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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

V/STOL flying qualities research using the X-22A

The X-22A has four ducted propellers and four engines. The engines are connected to a common system of rotating shafts which distribute propulsive power to the four propellers. Changes in the direction of the thrust vector are accomplished by rotating the ducts, which are interconnected so that all rotate through the same angle. Thrust magnitude is determined by a collective pitch lever, very similar to a helicopter. There are four variable stability system (VSS) controllers: thrust, pitch, roll, and yaw, and three artificial feel servos for the evaluation pilot cockpit controls, each employing electrohydraulic servos. Longitudinal flying qualities for STOL landing approach, and lateral-directional flying qualities and control power requirements for STOL landing approach are discussed. Attention is given to the data acquisition and processing system.

Smith, R. E.↗
NASA NTRS1975

Space shuttle vehicle ferry configuration afterbody fairing effects on 140A/B orbiter aerodynamic characteristics using an .0405 scale model orbiter (43-0) in the Rockwell International 7.75 x 11 ft low speed wind tunnel (OA123)

The primary test objectives were to define ferry configuration afterbody fairing effects on orbiter stability and control characteristics and to substantiate wind tunnel results. Parametric variations consisted entirely of testing different afterbody fairing contours in an effort to improve both the orbiter drag levels and lateral-directional control characteristics. The three afterbody contours that were tested consisted of the Boeing TC3 beavertail, the new Rockwell-Boeing TC4 fairing, and a modification of an existing short bumblebee fairing redesignated TC6.

Mennell, R. C.↗
NASA NTRS1979

A compilation and analysis of helicopter handling qualities data. Volume 2: Data analysis

A compilation and an analysis of helicopter handling qualities data are presented. Multiloop manual control methods are used to analyze the descriptive data, stability derivatives, and transfer functions for a six degrees of freedom, quasi static model. A compensatory loop structure is applied to coupled longitudinal, lateral and directional equations in such a way that key handling qualities features are examined directly.

Heffley, R. K.↗
NASA NTRS1982

Open Cherry Picker simulation results

The Open Cherry Picker (OCP) is a manned platform, mounted at the end of the Remote Manipulator System (RMS), which is used to enhance extravehicular activities. The objective of the simulation program described was to reduce the existing complexity of those OCP design features that are mandatory for initial Space Shuttle applications. The OCP development test article consists of a torque box, a rotating foot restraint, a rotating stanchion that houses handholds, and a tool storage section with an interface with payload modules. If the size or complexity of the payload increases, payload handling devices may be added at a later data. The simulations have shown that the crew can control the RMS from the Aft Flight Deck of the Shuttle, using voice commands from the EVA crewman. No need for a stabilizer was evident, and RMS dynamics due to crew-induced workloads were found to be minor.

Nathan, C. A.↗
NASA NTRS1989

Analysis of flight data from a High-Incidence Research Model by system identification methods

Data partitioning and modified stepwise regression were applied to recorded flight data from a Royal Aerospace Establishment high incidence research model. An aerodynamic model structure and corresponding stability and control derivatives were determined for angles of attack between 18 and 30 deg. Several nonlinearities in angles of attack and sideslip as well as a unique roll-dominated set of lateral modes were found. All flight estimated values were compared to available wind tunnel measurements.

Batterson, James G.↗
NASA NTRS1983

Passive Magnetic Bearing

Magnetic bearing for limited rotation devices requires no feedback control system to sense and correct shaft position. Passive Magnetic Torsion Bearing requires no power supply and has no rubbing parts. Torsion wire restrains against axial instability. Magnetic flux geometry chosen to assure lateral stability with radial restoring force that maintains alignment.

Studer, P. A.↗
NASA NTRS1984

Study to eliminate ground resonance using active controls

The effectiveness of active control blade feathering in increasing rotor body damping and the possibility to eliminate ground resonance instabilities were investigated. An analytical model representing rotor flapping and lead-lag degrees of freedom and body pitch, roll, longitudinal and lateral motion is developed. Active control blade feathering is implemented as state variable feedback through a conventional swashplate. The influence of various feedback states, feedback gain, and weighting between the cyclic controls is studied through stability and response analyses. It is shown that blade cyclic inplane motion, roll rate and roll acceleration feedback can add considerable damping to the system and eliminate ground resonance instabilities, which the feedback phase is also a powerful parameter, if chosen properly, it maximizes augmentation of the inherent regressing lag mode damping. It is shown that rotor configuration parameters, like blade root hinge offset, flapping stiffness, and precone considerably influence the control effectiveness. It is found that active control is particularly powerful for hingeless and bearingless rotor systems.

