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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 217 records · Page 12

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NASA NTRS1974

Mariner Venus/Mercury 1973 solar radiation force and torques

The need for an improvement of the mathematical model of the solar radiation force and torques for the Mariner Venus/Mercury spacecraft arises from the fact that this spacecraft will be steering toward the inner planets (Venus and Mercury), where, due to the proximity of the Sun, the effect of the solar radiation pressure is much larger than it was on the antecedent Mariner spacecraft, steering in the opposite direction. Therefore, although the model yielded excellent results in the case of the Mariner 9 Mars Orbiter, additional effects of negligible magnitudes for the previous missions of the Mariner spacecraft should now be included in the model. This study examines all such effects and incorporates them into the already existing model, as well as using the improved model for calculation of the solar radiation force and torques acting on the Mariner Venus/Mercury spacecraft.

Georgevic, R. M.↗

NASA NTRS1974

Exploiting environmental torques for attitude control and determination of spin stabilized satellites

Design techniques are presented which exploit environmental torques for attitude control and determination of spin stabilized satellites. The techniques are applicable to satellite missions where the dominant environmental torques are well understood and lend themselves to accurate analytical modeling. The techniques were applied to the Particles and Fields subsatellites of the Apollo 15 and 16 spacecraft and the flight results show good agreement with the attitude determination estimates obtained.

Gluck, R.↗

NASA NTRS1980

Torque control for electric motors

Method for adjusting electric-motor torque output to accomodate various loads utilizes phase-lock loop to control relay connected to starting circuit. As load is imposed, motor slows down, and phase lock is lost. Phase-lock signal triggers relay to power starting coil and generate additional torque. Once phase lock is recoverd, relay restores starting circuit to its normal operating mode.

Bernard, C. A.↗

NASA NTRS1980

Reduction of unsteady wind torques on an open port airborne optical turret

Techniques for reducing the unsteady torques acting on the inner gimbal of a turret were developed. The reductions in the unsteady torques were obtained by using fixes that alter undesirable flow characteristics or change the acoustic properties of the turret cavity. These fixes were designed to be used in the subsonic and transonic flow regimes. The flow field about the turret generally three dimensional and turbulent, and shock waves formed because of the rapid acceleration of the compressible gas about the blunt turret. The situation was further complicated by the presence of the cavity flow, and the fact that the mouth of the cavity must sweep through a wide angular variation relative to the direction of the freestream. Results indicate that significant reductions of the unsteady pressures measured in the turret cavity could be obtained by the use of porous wind screens around the aperature of the cavity mouth.

Thomas, J. P., Jr.↗

NASA NTRS1980

Atmospheric tides and the rotation of Venus. I - Tidal theory and the balance of torques

Insolation absorbed by the surface of Venus is quickly redeposited at the bottom of the atmosphere. This periodic heating causes mass to flow away from the warm afternoon side of the planet and into the cooler morning region. The Sun's gravitational field exerts a torque on this atmospheric tide tending to accelerate the retrograde zonal circulation. When this torque is transmitted to the crust, it can balance the despinning effect of tides in the body of Venus. The slow retrograde rotation of Venus may be a steady state among tides in the atmosphere, tides in the solid body, and possibly the influence of the Earth.

Dobrovolskis, A. R.↗

NASA NTRS1979

Accretion by rotating magnetic neutron stars. III - Accretion torques and period changes in pulsating X-ray sources

The solutions of the two-dimensional hydromagnetic equations are used to calculate the torque on a magnetic neutron star accreting from a Keplerian disk. It is found that the magnetic coupling between the star and the plasma in the outer transition zone is appreciable; that as a result, the spin-up torque on fast rotators is substantially less than that on slow rotators, and that for sufficiently high stellar angular velocities or sufficiently low mass accretion rates, the rotation of the star can be braked while accretion continues. These results are applied to pulsating X-ray sources, revealing that at high luminosities a star of given spin period rotating in the same direction as the disk can experience either spin-up or spin-down, depending on its luminosity. Also considered are the general problem of interpreting period changes in pulsating X-ray sources, and the dipole magnetic moments of nine pulsating X-ray sources are estimated by fitting the theoretical spin-up equation to estimates of the average luminosity and spin-up rate of each source.

Ghosh, P.↗

NASA NTRS1982

Cam-Design Torque Wrench

New Torque wrench for electrical connnectors automatically tightens its grip with increasing torque to insure against slippage. Tool requires only minimal clearance between connector and adjacent structures or components. Wrench is operated with one hand and can be used on connectors of various shapes.

Schick, P. H. J.↗

NASA NTRS1982

Torque Simulator for Rotating Systems

New torque brake simulates varying levels of friction in bearings of rotating body. Rolling-tail torque brake uses magnetic force to produce friction between rotating part and stationary part. Simulator electronics produce positive or negative feedback signal, depending on direction of rotation. New system allows for first time in-depth study of effects of tail-fin spin rates on pitch-, yaw-, and roll-control characteristics.

