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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 775 records · Page 43

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NASA NTRS1995

Design challenges encountered in the F-15 PCA flight test program

The NASA Dryden Flight Research Center conducted flight tests of a propulsion-controlled aircraft system on an F-15 airplane. This system was designed to explore the feasibility of providing safe emergency landing capability using only the engines to provide flight control in the event of a catastrophic loss of conventional flight controls. Control laws were designed to control the flight path and bank angle using only commands to the throttles. While the program was highly successful, this paper concentrates on the challenges encountered using engine thrust as the only control effector. Compared to conventional flight control surfaces, the engines are slow, nonlinear, and have limited control effectiveness. This increases the vulnerability of the system to outside disturbances and changes in aerodynamic conditions. As a result, the PCA system had problems with gust rejection. Cross coupling of the longitudinal and lateral axis also occured, primarily as a result of control saturation. The normally negligible effects of inlet airframe interactions became significant with the engines as the control effector. Flight and simulation data are used to illustrate these difficulties.

Maine, Trindel A.↗

NASA NTRS1954

Measurement of the Static Stability and Control and the Damping Derivatives of a 0.13-Scale Model of the Convair XFY-1 Airplane, TED No. NACA DE 368

An investigation has been conducted to determine the static stability and control and damping in roll and yaw of a 0.13-scale model of the Convair XFY-1 airplane with propellers off from 0 deg to 90 deg angle of attack. The tests showed that a slightly unstable pitch-up tendency occurred simultaneously with a break in the normal-force curve in the angle-of-attack range from about 27 deg to 36 deg. The top vertical tail contributed positive values of static directional stability and effective dihedral up to an angle of attack of about 35 deg. The bottom tail contributed positive values of static directional stability but negative values of effective dihedral throughout the angle-of-attack range. Effectiveness of the control surfaces decreased to very low values at the high angles of attack, The model had positive damping in yaw and damping in roll about the body axes over the angle-of-attack range but the damping in yaw decreased to about zero at 90 deg angle of attack.

Johnson, Joseph L.↗

NASA NTRSDate not supplied

Assessment of Control Algorithms for Mars Entry Vehicles With Flap-Based Trajectory Control Under Uncertainty

Flap-based steering systems on blunt-body entry vehicles may improve flight performance relative to heritage bank-angle steering systems. Successful implementation of articulating aerodynamic flaps on a hypersonic entry vehicle requires an active control system to map angle of attack and sidelip angle commands to flap deflection commands. Here, a successive-linearization model prective control algorithm, as a linear quadratic regulator, are formulated, designed, and assessed to address this multiple input multiple output control problem. These two control algorithms are assessed under uncertainty in Monte Carlo simulations for various control profiles and vehicle configurations. Results indicate that while both control algorithms provide successful command tracking under uncertainty, the model predictive controller provides a lower mean and integral error, as well as greater robustness, relative to the linear-quadratic regulator.

Daniel L Engel↗

NASA NTRS1978

The effect of normal atmospheric variability on Space Shuttle Orbiter entry performance

The Space Shuttle Orbiter is controlled during entry by a combination of aerodynamic surfaces composed of elevons, a body flap, and a rudder that flares as a speedbrake, and a reaction control system that uses 16 small rocket thrusters. To determine the effects of realistic atmospheric density variations on reentry, a series of Monte Carlo trajectories were generated for each season. The performance parameters analyzed include maximum hinge moments experienced by the aerodynamic control surfaces, the maximum deflections experienced by the aerodynamic control surfaces, a range of angle-of-sideslip values, maximum dynamic pressure, maximum stagnation point heat rate, and state conditions at touchdown. The results of the investigation indicate that the Orbiter guidance and control systems could tolerate atmospheric variability without failures in the control system hardware.

Powell, R. W.↗

NASA NTRS1993

A fixed H-infinity controller for a supermaneuverable fighter performing the Herbst maneuver

This paper presents an H-infinity flight control system design case study for a supermaneuverable fighter flying the Herbst maneuver. The Herbst maneuver presents an especially challenging flight control problem because of its large ranges of airspeed, angle of attack and angular rates. A fixed H-infinity controller has been developed via the mixed-sensitivity problem formulation for 20 linearized models representing the maneuver. Both linear and nonlinear full model evaluations indicate that this single H-infinity controller together with a fixed LQR inner loop feedback have achieved 'robust stability' and 'robust performance' for the entire maneuver without gain scheduling.

