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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Northrop F-5F shark nose development

During spin susceptibility testing of the Northrop F-5F airplane, two erect spin entries were obtained from purely longitudinal control inputs at low speed. Post flight analysis of the data showed that the initial yaw departure occurred at zero sideslip, and review of wind tunnel data showed significant yawing moments present at angles of attack well above stall. Further analysis of this wind tunnel data indicated that the yawing moments were being generated by the long slender nose of the airplane. Redesign of the nose was accomplished, resulting in a nose configuration which completely alleviated the asymmetric yawing moments.

Edwards, O. R.↗
NASA NTRS1981

Effects of mistuning on bending-torsion flutter and response of a cascade in incompressible flow

The effect of small differences between the individual blades (mistuning) on the aeroelastic stability and response of a cascade were studied. The aerodynamic, inertial, and structural coupling between the bending and torsional motions of each blade and the aerodynamic coupling between the blades was considered. A digital computer program was developed to conduct parametric studies. Results indicate that the mistuning has a beneficial effect on the coupled bending torsion and uncoupled torsion flutter. On forced response, however, the effect may be either beneficial or adverse, depending on the engine order of the forcing function. The results also illustrate that it may be feasible to utilize mistuning as a passive control to increase flutter speed while maintaining forced response at an acceptable level.

Kaza, K. R. V.↗
NASA NTRS1981

Effects of mistuning on bending-torsion flutter and response of a cascade in incompressible flow

This paper presents an investigation of the effects of blade mistuning on the aeroelastic stability and response of a cascade in incompressible flow. The aerodynamic, inertial, and structural coupling between the bending and torsional motions of each blade and the aerodynamic coupling between the blades are included in the formulation. A digital computer program was developed to conduct parametric studies. Results indicate that the mistuning has a beneficial effect on the coupled bending-torsion and uncoupled torsion flutter. The effect of mistuning on forced response, however, may be either beneficial or adverse, depending on the engine order of the forcing function. Additionally, the results illustrate that it may be feasible to utilize mistuning as a passive control to increase flutter speed while maintaining forced response at an acceptable level.

Kaza, K. R. V.↗
NASA NTRS1981

The Lick Observatory charge-coupled device /CCD/ and controller

A description is given of a flexible microprocessor-based controller for charge-coupled device two-dimensional detectors. It is noted that the controller can operate under manual control or as a slave to a remote computer linked by coaxial cable. The system is discussed, together with data taken at the telescope and in the laboratory. The flexibility of the controller derives from its modular form and from the use of a programmable 8-bit microprocessor to control and sequence the electronic logic. The electronic circuits for such functions as signal processing, clock sequencing, voltage level adjustment, and temperature control are on small individual plug-in cards, making future improvements and changes simple. The software of the microprocessor is stored in erasable, programmable, read-only memory. Among the limitations of the controller is a scan speed of roughly 35 microsec per pixel.

Robinson, L. B.↗
NASA NTRS1982

Description of the 3 MW SWT-3 wind turbine at San Gorgonio Pass, California

The SWT-3 wind turbine, a microprocessor controlled three bladed variable speed upwind machine with a 3MW rating that is presently operational and undergoing system testing, is discussed. The tower, a rigid triangular truss configuration, is rotated about its vertical axis to position the wind turbine into the prevailing wind. The blades rotate at variable speed in order to maintain an optimum 6 to 1 tip speed ratio between cut in and fated wind velocity, thereby maximizing power extraction from the wind. Rotor variable speed is implemented by the use of a hydrostatic transmission consisting of fourteen fixed displacement pumps operating in conjunction with eighteen variable displacement motors. Full blade pitch with on-off hydraulic actuation is used to maintain 3MW of output power.

Rybak, S. C.↗
NASA NTRS1985

Signal Analysis of Gas Tungsten Arc Welds

Gas tungsten arc welding is a process in which the input parameters such as current, voltage and travel speed, can be easily controlled and/or monitored. However, weld quality is not solely a function of these parameters. An adaptive method of observing weld quality is desired to improve weld quality assurance. The use of dynamic electrical properties of the welding arc as a weld quality monitor was studied. The electrical properties of the arc are characterized by the current voltage transfer function. The hardware and software necessary to collect the data at a maximum rate of 45 kHz and to allow the off-line processing of this data are tested. The optimum input current waveform is determined. Bead-on-plate welds to observe such characteristics of the weld as the fundamental frequency of the puddle are studied. Future work is planned to observe changes of the arc response with changes in joint geometry, base metal chemistry, and shielding gas composition are discussed.