Straub, F. K.↗
NASA NTRS1999

Further Development, Support and Enhancement of CONDUIT

From the first airplanes steered by handles, wheels, and pedals to today's advanced aircraft, there has been a century of revolutionary inventions, all of them contributing to flight quality. The stability and controllability of aircraft as they appear to a pilot are called flying or handling qualities. Many years after the first airplanes flew, flying qualities were identified and ranked from desirable to unsatisfactory. Later on engineers developed design methods to satisfy these practical criteria. CONDUIT, which stands for Control Designer's Unified Interface, is a modern software package that provides a methodology for optimization of flight control systems in order to improve the flying qualities. CONDUIT is dependent on an the optimization engine called CONSOL-OPTCAD (C-O). C-O performs multicriterion parametric optimization. C-O was successfully tested on a variety of control problems. The optimization-based computational system, C-O, requires a particular control system description as a MATLAB file and possesses the ability to modify the vector of design parameters in an attempt to satisfy performance objectives and constraints specified by the designer, in a C-type file. After the first optimization attempts on the UH-60A control system, an early interface system, named GIFCORCODE (Graphical Interface for CONSOL-OPTCAD for Rotorcraft Controller Design) was created.

Veronica, Moldoveanu↗
NASA NTRS2009

Adaptive Control of a Transport Aircraft Using Differential Thrust

The paper presents an adaptive control technique for a damaged large transport aircraft subject to unknown atmospheric disturbances such as wind gust or turbulence. It is assumed that the damage results in vertical tail loss with no rudder authority, which is replaced with a differential thrust input. The proposed technique uses the adaptive prediction based control design in conjunction with the time scale separation principle, based on the singular perturbation theory. The application of later is necessitated by the fact that the engine response to a throttle command is substantially slow that the angular rate dynamics of the aircraft. It is shown that this control technique guarantees the stability of the closed-loop system and the tracking of a given reference model. The simulation example shows the benefits of the approach.

Stepanyan, Vahram↗
NASA NTRS1989

Low-speed static and dynamic force tests of a generic supersonic cruise fighter configuration

Static and dynamic force tests of a generic fighter configuration designed for sustained supersonic flight were conducted in the Langley 30- by 60-foot tunnel. The baseline configuration had a 65 deg arrow wing, twin wing mounted vertical tails and a canard. Results showed that control was available up to C sub L,max (maximum lift coefficient) from aerodynamic controls about all axes but control in the pitch and yaw axes decreased rapidly in the post-stall angle-of-attack region. The baseline configuration showed stable lateral-directional characteristics at low angles of attack but directional stability occurred near alpha = 25 deg as the wing shielded the vertical tails. The configuration showed positive effective dihedral throughout the test angle-of-attack range. Forced oscillation tests indicated that the baseline configuration had stable damping characteristics about the lateral-directional axes.

Hahne, David E.↗
NASA NTRS1953

Wind-Tunnel Investigation at Low Speed of the Static Longitudinal and Lateral Stability Characteristics of a 1/9-Scale Powered Model of the Convair XFY-1 Vertically Rising Airplane

An experimental investigation has been made in the Langley stability tunnel at low speed to determine the static longitudinal and lateral stability characteristics of a l/9-scale powered model of the Convair XFY-1 vertically rising airplane. Effects of thrust coefficient were investigated for the complete model and for certain components of the model. Effects of control deflections and of propeller-blade angle were investigated briefly for the complete model. Most of the tests were made through an angle-of-attack range from about -4 deg. to 29 deg, and the thrust-coefficient range was from 0 t o 0.7. In order to expedite distribution of these data to interested persons, no analysis of the data has been prepared for this report,

Queijo, M. J.↗
NASA NTRS2007

Operational Experience with Autonomous Star Trackers on ESA Interplanetary Spacecraft