Davis, W. T.↗

NASA NTRS1982

A survey of nongravitational forces and space environmental torques with applications to the Galileo spacecraft

A detailed survey of nongravitational forces and space environmental torques acting upon the Galileo spacecraft during its interplanetary flight to Jupiter is given. It includes simple analytic equations to model the first order effect of: solar, planetary and spacecraft radiation, solar wind, meteoroids, cosmic rays, magnetic fields, atmospheric forces and gas leakage of the propulsion system. The model parameters are taken from recent spaceflight data. The result is a probabilistic error model of the magnitudes of the disturbing forces and torques. It provides a useful tool for the analysis of the Galileo and future spaceflight missions.

Longuski, J. M.↗

NASA NTRS1984

Torque-Wrench Extension Arm

Torque-wrench extension arm makes possible to apply torque to bolt, screw, or nut inaccessible to conventional wrenches or in areas where wrench cannot be manipulated. Used in narrow pockets and behind panels and walls.

Pacala, T. J.↗

NASA NTRS1984

Displaying Force and Torque of A Manipulator

Display combines bar charts, vector diagrams, and numerical values to inform operator of forces and torques exerted by end effector of manipulator. On voice or keyboard command, eight-channel strip-chart recorder traces force and torque components and claw position of raw measurements from eight strain gage sensors in end effector. Especially helpful when operator's view of end effector is obscured.

Bejczy, A. K.↗

NASA NTRS1984

Ring torque on Janus and the melting of Enceladus

The absence of craters noted on Voyager 2 images of Encedalus indicates geologically recent resurfacing, probably due to internal melting; heating mechanism calculations, however, yield heating rates too small to cause melting. If Janus, whose orbital mean motion is currently decreasing as Janus' orbit evolves outward due to resonant torques from Saturn's rings, were ever to become locked into a stable 2:1 orbital commensurability with Encedalus, the resulting angular momentum transfer could have sufficiently enhanced the eccentricity of Encedalus' orbit for the ensuing tidal heating to have melted Encedalus' interior. However, the predicted rapid time scale for ring evolution due to resonant torques from Saturn's inner moons remains a major problem.

Lissauer, J. J.↗

NASA NTRS1986

Torque-Summing Brushless Motor

Torque channels function cooperatively but electrically independent for reliability. Brushless, electronically-commutated dc motor sums electromagnetic torques on four channels and applies them to single shaft. Motor operates with any combination of channels and continues if one or more of channels fail electrically. Motor employs single stator and rotor and mechanically simple; however, each of channels electrically isolated from other so that failure of one does not adversely affect others.

Vaidya, J. G.↗

NASA NTRS1986

Hex ball torque test

A series of torque tests were performed on four flight-type hex ball universal joints in order to characterize and determine the actual load-carrying capability of this device. The universal joint is a part of manual actuation rods for scientific instruments within the Hubble Space Telescope. It was found that the hex ball will bind slightly during the initial load application. This binding did not affect the function of the universal joint, and the units would wear-in after a few additional loading cycles. The torsional yield load was approximately 50 ft-lb, and was consistent among the four test specimens. Also, the torque required to cause complete failure exceeded 80 ft-lb. It is concluded that the hex ball universal joint is suitable for its intended applications.

Robinson, B. A.↗

NASA NTRS1986

Gravity gradient torque for an arbitrary potential function

To permit investigation of the relative effects of higher-order terms in the potential function and allow computation of the gravity gradient torques consistent with the gravitational acceleration for a given potential function, a simple formula is derived for computing the gravity gradient torque on a vehicle in terms of the eigenvalues and eigenvectors of the gravity gradient matrix and the inertia properties of the vehicle. The formulation is applicable to any potential function for which the gravity matrix can be computed for a given point in the potential field.

Glandorf, D. R.↗

NASA NTRS1987

Six component robotic force-torque sensor

The results of a two-phase contract studying the feasibility of a miniaturized six component force-torque sensor and development of a working laboratory system were described. The principle of operation is based upon using ultrasonic pulse-echo ranging to determine the position of ultrasonic reflectors attached to a metal or ceramic cover plate. Because of the small size of the sensor, this technology may have application in robotics, to sense forces and torques at the finger tip of a robotic end effector. Descriptions are included of laboratory experiments evaluating materials and techniques for sensor fabrication and of the development of support electronics for data acquisition, computer interface, and operator display.

Grahn, Allen R.↗

NASA NTRS1986

Density waves in the solar nebula - Differential Lindblad torque

The differential torque exerted by Lindblad resonances on a perturbing object embedded in a two-dimensional nonself-gravitating disk with density, pressure and sound speed gradients is quantified. First-order corrections are made to account for Keplerian rotation and the presence of the gradients. The total torque is calculated by summing over all resonances in the absence of local wave damping. When applied to the primordial solar nebula disk, the calculations show that disks that cool with increasing heliocentric distance will cause decay of the orbit of the perturbing object. Conditions in which the perturber will escape orbit delay are also described. The characteristic drift time will be no greater than the stochastic accretion time scales. Implications of the calculations for planetary formation are discussed.

Ward, W. R.↗

NASA NTRS1989

Magnetic Coupling Delivers Increased Torque

Fixed magnetic pins reduce reluctance of gap in magnetic coupling. Concentrate flux and increase torque transmitted. Coupling arranged as face or radial drive. Addition of flux pins to gap between magnetically coupled shafts in bioreactor experiment increases transferred torque by almost 50 percent.

Carter, Edward L.↗