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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Equations of motion of the lunar roving vehicle.

Equations of motion have been formulated for a four-wheel vehicle as it traverses a terrain characterized by slopes, craters, bumps, washboards, or a power spectrum. Independent suspension and electric motor propulsion are considered. These equations were programmed on the UNIVAC 1108 digital computer. Results are given for the steerability of the Lunar Roving Vehicle (LRV) which was found to be satisfactory for normal operating speeds and turning radii. The vehicle was also found to be satisfactory against overturning in both the pitch and roll mode, and results are presented for various speeds as the LRV engages a bump on meter in diameter and of varying heights. Speed, power consumption, and load characteristics are presented for the LRV traversing a simulated lunar soil at full throttle. Comparisons are given against data compiled from the Apollo 15 mission.

Kaufman, S.↗
NASA NTRS1978

New formulation of de Sitter's theory of motion for Jupiter I-IV. I - Equations of motion and the disturbing function

Elliptic orbits are substituted for circular orbits in the first approximation, in an analysis of the common retrograde motion of Jupiter's satellites. A modification of the de Sitter theory, made possible by extended observations of the satellites, is presented with attention to that aspect of the theory which eliminates small divisors at all stages of the solution. The convergence problem is circumvented by use of Poincare's canonical relative coordinates. In addition, modified Delaunay variables and their associated Poincare variables are applied to the disturbing function, which is expanded by means of generalized Newcomb operators.

Aksnes, K.↗
NASA NTRS2010

Enhanced Modeling of First-Order Plant Equations of Motion for Aeroelastic and Aeroservoelastic Applications

A methodology is described for generating first-order plant equations of motion for aeroelastic and aeroservoelastic applications. The description begins with the process of generating data files representing specialized mode-shapes, such as rigid-body and control surface modes, using both PATRAN and NASTRAN analysis. NASTRAN executes the 146 solution sequence using numerous Direct Matrix Abstraction Program (DMAP) calls to import the mode-shape files and to perform the aeroelastic response analysis. The aeroelastic response analysis calculates and extracts structural frequencies, generalized masses, frequency-dependent generalized aerodynamic force (GAF) coefficients, sensor deflections and load coefficients data as text-formatted data files. The data files are then re-sequenced and re-formatted using a custom written FORTRAN program. The text-formatted data files are stored and coefficients for s-plane equations are fitted to the frequency-dependent GAF coefficients using two Interactions of Structures, Aerodynamics and Controls (ISAC) programs. With tabular files from stored data created by ISAC, MATLAB generates the first-order aeroservoelastic plant equations of motion. These equations include control-surface actuator, turbulence, sensor and load modeling. Altitude varying root-locus plot and PSD plot results for a model of the F-18 aircraft are presented to demonstrate the capability.

Pototzky, Anthony S.↗
NASA NTRS1974

A vector-dyadic development of the equations of motion for N-coupled rigid bodies and point masses

The equations of motion are derived, in vector-dyadic format, for a topological tree of coupled rigid bodies, point masses, and symmetrical momentum wheels. These equations were programmed, and form the basis for the general-purpose digital computer program N-BOD. A complete derivation of the equations of motion is included along with a description of the methods used for kinematics, constraint elimination, and for the inclusion of nongyroscope forces and torques acting external or internal to the system.

Frisch, H. P.↗
NASA NTRS1984

Dynamics analysis of electrodynamic satellite tethers. Equations of motion and numerical solution algorithms for the tether

The equations of motion are developed for a perfectly flexible, inelastic tether with a satellite at its extremity. The tether is attached to a space vehicle in orbit. The tether is allowed to possess electrical conductivity. A numerical solution algorithm to provide the motion of the tether and satellite system is presented. The resulting differential equations can be solved by various existing standard numerical integration computer programs. The resulting differential equations allow the introduction of approximations that can lead to analytical, approximate general solutions. The differential equations allow more dynamical insight of the motion.

