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V/stol aircraft handling criteria for hovering, low-speed and transition flight - control response and power - flight stability
Supersonic or hypersonic vehicle control system comprising elevons with hinge line sweep and free of adverse aerodynamic cross coupling
An existing deHavilland C-8A airplane has been modified into an augmentor wing flight test vehicle. Research objectives are to verify the augmentor flap concept and to produce data for STOL airworthiness criteria. The Modified C-8A provides the means for jet-STOL flight research down to a 60 knot approach speed. The airplane has a high thrust-to-weight ratio, high-lift flap system, vectored thrust, powerful flight controls, and lateral-directional stability augmentation system. Normal performance and handling qualities are expected to be satisfactory. Analysis and piloted simulator results indicate that stability and control characteristics in conventional flight are rated satisfactory. Handling qualities in the STOL regime are also generally satisfactory, although pilot workload is high about the longitudinal axis.
Innovation eliminates need for driver, sensor, and interconnecting logic circuits. Device combines simplicity of fixed-fin concept with precise rate control provided by active flight control system.
The use of the difference in chamber pressure between solid rocket booster engines as a controlling signal to the flight control system during booster thrust tailoff was examined. In addition, the control capability of the Generalized Attitude Control System (GACS) was compared to that of the baseline. Results indicate that the difference in chamber pressure signal provided essentially no improvement. However, the GACS is considerably better than the baseline in controlling during tailoff disturbances.
A telerobot concept consisting of dual-arm dexterous manipulators controlled by an operator has been proposed as a supplement (and possibly an alternative) to EVA by space crews. Issues of control of manipulator arms arising from the mechanical response and the operator's interaction with the hand controllers and displays are discussed. It is noted that the Space Shuttle cabin and the payload bay are the primary facilities for the resolution of remote manipulation and issues with telerobots.
The Space Station Reference Configuration is assembled in 19 assembly flights of several large structure elements of varied size and shape that contribute to its overall asymmetrical nature. The elements include thousands of square feet of solar arrays and thermal radiators, several hundred feet of truss structure, and several hundred thousand pounds of large-diameter cylindrical-shaped pressure modules housing scientific experiments and astronaut habitation areas. This paper quantitatively describes these physical characteristics of the fully assembled Space Station configuration. Several flight control design considerations are discussed relating to control system sizing, flight-path attitude orientation, payload pointing accommodation, and potential configuration modifications.
Many types of hypersonic aircraft configurations are currently being studied for feasibility of future development. Since the control of the hypersonic configurations throughout the speed range has a major impact on acceptable designs, it must be considered in the conceptual design stage. Here, an investigation of the aerodynamic control effectiveness of highly swept delta planforms operating in ground effect is presented. A vortex-lattice computer program incorporating a free wake is developed as a tool to calculate aerodynamic stability and control derivatives. Data generated using this program are compared to experimental data and to data from other vortex-lattice programs. Results show that an elevon deflection produces greater increments in C sub L and C sub M in ground effect than the same deflection produces out of ground effect and that the free wake is indeed necessary for good predictions near the ground.
A method for thermally analyzing convectively cooled flight experiments is presented. A three-dimensional fluid flow analysis code is used to optimize air circulation patterns and to predict air velocities in thermally critical areas. The analysis results are compared with the performance characteristics of a typical isothermal free jet, and good agreement is found between velocity profiles and radial distributions for downstream flow mixing. Predicted air velocities from the fluid analysis are used to calculate forced convection coefficients for the flight experiment, and the coefficients are used in a finite difference thermal analysis code to describe the response of air temperature and heat loss for the Lidar Atmospheric Sensing Experiment during transient flight profiles. Recommendations are made for the future design of convectively cooled flight experiments.
Described here is the development and implementation of on-line, near real time controller performance evaluation (CPE) methods capability. Briefly discussed are the structure of data flow, the signal processing methods used to process the data, and the software developed to generate the transfer functions. This methodology is generic in nature and can be used in any type of multi-input/multi-output (MIMO) digital controller application, including digital flight control systems, digitally controlled spacecraft structures, and actively controlled wind tunnel models. Results of applying the CPE methodology to evaluate (in near real time) MIMO digital flutter suppression systems being tested on the Rockwell Active Flexible Wing (AFW) wind tunnel model are presented to demonstrate the CPE capability.
The topics covered include the following: (1) telemetry processing independent of source; (2) generic system/software; (3) time homogeneity; (4) low latency networks; (5) distributed processing; (6) all data available to all workstations; and (7) recall of data in real time.
Monthly progress reports for September 1990 to January 1991 are given. Topics that are briefly covered include problem solving and learning taxonomies, knowledge acquisition techniques, software design, air traffic control, and space shuttle flight control.
The paper describes the application of techniques of exact I/O linearization of nonlinear control systems to the flight control of V/STOL aircraft. It is seen that the application of the theory to this example is not straightforward; in particular, the direct application of the theory yielded an undesirable controller. The situation was remedied by neglecting the coupling between the rolling moment input to the aircraft dynamics and the dynamics along the y-axis. An approximate I/O linearization procedure developed for slightly nonminimum phase nonlinear systems is shown to be effective for V/STOL aircraft.
Replacing the helicopter rotor swashplate and blade pitch control system with on-blade elevon control surfaces for primary flight control may significantly reduce weight and drag to improve mission performance. Simplified analyses are used to examine the basic aeroelastic characteristics of such rotor blades, including pitch and flap dynamic response, elevon reversal, and elevon control effectiveness. The profile power penalty associated with deflections of elevon control surfaces buried within the blade planform is also evaluated. Results suggest that with aeroelastic design for pitch frequencies in the neighborhood of 2/rev, reasonable elevon control effectiveness may be achieved and that, together with collective pitch indexing, the aerodynamic profile power penalty of on-blade control surface deflections may be minimized.
This paper presents an approach to interpretive modeling of LP based control allocation in intelligent flight control. The emphasis is placed on a nonlinear interpretation of the LP allocation process as a static map to support analytical study of the resulting closed loop system, albeit in approximate form. The approach makes use of a bi-layer neural network to capture the essential functioning of the LP allocation process. It is further shown via Lyapunov based analysis that under certain relatively mild conditions the resulting closed loop system is stable. Some preliminary conclusions from a study at Ames are stated and directions for further research are given at the conclusion of the paper.
This paper describes the methods used to estimate the statistical delta V and propellant requirements for propulsive maneuvers necessary to deliver the two Rovers while ensuring that planetary protection requirements are satisfied.
The MER Project will launch two spacecraft (MER-A and MER-B) to Mars in 2003 with the objective of delivering two rovers to different landing sites on Mars to study the surface composition and to look for evidence of present or past water.
Mission Operations and Command Assurance (MO&CA), a recent addition to flight operations teams at JPL. provides a system level function to instill quality in mission operations. MO&CA's primary goal at JPL is to help improve the operational reliability for projects during flight. MO&CA tasks include early detection and correction of process design and procedural deficiencies within projects. Early detection and correction are essential during development of operational procedures and training of operational teams. MO&CA's effort focuses directly on reducing the probability of radiating incorrect commands to a spacecraft. Over the last seven years at JPL, MO&CA has become a valuable asset to JPL flight projects. JPL flight projects have benefited significantly from MO&CA's efforts to contain risk and prevent rather than rework errors. MO&CA's ability to provide direct transfer of knowledge allows new projects to benefit directly from previous and ongoing experience. Since MO&CA, like Total Quality Management (TQM), focuses on continuous improvement of processes and elimination of rework, we recommend that this effort be continued on NASA flight projects.