Eagar, T. W.↗
NASA NTRS1986

Effects of damping on the control dynamics of the space shuttle based on tethered systems

The analysis of the effects of damping on the control dynamics of the space shuttle based on tethered systems suggest that a relatively simple point mass model can provide useful information concering librational dynamics during development and retrieval of the tethered satellites. The results show that a nonlinear tension control strategy in conjunction with a suitable choice of gains and realistic damping can lead to stable retrieval maneuver with amplitudes in pitch and roll limited to acceptable values. Longitudinal and lateral vibrations of the tether are strongly coupled and can lead to the slackening of the tether. Tether vibrations can be controlled quite effectively by speeding up the retrieval at smaller tether length and/or using thruster.

Modi, V. J.↗
NASA NTRS1986

Multiaxis aircraft control power from thrust vectoring at high angles of attack

Extensive research programs conducted at the Langley Research Center have shown that thrust vectoring can be provided by multifunction (nonaxisymmetric) nozzles. Most of this research has been conducted on pitch vectoring at both static and forward flight conditions. Recent efforts have been aimed at evaluating yaw vectoring concepts at static (wind off) conditions. This paper summarizes results for three different twin-engine fighter configurations tested over a Mach number range of 0.15 to 2.47 at angles of attack up to 35 deg. The objective of these investigations was to determine the multiaxis control power characteristics provided by thrust vectoring. All three configurations employed two-dimensional convergent-divergent nozzles which provided pitch vectoring by differential deflection of the upper and lower nozzle divergent flaps. Three different means of yaw vectoring were tested: (1) a translating nozzle sidewall; (2) yaw flaps located in the nozzle sidewalls; and (3) canted nozzles. These investigations were conducted in the Langley 16-Foot Transonic Tunnel and the Lewis 10x10-Foot Supersonic Tunnel. Longitudinal and direction control power from thrust vectoring was greater than that provided by aerodynamic control effectors at low speed or at high angles of attack.

Capone, F. J.↗
NASA NTRS1987

High speed precision motion strategies for lightweight structures

Work during the recording period proceeded along the lines of the proposal, i.e., three aspects of high speed motion planning and control of flexible structures were explored: fine motion control, gross motion planning and control, and automation using light weight arms. In addition, modeling the large manipulator arm to be used in experiments and theory has lead to some contributions in that area. These aspects are reported below. Conference, workshop and journal submissions, and presentations related to this work were seven in number, and are listed. Copies of written papers and abstracts are included.

Book, Wayne J.↗
NASA NTRS1986

Multiaxis aircraft control power from thrust vectoring at high angles of attack

Extensive research programs conducted at the Langley Research Center have shown that thrust vectoring can be provided by multifunction (nonaxisymmetric) nozzles. Most of this research has been conducted on pitch vectoring at both static and forward flight conditions. Recent efforts have been aimed at evaluating yaw vectoring concepts at static (wind off) conditions. This paper summarizes results for three different twin-engine fighter configurations tested over a Mach number range of 0.15 to 2.47 at angles of attack up to 35 deg. The objective of these investigations was to determine the multiaxis control power characteristics provided by thrust vectoring. All three configurations employed two-dimensional convergent-divergent nozzles which provided pitch vectoring by differential deflection of the upper and lower nozzle divergent flaps. Three different means of yaw vectoring were tested: (1) a translating nozzle sidewall; (2) yaw flaps located in the nozzle sidewalls; and (3) canted nozzles. These investigations were conducted in the Langley 16-Foot Transonic Tunnel and the Lewis 10 x 10-Foot Supersonic Tunnel. Longitudinal and direction control power from thrust vectoring was greater than that provided by aerodynamic control effectors at low speed or at high angles of attack.

Capone, Francis J.↗
NASA NTRS1987

Use of voice recognition for control of a robotic welding workcell

This paper describes work underway to evaluate the effectiveness of voice recognition systems as an element in the control of a robotic welding workcell. Factors being considered for control include program editor access security, preoperation checklist requirements, welding process variable control, and robot manipulator motion overrides. In the latter two categories, manual vocal control is being compared against manual tactile control and fully automatic control in terms of speed of response, accuracy, stability, reliability, and safety.