Mars Express (MEX), Rosetta and Venus Express (VEX) are ESA interplanetary spacecrafts (S/C) launched in June 2003, March 2004 and November 2005, respectively. Mars Express was injected into Mars orbit end of 2003 with routine operations starting in spring 2004. Rosetta is since launch on its way to rendezvous comet Churyumov-Gerasimenko in 2014. It has completed several test and commissioning activities and is performing several planetary swingbys (Earth in spring 2005, Mars in spring 2007, Earth in autumn 2007 and again two years later). Venus Express has also started routine operations since the completion of the Venus orbit insertion maneuver sequence beginning of May 2006. All three S/C are three axes stabilized with a similar attitude and orbit control system (AOCS). The attitude is estimated on board using star and rate sensors and controlled using four reaction wheels. A bipropellant reaction control system with 10N thrusters serves for wheel off loadings and attitude control in safe mode. Mars Express and Venus Express have an additional 400N engine for the planetary orbit insertion. Nominal Earth communication is accomplished through a high gain antenna. All three S/C are equipped with a redundant set of autonomous star trackers (STR) which are based on almost the same hardware. The STR software is especially adapted for the respective mission. This paper addresses several topics related to the experience gained with the STR operations on board the three S/C so far.

Lauer, Mathias↗
NASA NTRS1958

Low-Speed Static Stability Characteristics of Two Configurations Suitable for Lifting Reentry from Satellite Orbit

An investigation of the low-speed static stability and control characteristics of 1/4-scale models of two configurations suitable for lifting reentry from satellite orbit has been made in the Langley free- flight tunnel. One of the models was a thick, all-wing configuration having a delta plan form and the other was a flat delta wing with a half-cone fuselage. The investigation showed that, in general, the all-wing configuration had better longitudinal and lateral stability characteristics than the flat delta configuration.

Paulson, John W.↗
NASA NTRS1982

Methodology for determining elevon deflections to trim and maneuver the DAST vehicle with negative static margin

The relationships between elevon deflection and static margin using elements from static and dynamic stability and control and from classical control theory are emphasized. Expressions are derived and presented for calculating elevon deflections required to trim the vehicle in lg straight-and-level flight and to perform specified longitudinal and lateral maneuvers. Applications of this methodology are made at several flight conditions for the ARW-2 wing. On the basis of these applications, it appears possible to trim and maneuver the vehicle with the existing elevons at -15% static margin.

Perry, B., III↗
NASA NTRS1982

Flight dynamics of rotorcraft in steep high-g turns

An analyticl procedure developed to permit a systematic examination of rotorcraft flight dynamics in steep high-g turns is presented. The procedure is used in a numerical investigation of a tilt-rotor aircraft and three single-rotor helicopters that have different types of main rotor systems. The results indicate (1) that strong coupling in longitudinal and lateral-directional motions exists for these rotorcraft in high-g turns; (2) that for single-rotor helicopters, the direction of turn has a significant influence on flight dynamics; and (3) that a stability and control augmentation system that is designed on the basis of standard small-disturbance equations of motion from steady straight and level flight and that otherwise performs satisfactorily in operations near 1 g, becomes significantly degraded in steep turning flight.

Chen, R. T. N.↗
NASA NTRS1996

Aerodynamic Characteristics of Two Waverider-Derived Hypersonic Cruise Configurations

An evaluation was made on the effects of integrating the required aircraft components with hypersonic high-lift configurations known as waveriders to create hypersonic cruise vehicles. Previous studies suggest that waveriders offer advantages in aerodynamic performance and propulsion/airframe integration (PAI) characteristics over conventional non-waverider hypersonic shapes. A wind-tunnel model was developed that integrates vehicle components, including canopies, engine components, and control surfaces, with two pure waverider shapes, both conical-flow-derived waveriders for a design Mach number of 4.0. Experimental data and limited computational fluid dynamics (CFD) solutions were obtained over a Mach number range of 1.6 to 4.63. The experimental data show the component build-up effects and the aerodynamic characteristics of the fully integrated configurations, including control surface effectiveness. The aerodynamic performance of the fully integrated configurations is not comparable to that of the pure waverider shapes, but is comparable to previously tested hypersonic models. Both configurations exhibit good lateral-directional stability characteristics.

Cockrell, Charles E., Jr.↗
NASA NTRS1981

Flight test experience with high-alpha control system techniques on the F-14 airplane

Improved handling qualities of fighter aircraft at high angles of attack can be provided by various stability and control augmentation techniques. NASA and the U.S. Navy are conducting a joint flight demonstration of these techniques on an F-14 airplane. This paper reports on the flight test experience with a newly designed lateral-directional control system which suppresses such high angle of attack handling qualities problems as roll reversal, wing rock, and directional divergence while simultaneously improving departure/spin resistance. The technique of integrating a piloted simulation into the flight program was used extensively in this program. This technique had not been applied previously to high angle of attack testing and required the development of a valid model to simulate the test airplane at extremely high angles of attack.

Gera, J.↗