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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1967

Finite element modeling of a cantilever beam

Finite element modeling of uniform cantilever beams and computation of transverse frequencies due to combinations of bending with rotatory inertia and shear flexibility

CANTILEVER BEAM↗
NASA NTRS1943

Requirements for Auxiliary Stiffeners Attached to Panels Under Combined Compression and Shear

Panels of aluminum alloy sheets, framed by side and end stiffeners, were subjected to combined loading by means of offset knife edges applying loads to top and bottom end plates with reacting forces against the end plates supplied by laterally acting rollers. The test specimens were 17S-T aluminum alloy shoots 0.040 inch thick in panels of 10-inch width and three different lengths (approximately 10, 26, and 30 inch). Data were obtained for the bowing of transverse and longitudinal ribs of rectangular cross section and varying depths mounted on one side of the sheet only, for several ratios of compression to shear loads. Limiting values of the moments of inertia were calculated from these measurements. The experimental values exceed the theoretical values given by Timoshenko for the case of simply supported sheets with uniformly distributed boundary stresses. The work reported includes measurements of the effective shear moduli of the nine test panels with and without ribs. These data are compared with values published by Lahdo and Wagner.

ALUMINUM ALLOYS, SHEET - ALCOA 17ST - STRENGTH↗
NASA NTRS2015

Testing and Validation of the Dynamic Interia Measurement Method

This presentation describes the DIM method and how it measures the inertia properties of an object by analyzing the frequency response functions measured during a ground vibration test (GVT). The DIM method has been in development at the University of Cincinnati and has shown success on a variety of small scale test articles. The NASA AFRC version was modified for larger applications.

vibration tests↗
NASA NTRS1963

A Passive Gravitational Attitude Control System for Satellites

It is shown how the gravity-gradient effect may be utilized to design a long-lived, earth-pointing satellite attitude control system which requires no fuel supplies, attitude sensors or active control equipment. This two-body system is provided with a magnetic hysteresis damper which effectively damps out oscillations (librations) about the local vertical. The long rods, which must be extended in space from coiled up metal tapes, provide the required large moments of inertia and possess adequate rigidity and sufficient strength to endure the rigors of the extension process. The system is compatible with the requirements of multiple satellite launchings from a single last-stage vehicle. Analysis indicates that the gravitational torques are sufficient to keep the disturbing effects of solar radiation pressure, residual magnetic dipole moments, orbit eccentricity, rod curvature, eddy currents, and meteorite impacts within tolerable limits. It is believed that the high-performance, earth-pointing system described and analyzed in this paper represents an essential step in the development of high-capacity communications satellites requiring long life.

GRAVITY↗
NASA NTRS1959

Some effects of vibration and rotation on the drift of gyroscopic instruments

It is the purpose of this paper to describe and indicate possible analytical approaches to some of the most significant mechanisms by which vibration induced drifts may occur, and to indicate, where possible, some means of alleviating them. In all cases we will not consider gimbal bearing friction, mass unbalance or other sources of steady extraneous torques on the gyro rotor. The mechanisms to be discussed are: Non-Newtonian viscosity in single degree of freedom (SDF) integrating-rate gyros, nonisoelasticity in SDF gyros, noncommutative effects for SDF stabilized platform, gimbal inertia effects, 2 DF gyros, and spin axis torque coupling in 2 DF gyros. High-frequency elastic resonances are not discussed explicitly in detail, because they are a more familiar problem and one which depends strongly on the details of each particular gyro design.

Viscous Torque↗
NASA NTRS1958

Vehicle Motions as Inferred from Radio-signal- Strength Records

Considerable data on various parameters of a satellite and its launching vehicle can be obtained from the received-signal-strength records at the various satellite receiver stations. The doppler shifts of the satellite can be used to determine the orbital characteristics quite accurately. (Ref. 1 discusses the rapid determination of these parameters.) Information concerning the velocity increment and direction of each stage can be obtained if doppler data are received by several stations during the high-speed staging. The variations in signal strength during launch can be used to find the spin rate of the satellite before, during, and after staging, and to find variations in attitude, including precession, during launch. With spin and precession frequencies available, any changes in the ratios of moments of inertia can be determined. In this paper the launchings of the Explorer satellites will be used as a basis for the generalized conclusions concerning utilization of radio-signal-strength records. The discussion includes a description of the Explorer launching system.

Pilkington, W. C.↗