This proposal is submitted by ANSER to the NSF for an advanced control system for a single stage-to-orbit launch vehicle application powered by a MHD energy-bypass engine. An advanced adaptive control system for an airbreathing MHD energy-bypass engine will be required to stabilize the interactions among the magnetic field, the boundary layer, and the conducting airflow in the MHD channels. The characteristics of a MHD energy-bypass engine are extremely nonlinear and vary widely with changing flight conditions and operating environments. The research for this application will focus on two classes of adaptive hierarchical control systems: (1) a back-propagated adaptive-critic design (ADC) model predictive control (MPC) system and (2) a back-propagated neural network model predictive-control system. Both of these control systems are potentially capable of controlling the kind of extreme non-linearity inherent in MHD energy-bypass engines. Processes within a MHD energy-bypass engine have a time constant in the nanosecond range. While previous aircraft and missile applications of adaptive-critic control systems provide some insight into the MHD energy-bypass engine application, the research team feels that those applications would be totally inadequate for the MHD energy-bypass engine control system. A new advanced control system is needed. Controllability of the MHD energy-bypass engine is a key issue and should be addressed during the engine design process.
The MHD energy-bypass propulsion system to be used in this research was defined by an ANSER-led research team during the NASA Highly Reusable Space Transportation (HRST) program 2 years ago. The MHD energy-bypass airbreathing engine extracts energy from the engine inlet flow by means of a MHD generator and adds the energy back into the flow by means of a MHD accelerator in the engine exhaust nozzle. Textron and Princeton MHD design and performance codes will be used to generate engine performance and sensitivity databases to develop and evaluate advanced control system alternatives. Princeton investigators, assisted by Dr. Eduardo Sontag from Rutgers, will define and model an advanced control system for a MHD energy-bypass propulsion system. ANSER will use the same design optimization code used in the NASA HRST study to determine the complete range of engine operating parameters and the impact of the control system on the overall performance of an MHD energy-bypass engine. Both single-stage-to-orbit (SSTO) and cruiser applications will be considered.
The products to be generated during the proposed investigation include (1) an advanced control system that can control and optimize the performance of an energy-bypass engine and (2) experiments to verify the limits of the control system's ability to control the energy-bypass processes. ***
