125
125

May 23, 2011
05/11

by
Chu, Barbara C. F.; Orgel, Leslie E

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Conjugates of biotin with the decamer of glutamic acid (glu(sub 10)) and the trimer of D,L-2-amino-5-phosphonovaleric acid (I) have been synthesized, and it has been shown that they mediate the binding of avidin to hydroxylapatite. In a similar way a conjugate of methotrexate with glu(sub 10) mediates the binding of dihydrofolate reductase to the mineral. The presentation of ligands on the hydroxylapatite component of bone may find applications in clinical medicine.

Topics: GRID GENERATION (MATHEMATICS), PREDICTOR-CORRECTOR METHODS, WINGS, COMPUTATIONAL GRIDS, LAPLACE...

502
502

May 29, 2011
05/11

by
NON

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This volume contains abstracts that have been accepted for presentation at the First Landing Site Workshop for the 2003 Mars Exploration Rovers, January 24-25, 2001.

Topics: COMPUTATIONAL FLUID DYNAMICS, PREDICTOR-CORRECTOR METHODS, FLOW DISTRIBUTION, ROTOR AERODYNAMICS,...

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154

Jul 12, 2010
07/10

by
Dorsch, R. G.; Boyd, B

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No Abstract Available

Topics: ALGORITHMS, BUCKLING, EQUATIONS OF MOTION, KINETIC EQUATIONS, NONLINEAR EQUATIONS,...

374
374

Jun 9, 2011
06/11

by
Levine, Joel S

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Biomass burning is a source of greenhouse gases, carbon dioxide, methane, and nitrous oxide. In addition, biomass burning is a source of chemically active gases, including carbon monoxide, nonmethane hydrocarbons, and nitric oxide. These gases, along with methane, lead to the chemical production of tropospheric ozone (another greenhouse gas) as well as control the concentration of the hydroxyl radical, which regulates the lifetime of almost every atmospheric gas. Following biomass burning,...

Topics: EQUATIONS OF STATE, SENSITIVITY ANALYSIS, HEAT TRANSFER, FINITE ELEMENT METHOD, TIME MARCHING,...

216
216

Jul 11, 2010
07/10

by
Hough, W. W

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Relationship between spacecraft structural loads and ground wind constraints at launch time

Topics: AXISYMMETRIC BODIES, NUMERICAL ANALYSIS, NUMERICAL CONTROL, PREDICTOR-CORRECTOR METHODS, TABLES...

265
265

May 23, 2011
05/11

by
Bement, Laurence J

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Following several flight and ground test failures of spacecraft systems using single-shot, 'normally closed' pyrotechnically actuated valves (pyrovalves), a Government/Industry cooperative program was initiated to assess the functional performance of five qualified designs. The goal of the program was to provide information on functional performance of pyrovalves to allow users the opportunity to improve procurement requirements. Specific objectives included the demonstration of performance...

Topics: FINITE ELEMENT METHOD, COMPUTATIONAL GRIDS, NONLINEARITY, TIME MARCHING, ALGORITHMS, BOUNDARY VALUE...

The procedure to generate the grid around a complex wing configuration is presented in this report. The automatic grid generation utilizes the Modified Advancing Front Method as a predictor and an elliptic scheme as a corrector. The scheme will advance the surface grid one cell outward and the newly obtained grid is corrected using the Laplace equation. The predictor-corrector step ensures that the grid produced will be smooth for every configuration. The predictor-corrector scheme is extended...

Topics: NASA Technical Reports Server (NTRS), GRID GENERATION (MATHEMATICS), PREDICTOR-CORRECTOR METHODS,...

184
184

May 31, 2011
05/11

by
deGroh, H. C.; Li, K.; Li, B. Q

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A 2-D finite element model is presented for the melt growth of single crystals in a microgravity environment with a superimposed DC magnetic field. The model is developed based on the deforming finite element methodology and is capable of predicting the phenomena of the steady and transient convective flows, heat transfer, solute distribution, and solid-liquid interface morphology associated with the melt growth of single crystals in microgravity with and without an applied magnetic field....

Topics: COLLOCATION, FUNCTIONS (MATHEMATICS), RUNGE-KUTTA METHOD, PARTIAL DIFFERENTIAL EQUATIONS,...

