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Results for “AUGMENTATION”

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 1,279 records · Page 71

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NASA NTRS1981

A study of a VTOL thrusting ejector in low speed flight, volume 2

An experimental investigation of V/STOL thrust augmenter wings in flight at slow forward speeds is reported. Two rectangular planforms of differing relative chord lengths were tested. The augmenters were positioned in the aft portion of the wing to produce increases in circulation lift. Two blown flap configurations were tested for comparison. Surface pressures as well as total forces and moments were obtained on the semispan models at two flap deflections and a range of momentum coefficients. Tabulations of surveys at the pressure augmenter exit, downwash surveys downstream of the wing, and force and moment data are included.

Stewart, V. R.↗

NASA NTRS1981

Motion-base simulator results of advanced supersonic transport handling qualities with active controls

Handling qualities of the unaugmented advanced supersonic transport (AST) are deficient in the low-speed, landing approach regime. Consequently, improvement in handling with active control augmentation systems has been achieved using implicit model-following techniques. Extensive fixed-based simulator evaluations were used to validate these systems prior to tests with full motion and visual capabilities on a six-axis motion-base simulator (MBS). These tests compared the handling qualities of the unaugmented AST with several augmented configurations to ascertain the effectiveness of these systems. Cooper-Harper ratings, tracking errors, and control activity data from the MBS tests have been analyzed statistically. The results show the fully augmented AST handling qualities have been improved to an acceptable level.

Feather, J. B.↗

NASA NTRS1981

Multivariable closed loop control analysis and synthesis for complex flight systems

A flight control system analysis and synthesis method is presented that is intended to be especially suitable for application to vehicles exhibiting complex dynamic characteristics. For such vehicles quantitative handling qualities specifications are not usually available. Howver, handling qualities objectives are specifically introduced in this method via the hypothesis of correlation between pilot ratings and the objective function of an optimal control model of the human pilot. Further, since augmentation and pilot operate in parallel, simultaneous determination of the augmentation and pilot model gains is required. Desirable augmented dynamics are obtained for a variety of complex systems and the method is experimentally verified in the case of simple pilot damper gain selection for optimum pitch tracking performance.

Schmidt, D. K.↗

NASA NTRS1984

V/STOL maneuverability and control

Maneuverability and control of V/STOL aircraft in powered-lift flight is studied with specific considerations of maneuvering in forward flight. A review of maneuverability for representative operational mission tasks is presented and covers takeoff, transition, hover, and landing flight phases. Maneuverability is described in terms of the ability to rotate and translate the aircraft and is specified in terms of angular and translational accelerations imposed on the aircraft. Characteristics of representative configurations are reviewed, including experience from past programs and expectations for future designs. The review of control covers the characteristics inherent in the basic airframe and propulsion system and the behavior associated with ontrol augmentation systems. Demands for augmented stability and control response to meet certain mission operational requirements are discussed. Experience from ground-based simulation and flight experiments that illustrates the impact of augmented stability and control on aircraft design is related by example.

Franklin, J. A.↗

NASA NTRS1984

Optimal cooperative control synthesis applied to a control-configured aircraft

A multivariable control augmentation synthesis method is presented that is intended to enable the designer to directly optimize pilot opinion rating of the augmented system. The approach involves the simultaneous solution for the augmentation and predicted pilot's compensation via optimal control techniques. The methodology is applied to the control law synthesis for a vehicle similar to the AFTI F16 control-configured aircraft. The resulting dynamics, expressed in terms of eigenstructure and time/frequency responses, are presented with analytical predictions of closed loop tracking performance, pilot compensation, and other predictors of pilot acceptance.

Schmidt, D. K.↗

NASA NTRS1981

Selected advanced aerodynamic and active control concepts development

A task for the Energy Efficient Transport program conducted: (1) The design and wind tunnel development of high-aspect-ratio supercritical wings, investigating the cruise speed regime and also high-lift. (2) The preliminary design and evaluation of an aircraft combining a high-aspect-ratio supercritical wing with a winglet. (3) Active Controls: The determination of criteria, configuration, and flying qualities associated with augmented longitudinal stability of a level likely to be acceptable for the next generation transport; and the design of a practical augmentation system. The baseline against which the work was performed and evaluated was the Douglas DC-X-200 twin engine derivative of the DC-10 transport. The supercritical wing development showed that the cruise and buffet requirements could be achieved and that the wing could be designed to realize a sizable advantage over today's technology. Important advances in high lift performance were shown. The design study of an aircraft with supercritical wing and winglet suggested advantages in weight and fuel economy could be realized. The study of augmented stability, conducted with the aid of a motion base simulator, concluded that a negative static margin was acceptable for the baseline unaugmented aircraft.

