Design of Launch Vehicle Flight Control Augmentors and Resulting Flight Stability and Control (Center Director's Discretionary Fund Project 93-05, Part III)

This report is Part III, the final part, of the Center Director's Discretionary Fund (CDDF) Project 93-05, in which the author as Principal Investigator has proposed and designed forward and aft, all-movable, blunt trailing-edge (TE), flight control augmentors (FCA's) to provide the required control augmentation for a family of aft center-of-gravity (cg) launch vehicles that could not be adequately controlled using engine gimbaling alone. This comprehensive flight mechanics research effort has been partially documented in previous publications. NASA TP-3635 (Barret, C.; February 1995) has presented the state-of-the-art assessment of smart materials and advanced composites directly applicable to the innovative design of the FCA's. NASA TP-3615 (Barret, C.; April 1996) has presented the developmental stages of the program, the comprehensive reviews of our national heritage of launch vehicles that have used aerodynamic surfaces, and the current use of these by other nations. This publication presents the control requirements, the details of the designed FCA's, the static stability and dynamic stability wind tunnel test programs, the static stability and control analyses, the dynamic stability characteristics of the experimental LV with the designed FCA's, and a consideration of the elastic vehicle. Dramatic improvements in flight stability have been realized with all the FCA designs; these ranged from 41 percent to 72 percent achieved by the blunt TE design. The control analysis showed that control increased 110 percent with only 3 degrees of FCA deflection. The dynamic stability results showed improvements with all FCA designs tested at all Mach numbers tested. The blunt TE FCA's had the best overall dynamic stability results. Since the lowest elastic vehicle frequency must be well separated from that of the control system, the significant frequencies and modes of vibration have been identified, and the response spectra compared for the experimental LV in both the conventional and the aft cg configuration. Although the dynamic response was 150 percent greater in the aft cg configuration, the lowest bending mode frequency decreased by only 2.8 percent.