Nacozy, P. E.↗
NASA NTRS1993

Solving modal equations of motion with initial conditions using MSC/NASTRAN DMAP. Part 1: Implementing exact mode superposition

Within the MSC/NASTRAN DMAP (Direct Matrix Abstraction Program) module TRD1, solving physical (coupled) or modal (uncoupled) transient equations of motion is performed using the Newmark-Beta or mode superposition algorithms, respectively. For equations of motion with initial conditions, only the Newmark-Beta integration routine has been available in MSC/NASTRAN solution sequences for solving physical systems and in custom DMAP sequences or alters for solving modal systems. In some cases, one difficulty with using the Newmark-Beta method is that the process of selecting suitable integration time steps for obtaining acceptable results is lengthy. In addition, when very small step sizes are required, a large amount of time can be spent integrating the equations of motion. For certain aerospace applications, a significant time savings can be realized when the equations of motion are solved using an exact integration routine instead of the Newmark-Beta numerical algorithm. In order to solve modal equations of motion with initial conditions and take advantage of efficiencies gained when using uncoupled solution algorithms (like that within TRD1), an exact mode superposition method using MSC/NASTRAN DMAP has been developed and successfully implemented as an enhancement to an existing coupled loads methodology at the NASA Lewis Research Center.

Abdallah, Ayman A.↗
NASA NTRS1976

The longitudinal equations of motion of a tilt prop/rotor aircraft including the effects of wing and prop/rotor blade flexibility

The equations of motion for the longitudinal dynamics of a tilting prop/rotor aircraft are developed. The analysis represents an extension of the equations of motion. The effects of the longitudinal degrees of freedom of the body (pitch, heave and horizontal velocity) are included. The results of body freedom can be added to the equations of motion for the flexible wing propeller combination.

Curtiss, H. C., Jr.↗
NASA NTRS1979

A computer program to generate equations of motion matrices, L217 (EOM). Volume 1: Engineering and usage

The equations of motion program L217 formulates the matrix coefficients for a set of second order linear differential equations that describe the motion of an airplane relative to its level equilibrium flight condition. Aerodynamic data from FLEXSTAB or Doublet Lattice (L216) programs can be used to derive the equations for quasi-steady or full unsteady aerodynamics. The data manipulation and the matrix coefficient formulation are described.

Kroll, R. I.↗
DOE OSTI2024

A Geometric Derivation of the Governing Equations of Motion of Nonholonomic Dynamic Systems

Here, in this paper, we present a Riemannian geometric derivation of the governing equations of motion of nonholonomic dynamic systems. A geometric form of the work-energy principle is first derived. The geometric form can be realized in appropriate generalized quantities, and the independent equations of motion can be obtained if the subspace of generalized speeds allowable by nonholonomic constraints can be determined. We provide a geometric perspective of the governing equations of motion and demonstrate its effectiveness in studying dynamic systems subjected to nonholonomic constraints.

42 ENGINEERING↗
NASA NTRS1987

Equations of motion for maneuvering flexible spacecraft

This paper is concerned with the derivation of the equations of motion for maneuvering flexible spacecraft both in orbit and in an earth-based laboratory. The structure is assumed to undergo large rigid-body maneuvers and small elastic deformations. A perturbation approach is presented in which the quantities defining the rigid-body maneuver are regarded as the unperturbed motion and the elastic motions and deviations from the rigid-body motions are regarded as the perturbed motion. The perturbation equations are linear, non-self-adjoint, and with time-dependent coefficients. A maneuver force distribution exciting the least amount of elastic deformation of the spacecraft is developed. Numerical results highlight the vibration caused by rotational maneuvers.

Meirovitch, L.↗
NASA NTRS1972

Equations of motion for the variable mass flow-variable exhaust velocity rocket

An equation of motion for a one dimensional rocket is derived as a function of the mass flow rate into the acceleration chamber and the velocity distribution along the chamber, thereby including the transient flow changes in the chamber. The derivation of the mass density requires the introduction of the special time coordinate. The equation of motion is derived from both classical force and momentum approaches and is shown to be consistent with the standard equation expressed in terms of flow parameters at the exit to the acceleration chamber.

Tempelman, W. H.↗
NASA NTRS1971

Computerized series solution of relativistic equations of motion.

A method of solution of the equations of planetary motion is described. It consists of the use of numerical general perturbations in orbital elements and in rectangular coordinates. The solution is expanded in Fourier series in the mean anomaly with the aid of harmonic analysis and computerized series manipulation techniques. A detailed application to the relativistic motion of the planet Mercury is described both for Schwarzschild and isotropic coordinates.

Broucke, R.↗