A rotor section aerodynamics design package is developed by coupling Constrained Direct Iterative Surface Curvature (CDISC) design method with the FPX rotor code. The coupling between the CDISC design and the FPX flow analysis is fully automated. The CDISC design method employs a predictor-corrector procedure iteratively to determine a surface geometry which produces a target pressure distribution, where the target pressure distributions is either pre-defined or automatically generated through...

Topics: NASA Technical Reports Server (NTRS), COMPUTATIONAL FLUID DYNAMICS, PREDICTOR-CORRECTOR METHODS,...

We discuss an Adams-type predictor-corrector method for the numerical solution of fractional differential equations. The method may be used both for linear and for nonlinear problems, and it may be extended to multi-term equations (involving more than one differential operator) too.

Topics: NASA Technical Reports Server (NTRS), DIFFERENTIAL EQUATIONS, PREDICTOR-CORRECTOR METHODS,...

A method for automatic multiblock grid generation is described. The method combines the modified advancing front method as a predictor with an elliptic scheme as a corrector. It advances a collection of cells by one cell height in the outward direction using modified advancing front method, and then corrects newly-obtained cell positions by solving elliptic equations. This predictor-corrector type scheme is repeatedly applied until the field of interest is filled with hexahedral grid cells....

Topics: NASA Technical Reports Server (NTRS), COMPUTATIONAL FLUID DYNAMICS, GRID GENERATION (MATHEMATICS),...

A new algorithm for identifying and characterizing vortices in complex flows is presented. The scheme uses both the vorticity and pressure fields. A skeleton line along the center of a vortex is produced by a two-step predictor-corrector scheme. The technique uses the vector field to move in the direction of the skeleton line and the scalar field to correct the location in the plane perpendicular to the skeleton line. A general vortex cross section can be concisely defined with five parameters...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, COMPUTATIONAL FLUID DYNAMICS, PREDICTOR-CORRECTOR...

The principles of conservation and stability of difference schemes achieved using the iteration control method were examined. For the schemes obtained of the predictor-corrector type, the conversion was proved for the control sequences of approximate solutions to the precise solutions in the Sobolev metrics. Algorithms were developed for reducing the differential problem to integral relationships, whose solution methods are known, were designed. The algorithms for the problem solution are...

Topics: NASA Technical Reports Server (NTRS), DIFFUSION THEORY, NONLINEAR EQUATIONS, NUMERICAL ANALYSIS,...

A multiphase selfadaptive predictor corrector type algorithm was developed. This algorithm enables the solution of highly nonlinear structural responses including kinematic, kinetic and material effects as well as pro/post buckling behavior. The strategy involves three main phases: (1) the use of a warpable hyperelliptic constraint surface which serves to upperbound dependent iterate excursions during successive incremental Newton Ramphson (INR) type iterations; (20 uses an energy constraint to...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, BUCKLING, EQUATIONS OF MOTION, KINETIC EQUATIONS,...

162
162

May 22, 2011
05/11

by
Thompson, Nancy; Farmer, Mose

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A full-span F/A-18 E/F cable mounted wind tunnel model is part of a flutter clearance program at the NASA Langley Transonic Dynamics Tunnel. Parametric analysis of this model using GRUMCBL software was conducted to assess stability for wind tunnel tests. Two configurations of the F/A-18 E/F were examined. The parameters examined were pulley-cable friction, mach number, dynamic pressure, cable geometry, center of gravity location, cable tension, snubbing the model, drag, and test medium. For the...

Topics: ALGORITHMS, FLOW DISTRIBUTION, PRESSURE GRADIENTS, TURBULENCE, COMPUTATIONAL FLUID DYNAMICS, HILSCH...

135
135

Jun 13, 2011
06/11

by
Reig, P.; Papadakis, I. E.; Shrader, C. R.; Kazanas, D

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We have obtained Fourier-resolved spectra of the black-hole binary 4U 1543-47 in the canonical states (high/soft, very high, intermediate and low/hard) observed in this source during the decay of an outburst that took place in 2002. Our objective is to investigate the variability of the spectral components generally used to describe the energy spectra of black-hole systems, namely a disk component, a power-law component attributed to Comptonization by a hot corona and the contribution of the...

Topics: FLIGHT CHARACTERISTICS, NEPTUNE ATMOSPHERE, LOW ALTITUDE, TARGETS, PERFORMANCE TESTS,...