Chiang, R. Y.↗

NASA NTRSDate not supplied

Pterodactyl: Guidance and Control of a Symmetric Deployable Entry Vehicle using an Aerodynamic Control System

The NASA-funded Pterodactyl project seeks to advance the current state-of-the-art for entry vehicles by developing novel guidance and control technologies for Deployable Entry Vehicles (DEVs). This paper presents the guidance and control design and analysis for a mechanically-deployed DEV with a symmetric aeroshell and aerodynamic control surfaces. We present guidance tuning using both bank angle modulation with the Fully-Numerical Predictor Corrector Entry Guidance technique (FNPEG) and angle of attack and sideslip modulation with FNPEG with uncoupled range control (FNPEG URC). We show the control system design and simulation results for tracking both types of guidance commands.

Benjamin W L Margolis↗

NASA NTRS2021

Pterodactyl: Guidance and Control of a Symmetric Deployable Entry Vehicle using an Aerodynamic Control System

Benjamin Margolis↗

NASA NTRS1974

Results of investigations on an 0.015 scale 140A/B configuration space shuttle vehicle orbiter model (49-0) in the LTV 4 by 4-foot high speed wind tunnel (0A84)

Data obtained from a wind tunnel test of an 0.015-scale 140 A/B configuration space shuttle vehicle orbiter model (49-0) are presented. Runs were conducted at Mach numbers 0.6, 0.9, 1.2, 1.6, and 2.0 and Reynolds numbers of 8.4, 9.0, 9.0, 10.9, and 13.6 million per foot respectively. Various control surface settings were investigated from angles of attack of minus 4 degrees to plus 30 degrees at fixed angles of sideslip of zero and minus 5 degrees and through angles of sideslip from minus 2 to plus 8 degrees at fixed angles of attack of zero, plus 10, plus 15, and plus 20 degrees. The purpose of the test was to define the longitudinal and lateral-directional stability and control characteristics for the updated SSV configuration.

Esparza, V.↗

NASA NTRS1971

Full-scale wind-tunnel tests of a small unpowered jet aircraft with a T-tail

The aerodynamic characteristics of a full scale executive type jet transport aircraft with a T-tail were investigated in a 40 x 80 ft (12.2 by 24.4 meter) wind tunnel (subsonic). Static, longitudinal, and lateral stability, and control characteristics were determined at angles of attack from -2 deg to +42 deg. The aircraft wing had 13 deg of sweep and an aspect ratio of 5.02. The aircraft was tested power off with various wing leading- and trailing-edge high lift devices. The basic configuration was tested with and without such components as engine nacelles, wing tip tanks, and empannage. Hinge-moment data were obtained and downwash angles in the horizontal-tail plane location were calculated. The data were obtained at Reynolds numbers of 4.1 million and 8.7 million based on mean aerodynamic chord. The model had static longitudinal stability through initial stall. Severe tail buffet occurred near the angle of attack for maximum lift. Above initial stall the aircraft had pronounced pitch-up, characteristic of T-tail configurations. A stable trim point was possible at angles of attack between 30 deg and 40 deg (depending on c.g. location and flap setting). Hinge-moment data showed no regions with adverse effects on stick force. Comparisons of wind-tunnel data and flight-test are presented.

Soderman, P. T.↗

NASA NTRS1976

Laser-electron beam interaction applied to optical amplifiers and oscillators

Momentum modulation of a relativistic electron beam by a Nd:YAG laser is demonstrated. The electrons, at 100 MeV energy, interact with the laser light in helium gas at standard temperature and pressure. At an angle of 6.55 mrad between the two wavevectors, corresponding to the Cerenkov angle, a given electron remains in a field of constant phase as it passes through the light beam. The experimental arrangement is illustrated showing the trajectories of the electron and light. The particle momentum is measured by a mass spectrometer, and the angle between the wavevectors is controlled by a rotatable mirror. Experimental results indicate that momentum modulation of an electron beam may be used for amplification. A possible configuration for an optical klystron is illustrated.

Pantell, R. H.↗

NASA NTRS1976

Radar Performance Improvement

The AN/APQ-153 fire control radar modified to provide angle tracking was evaluated for improved performance. The frequency agile modifications are discussed along with the range-rate improvement modifications, and the radar to computer interface. A parametric design and comparison of noncoherent and coherent radar systems are presented. It is shown that the shuttle rendezvous range and range-rate requirements can be made by a Ku-Band noncoherent pulse radar.

