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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Metal-silicate friction in ultrahigh vacuum

Results of the analysis and experiments on the frictional behavior of materials under conditions of ultrahigh vacuum, as related to kinematic problems in a lunar environment, are presented. Experiments have been performed under varying conditions of cleanliness to determine frictional characteristics at 10 to the minus 7th power to 10 to the minus 8th power torr between flat basalt and spherical 7075-T6 aluminum surfaces. A quantitative analysis has been made of the factors influencing frictional behavior of these materials. The proposed mathematical model incorporated parameters of surface cleanliness, surface roughness, and surface energy.

Ofodile, E. I.↗
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 NTRS1975

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

The equations of motion for a system of coupled flexible bodies, rigid bodies, point masses, and symmetric wheels were derived. The equations were cast into a partitioned matrix form in which certain partitions became nontrivial when the effects of flexibility were treated. The equations are shown to contract to the coupled rigid body equations or expand to the coupled flexible body equations all within the same basic framework. Furthermore, the coefficient matrix always has the computationally desirable property of symmetry. Making use of the derived equations, a comparison was made between the equations which described a flexible body model and those which described a rigid body model of the same elastic appendage attached to an arbitrary coupled body system. From the comparison, equivalence relations were developed which defined how the two modeling approaches described identical dynamic effects.

Frisch, H. P.↗
NASA NTRS1977

High-resolution observations of the Lyman alpha sky background

The first high-resolution observations of the Lyman alpha sky background, obtained with a spectrometer on the Copernicus satellite, are examined. The high-resolution observations presented allow the first direct measurement of the heliocentric velocity of the local interstellar medium. The high resolution of the spectrometer and the projection of the earth's orbital velocity along the line of sight made it possible to separate the weak extraterrestrial background feature from the intense geocoronal emission line. The observations also contain considerable information about the Lyman alpha emission from the geocorona. The data permit limits to be placed on the temperature of the gas that produces the background feature.

Adams, T. F.↗
NASA NTRS1978

The N-BOD2 user's and programmer's manual

A general purpose digital computer program was developed and designed to aid in the analysis of spacecraft attitude dynamics. The program provides the analyst with the capability of automatically deriving and numerically solving the equations of motion of any system that can be modeled as a topological tree of coupled rigid bodies, flexible bodies, point masses, and symmetrical momentum wheels. Two modes of output are available. The composite system equations of motion may be outputted on a line printer in a symbolic form that may be easily translated into common vector-dyadic notation, or the composite system equations of motion may be solved numerically and any desirable set of system state variables outputted as a function of time.

Frisch, H. P.↗