An explicit time/space finite difference procedure is used to model the propagation of sound in a quasi one-dimensional duct containing high Mach number subsonic flow. Nonlinear acoustic equations are derived by perturbing the time-dependent Euler equations about a steady, compressible mean flow. The governing difference relations are based on a fourth-order, two-step (predictor-corrector) MacCormack scheme. The solution algorithm functions by switching on a time harmonic source and allowing...

Topics: NASA Technical Reports Server (NTRS), FINITE DIFFERENCE THEORY, SOUND PROPAGATION, TRANSONIC FLOW,...

The determination of altitude by means of barometric sensors in sounding rocket applications is discussed. A method for predicting the performance of such sensing systems is needed. A method is developed for predicting the pressure-time response of a volume subjected to subsonic air flow through from one to four passages. The pressure calculation is based on one-dimensional gas flow with friction. A computed program has been developed which solves the differential equations using a...

Topics: NASA Technical Reports Server (NTRS), ALTIMETERS, EQUIPMENT SPECIFICATIONS, PRESSURE SENSORS,...

PredGuid+A software was developed to enable a unique numerical predictor-corrector aerocapture guidance capability that builds on heritage Orion entry guidance algorithms. The software can be used for both planetary entry and aerocapture applications. Furthermore, PredGuid+A implements a new Delta-V minimization guidance option that can take the place of traditional targeting guidance and can result in substantial propellant savings. PredGuid+A allows the user to set a mode flag and input a...

Topics: NASA Technical Reports Server (NTRS), AEROCAPTURE, PREDICTOR-CORRECTOR METHODS, COMPUTER PROGRAMS,...

This report describes the current state of development of methods for calculating optimal orbital transfers with large numbers of burns. Reported on first is the homotopy-motivated and so-called direction correction method. So far this method has been partially tested with one solver; the final step has yet to be implemented. Second is the patched transfer method. This method is rooted in some simplifying approximations made on the original optimal control problem. The transfer is broken up...

Topics: NASA Technical Reports Server (NTRS), ELECTRIC PROPULSION, OPTIMAL CONTROL, ORBITAL MANEUVERS,...

530
530

Jul 11, 2010
07/10

by
NON

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For abstract, see N73-30995.

Topics: FINITE DIFFERENCE THEORY, TWO DIMENSIONAL FLOW, FLOW DISTRIBUTION, BODIES OF REVOLUTION, FLOW...

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667

Jul 26, 2010
07/10

by
Lee, Jeh Wo

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The objective is the theoretical analysis and the experimental verification of dynamics and control of a two link flexible manipulator with a flexible parallel link mechanism. Nonlinear equations of motion of the lightweight manipulator are derived by the Lagrangian method in symbolic form to better understand the structure of the dynamic model. The resulting equation of motion have a structure which is useful to reduce the number of terms calculated, to check correctness, or to extend the...

Topics: AERODYNAMIC CHARACTERISTICS, AZIMUTH, CONTROL THEORY, CONTROLLERS, DOWNRANGE, PREDICTOR-CORRECTOR...

An adaptive numeric predictor-corrector guidance is developed for atmospheric entry vehicles which utilize lift to achieve maximum footprint capability. Applicability of the guidance design to vehicles with a wide range of performance capabilities is desired so as to reduce the need for algorithm redesign with each new vehicle. Adaptability is desired to minimize mission-specific analysis and planning. The guidance algorithm motivation and design are presented. Performance is assessed for...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, EQUATIONS OF MOTION, MISSION PLANNING, NUMERICAL...

The purpose of the Mars Entry, Descent and Landing Systems Analysis (EDL-SA) study was to identify feasible technologies that will enable human exploration of Mars, specifically to deliver large payloads to the Martian surface. This paper focuses on the methods used to guide and control two of the contending technologies, a mid- lift-to-drag (L/D) rigid aeroshell and a hypersonic inflatable aerodynamic decelerator (HIAD), through the entry portion of the trajectory. The Program to Optimize...

Topics: NASA Technical Reports Server (NTRS), MARS LANDING, AERODYNAMIC DRAG, DESCENT, SYSTEMS ANALYSIS,...

LSODE, the Livermore Solver for Ordinary Differential Equations, is a package of FORTRAN subroutines designed for the numerical solution of the initial value problem for a system of ordinary differential equations. It is particularly well suited for 'stiff' differential systems, for which the backward differentiation formula method of orders 1 to 5 is provided. The code includes the Adams-Moulton method of orders 1 to 12, so it can be used for nonstiff problems as well. In addition, the user...

