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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Relationship Between Rainfall in the Northern Hemisphere and Impulses of the Torque in the Sun's Motion

The analysis of major change in the angular momentum of the sun's irregular motion about the barycenter of the solar system, represented by extrema in the running variance of impulses of the torque (IOT), discloses a connection with both extrema in the Gleissberg cycle of secular sunspot activity and maxima in the thickness of varves from Lake Saki, Crimea. This significant relationship can be traced back to the 7th century. Further inquiries link the running variance in IOT to rainfall over central Europe, England, Wales, eastern United States, and India, as well as to temperature in Europe. This significant correlation covers more than 130 years.

Landscheidt, T.↗
NASA NTRS1991

Resolved rate and torque control schemes for large scale space based kinematically redundant manipulators

Resolved rate control of kinematically redundant ground based manipulators is a challenging problem. The structural, actuator, and control loop frequency characteristics of industrial grade robots generally allow operation with resolved rate control; a rate command is achievable with good accuracy. However, space based manipulators are different, typically have less structural stiffness, more motor and joint friction, and lower control loop cycle frequencies. These undesirable characteristics present a considerable Point of Resolution (POR) control problem for space based, kinematically redundant manipulators for the following reason: a kinematically redundant manipulator requires an arbitrary constraint to solve for the joint rate commands. A space manipulator will not respond to joint rate commands because of these characteristics. A space based manipulator simulation, including free end rigid body dynamics, motor dynamics, motor striction/friction, gearbox backlash, joint striction/friction, and Space Station Remote Manipulator System type configuration parameters, is used to evaluate the performance of a documented resolved rate control law. Alternate schemes which include torque control are also evaluated.

Robert W Bailey↗
NASA NTRS1990

Design of a telerobotic controller with joint torque sensors

The purpose was to analytically show how to design a joint controller for a telerobotic system when joint torque sensors are available. Other sensors such as actuator position, actuator velocity, joint position, and joint velocity are assumed to be accessible; however, the results will also be useful when only partial measurements are available. The controller presented can be applied to either mode of operation of a manipulator (i.e., teleoperation or robotic). Mechanical manipulators with high levels of friction are assumed. The results are applied to a telerobotic system built for NASA. Very high levels of friction have been reduced using high-gain feedback while avoiding limit cycles.

Jansen, J. F.↗
NASA NTRS1992

Torque Tube Stiffens Trailer Frame

Trailer frame incorporates longitudinal torque tube absorbing torsional loads and stiffening trailer. Used to transport large cylindrical objects like pressure vessels, tanks, and rocket engines without subjecting them to damage or excessive loads.

Macmartin, Malcolm J.↗
NASA NTRS1992

Torque, Tension, And Friction In Bolts

Improved equations predict relationships among tension in bolt, torque applied to bolt during installation, effective coefficient of friction, and number of times bolt has been installed. Bolted joints designed with new equations, use fewer and/or smaller bolts to carry same loads, reducing weights.

Morawski, Julian↗
NASA NTRS1991

Aerodynamic design of a Coanda induced force and thruster anti-torque system

A general method of analysis of the external and internal aerodynamics of a generic Coanda induced circulation anti-torque system is presented. The technique gives moment about the yaw axis and download induced on the boom as well as the force developed by an aft jet. The external flows including downwash, wake swirl and the boom circulation are considered. The internal flow and losses through the duct, fan, blown slots, cascades and nozzle are considered on a step-by-step basis. Limited comparison is made with open data where available.

Velkoff, Henry R.↗
NASA NTRS1991

Manufacturing techniques - Split torque path helicopter transmission

A description of the manufacturing techniques, capital equipment, tooling plan, and assembly methods necessary to manufacture the split torque path gearbox is presented. This transmission was designed and built for the advanced rotorcraft transmission program of the U.S. Army and NASA. Consideration is given to the engineering technology advancements along with a description of the integrated product development team process.

Mitchell, George D., Jr.↗
NASA NTRS1991

Experiments with simplified computed-torque controllers for free-flying robots

The effect of neglecting base accelerations in an inertial space endpoint computed-torque (CT) controller is examined. Numerical simulations predict a rather wide set of conditions under which CT controllers can neglect base accelerations in their dynamic model with insignificant performance degradation. Two predictions are experimentally verified with a laboratory robot. These two experiments show that negligible additional endpoint controller error results with a simplified CT controller for the given robot mass parameters and manipulator articulation.

