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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Six degree of freedom FORTRAN program, ASTP docking dynamics, users guide

The digital program ASTP Docking Dynamics as outlined is intended to aid the engineer using the program to determine the docking system loads and attendant vehicular motion resulting from docking two vehicles that have an androgynous, six-hydraulic-attenuator, guide ring, docking interface similar to that designed for the Apollo/Soyuz Test Project (ASTP). This program is set up to analyze two different vehicle combinations: the Apollo CSM docking to Soyuz and the shuttle orbiter docking to another orbiter. The subroutine modifies the vehicle control systems to describe one or the other vehicle combinations; the rest of the vehicle characteristics are changed by input data. To date, the program has been used to predict and correlate ASTP docking loads and performance with docking test program results from dynamic testing. The program modified for use on IBM 360 computers. Parts of the original docking system equations in the areas of hydraulic damping and capture latches are modified to better describe the detail design of the ASTP docking system.

Mount, G. O., Jr.↗
NASA NTRS1975

An elementary psychophysical model to predict ride comfort in the combined stress of multiple degrees of freedom

The quality of airplane rides probably will become increasingly important to passengers, particularly in terminal area operations and on short haul trips. The development of models to predict ride comfort is considered. An elementary model concept is presented herein and compared with subjective ride comfort response ratings measured on actual scheduled airline flights and simulated flights.

Stone, R. W., Jr.↗
NASA NTRS1975

Development of a digital electronic rebalance loop for a dry tuned-rotor two degree-of-freedom gyroscope

Digital electronic rebalance loops were designed and implemented in brassboard form to capture both X and Y axes of the Kearfott Gyroflex. The loops were width-modulated binary types using a 614.4 kHz keying signal and a 2.4 kHz sample frequency. The loops were designed for a torquing rate of 2 deg/sec (70.6 mA torquing current) and a data resolution of 23.4 milli-arc-sec per data pulse. Design considerations, implementation details, and preliminary experimental results are presented.

Blalock, T. V.↗
NASA NTRS1976

Flight data identification of six degree-of-freedom stability and control derivatives of a large crane type helicopter

Flight test data from a large 'crane' type helicopter were collected and processed for the purpose of identifying vehicle rigid body stability and control derivatives. The process consisted of using digital and Kalman filtering techniques for state estimation and Extended Kalman filtering for parameter identification, utilizing a least squares algorithm for initial derivative and variance estimates. Data were processed for indicated airspeeds from 0 m/sec to 152 m/sec. Pulse, doublet and step control inputs were investigated. Digital filter frequency did not have a major effect on the identification process, while the initial derivative estimates and the estimated variances had an appreciable effect on many derivative estimates. The major derivatives identified agreed fairly well with analytical predictions and engineering experience. Doublet control inputs provided better results than pulse or step inputs.

Tomaine, R. L.↗
NASA NTRS1975

Return-to-launch-site three degree of freedom analysis, constant inertial attitude during the fuel dissipation phase

Results are presented of a study to show the effect of selecting a constant inertial attitude during the fuel dissipation phase of a return-to-launch-site abort. Results are also presented which show that the selection of the constant inertial attitude will affect the arrival point on the range-velocity target line. An alternate selection of the inertial attitude will provide control over the trajectory shape.

Bown, R. L.↗
NASA NTRS1976

Preliminary design of a redundant strapped down inertial navigation unit using two-degree-of-freedom tuned-gimbal gyroscopes

This redundant strapdown INS preliminary design study demonstrates the practicality of a skewed sensor system configuration by means of: (1) devising a practical system mechanization utilizing proven strapdown instruments, (2) thoroughly analyzing the skewed sensor redundancy management concept to determine optimum geometry, data processing requirements, and realistic reliability estimates, and (3) implementing the redundant computers into a low-cost, maintainable configuration.