Topics: NASA Technical Reports Server (NTRS), BACKWARD DIFFERENCING, BOUNDARY VALUE PROBLEMS, DIFFERENTIAL...

An application of a simple numerical technique which allows for the rapid construction of orthogonal coordinate systems about axisymmetric blunt bodies is presented. This technique can generate orthogonal meshes which have unequally spaced points in two directions. Relations are given for the numerical generation of the metric coefficients. Body shapes ranging from simple analytical bodies to complex reverse curvature bodies are presented together with their orthogonal coordinate systems. The...

Topics: NASA Technical Reports Server (NTRS), AXISYMMETRIC BODIES, BLUNT BODIES, COORDINATE...

The Dynamic Engine Analysis program, DEAN, is a FORTRAN code implemented on the IBM/370 mainframe at NASA Lewis Research Center for digital simulation of turbofan engine dynamics. DEAN is an interactive program which allows the user to simulate engine subsystems as well as a full engine systems with relative ease. The nonlinear first order ordinary differential equations which define the engine model may be solved by one of four integration schemes, a second order Runge-Kutta, a fourth order...

Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMS, COMPUTERIZED SIMULATION, ENGINE ANALYZERS,...

An online entry guidance algorithm has been developed using a predictor-corrector approach. The algorithm is designed for the Reusable Launch Vehicle (RLV) and is demonstrated by using, the X-33 model. The objective of the design is to handle widely dispersed entry conditions and deliver the vehicle at the Terminal Area Energy Management (TAEM) interface box within an acceptable tolerance and without violating any of the vehicle physical constraints. Combination of several control variables is...

Topics: NASA Technical Reports Server (NTRS), X-33 REUSABLE LAUNCH VEHICLE, PREDICTOR-CORRECTOR METHODS,...

A modified form of the Lepping - Argentiero single spacecraft, shock normal determination procedure is presented. The modified method incorporates a simple predictor-corrector algorithm which allows a faster convergence rate and the use of average values of the parameters for the starting vector.

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, APPROXIMATION, COMPUTER PROGRAMS, CONVERGENCE,...

An application of a simple numerical technique which allows for the rapid construction of orthogonal coordinate systems about two dimensional and axisymmetric bodies is presented. The technique is based on a predictor corrector numerical method. It can be used to generate orthogonal meshes which have unequally spaced points in two directions. These orthogonal meshes in their transformed computational plane are, however, equally spaced so that the differencing for the metric coefficients and the...

Topics: NASA Technical Reports Server (NTRS), COORDINATES, FLUID DYNAMICS, GRID GENERATION (MATHEMATICS),...

Future missions to Mars may require pin-point landing precision, possibly on the order of tens of meters. The ability to reach a target while meeting a dynamic pressure constraint to ensure safe parachute deployment is complicated at Mars by low atmospheric density, high atmospheric uncertainty, and the desire to employ only bank angle control. The vehicle aerodynamic performance requirements and guidance necessary for 0.5 to 1.5 lift drag ratio vehicle to maximize the achievable footprint...

Topics: NASA Technical Reports Server (NTRS), AERODYNAMIC CHARACTERISTICS, ATMOSPHERIC ENTRY, DYNAMIC...

A high-speed shear layer is studied using compressibility corrected Reynolds stress turbulence model which employs newly developed model for pressure-strain correlation. MacCormack explicit prediction-corrector method is used for solving the governing equations and the turbulence transport equations. The stiffness arising due to source terms in the turbulence equations is handled by a semi-implicit numerical technique. Results obtained using the new model show a sharper reduction in growth rate...

Topics: NASA Technical Reports Server (NTRS), COMPUTATIONAL FLUID DYNAMICS, REYNOLDS STRESS, SHEAR FLOW,...

In this paper, efficient dynamic simulation algorithms for a system of m manipulators, cooperating to manipulate a large load, are developed; their performance, using two possible forms of parallelism on a general-purpose parallel computer, is investigated. One form, temporal parallelism, is obtained with the use of parallel numerical integration methods. A speedup of 3.78 on four processors of CRAY Y-MP8 was achieved with a parallel four-point block predictor-corrector method for the...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, BODY KINEMATICS, COMPUTERIZED SIMULATION, DYNAMIC...