Koningstein, R.↗
NASA NTRS1993

Noncontact Measurement Of Shaft Speed, Torque, And Power

Noncontact fiber-optic sensor and associated electronic equipment measure twist and speed of rotation of shaft. Measurements determine torque and power. Response of sensor remains linear even at cryogenic temperatures. Reflective strips on rotating shaft reflect two series of light pulses back into optical system. Bidirectional coupler in each of two optical fiber paths separates reflected light from incident light, sending it to photodiode for output to analog-to-digital converter and computer. Sensor requires no slip rings or telemetry to transfer signals from shaft. Well suited for providing data on performances of turbopumps for such cryogenic fluids as liquid oxygen and liquid hydrogen.

Madzsar, George C.↗
NASA NTRS1993

Compliant Gearing For Redundant Torque Drive

Elastomeric bearings make torque loads more nearly equal. Bearings couple drive shaft with ring spur gear. Inner elastomeric bearing radially stiff and circumferentially compliant, while outer elastomeric bearings circumferentially stiff and radially compliant. Combination accommodates minor variations in dimensions and placements of gears, shafts, and other components.

Isabelle, C.↗
NASA NTRS1993

Adjustable-Torque Truss-Joint Mechanism

Threaded pin tightened or loosened; tedious trial-and-error procedure shortened. Mechanism joining strut and node in truss structure preloaded to desired stress to ensure tight, compressive fit preventing motion of strut during loading or vibration. Preload stress on stack of Belleville spring washers adjusted by tightening or loosening threaded Belleville-washer-alignment pin. Pin turned, by use of allen wrench, to adjust compression preload on Belleville washers and adjusts joint-operating torque.

Bush, Harold G.↗
NASA NTRS1992

Numerical simulation of satellite-ring interactions - Resonances and satellite-ring torques

The Krook kinetic equation for planetary rings is numerically solved in two spatial dimensions and in time, with (1) interparticle collisions and (2) satellite-forcing, but (3) without self-gravity, for the case of a flattened planetary ring that undergoes gravitational perturbation by a nearby satellite. It is noted that the amplitude of wakes is limited by purely kinematic effects, even in the absence of collisions. Attention is given to the results of a simulation of an inner Lindblad-resonance location, as the distribution approaches steady state; these simulations do not show an increase in velocity dispersion in the resonance zone, obviating a net torque.

Brophy, Thomas G.↗
NASA NTRS1993

Wake-vortex structure from lift and torque induced on a following wing

A procedure based on vortex lattice theory to interpret the lift and torque measured on a following model in a wind tunnel is developed to retrieve the velocity distribution in the vortex wake that caused the induced forces. It is concluded that the retrieval procedure has a potential for reliably determining the structure of vortex wakes that trail from the wings of subsonic transport aircraft. Tests using idealized theoretical models show that the procedure is highly reliable and accurate. However, certain difficulties are found in the retrieval procedure when applied to actual data measured with following wings of various sizes in a wind tunnel.

Rossow, Vernon J.↗
NASA NTRS1934

The torsional stiffness of thin duralumin shells subjected to large torques

This report gives a simple method of estimating the torsional stiffness of thin shells, such as box beams or stressed-skin wings under large torque loads. A general efficiency chart for shells in torsion is established, based on the assumption that the efficiency of the web sheet in resisting deformation decreases linearly with the average stress. The chart is used to calculate the torsional deflections of eight box beams, a test wing panel, and a complete wing; the results of the calculations are shown in comparison with the test results. The agreement is probably as good as might be expected considering the empirical nature of the method and the well-known dispersion between results of tests on thin sheet-metal structures.

Kuhn, Paul↗
NASA NTRS1948

Charts for Determining Preliminary Values of Span-load, Shear, Bending-moment, and Accumulated-torque Distributions of Swept Wings of Various Taper Ratios

Contains charts for use in determining preliminary values of the spanwise-load, shear, bending-moment, and accumulated-torque distributions of swept wings. The charts are based on strip theory and include four aerodynamic-load distributions, two section-moment distributions, and two inertia-load distributions. The taper ratios considered cover the range from 1.0 to 0 and the results are applicable to any angle of sweep.

LOADS, MANEUVERING - WINGS↗
NASA NTRS1934

Negative Thrust and Torque Characteristics of an Adjustable-Pitch Metal Propeller

This report presents the results of a series of negative thrust and torque measurements made with a 4 foot diameter model of a conventional aluminum-alloy propeller. The tests were made in the 20-foot propeller-research tunnel of the National Advisory Committee for Aeronautics. The results show that the negative thrust is considerably affected by the shape and size of the body behind the propeller, that the maximum negative thrust increases with decrease in blade-angle setting, and that the drag of a locked propeller may be greatly reduced by feathering it into the wind. Several examples of possible applications of the data are given.

Hartman, Edwin P↗