Source record↗
NASA NTRS1977

On aerodynamic coupling between lateral and longitudinal degrees of freedom

An oscillatory technique for routine measurement of all the direct, cross and cross-coupling moment derivatives due to pitching and yawing has been developed and a series of comprehensive results at Mach numbers 0.7 and 0.25 and at angles of attack up to 40 deg has been obtained in a large wind tunnel. It was found that some of the dynamic cross-coupling derivatives, that at low angles of attack were all zero, at higher angles of attack could reach values that rendered the pertinent cross-coupling terms in the equations of motion comparable in magnitude to the well-established damping terms. Large nonlinear variations with angle of attack were observed in many of the measured derivatives including the important damping-in-pitch and damping-in-yaw derivatives. It was concluded that it may be desirable to include some dynamic cross-coupling derivatives, and the functional variation with angle of attack of many derivatives, in the equations of motion, and to consider all these equations simultaneously, rather than in separate longitudinal and lateral groups.

Orlik-Rueckemann, K. J.↗
NASA NTRS1980

Analysis and improvement of contact dynamics simulation using the six degree of freedom motion system

The 6 DOF motion system was employed for closed loop simulation of the contact dynamics involved in the docking of two satellites. Under most initial conditions the system gives inaccurate results. It is well known that the presence of a time lag can generate instability in closed loop systems. In order to see if the time lag (about 200 ms.) in the 6 DOF system can can satisfactorily account for its errors, a simple computer model of the system incorporating this lag and other revelant parameters was implemented. The model in fact does predict all the observed rebound errors with reasonable precision. Also, since it is probable that the time delay can only be reduced but not eliminated, various compensation schemes were devised. Two give adequate correction for delays under 100 ms for a non preloaded probe. More powerful schemes may be adequate for the present 200 ms. environment and the presence of a preload.

Brown, R. C.↗
NASA NTRS1981

Main rotor six degree-of-freedom isolation system analysis

The design requirements of the system have been defined and an isolator concept satisfies these requirements identified. Primary design objectives for the isolation system are 90% attenuation of all NP main rotor shaft loads at a weight penalty less than or equal to 1% of design gross weight. The configuration is sized for a UH-60A BLACK HAWK helicopter and its performance, risk, and system integration were evaluated through a series of parametric studies. Preliminary design was carried forward to insure that the design is practical and that the details of the integration of the isolator into the helicopter system are considered. Alternate ground and flight test demonstration programs necessary to verify the proposed isolator design are defined.

Eastman, L. B.↗
NASA NTRS1982

A two-degree-of-freedom flutter mount system with low damping for testing rigid wings at different angles of attack

A wind tunnel model mount system for conducting flutter research using a rigid wing was developed. The wing is attached to a splitter plate so that the two move as one rigid body. The splitter plate is supported away from the tunnel wall by a system of rods with fixed fixed and conditions. The rods flex in such a way that only pitch and plunge oscillations are permitted. At the tunnel wall the rods are attached to a remotely controlled turntable so that angle of attack can be varied. Wind tunnel data obtained by using the mount system are presented for a supercritical and a conventional airfoil. Both classical flutter and stall flutter data are presented.

Farmer, M. G.↗
NASA NTRS1983

Two-Degree-of-Freedom Mount System for Flutter Models

Flexible rods replace conventional bearing supports to minimize structural damping. Aerodynamic damping not masked by effects of mount system, making more accurate studies possible of how aerodynamic damping varies as flow over model changed. New system called PAPA.

Farmer, M. G.↗
NASA NTRS1985

Display comparison for six-degree-of-freedom force/torque control

The experimental design and the results of a study of a force and torque sensing and display (FTSD) system, developed at the Jet Propulsion Laboratory, are presented. The FTSD system was incorporated into the one-g version of the Space Shuttle Remote Manipulator System (RMS). The tests consisted of evaluating alternative graphics formats for presenting force and torque information at the RMS work station, and of testing the utility of the sensor and the display system as an aid to specific RMS tasks. The participating subjects were all trained RMS operators with experience on the one-g version of the system, three of them with previous experience using the Space Shuttle RMS on orbit. The results support the use of the FTSD system as an aid to RMS operations: the system was found to facilitate the control of forces when the RMS is under partially or wholly constrained conditions. The graphics format employed in the present version of the FTSD system was found to be superior to earlier formats.