A new algorithm was developed for fast, automatic integration of chemical kinetic rate equations describing homogeneous, gas-phase combustion at constant pressure. Particular attention is paid to the distinguishing physical and computational characteristics of the induction, heat-release and equilibration regimes. The two-part predictor-corrector algorithm, based on an exponentially-fitted trapezoidal rule, includes filtering of ill-posed initial conditions, automatic selection of Newton-Jacobi...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, COMBUSTION, COMPUTER PROGRAMS, REACTION KINETICS,...

We present a method for visualizing unsteady flow by displaying its vortices. The vortices are identified by using a vorticity-predictor pressure-corrector scheme that follows vortex cores. The cross-sections of a vortex at each point along the core can be represented by a Fourier series. A vortex can be faithfully reconstructed from the series as a simple quadrilateral mesh, or its reconstruction can be enhanced to indicate helical motion. The mesh can reduce the representation of the flow...

Topics: NASA Technical Reports Server (NTRS), COMPUTER GRAPHICS, HILSCH TUBES, NUMERICAL FLOW...

A computational procedure is described which numerically integrates the equations of motion of an unguided rocket. Three translational and two angular (roll discarded) degrees of freedom are integrated through the final burnout; and then, through impact, only three translational motions are considered. Input to the routine is: initial time, altitude and velocity, vehicle characteristics, and other defined options. Input format has a wide range of flexibility for special calculations. Output is...

Topics: NASA Technical Reports Server (NTRS), COMPUTER PROGRAMS, SOUNDING ROCKETS, TRAJECTORY ANALYSIS,...

A new method for automatic multi-block grid generation is described. The method combines the Modified Advancing Front Method as a Predictor with an elliptic scheme as a corrector. It advances a collection of cells by one cell height in the outward direction using Modified Advancing Front Method, and then corrects newly-obtained cell positions by solving elliptic equations. This predictor-corrector type scheme is repeatedly applied until the field of interest is filled with hexahedral grid...

Topics: NASA Technical Reports Server (NTRS), ELLIPTIC DIFFERENTIAL EQUATIONS, GRID GENERATION...

The focus of the paper is on the derivation of sensitivity equations for transient heat transfer problems modeled by different discretization processes. Two examples will be used in this study to facilitate the discussion. The first example is a coupled, transient heat transfer problem that simulates the press molding process in fabrication of composite laminates. These state equations are discretized into standard h-version finite elements and solved by a multiple step, predictor-corrector...

Topics: NASA Technical Reports Server (NTRS), EQUATIONS OF STATE, SENSITIVITY ANALYSIS, HEAT TRANSFER,...

A method for numerically solving the three dimensional unsteady Euler equations using flux vector splitting is developed. The equations are cast in curvilinear coordinates and a finite volume discretization is used. An explicit upwind second-order predictor-corrector scheme is used to solve the discretized equations. The scheme is stable for a CFL number of two and local time stepping is used to accelerate convergence for steady-state problems. Characteristic variable boundary conditions are...

Topics: NASA Technical Reports Server (NTRS), DIFFERENTIAL EQUATIONS, EULER EQUATIONS OF MOTION, FLOW...

The focus of this research has been to determine the effectiveness of applying parallel processing techniques to a sizable real-world problem, the simulation of the dynamics associated with a tether which connects two objects in low earth orbit, and to explore the degree to which the parallelization process can be automated through the creation of new software tools. The goal has been to utilize this specific application problem as a base to develop more generally applicable techniques.

Topics: NASA Technical Reports Server (NTRS), PARALLEL PROCESSING (COMPUTERS), TETHERING, SOFTWARE...

The application of Predictor corrector integration algorithms developed for the digital parallel processing environment are investigated. The algorithms are implemented and evaluated through the use of a software simulator which provides an approximate representation of the parallel processing hardware. Test cases which focus on the use of the algorithms are presented and a specific application using a linear model of a turbofan engine is considered. Results are presented showing the effects of...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, DIGITAL SIMULATION, JET ENGINES, NUMERICAL...

Predictor-corrector schemes are discussed for the numerical integration of initial value problems by computer. Descloux formulas, which are considered modified Nordsieck formulas are studied because of their desirable stability and truncation properties along with the standard Nordsieck formulas. The stability of Nordsieck and modified Nordsieck algorithms are computed, and the results are graphed. Test problems are included as examples for comparing the efficiency of the algorithms.

