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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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Program analyzes general nonaxisymmetric and nonsynchronous transient and steady-state rotor dynamic performance of bending- and shear-wise flexible rotor-bearing system under various operating conditions. Program can be used as analytical study tool for general transient spin-speed and/or non-axisymmetric rotor motion.
Versatile standardized pulse modulation nondissipatively regulated control signal processing circuits were applied to three most commonly used dc to dc power converter configurations: (1) the series switching buck-regulator, (2) the pulse modulated parallel inverter, and (3) the buck-boost converter. The unique control concept and the commonality of control functions for all switching regulators have resulted in improved static and dynamic performance and control circuit standardization. New power-circuit technology was also applied to enhance reliability and to achieve optimum weight and efficiency.
The Analog Signal to Discrete Time Interval Converter microminiaturized module was utilized to control the signal conditioner power supplies. The multi-loop control provides outstanding static and dynamic performance characteristics, exceeding those generally associated with single-loop regulators. Eight converter boards, each containing three independent dc to dc converter, were built, tested, and delivered.
The mechanical and electrical characteristics of the conical arc-chamber driver and the 1450-microfarad capacitor bank are described. The system dynamic performance can be approximated by a second-order nonlinear equation. The discharge of the capacitor bank into the conical arc-chamber was investigated at a variety of initial conditions. Details of the discharge are explained and compared for typical performance with both hydrogen and helium arc-chamber gases. At peak current the hydrogen plasma resistivity is significantly higher than that of the helium plasma and this, in part, accounts for the better shock speed performance with hydrogen. The lower melting and boiling point exploding wires of aluminum, copper, and stainless steel produced higher shock speed performance than the apparently nonexploding tungsten wire.
A model of the human arm, emphasizing the neuromuscular mechanisms of feedback control, has been constructed. The various parameters and functions of physiological receptors in the feedback section have been classified into an automated category that can be incorporated in the prosthesis servo loop, and into a sensory category that should be communicated to the operator if control and dynamic performance are to be optimized. A scheme for simultaneous display of two such sensory parameters, i.e., fingertip pressure and elbow position, has been developed, implemented and evaluated. The neurophysiological mechanism of such displays, and the feasibility of sensory transformation, is discussed in this paper.
Evaluation of hot-pressed silicon nitride as a rolling-element bearing material. Two grades of hot-pressed silicon nitride balls were tested under rolling contact conditions in a five-ball fatigue tester. A digital computer program was used to predict the dynamic performance characteristics and fatigue life of high-speed ball bearings with silicon nitride balls relative to that with bearings containing steel balls. The results obtained include the finding that fatigue spalls on silicon nitride balls are similar in appearance to those obtained with typical bearing steels.
Gaseous squeeze film dampers are analyzed to determine the effect of periodic disturbance amplitude on the dynamic performance. Both circular and rectangular parallel surfaces are investigated. A solution of the nonlinear Reynolds equation is obtained by expanding the pressure in powers of the squeeze number, retaining up to and including terms of the order of the square of the squeeze number. The time dependent load characteristics are found. The effect of disturbance amplitude on the film stiffness and damping is given.
A program for the development and verification of drive-train dynamic technology is described along with its basis and the results expected from it. A central feature of this program is a drive-train test facility designed for the testing and development of advanced drive-train components, including shaft systems, dampers, and couplings. Previous efforts in designing flexible dynamic drive-train systems are reviewed, and the present state of the art is briefly summarized. The design of the test facility is discussed with major attention given to the formulation of the test-rig concept, dynamic scaling of model shafts, and the specification of design parameters. Specific efforts envisioned for the test facility are briefly noted, including evaluations of supercritical test shafts, stability thresholds for various sources and types of instabilities that can exist in shaft systems, effects of structural flexibility on the dynamic performance of dampers, and methods for vibration control in two-level and three-level flexible shaft systems.
Two dynamic pressure sources are described for the calibration of pogo pressure transducers used to measure oscillatory pressures generated in the propulsion system of the space shuttle. Rotation of a mercury-filled tube in a vertical plane at frequencies below 5 Hz generates sinusoidal pressures up to 48 kPa, peak-to-peak; vibrating the same mercury-filled tube sinusoidally in the vertical plane extends the frequency response from 5 Hz to 100 Hz at pressures up to 140 kPa, peak-to-peak. The sinusoidal pressure fluctuations can be generated by both methods in the presence of high pressures (bias) up to 55 MPa. Calibration procedures are given in detail for the use of both sources. The dynamic performance of selected transducers was evaluated using these procedures; the results of these calibrations are presented. Calibrations made with the two sources near 5 Hz agree to within 3% of each other.