Source record↗

NASA NTRS1983

VTOL controls for shipboard operations

Piloted, moving-base simulations have been performed in the evaluation of several VTOL control system concepts during landings on a destroyer in adverse weather conditions. All the systems incorporated attitude control augmentation; most systems incorporated various types of translational control augmentation implemented either through aircraft attitude or, more directly, through the propulsion system (thrust magnitude and deflection). Only one of the control systems failed to provide satisfactory handling qualities in calm seas. Acceptable handling qualities in sea state 6 seem to require a system with control augmentation in all translational degrees of freedom.

Merrick, V. K.↗

NASA NTRS1984

The direct effects of strain on burning rates of composite solid propellants

A mathematical model is developed to predict burn rate augmentation due to strain in a composite solid propellant. The model assumes the effect is due to the ability of the flame to penetrate the small fissures and voids that form when a propellant is strained. The number and size of these fissures is obtained by applying a flaw propagation analysis to randomly distributed flaws that form when the binder-oxidizer particle bonds break under stress. A flame height is calculated with Summerfield's burn rate equation and is used to compute the burn rate augmentation based upon the additional burn area created when the flame penetrates the fissures. Comparisons are made with data obtained from published sources. The existence of threshold pressure and strains, above which augmentation occurs, is verified although the model predicts a lower threshold pressure and higher threshold strain than expected. Further results and applications of the model are discussed.

Langhenry, M. T.↗

NASA NTRS1985

Ground-based and in-flight simulator studies of flight characteristics of a twin-fuselage passenger transport airplane during approach and landing

Six-degree-of-freedom ground-based and in-flight simulator studies were conducted to evaluate the low-speed flight characteristics of a twin-fuselage passenger transport airplane and to compare these characteristics with those of a large, single-fuselage (reference) transport configuration similar to the Lockheed C-5A airplane. The primary piloting task was the approach and landing task. The results of this study indicated that the twin-fuselage transport concept had acceptable but unsatisfactory longitudinal and lateral-directional low-speed flight characteristics, and that stability and control augmentation would be required in order to improve the handling qualities. Through the use of rate-command/attitude-hold augmentation in the pitch and roll axes, and the use of several turn coordination features, the handling qualities of the simulated transport were improved appreciably. The in-flight test results showed excellent agreement with those of the six-degree-of-freedom ground-based simulator handling qualities tests. As a result of the in-flight simulation study, a roll-control-induced normal-acceleration criterion was developed. The handling qualities of the augmented twin-fuselage passenger transport airplane exhibited an improvement over the handling characteristics of the reference (single-fuselage) transport.

Grantham, W. D.↗

NASA NTRS1985

Performance characterization tests of a 1-kW resistojet using hydrogen, nitrogen and ammonia as propellants

A performance mapping test of a 1 kW radiatively heated resistojet demonstrated high specific impulse and efficiency with hydrogen, nitrogen and ammonia as propellants. The resistojet was based on an unmodified augmentation section of the flight-qualified Rocket Research Company Augmented Catalytic Thruster. Peak specific impulse values of 686.9 sec for hydrogen, 191.6 sec for nitrogen, and 342 sec for ammonia were demonstrated. A maximum specific impulse efficiency of 94.3 percent was demonstrated with hydrogen. Testing covered a thrust range of 27 to 112 mlbf with augmentation powers ranging from 300 to 1000 watts. A total of 83 runs accumulating 25 hours of operation were conducted with the three propellants. Comparison of specific impulse efficiency to other published resistojet performance data showed the radiatively heated resistojet compares favorably to other design concepts.

Miyake, C. I.↗

NASA NTRS1986

Experiments on high speed ejectors

Experimental studies were conducted to investigate the flow and the performance of thrust augmenting ejectors for flight Mach numbers in the range of 0.5 to 0.8, primary air stagnation pressures up to 107 psig (738 kPa), and primary air stagnation temperatures up to 1250 F (677 C). The experiment verified the existence of the second solution ejector flow, where the flow after complete mixing is supersonic. Thrust augmentation in excess of 1.2 was demonstrated for both hot and cold primary jets. The experimental ejector performed better than the corresponding theoretical optimal first solution ejector, where the mixed flow is subsonic. Further studies are required to realize the full potential of the second solution ejector. The research program was started by the Flight Dynamics Research Corporation (FDRC) to investigate the characteristic of a high speed ejector which augments thrust of a jet at high flight speeds.

Wu, J. J.↗

NASA NTRS1986

A survey of handling qualities criteria and their applications to high performance aircraft

Various handling qualities criteria and their application to high performance aircraft including state-of-the-art and highly augmented aircraft were surveyed. Neal-Smith, Bandwidth, Equivalent Systems, and Military Specification 8785 criteria are applied to flight test data from aircraft such as the F-8 Digital Fly-By-Wire, the YF-12, and an Advanced Fighter Aircraft. Backgrounds and example applications of each criteria are given. The results show that the handling qualities criteria investigated can be applied to highly augmented aircraft with fairly good results in most cases; however, since no one method excelled, more than one criteria should be used whenever possible. Equivalent time delays appear to be the most frequent critical factor in determining pilot rating levels of highly augmented aircraft.

