sensitivity or minimum detectable concentration of molecules that can be achieved with each method. Analytical applications include laser microprobe analysis, remote sensing and instrumental methods such as laser-Raman spectroscopy, atomic absorption/fluorescence spectrometry, fluorescence assay techniques, optoacoustic spectroscopy, and polarization measurements. The application of lasers to spectroscopic methods of analysis would seem to be a rewarding field both for research in analytical chemistry and for investments in instrument manufacturing.

Steinfeld, J. I.↗
NASA NTRS1977

Analytical screening of low emissions, high performance duct burners for supersonic cruise aircraft engines

An analytical screening study was conducted to identify duct burner concepts capable of providing low emissions and high performance in advanced supersonic engines. Duct burner configurations ranging from current augmenter technology to advanced concepts such as premix-prevaporized burners were defined. Aerothermal and mechanical design studies provided the basis for screening these configurations using the criteria of emissions, performance, engine compatibility, cost, weight and relative risk. Technology levels derived from recently defined experimental low emissions main burners are required to achieve both low emissions and high performance goals. A configuration based on the Vorbix (Vortex burning and mixing) combustor concept was analytically determined to meet the performance goals and is consistent with the fan duct envelope of a variable cycle engine. The duct burner configuration has a moderate risk level compatible with the schedule of anticipated experimental programs.

Lohmann, R. A.↗