Computer program mathematically describes complete hydraulic systems to study their dynamic performance. Program employs subroutines that simulate components of hydraulic system, which are then controlled by main program. Program is useful to engineers working with detailed performance results of aircraft, spacecraft, or similar hydraulic systems.
Static and dynamic performance of air cushion landing system is simulated in computer program that treats four primary ACLS subsystems: fan, feeding system, trunk, and cushion. Configuration of systems is sufficiently general to represent variety of practical designs.
A dynamic model of the National Transonic Facility (NTF) section and plenum chamber was developed. The model serves as a means for determining the dynamic performance of the NTF and the subsequent design of optimal control configurations, and is of one dimensional flow type as to facilitate computer simulation. The model allows for the simulation of the effects of test section blockage, boundary layer losses, slot flow required for supersonic flow generation, reentry flap position, and auxiliary plenum suction.
A real time hybrid simulation of the Pratt & Whitney F100-PW-F100 turbofan engine was used for linear-model generation. The linear models were used to analyze the effect of disturbances about an operating point on the dynamic performance of the engine. A procedure that disturbs, samples, and records the state and control variables was developed. For large systems, such as the F100 engine, the state vector is large and may contain high-frequency information not required for control. This, reducing the full-state to a reduced-order model may be a practicable approach to simplifying the control design. A reduction technique was developed to generate reduced-order models. Selected linear and nonlinear output responses to exhaust-nozzle area and main-burner fuel flow disturbances are presented for comparison.
A hybrid computer simulation of an Advanced Automotive Gas Turbine Powertrain System is reported. The system consists of a gas turbine engine, an automotive drivetrain with four speed automatic transmission, and a control system. Generally, dynamic performance is simulated on the analog portion of the hybrid computer while most of the steady state performance characteristics are calculated to run faster than real time and makes this simulation a useful tool for a variety of analytical studies.
The challenges that resulted from the unique configuration of the space shuttle and capabilities developed to meet these challenges are described. The methods and the organization that were developed to perform dynamic loads analyses on the space shuttle configuration and to assess dynamic data developed after design are discussed. Examples are presented from the dynamic loads analysis of the lift-off and maximum dynamic pressure portion of ascent. Also shown are orbital flight test results, for which selected predicted responses are compared to measured data for the lift-off and high-dynamic-pressure times of ascent. These results have generally verified the design analysis. However, subscale testing was found to be deficient in predicting full-scale results in two areas: the ignition overpressure at lift-off and the aerodynamics/plume interactions at high-q boost. In these areas, the results of the flight test program were accommodated with no impact to the vehicle design.
The dynamic performance of the primary mirror of the Large Deployable Reflector (LDR) is analyzed under conditions of typical external disturbances that would be encountered during normal space operation. The performance assessment is based upon the difference between the figure distortion errors of the incoming image and the mission figure tolerance requirements (rms surface accuracy error and jitter). The need for additional figure control of the incoming image is assessed, and other alternatives for figure control are presented, such as increased structural damping effects due to the uncertainty in the real damping characteristics.
Engineering changes made on the Voyager spacecraft during their explorations of the outer solar system are discussed. A recovery from a scan actuator fault, achieved by ground testing, in flight capability enhancement and testing, conservation of actuator usage and a set of contingency plans to substitute roll motion of the spacecraft for motion of the scan platform in the AZ direction, is discussed. General engineering improvements made are addressed, including a scan platform anticreep patch modification, an improvement of dynamic performance during maneuvers, and adaptive control of the attitude control deadband. Changes made in the power management are described. Finally, engineering improvements made in order to enhance scientific findings at the Uranus encounter are reviewed in detail. The two most important were the increased gyro drift turn rate capability to accommodate image motion compensation for the close fly-by of Miranda and the reduction in spacecraft rates to accommodate increased imaging exposure times without incurring excessive image smear.
The One Controller at a Time (1-CAT) methodology for designing digital controllers for Large Space Structures (LSS's) is introduced and illustrated. The flexible mode problem is first discussed. Next, desirable features of a LSS control system design methodology are delineated. The 1-CAT approach is presented, along with an analytical technique for carrying out the 1-CAT process. Next, 1-CAT is used to design digital controllers for the proposed Space Based Laser (SBL). Finally, the SBL design is evaluated for dynamical performance, noise rejection, and robustness.