Peahl, D. L.↗

NASA NTRS1986

Control of V/STOL aircraft

This paper deals with control of V/STOL aircraft in powered-lift flight. A review of representative operational mission tasks is presented for the take-off, transition, hover and landing flight phases. Characteristics inherent in the basic airframe and propulsion system and the behavior associated with control augmentation systems are considered. Demands for augmented stability and control response to meet certain mission operational requirements are discussed. Experience from ground-based simulation and flight experiments that illustrates the impact of augmented stability and control on aircraft design is related by example.

Franklin, J. A.↗

NASA NTRS1987

Contingency power for small turboshaft engines using water injection into turbine cooling air

Because of one engine inoperative requirements, together with hot-gas reingestion and hot day, high altitude takeoff situations, power augmentation for multiengine rotorcraft has always been of critical interest. However, power augmentation using overtemperature at the turbine inlet will shorten turbine life unless a method of limiting thermal and mechanical stresses is found. A possible solution involves allowing the turbine inlet temperature to rise to augment power while injecting water into the turbine cooling air to limit hot-section metal temperatures. An experimental water injection device was installed in an engine and successfully tested. Although concern for unprotected subcomponents in the engine hot section prevented demonstration of the technique's maximum potential, it was still possible to demonstrate increases in power while maintaining nearly constant turbine rotor blade temperature.

Biesiadny, Thomas J.↗

NASA NTRS1987

Contingency power for small turboshaft engines using water injection into turbine cooling air

Biesiadny, Thomas J.↗

NASA NTRS1988

Concepts for robot motion primitives required for space station teleoperations

Ground controlled teleoperations are expected to be used to augment Space Station manned extravehicular activities (EVA) and Intravehicular activities (IVA). However, ground controlled teleoperations will encounter communications time delays of from 3 to 8 secs. Time delays greater than 1 sec have been shown to be detrimental to safe and efficient teleoperations. Therefore, concepts must be developed to overcome the hazards and limitations of time delays when performing teleoperations using robots. The concept for robot motion primitives incorporate force/torque and tactile sensor feedback to implement the degree of autonomy required for interactive, ground controlled telerobotics. Several primitives are studied that augment human initiated actions by providing rapid response interaction with the physical environment of a telerobot. These primitives are detailed. They constitute a level of intelligent sensing and reaction required to augment human actions through autonomous interaction with the physical environment.

Grover, Jeffrey L.↗

NASA NTRS1988

Flight evaluation of an integrated control and display system for high-precision manual landing flare of powered-lift STOL aircraft

An account is given of the features and performance of a manual landing flare and touchdown system capable of great precision, as demonstrated by its installation in the NASA Quiet Short-haul Research Aircraft (QSRA). The integrated cockpit display and closed-loop control employed constitutes a trajectory-augmentation system that extends QSRA flight control from augmentation of altitude, flight path angle, and airspeed, to the augmentation of the trajectory itself. The + or - 18 ft touchdown dispersion achieved is approximately equal to that obtained during aircraft carrier trials of the same aircraft.

Hynes, Charles S.↗

NASA NTRS1989

Subharmonic and fundamental high amplitude excitation of an axisymmetric jet

A circular jet was excited simultaneously by two different harmonically related tones. Data for three pairs of Strouhal numbers (St(D) = f*D/U (sub j) = 0.2 and 0.4, 0.3 and 0.6, 0.4 and 0.8). For each case the initial phase difference between the two waves was varied in steps of 45 deg, for one full cycle and the level of the fundamental and subharmonic forcing were varied independently over the range of 0.1 to 7 percent of the jet exit velocity. Our initial findings concurred with published findings, such as a critical level of the fundamental is required for subharmonic augmentation, the initial phase difference is critical in determining whether the subharmonic is augmented or suppressed. The detailed documentation of several aspects of this phenomenon all measured in one and the same experimental facility in a controlled manner, bring out several important points that eluded previous researchers: (1) At high amplitudes of the fundamental and subharmonic forcing levels the subharmonic augmentation is independent of the initial phase difference. (2) Contrary to the earlier belief that stable pairing could be produced only with an initial laminar boundary layer, the present work shows that by the two-frequency excitation method this phenomenon can be induced over a range of conditions for a jet with an initially turbulent boundary layer. (3) It is seen that two-frequency excitation is indeed more effective than single frequency excitation in jet mixing enhancement. Higher spreading rates seem to go along with higher subharmonic levels.

Raman, Ganesh↗