Watson, J. Kevin↗
NASA NTRS1989

A seal test facility for the measurement of isotropic and anisotropic linear rotordynamic characteristics

A new seal test facility for measuring high-pressure seal rotor-dynamic characteristics has recently been made operational at Case Western Reserve University (CWRU). This work is being sponsored by the Electric Power Research Institute (EPRI). The fundamental concept embodied in this test apparatus is a double-spool-shaft spindle which permits independent control over the spin speed and the frequency of an adjustable circular vibration orbit for both forward and backward whirl. Also, the static eccentricity between the rotating and non-rotating test seal parts is easily adjustable to desired values. By accurately measuring both dynamic radial displacement and dynamic radial force signals, over a wide range of circular orbit frequency, one is able to solve for the full linear-anisotropic model's 12 coefficients rather than the 6 coefficients of the more restrictive isotropic linear model. Of course, one may also impose the isotropic assumption in reducing test data, thereby providing a valid qualification of which seal configurations are well represented by the isotropic model and which are not. In fact, as argued in reference (1), the requirement for maintaining a symmetric total system mass matrix means that the resulting isotropic model needs 5 coefficients and the anisotropic model needs 11 coefficients.

Adams, M. L.↗
NASA NTRS1989

An update of commercial infrared sensing and imaging instruments

A classification of infrared sensing instruments by type and application, listing commercially available instruments, from single point thermal probes to on-line control sensors, to high speed, high resolution imaging systems is given. A review of performance specifications follows, along with a discussion of typical thermographic display approaches utilized by various imager manufacturers. An update report on new instruments, new display techniques and newly introduced features of existing instruments is given.

Kaplan, Herbert↗
NASA NTRS1990

Performance of a 300 Mbps 1:16 serial/parallel optoelectronic receiver module

Optical interconnects are being considered for the high speed distribution of multiplexed control signals in GaAs monolithic microwave integrated circuit (MMIC) based phased array antennas. The performance of a hybrid GaAs optoelectronic integrated circuit (OEIC) is described, as well as its design and fabrication. The OEIC converts a 16-bit serial optical input to a 16 parallel line electrical output using an on-board 1:16 demultiplexer and operates at data rates as high as 30b Mbps. The performance characteristics and potential applications of the device are presented.

Richard, M. A.↗
NASA NTRS1991

CFD validation of a supersonic laminar flow control concept

A three-dimensional Navier-Stokes code is used in conjunction with a linear compressible stability analysis code to develop a numerical procedure for prediction of laminar flow transition. The procedure is applied to a modified F-16XL fighter with a laminar flow control glove at supersonic speed. Details of boundary layer stability analysis indicate that, computationally, laminar flow could be realized on the highly swept wing in the absence of the leading edge attachment-line contamination. Effects of the three-dimensionality of the flow were shown to be important in the boundary layer stability analysis. The numerically predicted surface pressures compare favorably with the flight test data.

Woan, Chung-Jin↗
NASA NTRS1990

Performance of a 300 Mbps 1:16 serial/parallel optoelectronic receiver module

Optical interconnects are being considered for the high speed distribution of multiplexed control signals in GaAs MMIC-based phased array antennas. This paper describes the performance of a hybrid GaAs optoelectronic integrated circuit (OEIC), along with a description of its design and fabrication. The OEIC converts a 16-bit serial optical input to a 16 parallel line electrical output using an on-board 1:16 demultiplexer and operates at data rates as high as 305 Mbps. The performance characteristics as well as potential applications of the device are presented.

Richard, M. A.↗
NASA NTRS1992

Aerodynamic Shutoff Valve

Aerodynamic flow achieved by adding fixed fairings to butterfly valve. When valve fully open, fairings align with butterfly and reduce wake. Butterfly free to turn, so valve can be closed, while fairings remain fixed. Design reduces turbulence in flow of air in internal suction system. Valve aids in development of improved porous-surface boundary-layer control system to reduce aerodynamic drag. Applications primarily aerospace. System adapted to boundary-layer control on high-speed land vehicles.

Horstman, Raymond H.↗
NASA NTRS1992

An electronic pan/tilt/zoom camera system

A small camera system is described for remote viewing applications that employs fisheye optics and electronics processing for providing pan, tilt, zoom, and rotational movements. The fisheye lens is designed to give a complete hemispherical FOV with significant peripheral distortion that is corrected with high-speed electronic circuitry. Flexible control of the viewing requirements is provided by a programmable transformation processor so that pan/tilt/rotation/zoom functions can be accomplished without mechanical movements. Images are presented that were taken with a prototype system using a CCD camera, and 5 frames/sec can be acquired from a 180-deg FOV. The image-tranformation device can provide multiple images with different magnifications and pan/tilt/rotation sequences at frame rates compatible with conventional video devices. The system is of interest to the object tracking, surveillance, and viewing in constrained environments that would require the use of several cameras.

Zimmermann, Steve↗