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, BOUNDARY VALUE PROBLEMS, COMPUTER PROGRAMMING,...

A 3-dimensional particle trajectory computer code was developed to compute the distribution of water droplet impingement efficiency on a 3-dimensional engine inlet. The computed results provide the essential droplet impingement data required for the engine inlet anti-icing system design and analysis. The droplet trajectories are obtained by solving the trajectory equation using the fourth order Runge-Kutta and Adams predictor-corrector schemes. A compressible 3-D full potential flow code is...

Topics: NASA Technical Reports Server (NTRS), ENGINE INLETS, FLOW DISTRIBUTION, ICE FORMATION, INLET FLOW,...

In many cases the structure of a fluid flow is well-characterized by its vortices, especially for the purpose of visualization. In this paper we present a new algorithm for identifying vortices in complex flows. The algorithm produces a skeleton line along the center of a vortex by using a two-step predictor-corrector scheme. The vorticity vector field serves as the predictor and the pressure gradient (in the perpendicular plane) serves as the corrector. We describe an economical description of...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, COMPUTATIONAL FLUID DYNAMICS, HILSCH TUBES,...

Forward Euler's explicit, finite-difference formula of extrapolation, is used as a predictor and a convex formula as a corrector to integrate differential equations numerically. An application has been made to Burger's equation.

Topics: NASA Technical Reports Server (NTRS), BURGER EQUATION, DIFFERENTIAL EQUATIONS, EXTRAPOLATION,...

In this paper we present a new form of the collocation method that allows one to find very accurate solutions to time marching problems without the unwelcome appearance of Gibb's phenomenon oscillations. The basic method is applicable to any partial differential equation whose solution is a continuous, albeit possibly rapidly varying function. Discontinuous functions are dealt with by replacing the function in a small neighborhood of the discontinuity with a spline that smoothly connects the...

Topics: NASA Technical Reports Server (NTRS), COLLOCATION, PARTIAL DIFFERENTIAL EQUATIONS, DISCONTINUITY,...

We are developing a model to determine what fraction of the planetesimals would have hit a protoplanet on their sunward journey as opposed to having a close approach and passing into an inferior orbit. The model involves direct numerical integration of restricted-three-body orbits using a predictor-corrector integrator. A simple gas drag law with a v(exp 2) dependence was also included in the equations of motion. Runs of 100 to 500 particles were already performed, while some future runs may...

Topics: NASA Technical Reports Server (NTRS), ASTRONOMICAL MODELS, COLLISIONS, INTERSTELLAR GAS, ORBIT...

Hypersonic flow over spherical dome protuberances was investigated to determine increased pressure and heating loads to the surface. The configuration was mathematically modeled in a time-dependent three-dimensional analysis of the conservation of mass, momentum (Navier-Stokes), and energy equations. A boundary mapping technique was used to obtain a rectangular parallelepiped computational domain, a MacCormack explicit time-split predictor-corrector finite difference algorithm was used to...

Topics: NASA Technical Reports Server (NTRS), AEROTHERMODYNAMICS, DOMES (STRUCTURAL FORMS), HYPERSONIC...

This paper describes the development and evaluation of a numerical roll reversal predictor-corrector guidance algorithm for the atmospheric flight portion of the Mars Surveyor Program 2001 Orbiter and Lander missions. The Lander mission utilizes direct entry and has a demanding requirement to deploy its parachute within 10 km of the target deployment point. The Orbiter mission utilizes aerocapture to achieve a precise captured orbit with a single atmospheric pass. Detailed descriptions of these...

Topics: NASA Technical Reports Server (NTRS), AEROCAPTURE, AIRCRAFT GUIDANCE, AIRCRAFT LANDING, ALGORITHMS,...

An elastic large displacement thick-shell mixed finite element is modified to allow for the calculation of viscoelastic stresses. Internal strain variables are introduced at the element's stress nodes and are employed to construct a viscous material model. First order ordinary differential equations relate the internal strain variables to the corresponding elastic strains at the stress nodes. The viscous stresses are computed from the internal strain variables using viscous moduli which are a...

Topics: NASA Technical Reports Server (NTRS), FINITE ELEMENT METHOD, AIRCRAFT TIRES, VISCOELASTICITY,...