Baggen, A.↗
NASA NTRS1985

Frequency domain solutions to multi-degree-of-freedom, dry friction damped systems under periodic excitation

The anticipated low damping level in large space structures (LSS) has been a major concern for the designers of these structures. Low damping degrades the free response and complicates the design of shape and attitude controllers for flexible spacecraft. Dry friction damping has been considered as a means of increasing the passive damping of LSS, by placing it in the joints and connecting junctures of structures. However, dry friction is highly nonlinear and, hence, analytical investigations are difficult to perform. Here, a multi-harmonic, frequency domain solution technique is developed and applied to a multi-DOF, dry friction damped system. It is seen that the multi-harmonic method is much more accurate than traditional, one harmonic solution methods. The method also compares well with time integration. Finally, comparisons are made with experimental results.

Ferri, A. A.↗
NASA NTRS1986

The flight and impact dispersion of the Comet Nucleus Penetrator - A six-degree-of-freedom simulation

The flight dynamics of a Penetrator probe which, as part of a Comet Rendezvous and Asteroid Flyby mission will impact a known periodic comet, possibly Hempel 2, and penetrate beneath the surface to obtain measurements, is discussed. The mission is described, including the penetrator-separation dynamics, the dynamics during initial coast and rocket thrust phase, and the final coast to impact. The effects on the results that may be caused by the comet nucleus gravity field variations, uncertainty in the spacecraft state vector, the spacecraft pointing accuracy, initial separation errors, and rocket motor thrust errors are examined.

Mascy, A. C.↗
NASA NTRS1987

Development of hardwares and computer interface for a two-degree-of-freedom robot

The research results that were obtained are reviewed. Then the robot actuator, the selection of the data acquisition system, and the design of the power amplifier will be discussed. The machine design of the robot manipulator will then be presented. After that, the integration of the developed hardware into the open-loop system will also be discussed. Current and future research work is addressed.

Nguyen, Charles C.↗
NASA NTRS1987

Traction-drive, seven-degree-of-freedom telerobot arm: A concept for manipulaton in space

As man seeks to expand his dominion into new environments, the demand increases for machines that perform useful functions in remote locations. This new concept for manipulation in space is based on knowledge and experience gained from manipulator systems developed to meet the needs of remote nuclear applications. It merges the best characteristics of teleoperation and robotic technologies. The design goals for the telerobot, a mechanical description, and technology areas that must be addressed for successful implementation are presented and discussed. The concept incorporates mechanical traction drives, redundant kinematics, and modular arm subelements to provide a backlash-free manipulator capable of obstacle avoidance.

Kuban, D. P.↗
NASA NTRS1988

Cartesian path control of a two-degree-of-freedom robot manipulator

The problem of cartesian trajectory control of a closed-kinematic chain mechanism robot manipulator with possible space station applications is considered. The study was performed by both computer simulation and experimentation for tracking of three different paths: a straight line, a sinusoid and a circle. Linearization and pole placement methods are employed to design controller gains. Results show that the controllers are robust and there are good agreements between simulation and experimentation. Excellent tracking quality and small overshoots are also evident.

Nguyen, Charles C.↗
NASA NTRS1989

One-degree-of-freedom motion induced by modeled vortex shedding

The motion of an elastically supported cylinder forced by a nonlinear, quasi-static, aerodynamic model with the unusual feature of a motion-dependent forcing frequency was studied. Numerical solutions for the motion and the Lyapunov exponents are presented for three forcing amplitudes and two frequencies (1.0 and 1.1 times the Strouhal frequency). Initially, positive Lyapunov exponents occur and the motion can appear chaotic. After thousands of characteristic times, the motion changes to a motion (verified analytically) that is periodic and damped. This periodic, damped motion was not observed experimentally, thus raising questions concerning the modeling.

Yates, L. A.↗