Little, G. R.↗

NASA NTRS1977

Optimization of the space shuttle entry guidance lateral deadband, minimum bank angle logic

The lateral deadband and minimum bank angle schedule were studied. Results used by the analytic drag control entry guidance system are presented. Lateral deadband limits and configuration were investigated and possible changes in the minimum bank angle schedule to improve crossrange control and drag acceleration control for entry were examined. The study recommends a 12.5 deg lateral deadband to accommodate low dispersions of up to 23%.

Bump, P. B.↗

NASA NTRS1981

Control of Saturn's kilometric radiation by Dione

Voyager 1 observations of Saturn's kilometric radio emissions reveal a strong but apparently transitory control by the orbital phase angle of Dione. This may be a geometrical effect and a time-variable plasma torus associated with Dione could explain most of the observed details of the Dione modulation by creating a shadow zone near the equatorial plane.

Kurth, W. S.↗

NASA NTRS1982

Microprocessor control system for 200-kilowatt Mod-OA wind turbines

The microprocessor system and program used to control the operation of the 200-kW Mod-OA wind turbines is described. The system is programmed to begin startup and shutdown sequences automatically and to control yaw motion. Rotor speed and power output are controlled with integral and proportional control of the blade pitch angle. Included in the report are a description of the hardware and a discussion of the software programming technique. A listing of the PL/M software program is given.

Nyland, T. W.↗

NASA NTRS1983

Stability and control of a supersonic transport airplane during landing approach

Modal control theory was applied to determine feedback gains that provide desirable stability characteristics and satisfactory transient response to aileron deflection input. However, the peak value of lateral acceleration at the pilot's station does not satisfy a proposed criterion during a rolling maneuver. Optimal regulator theory does not provide a significant reduction of the peak lateral acceleration. The weighting matrices in the performance index were given an extreme variation, but the effect on lateral acceleration remained insignificant. Open loop control provided the desired bank angle (30 deg) with the desired roll rate (10 deg/sec), and provided a satisfactory level of lateral acceleration. However, a large adverse sideslip angle was required. In addition, the yawing velocity was negative for about two seconds and lateral acceleration changed sign during the maneuver. The problem persists and perhaps relaxed criteria must be proposed. The criteria could allow any combination of a lower average rolling velocity, a larger adverse sideslip angle excursion, and a higher peak lateral acceleration at the pilot's station.

Oehman, W. I.↗

NASA NTRS1983

Space Station Control Requirements and Flywheel System Weights for Combined Momentum and Energy Storage

The specifications of the flywheel system for momentum storage and vehicle torquing are somewhat dependent upon the attitude control requirements of the space station in orbit. As a ground rule, the flywheel system will be sized large enough to provide all attitude maneuvers, if practical, to avoid or minimize turning on the reaction control system (RCS). The RCS, whenever used, expels expensive mass and tends to contaminate optical surfaces of the vehicle. The vehicle rate and acceleration specifications of 0.10 deg/sec and 0.01 deg/square sec are tentative, and may be reduced if lesser values are more practical for flywheel design. For local vertical attitude hold, the average attitude error should be zero, and not the classical 1 degree, since control moment gyro (CMG) gimbal angles provide an exact reference feedback for gravity gradient momentum. Docking presents a problem for docking transients and attitude alignment which will require use of the RCS.

Elam, F. M.↗

NASA NTRS1984

Optimal slewing maneuvers for flexible spacecraft using a closed form solution for the linear tracking problem

The problem of maneuvering a flexible spacecraft through a large angle while requiring the feedback control system to track a desired output state is considered. The desired output state is assumed to be provided by the corresponding open-loop maneuvering solution for the linear system model. Closed form solutions are provided for the Riccati and prefilter equations defining the optimal control. Example maneuvers are presented where control-rate penalties have been included in the performance index, in order to smooth both the open- and closed-loop control commands.

Turner, J. D.↗

NASA NTRS1985

The Satellite Sail

It is proposed to suspend an airfoil from the Space Shuttle by a long tether into the upper atmosphere to provide a horizontal force on the Shuttle, thereby changing its orbital plane most efficiently. The airfoil would need high-temperature skin and tether, and remotely controlled flaps to adjust its angle of attack. The airfoil could also be used as a hypersonic facility to measure aerodynamic characteristics at extreme altitudes and velocities. This use would require a vertical lift force to counteract the drag force and prevent the Shuttle orbit from decaying too rapidly during the aerodynamic measurements.

Pearson, J.↗